Faculty of Pharmaceutical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda 278-8510, Japan.
Inorg Chem. 2010 Feb 1;49(3):888-99. doi: 10.1021/ic901279t.
We previously reported on a 8-quinolinol-pendant cyclen (L(5)) as a Zn(2+) fluorophore (cyclen = 1,4,7,10-tetraazacyclododecane) and its caged derivative, 8-(benzenesulfonyloxy)-5-(N,N-dimethylaminosulfonyl)quinolin-2-ylmethyl-pendant cyclen (BS-caged-L(5)), which can be reactivated by hydrolysis of benzenesulfonyl group upon complexation with Zn(2+) at neutral pH to give a 1:1 Zn(2+)-L(5) complex (Zn(H(-1)L(5))). We report herein on the synthesis of 5,7-bis(N,N-dimethylaminosulfonyl)-8-hydroxyquinolin-2-ylmethyl-pendant cyclen (L(6)) and its caged derivative (BS-caged-L(6)) for more sensitive and more efficient cell-membrane permeability than those of L(5) and BS-caged-L(5). By potentiometric pH, (1)H NMR, and UV-vis spectroscopic titrations, the deprotonation constants pK(a1)-pK(a6) of H(5)L(6) were determined to be <2, <2, <2, 2.5 +/- 0.1 (for the 8-OH group of the quinoline moiety), 9.7 +/- 0.1, and 10.8 +/- 0.1 at 25 degrees C with I = 0.1 (NaNO(3)). The results of (1)H NMR, potentiometric pH, UV-vis, and fluorescent titrations showed that L(6) rapidly forms a 1:1 complex with Zn(2+) (Zn(H(-1)L(6))), the dissociation constant of which is 50 fM at pH 7.4. The fluorescent emission of Zn(H(-1)L(6)) at 478 nm is 32 times as large as that of L(6) (excitation at 370 nm), and the fluorescent quantum yield of Zn(H(-1)L(6)) (Phi(F) = 0.41) is much greater than that of Zn(H(-1)L(5)) (Phi(F) = 0.044). The BS-caged-L(6) was reactivated by hydrolysis of the benzenesulfonyl moiety more rapidly (completes in 30 min at pH 7.4 at 37 degrees C) than BS-caged-L(5), presumably enabling the practical detection of Zn(2+) in sample solutions and living cells. The photochemical deprotection of BS-caged-L(6) and the cell membrane permeability of L(6) and BS-caged-L(6) are also described.
我们之前曾报道过一种 8-喹啉醇-环戊烷（L(5)）作为 Zn(2+)荧光团（环戊烷= 1,4,7,10-四氮杂环十二烷）及其笼状衍生物，8-(苯磺酰氧基）-5-（N,N-二甲基氨基磺酰基）喹啉-2-基甲基-环戊烷（BS-笼状-L(5)），它可以通过在中性 pH 下与 Zn(2+)络合时苯磺酰基的水解而被重新激活，得到 1:1 Zn(2+)-L(5)配合物（Zn(H(-1)L(5))）。本文报道了 5,7-双（N,N-二甲基氨基磺酰基）-8-羟基喹啉-2-基甲基-环戊烷（L(6)）及其笼状衍生物（BS-笼状-L(6)）的合成，与 L(5)和 BS-笼状-L(5)相比，它们具有更高的细胞通透性和灵敏度。通过电位 pH、(1)H NMR 和紫外可见光谱滴定，确定了 H(5)L(6)的去质子常数 pK(a1)-pK(a6)分别为 <2、<2、<2、2.5 +/- 0.1（喹啉部分的 8-OH 基团）、9.7 +/- 0.1 和 10.8 +/- 0.1，在 25 摄氏度下 I = 0.1（硝酸钠）。(1)H NMR、电位 pH、紫外可见和荧光滴定的结果表明，L(6)与 Zn(2+)迅速形成 1:1 配合物（Zn(H(-1)L(6))），其离解常数在 pH 7.4 时为 50 fM。Zn(H(-1)L(6))在 478nm 处的荧光发射比 L(6)（激发波长为 370nm）大 32 倍，Zn(H(-1)L(6))的荧光量子产率（Phi(F) = 0.41）远大于 Zn(H(-1)L(5))（Phi(F) = 0.044）。BS-笼状-L(6)比 BS-笼状-L(5)更快地通过苯磺酰基的水解被重新激活（在 pH 7.4 下 37 摄氏度 30 分钟内完成），这可能使我们能够在样品溶液和活细胞中实际检测 Zn(2+)。还描述了 BS-笼状-L(6)的光化学去保护和 L(6)和 BS-笼状-L(6)的细胞膜通透性。
