Dawn Arnab, Nandi Arun K
Polymer Science Unit, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032 India.
Langmuir. 2006 Mar 28;22(7):3273-9. doi: 10.1021/la052536+.
The DNA-poly(o-methoxyaniline) (POMA) hybrid is prepared by mixing aqueous solutions of POMA [emeraldine salt (ES), doping level [Cl]/[N] = 0.52] and sodium salt of DNA (Na-DNA) and is then freeze-dried after 4 days. Three different compositions (WDNA = 0.25, 0.5, and 0.75, WDNA is the weight fraction of DNA) of the hybrids are prepared. The SEM pictures show a gradation in morphology; for example, for WDNA = 0.75, fibrils are present but, at lower DNA concentration, a fibrillar network structure of the hybrid is observed. The circular dichroism (CD) spectra of the hybrid solutions indicate unchanged DNA conformation and WAXS patterns indicate intact crystal structure of DNA in the hybrid. The UV-vis spectra suggest no denaturation of DNA during the blending process. The UV-vis spectra of the hybrids in aqueous medium show a gradual red shift of the pi band to polaron band transition with time. The plots of these wavelengths with time are sigmoidal, indicating the autocatalytic nature of the process. With an increase in the temperature, the rate of the red shift of the above peak is faster. Arrhenius analysis of the rate (1/tau700 where tau700 is the time required to reach the absorption maximum at the wavelength 700 nm) yields straight lines for the three hybrid compositions with activation energy values of 13-15 kcal/mol. These values are almost equal to the activation energy values of conformational transition of other polymers, supporting the red shift in UV-vis spectra occurs from conformational transition. DNA offers a surface where POMA gets adsorbed and the stable conformational transition resulting in the uncoiling of the POMA chain occurs through repulsive interaction among bound radical cations of POMA (ES) on the DNA surface. The conductivity of the hybrids is on the order of 10(-6) S/cm, and the I-V characteristic curves indicate the semiconducting nature of the hybrids.
通过将聚（邻甲氧基苯胺）（POMA）[翠绿亚胺盐（ES），掺杂水平[Cl]/[N]=0.52]的水溶液与DNA钠盐（Na-DNA）的水溶液混合来制备DNA-POMA杂化物，然后在4天后进行冷冻干燥。制备了三种不同组成（WDNA = 0.25、0.5和0.75，WDNA是DNA的重量分数）的杂化物。扫描电子显微镜（SEM）图片显示出形态上的渐变；例如，对于WDNA = 0.75，存在纤维，但在较低的DNA浓度下，观察到杂化物的纤维状网络结构。杂化溶液的圆二色性（CD）光谱表明DNA构象未改变，广角X射线散射（WAXS）图谱表明杂化物中DNA的晶体结构完整。紫外可见光谱表明在混合过程中DNA未发生变性。杂化物在水性介质中的紫外可见光谱显示π带至极化子带跃迁随时间逐渐发生红移。这些波长随时间的曲线呈S形，表明该过程具有自催化性质。随着温度升高，上述峰的红移速率更快。对速率进行阿仑尼乌斯分析（1/τ700，其中τ700是在波长700nm处达到吸收最大值所需的时间），得到三种杂化组成的直线，活化能值为13 - 15 kcal/mol。这些值几乎等于其他聚合物构象转变的活化能值，支持紫外可见光谱中的红移是由构象转变引起的。DNA提供了一个表面，POMA吸附在其上，并且通过DNA表面上POMA（ES）的结合自由基阳离子之间的排斥相互作用，发生导致POMA链解缠的稳定构象转变。杂化物的电导率约为10^(-6) S/cm，I-V特性曲线表明杂化物具有半导体性质。
