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The geometries, polarizabilities (αs), and first hyperpolarizabilities (βtot) of a series of green fluorescent protein chromophore coupled diradicals and their corresponding optical isomers were investigated using density functional theory (DFT). The results show that the introductions of the electron donor/acceptor significantly enhance the polarizabilities and have a different influence on the first hyperpolarizabilities. For trans isomers, the βtot values of the studied compounds increase with increasing strength of the electron-withdrawing ability of the substituent, whereas the βtot values decrease significantly with increasing strength of the electron-donating ability of the substituent. For cis isomers, the trends in the changes in the βtot values are the opposite of those for trans isomers on introduction of a donor/acceptor. Significantly, photoisomerization can lead to the different βtot values. The βtot values of cis isomers are smaller than those of trans isomers when electron acceptors are introduced. For example, the βtot value of the cis isomer with the strongest electron acceptor, i.e.,―NO2, is about 1/6 that of the corresponding trans isomer. However, the βtot values of trans isomers are smaller than those of cis isomers when electron donors are introduced. For example, the βtot value of the trans isomer with the strongest electron donor, i.e., ―NH2, is about six times smaller than that of the corresponding cis isomer. As a result, photoisomerization can modulate the molecular nonlinear optical (NLO) responses effectively. 2543 Acta Phys. -Chim. Sin. 2013 Vol.29 1 引 言 近几十年,人们对新型有机非线性光学(NLO) 分子材料进行了大量研究. 这些材料具有较高的 NLO响应和良好的光电特性,引起了理论和实验 工作者的重视.研究发现,共轭链长度、电荷价态、 给受体基团的改变等都可以影响分子的 NLO特 性. 最初人们研究的有机NLO分子为闭壳层体 系, 近年来人们开始关注开壳层体系, 对有机自由 基分子的NLO性质进行理论与实验探讨,以期成为 一种新的NLO材料.在诸多开壳层体系中,氮氧自 由基以其良好的热稳定性、简易的制备方法、灵活 的配位能力以及协同磁效应而倍受关注.最近, NLO分子开关材料引起了人们的重视.将开关效应 引入到NLO材料拓宽了其应用领域,并且对分子光 电器件的发展产生深远影响. NLO开关是指分子 的NLO响应在“开”和“关”两种状态下能够被可逆 地调整.这种转换包括顺反异构、开闭环、氧化 还原 及分子内质子转移 等,这些结构转换导 致分子NLO性质的改变. Lamere等 对金属羰基配 合物进行了实验与理论研究,发现分子内旋转可以 显著衰减此类配合物的 NLO响应. 目前大多数 NLO分子开关主要基于有机金属配合物分子,自由 基体系的NLO开关效应研究相对较少. 1998年, Tsien合成了光照引起结构可逆变化 的荧光蛋白发色团. Voliani等 进一步研究了系列 荧光蛋白发色团的热稳定性,发现荧光蛋白发色团 表现出相当大的二次谐波响应. Meulenaere等 对 荧光蛋白发色团的NLO性质进行了理论和实验研 究.最近, Bhattacharya等 以绿色荧光蛋白(GFP)发 色团为基础, 引入亚胺基氮氧自由基, 研究了系列 含氮氧双自由基衍生物的磁性耦合规律,此类GFP 发色团结构转换引起NLO性质研究未见报道.基于 以上研究,我们对系列含双自由基的GFP发色团结 构改变引起的NLO转换效应进行讨论,为有机自由 基NLO材料的设计提供理论依据. 2 计算模型与方法 GFP发色团分子模型如图 1所示,每个分子有 两个单电子,磁性研究表明,反式结构分子为反铁 磁性耦合,顺式结构分子为铁磁性耦合,所以 a系列 双自由基分子为单重态, b系列双自由基分子为三 重态. 为了获得准确的结构, 溶剂化效应在优化中 被考虑.采用DFT-UB3LYP方法 和6-31G*基组,分 别在气相和极化连续模型(PCM)基础上,以甲醇为 溶剂,优化分子单、三重态的几何构型.计算时分子 的坐标原点选在C1位置, z轴通过桥连键并指向苯 环, xz平面为咪唑啉酮环所在平面. 长程校正杂化交换相关函数CAM-B3LYP方法 降低了被B3LYP方法过高估计的体系第一超极化 率值,并接近耦合簇(CC)方法的计算结果,因此本 文采用UCAM-B3LYP方法计算分子的第一超极化 率.同时采用UBHandHLYP方法对第一超极化率值 进行可靠性分析, Li等 研究表明, UBHandHLYP方 法可将第一超极化率计算机时和有效性进行良好 折中. 在均匀静电场中,分子的能量可按Taylor级数 展开: E = E -∑ i μ i Fi 1 2∑ij αij Fi Fj 1 3∑ijk βijk Fi Fj Fk 4∑ijkl γijkl Fi Fj Fk Fl ... (1) E为无外场时分子的能量, μi 为分子的永久偶极 矩, Fi为外电场在方向 i的分量, αij为线性极化率张 量, βijk和γijkl分别为分子第一、第二超极化率分量.计 算分子极化率和第一超极化率可以采用解析导数 法或数值导数法.文献 报道,解析导数方法较数值 导数法更高效,因此采用解析导数方法计算分子的 静态第一超极化率βtot.计算公式如下: β tot = (β 2 x + β 2 y + β 2 z ) 1 2 (2)

Objective To investigate the association between polymorphisms of α-adducin (ADD) gene Gly460Trp, angiotensin converting enzyme (ACE) gene I/D and kidney lesions in patients with essential hypertension respectively and jointly. Methods The case-control study was performed in 169 hospitalised hypertensive patients and 169 normal subjects (group A). On the basis of creatinine clearance calculated by Cockcroft–Gault equation, hypertensive patients were divided into two groups: normal renal function group (group B: Ccr≥80 ml/min) with 63 subjects and abnormal renal function group (group C: Ccr Results (1) The levels of age, serum creatinine, urea nitrogen and uric acid were higher in group C by comparison with group A and B, and had significant difference (p 0.05). (2) The expected frequencies of the ACE and ADD genotypes were under the assumption of the Hardy-Weinberg equilibrium in hypertensive group and normal group respectively (p>0.05). (3) Chi-square test demonstrated that the distributions of ACE -DD, ADD-TT homozygote and ACE-DD+ADD-TT genotype (25.47%, 30.19% and 13.21% respectively) were higher in group C than in A (the distribution was, 10.06%, 14.79% and 1.59%, respectively) and in B (the distribution was 7.94%, 11.11% and 1.59% respectively); and had significant difference (p 0.05). (4) Binary logistic stepwise regression demonstrated that hypertensive course and ACE-DD+ADD-TT genotype entered the model at last, and was significantly associated with abnormal renal function in group B and C. The OR were 1.006 (95% CI 1.004 to 1.008) and 4.977 (95% CI 1.465 to 16.914). Conclusion It was suggested that both α-adducin-TT genotype and ACE –DD genotype were significantly associated with kidney lesions in patients with essential hypertension, respectively or jointly. ACE-DD+ADD–TT genotype can be the independent risk factor of hypertensive kidney lesions.