Studies on the Calcium-Protein Relationship With the Aid of the Ultracentrifuge

Studies on Adenosine Triphosphate Transphosphorylases. IV. Enzyme-Substrate Interactions*

“…B. Sedimentation Gradient Procedure.-The technique used was essentially that of Chanutin et at. (1942) as applied by Velick (Velick et al, 1953;Hayes and Velick, 1954).…”

Binding of cations to caseins. Site binding, Donnan binding, and system characteristics

“…Little information on ion binding is available. The interactions of mixtures of caseins, with monovalent cations (Carr and Topol, 1950;Carr and Engelstad, 1958) and with divalent cations (Chanutin et al, 1942;Zittle et al, 1958) have been studied, but studies of components are limited to the data of Ho and Waugh (1965a) on the binding of sodium and potassium to as-casein. For divalent cations, Ho and Waugh (1965b) report that the organic phosphate groups on ,-casein appear to be the strongest binding sites for calcium and Dickson and Perkins (1969) report that the relative order of binding constants to ,-, ß-, and «-caseins is Ca2+ > Ba2+ > Sr2+, and that the relative order of binding capacities is as > ß > .…”

Ultracentrifugation Studies with Absorption Optics. V. Analysis of Interacting Systems Involving Macromolecules and Small Molecules*

“…In such experiments the fractional amount of dye in the free form and, hence, the fraction bound can be calculated directly from patterns such as those in Figure 6. These procedures utilizing the absorption optical system in the ultracentrifuge are directly analogous to those employed by Chanutin et al (1942), Velick et al (1953, Velick (1954), andVelick (1954) for the evaluation of binding data from samples removed from tubes in a preparative centrifuge.…”

“…However the number of studies of this type has been very limited. Chanutin et al (1942), for example, employed a preparative centrifuge for determinations of the binding of calcium ions to casein and serum proteins. In these experiments the contents of the tubes after a long period of highspeed centrifugation were separated into a series of fractions corresponding to levels at different distances from the axis of rotation.…”