Exploring and characterizing the folding processes of Lys- and Arg-containing Ala-based peptides: a molecular dynamics study

In this study, molecular dynamics simulations were carried out on Lys- and Arg-containing Ala-based peptides (i.e. Ace-(AAAAK)(n)A-NH(2) and Ace-(AAAAR)(n)A-NH(2), where n=1-4), in order to explore and characterize their folding processes. For the oligopeptides, the evolution of α-helical structure with regard to the whole conformation, as well as to each residue was investigated, and the helix-forming propensities were characterized. On the basis of the helicity curves, representing the alteration of average helicity as a function of time, the typical time values describing the folding processes and subprocesses were identified. In the case of each peptide, the evolution and role of helix-stabilizing, non-local and side-chain-to-backbone H-bonds were examined. The appearing i←i+4 H-bonds pointed out the role of these interactions in the stabilization of α-helical conformations, while the occurring i←i+3 H-bonds indicated the presence of β-turn or 3(10)-helical structures. Studying the formation and role of non-local and side-chain-to-backbone H-bonds led to the observation that these types of interactions produced an effect on the evolution of helical conformations, as well as on the folding processes.     

Germanium/phosphorus cage compounds with germanium in three different oxidation states

Novel germanium/phosphorus cage compounds with new structural motifs have been synthesized containing germanium in three different oxidation states. The key to obtain this new class of compounds is the use of monolithiated primary phosphine LiHPtBu in the reaction with GeX(2).