BARNHART B J
J Bacteriol. 1965 May;89(5):1271-9. doi: 10.1128/jb.89.5.1271-1279.1965.
Barnhart, Benjamin J. (Johns Hopkins University School of Hygiene and Public Health, Baltimore, Md.). Residual activity of thermally denatured transforming deoxyribonucleic acid from Haemophilus influenzae. J. Bacteriol. 89:1271-1279. 1965.-The level of residual transforming activity of heated deoxyribonucleic acid (DNA) (i.e., 1 to a few per cent of native DNA-transforming activity) was found to be independent of the heating and quenching temperatures and less susceptible than native or renatured DNA to heat inactivation upon prolonged heating above or below the critical melting temperature. Similar dose-response curves were obtained for inactivation by formamide of native and renatured DNA, but the residual-active material was much more resistant. Heating DNA above the T(m) in the presence of 1% formaldehyde resulted in a level of residual activity 4 logs lower than that obtained without formaldehyde. Residual-active material was not inactivated by Escherichia coli phosphodiesterase, but it was susceptible to snake venom phosphodiesterase. A new genetic marker was induced in heated-quenched DNA but not in purified residual-active material following nitrous acid treatment. Residual activity was found to be less susceptible to ultraviolet inactivation and to band at a higher density region in CsCl than native DNA. In conclusion, it is suggested that the residual-active material is a structure formed by intrastrand hydrogen bonding of the separated units of heated-quenched DNA. Such a configuration would result in at least a partially double-stranded structure, which is probably the essential characteristic of the residual-active material endowing it with biological activity.
巴恩哈特，本杰明·J.（约翰斯·霍普金斯大学卫生与公共卫生学院，马里兰州巴尔的摩）。流感嗜血杆菌热变性转化脱氧核糖核酸的残余活性。《细菌学杂志》89:1271 - 1279。1965年。发现加热后的脱氧核糖核酸（DNA）的残余转化活性水平（即天然DNA转化活性的1%至百分之几）与加热和淬火温度无关，并且在高于或低于临界熔解温度的长时间加热下，比天然或复性DNA更不易热失活。天然和复性DNA被甲酰胺灭活时获得了相似的剂量反应曲线，但残余活性物质更具抗性。在1%甲醛存在下将DNA加热至高于T(m)会导致残余活性水平比无甲醛时低4个对数。残余活性物质不被大肠杆菌磷酸二酯酶灭活，但对蛇毒磷酸二酯酶敏感。亚硝酸处理后，在加热淬火的DNA中诱导出了一个新的遗传标记，但在纯化的残余活性物质中未诱导出。发现残余活性比天然DNA更不易被紫外线灭活，并且在氯化铯中在更高密度区域形成条带。总之，有人提出残余活性物质是加热淬火DNA的分离单元通过链内氢键形成的一种结构。这样的构型将导致至少部分双链结构，这可能是赋予残余活性物质生物活性的基本特征。
