engleski

Modified glycopeptides related to cell wall peptidoglycan: conformational studies by NMR and molecular modelling

Peptidoglycans, the ubiquitous polymeric constituents of bacterial cell walls, and smaller glycopeptides derived from them, exhibit versatile biological activities including immunomodulating properies. The conformation of the peptidoglycan monomer (PGM, 1) from Brevibacterium divaricatum was studies previously in aqueous solution by 2D NMR and molecular modelling. Novel lipophilic derivatives of PGM bearing either Boc-Tyr or adamantyl-acetyl substituents (2 and 3, respectively) have recently been synthesized. Adamantyl-substituted PGM-related peptdies were shown to significantly influence the humoral immune response in mouse. We have therefore started an investigation into the conformational properties of these compounds in DMSO solutions. Complete 1-H and 13-C resonance assignments were achieved by standard 2D NMR techniques. Distance restraints derived from the MOESY/ROESY peaks were used in distance geometry calculations combined with energy minimization in a classical force field in order to evaluated conformational preferences. Comparison of the data obrained for the paredt molecule 1 with those for 2 and 3 in the same sovent revealed differences in the distributions of the preferred conformers ; the role of the lipophilic N-terminal groups introduces in the derivatives is discussed.

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