Sypherd, Paul S. (University of California, San Diego). Accumulation of ribonucleoprotein particles in a relaxed mutant of Escherichia coli. J. Bacteriol. 90:403-410. 1965.-The synthesis of ribonucleic acid during amino acid deprivation of a "relaxed" mutant was investigated. Aspects of the stability of the macromolecular ribonucleic acid (RNA) were studied, and standard conditions were established to allow maximal recovery of the larger RNA's (i.e., 16S and 23S). These RNA's, representing 75% of the total RNA produced during starvation, were present in particles with nominal S-values of 20, 30, and 43. The particles are extremely sensitive to nuclease action, being completely destroyed in the presence of 2 mug/ml of pancreatic ribonuclease at 15 C for 30 min. The particles containing the bulk of the RNA were shown to be ribonucleoprotein, consisting of 26 to 28% protein by weight. It was shown that no mature 70S ribosomes were formed during the accumulation of the lighter, protein-deficient particles.