辐射引起的自旋从脱氧核糖核酸(DNA)及胸苷酸(TMP)向没食子酸丙酯转移

本文用小牛胸腺DNA、没食子酸丙酯(PG)和它们的5种分子混合物(PG含量为1—20％)在真空及296°K用γ射线辐照。根据ESR谱形及自由基微波饱和特性,可推断辐射引起的自旋能从DNA向PG转移。PG的自旋产率比其单独辐照时高出2—3个数量级。在自旋转移比率与之间发现有良好的线性关系(r为核苷酸对PG的克分子比率)。在77°K测定说明,此种自旋转移是由于氢转移机制。作者还证实从γ射线辐照的热变性DNA或TMP向PG的自旋转移,并讨论了有关机制。     

乌骨鸡黑素的元素组成与自由基状态初探

乌骨鸡(Gallina lanigera),又名白绒毛鸡,为我国特产的药用鸡种.远在唐代即知乌骨鸡能治风湿等病,明代李时珍在《本草纲目》中亦记载其药效.乌骨鸡的皮肤、肌肉、骨膜及内脏(除心、肝及肺外)中含有大量黑素,但其化学性质迄未鉴定.我们推测可利用黑素的自由基状态来探索黑素的理化性质及其与结构和功能的关系.Commoner 等于1954年最先发现在含黑素的组织(蛙卵)中自由基含量很     

四种哌啶系氮氧自由基的ESR特性研究——固态特性、溶液中的浓度效应和溶剂效应

本文研究四种哌啶系氮氧自由基在固态与在溶液中的ESR特性.它们在固态均显示单峰波谱,而在浓度小于1×10~(-2)M的溶液中则显示三峰波谱.观察并比较溶液中的自由基浓度、溶剂的极性和粘度对ESR波谱五种参数的影响。在超精细分裂常数 A_N与溶剂极性参数 Kosower Z值之间得出线性关系.实验数据表明,自由基的旋转相关时间τ亦与溶剂粘度η成线性关系.并发现高场峰的相对高度与η成反比.对氮氧自由基的这些ESR特性作了讨论。     

STUDIES ON THE ESR CHARACTERISTICS OF FOUR PIPERIDINE NITROXYL RADICALS——CHARACTERISTICS IN THE SOLID STATE,CONCENTRATION EFFECTS AND SOLVENT EFFECTS IN SOLUTIONS

The ESR characteristics are studied for four piperidine nitroxyl radicals in the solidstate and in solutions. They all exhibited singlet ESR spectra in the solid state, but tripletspectra in solutions at a concentration lower than 1×10~(-2)M. The effects of the free radi-eal coneentration and the polarity trod the viscosity of solvents were observed and comparedon five ESR spectral parameters. Linear correlations could be found between the hyperfinesplitting constant A_N and the solvent polarity parameter, namely, Kosower Z value, Ex-perimental data showed also linear relations of the rotational correlation time τ of free rad-icals with the solvent viscosity, η. We have further found that the relative height of thehigh-field peak varied inversely with η. These ESR characteristics of nitroxyl radicals arediscussed.     

TRANSFER OF RADIATION-INDUCED SPINS FROM DEOXYRIBONUCLEIC AND TH

When calf thymus deoxyribonucleic acid (DNA), propyl gallate (PG) and their five mo-ecular mixtures (with PG content of 1, 2, 5, 10 and 20%) are irradiated with γ-rays indry state in vacuum at 296°K, the ESR spectra of all molecular mixtures differ strikinglyfrom those of DNA, but bear a close resemblance to those of PG. The spin yield in the PGcontained in these mixtures is two to three orders of magnitude higher than that in the caseof PG irradiated separately. Furthermore, on the basis of the relative saturation characteris-tics of ESR spectra, these molecular mixtures behave more like PG than like DNA. It maybe inferred that the radiation-induced spins could be transferred from DNA to PG. Withr representing the molar ratio of nucleotides to PG, we have found a good linear correlationbetween the transfer ratio (TR) and r~(1/2). One PG molecule could protect at least 68 nu-eleotides in the duplex DNA chain, and thereby the minimal range of spin transfer is estimat-ed at 115 ?. Results obtained from irradiation at 77°K show that PG exerts no protectiveeffect on DNA, so DNA sustains an irreversible damage. It is thought that the spin transferfrom DNA to PG is exclusively due to a hydrogen transfer mechanism. We have also demons-trated the transfer of radiation-induced spins from both thermally denatured DNA and TMPto PG. The former process can be ascribed primarily to the hydrogen transfer mechanism,Whereas the latter, as in the case of native DNA, exclusively to this mechanism.     

用电子自旋共振对自旋数的简易测定方法

关于电子自旋共振(ESR)定量测定方法虽已有专文论述,但在具体应用的许多细节方面仍有值得改进之必要。本文报导一种简易测定方法,从两个方面分别说明于下。一、图解双积分法的简化 ESR定量测定的主要依据是试样中自旋数与微波吸收曲线下所包的面积成正比。但由于常用的ESR波谱仪采用高频调场的关系,记录的不是微波吸收曲线本身,而是它对磁场强度的一次微商函数。因此必须对后者进行双积分才能算出吸收曲线下所包的面积。在缺乏积分仪和电子计算机的条件下,图解双积分法是切实可行的。     

四种哌啶系氮氧自由基的ESR特性研究Ⅲ.pH效应和去氧效应

本文研究不同PH和去氧对数种哌啶系氮氧自由基在溶液中的ESR波谱的影响。其中两种水溶性自由基在PH为3-12的缓冲液内,有较高稳定性。对固态自由基,去氧并不影响其ESR特性,但在自由基溶液中,溶剂极性对如何显现去氧效应起着决定性的作用。在低极性溶液中,去氧使波谱显著变窄及增强,¹⁴N超精细三峰分裂的完善程度大大提高;而在水溶液中,去氧效应甚小。