Evolution. Nuclear Overhauser enhancement NMR studies of the hydrogen-bonded complex between cytosine and serine-containing peptides are currently underway to definitively establish the proper formulation of the hydrogen-bonded structure. Protein Synthesis. Experimental dissection and elucidation of the mechanism of the reductive activation of yeast valyl-tRNA synthetase is continuing. A lipophilic substance found in 15-fold higher concentrations in rapidly growing than in resting yeast cells has been identified as a dioctylphthalate. The possibility of its having an activator role in protein biosynthesis is being studied.