Molecular dynamics simulations and experimental studies of binding and mobility of 7-tert-butyldimethylsilyl-10-hydroxycamptothecin and its 20(S)-4-aminobutyrate ester in DMPC membranes.
Molecular dynamics simulations and experimental studies of binding and mobility of 7-tert-butyldimethylsilyl-10-hydroxycamptothecin and its 20(S)-4-aminobutyrate ester in DMPC membranes.
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7-叔丁基二甲基甲硅烷基-10-羟基喜树碱及其20(S)-4-氨基丁酸酯在DMPC膜中的结合和迁移率的分子动力学模拟和实验研究。
DOI：
10.1021/mp0600081
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发表时间：
2006
影响因子：
4.9
通讯作者：
Anderson,BradleyD
中科院分区：
文献类型：
--
作者：
Xiang,Tian-Xiang;Jiang,Zhi-Qiang;Song,Lin;Anderson,BradleyD
脂质体在实体瘤中的增强的渗透性和保留使得脂质体制剂对于靶向各种抗肿瘤剂具有吸引力。本研究通过分子动力学模拟和实验研究探讨了拓扑异构酶I抑制剂7-叔丁基二甲基硅基-10-羟基喜树碱（DB-67）及其前体药物20（S）-4-氨基丁酸酯（DB-67-AB）在DMPC脂质体中的结合、取向和动力学性质。对含有DB-67和DB-67-AB单分子的全原子和完全水合液晶双层（2 × 36 DMPC脂质）进行了长达50 ns的MD模拟。通过超离心法测定DB-67和DB-67-AB的膜/水分配系数与pH的关系。在各种溶剂和DMPC脂质体中测量荧光光谱和/或稳态各向异性。在存在和不存在DMPC脂质体的情况下，通过具有荧光检测的HPLC测定可逆DB-67内酯开环的动力学。在整个模拟时间期间，DB-67和DB-67-AB都位于双层膜上DMPC的极性酯基团附近。DB-67和DB-67-AB的平均渗透深度相似（12.4 - 13.2 μ m），前药的质子化氨基被表面水和脂质磷酸基团强溶剂化。结合和荧光实验显示，在DB-67上连接电离的4-氨基丁酸基团后，结合亲和力仅适度降低。结合微环境极性类似于极性溶剂如EtOH和DMSO的极性。动力学实验证实，在DMPC脂质体存在下，DB-67内酯水解被抑制，这与模拟中观察到的内酯环暴露于水的减少一致。结合DB-67和结合DB-67-AB在膜中具有非随机取向和降低的迁移率，特别是对于垂直于双层表面的扩散和旋转弛豫，两者都比在本体水中慢≥2个数量级。分子动力学模拟正确地预测了DB-67-AB与DMPC双层的高结合亲和力，结合DB-67对内酯水解的保护，以及DB-67的20（S）-4-氨基丁酸酯前药的结合没有实质性减少。关键词：脂质双层;脂质体;喜树碱; DB-67;前药;内酯水解;分子动力学模拟; DMPC;膜结合;荧光;抗癌药物
The enhanced permeability and retention of liposomes in solid tumors makes liposomal formulations attractive for the targeting of various antitumor agents. This study explores the binding, orientation, and dynamic properties of a potent topoisomerase I inhibitor, 7-tert-butyldimethylsilyl-10-hydroxycamptothecin (DB-67), and its 20(S)-4-aminobutyrate ester prodrug (DB-67-AB) in DMPC liposomes by molecular dynamics (MD) simulations and experimental studies. MD simulations of an all-atom and fully hydrated liquid-crystalline bilayer (2 × 36 DMPC lipids) containing single molecules of DB-67 and DB-67-AB were conducted for up to 50 ns. Membrane/water partition coefficients for DB-67 and DB-67-AB vs pH were determined by ultracentrifugation. Fluorescence spectra and/or steady-state anisotropies were measured in various solvents and in DMPC liposomes. Kinetics for the reversible DB-67 lactone ring-opening in the presence and absence of DMPC liposomes were determined by HPLC with fluorescence detection. During the entire simulation time both DB-67 and DB-67-AB were located on the bilayer membrane near the polar ester groups of DMPC. The average depth of penetration for DB-67 and DB-67-AB was similar (12.4−13.2 Å) with the prodrug's protonated amino group strongly solvated by surface water and lipid phosphate groups. Binding and fluorescence experiments revealed only a modest reduction in the binding affinity upon attachment of the ionized 4-aminobutyrate group onto DB-67. The binding microenvironment polarity resembles that of a polar solvent such as EtOH and DMSO. Kinetics experiments confirmed that DB-67 lactone hydrolysis is inhibited in the presence of DMPC liposomes, consistent with the reduced exposure of its lactone ring to water, as observed in the simulations. Both bound DB-67 and bound DB-67-AB have nonrandom orientations and reduced mobility in the membrane, especially for diffusion normal to the bilayer surface, and rotational relaxation, both of which are ≥2 orders of magnitude slower than in bulk water. MD simulations correctly predicted the high binding affinities for DB-67-AB to DMPC bilayers, protection of bound DB-67 toward lactone hydrolysis, and the lack of a substantial reduction in binding for the 20(S)-4-aminobutyrate prodrug of DB-67.Keywords: Lipid bilayers; liposomes; camptothecins; DB-67; prodrugs; lactone hydrolysis; molecular dynamics simulation; DMPC; membrane binding; fluorescence; anticancer drugs