Lipids in hydatid fluid collected from lungs and livers of sheep and man.

Hydatid fluid collected from the lungs and livers of sheep and humans was analysed for protein and lipid composition. There were no marked differences in the composition of these parameters and the major lipids were triglycerides and diglycerides. The phospholipids, which formed the minor fraction, were mainly phosphatidyl choline and phosphatidyl inositol. Cholesterol present was in the free form.

Effect of succinylation (3-carboxypropionylation) on the conformation and immunological activity of ovalbumin.

The epsilon-amino groups of ovalbumin were modified with succinic anhydride; as many as 16 lysine residues were succinylated (3-carboxypropionylated). The five succinylated derivatives thus prepared were homogeneous with respect to the extent of chemical modification as shown by electrophoretic and immunological data. Succinylation of the amino groups altered electrophoretic mobility and isoionic pH of ovalbumin in the expected direction. U.v.-absorption and fluorescence spectra suggested changes in the microenvironment of the chromophores in the modified proteins. The difference-spectral results showed greater exposure of tyrosine and tryptophan residues in the succinylated ovalbumin. Increase in susceptibility to tryptic digestion, Stokes radius and intrinsic viscosity of native ovalbumin, which was observed on successive increase in the chemical modification, demonstrated a conformational change that was proportional to the extent of modification. The loss of immunological reactivity caused by chemical modification also indicated a conformational change in succinylated ovalbumin. The fact that the intrinsic viscosity of maximally modified ovalbumin was less than one-third of that for the completely denatured protein in 6M-guanidinium chloride suggested that the modified protein contained significant residual native structure. The latter presumably accommodates some antigenic determinants accounting for 37% residual immunological activity observed with maximally succinylated ovalbumin.

Acetylation of amino groups and its effect on the conformation and immunological activity of obalbumin.

A procedure is described for the specific acetylation of the lysine residues of ovalbumin. Six acetylated ovalbumins varying in the degree of modification from 21 to 98% were prepared and were found to be homogeneous by polyacrylamide gel electrophoresis, immunodiffusion, and immunoelectrophresis. As expected, the anodic movement of ovalbumin increased and the isoionic point shifted to lower pH values with progressive acetylation of the protein. Measurements on ultraviolet absorption, fluorescence, tryptic digestion, intrinsic viscosity, gel filtration behavior, and immunological reactivity demonstrated that the native folded conformation of ovalbumin was appreciably altered by acetylation. However, even the maximally modified ovalbumin retained considerable residual structure consisting of regions of ordered structure containing antigenic determinants.