Synthesis and crystal structure of a silver(I) 6-methylmercaptopurine riboside complex

Silver nitrate reacts with 6-methylmercaptopurine riboside (6-MMPR) in aqueous solution containing methanol and dimethyl sulfoxide at room temperature to give a colourless crystalline complex, namely, bis(6-methylmercaptopurine riboside-κN⁷)(nitrato-κ²O,O′)silver(I) 2.32-hydrate, [Ag(NO₃)(C₁₁H₁₄N₄O₄S)₂]·2.32H₂O. The crystal structure, determined from synchrotron diffraction data, shows a central Ag^I ion on a crystallographic twofold rotation axis, coordinated in an almost linear fashion by two 6-MMPR ligands via atom N7 (purine numbering), with the nitrate counter-ion loosely coordinated as a bidentate ligand, forming a discrete molecular complex as an approximate dihydrate. The complex and water molecules are connected in a three-dimensional network by hydrogen bonding.     

6-巯基嘌呤互变异构体的密度泛函理论计算

在密度泛函B3LYP/6-311G水平下,对8种气相和水相中可能存在的6-巯基嘌呤异构体进行了几何构型的全自由度优化,并计算出它们的总能量、焓、熵、吉布斯自由能．Onsager反应场溶剂模型用于水相的计算．计算结果表明,6-巯基嘌呤在气相和水相中主要以硫酮形式存在．在气相中,硫酮．N(7)(H)要比硫酮-N(9)(H)更稳定,而在水相中,则硫酮-N(9)(H)要比硫酮-N(7)(H)更稳定．计算结果同已有实验结果一致．6-巯基嘌呤的熵效应小,对互变异构平衡几乎没有显著的影响,而焓变对互变异构产生了主要的影响．较详细地讨论了水溶剂化作用对异构体的能量、几何结构、电荷分布和偶极矩的影响,溶剂化吉布斯自由能与异构体的气相偶极矩存在相关性．     

急性淋巴细胞白血病患儿红细胞中硫嘌呤甲基转移酶活性的HPLC分析

建立了急性淋巴细胞白血病患儿血液中红细胞中的硫嘌呤甲基转移酶活性(TPMT)的HPLC测定法。采用反相高效液相色谱法直接测定酶促反应的产物浓度,从而计算红细胞中TPMT的活性。以S-腺苷-L-甲硫氨酸(SAM)作为甲基供给体,6-硫鸟嘌呤(6-TG)作为酶反应底物,TPMT催化6-TG生成2-氨基-6-甲基巯基嘌呤(6-MTG),采用HClO4溶液终止反应及沉淀蛋白,分离上清液进行色谱分析。色谱柱为AichromBond-1 C18柱(5μm,4.6mm i.d.×150mm);等梯度洗脱,流动相为V(乙腈)∶V(0.01mol/L磷酸钾缓冲溶液)=6∶94(用HCl调pH2.74),荧光检测器检测,激发波长为310nm,发射波长为390nm。结果表明,6-MTG在0~250μg/mL范围内呈良好的线性关系,相关系数r=0.9999,检出限为0.093μg/L(S/N=3),回收率为81.4%~106.3%。方法能用地巯基嘌呤类药物药代研究和临床用药监测常规分析。     

Comparison of 6‐mercaptopurine with 6‐thioguanine for the analysis of thiopurine S‐methyltransferase activity in human erythrocyte by LC–MS/MS

Thiopurines (TPDs) are first‐line drugs in treating neuromyelitis optica spectrum disorders (NMOSD). Evaluation of thiopurine S‐ methyltransferase activity (TPMT), a major determinant of TPD toxicity, before TPD treatment using 6‐mercaptopurine (6‐MP) and 6‐thioguanine (6‐TG) as substrate was suggested. However, the equivalent of the two substrates in TPMT activity evaluation was unknown, and an alternative substrate was required in TPMT activity evaluation in patients who were already taking 6‐MP or 6‐TG. Before evaluating the agreement of 6‐MP and 6‐TG in TPMT activity measurement in patients with NMOSD, the affinity of the two substrates for the active center of TPMT should be established. A computer‐based simulation indicated that 6‐MP and 6‐TG had similar affinities for the two active sites of TPMT. According to the guidelines, an LC–MS/MS method was developed and validated to evaluate the TPMT activity in human erythrocyte hemolysate using 6‐MP or 6‐TG as substrates via 1 h incubation at 37°C. The method was applied in 81 patients with NMOSD. Evaluated by Bland–Altman plot, 6‐methylmercaptopurine and 6‐methylthioguanine represented TPMT activities were in agreement with each other. Further studies are warranted to confirm the results.