McCray J A, Herbette L, Kihara T, Trentham D R
Proc Natl Acad Sci U S A. 1980 Dec;77(12):7237-41. doi: 10.1073/pnas.77.12.7237.
2-Nitrobenzyl derivatives have been used for several years as photolabile protecting groups in synthetic organic chemistry. Recently, P3-1-(2-nitro phenylethyladenosine 5'-triphosphate "caged ATP" was synthesized and its photolysis was shown to generate ATP in situ. This and related reactions have great potential for structural and kinetic studies of both intact and soluble biological systems and it is thus important to define the kinetic characteristics of the photolytic reaction. Caged ATP (2.5 mM) was photolyzed at 347 nm by a single 30-nsec pulse from a frequency-doubled ruby laser of 25 mJ energy to generate 500 microM ATP. The kinetics of the overall reaction were determined by monitoring the kinetics of ATP-induced dissociation of actomyosin, a reaction of known kinetic characteristics. Release of 500 microM ATP was found to be controlled by a process having a rate constant of 2.2 X 10(9) [H+] sec-1 at 22 degrees C at pH 5.8-9.5, which corresponds to 220 sec-1 at pH 7. This process is believed to be the breakdown of an aci-nitro compound, which was identified on the basis of its spectral properties and the photochromicity of related 2-nitrobenzyl compounds.
2-硝基苄基衍生物在合成有机化学中作为光不稳定保护基团已使用多年。最近，合成了P3-1-(2-硝基苯乙基腺苷5'-三磷酸，即“笼形ATP”，并表明其光解能原位产生ATP。该反应及相关反应对于完整和可溶性生物系统的结构和动力学研究具有巨大潜力，因此确定光解反应的动力学特征很重要。将2.5 mM的笼形ATP用一台能量为25 mJ的倍频红宝石激光器发出的单个30纳秒脉冲在347 nm波长下进行光解，以产生500 μM的ATP。通过监测ATP诱导的肌动球蛋白解离的动力学来确定整个反应的动力学，肌动球蛋白解离反应具有已知的动力学特征。发现在22℃、pH 5.8 - 9.5条件下，释放500 μM ATP受一个速率常数为2.2×10⁹[H⁺]秒⁻¹的过程控制，在pH 7时相当于220秒⁻¹。据信该过程是酸式硝基化合物的分解，这是根据其光谱特性和相关2-硝基苄基化合物的光致变色性确定的。
