Session TOC. There are 3 abstracts in this session.

Session: Computational NMR, time: 11:00am-11:40am

Calculation and analysis of NMR parameters with first-principles methods

Jochen Autschbach
SUNY Buffalo, Buffalo, NY
We will present selected applications of first-principles calculations within nonrelativistic and relativistic frameworks aimed at a detailed understanding of how molecular structure & chemical bonding are related to the nuclear magnetic shielding, indirect nuclear spin-spin (J) coupling, and electric field gradient involving a given nucleus.  Among the topics is the ab-initio molecular dynamics based calculation of quadrupolar and dipolar relaxation rates in solution, with applications to liquid water, alkali and halide ions and 14N relaxation in small heterocycles. Another topic will be relativistic and solvent effects of metal NMR parameters. Finally, we will discuss electron paramagnetic effects on ligand chemical shifts in metal complexes, calculated with Kohn-Sham and wavefunction methods.

Session: Computational NMR, time: 11:40am-12:20pm

Pursuing Crystallography without Diffraction Data

James Harper
University of Central Florida, Orlando, FL
This presentation explores the ability of solid-state NMR and computational methods to provide crystal structures for materials unsuitable for conventional crystallography. Initial focus is on accurately predicting structure of the individual molecule in the lattice.  Two paths are then described for expanding these structures into crystal structures.  One route provides complete crystal structures without diffraction data while the second uses certain information from powder diffraction. In each case, structures obtained have small inaccuracies and a final lattice-including refinement is needed to obtain coordinates that agree with NMR, diffraction and force data.  Recently, errors in individual atom positions similar to “thermal ellipsoids” have been added to these structures using a Monte Carlo sampling scheme.

Session: Computational NMR, time: 12:20pm-1:00pm

Exhaustive mapping of methyl assignments in large proteins

Nikolas Sgourakis
UC Santa Cruz, Santa Cruz, CA
The use of methyl probes has opened new avenues for the application of NMR methods to study large molecular machines.  Here, we describe a fully automated method which makes use of 2 NOE peak lists and a known crystal structure (or homology-based model), to exhaustively map the set of all possible consistent assignments using algorithms from the theory of exact computing. We present results from a benchmark set of 10 protein targets spanning a range of sizes from 20-45 kDa, therefore our method can deliver 100% correct, unambiguous assignments for up to 80% of methylbearing residues in the system. Finally, we discuss the use of our method to model the domain structure of larger proteins, guided by methyl NOEs