A light-scattering study of the effect of calcium chloride on the molecular weight of busycon hemocyanin

✍ Scribed by M.Constance Loeffler; Shian-shi Su; Norman C. Li; Edward F. Casassa

• Book ID: 104106000
• Publisher: Elsevier Science
• Year: 1978
• Weight: 363 KB
• Volume: 8
• Category: Article
• ISSN: 0006-3061
• DOI: 10.1016/s0006-3061(00)80239-2

✦ Synopsis

Solutions of &qcon

cunaliculutum have been studied by light scattering. In 0.05 M Trizma buffer + 0.1 M NaCl at pli 7.0 at l@, the. weight-average molecular weight is 8.9 X 106. In the presence of added Car& (0.02 Ml, the molecular weight of the protein increases to 10.7 X 106, and the second virial coefflclent is reduced. At pH 9.95. the moIecular weights with and without 0.02 h4 Carla, are 3.7 X lo6 and 1.3 X 106, respectively; and the effect of Ca++ in reducing the second virial coefficient is much greater than at pH 7.0. These results can be understood on the basis that at pH 7.0, Ca++ increases the association of hemocyanin. by binding and intermolecular linkage through the carboxyl groups of protein side chains. At pH 9.95, amino groups are deprotonated and therefore also become available for Ca++ binding. The relative effect of Ca++ _ m enhancing the association of hemocyanin therefore becomes greater at the higher pH.

'At pH 9% some of the Ca* _ effective concentration of Ca-1s chelated to the glycine buffer component. Thus the producing aggregation is less than 0.02M.