PHOTOPHYSICS OF 2'-DEOXYURIDINE (DU) NUCLEOSIDES COVALENTLY SUBSTITUTED WITH EITHER 1-PYRENYL OR 1-PYRENOYL - OBSERVATION OF PYRENE-TO-NUCLEOSIDE CHARGE-TRANSFER EMISSION IN 5-(1-PYRENYL)-DU
PHOTOPHYSICS OF 2'-DEOXYURIDINE (DU) NUCLEOSIDES COVALENTLY SUBSTITUTED WITH EITHER 1-PYRENYL OR 1-PYRENOYL - OBSERVATION OF PYRENE-TO-NUCLEOSIDE CHARGE-TRANSFER EMISSION IN 5-(1-PYRENYL)-DU
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DOI：
10.1021/ja00141a002
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发表时间：
1995-09-13
影响因子：
15
通讯作者：
EATON, BE
中科院分区：
文献类型：
--
作者：
NETZEL, TL;ZHAO, M;EATON, BE
本文报道了两种吡啶取代尿苷核苷的合成、电子吸光度、发射光谱和发射动力学结果，作为一项正在进行的研究的一部分，该研究旨在研究这些核苷在不同碱基序列组成的DNA低聚物和双聚物中嵌入的光物理和光化学行为。这两个标记是1-芘基本身和1-羧基芘基（1-pyrenoyl），它们都直接连接到2'-脱氧尿嘧啶（dU）的5位上，这些直接连接极大地限制了芘标记在连接到DNA低聚物或双聚物时的构象范围。5-(1-pyrenyl)- du， 1在甲醇（MeOH）中不存在π， π *释放，但在四氢呋喃（THF）中存在。对于1在MeOH中，存在宽电荷转移（CT）发射，在470 nm处最大，量子产率为0.027；在THF中，1存在π， π *发射，在395 nm处最大，量子产率为0.42。热力学分析表明，MeOK中释放的1的CT光产物为芘(.+)/dU（.-）。MeOH中1的发射动力学是三指数的，但不同衰减寿命相对振幅的波长变化表明，ct态弛豫是双指数的，寿命小于等于50 ps和0.9 ns。同样，MeOH中1的pi，pi*态也有两个电子转移（ET）猝灭寿命小于等于50 ps和2-3 ns。MeOH中1的稳态发射光谱表明，在所有波长下，仅有的几个长寿命的π， π *：态的发射都被0.9 ns的CT发射所主导，而5-(1-pyrenoyl)- du， 2在MeOH和THF中都只有π，pi*发射，发射量子产率分别为0.002和0.028。THF中2的发射动力学至少为四倍指数，最长的发射寿命约为95 ns。然而，只有大约10%的相对发射振幅衰减，寿命大于10ns。核苷1和核苷2的光谱和发射动力学数据支持这样的结论：它们在溶液中都有多个构象，芘和尿苷pi-体系的相对取向在决定芘的ET猝灭速率和光产物中的电荷重组速率方面起着至关重要的作用。
This paper reports syntheses, electronic absorbance and emission spectra, and emission kinetics results for two types of pyrene-substituted uridine nucleosides as part of an ongoing study which is examining the photophysical and photochemical behaviors of these same nucleosides embedded in DNA oligomers and duplexes with varying base-sequence composition, The two labels are 1-pyrenyl itself and 1-carboxypyrenyl (1-pyrenoyl) which are each joined directly to the 5-position of 2'-deoxyuridine (dU), These direct attachments significantly restrict the range of conformations available to the pyrene label when it is attached to a DNA oligomer or duplex. pi,pi* emission is absent for 5-(1-pyrenyl)-dU, 1, in methanol (MeOH) but present in tetrahydrofuran (THF). For 1 in MeOH, broad charge-transfer (CT) emission is present with a maximum at 470 nm and a quantum yield of 0.027; for 1 in THF, pi,pi* emission is present with a maximum at 395 nm and quantum yield of 0.42. Thermodynamic considerations suggest that the CT photoproduct of 1 which emits in MeOK is pyrene(.+)/dU(.-). The emission kinetics of 1 in MeOH are triexponential, but the wavelength variation of the relative amplitudes of the different decay lifetimes indicates that the CT-state relaxations are biexponential with lifetimes of less than or equal to 50 ps and 0.9 ns, Similarly, the pi,pi* State of 1 in MeOH also has two electron transfer (ET) quenching lifetimes of less than or equal to 50 ps and 2-3 ns. The steady-state emission spectrum of 1 in MeOH shows that emission from the few long-lived pi,pi*: states is dominated at all wavelengths by the 0.9-ns lived CT emission, In contrast, only pi,pi* emission is observed for 5-(1-pyrenoyl)-dU, 2, in both MeOH and THF with emission quantum yields of 0.002 and 0.028, respectively. The emission kinetics for 2 in THF are at least quadruply exponential having the longest emission lifetime of ca. 95 ns. However, only about 10% of the relative emission amplitude decays with lifetimes greater than 10 ns. Approximately 90% of the emission amplitude decays on the same time scale as for 2 in MeOH, The spectral and emission kinetics data for nucleosides 1 and 2 support the conclusions that each has multiple conformers in solution and that the relative orientation of the pyrene and uridine pi-systems plays a crucial role in determining the rates of both ET quenching of pyrene* and charge-recombination in the photoproduct.