Deck Kathryn M, Tseng T Andrew, Burstyn Judith N
Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Inorg Chem. 2002 Feb 25;41(4):669-77. doi: 10.1021/ic0107025.
A 6000-fold rate enhancement has been observed for the hydrolysis of bis(p-nitrophenyl)phosphate (BNPP) in the presence of 0.2 mM Cu(i-Pr(3)[9]aneN(3))(2+) at pH 9.2 and 50 degrees C. In a direct comparison, the rate of hydrolysis of BNPP is accelerated at least 60-fold over the previously reported catalyst Cu([9]aneN(3))(2+). As observed for Cu([9]aneN(3))(2+), hydrolysis is selective for diesters over monoesters. Hydrolysis of BNPP by Cu(i-Pr(3)[9]aneN(3))(2+) is catalytic, exhibiting both rate enhancement and turnover. The reaction is inhibited by both p-nitrophenyl phosphate and inorganic phosphate. The reaction is first-order in substrate and half-order in metal complex, with a k(1.5) of 0.060 +/- 0.004 M(-1/2) s(-1) at 50 degrees C. The temperature dependence of the rate constant results in a calculated activation enthalpy (Delta H(++) of 51 +/- 2 kJ mol(-1) and activation entropy (Delta S(++)) of -110 +/- 6 J mol(-1) K(-1). The kinetic pK(a) of 7.8 +/- 0.2 is close to the thermodynamic pK(a) of 7.9 +/- 0.2, consistent with deprotonation of a coordinated water molecule in the active form of the catalyst. The active catalyst Cu(i-Pr(3)[9]aneN(3))(OH)(OH(2)) is in equilibrium with an inactive dimer, and the formation constant for this dimer is between 216 and 1394 M(-1) at pH 9.2 and 50 degrees C. Temperature dependence of the dimer formation constant K(f) indicates an endothermic enthalpy of formation for the dimer of 27 +/- 3 kJ mol(-1). The time course of anaerobic DNA cleavage by Cu(i-Pr(3)[9]aneN(3))(2+) is presented over a wide range of concentrations at pH 7.8 at 50 degrees C. The concentration dependence of DNA cleavage by Cu([9]aneN(3))(2+) and Cu(i-Pr(3)[9]aneN(3))(2+) reveals a maximum cleavage efficiency at sub-micromolar concentrations of cleavage agent. DNA cleavage by Cu(i-Pr(3)[9]aneN(3))(2+) is twice as efficient at pH 7.8 as at pH 7.2.
在pH 9.2和50℃条件下，当存在0.2 mM Cu(i-Pr(3)[9]aneN(3))(2+)时，观察到双（对硝基苯基）磷酸酯（BNPP）的水解速率提高了6000倍。直接比较发现，BNPP的水解速率比先前报道的催化剂Cu([9]aneN(3))(2+)至少加快了60倍。正如Cu([9]aneN(3))(2+)的情况一样，水解对二酯的选择性高于单酯。Cu(i-Pr(3)[9]aneN(3))(2+)催化BNPP的水解，表现出速率增强和周转。对硝基苯基磷酸酯和无机磷酸均能抑制该反应。该反应对底物为一级反应，对金属配合物为半级反应，在50℃时k(1.5)为0.060±0.004 M(-1/2) s(-1)。速率常数的温度依赖性导致计算出的活化焓（ΔH(++)）为51±2 kJ mol(-1)，活化熵（ΔS(++)）为-110±6 J mol(-1) K(-1)。动力学pK(a)为7.8±0.2，接近热力学pK(a)的7.9±0.2，这与催化剂活性形式中配位水分子的去质子化一致。活性催化剂Cu(i-Pr(3)[9]aneN(3))(OH)(OH(2))与无活性二聚体处于平衡状态，在pH 9.2和50℃时，该二聚体的形成常数在216至1394 M(-1)之间。二聚体形成常数K(f)的温度依赖性表明二聚体形成的焓变为吸热，为27±3 kJ mol(-1)。给出了在50℃、pH 7.8条件下，不同浓度的Cu(i-Pr(3)[9]aneN(3))(2+)进行厌氧DNA切割的时间进程。Cu([9]aneN(3))(2+)和Cu(i-Pr(3)[9]aneN(3))(2+)对DNA切割的浓度依赖性表明，在亚微摩尔浓度的切割剂下，切割效率最高。Cu(i-Pr(3)[9]aneN(3))(2+)在pH 7.8时对DNA的切割效率是pH 7.2时的两倍。
