David I. C. Kells

Physical and biological properties of guinea pig insulin.

Abstract Single component guinea pig insulin was found by sedimentation equilibrium centrifugation to exist in neutral solution as a monomeric species only, even in the presence of zinc ion. This insulin, in contrast to bovine insulin, did not bind zinc ion at pH 7.4. The biological activity of guinea pig insulin, estimated by mouse convulsion assay, was 2.14 I. U. per mg.

A rapid computer analysis for multicomponent DNA reassociation kinetics

Abstract An iterative program, Gaushaus, has been adapted to analyze complex DNA reassociation kinetics. With valid experimental data, rapid convergence to a solution is always achieved by this program even when the starting parameters are grossly in error. The output of the program also includes useful statistical information.

Non-covalent interactions between heavy and light chains of immunoglobulin G: role of light chain variable-region subgroup.

Abstract Previous studies have shown that the forward rate constants governing the non-covalent association of heavy and light chains of different IgG myeloma proteins vary considerably. In the present study rate constants, absorption difference spectra enthalpies associated with recombination have been determined using kappa chain of known variable-region subgroup specificity. The basic experimental approach was to allow a single species by γ chain to react reparately with several kappa chains belonging either to the κIII subgroup. The rate constant varied by two orders of magnitude but there was no evidence that this variability was related to subgroup specificity. There was as much variation within a subgroup as between subgroups. A correlation was noted, however, between the rate constants and the species of heavy chain used in the recombination reactions. The shape and magnitude of the difference spectra generated upon subunit association were also variable but again this could not be correlated with subgroup specificity. Variations in enthalpies of association were less striking but there were some indications that values for δH depended on the heavy chain used. Only for one of the heavy chains used was there evidence to indicate that the preferential recombination of autologous subunits observed in equilibrium systems arises because autologous subunits associate more rapidly than heterologous chains. The data presented indicate that sequence variations in either the hypervariable regions, or the framework within a subgroup, play an important role in subunit association.

A method for eliminating Rayleigh scattering from fluorescence spectra

A numerical method is described for the elimination of Rayleigh scattering from protein fluorescence emission spectra. The method is based upon the observation that Rayleigh scattering is symmetrical about a wavelength at or near the wavelength of excitation. It works best when an automated, computer-based approach can be applied to spectra collected on a data-logging device, although manual correction of chart-recorded spectra is also possible.

Sedimentation velocity studies on microgram quantities of rat intestinal goblet cell mucin

Abstract A procedure is outlined by which sedimentation analyses of small quantities of mucin glycoproteins can be performed. Rat intestinal goblet cell mucin was stained with periodic acid-Schiff reagent to permit detection by light absorption at 555 nm. PAS treatment resulted in chemical modification of sialic acid and 55% of fucose residues in the mucin. No other chemical or physical alterations were detected. The stained mucus was subjected to band ultracentrifugation using D2O-containing solvents. Sedimentation was monitored by scanning at 555 nm. Results compared favorably with those reported earlier for conventional boundary ultracentrifugation of intact goblet cell mucin. Because of the low concentrations of mucin used in band ultracentrifugation (0.2–1.5 μg protein/ml), S20,w values are comparable to sedimentation coefficients at zero concentration (So values), determined by conventional means.