Department of Chemistry, Islamic Azad University, Central Tehran Branch (IAUCTB), Tehran, Iran.
J Photochem Photobiol B. 2011 Oct 5;105(1):34-9. doi: 10.1016/j.jphotobiol.2011.06.008. Epub 2011 Jul 19.
Oseltamivir phosphate (OP; tamiflu) is an antiviral pro-drug, which is hydrolyzed hepatically to the active metabolite oseltamivir carboxylate (OC). It is the first orally neuraminidase inhibitor that was used in the treatment and prophylaxis of influenza virus A and B infection. Human serum albumin (HSA) is the most abundant of the proteins in the blood plasma and is major transporter for delivering several drugs in vivo. This study was designed to examine the interaction of HSA with oseltamivir phosphate (OP) and oseltamivir carboxylate (OC) in aqueous solution at physiological conditions, using a constant protein concentration and various drug contents. FTIR, UV-Vis spectroscopic methods were used to determine the drugs binding mode, the binding constant and the effects of drug complexation on protein secondary structure. Structural analysis showed that OP and OC bind HSA via polypeptide polar groups with overall binding constants of K(OP-HSA)=3.86(± 1.05)× 10(3)M(-1) and K(OC-HSA)=1.5(±0.45) × 10(2)M(-1). The alterations of protein secondary structure are attributed to a partial destabilization of HSA on drug complexation. The protein secondary structure showed no major alterations at low drugs concentrations (50 μM), whereas at higher content (1mM), decrease of α-helix from 58% (free HSA) to 38% (OP-HSA)-48% (OC-HSA), decrease of random coil from 15% (free HSA) to 2% (OP-HSA)-3% (OC-HSA), increase of β-sheet from 6% (free HSA) to 20% (OC-HSA)-29% (OP-HSA) and turn from 8% (free HSA) to 17% (OC-HSA)-19% (OP-HSA) occurred in the drug-HSA complexes. These observations indicated that low drug content induced protein stabilization, whereas at high drug concentration, a partial protein destabilization occurred in these drug-HSA complexes.
磷酸奥司他韦（OP；达菲）是一种抗病毒前药，在肝脏中水解为活性代谢物奥司他韦羧酸（OC）。它是第一种用于治疗和预防甲型和乙型流感病毒感染的口服神经氨酸酶抑制剂。人血清白蛋白（HSA）是血浆中最丰富的蛋白质，是体内输送多种药物的主要载体。本研究旨在研究在生理条件下，使用恒定的蛋白质浓度和不同的药物含量，奥司他韦磷酸（OP）和奥司他韦羧酸（OC）与水溶液中 HSA 的相互作用。采用傅里叶变换红外光谱（FTIR）、紫外-可见光谱（UV-Vis）光谱法测定药物结合模式、结合常数以及药物络合对蛋白质二级结构的影响。结构分析表明，OP 和 OC 通过多肽极性基团与 HSA 结合，结合常数分别为 K（OP-HSA）=3.86（±1.05）×10（3）M（-1）和 K（OC-HSA）=1.5（±0.45）×10（2）M（-1）。蛋白质二级结构的变化归因于药物络合时 HSA 的部分失稳。在低药物浓度（50 μM）下，蛋白质二级结构没有发生重大变化，而在较高浓度（1mM）下，α-螺旋从 58%（游离 HSA）减少到 38%（OP-HSA）-48%（OC-HSA），无规卷曲从 15%（游离 HSA）减少到 2%（OP-HSA）-3%（OC-HSA），β-折叠从 6%（游离 HSA）增加到 20%（OC-HSA）-29%（OP-HSA），转角从 8%（游离 HSA）增加到 17%（OC-HSA）-19%（OP-HSA）。这些观察结果表明，低药物含量诱导蛋白质稳定，而在高药物浓度下，这些药物-HSA 络合物中发生了部分蛋白质失稳。
