DyNAs: constitutional dynamic nucleic acid analogues

Dynamic cationic polymers were generated in aqueous media from functionally complementary monomers bearing nucleobase groups. (1)H NMR spectroscopy was used to follow the polycondensation reaction of the nucleobase-appended dihydrazides 1 and 2 with the dialdehydes B and C. The reversibility of these polymers was established by proton NMR spectroscopy through exchange of the dihydrazide 2 with polymer 1 B. The polymers 1 B, 2 B, 1 C, and 2 C represent dynamic biopolymers of nucleic acid type, DyNAs. Electrostatic interaction of these polymers with polyanionic entities, such as polyphosphates, polynucleotides, and polyaspartic acid, was shown to take place. It induces a change in size of the dynamic polymer, as it responds by an increase in degree of polymerization to an increase of the overall anionic charge introduced, that is, to the total electrostatic interaction.     

Molecular diversification in spider venoms: A web of combinatorial peptide libraries

Summary Spider venoms are a rich source of novel pharmacologically and agrochemically interesting compounds that have received increased attention from pharmacologists and biochemists in recent years. The application of technologies derived from genomics and proteomics have led to the discovery of the enormous molecular diversity of those venoms, which consist mainly of peptides and proteins. The molecular diversity of spider peptides has been revealed by mass spectrometry and appears to be based on a limited set of structural scaffolds. Genetic analysis has led to a further understanding of the molecular evolution mechanisms presiding over the generation of these combinatorial peptide libraries. Gene duplication and focal hypermutation, which has been described in cone snails, appear to be common mechanisms to venomous mollusks and spiders. Post-translational modifications, fine structural variations and new molecular scaffolds are other potential mechanisms of toxin diversification, leading to the pharmacologically complex cocktails used for predation and defense.     

矩阵乘积的初等变换术及其应用

通过矩阵乘法运算的拆行拆列表示,巧妙地绕过初等矩阵,建立了矩阵乘积的初等变换术,进而导出了原来运用初等矩阵才能导出的有关初等变换、逆矩阵、矩阵方程、矩阵等价的若干重要结果.     

运筹学课程教学中的探索与实践

结合教学实践经验,从提高学生的兴趣和积极性出发,在运筹学课程的教学过程中,提出了以学生为本,改进教学内容和教学方法,并把数学建模的思想融到运筹学课程的教学中去,从而提高学生的学习效果和教师的教学效果.     

Dithioacetal Exchange: A New Reversible Reaction for Dynamic Combinatorial Chemistry

Reversibility of dithioacetal bond formation is reported under acidic mild conditions. Its utility for dynamic combinatorial chemistry was explored by combining it with orthogonal disulfide exchange. In such a setup, thiols are positioned at the intersection of both chemistries, constituting a connecting node between temporally separated networks.     

Dynamic Combinatorial Enrichment of Polyconformational D‐/L‐Peptide Dimers

D ‐/L ‐Peptides such as gramicidin A (gA) adopt unique dimeric β‐helical structures of different topologies. To overcome their conformational promiscuity and enrich individual components, a dynamic combinatorial approach assisted by thiol tags was developed. This method led to identification of the preferential formation of antiparallel dimers under a broad range of conditions, which was independent of peptide side‐chain polarity. Exclusive formation of an antiparallel cyclic dimer was achieved in the presence of cesium ions.