Biomedical subjects

Yudong Wu

Publications and source records attributed to Yudong Wu.

3 recordsLinked to original sources

PubMed2005

Protonation-induced stereoisomerism in nicotine: conformational studies using classical (AMBER) and ab initio (Car-Parrinello) molecular dynamics.

A variety of biologically active small molecules contain prochiral tertiary amines, which become chiral centers upon protonation. S-nicotine, the prototypical nicotinic acetylcholine receptor agonist, produces two diastereomers on protonation. Results, using both classical (AMBER) and ab initio (Car-Parrinello) molecular dynamical studies, illustrate the significant differences in conformational space explored by each diastereomer. As is expected, this phenomenon has an appreciable effect on nicotine's energy hypersurface and leads to differentiation in molecular shape and divergent sampling. Thus, protonation induced isomerism can produce dynamic effects that may influence the behavior of a molecule in its interaction with a target protein. We also examine differences in the conformational dynamics for each diastereomer as quantified by both molecular dynamics methods.

Molecular Conformation↗

PubMed2004

Structural basis for the restoration of TCR recognition of an MHC allelic variant by peptide secondary anchor substitution.

Major histocompatibility complex (MHC) class I variants H-2K(b) and H-2K(bm8) differ primarily in the B pocket of the peptide-binding groove, which serves to sequester the P2 secondary anchor residue. This polymorphism determines resistance to lethal herpes simplex virus (HSV-1) infection by modulating T cell responses to the immunodominant glycoprotein B(498-505) epitope, HSV8. We studied the molecular basis of these effects and confirmed that T cell receptors raised against K(b)-HSV8 cannot recognize H-2K(bm8)-HSV8. However, substitution of Ser(P2) to Glu(P2) (peptide H2E) reversed T cell receptor (TCR) recognition; H-2K(bm8)-H2E was recognized whereas H-2K(b)-H2E was not. Insight into the structural basis of this discrimination was obtained by determining the crystal structures of all four MHC class I molecules in complex with bound peptide (pMHCs). Surprisingly, we find no concerted pMHC surface differences that can explain the differential TCR recognition. However, a correlation is apparent between the recognition data and the underlying peptide-binding groove chemistry of the B pocket, revealing that secondary anchor residues can profoundly affect TCR engagement through mechanisms distinct from the alteration of the resting state conformation of the pMHC surface.

Alleles↗

PubMed2004

Mapping potential energy surfaces.

A recently proposed dynamical method [A. Laio and M. Parrinello, Proc. Natl. Acad. Sci. U.S.A. 99, 12562 (2002)] allows us to globally sample the free energy surface. This approach uses a coarse-grained non-Markovian dynamics to bias microscopic atomic trajectories. After a sufficiently long simulation time, the global free energy surface can be reconstructed from the non-Markovian dynamics. Here we apply this scheme to study the T=0 free energy surface, i.e., the potential energy surface in coarse-grained space. We show that the accuracy of the reconstructed potential energy surface can be dramatically improved by a simple postprocessing procedure with only minor computational overhead. We illustrate this approach by conducting conformational analysis on a small organic molecule, demonstrating its superiority over traditional unbiased approaches in sampling potential energy surfaces in coarse-grained space.

Journal Article↗