Objectives: 1. Preparations of pure, intact chloroplasts of spinach and Euglena gracilis will be isolated by the method of Morgenthaler et al. (Arch. Biochem. Biophys. 1975, in press) in which the organelles are sedimented into a density gradient of colloidal silica. The chloroplasts will be incubated with a mixture of C-14 amino acids; fractionated into outer envelopes, thylakoids, ribosomes, and non-sedimenting materials; and the constituent polypeptides analyzed by SDS-acylamide gel electrophoresis. The mobilities of the polypeptides synthesized autonomously by the chloroplasts will be compared with those of known enzymes and other proteins of the organelles. 2. The "sidedness" of the polypeptides identified in the outer envelopes of chloroplasts will be determined by labeling with DABS (diazobenzene-S35-sulfonic acid).