Fluorescence quenching over short range in a donor-DNA-acceptor system.
Fluorescence quenching over short range in a donor-DNA-acceptor system.
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供体-DNA-受体系统中短距离荧光猝灭
DOI：
10.1002/cphc.201200924
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
T. J. A. Wolf
中科院分区：
文献类型：
--
作者：
T. Ehrenschwender;Y. Liang;A.-N. Unterreiner;H.-A. Wagenknecht;T. J. A. Wolf
以尼罗红修饰的2′-脱氧尿苷为电荷供体，6-N，N-二甲氨基芘修饰的2 ′-脱氧尿苷为受体，合成了一种新的供体-DNA-受体体系，利用荧光光谱和时间分辨飞秒泵浦-探测技术研究了DNA双链体中的电荷转移.荧光猝灭实验表明，尼罗红的猝灭效率取决于两个组分：1）电荷受体的存在和2）供体和受体之间插入的CG和AT碱基对的数量。令人惊讶的是，两个碱基对的猝灭效率（CG为73%，AT为73%）高于一个碱基对的猝灭效率（CG为68%，AT为37%），而在三个碱基对的间隔处观察到小于10%的猝灭。与时间分辨测量结果的比较揭示了猝灭效率与第一超快时间常数之间的相关性，表明猝灭通过从供体到受体的电荷转移进行。所有的瞬变现象都可以用两种衰变来描述：一种是快速的电荷转移，其速度为600 fs（Δ 1012 s −1），这与施主和受主之间的距离有很大的非线性关系;另一种是较慢的时间常数，只有几皮秒（Δ 1011 s −1），但距离依赖性很弱。纳秒时间尺度上的第三时间常数表示供体分子的荧光寿命。根据这些结果和含时密度泛函理论（TDDFT）计算，可以提出这种短程电荷转移的单步超交换和多步跳跃机制的组合。此外，在非常短的距离下显著更低的猝灭效率和更慢的电荷转移速率表明供体和受体之间的直接相互作用导致DNA双链体的局部结构畸变，这可能在确定短程系统中的电荷转移速率时提供一些不确定性。
A new donor‐DNA‐acceptor system has been synthesized containing Nile red‐modified 2′‐deoxyuridine as charge donor and 6‐N,N‐dimethylaminopyrene‐modified 2′‐deoxyuridine as acceptor to investigate the charge transfer in DNA duplexes using fluorescence spectroscopy and time‐resolved femtosecond pump‐probe techniques. Fluorescence quenching experiments revealed that the quenching efficiency of Nile red depends on two components: 1) the presence of a charge acceptor and 2) the number of intervening CG and AT base pairs between donor and acceptor. Surprisingly, the quenching efficiency of two base pairs (73 % for CG and the same for AT) is higher than that for one base pair (68 % for CG and 37 % for AT), while at a separation of three base pairs less than 10 % quenching is observed. A comparison with the results of time‐resolved measurements revealed a correlation between quenching efficiency and the first ultrafast time constant suggesting that quenching proceeds via a charge transfer from the donor to the acceptor. All transients are satisfactorily described with two decays: a rapid charge transfer with 600 fs (∼1012s−1) that depends strongly and in a non‐linear fashion on the distance between donor and acceptor, and a slower time constant of a few picoseconds (∼1011s−1) with weak distance dependence. A third time constant on a nanosecond time scale represents the fluorescence lifetime of the donor molecule. According to these results and time‐dependent density functional theory (TDDFT) calculations a combination of single‐step superexchange and multistep hopping mechanisms can be proposed for this short‐range charge transfer. Furthermore, significantly less quenching efficiency and slower charge transfer rates at very short distances indicate that the direct interaction between donor and acceptor leads to a local structural distortion of DNA duplexes which may provide some uncertainty in identifying the charge transfer rates in short‐range systems.
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DOI：
--
发表时间：
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期刊：
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影响因子：
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作者：
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影响因子：
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