Session PB. There are 56 abstracts in this session.



Session: SOLIDS, poster number: 123

Solid-State NMR Investigation of the Effects of Gamma Irradiation on a Clarifying Agent for Polypropylene Food Packaging


Clark D. Ridge1; Sarah Donnelly1; Mary Dawn Celiz1; Fu Chen2
1FDA, College Park, MD; 2Department of Chemistry, Univerity of Maryland, College Park, MD

LCMS and SSNMR methods were used to analyze the effects of gamma irradiation on a clarifying agent used in polypropylene packaging. Powdered resin samples containing the agent were subjected to doses of gamma radiation ranging from 1-20kGy. The LCMS experiments showed no significant change to the additive but were not able to report on the whole additive in the plastic. The solvation and ionization processes separated the aluminum from the agent. This made it difficult to determine if the irradiation separated the compound prior to analysis. SSNMR experiments were performed on the samples to report on the structure of the additive in the resin. Results of the NMR analysis will be presented with discussion of future applicability of SSNMR in the study of food packaging.


Session: SOLIDS, poster number: 124

Electron Saturation Recovery with Magic Angle Spinning and Rapid Signal Acquisition


Nicholas Alaniva
WUSTL, St. Louis, MO

Dynamic nuclear polarization (DNP) increases NMR sensitivity by transferring polarization from electron to nuclear spins. Polarizing for 10 ms emphasizes the enhanced signal of nuclear spins in direct contact with the electron spins. At 4.3 K, the longitudinal relaxation of the polarizing electron spins is long enough that the degree of relaxation can be encoded in this direct DNP-enhanced signal. We report the first measurement of electron longitudinal relaxation with magic-angle spinning (MAS) NMR, using DNP-enhanced NMR. The relaxation constant, T1e, is measured at 40 ± 6 ms for 40 mM trityl spinning at 4.0 kHz and 4.3 K in a 7 T magnetic field. Cryogenic spinning at 4.3 K is achieved with a custom MAS-DNP spectrometer.


Session: SOLIDS, poster number: 125

Selective Detection of Active Pharmaceutical Ingredients in Tablet Formulations Using Solid-State NMR Spectroscopy


You-lee Hong1, 2; G. N. Manjunatha Reddy3; Yusuke Nishiyama1, 4
1RIKEN-JEOL Collaboration Center, RIKEN, Kanagawa, Japan; 2WPI-iCeMS, ChEM-OIL, Kyoto University, Kyoto, Japan; 3Department of Physics, University of Warwick, Coventry, United Kingdom; 4JEOL RESONANCE Inc., Tokyo, Japan

We propose a fast MAS NMR experiment for the selective detection of 1H signals associated with an API from a severely overlapped NMR spectrum of a tablet formulation. Spectral simplification is achieved by combining (i) S-RESPDOR with the phase-modulate (PM) saturation pulses, (ii) RFDR, and (iii) double-quantum excitation pulse sequence. First, 1H sites in close proximities to 14N nuclei of an API are excited using a PM-S-RESPDOR sequence, and simultaneously, the other unwanted 1H signals of excipients are suppressed. Then, RFDR sequence drives 1H magnetization transfer to adjacent 1H sites in the crystalline API regions. Finally, a PM-S-RESPDOR-RFDR sequence is combined with a BaBa sequence to elucidate local-structures and 1H-1H proximities of the API in a dosage form.


Session: SOLIDS, poster number: 126

A Search for Small Molecule Inhibitors of S100 β


Moneerah Alqahtani1, 3; Amar G. Chittiboyina2; Ikhlas A. Khan2
1Department of BioMolecular Sciences, University, MS; 2National Center for Natural Products Research, University, MS; 3Department of Pharmacognosy, King Saud University, Riyadh, KSA

Our research warrants the field to consider out of the box thinking for therapeutic approaches and urges the recognition of the multifactorial nature of Alzheimer’s disease (AD) and the paradigm shift of drug development from a single targeted to multi-targeted ligand approaches. The primary goal of this project is to develop inhibitors of S100β with neuroprotective as well as antioxidative properties for the treatment of AD. By combining the structural features of both lipoic and arundic acids, a multifunctional and bivalent ligands were designed. Such ligands are anticipated to synergize the antioxidative and neuroprotective traits of novel inhibitors of S100β for the treatment of neurodegenerative disorders such as AD. Research efforts as well as synthetic details will be presented.


Session: SOLIDS, poster number: 127

Novel methods for homonuclear decoupling in 1H NMR of solids


Pinelopi Moutzouri; Federico Maria Paruzzo; Bruno Simões de Almeida; Lyndon Emsley
EPFL, Lausanne, Switzerland

The typical linewidths of 1H NMR spectra of powdered organic solids at the fastest magic angle spinning (MAS) rates are of the order of a few hundred Hertz. While this is remarkable in comparison to the tens of kHz obtained from spectra of static samples, it is still the bottleneck for the general use of 1H solid-state NMR. Here, we demonstrate a novel strategy to further improve spectral resolution. We show that the anti-z-COSY experiment, originally used for 1H homonuclear J decoupling in solution-state NMR, can also reduce the residual line broadening of 1H spectra of solids leading to an improvement in resolution of up to a factor of two compared to conventional spectra at the same rate.


Session: SOLIDS, poster number: 128

Directly Probing Secondary Bonding Interactions in Organometallic Complexes By Solution and Solid-State NMR


Amrit Venkatesh1, 2; Kasuni C. Boteju1, 2; Damien B. Culver3; Matthew P. Conley3; Aaron D. Sadow1, 2; Aaron J. Rossini1, 2
1Iowa State University, Department of Chemistry, Ames, IA; 2US DOE Ames Laboratory, Ames, IA; 3Department of Chemistry, University of California, Riverside, CA

Secondary interactions between the metal and hydrogen atoms in the coordinating ligands frequently stabilize organometallic complexes, and play an important role in metal catalyzed polymerization and C-H activation processes. These interactions are typically indirectly studied using X-ray crystallography, IR spectroscopy, and 1H, 13C, and 29Si solution NMR spectroscopies. Here we directly probe M↼H-X interactions where X=Si or C and M=Y, Yb, Sc, using solution and solid-state NMR. A series of yttrium complexes are characterized in solution by measuring 1H-89Y and 1H-29Si J-couplings. Secondary interactions in fluxional ytterbium and scandium compounds are characterized by low temperature solid-state NMR dipolar HETCOR and J-resolved experiments. The measured M-H J-couplings agree well with DFT, providing a powerful approach to characterize the strength of secondary interactions.


Session: SOLIDS, poster number: 129

Solid-State NMR Structure of Human Cofilin-2 Assembled on Actin Filaments Reveals Isoform-Specific Conformational Changes and Binding Mode


Jodi Kraus1; Jenna Yehl1; Elena Kudryashova2; Ryan Russell1; Dmitri Kudryashov2; Tatyana Polenova1
1University of Delaware, Newark, DE; 2The Ohio State University, Columbus , OH

The cofilin family of proteins plays an integral role in regulating actin polymerization dynamics. These proteins regulate actin filament severing in a nucleotide-dependent manner during actin treadmilling. We present the atomic resolution structure and intermolecular interface of human cofilin-2 (cofilin) assembled on filamentous (ADP-F)-actin. We completed 96% of resonance assignments in cofilin using a set of 2D and 3D homo- and heteronuclear data sets. From spectra acquired on 2-13C-glucose,15N and 1,6-13C-glucose,15N-labeled cofilin, we assigned 1,612 distance restraints for structure determination. Our structure reveals new hydrogen bonding interactions and a unique conformation for cofilin. Using dREDOR methods, we determined the cofilin-actin interface and identified two patches on cofilin for actin binding. Our results provide a structural basis for isoform-dependent actin severing.


Session: SOLIDS, poster number: 130

Functional interactions between a Kir Channel and the lipid bilayer


Benjamin Wylie; Collin Borcik; Reza Amani; Nazmul Khan; Derek Versteeg; Maryam Yekefallah; Evan val Aalst
Texas Tech University, Lubbock, TX

KirBac1.1 is a tetrameric inward-rectifier K+ (Kir) channel.  Its structure includes a selectivity filter which allows K+ ions  to pass through the bilayer,  eight transmembrane helices, and a cytoplasmic “Kir domain”.  The Kir domain tethers to anionic lipids, gating the channel. Using solid-state NMR, we identified the activating anionic lipid binding pocket within KirBac1.1 and determined the changes in dynamic structure associated with channel gating.  We discovered two states of the channel under gating conditions.  One state is activated and conductive and the second state appears to be shallowly inactivated. Further, using 13C-labeled biological lipids, we show that KirBac1.1 lowers the gel-liquid crystalline phase transition of the surrounding bilayer and increases the liquid-ordered (Lo)/liquid-disordered (Ld) phase separation of these membranes.


Session: SOLIDS, poster number: 131

Tailoring Solid-state NMR to Elucidate Molecular Structure of Amorphous Biological Complexes


John E Kelly1; Christine Chrissian1, 2; Keyvan Dastmalchi1; Ruth E Stark1
1City College of New York, New York, NY; 2Ph.D. Programs in Biochemistry and Chemistry, CUNY, New York, NY

We describe strategies to adapt several solid-state NMR methods to elucidate the molecular structures and compositions of amorphous biosolids These materials typically contain a mix of rigid and mobile domains, resulting in over/under-sampling of the spin signals and spectral complexity. We have addressed these issues using multidimensional experiments with direct and cross polarization-based methods in two biocomposite materials, fungal melanin and potato tuber suberin. For example, DP-INADEQUATE has uncovered and enabled us to determine the lipid composition of C. neoformans in whole cells. Using 3D DARR-DARR we have begun to separate the crowded polysaccharide region of the suberin spectra. These advances lay the groundwork for structural determination that will improve our functional understanding of these complex solid biocomposites.


Session: SOLIDS, poster number: 132

Multidimensional Solid-State NMR Studies of Plant Cell Wall Structure and Dynamics


Pyae Phyo1; Henry Temple2; Barbara Perrone3; Paul Dupree2; Mei Hong1
1MIT, Cambridge, MA; 2University of Cambridge, Cambridge, United Kingdom; 3Bruker BioSpin AG, Fällanden, Switzerland

Plant cell walls possess a complex polysaccharide network that provides both strength and flexibility to plant cells. In this study, we applied 2D 13C and 1H solid-state NMR experiments to investigate the structure and dynamics of genetically modified intact Arabidopsis leaves, in order to understand the effects of methyl esterification and calcium ions on cell wall structure. An MAS cryoprobe allowed us to observe long-range intermolecular cross peaks with 3-fold higher sensitivity. Our results give molecular evidence of how cellulose-pectin interactions and the Ca2+ crosslinked pectin network change to regulate cell wall loosening and plant growth.


Session: SOLIDS, poster number: 133

Structural Studies of GSS-Associated Y145Stop Prion Protein Amyloids by Solid-State NMR Spectroscopy


Hanh Dao1; May Z. Hlaing1; Yixuan Ma1; Krystyna Surewicz2; Witold K. Surewicz2; Christopher P. Jaroniec1
1The Ohio State University, Columbus, OH; 2Case Western Reserve University, Cleveland, OH

Transmissible spongiform encephalopathies (TSEs), commonly known as prion diseases, are neurodegenerative diseases in humans and some animals. The most well-studied prion diseases in human to date is Creutzfeldt-Jakob disease (CJD), but there are also other inherited forms of human prion diseases, including Fatal Familial Insomnia (FFI) and Gerstmann–Sträussler–Scheinker disease (GSS). GSS is associated with substitution mutations such as P102L, P105L, A117V, and G131V, in the prion protein gene. Additionally, the M129V polymorphism is suspected to play a crucial role in the susceptibility to CJD and GSS, yet its impact remains unclear. Here, we investigate the kinetics and structural impact of P102L, P105L, A117V mutations, on their own and in combination with M129V mutation.


Session: SOLIDS, poster number: 134

The application of 1H detection methods at fast MAS regime for the studies of biological systems


Alons Lends; Axelle Grelard; Estelle Morvan; Mathilde Bertoni; Antoine Loquet
Institut Européen de Chimie et Biologie, Pessac, France

The recent development in MAS NMR probe technology enabled the access to the highly resolved 1H detected spectra. Particularly the faster MAS frequencies increased the resolution and sensitivity in the 1H dimension. Higher MAS frequencies require the use of rotors with significantly smaller diameters. Hence, the samples could be reduced till even sub-milligram quantities. The 1H detection methods at fast MAS successfully have been already applied for many types of biological systems. It opened up the new avenues for structural description at atomic level of systems previously unreachable with other methods. Here we are going to present the 1H detection experiments to structurally characterize the alpha-synuclein fibrils and the Cryptococcus neoformans pathogen.


Session: SOLIDS, poster number: 135

A Site-specific Comparison of the Pentameric and Hexameric Assembly of the Rous Sarcoma Virus Capsid Protein


Bo Chen1; Xin Qiao1; Tyrone Thames1; Kaylie Janicki1; Ryan Weed1; Jaekyun Jeon1; Ivan Hung2; Peter Gorkov2; zhehong Gan2
1University of Central Florida, Orlando, FL; 2NHMFL, Tallahassee, FL

In the maturation process, the immature spherical retroviral capsids reorganize into polymorphic mature capsids to encapsulate the viral genome. The retroviral capsid is a promising antiviral drug target, as its shape and stability is vital to the viral infectivity. The polymorphism of mature retroviral capsids is caused by insertion of twelve pentameric capsid proteins (CAs) into the hexameric lattice. However, due to the strong polymorphism, structural information of retroviral capsids is limited at the molecular level, especially the pentameric assembly that underpins the shape and size of the mature capsid. Here we report our solid state NMR (ssNMR) studies of the assembly of the 237-residue Rous sarcoma virus (RSV) CA, a widely used retroviral template. Torsion angles and dynamics are derived from chemical shift assignments of 220 residues in the RSV CA spherical assembly, formed entirely by CA pentamers. By comparing with our prior work1 of the same protein in its tubular assembly comprising exclusively CA hexamers, we reveal, for the first time, site-specific structural differences that dictate the assembly morphology in its native state (Figure 1). This information lays the foundation for further study of the mechanism of capsid assembly at the molecular level and may assist rational design of anti-viral drugs against deadly diseases caused by retroviruses.


Session: SOLIDS, poster number: 136

Atomic-Resolution Structure of Assembled HIV-1 Capsid Tubes by Magic Angle Spinning NMR


Manman Lu1, 3; Ryan Russell1, 2; Alex Bryer1; Caitlin Quinn1; Juan Perilla1, 2; Charles Schwieters4; Angela Gronenborn2, 3; Tatyana Polenova1, 2
1University of Delaware, Newark, DE; 2Pittsburgh Center for HIV Protein Interactions, Pittsburgh, PA; 3University of Pittsburgh, Pittsburgh, PA; 4National Institutes of Health, Bethesda, MD

HIV-1 capsid plays multiple key roles in the viral replication and its inherent plasticity has hampered efforts to determine its structure. Here, we report the atomic-resolution structure of assembled capsid tubes determined by magic angle spinning NMR spectroscopy, integrated with low-resolution cryo-EM data. The structure of a single polypeptide chain was calculated using C-C distance restraints, 13C and 15N chemical shifts, and torsion angle information. This chain was fit into a low-resolution (8 Å) cryo-EM density map of a CA hexamer unit, extracted from the density of a (-12,11) helical tube. The CA structure in tubular assemblies exhibits notable differences from the flat hexameric X-ray structure in crystals of CA, which underscore the remarkable structural plasticity of the capsid.

 


Session: SOLIDS, poster number: 137

Assignment of 2x72 kDa Tryptophan Synthase by proton-detected 5D Solid-State NMR Experiments


Alexander Klein1; Petra Rovó2; Varun Sakhrani3; Patricia Skowronek2; Laura Kukuk1; Suresh Vasa1; Leonard Mueller3; Rasmus Linser1
1Technical University Dortmund, Dortmund, Germany; 2Ludwig-Maximilians-University, Munich, Germany; 3University of California Riverside, Riverside, CA
Proteins with >~40 kDa molecular weight have practically posed insurmountable hurdles for both solution and solid-state NMR. Here we show that tryptophan synthase, 72 kDa in the asymmetric unit (143 kDa in its physiological form), can be assigned for the first time when a combination of higher-dimensionality experiments in the solid state, in particular a combination of 5D HNcaCONH and 5D HNcoCANH with 4D sidechain-to-backbone experiments enabling sidechain assignments and amino acid type determination, are used.
Opposed to solution NMR, dipolar magnetization transfer efficiency is irrespective of molecular weight, rendering complex pulse schemes and higher dimensionality a perfect setting for solid-state NMR. The implementation of the demonstrated pulse schemes will enable a significant expansion of amenable NMR target proteins.

Session: SOLIDS, poster number: 138

Modulation of the Structure and Self-assembly of S100A12 by Cooperating with Ca(II) and Zn(II)


Qian Wang
College of Staten Island, Staten Island, New York

Calgranulin C (or S100A12) accounts for 5% of the proteins in neutrophils and binds zinc to sequester this metal to prevent pathogenic growth and proliferation. Crystal structures of biologically relevant Zn(II), Ca(II) bound form of S100A12 has not been characterized. The dimeric apo-protein self-assembles into higher-order oligomers in the presence of Zn(II) and Ca(II), prohibiting its structural characterization by solution NMR methodologies. We present magic angle spinning (MAS) NMR studies of apo-, Zn(II)-, Ca(II)- and Zn(II),Ca(II)-S100A12 aimed at investigating structural perturbations induced upon metal binding and oligomerization. Based on our results, conformational changes occur in helix II and the functionally relevant hinge region. These zinc-binding induced perturbations might be critical for the interaction of S100A12 with its target proteins.


Session: SOLIDS, poster number: 139

Examining Interactions at Lipid Membrane Interfaces with Solid-state NMR


Ashley D. Bernstein1; Zilma P. Muneeswaran1; Aijaz Ahmad Dar2; Laurence S. Romsted1; Andrew J. Nieuwkoop1
1Rutgers University, Piscataway, NJ; 2University of Kashmir, Hazratbal, Srinagar, J&K India

At the membrane interface, concentrations of ions aren’t what they seem. Different from the bulk by orders of magnitude, ion concentrations are much higher, and ion pairing can occur. All of this can greatly affect membrane mobility and protein binding. We use ssNMR to investigate effects of various species on liposomes, such as divalent cations or phospholipids with charged headgroups. Chemical Trapping (CT) is a technique that reports on concentrations of moieties in the interfacial region. We confirmed CT results of a membrane-binding peptide’s orientation on PC liposomes. We then 15N labeled an inactive version of the CT probe in order to examine the position of the probe with regard to the lipid bilayers, as well as to the peptide.


Session: SOLIDS, poster number: 140

Pseudocontact Shifts Measurements in a Natively Diamagnetic Protein Using Proton Detected  Solid State NMR Spectroscopy Facilitated by Co2+Binding Tag


Justin K Thomas; Rajith J Arachchige; Dwaipayan Mukhopadhyay; Christopher P. Jaroniec
The Ohio State University, Columbus,

Paramagnetic solid state NMR experiments provides distance depended pseudocontact shift (PCSs) and paramagnetic relaxation enhancements (PREs) restraints, such site specific measurement of PCSs and PREs restraints are used for structural studies of proteins and other biological molecules. Here we demonstrate PCS measurements in natively diamagnetic proteins are facilitated by a thiol-reactive, compact cyclen-based, high affinity Co2+binding tag, 2,2'-(4,10-bis(2-(pyridin-2-yldisulfanyl)ethyl)-1,4,7,10-tetraazacyclododecane-1,7-diyl)diacetic acid (TETACD), which can be rigidly attached to protein via two disulfide bridges. Specifically, using K38C-Q32C-TETACD and D40C-E42C-TETACD mutants of B1 immunoglobulin-binding domain of protein G as a model, we observed about 200 PCS restraints for nuclei up to ~20 Åfrom the metal and displays good agreement with calculated PCS values.

 


Session: SOLIDS, poster number: 141

pH-Dependent Thermodynamic Intermediates of PHLIP Studies by Solid-State NMR Spectroscopy (ssNMR)


Sarah Otieno
SUNY at Binghamton, Binghamton, NY

The pH low insertion peptide (pHLIP) inserts into membrane under mild acidity, forming a transmembrane α-helix. For applications, pHLIP detects local acidosis in vivo (particularly for cancer imaging) and translocate membrane-impermeable cargo across membrane, feature with implications in research and medicine. Although the initial and end states of pHLIP insertion (at pH ≥ 7 and ≤5.3, respectively) are well known, how pHLIP interacts with membrane at the intervening pH values, which are relevant to tumor acidity in vivo, is not clear. Here, using advanced solid-state NMR spectroscopy with palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine vesicles model membrane, we show the existence of distinct intermediate states at the intervening pH values. Such understanding may improve pHLIP technology in the future. We also report, pHLIp membrane insertion mechanism using a biologically relevant target membrane composition.


Session: SOLIDS, poster number: 142

H3 and H4 Histone Tails Flexibility Studied by MAS NMR


Nicole Gonzalez Salguero; Mohamad Zandian; Matthew Shannon; Rudra Purusottam; Michael Poirier; Christopher Jaroniec
The Ohio State University, Columbus, United States

Histone tails mediate different biological processes, such as transcription, chromatin organization, and protein recruitment. Due to their disordered nature, they have remained elusive to traditional structural biology techniques. In order to provide insight into their different functions, we have used a combination of solution NMR and High-Resolution Magic-Angle spinning NMR to study histones H3 and H4 tails dynamics and DNA interactions. Our results suggest that histone tails remain dynamic not only in a nucleosome context, but even in highly condensed nucleosome-arrays with 30bp linker DNA. We also find evidence that suggests the tails interact with their own nucleosomal DNA, and that linker DNA length has a modest influence in their flexibility.


Session: SOLIDS, poster number: 143

Preparing PH Domain Nanocrystalline Samples to Study PH Domain-Phosphatidylinositol Phosphate Interactions via Solid-State NMR


Stefany Lazieh1; Jacqueline Perodeau1; An Kitamura2; Andrew Nieuwkoop1
1Rutgers University, New Brunswick, NJ; 2Carleton University, Northfield, MN

Phosphatidylinositol phosphates (PIPs) are a class of membrane lipid involved in regulating cellular growth, metabolism, immunity, and development. Membranes containing PIPs can be specifically bound by proteins containing a pleckstrin homology (PH) domain, a family of highly conserved domains found in several hundred signaling proteins. Despite being implicated in diseases like diabetes, cancer, and obesity, direct analysis of PIP-PH domain interactions still poses difficulties. MAS solid-state NMR is suited to providing atomic resolution analysis and serves as a tool to understand the structural changes associated with binding within the protein and at the lipid surface. We are preparing nanocrystalline protein samples of the Kindlin-2 PH domain, which is essential for solid-state assignments and binding studies with various PIP species.


Session: SOLIDS, poster number: 144

Probing the structure and dynamics of large protein complexes using segmental isotopic labeling and solid state NMR


Yuuki Wittmer; Rong Hu; Rachelle Stowell; Rebecca Rafique; Natalie Boulos; Dylan Murray
Univ. of California, Davis, Davis, 0

In theory, solid state NMR allows for the characterization of protein structure and dynamics of large protein assemblies with no upper limit in size. Limited spectral space for the signals from the protein molecules places a practical upper limit on the size of the assembly that can be probed. We implement segmental isotopic labeling using intein chemistry to selectively incorporate NMR-visible isotopes into subdomains of protein molecules. We present results for proteins involved in the formation of intermediate filament networks in the cell cytoskeleton and RNA-binding proteins that form both membraneless organelles and pathological inclusions in neurodegenerative disease. Our data show that segmental isotopic labeling is a key and viable technology for probing the molecular conformations of these proteins.


Session: SOLIDS, poster number: 145

Cross-Seeding Specificities of Mammalian Y145Stop Prion Protein Amyloids studied by Solid-State NMR


Tara George1; Theint Theint1; Krystyna Surewicz2; Witold Surewicz2; Christopher P. Jaroniec1
1The Ohio State University, Columbus, OH; 2Case Western Reserve University, Cleveland, OH

Prion strain diversity and transmission barriers, two significant features of mammalian prion propagation, believed to be linked to the three-dimensional structures of prion fibrils. solid-state NMR establish that human, mouse and Syrian hamster PrP23-144 variants adopt distinct amyloid core structures. We use solid-state NMR to investigate cross-seeding specificities of the PrP23-144 variants where the amyloid formation by a monomeric protein from one species is seeded with preformed fibril seeds from another species. We observed that the newly formed PrP23-144 amyloids can adopt a structure different from the native one of both species, that resembles the one obtained in an unseeded reaction of the native parent protein or that of the conformation of the seed from a different species.  

 


Session: SOLIDS, poster number: 146

Anionic Lipid Tethering Promotes an Open Activated State of an Inward Rectifying Potassium Channel.


Collin Borcik; Derek Versteeg; Maryam Yekefallah; Reza Amani; Benjamin Wylie
Texas Tech University, Lubbock, TX

Inward-rectifier K+ (Kir) channels are transmembrane proteins which play vital roles in excitable cells. Kir channel loss of function mutations lead to heart disease and a host of blood and brain disorders. Bacterial KirBac1.1 has high homology to its human counterparts and is producible in NMR quantities making it a good structural model for Kir channel studies. Functional assays and SSNMR studies reveal global modes of channel activation by anionic lipids. Water-edited polarization transfer reveal large alterations to C-terminal domain orientations tied to gating. These identified structural changes correlate to the presence or absence of key anionic lipid binding residues. These findings highlight important interactions with anionic lipids and give insight into the molecular mechanisms involved in channel activation.


Session: SOLIDS, poster number: 147

Conformational changes upon gating of KirBac1.1 into an open-activated state revealed by solid-state NMR and functional assays


Reza Amani1; Collin Borcik1; Nazmul Khan1; Derek Versteeg1; Maryam Yekefallah1; Hoa Do2; Heather Coats1; Benjamin Wylie1
1Texas Tech University, Lubbock, TX; 2Texas Tech University Health Science Center, Lubbock, TX

The conformational changes required for activation and K+ conduction in inward-rectifier K+ (Kir) channels are still debated. These structural changes are brought about by lipid binding. We examine the structural details of KirBac1.1 reconstituted into both POPC and an activating lipid mixture of 3:2 POPC:POPG (wt/wt). KirBac1.1 is in a constitutively active state in POPC:POPG bilayers through the use of real-time fluorescence quenching assays and Förster resonance energy transfer (FRET) distance measurements. Multidimensional solid-state NMR (SSNMR) spectroscopy experiments reveal two different conformers within the transmembrane regions of the protein in this activating lipid environment, which are distinct from the conformation of the channel in POPC bilayers.


Session: SOLIDS, poster number: 148

Investigation of Cholesterol Clustering in Lipid Bilayers by 19F and 13C Solid-State NMR


Matthew Elkins1; Asanga Bandara2; George Pantelopulos2; John Straub2; Mei Hong1
1MIT, Cambridge, MA; 2Boston University, Boston, MA

Cholesterol is ubiquitous in mammalian cell membranes and influences the physical properties of the lipid bilayer by interacting with proteins, lipids, and itself. We used orthogonal 13C biosynthetic labeling of cholesterol and 13C–13C 2D correlation NMR to detect cholesterol dimers in lipid membranes. Using fluorinated cholesterol, 2D 19F CODEX experiments, and MD simulations, we also observed cholesterol tetramers at high concentrations. Measurements of 1H–13C dipolar couplings revealed multiple cholesterol populations and suggest that cholesterol dimers are common. Cholesterol self-association has significant implications on how cholesterol may interact with proteins to regulate biological functions.


Session: SOLIDS, poster number: 149

Exploring Long-Range Contacts and Hydrogen Bonds in Proteins with Proton Detected Solid-State Magic Angle NMR


Jacqueline Perodeau1; Daniel Friedrich2; Hartmut Oschkinat2; Andrew J. Nieuwkoop1
1Rutgers University, Piscataway, NJ; 2FMP, Berlin, Germany

1H detection is an increasingly important part of the structure determination process for solid protein samples.1 Long-range contacts between protons and heavy atoms, such salt bridges and hydrogen bonds, are amongst the most important interactions defining protein structure, function, and dynamics. By combining fast and ultra-fast magic angle spinning (MAS) with back-exchanged 2H, 13C, 15N isotopically labeled micro and nanocrystalline protein samples, we developed a pair of 1H detected 3D HCN experiments (hNCOH/hNCAH) in which hydrogen bonds are correlated with either the i-1th CO or the ith CA, respectively. These experiments open new routes for probing secondary structure and the functionally relevant protons in solid samples.


Session: SOLIDS, poster number: 150

Accuracy and Precision of Protein Structures Determined by MAS NMR Spectroscopy


Ryan Russell1, 2; Manman Lu1, 3; Matthew Fritz1, 2; Jodi Kraus1, 2; Caitlin Quinn1; Angela Gronenborn2, 3; Tatyana Polenova1, 2
1University of Delaware, Newark, DE; 2Pittsburgh Center for HIV Protein Interactions, Pittsburgh, PA; 3University of Pittsburgh, Pittsburgh, PA

We present a systematic investigation into the attainable accuracy and precision of protein structures determined by heteronuclear magic angle spinning solid-state NMR for a set of four proteins of varied size and secondary structure content. Structures were calculated using synthetically generated random sets of C-C distances up to 7 Å at different degrees of completeness. For single-domain proteins, 9-15 restraints per residue are sufficient to derive an accurate model structure, while maximum accuracy and precision are reached with over 15 restraints per residue. For multi-domain proteins and protein assemblies, additional information on domain orientations, quaternary structure and/or protein shape is needed. As demonstrated for the HIV-1 capsid protein assembly, this can be accomplished by integrating MAS NMR with cryoEM maps.


Session: SOLIDS, poster number: 151

Comparison of RF Heating between Conventional and E-free Comprehensive Multiphase Probes for In-vivo NMR


Paris Ning1; Daniel Lane1; Rajshree Ghosh Biswas1; Ronald Soong1; Daniel Schmidig2; Thomas Frei2; Peter De Castro2; Ivan Kovacevic2; Stephan Graf2; Sebastian Wegner3; Falko Busse3; Jochem Struppe4; Michael Fey4; Henry J. Stronks5; Martine Monette5; Myrna J. Simpson1; Andre J Simpson1
1University of Toronto, Toronto, Canada; 2Bruker Biospin AG (Switzerland), Fällanden, Switzerland; 3Bruker BioSpin Corp., Billerica, MA; 4Bruker BioSpin, Rheinstetten, N/A; 5Bruker Ltd., Milton, ON
Studying living organisms is critical to understanding biological processes, disease progression and response to environmental stressors. Comprehensive multiphase (CMP) NMR integrates all electronics and hardware required to differentiate components in different phases (solids, gels, liquids) in living organisms. However, heat produced by decoupling in solid state experiments can decrease the organism’s survivability. An E-free CMP coil platform was developed to reduce heat output. KBr solution is used to calculate temperature change from its chemical shift. By comparison, with 50 kHz decoupling bandwidth the new platform lowers the heat output ~10 fold over a conventional solenoid design. The reduction of heat output widens CMP-NMR’s application to heat sensitive samples including in-vivo research.

Session: SOLIDS, poster number: 152

Comprehensive Multiphase E-Free I-Probe: 13C Optimized Analysis of Complex Natural Samples


Rajshree Ghosh Biswas1; Ronald Soong1; Paris Ning1; Daniel Schmidig2; Thomas Frei2; Peter De Castro2; Ivan Kovacevic2; Stephan Graf2; Till Kuehn2; Sebastian Wegner3; Falko Busse3; Jochem Struppe4; Michael Fey4; Henry J. Stronks5; Martine Monette5; Myrna J. Simpson1; Andre J Simpson1
1University of Toronto, Toronto, ON; 2Bruker Biospin AG, Fällanden, Switzerland; 3Bruker BioSpin, Rheinstetten, Germany; 4Bruker BioSpin, Billerica, MA; 5Bruker Canada Ltd, Milton, ON

The introduction of the new comprehensive multiphase (CMP) I-Probe (E-free MAS) allows for automated multiphase analysis of complex natural samples. One of the most attractive features of the I-Probe is its E-free design with the 1H coil far removed from the sample, thus significantly reducing RF heating. Furthermore, the I-Probe design is the first CMP probe to be fitted with an automatic tuning and matching module. In combination with HR-MAS Topshim and an autosampler, this opens the possibility of high-throughput screening of intact samples. Moreover, the additional 13C sensitivity permits natural 13C abundance experiments on non-enriched samples. All in all, the I-Probe CMP probe has the potential to be a central tool in high-throughput toxicity screening and contaminant fate studies.


Session: SOLIDS, poster number: 153

A Mechanistic Study of Proton Insertion and Defects in Electrochromic Zinc Oxide Formed in Alkaline Electrolytes by Solid-State NMR Spectroscopy


Brendan E. Hawkins; Ankur L. Jadhav; Sanjoy Banerjee; Damon E. Turney; Robert J. Messinger
The City College of New York, New York, NY

Zinc oxide (ZnO) is of great interest for next-generation energy applications, though its application in optoelectronic devices has been limited by incomplete understanding of its defect structures. Here, solid-state magic-angle-spinning (MAS) NMR was used to better understand the proton insertion mechanism and characterize local defects in electrochromic ZnO. Solid-state 1H and 2H MAS NMR measurements conducted under quantitative conditions establish that additional species with limited mobility were present in ZnO after coloration, which were not present in bleached ZnO. Additional insights into the defect structures of ZnO were revealed through use of 2D 1H-1H exchange spectroscopy (EXSY), 1H-1H double-quantum-filtering (BABA-xy-16), and single-pulse 67Zn MAS NMR measurements.


Session: SOLIDS, poster number: 154

Understanding the Surface Interactions of a Model Sugar on Lewis Acidic Metal Oxides


Sean Najmi; Andrew Medford; Carsten Sievers
Georgia Institute of Technology, Atlanta, Georgia

Erythrose, a cyclic C4 sugar, is used as a model compound to provide insight into the fundamental interactions of sugars with Lewis acidic metal oxides. A dilute erythrose solution was impregnated over the following materials: Al2O3, CeO2, Nb2O5, SiO2, SnO2, TiO2, and ZrO2.  Nb2O5 produced the most surface species in the aliphatic, olefinic and carbonyl region of the spectrum. SiO2 was not active and only showed a physisorbed state of erythrose, however, heating to 50 C produced a signal in the carbonyl region suggesting a ring opening reaction occurred facilitated by the surface. Contact time experiments were done to understand the strength of adsorption of different sugar moieties by varying the magnetization transfer time.


Session: SOLIDS, poster number: 155

The Colorful Picture of Nanocrystals: An NMR Perspective


Xueqian Kong
Zhejiang University, Hangzhou, China

Nanocrystals are an important class of nanomaterials which have shown great promise in next-generation electro-optical devices, heterogeneous catalysis and biomedical applications. In a series of recent works, we advanced the fundamental understanding of the surface chemistry of CdSe nanocrystals using a full set of solid-state and solution-state NMR characterizations. For example, we revealed coordination structure of ligands, uncovered the partitioning of mixed ligands, elucidated the intrinsic effect of ligand dynamics on solution dispersity, investigated the inorganic core structures, and analyzed the ligand exchange processes. Our NMR research builds up the quantitative connections between the molecular picture of nanocrystal-ligands complexes and their macroscopic properties.


Session: SOLIDS, poster number: 156

Structure and dynamics of ionic liquid and polymer gel electrolytes by NMR spectroscopy


Mounesha N Garaga1; Nishani Jayakody1; Boris Itin2; Steven Greenbaum1
1Hunter College of CUNY, New York, NY; 2New York Structural Biology Center, New York, NY

Designing new-type of electrolytes require their better understanding and correlation of transport properties with its molecular structure. In this respect, polymer electrolytes  have been emerging materials for Li ion battery applications. In this study, ionic liquid electrolytes, in particular ammonium- and phosphonium-based ILs, and PMMA polymer gel electrolytes have been explored by NMR spectroscopy. PFG and solid state NMR helps in understanding the dynamics and local interactions of mobile ions within the polymer network. In addition, the fast field cycling relaxometry technique, measuring the T1 relaxation, probes the mobility ionic species.

 


Session: SOLIDS, poster number: 157

Molecular-Level Environments of Chloroaluminate-Intercalated Graphite Electrodes Revealed by Solid-State NMR and DFT Methods


Jeffrey H. Xu; Ankur L. Jadhav; Damon E. Turney; Robert J. Messinger
The City College of New York, CUNY, New York, NY

Rechargeable aluminum-graphite batteries using chloroaluminate-containing ionic liquid electrolytes are a promising beyond-lithium battery technology that store energy by electrochemically intercalating AlCl4- anions. However, the local environments and molecular geometries of the intercalant chloroaluminate species are not well understood. Here, we use solid-state MAS 27Al NMR spectroscopy to probe the local environments of intercalated AlCl4- anions as a function of state-of-charge. To interpret the 27Al NMR shifts, density functional theory (DFT) methods were employed to compute the relative contributions of different NMR interactions for a [AlCl4-]-bilayer coronene model. Correlation of the DFT-calculated 27Al isotropic shifts compared well to the experimental 27Al NMR shifts and established consistent descriptions of the molecular geometry of the ionic intercalants at extents of intercalation.


Session: SOLIDS, poster number: 158

Identifying Aspirin Polymorphs from Combined DFT-based Crystal Structure Prediction and Solid-State NMR


Lydia Gkoura1; Renny Mathew1; Karolina Uchman1; Chris Pickard2, 3; Maria Baias1
1New York University Abu Dhabi, Abu Dhabi, United Arab Emirates; 2University of Cambridge, Cambridge, UK; 3Tohoku University, Sendai, Japan

A combined experimental and computational approach was used to distinguish between different polymorphs of the pharmaceutical drug aspirin. For this purpose we used Ab Initio Random Structure Searching (AIRSS), a DFT-based crystal structure prediction method for the prediction of polymorphic structures, with DFT calculations of the NMR parameters and solid-state NMR experiments at natural abundance. We were able to discriminate the two different polymorphs and identify form-I as the polymorph present in our sample, by the use of the root-mean-square deviation between experimental and calculated 1H chemical shifts. Our results illustrate that AIRSS can successfully predict the crystal structure of organic molecular crystals and it can be used together with NMR chemical shifts in order to identify different pharmaceutical polymorphs.


Session: SOLIDS, poster number: 159

Molecular-Level Insights on the Charge Storage Mechanisms of Rechargeable Aluminum Batteries Revealed by Solid-State NMR Spectroscopy


Robert Messinger; Ankur Jadhav; Jeffrey Xu; Leo Gordon; Rahul Jay
The City College of New York, New York, NY

Rechargeable aluminum metal batteries have great promise: aluminum is energy dense, low cost, earth abundant, and inherently safe. However, development of positive electrode materials that pair with aluminum anodes has been hindered, in part, by limited understanding of their charge storage mechanisms. Here, recent progress will be discussed on the application of solid-state NMR to the development and understanding of positive electrode materials, including graphites, crystalline transition metal sulfides, organic compounds, and elemental sulfur. Molecular-scale understanding of their diverse ionic and electronic charge storage mechanisms are revealed by solid-state NMR, ranging from electrochemical intercalation of molecular or aluminum ions to reversible anionic redox processes. The results highlight the critical role that solid-state NMR plays in understanding emerging aluminum battery chemistries.  


Session: SOLIDS, poster number: 160

ex-situ NMR studies on zintl phases formation of Si anodes


Xiang Li; Baris Key; Fulya Dogan; Stephen E Trask; James A Gilbert; John T Vaughey
Argonne National Laboratory, Lemont, IL

Si is one of the most promising anode candidates in LIBs. The interphase stability between Si anode and electrolyte can be improved significantly by adding 0.1 M MTFSI salts (M =Mg, Al, Zn, Ca). To understand the mechanism of Zintl phases formation upon lithiation/delithiation process, high-resolution 7Li and 29Si NMR is utilized to directly probe the local Li and Si environments.


Session: SOLIDS, poster number: 161

Characterization of heterogeneous single-site metal catalyst immobilized support materials by advanced solid-state NMR spectroscopy


Takeshi Kobayashi1; Zhuoran Wang1, 2; Frederic A. Perras1; Marek Pruski1, 2
1US DOE Ames Laboratory, Ames, IA; 2Department of Chemistry, Iowa State University, Ames, IA

Single-site metal catalysts immobilized on high surface area materials, including metal oxides and metal-organic frameworks, demonstrate excellent catalytic performance as well as a high atomic utilization of metals. To tailor their properties, a detailed picture of their atomic-scale structure is indispensable. We will present recent examples from our lab of the applications of advanced solid-state NMR techniques, including fast-MAS and DNP, to the structural studies of heterogeneous single-site metal catalysts. For instance, we used a suite of fast MAS experiments on a La{C(SiHMe2)3}2 catalyst to determine detailed structure of the complex. In another example, we applied DNP-enhanced 13C CSA recoupling on a supported ditungsten catalyst to distinguish the signals from ligands coordinated to surface-bound and cantilevered W sites.


Session: SOLIDS, poster number: 162

Characterization of structural heterogeneity in carbon fluorides


Brennan J. Walder; Todd M. Alam
Sandia National Laboratories, Albuquerque, NM

Carbon monofluoride, (CF)n, is the fully fluorinated end-member of a series of fluorinated graphite materials, CFx (x = F:C ratio), whose idealized structures possess extended two-dimensional carbon frameworks.  Here we investigate the structure of several CFx samples using multidimensional 13C and 19F solid-state MAS NMR experiments. In these materials we find evidence of structures which are far from ideal.  Quantitative 13C and 19F NMR spectra confirm significant quantities of defective CF2 and CF3 functional groups.  Two-dimensional 19F spin diffusion EXSY and spectral editing experiments demonstrate that magnetization of deshielded CF groups flows through shielded CF groups prior to reaching CF2 groups. We propose a fluorographene-based structural model for (CF)n which attributes our observations to the finite size of the sheets.


Session: SOLIDS, poster number: 163

Exploiting inherent paramagnetic effects in transition metal exchanged zeolites as predictors of catalytic activity


Joseph Palamara; Jeff Yang; Ahmad Moini; Subramanian Prasad
BASF Corporation, Iselin, NJ

Silicon-29 spin-lattice relaxation time (T1) NMR provides information on the nature and distribution of the transition metal-ion containing  species within zeolites. By observing changes in T1 values after thermal treatment, it is possible to observe distribution, mobility and stability within different zeolite structures while providing correlation of catalytic activity.


Session: SOLIDS, poster number: 164

An NMR Crystallography Approach to Determine the Supramolecular Structure of Layered Hybrid Perovskites


Michael Hope; Aditya Mishra; Manuel Cordova; Paramvir Ahlawat; Toru Nakamura; Dominik Kubicki; Claudia Avalos; Ursula Roethlisberger; Jovana Milic; Michael Graetzel; Lyndon Emsley
EPFL, Lausanne, Switzerland

Layered 2D perovskites, which comprise perovskite slabs separated by a hydrophobic organic spacer layer, are promising photovoltaic materials due to their high environmental stability. The structure of the organic spacers is key in determining the optoelectronic properties but can be challenging to determine using conventional techniques. In this work we reveal the supramolecular structure of the organic spacers by combining solid-state NMR and theoretical calculations in an NMR crystallography approach. We compare the structures for 2D perovskites and 3D perovskites which have been doped with the spacers, as well as for different combinations of organic spacers. This reveals important design principles to harness non-covalent interactions in 2D/3D hybrid perovskites, and paves the way for ever-more efficient optoelectronic devices.


Session: SOLIDS, poster number: 165

Metal-Organic Framework (MOF) Structure, Ligand Dynamics, and Electrochemical Behavior as Supercapacitor Electrodes


Christopher Klug1; Catherine Choo2; Boris Dyatkin1; Mark Palenik1; Carlos Hangarter1; Matthew Laskoski1; Joel Miller1
1U. S. Naval Research Laboratory, Washington, District of Columbia; 2Thomas Jefferson High School, Alexandria, Virginia

Metal-organic frameworks (MOFs) have tremendous potential for use in energy storage devices.  We have used a combination of solid-state NMR and DFT calculations to characterize the structure and dynamics of two MOFs: for a Zr-based MOF we observed clear evidence of linker dynamics in the 13C NMR while for a Co-based MOF we observed effects due to the paramagnetism of Co.


Session: SOLIDS, poster number: 166

The genesis mechanism of the core-shell structure of hydroxyapatite nanoparticles in bone and in flask


Hung-Hsiang Wei1; Yi-Chun Lai1; Po-Yu Cheng1; Dinbedhu Thakur1; Song Seng Loke2; Shangwu Ding1
1Natl Sun Yat-sen Univer, Kaohsiung, Taiwan; 2Chang-Gung Memorial Hospital, Kaohsiung, Taiwan

The precise determination of the morphology of hydroxyapatite (HAp, the inorganic component in bone) remains a challenge. Based on solid state NMR spectra and translational diffusion measurement, we show ubiquitous presence of core-shell structure of synthetic or natural hydroxyapatite nanoparticles. The volume ratio of core to shell can be accurately quantified with 1H-31P HETCOR and 1H-1H double quantum coherence spectra. We propose a theoretical interpretation of the phenomenon supported by electrostatics and quantum chemistry calculations. The differences in structure and morphology of HAp nanoparticles in vivo and in vitro are explained with theoretical analysis and numerical calculations. The implications of this work to bone physiology and pathology as well as bone/tooth  replacement materials, coating materials, drug delivery materials are to be discussed.


Session: SOLIDS, poster number: 167

Framework flexibility-driven CO2 adsorption on zeolites - an NMR crystallography study. 


Eric Breynaert1; Hyun June Choi2; Sambhu Radhakrishnan1; Vinod Nair1; Suk Bong Hong2; Christine E.A. Kirschhock1
1KULeuven; COK-kat, Leuven, Belgium; 2Postech, Pohang, Korea

Capture and storage of carbon dioxide has been proposed as an effective strategy to reduce global warming. Owing to its low cost and eco-friendly properties, adsorption-driven capture of CO2 is attracting increasing interest. Here we present an alkaline cation exchanged zeolite exhibiting stepped CO2 isotherms, enabling CO2 uptake capacities of 3.5–3.8 mmol/g at 25°C and 1 bar. Exact localization of CO2 and extraframework cations was essential in understanding this reversible uptake. NMR crystallography combining Rietveld refinement, absolute MAS-NMR quantification and multidimensional ssNMR experiments allowed identification of the mechanism driving ad- and desorption of CO2. The framework flexibility determines the up-take and release of CO2, allowing temperature swing operation at surprisingly low temperatures for adsorbent regeneration. 


Session: SOLIDS, poster number: 168

Multiphysics NMR correlation spectroscopy


Yiqiao Tang
Schlumberger-Doll Research, Cambridge, MA

Modern NMR spectroscopy owes its power in molecular studies to correlation methodology, yet only spin Hamiltonians are considered in a single physics experiment. We break the constraints by incorporating correlations between completely different physical processes. We illustrate the idea by examples of capillary drainage vs NMR correlation experiments for porous media, and demonstrated that the new method reveals novel insights into the pore connectivity that has long-evaded experimental studies. This new approach is valuable for natural and engineered porous media, as well as nanoporous materials. Other dynamic and thermodynamical processes may be incorporated in a similar fashion for applications beyond these examples.


Session: SOLIDS, poster number: 169

Fast Field Cycling NMR Relaxometry to Reveal Food Properties


Pellegrino Conte1; Moreno Pasin2; Rebecca Steele2; Philippe R. Bodart3, 4; Jadwiga Tritt-goc5; Adam Rachocki5; Luciano Cinquanta1; Mecit Halil Oztop6; Pedro J. Sebastiao7; Maria I. Tavares8; Gianni Ferrante2
1University of Palermo, Palermo, Italy; 2Stelar s.r.l., Mede (Pv), Italy; 3Université Bourgogne Franche-Comté, Dijon, France; 4Université des Sciences et Technologies de Lille, Lille, France; 5Polish Academy of Sciences, Poznan, Poland; 6Middle East Technical University, Ankara, Turkey; 7Universidade de Lisboa, Lisboa, Portugal; 8Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
Fast Field Cycling is a low-field NMR technique which allows the measurement of the longitudinal relaxation time T1 (=1/R1) of samples (both liquids and solids) as a function of the strength of the applied magnetic field. In this work, we report a few case studies showing important FFC applications to food science. FFC NMR relaxometry is shown to be a powerful method through, revealing the presence of pork-beef in frankfurters; evaluating the crystallization induction times of cocoa butter, one of the main components in chocolate manufacturing; characterizing wines; revealing fraud in the production of balsamic vinegars; observing liquified honey and starches in fruit seeds; measuring the shelf-life of dried apple slices produced with different drying methods.

Session: SOLIDS, poster number: 170

Gyrotrons and MAS spheres for Frequency-chirped and In-cell DNP


Chukun Gao1; Nicholas Alaniva1; Edward Saliba1; Lauren Price1; Pin-Hui Chen1; Thomas Osborn Popp1; Sarah Overall1; Patrick Judge2; Erika Sesti2; Alexander Barnes1
1ETH, Zurich, Switzerland; 2Washington University in St. Louis, St. Louis, MO

We present the development for frequency-chirped and in-cell DNP. An enhancement of 60 is achieved within intact human cells using a fluorescent, targeting polarizing agent. DNP enhancement of 46 within Jurcat cells demonstrates the ability to detect cellular activation of HIV provirus. Improvements in gyrotron design result in three times higher microwave power output. A 19% higher DNP enhancement is achieved using the frequency-chirped microwaves than continuous wave. We also present the feasibility of downscaling spherical rotors to achieve faster MAS. 3-fold increase in MAS frequency is obtained scaling down from 9.5 mm to 4 mm spheres. Ongoing development on 2 mm and smaller spheres shows promise for higher MAS frequency.


Session: SOLIDS, poster number: 171

Use of Reverse-Wound Solenoids for 1.5 GHz Solid State NMR


Peter L. Gor'kov; Wenping Mao; Jason Kitchen; Ivan Hung; Zhehong Gan; William W. Brey
National High Magnetic Field Laboratory, Tallahassee, FL
We report use of reverse-wound solenoids for construction of high field 1.5 GHz 3.2 mm MAS 1H/X solid-state NMR probe. The reverse-wound coil is a low-inductance geometry that mimics the current distribution of a conventional solenoid. At the very high fields such as 1.5 GHz, reverse-wound coils can help retain sample sizes that are common for sub-GHz spectrometers. Used with cross-coils they can alleviate tunability issues, reduce dielectric losses in biological samples at high 13C frequency. They also raise B1 fields that can be sustained by a relatively large sample probe without arcing, due to reduced voltage in RF circuit.

Session: SOLIDS, poster number: 172

Cryogen-free magnets for magnetic resonance applications


Eugeny Kryukov1; Angel Joaquin Perez Linde1; Seema Raghunathan1; Stephen Burgess1; Paul Jonsen1, 2; Jeremy Good1
1Cryogenic Ltd, London, UK, London, United Kingdom; 2Talavera-Science, Harrogate, UK

The temporal magnetic field variation in cryogen-free magnets was studied. Displacement of the magnet inside the cryostat appeared to be the main issue of magnetic field perturbation. In a cryostat with the Gifford- McMahon type of cryocooler, motion of the displacer with magnetic material inside also produces significant field modulation. The temperature variation of the magnet, although noticeable, leads to smaller field distortions compared to the previous two factors. It was shown that the temporal magnetic field variation could be reduced down to below 20 ppb level that could be acceptable for MRI and MAS NMR applications. It was also shown that a single cryogen-free magnet could be easily used at different fields on a day-to-day basis without compromising the field stability.


Session: SOLIDS, poster number: 173

Reducing Coherent RFI in QR Detection Systems through Pulse Sequence Manipulation


Xinxing Meng; Jeffrey L. Schiano
The Pennsylvania State University, University Park, PA

The effect of AM broadcast interference on detection of energetic materials using quadrupole resonance (QR) remains a challenge despite the use of techniques such as shielding, narrow-band probes, and adaptive cancellation. Within the passband of the QR receiver, the AM RFI is represented by the superposition of two components, one due to the information contained in the sidebands, and the other due to the carrier. Signal averaging is effective at reducing the sideband components due to the stochastic nature of the modulation signal. On the other hand, the carrier component is deterministic. We show by appropriately choosing the spacing between RF sequences and pulses, averaging can significantly reduce the RFI component caused by the AM carrier.


Session: SOLIDS, poster number: 174

Toward a Cryogenically-Cooled High-Sensitivity System for Nuclear Quadrupole Resonance Spectroscopy


Jarred Glickstein1; Soumyajit Mandal2
1Case Western Reserve, Cleveland, OH; 2University of Florida, Gainesville, FL

In recent work, we have combined polarization enhanced nuclear quadrupole resonance (PENQR) spectroscopy with a digitally-tunable matching network to obtain improved signal-to-noise ratio (SNR) over a broad frequency range. Ongoing work aims to further improve system performance by i) switching to an analog tunable network to increase the number of available tuning frequencies, and ii) by reducing the thermal noise 4kTR in the coil and preamplifier through cryogenic cooling in liquid nitrogen at 77K.


Session: SOLIDS, poster number: 175

Cryogen Free Magnets for Magnetic Resonance Applications 


Eugeny Kryukov1; Angel Joaquin Perez Linde1; Seema Raghunathan1; Stephen Burgess1; Paul Jonsen2; Jeremy Good1
1Cryogenic Limited, London, UK; 2Talavera Science, Harrogate, UK

 

While cryogen-free cryostats are becoming more popular, applications for high resolution MR are limited by time dependent magnetic field variations. We consider three pathways which lead to temporal field variations and show advancements in magnet technology which minimize these sufficiently to make NMR viable.

Mechanical displacements of the magnet are a significant source, but better magnet fixation can reduce instabilities below 20ppb. Instability from magnetic piston materials in GM cryocoolers can be eliminated with a superconducting shield.

Temperature variation within the coldhead cycle can be minimized through the use of a thermal buffer.

Lastly we show that a cryogen-free cryostat can accelerate the settling of the magnetic field to below 0.2ppm/hr within one hour of ramping to full field.

 

 


Session: SOLIDS, poster number: 176

3D Printed Sample Tubes for Solid-State NMR Experiments


Zheng Long; Jamie Ruthford; Stanley Opella
UC San Diego, La Jolla, CA

NMR benefits from improvements in instrumentation; chiefly the probe, which provides the interface between the sample and the RF irradiations and detections that constitute the experiment.  Both the electronic components (capacitors and inductors) and their arrangement are crucial factors in determining performance. Here we combine standard components in unique arrangements made possible by the use of 3D printing in the fabrication of the probe and demonstrate the use of an inexpensive commercial 3D printer to fabricate multiple probe components that can be combined in the assembly process.


Session: SOLIDS, poster number: 177

Creating a Generalizable Approach to Achieve Optimized Field Profiles in ssNMR RF Transceivers


Jessica Kelz
UC Irvine, Irvine, CA

To address the challenge of reliably achieving wire transceiver coil designs we developed removable 3D-printed polymer templates referred to as DIAPERs. This work has led to a collaborative effort to design and fabricate coils with optimized magnetic field profiles for use in state-of-the-art ssNMR probes. Experimental considerations have been defined as constraints in simulation software for parameterization to maximize the axial homogeneous region of a variable-pitch solenoid for use in a 3.2mm cylindrical rotor MAS probe. DIAPERs will be used to fabricate the design for testing in a 500MHz magnet. This work is focused on experimentally driven objectives, providing spectroscopists with a reproducible, scalable and generalized method for design and fabrication of new high-performance coil forms for novel applications.


Session: SOLIDS, poster number: 178

Increasing NQR Detection Range from a Surface Coil using Composite Pulse Excitation


Garrett Lee; David Prescott; Karen Sauer
George Mason University, Fairfax, VA

Nuclear quadrupole resonance, or zero-field NMR, can be used to detect illicit substances semi-remotely using a surface coil; for instance, the detection of explosives buried in the ground.  Typically, an initial excitation is followed by a train of refocusing pulses to increase the signal-to-noise ratio.  The effective tip angles in the pulse sequence, can depend dramatically on the distance between the coil and sample, due to the field fall-off from the coil. This leads to non-uniform sample excitation within a target region. Using ammonium nitrate, we demonstrate the use of a composite excitation pulse to obtain signal 1.5 times better than a spin-lock spin-echo sequence in a region of 10 cm displaced from the coil; compensating for the field fall-off.