In vitro study on the interaction between thiophanate methyl and human serum albumin

Thiophanate methyl (MT) is one of the widely used fungicides to control important fungal diseases of crops, which has led to potential toxicological risk to public health. Several different transport proteins exist in blood plasma, but albumin only is bound by a wide diversity of xenobiotics reversibly with high affinity. We studied the interaction of MT with human serum albumin by using spectroscopic methods including fluorescence quenching technology, UV and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The result of fluorescence titration revealed that MT could quench the intrinsic fluorescence of HSA. The binding process was exothermic and spontaneous, as indicated by the thermodynamic analyses. In addition, the studies of FT-IR spectroscopy showed that the binding of MT to HSA changed molecular conformation of HSA. The results obtained from molecular modeling showed that the interaction between MT and HSA was dominated by hydrophobic force, and there was also hydrogen bond interaction between the pesticide and the residues of HSA, which was in good agreement with the result of binding mode.     

Synthesis and characterization of lanthanide complexes of DO3A-alkylphosphonates

Eight DO3A-based lanthanide(III) complexes bearing ester protected and unprotected phosphonate groups at variable distances from the macrocyclic moiety have been synthesized and analyzed. The ligands were made by straightforward four-step synthetic procedures and purified with preparative RP-HPLC, after which they were used to prepare gadolinium(III) and europium(III) complexes. Relaxometric experiments were performed on the Gd(III) complexes at 300 MHz, varying the pH of the solutions or the concentration of human serum albumin (HSA). It was found that when the pH of the medium was changed from neutral to pH 4 the longitudinal relaxivity of GdDO3A-ethylphosphonate and GdDO3A-propylphosphonate complexes increased by 50% and 60%, respectively. Diethyl esters of these complexes did not change longitudinal relaxivity in the same pH range but their transverse relaxivity increased upon binding to HSA. 31P NMR experiments on Eu(III) complexes showed a change in the chemical shift of both acid complexes in the same region where the highest relaxivity changes were observed and proved the stability of the complexes in the investigated pH range, while no shift was observed for the diester complexes. Luminescence studies on europium(III) complexes additionally supported observations obtained by NMR methods. The change in the form of the luminescence emission spectra, and the reduction in the q value upon addition of HSA proved the ternary adduct formation between the charge neutral diester complexes and HSA. Similarly, the change in the emission spectra showing a phosphonate bound structure at pH 7 to a species where the phosphonate oxygen is not coordinated at pH 4 in parallel with the increase of q value is supporting the hypothesis that the deprotonation of phosphonates is the main reason for the distinct relaxivity change from slightly acidic to the neutral solution media.     

Enantioselective binding of a lanthanide(III) complex to human serum albumin studied by 1H STD NMR techniques

The enantioselective binding of the (SSS)-Δ isomer of an yttrium(III) tetraazatriphenylene complex to 'drug-site II' of human serum albumin (HSA) was detected by the intensity differences of its STD (1)H NMR spectrum relative to the (RRR)-Λ isomer, by the effect of the competitive binder to that site, N-dansyl sarcosine, upon the STD spectrum of each isomer, in the presence of HSA and by 3D docking simulations.     

In situ circular dichroic electrochemical study of bilirubin and bovine serum albumin complex

The electrooxidation of bilirubin (BR) and bovine serum albumin (BSA) complexes was studied by in situ circular dichroism (CD) spectroelectrochemistry. The result showed that the mechanism of the whole electrooxidation process of this complex corresponded to electrochemical processes (EE mechanism) in aqueous solution. Some parameters of the process were obtained by double logarithm method, differential method and nonlinear regression method. In visible region, CD spectra of the two enantiomeric components of the complex and their fraction distribution against applied potentials were obtained by singular value decomposition least-square (SVDLS) method. Meanwhile, the distribution of the five components of secondary structure was also obtained by the same method in far-UV region. The peak potential gotten from EE mechanism corresponds to a turning point for the component transition, beyond which the whole reaction reaches a new equilibrium. Under applied positive potentials, the enantiomeric equilibrium between M and P form is broken and M form transfers to its enantiomer of P, while the fraction of alpha-helix increases and that improves the transition to P form.     

Noncovalent interactions between a trinuclear monofunctional platinum complex and human serum albumin

Interactions between platinum complexes and human serum albumin (HSA) play crucial roles in the metabolism, distribution, and efficacy of platinum-based anticancer drugs. Polynuclear monofunctional platinum(II) complexes represent a new class of anticancer agents that display distinct molecular characters of pharmacological action from those of cisplatin. In this study, the interaction between a trinuclear monofunctional platinum(II) complex, [Pt(3)LCl(3)](ClO(4))(3) (L = N,N,N',N',N",N"-hexakis(2-pyridylmethyl)-1,3,5-tris(aminomethyl)benzene) (1), and HSA was investigated using ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, circular dichroism spectroscopy, fluorescence spectroscopy, molecular docking, and inductively coupled plasma mass spectrometry. The spectroscopic and thermodynamic data show that the interaction is a spontaneous process with the estimated enthalpy and entropy changes being 14.6 kJ mol(-1) and 145.5 J mol(-1) K(-1), respectively. The reactive sites of HSA to complex 1 mainly locate within its hydrophobic cavity in domain II. Noncovalent actions such as π-π stacking and hydrophobic bonding are the primary contributors to the interaction between HSA and complex 1, which is different from the scenario for cisplatin in similar conditions. The results suggest that the connection between complex 1 and HSA is reversible, and therefore the cytotoxic activity of the complex could be preserved during blood circulation.     

磺化酞菁与人血清白蛋白复合物的光动力活性研究

通过光谱法研究了三种磺化酞菁(α位四磺化酞菁、β位四磺化酞菁和α位单取代磺化酞菁)与人血清白蛋白(HSA)的相互作用.结果 表明,HSA对α位四磺化酞菁的存在状态(单体、聚集体)影响显著,而对β位四磺化酞菁和α位单取代磺化酞菁的存在状态没有明显影响.磺化酞菁与HSA均存在明显的相互作用,且.四磺化酞菁与HSA的结合作用...     

In vitro evaluation of potential complexation between bovine insulin and bovine serum albumin

The objective of this study was to examine the possible binding of bovine insulin (BI) with bovine serum albumin (BSA) to form a new potential diabetogenic irreversible complex protein. Several preparations of BSA and BI were prepared. Both capillary electrophoresis and spectrophotometric analysis were undertaken to test the possibility of complexation between BI and BSA. HPLC was used to test whether the potential complex of BI and BSA is reversible or irreversible. The optimum deviation between the real and calculated absorbances was observed at a BI/BSA ratio of 2. Moreover, the migration time of BI decreased substantially with increasing ratio of BI to BSA until it became almost constant at equal molar ratio of BI/BSA. While the majority of the 2:1 BI–BSA sample detached during the HPLC analysis, which confirms the reversible character of BI–BSA binding, the HPLC chromatogram also emphasizes the formation of an irreversible complexation between the two proteins. This study provides evidence of the formation of reversible and irreversible new BI–BSA complexes under physiological conditions. This highlights the importance of examining the possible diabetogenicity of BI–BSA complex in genetically susceptible people. Copyright © 2013 John Wiley & Sons, Ltd.     

铈配合物与人血清白蛋白相互作用的研究

在生理条件(pH=7.4)下,利用荧光光谱和紫外光谱探讨了华法灵铈与人血清白蛋白(HSA)的相互作用。根据荧光和紫外光谱可知,华法灵铈配合物对人血清白蛋白荧光产生猝灭作用,其猝灭方式为静态猝灭。并通过Stern-Volmer方程等,计算出了配合物与人血清白蛋白的静态猝灭常数、结合常数和结合位点数。根据一系列热力学参数ΔH,ΔS,ΔG的相对大小,确定出配合物与人血清白蛋白的主要作用力类型为静电作用力。且用同步荧光法讨论了华法灵铈对HSA构象的影响。     

In vitro study on the binding of herbicide glyphosate to human serum albumin by optical spectroscopy and molecular modeling

In this study, the interaction mechanism of herbicide glyphosate and human serum albumin (HSA) has been characterized by fluorescence, UV, Fourier transform infrared (FT-IR), Circular dichroism (CD) spectroscopic and molecular modeling methods. The structural characteristics of glyphosate and HSA were probed, and affinity constants were determined under different temperatures. The enthalpy change (DeltaH degrees ) and the entropy changes (DeltaS degrees ) were calculated to be -21.78kJmol(-1) and 6.38Jmol(-1)K(-1) according to the Van't Hoff equation. These results indicated that glyphosate binds to HSA mainly by hydrogen bond and hydrophobic interaction can also not be excluded, which is in good agreement with the results from modeling experiment. The average binding distance, r, between the donor (HSA) and the acceptor (glyphosate) was evaluated and found to be 2.89nm according to the F?rster's theory of non-radiation energy transfer. The alterations of protein secondary structure in the presence of glyphosate were confirmed by the evidences from UV, FT-IR and CD spectroscopes.     

Synthesis of lanthanide(III) complexes appended with a diphenylphosphinamide and their interaction with human serum albumin

Two DOTA-based proligands bearing a pendant diphenylphosphinamide 4a and 4b were synthesised. Their Eu(III) complexes exhibit sensitised emission when excited at 270 nm via the diphenylphosphinamide chromophore. Hydration states of q = 1.5 were determined from excited state lifetime measurements (Eu.4a $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 2. 1 4 \,{\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 0. 6 4 \,{\text{ms}}^{ - 1} $ ; Eu.4b $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 2. 6 7\, {\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 1. 1 8 \,{\text{ms}}^{ - 1} $ ). In the presence of human serum albumin (HSA) (0.1 mM Eu.4a/b, 0.67 mM HSA, pH 7.4) q = 0.4 for Eu.4a ( $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 1. 3 4\, {\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 0. 7 5\, {\text{ms}}^{ - 1} $ ) and q = 0.6 for Eu.4b ( $ k_{{{\text{H}}_{ 2} {\text{O}}}} = 1. 8 3\, {\text{ms}}^{ - 1} ,\;k_{{{\text{D}}_{ 2} {\text{O}}}} = 1.0 5 \,{\text{ms}}^{ - 1} $ ). Relaxivites (pH 7.4, 298 K, 20 MHz) of the Gd(III) complexes in the absence and presence of HSA (0.1 mM Gd.4a/b, 0.67 mM HSA) were: Gd.4a (r ₁ = 7.6 mM^?1s^?1 and r ₁ = 11.7 mM^?1s^?1) and Gd.4b. (r ₁ = 7.3 mM^?1s^?1 and r ₁ = 16.0 mM^?1s^?1). These relatively modest increases in r ₁ are consistent with the change in inner-sphere hydration on binding to HSA shown by luminescence measurements on Eu.4a/b. Binding constants for HSA determined by the quenching of luminescence (Eu) and enhancement of relaxivity (Gd) were Eu.4a (27,000 M^?1 ± 12%), Eu.4b (32,000 M^?1 ± 14%), Gd.4a (21,000 M^?1 ± 15%) and Gd.4b (26,000 M^?1 ± 15%).     

Binding of glycyrrhizin to human serum and human serum albumin

The binding of glycyrrhizin (GLZ) to human serum and human serum albumin (HSA) was examined by an ultrafiltration technique. Specific and nonspecific bindings were observed in both human serum and HSA. The association constants (K) for the specific bindings were very similar: 1.31 x 10(5) M-1 in human serum and 3.87 x 10(5) M-1 in HSA. The number of binding sites (n) and the linear binding coefficient (phi) in HSA were 1.95 and 3.09 x 10(3) M-1, respectively. When the human serum protein concentration was assumed to be 4.2% (equal to the measured serum albumin concentration), n in human serum was 3.09, which is similar to the n value in HSA, and phi in human serum was 0.71 x 10(3) M-1, which is reasonably close to that for HSA. The binding pattern of GLZ with human serum protein on Sephadex G-200 column chromatography showed that GLZ binds to only the albumin fraction. It was concluded that the GLZ-binding sites in human serum exist mainly on albumin and GLZ binds to specific and nonspecific binding sites at lower and higher concentrations than approximately 2 mM, respectively.     

人血清白蛋白与Cu(II)配合物的生物活性研究

Cu(II)配合物很有可能成为下一代的抗肿瘤药物。本文以2-氨基-5-氯苯酚和2-喹啉甲醛合成的席夫碱作为配体,与Cu(II)络合形成配合物1。分别对配合物1和其与人血清白蛋白(HSA)的复合物HSA-1进行体外抗肿瘤测试,发现HSA能提高配合物1的抗肿瘤活性,并降低了对正常细胞的毒性。通过线粒体膜电位等实验,可以推断出配合物1是通过线粒体通路诱导癌细胞凋亡。     

Fluorimetric study of the interaction between human serum albumin and quinolones-terbium complex and its application

A highly sensitive spectrofluorimetric method is proposed for determination of human serum albumin (HSA) and some quinolone drugs. Using quinolones-terbium (Tb3+) complex as a fluorescent probe, in the buffer solution of pH 7.8, HSA can remarkably enhance the fluorescence intensity of the quinolones-Tb3+ complex at 545 nm and the enhanced fluorescence intensity of Tb3+ ion is in proportion to the concentration of HSA and quinolone drugs. Optimum conditions for the determination of HSA were also investigated. The linear ranges and limits of detection are 8.0 x 10(-9) to 8.0 x 10(-8) mol L(-1), 4.20 x 10(-9) mol L(-1) (for HSA); 1.0 x 10(-6) to 4.0 x 10(-6) mol L(-1), 1.87 x 10(-8) mol L(-1) (for norfloxacin) and 1.0 x 10(-7) to 1.0 x 10(-6) mol L(-1), 4.82 x 10(-8) mol L(-1) (for enoxacine), respectively. This method is simple, practical and relatively free interference from coexisting substances, as well as much more sensitive than most of the existing assays.     

A binaphthyl-containing Eu(III) complex and its interaction with human serum albumin: a luminescence study

On binding to human serum albumin (HSA), the Eu(III) luminescent emission enhancement of a complex containing a binaphthyl chromophore enables the determination of binding constants, showing no chiral discrimination for the (R)- (K= 8200 +/- 810 M(-1)) and (S)-enantiomers (K= 7710 +/- 460 M(-1)).     

A novel TICT-based near-infrared fluorescent probe for light-up sensing and imaging of human serum albumin in real samples

Human serum albumin (HSA) has emerged as a pivotal biomarker and prognostic indicator for various human diseases. Real-time sensing and visual tracking of HSA in plasma or other biological systems will immensely facilitate the basic researchers and clinicians to better understand HSA-associated biological processes. Herein, a novel near-infrared (NIR) fluorescent probe (7-HTCF) was rationally constructed for light-up sensing and in-situ imaging of HSA in real samples, based on the principle of twisted intramolecular charge transfer (TICT). Under physiological conditions, 7-HTCF could be efficiently trapped by HSA to form a stable complex via binding on a non-drug binding site, while the complex emitted strong fluoresce signals around 670 nm. Further investigations demonstrated that 7-HTCF displayed a great combination of excellent selectivity and good chemical stability, as well as rapid fluorescent response and ultra-high sensitivity for HSA detection. Particularly, the newly developed light-up probe has been successfully utilized for quantitative detection of HSA in diluted plasma samples, while its readouts are hardly affected by the addition of therapeutic agents and herbal medicines. 7-HTCF is also successfully used for in-situ imaging of the reabsorbed HSA in living renal cells, while this dye exhibits good cell permeability and high resolution for in-situ imaging in living cells. Collectively, a novel TICT-based near-infrared fluorescent probe was devised for highly selective and ultra-sensitive sensing of HSA in plasma samples or imaging HSA in living cells, which offered a practical tool for clinical tests and for exploring HSA-associated biological processes.     

A dimeric luminescent lanthanide complex [Eu(PAA)2(phen)(NO3)]2: hydrothermal synthesis,crystal structure and fluorescence

A lanthanide coordination complex [Eu(PAA)₂(phen)(NO₃)]₂ (PAA?=?phenylacetic acid, phen?=?1,10-phenanthroline) has been synthesized by the hydrothermal method. Single crystal X-ray diffractions show that it forms a dimeric molecular structure. The title complex crystallizes in the triclinic system, space group P 1, with lattice parameters a?=?8.9473(8)?Å, b?=?13.3659(12)?Å, c?=?13.4745(12)?Å, α?=?60.7590(10)°, β?=?89.5100(10)°, γ?=?71.9850(10)°, V?=?1317.3(2)?ų, D _c?= 1.675?Mg?m^?3, Z?=?1, F(000)?=?660, GOF?=?1.003, R ₁?=?0.0206, wR ₂?=?0.0575. The fluorescence excitation and emission spectra have been investigated.