杜鹃素新结构衍生物与人血清白蛋白相互作用的光谱及分子对接

采用光谱法及分子对接法考察了该化合物与人血清白蛋白(HSA)的相互作用。荧光光谱分析表明,DJS-NO_2对HSA的荧光有明显的猝灭作用,其机制属于静态荧光猝灭;温度为25℃和37℃时,猝灭常数分别为6.691×10~(13)mol/(L·s)和3.433×10~(13)mol/(L·s);结合常数分别为4.914×10~5mol/L和4.610×10~5mol/L,具有一个结合位点。热力学分析表明,该化合物与HSA之间的结合以疏水作用力为主;三维荧光光谱分析表明DJS-NO_2导致HSA氨基酸残基微环境和二级构象发生变化。圆二色谱分析显示二者的结合使得HSA的α-螺旋含量减少,提示HSA构象发生变化。分子模拟结果显示DJS-NO_2主要与HSA的位点I结合,且该化合物通过氢键与ALA118结合最紧密。     

二苯甲酮与人血清白蛋白相互作用的研究

在模拟人体生理条件下(pH=7.4),采用荧光光谱、位点竞争、三维荧光光谱研究了二苯甲酮(BP)与人血清白蛋白(HSA)之间的相互作用。根据修正的Stern-Volmer方程计算了不同温度下的结合常数,并结合Van't Hoff方程计算出相应的热力学参数。实验结果表明,BP对HSA的猝灭机制为静态猝灭过程,氢键和范德华力是维持BP-HSA复合物稳定的主要作用力;位点竞争实验揭示了BP在HSA上的结合位点位于亚域结构II A上的疏水腔中(site I位);三维荧光光谱分析表明BP使HSA发生了轻微地解旋,HSA的二级结构发生了改变。     

全氟丙酸与人血清白蛋白结合作用机制的计算模拟与光谱法研究

通过分子对接和动力学模拟的计算方法模拟人血清白蛋白(HSA)的三维空间结构,建立了HSA与全氟丙酸(IPC-PFFA-3)相互作用的模型,研究了HSA与全氟丙酸复合物在水溶液中的稳定性以及在结合位点中的动力学性质。在模拟人体生理的实验条件下,采用荧光光谱法和同步荧光光谱法研究了HSA与IPCPFFA-3的相互作用。实验结果表明,IPC-PFFA-3与HSA形成的复合物HSA-IPC-PFFA-3对HSA产生荧光猝灭作用,其猝灭机理是静态猝灭;热力学参数计算得出两者结合的主要作用力为氢键作用力;竞争实验的结果表明IPC-PFFA-3与HSA的结合位点位于HSA的SiteⅡ,与分子对接的模拟结果相吻合。同步荧光光谱实验与动力学模拟的结果证明IPC-PFFA-3与HSA能够稳定结合,并使HSA的构象发生变化。     

烟碱与人血清蛋白相互作用的光谱研究

在0.1 mol/L的磷酸氢二钠-柠檬酸体系中,采用荧光光谱、紫外吸收光谱研究了人血清蛋白与烟碱的相互作用.荧光滴定表明这种相互作用使HSA的内源荧光猝灭.通过猝灭常数、结合常数和结合位点数的计算,证明了这种猝灭为静态猝灭机制.尼古丁和HSA形成11稳定复合物;考察不同温度和酸度下的猝灭作用,进一步证实其静态猝灭行为和疏水作用机制.紫外吸收光谱和同步荧光光谱表明,相互作用引起HSA构象变化,而同步荧光光谱提示结合位点更接近于色氨酸.     

2,3,3'-三氯联苯与人血清白蛋白之间相互作用的计算模拟及光谱研究

利用分子对接、分子动力学模拟、荧光光谱、紫外光谱及同步荧光光谱法研究了2,3,3'-三氯联苯(PCB-20)与人血清白蛋白(HSA)的相互作用。分子对接结果表明,PCB-20与HSA通过疏水作用力稳定结合于HSA的疏水空腔内。光谱法实验结果表明,PCB-20通过与HSA形成HSA-PCB20复合物从而对HSA具有荧光猝灭作用,猝灭原因是静态猝灭和非辐射能量转移,热力学参数也表明两者结合的主要驱动力为疏水作用力,计算模拟与实验结果吻合度较高。分子动力学模拟结果表明,PCB-20能够与HSA稳定结合,且与同步荧光光谱实验共同证明其对HSA的构象变化产生了一定影响。     

吡虫啉与人血清白蛋白相互作用热力学行为

在模拟人体生理条件下,综合利用荧光光谱、紫外吸收光谱、圆二色谱和分子模拟等方法,研究了吡虫啉(IMI)和人血清白蛋白(HSA)相互作用的热力学行为。荧光光谱和紫外吸收光谱的分析表明：吡虫啉能有效猝灭HSA的内源荧光,猝灭机制为静态猝灭;通过所获取的相互作用热力学参数,可知两者之间的相互作用是一个吉布斯自由能降低的自发过程,且二者之间的主要作用力为氢键和范德华力。位点竞争实验和分子模拟的结果表明：吡虫啉在HSA的主要结合位置为位点?。圆二色谱、同步荧光光谱和三维荧光的分析发现：吡虫啉引起HSA的构象发生改变,其α-螺旋含量降低,无规卷曲含量升高,肽链结构在吡虫啉的作用下有所伸展。     

2,3,3′-三氯联苯与人血清白蛋白之间相互作用的计算模拟及光谱研究

利用分子对接、分子动力学模拟、荧光光谱、紫外光谱及同步荧光光谱法研究了2,3,3′-三氯联苯(PCB-20)与人血清白蛋白(HSA)的相互作用。分子对接结果表明,PCB-20与HSA通过疏水作用力稳定结合于HSA的疏水空腔内。光谱法实验结果表明,PCB-20通过与HSA形成HSA-PCB20复合物从而对HSA具有荧光猝灭作用,猝灭原因是静态猝灭和非辐射能量转移,热力学参数也表明两者结合的主要驱动力为疏水作用力,计算模拟与实验结果吻合度较高。分子动力学模拟结果表明,PCB-20能够与HSA稳定结合,且与同步荧光光谱实验共同证明其对HSA的构象变化产生了一定影响。     

水溶性阳离子型吡啶基咔咯镓配合物与人血清蛋白的相互作用

利用紫外吸收光谱、荧光光谱、圆二色(CD)光谱和分子对接计算探究了5,10,15-三[4-(N-甲基-吡啶)]咔咯镓配合物(1-Ga)与人血清蛋白(HSA)的相互作用.结果表明,HSA的荧光能被1-Ga静态猝灭,两者的结合常数为2.82×104L/mol,作用距离为3.342 nm.热力学参数显示1-Ga主要通过氢键和疏水作用与HSA结合,位点标记竞争实验表明1-Ga优先结合HSA的布洛芬位点Ⅱ.此外,紫外吸收光谱和CD光谱显示二者的相互作用会导致HSAα-螺旋结构的减少.分子对接计算结果表明1-Ga优先结合在HSA亚结构域ⅢA的位点Ⅱ疏水袋中.     

苦参碱Fe(Ⅲ)化合物的合成及其与HSA相互作用的光谱研究

采用具有天然抗肿瘤活性的药物苦参碱为配体,与Fe(III)反应得到黄色的离子型苦参碱Fe(III)化合物[H-Matrine][FeCl4],用X射线单晶衍射分析法确定了配合物的结构,并在模拟生理条件下,利用紫外光谱法、荧光光谱法、同步荧光光谱和圆二色谱法研究了化合物[H-Matrine][FeCl4]与人血清白蛋白(HSA)的相互作用。结果表明:[H-Matrine][FeCl4]对HSA的荧光产生猝灭作用,猝灭机制为静态猝灭;[H-Matrine][FeCl4]与HSA在不同温度下的结合常数K和结合位点数n,及其相关热力学参数ΔH、ΔG、ΔS,室温时分别为:1.03×106L·mol-1、1.24、-68.63KJ·mol、-34.30KJ·mol和114.05J·mol,且其相互作用力主要是静电作用力。同步荧光光谱的结果表明:[H-Matrine][FeCl4]与HSA的结合位点靠近色氨酸,并使色氨酸的疏水性减弱。     

黄腐酸与人血清白蛋白相互作用机制的光谱研究

利用荧光光谱研究了黄腐酸与HSA的相互作用,黄腐酸对HSA有明显的荧光猝灭作用,计算了黄腐酸与HSA作用的结合常数(Ka=1.2×107L/mol)、结合位点数(n=1.45)及结合距离(r0=2.92 nm)。黄腐酸与HSA的猝灭机制属于静态猝灭,并发生了分子内非辐射能量转移,能量从HSA向黄腐酸转移。同时,通过圆二色谱探讨了黄腐酸对HSA构象的影响,HSA与黄腐酸结合后引起了HSA肽链收缩,改变了HSA的二级结构,使HSA的结构变得更加紧密。     

芘与人血清白蛋白和牛血清白蛋白结合位点微环境极性的差异

利用芘(Pyr)的微环境极性探针性质, 采用稳态荧光光谱、 荧光共振能量转移技术结合分子对接法, 对比分析了Pyr分别与人血清白蛋白(HSA)和牛血清白蛋白(BSA)作用机制的差异. 结果表明, HSA和BSA中Pyr的I₁/I₃平均值分别为1.36和0.92; Pyr与HSA和BSA的结合常数分别为1.86×10⁷和1.71×10⁵ L/mol; Pyr与HSA和BSA中色氨酸残基表观距离分别为2.37和2.34 nm. Pyr在HSA和BSA中不同的结合位点位于ⅠB子域和ⅠA子域, 其结合位点周围氨基酸残基的极性是影响Pyr I₁/I₃值的主要原因之一. 实验证实Pyr与HSA和BSA结合作用位点处的微环境极性存在差异.     

New transition metal complexes of 9,10‐phenanthrenequinone p‐toluyl hydrazone Schiff base: Synthesis,spectroscopy, DNA and HSA interactions,antimicrobial, DFT and docking studies

The new complexes of Cu (II) and Ni (II) of a tridentate Schiff base ligand derived from 9,10‐phenanthrenequinone and p‐toluic hydrazide have been synthesized and characterized by elemental analysis, electrical conductometry, FT‐IR, Mass, NMR and UV–Vis. The DFT calculations were carried out at B3LYP/6‐31G*(d) level for the determination of the optimized structure of the ligand and its complexes. The as‐synthesized compounds were screened for their antimicrobial activity. Also, their binding behavior with fish salmon‐DNA (FS‐DNA) and human serum albumin (HSA) were studied by different kinds of spectroscopic and molecular modeling techniques. The fluorescence data at different temperatures were applied in order to estimate the thermodynamics parameters of interactions of ligand and its complexes with DNA and HSA. The results showed that the as‐made compounds could bind to FS‐DNA and HSA via the groove binding as the major binding mode. According to molecular docking calculation and competitive binding experiments, these compounds bind to the minor groove of DNA and hydrophobic residues located in the subdomain IB of HSA. In addition, the molecular docking results kept in good consistence with experimental data.     

Binding Studies of AICAR and Human Serum Albumin by Spectroscopic,Theoretical, and Computational Methodologies

The interactions of small molecule drugs with plasma serum albumin are important because of the influence of such interactions on the pharmacokinetics of these therapeutic agents. 5-Aminoimidazole-4-carboxamide ribonucleoside (AICAR) is one such drug candidate that has recently gained attention for its promising clinical applications as an anti-cancer agent. This study sheds light upon key aspects of AICAR’s pharmacokinetics, which are not well understood. We performed in-depth experimental and computational binding analyses of AICAR with human serum albumin (HSA) under simulated biochemical conditions, using ligand-dependent fluorescence sensitivity of HSA. This allowed us to characterize the strength and modes of binding, mechanism of fluorescence quenching, validation of FRET, and intermolecular interactions for the AICAR–HSA complexes. We determined that AICAR and HSA form two stable low-energy complexes, leading to conformational changes and quenching of protein fluorescence. Stern–Volmer analysis of the fluorescence data also revealed a collision-independent static mechanism for fluorescence quenching upon formation of the AICAR–HSA complex. Ligand-competitive displacement experiments, using known site-specific ligands for HSA’s binding sites (I, II, and III) suggest that AICAR is capable of binding to both HSA site I (warfarin binding site, subdomain IIA) and site II (flufenamic acid binding site, subdomain IIIA). Computational molecular docking experiments corroborated these site-competitive experiments, revealing key hydrogen bonding interactions involved in stabilization of both AICAR–HSA complexes, reaffirming that AICAR binds to both site I and site II.     

Revealing the ionization ability of binding site I of human serum albumin using 2-(2'-hydroxyphenyl)benzoxazole as a pH sensitive probe

The ability of site I of human serum albumin (HSA) to bind medium sized molecules is important for the distribution, metabolism, and efficacy of many drugs. Herein, we show that this binding site has the ionization ability that may alter the drug structure during the process of its delivery. We reveal this ability by employing 2-(2'-hydroxyphenyl)benzoxazole (HBO) as a pH sensitive probe. Binding of HBO in site I is studied here at physiological pH 7.2 using steady-state and lifetime spectroscopic measurements, molecular docking and molecular dynamics (MD) simulation methods. The complex photophysics of HBO and the unique fluorescence signature of its anionic form indicate that, upon binding with HSA, the molecule exists in equilibrium between the anionic and the syn-keto forms. The position of HBO inside the binding site was determined experimentally by measuring the fluorescence quenching of W214, the sole tryptophan residue in HSA. The ionization degree of HBO inside the binding site was estimated to be close to the ionization degree of HBO in an aqueous solution of pH 10. This was concluded by comparing the fluorescence behavior of bound HBO to that of HBO in different solvents and in aqueous solutions of different pH values. Molecular docking and MD simulations show that HBO binds in site I close to W214, confirming the experimental results, and pinpoint the dominant role of hydrophobic interactions in the binding site. The formation of the anionic form is proposed to be due to through-space interaction between the OH group of HBO and both R222 and I290 with a binding mode similar to that of warfarin in site I. Comparison of the results with those of HBO mixed with key amino acids in solution indicates the importance of through-space interaction in the formation of the anion, similar to enzymatic reactions.     

甲基橙皮苷和人血清白蛋白相互作用的光谱研究

利用荧光光谱法和红外光谱法研究了甲基橙皮苷(MH)与人血清白蛋白(HSA)的相互作用.结果表明,MH对HSA的荧光有较强的猝灭作用.在296、303、310K温度下,MH与HSA相互作用的结合常数分别为1.77×104,2.65×104,3.53×104 L·mol-1.热力学分析结果表明,MH与HSA之间的结合过程是吸热的并且是自发的;作用力以疏水作用为主,并伴随氢键作用.     

两种组氨酸酰胺衍生物的合成及其与人血清白蛋白的结合

L-组氨酸对生物有机体有着良好的亲和能力,通过修饰其化学结构以期寻找药理活性和生物利用度高的衍生物。本文将L-组氨酸分别与反式肉桂酸和对甲氧基肉桂酸反应,合成了两种组氨酸酰胺类衍生物,利用傅里叶变换红外光谱、质谱、氢谱/碳谱核磁共振谱进行了结构表征。采用分子操作环境(MOE)软件分子对接技术、荧光光谱法、同步荧光光谱法(SFS)、紫外-可见光谱法(UV-Vis),共同研究了两种衍生物分别和人血清白蛋白(HSA)相结合的机理。MOE对接结果显示,这两种衍生物与HSA的模拟结合能分别为-13.82和-16.25 kcal/mol,主要是通过范德华力和疏水作用结合在HSA亚结构域ⅡA(即siteⅠ)的疏水腔内。荧光猝灭数据表明,衍生物与HSA相互作用并形成了新的基态配合物,荧光猝灭过程为静态猝灭;不同温度(300、305和310 K)下衍生物与HSA相互作用的结合常数分别为1.773×104、6.354×10~3、1.260×10~3和5.314×10~4、4.614×10~3、1.420×10~3;由热力学参数得到衍生物与HSA的结合过程是由范德华力驱动;SFS表明,衍生物使得HSA的二级结构发生了变化。结合UV-Vis的结果可以确定,在体外生理条件下,组氨酸酰胺类衍生物均可以通过范德华力与HSA结合,并对HSA内源荧光产生静态猝灭及构象影响,这与分子对接结果一致,从而为组氨酸酰胺类衍生物药物的进一步开发提供了参考。     

Mechanistic Insight into Binding of Huperzine A with Human Serum Albumin: Computational and Spectroscopic Approaches

Human serum albumin (HSA) is the most abundant protein in plasma synthesized by the liver and the main modulator of fluid distribution between body compartments. It has an amazing capacity to bind with multiple ligands, offering a store and transporter for various endogenous and exogenous compounds. Huperzine A (HpzA) is a natural sesquiterpene alkaloid found in Huperzia serrata and used in various neurological conditions, including Alzheimer’s disease (AD). This study elucidated the binding of HpzA with HSA using advanced computational approaches such as molecular docking and molecular dynamic (MD) simulation followed by fluorescence-based binding assays. The molecular docking result showed plausible interaction between HpzA and HSA. The MD simulation and principal component analysis (PCA) results supported the stable interactions of the protein–ligand complex. The fluorescence assay further validated the in silico study, revealing significant binding affinity between HpzA and HSA. This study advocated that HpzA acts as a latent HSA binding partner, which may be investigated further in AD therapy in experimental settings.     

Interaction Between Toddalolatone and Human Serum Albumin

A combination of fluorescence, UV–Vis absorption, circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopic and molecular modeling approaches was employed to investigate the interaction between toddalolactone (TDT) and human serum albumin (HSA) at physiological buffer conditions (pH 7.4). Fluorescence titration suggests that the mechanism of the fluorescence quenching of HSA is static, resulting from the formation of a TDT–HSA complex. Binding parameters calculated from the modified Stern–Volmer equation show that TDT binds to HSA with high affinity. Negative enthalpy change and positive entropy change values suggest that the binding process is primarily driven by hydrophobic interactions and hydrogen bonds. The binding of TDT to HSA results in an increase in the surface hydrophobicity of HSA. The binding distance between the Trp-214 residue (donor) and TDT (acceptor) was determined to be 4.18 nm based on the Förster theory of non-radioactive energy transfer. Displacement studies of site markers reveal that the binding site of TDT to HSA is located in the subdomain IIA (Sudlow’s site I). Furthermore, the molecular docking results corroborate and illustrate the specific binding mode and binding site. Analysis of UV–Vis absorption, CD and FT-IR spectra demonstrated that TDT induced a small alteration of the protein’s conformation.     

Characterization of the interaction between a platinum(II) complex and human serum albumin: spectroscopic analysis and molecular docking

In this study, the interaction between (2,2?-bipyridine)(pyrrolidinedithiocarbamato) platinum(II) nitrate, [Pt(bpy)(pyr-dtc]NO₃, and human serum albumin (HSA) was investigated by various spectroscopic methods (UV–vis, fluorescence, CD and FT-IR) and molecular docking technique at three temperatures. UV–vis absorption spectroscopy showed that Pt(II) complex can denature the protein at moderate concentrations. The results of emission quenching at two temperatures has revealed that the quenching mechanism of Pt(II) complex with HSA was static quenching mechanism. Binding constants (K), binding site number (n) and corresponding thermodynamic parameters ?G?, ?H? and ?S? were calculated and revealed that hydrophobic forces played a major role when Pt(II) complex interacted with HSA. The binding distance (r) between above complex and HSA based on Förster?s theory of non-radiation energy transfer was calculated as 3.22 nm. Alterations of HSA secondary structure induced by complex were confirmed by FT-IR and CD measurements. Also, a molecular docking study was performed for identification of key structural features of binding of the Pt complex into the receptor and predicting bioactive conformers. Our results may provide valuable information to understand the mechanistic pathway of drug delivery and to pharmacological behavior of drug.