Femtosecond photoisomerization of azobenzene-derivative binding to DNA
Femtosecond photoisomerization of azobenzene-derivative binding to DNA
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DOI：
10.1016/j.jphotochem.2011.08.007
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发表时间：
2011-09-25
影响因子：
4.3
通讯作者：
Yamashita, Mikio
中科院分区：
文献类型：
--
作者：
Chen, Tao;Igarashi, Kazumasa;Yamashita, Mikio
采用速率方程法研究了反式（T）4 '-甲硫基偶氮苯（AzD）与双链DNA（T-AzD-dsDNA）、单链DNA（T-AzD-ssDNA）和T-AzD的超快光致异构和弛豫动力学.所有的解都显示出快（τ（1），A（1））和慢（τ（2），A（2））衰减分量以及偏移分量（A（3））。T-AzD溶液在400和420 nm波长下的负或正吸光度变化行为差异很大，这归因于T-AzD的激发态和基态之间的吸收截面差以及顺式（C）-和T-AzD的基态之间的吸收截面差对探测波长的显著依赖性。T-AzD-dsDNA和T-AzD-ssDNA的S-2（T）态寿命τ（1）分别为30和60 fs，而T-AzD的S-2（T）态寿命τ（1）为220 fs。这可能是由于T-AzD-DNAs中DNA碱基向T-AzD的分子内电子转移所致。这表明在与DNA相互作用的超快光致异构化系统中首次观察到电子转移。而在T到C光异构化的初始过程中，从S-2（T）态到瓶颈中间态I-1（T. C）的动力学速率k（2.1）（T.I）和I-1（T. C）态寿命τ（2）几乎没有变化，大约为1.3 × 10（11）。1.4 x 10（11）和1.6 x 10（11）s（-1），分别为6.7、6.2和6.0 Ps。后者意味着C-异构体的诞生时间对于所有溶液几乎相同。此外，在100 nJ脉冲能量水平下，由A（3）确定的T-C光异构化速率eta（T，C）分别为1.2%、0.36%和0.22%，表明T-AzD分子是最有效的T-C光异构化分子之一。T-AzD-DNA中eta（T，C）的降低是由于激发态寿命τ（1）的显著缩短。(C)2011 Elsevier B. V.保留所有权利。
Ultrafast photoisomerization and relaxation dynamics of trans (T) 4'-methylthioazobenzene (AzD) binding to double-strand DNA (T-AzD-dsDNA) as well as single-strand DNA (T-AzD-ssDNA) and T-AzD were investigated by the measurement of femtosecond absorbance changes on S-2(T) excitation (400 nm) with the rate equation analysis. All the solutions showed the fast (tau(1), A(1)) and slow (tau(2), A(2)) decay components and the offset component (A(3)). The greatly different negative or positive absorbance change behaviors by the probe wavelength of 400 or 420 nm for the T-AzD solution were attributed to the remarkable dependence of the absorption cross-section difference between the T-isomer excited and ground states on the probe wavelength and of that between the cis (C)- and T-isomer ground states. The significantly shorter S-2(T) state lifetimes tau(1) for T-AzD-dsDNA and T-AzD-ssDNA were observed to be 30 and 60 fs, respectively, compared with that (220 fs) of T-AzD. This is presumably attributed to the intramolecular electron transfer from DNA bases to T-AzD in T-AzD-DNAs. suggesting the first observation of electron transfer in an ultrafast photoisomerization system interacting with DNA. While, the kinetic rate k(2.1)(T.I) from the S-2(T) state to the bottleneck intermediate state I-1(T.C) of the initial process in the T to C photoisomerization and the I-1(T.C) state lifetime tau(2) hardly changed like 1.3 x 10(11). 1.4 x 10(11) and 1.6 x 10(11)s(-1) and like 6.7, 6.2 and 6.0 Ps, respectively. The latter implies that the birth time of the C-isomer is almost the same for all the solutions. Furthermore, the T-to-C photoisomerization rate eta(T,C) by single-shot excitation was determined from A(3) to be 1.2%, 0.36% and 0.22% at the 100-nJ pulse energy level, indicating that the T-AzD molecule is one of the most efficient T-to-C photoisomerization molecules. The decrease of eta(T,C) in T-AzD-DNAs is due to the dramatic shortening of the excited-state lifetime tau(1). (C) 2011 Elsevier B.V. All rights reserved.