Contribution of light scattering to the circular dichroism of deoxyribonucleic acid films, deoxyribonucleic acid-polylysine complexes, and deoxyribonucleic acid particles in ethanolic buffers.
Contribution of light scattering to the circular dichroism of deoxyribonucleic acid films, deoxyribonucleic acid-polylysine complexes, and deoxyribonucleic acid particles in ethanolic buffers.
复制标题
光散射对乙醇缓冲液中脱氧核糖核酸膜、脱氧核糖核酸-聚赖氨酸复合物和脱氧核糖核酸颗粒圆二色性的贡献。
作者：
M. Maestre;C. Reich
通过使用新的测量技术，研究了具有扭曲结构的DNA膜、DNA-聚赖氨酸复合物和浓缩的DNA聚集体在确定盐浓度的乙醇缓冲液中的散射对圆二色性（CD）的贡献。这些技术包括荧光比色皿、荧光检测圆二色性（FDCD）方法、反向散射捕获装置和光束安装测角仪检测器。实验测量的结果是，可以制备在尖锐的特定波长处具有非常大的椭圆率或CD的DNA膜。这些椭圆的符号与扭转的旋向有关，右旋扭转产生大的正旋转，左旋扭转产生负旋转。胶片显示出与光的相互作用最小的波节角。这两种膜，DNA-聚赖氨酸颗粒和DNA-EtOH凝聚物的散射图案，表明，主要的相互作用是光散射产生的共振现象类似于产生在双折射液晶和扭曲双折射液晶。从这个结果中，我们提出，所谓的PSI型CD光谱是一个并排包装的DNA分子与长程扭曲秩序，其螺旋参数匹配的螺旋参数的圆偏振光在特定的共振或临界波长的表现。应用布拉格定律对双折射液晶的研究，给出了长程有序结构的周期性。
The contribution of scattering to the circular dichroism (CD) of DNA films with twisted structures, DNA-polylysine complexes, and condensed DNA aggregates in ethanolic buffers of defined salt concentrations has been studied by the use of novel measuring techniques. These techniques include fluorscat cuvettes, fluorescence-detected circular dichroism (FDCD) methods, backscattering capturing devices, and beam-mounted goniometer detectors. The result of the experimental measurement is that DNA films can be made which have very large ellipticities or CD at sharp specific wavelengths. The sign of these ellipticities is related to the handedness of the twists, with a right-handed twist producing large positive rotations and a left-handed one producing negative rotations. The film show nodal angles at which the interaction with light is minimal. The scattering patterns of both films, DNA-polylysine particles and DNA-EtOH condensates, show that the main interaction is light scattering produced by a resonance phenomenon similar to that produced in cholesteric liquid crystals and twisted-nematic liquid crystals. From this result we propose that the so-called psi-type CD spectrum is a manifestation of a side-by-side packing of DNA molecules with a long-range twisting order whose helical parameters match the helical parameter of circularly polarized light at specific resonance or critical wavelengths. Application of the Bragg law for cholesteric liquid crystals gives the periodicity of the long-range ordered structures.