Borquez Eduardo, Cleaves H James, Lazcano Antonio, Miller Stanley L
Department of Chemistry, and Biochemistry, University of California, San Diego, La Jolla, CA, USA.
Orig Life Evol Biosph. 2005 Apr;35(2):79-90. doi: 10.1007/s11084-005-5945-9.
The polymerization of concentrated NH4CN solutions has been studied at various temperatures and ammonia concentrations. The products of the oligomerization of ammonium cyanide include adenine and guanine, as well as trace amounts of 2,6-diaminopurine. Our results indicate that the adenine yield is not strongly dependent on temperature. Guanine is produced in lower yield. The original studies by Oró and Kimball (1961) showed that the 6 N HCl hydrolysis of the NH4CN polymerization supernatant greatly increased the adenine yield. However, this hydrolysis also decomposes adenine and other purines. Therefore, we have measured the yields from an NH4CN polymerization as a function of hydrolysis time, and found that shorter hydrolytic periods give higher yields of adenine. We have also investigated the hydrolysis of the supernatant at pH 8, which is a more reasonable model of primitive oceanic conditions, and found that the adenine yield is comparable to that obtained with acid hydrolysis (approximately 0.1%). The yield of adenine does not decline at longer hydrolysis times because of the greater stability of adenine at pH 8. The insoluble black polymer formed from NH4CN has been analyzed by both acid and neutral hydrolysis. In both cases adenine yields of approximately 0.05% were obtained. This suggests that the polymer may have been as important a prebiotic source of purines as the usually analyzed supernatant.
已在不同温度和氨浓度下研究了浓NH₄CN溶液的聚合反应。氰化铵低聚反应的产物包括腺嘌呤和鸟嘌呤，以及痕量的2,6 - 二氨基嘌呤。我们的结果表明，腺嘌呤产率对温度的依赖性不强。鸟嘌呤的产率较低。奥罗（Oró）和金博尔（Kimball）（1961年）的原始研究表明，NH₄CN聚合上清液的6N HCl水解大大提高了腺嘌呤产率。然而，这种水解也会分解腺嘌呤和其他嘌呤。因此，我们测量了NH₄CN聚合反应中腺嘌呤产率随水解时间的变化，发现较短的水解时间能得到更高的腺嘌呤产率。我们还研究了在pH 8条件下上清液的水解情况，这是更接近原始海洋条件的合理模型，发现腺嘌呤产率与酸水解得到的产率相当（约0.1%）。由于腺嘌呤在pH 8时稳定性更高，较长水解时间下腺嘌呤产率不会下降。由NH₄CN形成的不溶性黑色聚合物已通过酸水解和中性水解进行了分析。在这两种情况下，腺嘌呤产率均约为0.05%。这表明该聚合物可能是嘌呤的一种与通常分析的上清液同样重要的益生元前体来源。
