The application of circular dichroism spectroscopy for the determination of metal ion speciation and coordination modes of peptide complexes

摘要

Copper(II) and nickel(II) complexes of the tripeptides containing methionyl residues (GlyGyMet, GlyMetGly, MetGlyGly, MetMetAla, MetGlyMet and MetMetMet) and palladium(II) complexes of GlyMet, MetGly, GlyMetGly and GlyGlyMet were studied by CD spectroscopic measurements. Complex formation reactions between copper(II), nickel(II) and tripeptides were very similar to each other, [MH-2L](-) being the major species in alkaline solutions. CD spectroscopy, however, was a very sensitive tool for the elucidation of small structural differences among peptide complexes, including the weak axial or equatorial coordinations of thioether residues. The significant differences in the spectral parameters of the species [CuL](+), [CuH-1L] and [CuH-2L](-) made it also possible to calculate the stability constants and metal ion speciation from CD measurements. (C) 2002 Elsevier Science Ltd. All rights reserved. [References: 31]