Spectroscopy, Structure, Biomacromolecular Interactions, and Antiproliferation Activity of a Fe(II) Complex With DPA-Bpy as Pentadentate Ligand.

An Fe(II) complex with DPA-Bpy (DPA-Bpy = N,N-bis(2-pyridinylmethyl)-2,20-bipyridine-6 -methanamine) as the ligand was synthesized and characterized to mimic bleomycin. The binding constants ( ) of the complex with calf thymus DNA and human serum albumin (HSA) were quantitatively evaluated using fluorescence spectroscopy, with as 5.53×10 and 2.

Electronic effects on a mononuclear Co complex with a pentadentate ligand for catalytic H₂ evolution.

Previous studies of Co catalysts for H2 evolution have shown opposite effects between the redox potentials of Co centers and their catalytic properties such as the overpotential and turnover frequency: Co catalysts with more positive reduction potentials from structural modification display insignificant changes in the overpotential for H2 evolution and require stronger acid for catalysis, and Co catalysts with lower overpotentials show decreased turnover frequency for H2 evolution. In order to explore the electronic effects of a ligand scaffold on the catalytic properties for H2 evolution by a Co complex with a pentadentate ligand, N,N-bis(2-pyridinylmethyl)-2,2'-bipyridine-6-methanamine (DPA-Bpy), we replaced the pyridyls in DPA-Bpy with more basic isoquinoline groups. In contrast to data from previously reported studies, in the current study, a Co complex with a more positive reduction potential, resulting from the replacement of pyridyls with isoquinoline groups, leads to a lower overpotential and higher turnover frequency for both electro- and photocatalytic H2 production in neutral aqueous solution.

Self-assembling cyclic tetrapeptide from alternating C-linked carbo-beta-amino acid [(S)-beta-Caa] and alpha-aminoxy acid [(R)-Ama]: a selective chloride ion receptor.

A cyclic tetrapeptide is prepared from alternating (S)-beta-Caa (C-linked carbo-beta-amino acid) and (R)-Ama (alpha-aminoxy acid). Extensive NMR (in CDCl(3) solution) and mass spectral (MS) studies show its halide binding capacity, with a special affinity to the chloride ion. At higher concentration it was found to form molecular aggregates as evidenced from transmission electron microscopic and atomic force microscopic analysis, confirming the formation of nanorods.

Design of a "new motif" with beta-amino acids and alpha-aminoxy acids: synthesis of hybrid peptides with 12/10-helix.

Hybrid peptides are prepared from a C-linked carbo-beta-amino acid ester (R-beta-Caa) and an alpha-aminoxy acid (R-Ama) derived from S-lactic acid. Extensive NMR (in CDCl 3 solution), CD, and MD studies on the tetra- and hexapeptides led to identification of robust 12/10-mixed helices. The dipeptide repeat having an R-beta-Caa and an R-Ama thus provides a "new motif" to realize a 12/10-mixed helix, for the first time, in oligomers containing R-Ama.