Using difference spectrophotometry to study the influence of different ions and buffer systems on drug protein binding
Using difference spectrophotometry to study the influence of different ions and buffer systems on drug protein binding
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DOI：
10.1081/ddc-100102233
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发表时间：
1999-01-01
影响因子：
3.4
通讯作者：
Afifi, NN
中科院分区：
文献类型：
--
作者：
Afifi, NN
采用差示分光光度法研究了不同离子和缓冲体系对消炎药替诺昔康与人血清白蛋白（HSA）结合的影响。氯离子和钠离子均降低了其结合亲和力。氯离子对初级结合常数K-1的影响较大，而钠离子对次级结合常数K-2的影响较大。结合位点n(1)和n(2)的数量不受影响，除了在0.12% HSA下，钠离子的存在使n(2)减半。钾离子显著增加K-1。钾离子代替钠离子的存在增加了低HSA浓度下的结合亲和力。除了0.12% HSA外，钾离子存在时结合位点nl和n(1)的数量比钠离子存在时少。二价钙镁阳离子增加了HSA与替诺西康的结合亲和力，对K-1的影响更大。镁离子对K-1的影响发生在MgCl2浓度增加到3和9 mM时，其中前者似乎是一个临界浓度。一级结合位点nl的数量不受钙离子的影响，但在1 mM MgCl2的作用下减少了一半。钙和镁阳离子均降低n(2)，当任何一个阳离子浓度增加到9 mM时，n(2)减少一半。缓冲系统对替诺昔康与HSA结合的影响取决于HSA浓度。当HSA浓度为0.04%和0.16%时，Sorensen磷酸盐缓冲液的K-1值高于Tris缓冲液，而当HSA浓度为0.08%和0.12%时，K-1值则相反。其他结合参数(K-2, n（1)和n(2)）在Sorensen's phosphate中高于Tris缓冲液。然而;在一定的HSA浓度下，两种缓冲体系中这些参数的值具有可比性。
Difference spectrophotometry was used to investigate the effect of different ions and buffer systems on the binding of the anti-inflammatory drug tenoxicam to human serum albumin (HSA). Chloride anions, as well as sodium cations, were found to decrease the binding affinity. The effect of chloride ions was greater on the primary binding constant K-1, while sodium ions had a greater effect on the secondary binding constant K-2. The number of binding sites n(1) and n(2) were not affected except at 0.12% HSA, for which the presence of sodium ions halved n(2). Potassium ions significantly increased K-1. The presence of potassium instead of sodium ions increased binding affinity at lower HSA concentrations. The number of binding sites nl and n(1) were fewer in presence of potassium than in the presence of sodium ions except at 0.12% HSA. The divalent calcium and magnesium cations increased the binding affinity of HSA to tenoxicam, with a greater effect on K-1. The effect of magnesium ions on K-1 occurred when the MgCl2 concentration was increased to 3 and 9 mM, with the former seeming to be a critical concentration. The number of primary binding sites nl was not affected by calcium ions, but was halved by 1 mM MgCl2. Both calcium and magnesium cations decreased n(2), which was halved when the concentration of either cation was increased to 9 mM. The effect of buffer systems on tenoxicam binding to HSA was dependent on HSA concentration. The value of K-1 was higher in Sorensen's phosphate buffer than in Tris [tris(hydroxymethyl) aminomethane HCl] buffer when the HSA concentration was 0.04% and 0.16%, while the reverse was observed at 0.08% and 0.12% HSA. The other binding parameters (K-2, n(1), and n(2)) were higher in Sorensen's phosphate than in Tris buffer. However; at certain HSA concentrations the values of such parameters were comparable in both buffer systems.