Study On The Relationship Between The Molecular Structures And Molecular Stacking Patterns Of Three Series Of Lipodipepdides

Peptides and peptide derivatives have attracted more and more attention due to many advantages such as good biocompatibility,low immunogenicity,structural programmability,cost-effectiveness and great potential for application in the area of new-occurring nanotechnology and biomedicine."C-terminal determination" rule was found to apply to some homogeneous lipodipeptides,however,for some heterogeneous lipodipepdies,the chirality of assemblies did not follow "C-terminal determination" rule due to different molecular packing mode.So studying the relation between molecular structure and molecular packing mode is of significance for understanding the self-assembly process deeply and designing lipopeptides with specific structure.In this paper,three series of lipodipeptides were designed and synthesized.The results are shown as follows:Firstly,compounds composed of different amino acids with different chirality can lead to different packing mode of carbonyl groups,interdigitated bilayer structure was formed by valine-alanine sodium salts;the hydrogels formed by valine-alanine sodium salts have thixotropic property and H-bonding interaction between molecules plays significant role in the formation and recovery of three-dimensional network structure;the self-assemblies can be aligned under directional force.Secondly,the self-assembly process of three C-2H25O-substituted C6H5COO-Ala-Ala dipeptides is time-dependent.Ortho-compound proceeds slowly morphologic transformation from kinetic control to thermodynamical control because of big steric hindrance,the increase of entropy is likely to drive association of moleculars to form kinetic-trapped assemblies and enthalpy drive the formation of thermodynamically favored state,the self-assembly process of meta-and para-compounds are driven by enthalpy because of relatively small steric hindrance.Thirdly,increasing the length of the amino acid branch,the steric hindrance is also increased,which has great influence on the way of molecular packing mode and the morphology of self-assemblies.