The time course of synthesis and breakdown of various macromolecules has been compared for sporulating ( a /α) and nonsporulating ( a/a and α/α) yeast cells transferred to potassium acetate sporulation medium. Both types of cells incorporate label into ribonucleic acid and protein. The gel electrophoresis patterns of proteins synthesized in sporulation medium are identical for sporulating and nonsporulating diploids; both are different from electropherograms of vegetative cells. Sporulating and nonsporulating strains differ with respect to deoxyribonucleic acid synthesis; no deoxyribonucleic acid is synthesized in the latter case, whereas the deoxyribonucleic acid complement is doubled in the former. Glycogen breakdown occurs only in sporulating strains. Breakdown of preexisting vegetative ribonucleic acid and protein molecules occurs much more extensively in sporulating than in nonsporulating cells. A timetable of these data is presented.

Little is known of the relationships that may exist among the three principal functionalities of glycoproteins. Orosomucoids of closely defined N-acetylneuraminic acid content were examined for evidence of influence of N-acetylneuraminic acid content on the physical properties of the glycoprotein. Fluorescence spectroscopy gave no indication of conformational change in the protein core upon desialylation. Small changes in the chromatographic partition coefficient, sigma, and thermal stability, Td, are interpreted to reflect loss of water of hydration and increased glycan stem-protein interaction without a major repositioning of the chains. Ligand-binding measurements indicate no alteration in the hydrophobic binding domain and a possible interaction between chlorpromazine and N-acetylneuraminic acid. All changes seen are progressive and occur through a region where changes in biological activity are not found. It is suggested that the dependence of biological activity on N-acetylneuraminic acid content in orosomucoid reflects, not coupled changes in protein conformation, but a charge-density-related interaction such that, below a contribution of four or five N-acetylneuraminic acid residues, activity is modified.

The fluorescence behaviour of human orosomucoid was investigated. The intrinsic fluorescence was more accessible to acrylamide than to the slightly larger succinimide, indicating limited accessibility to part of the tryptophan population. Although I- showed almost no quenching, that of Cs+ was enhanced, and suggested a region of negative charge proximal to an emitting tryptophan residue. Removal of more than 90% of sialic acid from the glycan chains led to no change in the Cs+, I-, succinimide or acrylamide quenching, indicating that the negatively charged region originates with the protein core. Quenching as a function of pH and temperature supported this view. The binding of chlorpromazine monitored by fluorescence quenching, in the presence and in the absence of the small quenching probes (above), led to a model of its binding domain on orosomucoid that includes two tryptophan residues relatively shielded from the bulk solvent, with the third tryptophan residue being on the periphery of the domain, or affected allotopically and near the negatively charged field.

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