Formation of pyrophosphate, tripolyphosphate, and phosphorylimidazole with the thioester, n, s-diacetyl-cysteamine, as the condensing agent.

Reaction of 0.20M orthophosphate with 0.20M N,S-diacetylcysteamine in 0.40M imidazole at pH 7.0 or 8.0 under drying conditions at 50 degree C for 6 days yields pyrophosphate and tripolyphosphate in the presence and absence of 0.10M divalent metal ion. The efficiency of utilization of N,S-diacetylcysteamine in the formation of pyrophosphate linkages ranges from 3 - 8% under the above conditions. The thioester, N,S-diacetylcysteamine, and imidazole are required for phosphoanhydride formation. Reaction of 0.40M orthophosphate with 0.20M N,S-diacetylcysteamine in 0.40M orthophosphate with 0.20M N,S-diacetylcysteamine in 0.40M imidazole at ambient temperature for 6 days yields phosphorylimidazole in the absence or presence of 0.50M MgCl2. Phosphorylimidazole and pyrophosphate are formed in the presence of 0.05M CaCl2; pyrophosphate and tripolyphosphate are formed with 0.15M CaCl2. The efficiency of utilization of N,S-diacetylcysteamine in the formation of pyrophosphate linkages is roughly 7% at 6 days of reaction with 0.15M CaCl2. The thioester, N,S-diacetylcysteamine and imidazole are required for the formation of phosphoanhydrides. The significance of these reactions to molecular evolution is discussed.