Polarographic study on poly alpha-L-glutamic acid-Cd2+,Co2+ complexes in the helix-coil pH region

Interactions between poly alpha- L-glutamic acid (PGA) and metal ions Cd(2+), Co(2+) were studied by direct current polarography. The diffusion currents of these ions decreased sharply in the presence of PGA in the pH region from 5.0 through neutral. A corresponding increase in the helix content of...

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Bibliographic Details
Published in:Analytical and bioanalytical chemistry 2002-12, Vol.374 (7-8), p.1250-1255
Main Authors: Asano, Atsushi, Sullivan, Chrissy M, Yanagisawa, Akira, Kimoto, Hiroki, Kurotsu, Takuzo
Format: Article
Language:English
Subjects:
Biopolymers - chemistry
Cadmium
Cadmium - chemistry
Carbon dioxide
Circular Dichroism
Cobalt
Cobalt - chemistry
Diffusion
Direct current
Glutamic acid
Glutamic Acid - chemistry
Hydrogen-Ion Concentration
Metal ions
Parameter sensitivity
pH effects
Polarography
Polarography - methods
Polymers
Protein Structure, Secondary
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Summary:Interactions between poly alpha- L-glutamic acid (PGA) and metal ions Cd(2+), Co(2+) were studied by direct current polarography. The diffusion currents of these ions decreased sharply in the presence of PGA in the pH region from 5.0 through neutral. A corresponding increase in the helix content of the PGA-metal ion complex was revealed by CD measurements on the same solutions. Helix contents determined by polarography were in good agreement with those by CD in the neutral pH region. On the contrary, the decrease of current in lower acidic pH regions was independent of helix formation and suggested that metal ions coordinate to sporadically-dissociated carboxylate groups to cause aggregation of the intra and/or inter polymer chains. The diffusion current of the ions, therefore, is a parameter sensitive to the conformational changes of PGA from acidic through neutral pH region.
ISSN:1618-2642
1618-2650
DOI:10.1007/s00216-002-1613-3