Thermodynamic Studies of Myelin Basic Protein upon Interaction with Zinc

The interaction of myelin basic protein (MBP) from bovine central nervous system with divalent zinc ion was studied by UV‐Vis titration spectrophotometry and isothermal titration calorimetry techniques at 27°C in Tris buffer solution at pH = 7.2. MBP has one binding site for a zinc ion. The binding of a zinc ion is endothermic (ΔH = + 159 kJ mol^?1) with a dissociation binding constant of 0.445 μM. The results obtained by two previous methods of isothermal titration spectrophotometry and calorimetry are similar and consistent with the result obtained from a new calculation method of calorimetric data analysis according to the Scatchard plot.     

A Thermodynamic Study on the Binding of Calcium Ion with Myelin Basic Protein

The interaction of myelin basic protein (MBP) from the bovine central nervous system with divalent calcium ion was studied by isothermal titration calorimetry at 27 °C in aqueous solution. The extended solvation model was used to reproduce the enthalpies of Ca²⁺-MBP interaction over the whole range of Ca²⁺ concentrations. The solvation parameters recovered from the solvation model were attributed to the structural change of MBP due to the metal ion interaction. It was found that there is a set of two identical and non-interacting binding sites for Ca²⁺ ions. The association equilibrium constant is 0.021 μmol⋅dm⁻³. The molar enthalpy of binding is ΔH=−15.10 kJ⋅mol⁻¹.     

A thermodynamic investigation on the binding of mercury ion with myelin basic protein at different temperatures

A thermodynamic study on the interaction of myelin basic protein with mercury ion was studied by using isothermal titration calonmetry,ITC,at 300.15,310.15 and 320.15 K in Tris buffer solution at pH 7.The enthalpies of MBP + Hg²⁺ interaction are reported and analysed in terms of the extended solvation model.It was found that MBP has two identical and non-cooperative binding sites for Hg²⁺ ions.The intrinsic dissociation equilibrium constants are 99.904,112.968 and 126.724μmol/L,and the molar enthalpy of binding are -11.634,-10.768 and -10.117kJ mol^-1 at 300.15,310.15 and 320.15 K,respectively.     

A New Approach for Titration Calorimetric Data Analysis on the Binding of Magnesium Ion with Myelin Basic Protein

The interaction of the myelin basic protein (MBP) from the bovine central nervous system with divalent magnesium ion was studied by isothermal titration calorimetry at 27 °C in aqueous solution. A simple rapid method for determination of the dissociation binding constants for Mg²⁺-MBP interaction was introduced using the isothermal titration calometric data. The binding isotherm for Mg²⁺-MBP interaction is easily obtained by carrying out a titration calorimetric experiment using only one set of concentrations of MBP. There are two identical independent intrinsic association constants equal to 0.021 μmol⋅L⁻¹ in the first- and second-binding sites, respectively.     

Application of an extended solvation theory to study on the binding of magnesium ion with myelin basic protein

Binding properties of myelin basic protein (MBP) from bovine central nervous system due to the interaction by divalent magnesium ion (Mg²⁺) was investigated at 27°C in aqueous solution using isothermal titration calorimetry (ITC) technique. An extended solvation model was used to reproduce the enthalpies of Mg²⁺-MBP interaction over the whole Mg²⁺ concentrations. It was found that there is a set of two identical and noninteracting binding sites for Mg²⁺ ions. The dissociation equilibrium constant is K _d=45.5 μM. The molar enthalpy of binding site is identical for both sites; ΔH=−15.24 kJ mol⁻¹. The solvation parameters recovered from the solvation model were attributed to the structural change of MBP due to the metal ion interaction.     

氧化苦参碱与牛血清白蛋白相互作用的热力学研究

在298.15 K下, 应用等温滴定量热法和圆二色谱法研究了氧化苦参碱(OMT)与牛血清白蛋白(BSA)的相互作用, 并讨论了二者结合过程热力学性质的改变. 研究结果表明, BSA大分子上存在可结合OMT分子的两类位点. OMT分子与第一类位点相结合时, 结合过程的平衡常数、标准摩尔焓变和标准摩尔吉布斯自由能变分别为 ＝(2.14±0.31)×105, ＝(－1.07±0.50) kJ•mol－1, ＝(－30.4±0.4) kJ•mol－1, 最大可结合位点数为 N1＝(10.0±0.2), 该过程是以熵驱动为主的焓熵协同驱动过程. OMT 分子与第二类位点相结合时, ＝(6.84±0.32)×103, ＝(1.91±0.03) kJ•mol－1, ＝(－21.9±0.4) kJ•mol－1, N2＝(25.0±0.3), 该过程是熵驱动过程. 圆二色谱测试结果表明, 两类结合过程中, OMT与BSA的相互作用均导致了蛋白质二级结构构象及不同结构单元相对含量的变化.     

丹皮酚及其两种同分异构体与牛血清白蛋白相互作用的热力学研究

在298.15 K下利用等温滴定微量热法研究了丹皮酚(2'-羟基-4'-甲氧基苯乙酮, Pae)及其两种同分异构体(2'-羟 基-5'-甲氧基苯乙酮, Hma; 4'-羟基-3'-甲氧基苯乙酮, Ace)与牛血清白蛋白(BSA)在缓冲溶液(pH≈7.0)中的相互作用. 从药物分子在蛋白质分子上有多种类型相互独立的结合位点的假定出发, 应用Langmuir吸附模型对这三种同分异构体与 BSA 相互作用的量热数据进行了处理. 结果表明, 有两类结合位点存在, 同时计算出了两类结合模式的结合常数、焓变、熵变及吉布斯自由能变等热力学数据. 这两类结合主要以焓驱动为主, 并且在同一类结合位点上, Pae, Hma以及 Ace与BSA结合过程的焓变绝对值依次减小, 这主要是由于客体分子苯环上取代基的相对位置不同而引起热力学数据的差异. 圆二色谱研究表明这三种同分异构体的加入均使BSA的二级结构发生变化, 说明这种生物大分子-药物分子相互作用既包含结合反应也包含小分子诱导BSA分子部分结构改变的过程.     

A High Performance Theory for Thermodynamic Study on the Binding of Human Serum Albumin with Erbium Chloride

A thermodynamic study of the interaction between erbium(III) chloride (Er3＋) and human serum albumin (HSA) was studied at pH＝7.0, 27 and 37 ℃ in phosphate buffer by isothermal titration calorimetry (ITC). The present study reports the thermodynamic parameters that govern HSA-Er3＋ interactions. The extended solvation theory was used to reproduce the enthalpies of HSA-Er3＋ interactions over the whole range of Er3＋ concentrations. The binding parameters recovered from the new model were attributed to the structural change of HSA and its biological activity. The results obtained indicate that there is a set of two identical binding sites for Er3＋ ions with negative cooperativity. The enhancement of complex formation by Er3＋ and concomitant increase in ∆S suggest that the metal ion plays a role in increasing the number of hydrophobic contacts. The binding parameters discovered from the extended solvation model indicate that the stability of HSA molecule is increased as a result of its interaction with Er3＋ ions.     

Blocking Effect of Demethylzeylasteral on the Interaction between Human ACE2 Protein and SARS-CoV-2 RBD Protein Discovered Using SPR Technology

The novel coronavirus disease (2019-nCoV) has been affecting global health since the end of 2019, and there is no sign that the epidemic is abating. Targeting the interaction between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein and the human angiotensin-converting enzyme 2 (ACE2) receptor is a promising therapeutic strategy. In this study, surface plasmon resonance (SPR) was used as the primary method to screen a library of 960 compounds. A compound 02B05 (demethylzeylasteral, CAS number: 107316-88-1) that had high affinities for S-RBD and ACE2 was discovered, and binding affinities (K_D, μM) of 02B05-ACE2 and 02B05-S-RBD were 1.736 and 1.039 μM, respectively. The results of a competition experiment showed that 02B05 could effectively block the binding of S-RBD to ACE2 protein. Furthermore, pseudovirus infection assay revealed that 02B05 could inhibit entry of SARS-CoV-2 pseudovirus into 293T cells to a certain extent at nontoxic concentration. The compoundobtained in this study serve as references for the design of drugs which have potential in the treatment of COVID-19 and can thus accelerate the process of developing effective drugs to treat SARS-CoV-2 infections.     

Interaction Characterization of a Tyrosine Kinase Inhibitor Erlotinib with a Model Transport Protein in the Presence of Quercetin: A Drug–Protein and Drug–Drug Interaction Investigation Using Multi-Spectroscopic and Computational Approaches

The interaction between erlotinib (ERL) and bovine serum albumin (BSA) was studied in the presence of quercetin (QUR), a flavonoid with antioxidant properties. Ligands bind to the transport protein BSA resulting in competition between different ligands and displacing a bound ligand, resulting in higher plasma concentrations. Therefore, various spectroscopic experiments were conducted in addition to in silico studies to evaluate the interaction behavior of the BSA-ERL system in the presence and absence of QUR. The quenching curve and binding constants values suggest competition between QUR and ERL to bind to BSA. The binding constant for the BSA-ERL system decreased from 2.07 × 10⁴ to 0.02 × 10² in the presence of QUR. The interaction of ERL with BSA at Site II is ruled out based on the site marker studies. The suggested Site on BSA for interaction with ERL is Site I. Stability of the BSA-ERL system was established with molecular dynamic simulation studies for both Site I and Site III interaction. In addition, the analysis can significantly help evaluate the effect of various quercetin-containing foods and supplements during the ERL-treatment regimen. In vitro binding evaluation provides a cheaper alternative approach to investigate ligand-protein interaction before clinical studies.     

Crystal Structure of Isoform CBd of the Basic Phospholipase A2 Subunit of Crotoxin: Description of the Structural Framework of CB for Interaction with Protein Targets

Crotoxin, from the venom of the South American rattlesnake Crotalus durissus terrificus, is a potent heterodimeric presynaptic β-neurotoxin that exists in individual snake venom as a mixture of isoforms of a basic phospholipase A₂ (PLA₂) subunit (CBa₂, CBb, CBc, and CBd) and acidic subunit (CA_1–4). Specific natural mutations in CB isoforms are implicated in functional differences between crotoxin isoforms. The three-dimensional structure of two individual CB isoforms (CBa₂, CBc), and one isoform in a crotoxin (CA₂CBb) complex, have been previously reported. This study concerns CBd, which by interaction with various protein targets exhibits many physiological or pharmacological functions. It binds with high affinity to presynaptic receptors showing neurotoxicity, but also interacts with human coagulation factor Xa (hFXa), exhibiting anticoagulant effect, and acts as a positive allosteric modulator and corrector of mutated chloride channel, cystic fibrosis transmembrane conductance regulator (CFTR), implicated in cystic fibrosis. Thus, CBd represents a novel family of agents that have potential in identifying new drug leads related to anticoagulant and anti-cystic fibrosis function. We determined here the X-ray structure of CBd and compare it with the three other natural isoforms of CB. The structural role of specific amino acid variations between CB isoforms are analyzed and the structural framework of CB for interaction with protein targets is described.     

酮洛芬与蛋白结合作用的高效液相色谱-迎头分析法研究及其与高效毛细管电泳-迎头分析法的比较

采用高效液相色谱-迎头分析法(HPLC-FA),以67 mmol/L (pH 7.4, I=0.17 mol/L) 的等渗磷酸盐缓冲液为流动相,Pinkerton GFF　Ⅱ-S5-80内表面反相柱(150 mm×4.6 mm i.d., 5 μm)为固定相,254 nm下检测,研究了酮洛芬与人血清白蛋白(HSA)的结合作用,通过非线性回归参数估算求得酮洛芬与HSA的结合参数。与高效毛细管电泳-迎头分析法(HPCE-FA)相比,HPLC-FA法具有高灵敏度的优势,但进样量较大,分析时间较长。HPLC-F     

Interaction Structure and Affinity of Zwitterionic Amino Acids with Important Metal Cations (Cd2+, Cu2+, Fe3+, Hg2+, Mn2+, Ni2+ and Zn2+) in Aqueous Solution: A Theoretical Study

Heavy metals are non-biodegradable and carcinogenic pollutants with great bio-accumulation potential. Their ubiquitous occurrence in water and soils has caused serious environmental concerns. Effective strategies that can eliminate the heavy metal pollution are urgently needed. Here the adsorption potential of seven heavy metal cations (Cd²⁺, Cu²⁺, Fe³⁺, Hg²⁺, Mn²⁺, Ni²⁺ and Zn²⁺) with 20 amino acids was systematically investigated with Density Functional Theory method. The binding energies calculated at B3LYP-D3/def2TZVP level showed that the contribution order of amino acid side chains to the binding affinity was carboxyl > benzene ring > hydroxyl > sulfhydryl > amino group. The affinity order was inversely proportional to the radius and charge transfer of heavy metal cations, approximately following the order of: Ni²⁺ > Fe³⁺ > Cu²⁺ > Hg²⁺ > Zn²⁺ > Cd²⁺ > Mn²⁺. Compared to the gas-phase in other researches, the water environment has a significant influence on structures and binding energies of the heavy metal and amino acid binary complexes. Collectively, the present results will provide a basis for the design of a chelating agent (e.g., adding carboxyl or a benzene ring) to effectively remove heavy metals from the environment.