英语翻译Interactions with DNA.The changes of the electronicabsor

英语翻译
Interactions with DNA.The changes of the electronic
absorption spectrum of 3 as a function of ct-DNA
concentration were used to estimate the DNA binding
constant,Kb (Figure S4 in the Supporting Information).34
Hypochromic shifts were observed at 365 and 457 nm
with a slight bathochromic shift (∼2 nm) for 10.4 μM3 in
the presence of up to 71.5 μM ct-DNA,resulting in Kb=
2.0 \2 106 M-1 (s=1.62) fitted as previously described in
detail.34 The DNA binding constant measured for 3 is
similar to values reported for 2 (106-107 M-1) and for
related DNA intercalating complexes,with values that
are several magnitudes greater than that of the nonintercalator
1 (700 M-1).48-50 As listed in Table 1,only a
modest (1.1-fold) luminescence enhancement is observed
for 10 μM3 upon the addition of 100 μMct-DNA (5mM
Tris,50 mM NaCl,pH=7.5),a result that is strikingly
different from that of the “light-switch” 2 under similar
experimental conditions.12 As previously reported,no
observable luminescence changes in 1 were detected upon
the addition of ct-DNA.51
The ethidium bromide stained agarose gel imaged in
Figure 6 compares the DNA photocleavage of 1-3 upon
irradiation (λirr g 455 nm,tirr = 15 min).Lane 1 shows
the migration of pUC18 alone kept in the dark as a control,
which is composed mostly of unreacted supercoiled
plasmid (formI).Without irradiation,no apparent
DNA cleavage is observed in lanes 2,4,and 6 for
complexes 1-3,respectively.Lanes 5 and 7 show theDNA photocleavage of 2 and 3,respectively,indicating
greater reactivity of 3 compared to 2 under similar
experimental conditions.This result is consistent with
the greater quantum yield of the sensitized 1O2 production
of 3 (Φ1O2
=0.76) relative to that of 2 (Φ1O2
=0.16)
measured in CH3OH.Although 1 has a greater quantum
yield for the production of 1O2 (0.81),negligible
DNAphotocleavage is observed under similar conditions
(lane 3).The difference in DNA photocleavage between
1 and 3 can be explained by the weak electrostatic DNA
binding of the former and tight intercalation of the latter.
The oxygen dependence of the DNA photocleavage by
3 was further investigated,and the results are shown in
Figure S5 in the Supporting Information.Lanes 3 and
4 (Figure S5 in the Supporting Information) show greater
DNA photocleavage by 3 in D2O compared to H2O,
in agreement with the longer lifetime of 1O2 in the
former.52 Additionally,negligible DNA cleavage by 3
was observed under deoxygenated conditions (lane 5,
Figure S5 in the Supporting Information).These findings
suggest that the DNA photocleavage of 3 is primarily
mediated by 1O2.

与DNA的相互作用.3的电子吸收谱随t0-DNA浓度的数变化被用来估算DNA结合常数Kb（支持信息中的图S4）34.在365和457nm处观察到了减色漂移,伴随着在存在直到71.5μM ct-DNA时10.4μM 3稍向红的漂移,导致了符合前面详细描述的Kb＝2.0×106M－1（s=1.62）34.对3测得的DNA结合常数类似于对2报行的值（106～107 M－1）和对于有关DNA插入络合物报行的值,其数值比非插入剂1的值（700 M－1）大几个数量级48-50.如表1所列的那样,对于10μM 3来说,在添加100μM ct-DNA(5mM Tris,50mM NaCl,pH=7.5)时只观察到适度的（1.1倍）发光增强,这是一个与“光开关”2在类似实验条件下明显不同的结果12.如以前报行过的那样,在添加ct-DNA时在1中监测不到可观察到的发光变化51.
成像在图6中的溴乙锭着色的琼脂糖凝胶比较了在辐照下1－3的DNA光断裂（λirr≥455nm,tirr＝15min）.第1行示出了作为对照的单独保持在黑暗中的pUC18的迁移,这大多是由未反应的超螺旋质体（形式1）组成的.在没有辐照的情况下,分别代表络合物1－3的第2、4、6行没有观察到明显的DNA断裂.第5和第7行分别示出了2和3的DNA光断裂,表明了在类似的实验条件下相比于2来说,3有较大的反应性.这一结果与络合物3在CH3OH中测得的致敏1O2产生 相对于2 的较高量子效率相符合.
虽然1对致敏1O2的产生有较大的量子效率（0.81）,但是在类似的条件下观察到的DNA断裂可以忽略不计（第3行）.1和3之间在DNA断裂上的差别可以用前者较弱的静电DNA结合和后者紧的插入来解释.用3的DNA光断裂与氧的相关性做了进一步的研究,结果示于了支持信息中的图S5.第3行和第4行（支持信息中的图S5）表明,用3,在D2O中相比于H2O中有较大的DNA光断裂,与1O2在前者中有较长的寿命相一致52.此外,在去氧条件下观察到3的DNA断裂可以忽略不计（第5行,支持信息中的图S5）.这些发现告诉我们,3的DNA光断裂主要由1O2起作用.