N-Phospho-α-Amino Acids and Co-Evolution of Nucleic Acid and Protein

N-phospho-α -amino acids obtainable from aqueous condition were different from their corresponding β -analogues intrinsically. As the self-reproduction unites, N-phospho-α -amino acids were capable to produce non-random oligopeptides. As the phosphoryl donor, they were able to phosphorylate the nucleosides much faster than the deoxynucleosides.     

Weibull分布定时截尾试验数据情形下的数据填充算法

利用处理非随机删失数据的矩不变准则及相应算法,本文针对Weibuu分布相同定时截尾型试验数据,通过控制算法中填充数据的分位概率,证明了通过迭代算法所得到的参数估计的相合性.进一步,通过对参数空间进行压缩,使得改进后的收敛算法所得到的参数估计同时具有相合性及不变性.作为本文算法的一个应用,我们还研究了利用填充后的虚拟完全样本构造可靠度的区间估计.最后,通过模拟计算验证了该算法具有较好的计算稳定性和可操作性.     

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??In this paper, precise large deviations of nonnegative, non-identical distributions and negatively associated random variables are investigated. Under certain conditions, the lower bound of the precise large deviations for the non-random sum is solved and the uniformly asymptotic results for the corresponding random sum are obtained. At the same time, we deeply discussed the compound renewal risk model, in which we found that the compound renewal risk model can be equivalent to renewal risk model under certain conditions. The relative research results of precise large deviations are applied to the more practical compound renewal risk model, and the theoretical and practical values are verified. In addition, this paper also shows that the impact of this dependency relationship between random variables to precise large deviations of the final result is not significant.     

重离子诱导的质粒DNA双链断裂分布研究

利用能量为7．2MeV／u氖离子束辐照体外质粒DNA:pUC18，采用恒场凝胶电泳结合多功能荧光成像系统研究了pUC18双链断裂片段的分布。证实了双链断裂片段分布的非随机性，结果还发现DNA断裂后片段的交联现象，而且交联片段的分布也是非随机的。DNA is considered to be the most important and sensitive target in biological systems. In addition to the base damage, DNA strand breaks are the major lesion in the genome due to exposure to ionizing radiation. Mutation can be introduced to DNA as a result of enzymatic processing of DNA lesions or post irradiation replication. However, the mechanisms of radiation induced mutations are not well clarified at the molecular level. To study the effect on the simple plasmid DNA of heavy ion is even predominant or more feasible. Plasmid pUC18 DNA was prepared and irradiated by neon beam (7.199 MeV/u). The fragment distributions were determined by quantifying the ethidium bromide fluorescence. It can be seen that the shape of the intensity distributions is vastly different for the used radiation Dose. The distribution produced shows an excess of fragments particularly in 3 000 and 10 000 Gy the size range between 20—40 kbp and 20—50 bp. This clustering of double stranded fragments might be influenced by the higher order chromatin structure of genomic DNA. If so, DNA loop structures could correspond to the size range for which we observed DSB clustering. Further studies aim at elucidating the heterogeneity of DSB induction within the genome and investigate the influence of chromatin structure on the non random fragment distribution.