help button home button Biophys. J.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS

Biophysical Journal 8: 1458-1474 (1968)
© 1968 the Biophysical Society

This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Tang, T.
Right arrow Articles by Grecz, N.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Tang, T.
Right arrow Articles by Grecz, N.

Mixed Chelates of Ca(II)-Pyridine-2,6-Dicarboxylate with Some Amino Acids Related to Bacterial Spores

T. Tang, K. S. Rajan and N. Grecz

ABSTRACT

The high resistance of bacterial spores to heat has been repeatedly postulated to be due to stabilization of spore biopolymers by metal chelate compounds. Binding of calcium dipicolinic acid (Ca(II)-DPA) with spore proteins and amino acids has been discussed in the literature, but equilibrium data are generally lacking. By means of potentiometric pH titrations at 25°C and an ionic strength of 1.0 (KNO3), the formation of Ca(II)-DPA (1:1 and 1:2) chelates and the interactions of Ca(II)-DPA chelate with a mole of each of three typical amino acids viz., cysteine, alanine, and glycine has been investigated. Analysis of the potentiometric data indicates that calcium and DPA forms 1:1 and 1:2 chelates with log KML1 = 4.39 ± 0.01 and log KML2 = 2.25 ± 0.01. In the presence of an equimolar amount of each of the amino acids under consideration, the Ca(II)-DPA chelate forms mixed ligand (ternary) chelate yielding the following stepwise stability constants: log K1 = 4.17 ± 0.01, log K2 = 0.78 ± 0.01 for cysteine, log K1 = 4.06 ± 0.01, log K2 = 0.65 ± 0.01 for alanine, and log K1 = 4.30 ± 0.02, log K2 = 0.11 ± 0.01 for glycine. Methods for calculating the stability constants of the mixed ligand system have been developed. On the basis of the potentiometric equilibrium data, possible structures for the various calcium chelate species are discussed. The data suggest that the differences in heat resistance of various strains of bacterial spores may conceivably be related to the differences in composition and stability of coordination complexes in the spore.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Copyright © 1968 by the Biophysical Society.