Huili Chen

Structure-specific binding of [Co(phen)2(HPIP)]3+to a DNA duplex containing sheared G:A mismatch base pairs

The binding of a Co(III) complex to the decanucleotide d(CCGAATGAGG)(2) containing two pairs of G:A mismatches was studied by 2D-NMR, UV absorption, and molecular modeling. NMR investigations indicate that racemic [Co(phen)(2)(HPIP)]Cl(3) [HPIP=2-(2-hydroxyphenyl) imidazo [4,5-f][1,10] phenanthroline] binds the decanucleotide by intercalation: the HPIP ligand selectively inserts between the stacked bases from the minor groove at the terminal regions and from the major groove at the sheared region. Further, molecular modeling revealed that the recognition shows strong enantioselectivity: the Lambda-isomer preferentially intercalates into the T(6)G(7):A(5)A(4) region from the DNA major groove, while Delta-isomer favors the terminal C(1)C(2):G(10)G(9) region and intercalates from the minor groove. Detailed energy analysis suggests that the steric interaction, especially the electrostatic effect, is the primary determinants of the recognition event. Melting experiments indicate that binding stabilizes the DNA duplex and increases the melting temperature by 9.5 degrees C. The intrinsic binding constant of the complex to the mismatched duplex was determined to be 3.5x105M(-1).

Study of the coordination of amino acids with metals using [trans-en2Os(η2-H2)L]2+ as a 1H NMR probe

This is a study of the interaction of 23 kinds of amino acids, peptides and their analogues with Os((II)) at different pD values. Experiments show that in acidic conditions, the carboxyl group in amino acids can coordinate with Os((II)), and there exists H-D coupling of the dihydrogen of the probe with D2O in strongly acidic conditions, N does not coordinate with Os((II)); In alkaline conditions, the carboxyl group can coordinate with Os, and the coordinating species have trans and cis isomers, and the trans isomer can convert to cis with time; N of -NH2- in alpha-amino group can coordinate with Os((II)) while that in gamma-amino-n-butyric acid cannot do that. Since the target of some anti tumor agents are nucleic acids and proteins, we demonstrate a competitive mode to study how the anti tumor complex Me2SnCl2 binds to amino acid Ala, and the minimum binding amount and formation constant of the metal anti tumor metal complexes binding with amino acid are also obtained.