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 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.
Asano
Atsushi
A
Department of Applied Chemistry, The National Defense Academy, Yokosuka 239-8686, Japan.
Sullivan
Chrissy M
CM
Yanagisawa
Akira
A
Kimoto
Hiroki
H
Kurotsu
Takuzo
T
D001704:Biopolymers / Q000737:chemistry*; D002104:Cadmium / Q000737:chemistry*; D002942:Circular Dichroism; D003035:Cobalt / Q000737:chemistry*; D018698:Glutamic Acid / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D011048:Polarography / Q000379:methods*; D017433:Protein Structure, Secondary
D001704:Biopolymers; D002104:Cadmium; D003035:Cobalt; D018698:Glutamic Acid