尿嘧啶激发态动力学溶剂效应的飞秒瞬态吸收光谱研究

沈环; 华林强; 魏政荣

doi:10.7498/aps.71.20220515

摘要

尿嘧啶是构成RNA链最基本的结构单元之一, 其光辐射下的光物理和光化学过程与光致癌变等过程紧密关联, 因而受到广泛的关注. 本文采用飞秒瞬态吸收光谱技术, 研究了在紫外光辐射下, 溶剂效应对尿嘧啶激发态超快动力学的影响. 实验利用一束264 nm的激发光将尿嘧啶激发到¹(π, π*)态(即S₂态). 然后, 利用覆盖范围为280—360 nm的紫外超连续谱作为探测光, 实现对尿嘧啶激发态和基态动力学的同步探测. 测量发现, 尿嘧啶在乙腈溶剂中显现了两个动力学衰减过程, 即9.8 ps (在300 nm处)和>1000 ps, 分别对应于振动冷却过程和三重态的衰减过程. 这一观察与水溶液中的结果差异很大, 因为在水溶液中基本没有测量到三重态的布居. 通过对一系列溶液展开测量, 发现尿嘧啶的超快动力学过程依赖于溶剂形成氢健能力的大小. 越容易形成氢键的溶剂, 尿嘧啶越不容易布居到三重态.

关键词:

Abstract

As one of the building blocks in RNA chain, uracil and its derivatives have attracted a great deal of interest since its ultrafast dynamics is closely related to mutagenic and carcinogenic effects. In this study, the solvent effect on the ultrafast decay of excited uracil is studied by femtosecond transient absorption spectroscopy in the UV region. The uracil molecule is populated to the ¹(π, π*) state (i.e. S₂ state) with a pump pulse at 264 nm. Broad-band white light continuum in the UV region from 280 to 360 nm is used as the probe. With a detail analysis of the measured transient spectra, two decay time constants, i.e. 9.8 ps and > 1000 ps, are directly obtained at 300 nm in the solvent of acetonitrile. Compared with our previous experiments, where no obvious triplet population is observed in water, triplet population is found to play an important role in acetonitrile. A comparison of excited-state dynamics among different solvents is also carried out. It reveals that the decay from the ¹(n, π*) state (i.e., S₁ state) to the T₁ state shows a clear dependence on the H bonding of the solvents. With stronger H bonding, the ¹(n, π*) excited state decays faster and has less chance to transfer to the triplet state. These results suggest that only when the ¹(n, π*) state has excess vibrational energy can it transit to the triplet state through the intersystem crossing process. With this new information obtained in the present measurement, the decay dynamics of uracil on the S₂ excited state can be further understood.

Keywords:

femtosecond transient absorption spectroscopy /
uracil /
excited-state dynamic /
solvent effect

作者及机构信息

1.
华中农业大学理学院, 武汉　430070

2.
中国科学院精密测量科学与技术创新研究院, 波谱与原子分子物理国家重点实验室, 武汉　430071

3.
湖北大学物理与电子科学学院, 武汉　430062

通信作者: 魏政荣, weizhengrong@hubu.edu.cn

基金项目: 国家自然科学基金(批准号: 12074109)和国家自然科学基金联合基金(批准号: U21A20435)资助的课题.

Authors and contacts

1.
College of Science, Huazhong Agricultural University, Wuhan 430070, China

2.
State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan 430071, China

3.
Faculty of Physics and Electronic Science, Hubei University, Wuhan 430062, China

Corresponding author: Wei Zheng-Rong, weizhengrong@hubu.edu.cn

Funds: Project supported by the National Natural Science Foundation of China (Grant No. 12074109) and the Joint Funds of the National Natural Science Foundation of China (Grant No. U21A20435).

文章全文

参考文献

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[2]	Pfeifer G P, You Y H, Besaratinia A 2005 Mutat. Res.- Fund. Mol. Mech. Mutagen 571 19 Google Scholar
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施引文献

图 1 在不同的泵浦和探测脉冲的时间延迟下尿嘧啶在乙腈溶剂中的瞬态吸收光谱　(a) 1—19.5 ps; (b) 59.5—79.5 ps

Fig. 1. Transient absorbance change of uracil in acetonitrile at different pump-probe delays: (a) 1–19.5 ps; (b) 59.5– 79.5 ps.

下载: 全尺寸图片幻灯片

图 2 在300 nm处尿嘧啶在乙腈中的瞬态吸收信号在不同的泵浦-探测光时间延迟下的变化曲线

Fig. 2. Time-dependent absorbance change of uracil in acetonitrile with different pump-probe delays at 300 nm.

下载: 全尺寸图片幻灯片

图 3 尿嘧啶在乙腈溶剂中的光激发衰减动力学过程示意图

Fig. 3. Jablonski diagram of the proposed decay mechanism for photo-excited uracil in acetonitrile.

下载: 全尺寸图片幻灯片

图 4 在不同的泵浦和探测脉冲的时间延迟下尿嘧啶在甲醇溶剂中的瞬态吸收光谱　(a) 0.5—20.3 ps; (b) 22.3—50.3 ps

Fig. 4. Transient absorbance change of uracil in methanol at different pump-probe delays: (a) 0.5–20.3 ps; (b) 22.3–50.3 ps.

下载: 全尺寸图片幻灯片

表 1 在不同溶剂中观察到的时间常数

Table 1. Observed time constants in different solvents.

乙腈乙酸乙酯甲醇乙二醇水

^aτ₁/ps 9.8 6.8 3.5 3.1 1.1
^bτ₂/ps >1000 >1000 >1000 >1000 >1000

^a 以300 nm处的衰减曲线为例; ^b τ₂ 在之前的研究中未能被精确测量.

下载: 导出CSV

map

[1]	Zierhut M, Roth W, Fischer I 2004 Phys. Chem. Chem. Phys. 6 5178 Google Scholar
[2]	Pfeifer G P, You Y H, Besaratinia A 2005 Mutat. Res.- Fund. Mol. Mech. Mutagen 571 19 Google Scholar
[3]	de Gruijl F R 1999 Eur. J. Cancer 35 2003 Google Scholar
[4]	Gustavsson T, Sarkar N, Lazzarotto E, Markovitsi D, Improta R 2006 Chem. Phys. Lett 429 551 Google Scholar
[5]	Hare P M, Crespo-Hernandez C E, Kohler B 2007 Proc. Natl. Acad. Sci. U. S. A 104 435 Google Scholar
[6]	Gustavsson T, Banyasz A, Lazzarotto E, Markovitsi D, Scalmani G, Frisch M J, Barone V, Improta R 2006 J. Am. Chem. Soc 128 607 Google Scholar
[7]	Matsika S 2004 J. Phys. Chem. A 108 7584 Google Scholar
[8]	Barbatti M, Aquino A J A, Szymczak J J, Nachtigallova D, ́Hobza P, Lischka H 2010 Proc. Natl. Acad. Sci. U. S. A 107 21453 Google Scholar
[9]	Hare P M, Crespo-Hernandez C E, Kohler B 2006 J. Phys. Chem. B 110 18641 Google Scholar
[10]	Gustavsson T, Sarkar N, Lazzarotto E, Markovitsi D, Barone V, Improta R 2006 J. Phys. Chem. B 110 12843 Google Scholar
[11]	Gustavsson T, Sarkar N, Banyasz A, Markovitsi D, Improta R 2007 Photochem. Photobiol 83 595 Google Scholar
[12]	Hua X, Hua L, Liu X 2015 J. Phys. Chem. A 119 12985 Google Scholar
[13]	Hua X, Hua L, Liu X 2016 Phys. Chem. Chem. Phys 18 13904 Google Scholar
[14]	Li P, Xue J, Zheng X 2019 J. Raman. Spectrosc 50 345 Google Scholar
[15]	Santoro F, Barone V, Gustavsson T, Improta R 2006 J. Am. Chem. Soc 128 16312 Google Scholar
[16]	Improta R, Barone V 2008 Theor. Chem. Acc 120 491 Google Scholar
[17]	Improta R, Barone V, Lami A, Santoro F 2009 J. Phys. Chem. B 113 14491 Google Scholar
[18]	Etinski M, Marian C M 2010 Phys. Chem. Chem. Phys 12 15665 Google Scholar
[19]	Danillo V, Adalberto V S A, Antonio C B 2021 Molecules 26 5191 Google Scholar
[20]	Salet C, Bensasson R 1975 Photochem. Photobiol 22 231 Google Scholar
[21]	Gorner H 1990 Photochem. Photobiol 52 935 Google Scholar
[22]	Charvat A, Assmann J, Abel B, Schwarzer D, Henning K, Luther K, Troe J 2001 Phys. Chem. Chem. Phys 3 2230 Google Scholar
[23]	Schwarzer D, Hanisch C, Kutne P, Troe J 2002 J. Phys. Chem. A 106 8019 Google Scholar
[24]	Schwarzer D, Kutne P, Schroder C, Troe J 2004 J. Chem. Phys 121 1754 Google Scholar
[25]	Schwarzer D, Troe J, Votsmeier M, Zerezke M 1996 J. Chem. Phys 105 3121 Google Scholar
[26]	Schwarzer D, Troe J, Votsmeier M, Zerezke M 1997 Ber. Bunsen. Phys. Chem. 101 595 Google Scholar

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尿嘧啶激发态动力学溶剂效应的飞秒瞬态吸收光谱研究