Binding interaction of atorvastatin with bovine serum albumin: Spectroscopic methods and molecular docking

Characterization of the structural and molecular interactions of Ferulic acid ethyl ester with human serum albumin and Lysozyme through multi-methods

Ferulic acid ethyl ester (FAEE) is an essential raw material for the formulation of drugs for cardiovascular and cerebrovascular diseases and leukopenia. It is also used as a fixed aroma agent for food production due to its high pharmacological activity. In this study, the interaction of FAEE with Human serum albumin (HSA) and Lysozyme (LZM) was characterized by multi-spectrum and molecular dynamics simulations at four different temperatures. Additionally, the quenching mechanism of FAEE-HSA and FAEE-LZM were explored. Meanwhile, the binding constants, binding sites, thermodynamic parameters, molecular dynamics, molecular docking binding energy, and the influence of metal ions in the system were evaluated. The results of Synchronous fluorescence spectroscopy, UV-vis spectroscopy, CD, three-dimensional fluorescence spectrum, and resonance light scattering showed that the microenvironment of HSA and LZM and the protein conformation changed in the presence of FAEE. Furthermore, the effects of some common metal ions on the binding constants of FAEE-HSA and FAEE-LZM were investigated. Overall, the experimental results provide a theoretical basis for promoting the application of FAEE in the cosmetics, food, and pharmaceutical industries and significant guidance for food safety, drug design, and development.

Exploring the binding characteristics between lorlatinib and human alpha-1-acid glycoprotein: Multispectral and molecular modeling techniques

Approval in 2019 was granted for the highly selective, targeted agent lorlatinib, which primary target is ROS1 and ALK. The purpose of this work was to examine the binding mechanism between lorlatinib (LOR) and HAG employing multispectral and molecular modeling techniques. Fluorescence data demonstrated that LOR quenched HAG fluorescence as a static quenching, interecalated into the hydrophobic cavity of HAG with a moderate affinity. Thermodynamic and competitive experiments pointed out that LOR bound with HAG primarily through hydrogen bonding, hydrophobic, and van der Waals forces. Circular dichroism, three-dimensional and synchronous fluorescence spectroscopic studies noted that the secondary structure of HAG and microenvironments around tyrosine (Tyr) and tryptophan (Trp) residues were altered due to binding with LOR. The contribution of each energy involved in binding process of LOR and HAG has been analyzed by molecular simulation techniques. Besides, the environmental conditions with metal ions have also been studied. The present study is expected to provide a theoretical basis for further studying the metabolism of LOR in vivo, which may help to gain a deeper understanding of the general pharmacological activity of the drug.

The mechanism of interaction between tri-para-cresyl phosphate and human serum protein: A multispectroscopic and in-silico study

Organophosphate flame retardants (OPFRs) pose the significant risks to the environment and human health and have become a serious public health issue. Tricresyl phosphates (TCPs), a group of aryl OPFRs, exhibit neurotoxicity and endocrine disrupting toxicity. However, the binding mechanisms between TCPs and human serum albumin (HSA) remain unknown. In this study, through fluorescence and ultraviolet-visible (UV-vis) absorption spectroscopy, molecular docking and molecular dynamics (MD), tri-para-cresyl phosphate (TpCP) was selected to explore potential interactions between HSA and TCPs. The results of the fluorescence spectroscopy demonstrated that a decrease in the fluorescence intensity of HSA and a blue shift were observed with the increasing concentrations of TpCP. The binding constant (Ka) was 2.575 × 104 L/mol, 4.701 × 104 L/mol, 5.684 × 104 L/mol and 9.482 × 104 L/mol at 293 K, 298 K, 303 K, and 310 K, respectively. The fluorescence process between HSA and TpCP involved a mix of static and dynamic quenching mechanism. The gibbs free energy (ΔG0) of HSA-TpCP system was -24.452 kJ/mol, -25.907 kJ/mol, -27.363 kJ/mol, and - 29.401 kJ/mol at 293 K, 298 K, 303 K, and 310 K, respectively, suggesting that the HSA-TpCP reaction was spontaneous. The enthalpy change (ΔH0) and thermodynamic entropy change (ΔS0) of the HSA-TpCP system were 60.83 kJ/mol and 291.08 J/(mol·>k), respectively, indicating that hydrophobic force was the major driving force in the HSA-TpCP complex. Furthermore, multispectral analysis also revealed that TpCP could alter the microenvironment of tryptophan residue and the secondary structure of HSA and bind with the active site I of HSA. Molecular docking and MD simulations confirmed that TpCP could spontaneously form a stable complex with HSA, which was consistent with the fluorescence experimental results. This study provides novel insights into the mechanisms of underlying the transportation and distribution of OPFRs in humans.

Multispectroscopic and Theoretical Investigation on the Binding Interaction of a Neurodegenerative Drug, Lobeline with Human Serum Albumin: Perturbation in Protein Conformation and Hydrophobic-Hydrophilic Surface

Lobeline (LOB), a naturally occurring alkaloid, has a broad spectrum of pharmacological activities and therapeutic potential, including applications in central nervous system disorders, drug misuse, multidrug resistance, smoking cessation, depression, and epilepsy. LOB represents a promising compound for developing treatments in various medical fields. However, despite extensive pharmacological profiling, the biophysical interaction between the LOB and proteins remains largely unexplored. In the current article, a range of complementary photophysical and cheminformatics methodologies were applied to study the interaction mechanism between LOB and the carrier protein HSA. Steady-state fluorescence and fluorescence lifetime experiments confirmed the static-quenching mechanisms in the HSA-LOB system. "K" (binding constant) of the HSA-LOB system was determined to be 105 M-1, with a single preferable binding site in HSA. The forces governing the HSA-LOB stable complex were analyzed by thermodynamic parameters and electrostatic contribution. The research also investigated how various metal ions affect complex binding. Site-specific binding studies depict Site I as probable binding in HSA by LOB. We conducted synchronous fluorescence, 3D fluorescence, and circular dichroism studies to explore the structural alteration occurring in the microenvironment of amino acids. To understand the robustness of the HSA-LOB complex, we used theoretical approaches, including molecular docking and MD simulations, and analyzed the principal component analysis and free energy landscape. These comprehensive studies of the structural features of biomolecules in ligand binding are of paramount importance for designing targeted drugs and delivery systems.

Analytic and In Silico Methods to Understand the Interactions between Dinotefuran and Haemoglobin

This work lies in the growing concern over the potential impacts of pesticides on human health and the environment. Pesticides are extensively used to protect crops and control pests, but their interaction with essential biomolecules like haemoglobin (Hb) remains poorly understood. Spectrofluorometric, electrochemical, and in silico investigations have been chosen as potential methods to delve into this issue, as they offer valuable insights into the molecular-level interactions between pesticides and haemoglobin. The research aims to address the gaps in knowledge and contribute to developing safer and more sustainable pesticide practices. The interaction was studied by spectroscopic techniques (UV-Visible & Fluorescence), in silico studies (molecular docking & molecular dynamics simulations) and electrochemical techniques (cyclic voltammetry and tafel). The studies showed effective binding of dinotefuran with the Hb which will cause toxicity to human. The formation of a stable molecular complex between ofloxacin and Haemoglobin was shown via molecular docking and the binding energy was found to be -5.37 kcal/mol. Further, molecular dynamics simulations provide an insight for the stability of the complex (Hb-dinotefuran) for a span of 250 ns with a binding free energy of -53.627 kJ/mol. Further, cyclic voltammetry and tafel studies show the interaction of dinotefuran with Hb effectively.

Probing the interaction between the metallo-β-lactamase SMB-1 and ampicillin by multispectral approaches combined with molecular dynamics

Metallo-β-lactamases (MβLs) hydrolyze and inactivate β-lactam antibiotics, are a pivotal mechanism conferring resistance against bacterial infections. SMB-1, a novel B3 subclass of MβLs from Serratia marcescens could deactivate almost all β-lactam antibiotics including ampicillin (AMP), which has posed a serious threat to public health. To illuminate the mechanism of recognition and interaction between SMB-1 and AMP, various fluorescence spectroscopy techniques and molecular dynamics simulation were employed. The results of quenching spectroscopy unraveled that AMP could make SMB-1 fluorescence quenching that mechanism was the static quenching; the synchronous and three-dimensional fluorescence spectra validated that the microenvironment and conformation of SMB-1 were altered after interaction with AMP. The molecular dynamics results demonstrated that the whole AMP enters the binding pocket of SMB-1, even though with a relatively bulky R1 side chain. Loop1 and loop2 in SMB-1 undergo significant fluctuations, and α2 (71-73) and local α5 (186-188) were turned into random coils, promoting zinc ion exposure consistent with circular dichroism spectroscopy results. The binding between them was driven by a combination of enthalpy and entropy changes, which was dominated by electrostatic force in agreement with the fluorescence observations. The present study brings structural insights and solid foundations for the design of new substrates for β-lactamases and the development of effective antibiotics that are resistant to superbugs.

Investigating Pyruvate Dehydrogenase Kinase 3 Inhibitory Potential of Myricetin Using Integrated Computational and Spectroscopic Approaches

Protein kinases are involved in various diseases and currently represent potential targets for drug discovery. These kinases play major roles in regulating the cellular machinery and control growth, homeostasis, and cell signaling. Dysregulation of kinase expression is associated with various disorders such as cancer and neurodegeneration. Pyruvate dehydrogenase kinase 3 (PDK3) is implicated in cancer therapeutics as a potential drug target. In this current study, a molecular docking exhibited a strong binding affinity of myricetin to PDK3. Further, a 100 ns all-atom molecular dynamics (MD) simulation study provided insights into the structural dynamics and stability of the PDK3-myricetin complex, revealing the formation of a stable complex with minimal structural alterations upon ligand binding. Additionally, the actual affinity was ascertained by fluorescence binding studies, and myricetin showed appreciable binding affinity to PDK3. Further, the kinase inhibition assay suggested significant inhibition of PDK3 by myricetin, revealing an excellent inhibitory potential with an IC50 value of 3.3 μM. In conclusion, this study establishes myricetin as a potent PDK3 inhibitor that can be implicated in therapeutic targeting cancer and PDK3-associated diseases. In addition, this study underscores the efficacy of myricetin as a potential lead to drug discovery and provides valuable insights into the inhibition mechanism, enabling advancements in cancer therapeutics.

Exploring the interaction of a potent anti-cancer drug Selumetinib with bovine serum albumin: Spectral and computational attributes

The binding of drugs to plasma proteins determines its fate within the physiological system, hence profound understanding of its interaction within the bloodstream is important to understand its pharmacodynamics and pharmacokinetics and thereby its therapeutic potential. In this regard, our work delineates the mechanism of interaction of Selumetinib (SEL), a potent anti-cancer drug showing excellent effect against multiple solid tumors, with plasma protein bovine serum albumin (BSA), using methods such as absorption, steady-state fluorescence, time-resolved, fluorescence resonance energy transfer, Fourier transform infrared spectra (FTIR), circular dichroism (CD), synchronous and 3D-fluorescence, salt fluorescence, molecular docking and molecular dynamic simulations. The BSA fluorescence intensity was quenched with increasing concentration of SEL which indicates interactions of SEL with BSA. Stern-Volmer quenching analysis and lifetime studies indicate the involvement of dynamic quenching. However, some contributions from the static quenching mechanism could not be ruled out unambiguously. The association constant was found to be 5.34 × 105 M-1 and it has a single binding site. The Förster distance (r) indicated probable energy transmission between the BSA and SEL. The positive entropy changes and enthalpy change indicate that the main interacting forces are hydrophobic forces, also evidenced by the results of molecular modeling studies. Conformation change in protein framework was revealed from FTIR, synchronous and 3D fluorescence and CD studies. Competitive binding experiments as well as docking studies suggest that SEL attaches itself to site I (subdomain IIA) of BSA where warfarin binds. Molecular dynamic simulations indicate the stability of the SEL-BSA complex. The association energy between BSA and SEL is affected in the presence of different metals differently.

Structural and functional impacts of neonicotinoids analogues on Apis mellifera's chemosensory protein: Insights from spectroscopic and molecular modeling investigations

In the intricate web of ecological relationships, pollinators such as the Italian honeybee (Apis mellifera) play a crucial role in maintaining biodiversity and agricultural productivity. This study focuses on the interactions between three neonicotinoid compounds and the honeybee's chemosensory protein 3 (CSP3), a key player in their olfactory system. Employing advanced spectroscopic techniques and molecular modeling, we explore the binding dynamics and conformational changes in CSP3 upon exposure to these pesticides. The research reveals that all three neonicotinoids considerably quench CSP3's fluorescence through a dynamic and static mixing mechanism, indicating a strong binding affinity, predominantly driven by hydrophobic interactions. UV-visible absorption, synchronous fluorescence, and 3D fluorescence spectra support slight changes in the microenvironment around the aromatic amino acids of CSP3. Circular dichroism spectra indicate a reduction in CSP3's α-helix content, suggesting structural alterations. Molecular docking and dynamics simulations further elucidate the binding modes and stability of these interactions, highlighting the role of specific amino acids in CSP3's binding cavity. Findings provide critical insights into molecular mechanisms by which neonicotinoids may impair honeybee chemosensory function, offering implications for designing safer pesticides and understanding the broader ecological impact of these chemicals on pollinator health.

Encapsulation of zingerone by self-assembling peptides derived from fish viscera: Characterization, interaction and effects on colon epithelial cells

The purpose of the present work was to encapsulate zingerone (a bioactive compound from ginger) by self-assembling peptides derived from fish viscera. The encapsulation conditions were investigated and the structure of fish peptides-zingerone complex was characterized. The interaction between zingerone and fish peptides was investigated using fluorescence spectroscopy. Further research was performed on the in vitro release of zingerone and fish peptide-zingerone as well as their antiproliferative effects on colon epithelial Caco-2 cells. The results demonstrated that zingerone can be successfully encapsulated by self-assembling peptides derived from fish viscera with high encapsulation efficiency and loading capacity. Furthermore, transmission electron microscope and confocal laser scanning microscope observations revealed the successful encapsulation of zingerone by fish viscera peptides. In addition, in vitro release and antiproliferative activity against Caco-2 cells can be significantly increased by encapsulating zingerone via peptide self-assembly. The current study advances knowledge of encapsulation of bioactive compounds through peptide self-assembly.

Experimental and Theoretical Approaches to Monitor the Behavior of Bovine Liver Catalase in Interaction with a Binuclear Bismuth Complex

Here, the antioxidant potency of a binuclear Bi(III) complex {[Bi2(μ-ox)(dipic)2(H2O)2 (taa)2].H2O, where ox2- = oxalato, dipic2- = pyridine 2,6-dicarboxylato, and taa = thiourea} was evaluated using the •DPPH assay. It was demonstrated that the Bi complex exhibited a high ability to inhibit DPPH free radicals. The binding mechanism of the complex with bovine liver catalase (BLC) was also investigated, revealing structural and activity changes in the enzyme in the presence of the complex. The catalase activity in the decomposition of hydrogen peroxide increased in the presence of the Bi complex, reaching 39.8% higher than its initial activity at a concentration of 7.77 × 10-6 M. The complex exhibited a relatively high affinity for BLC, with K b values of 3.98, 0.13, and 0.09 × 105 M-1 at 303, 310, and 317 K, respectively. The mechanisms involved in the interaction were hydrogen bonding and van der Waals interactions, as validated through molecular docking simulations. Synchronous fluorescence showed that tryptophan was more affected by enzyme-complex interactions than tyrosine. In addition, a cell viability test using the MTT method revealed that at its highest concentration, the Bi complex caused a decrease in the number of cells below 50% compared to the control, while cisplatin showed negative effects at all concentrations. These findings suggest that the Bi complex has the potential to be developed as a promising candidate for BLC-related therapeutic target therapy.

Insights into the binding of buspirone to human serum albumin using multi-spectroscopic and molecular docking techniques

Buspirone is an anxiolytic drug that plays a significant role in managing anxiety disorders and alleviating their symptoms as well. Several techniques were utilized to study the interaction between buspirone and human serum albumin under physiological conditions, including UV-vis absorption spectroscopy, fluorescence emission spectroscopy, circular dichroism, Fourier transform infrared spectroscopy (FT-IR), equilibrium dialysis, and molecular docking. The results of this study demonstrated that buspirone quenched the intrinsic fluorescence of human serum albumin through a mixed mechanism. Moreover, the binding constants (Kb), the quenching constants (Ksv), and thermodynamic parameters were calculated at various temperatures. The binding process of buspirone to human serum albumin showed a cooperative binding pattern, confirmed by the Scatchard diagram and Hill coefficient. Molecular docking results showed that buspirone interacted with the IIA, IIIA, and IIB subdomains of human serum albumin and slightly changed its conformation. It was also found that hydrophobic forces played a major role in this interaction. This study consequently proves that BSH as a drug can be transported by blood albumin. Additionally, due to its ratiometric response in absorbance upon binding to a biological target, HSA can be used as a molecular probe to follow biomolecular interactions.

Synthesis, characterization, and BSA binding studies of newfangled 2-phenylacetohydrazide derivatives

Five 2-phenylacetohydrazide derivatives (BPAH = N'-benzylidene-2-phenylacetohydrazide, HBPAH = N'-(2-hydroxybenzylidene)-2-phenylacetohydrazide), PPAH = 2-phenyl-N'-3-phenylallylideneacetohydrazide, FMPAH = N'-(furan-2-ylmethylene)-2-phenylaceto hydrazide and EPAH = N'-ethylidene-2-phenylacetohydrazide were synthesized by the condensation of 2-phenylacetohydrazide with the corresponding aldehyde. The synthesized compounds were characterized by FTIR, 1D, and 2D NMR spectroscopy. The structure of the BPAH and PPAH were analyzed by single crystal X-ray diffraction analysis and in both crystallized compounds, the molecules adopted trans geometry around the -C[bond, double bond]N- (imine) functional group. To explore the pharmacological significance of these compounds, the binding ability of these compounds with Bovine Serum Albumin (BSA) was investigated using fluorescence spectroscopy. BPAH and PPAH showed the highest binding ability while EPAH, HBPAH, and FMPAH had lower binding ability to BSA molecules. Thermodynamic parameters ΔG, ΔH°, and ΔS° demonstrated that interactions of BSA with compounds BPAH, EPAH, FMAH, and HBPAH were exothermic while for PPAH it was endothermic. The negative enthalpy and entropy of the compounds BPAH, EPAH, FMAH, and HBPAH indicated that van der Waals' forces and hydrogen bonding played a major role in stabilizing the BSA binding with the molecules. Hydrophobic interactions were predominant in the binding of PPAH with BSA tends to interact with two sets of BSA binding sites with an increase in temperature.

Comprehending the intermolecular interaction of dacomitinib with bovine serum albumin: experimental and theoretical approaches

Dacomitinib (DAC), as a member of tyrosine kinase inhibitors is primarily used to treat non-small cell lung cancer. The intermolecular interaction between DAC and bovine serum albumin (BSA) was comprehended with the help of experiments and theoretical simulations. The outcomes indicated that DAC quenched the endogenous fluorescence of BSA through static quenching mode. In the binding process, DAC was preferentially inserted into the hydrophobic cavity of BSA subdomain IA (site III), and a fluorescence-free DAC-BSA complex with molar ratio of 1:1 was generated. The outcomes confirmed that DAC had a stronger affinity on BSA and the non-radiative energy transfer occurred in the combination process of two. And, it can be inferred from the outcomes of thermodynamic parameters and competition experiments with 8-aniline-1-naphthalenesulfonic acid (ANS) and D-(+)- sucrose that hydrogen bonds (H-bonds), van der Waals forces (vdW) and hydrophobic forces had a significant impact in inserting DAC into the hydrophobic cavity of BSA. The outcomes from multi-spectroscopic measurements that DAC could affect the secondary structure of BSA, that was, α-helix content decreased slightly from 51.0% to 49.7%. Moreover, the combination of DAC and BSA led to a reduction in the hydrophobicity of the microenvironment around tyrosine (Tyr) residues in BSA while had little influence on the microenvironment of around tryptophan (Trp) residues. The outcomes from molecular docking and molecular dynamics (MD) simulation further demonstrated the insertion of DAC into site III of BSA and hydrogen energy and van der Waals energy were the dominant energy of DAC-BSA stability. In addition, the influence of metal ions (Fe3+, Cu2+, Co2+, etc.) on the affinity of the system was explored.Communicated by Ramaswamy H. Sarma.

The weakened physiological functions of human serum albumin in presence of polystyrene nanoplastics

Due to the widespread presence of nanoplastics (NPs) in daily essentials and drinking water, the potential adverse effects of NPs on human health have become a global concern. Human serum albumin (HSA), the most abundant and multi-functional protein in plasma, has been chosen to understand the biological effects of NPs after entering the blood. The esterase activity and the transport of bisphenol A in the presence of polystyrene nanoplastics (PSNPs) under physiological conditions (pH 4.0 and 7.4) have been investigated to evaluate the possible biological effects. The interactions between PSNPs and HSA have also been systematically studied by multispectral methods and dynamic light scattering techniques. The esterase activity of HSA presented a decreased trend with increasing PSNPs; conversely, higher permeabilities are accompanied by higher amounts of PSNPs. Compared with the unchanged hydrodynamic diameter and weaker interactions at pH 7.4, stronger binding between HSA and PSNPs at pH 4.0 led to a significant increase in the particle size of the PSNPs-HSA complex. The quenching mechanism belonged to the static quenching type. The electrostatic force is proposed to be the dominant factor for PSNPs binding to HSA. The work provides some information about the toxicity of NPs when exposed to humans.

Extraction and characterization of polysaccharides from blackcurrant fruits and its inhibitory effects on acetylcholinesterase

Microwave assisted aqueous two-phase system (MA-ATPS) was used to simultaneously extract two polysaccharides from blackcurrant. Under the suitable ATPS (ethanol/(NH4)2SO4, 26.75 %/18.98 %) combining with the optimal MA conditions (liquid-to-material ratio 58.5 mL/g, time 9.5 min, temperature 60.5 °C, power 587 W) predicted by response surface methodology, the yields of the top/bottom phase polysaccharides were 13.08 ± 0.37 % and 42.65 ± 0.89 %, respectively. After purification through column chromatography, the top phase polysaccharide (PRTP) and bottom phase polysaccharide (PRBP) were obtained. FT-IR, methylation and NMR analyses confirmed that the repeating unit in the backbone of PRTP was →2, 5)-α-L-Araf-(1 → 3)-α-D-Manp-(1 → 6)-β-D-Galp-(1 → 6)-α-D-Glcp-(1 → 4)-α-L-Rhap-(1 → 4)-α-D-GalAp-(1→, while the possible unit in PRBP was →4)-α-L-Rhap-(1 → 3)-α-D-Manp-(1 → 6)-β-D-Galp-(1 → 6)-α-D-Glcp-(1 → 2, 5)-α-L-Araf-(1 → 4)-α-D-GalAp-(1→. PRBP with relatively low molecular weight exhibited better stability, rheological property, free radical scavenging and acetylcholinesterase (AChE) inhibitory activities than PRTP. PRTP and PRBP were reversible mixed-type inhibitors for AChE, and the conformation of AChE was changed after binding with the polysaccharides. Molecular docking, fluorescence and isothermal titration calorimetry assays revealed that PRTP and PRBP quenched the fluorescence through static quenching mechanism, and the van der Waals interactions and hydrogen bonding played key roles in the stability of polysaccharide-enzyme complexes. This study provided a theoretical basis for blackcurrant polysaccharides as AChE inhibitors to treat Alzheimer's disease.

Investigating the effect of pH on the interaction of cypermethrin with human serum albumin: Insights from spectroscopic and molecular dynamics simulation studies

To efficiently combat the negative consequences of the utilization of pesticides and hazardous substances with biomolecules, it is crucial to comprehend the features of the corresponding compounds. In this study, interactions between cypermethrin (CYP) and HSA at neutral and acidic pH were investigated using a set of spectroscopic and computational tools, such as UV/VIS's absorption spectroscopy, fluorescence, Fourier-transform infrared (FTIR) spectroscopy, molecular docking, and molecular dynamics. Furthermore, the effect of CYP on the HSA thermal stability was investigated. The increase in the CYP concentration at acidic and neutral pH resulted in static HSA fluorescence quenching. In the interaction between HSA and CYP at both pH, increasing the temperature led to a decrease in the Stern-Volmer quenching constant and the binding constant. We also revealed that with increasing CYP concentration, the melting temperature of HSA increases at both pH values.

Evidence for paraquat-pepsin interaction: In vitro and silico study

The use of the herbicide paraquat (PQ) has raised concerns about potential environmental consequences due to its toxicity and persistence in the environment. Considering the affinity of dangerous compounds to biological molecules, it is necessary to know their binding properties. This article focuses on the behavior of the pepsin enzyme following its contact with paraquat poison, and the interaction between paraquat and pepsin has been investigated in laboratory conditions and simulated physiological conditions using multispectral techniques. Fluorescence experiments showed that PQ uses a static method to quench pepsin's intrinsic fluorescence. By causing structural damage to pepsin, PQ may be detrimental as it alters its conformational function based on FT-IR spectroscopy. The coupling reaction is a spontaneous process caused by hydrogen bonding and van der Waals forces according to the analysis of the thermodynamic parameters of each system at three different temperatures. The molecular structure of pepsin changes when it binds to PQ. Also, the results showed that PQ is a pepsin inhibitor that changes the function of the enzyme.

Binding studies of potential amyloid-β inhibiting chalcone derivative with bovine serum albumin

Chalcones (α-phenyl-β-benzoylethylene) and their natural-source derivatives have been investigated for their remarkable biological activities, like neuroprotective, anti-inflammatory, and anti-tumor properties. A triazole chalcone ligand (E)-3-(4-(dimethylamino)phenyl)-1-(4-((1-(2-(4-((E)-3-(4(dimethylamino)phenyl)acryloyl)phenoxy)ethyl)-1H-1,2,3-triazol-4-yl)methoxy)phenyl)prop-2-en-1-one (L1) was synthesized by Cu(I)- catalysed click reaction. The mechanistic properties of L1 for therapy were evaluated by analyzing the binding interactions between L1 and bovine serum albumin (BSA) through photophysical and computational studies. The structural elucidation of ligand L1 was carried out by NMR and mass spectrometry. The Aβ inhibitory activity of L1 was studied by thioflavin T assay and transmission electron microscopy. The biomolecular interaction of L1 with bovine serum albumin was examined through multi-spectroscopic techniques in combination with in silico studies. UV-Visible absorption, fluorescence spectroscopy, circular dichroism, Förster resonance energy transfer, and three-dimensional fluorescence studies confirmed the formation of a BSA-L1 complex. The potential binding sites, mechanism of interactions, and variations in the environment of tyrosine and tryptophan amino acid residues of BSA were assessed at different temperatures. The binding constant for the Static quenching mechanism of intrinsic fluorescence of BSA was of the order of 105 M-1. The esterase enzyme activity assay in the presence of L1 revealed an increase in the protein enzyme activity. Molecular docking studies suggested L1 was predominantly bound to BSA by hydrogen bonds and Van der Waals forces.

Investigation of the interaction between S-isoalkyl derivatives of the thiosalicylic acid and human serum albumin

S-isoalkyl derivatives of thiosalicylic acid (isopropyl-(L1), isobutyl-(L2) and isoamyl-(L3)) were selected in order to investigate the binding interaction with the human serum albumin (HSA) using different spectroscopic methods and molecular docking simulation. Association constants and number of binding sites were used to analyze the quenching mechanism. The experimental results showed that the fluorescence quenching of HSA by L1, L2 and L3 occurs because of static quenching and that binding processes were spontaneous, with the leading forces in bonding by hydrogen bonding, hydrophobic interactions, and electrostatic interactions. Fluorescence spectroscopy, UV-Vis spectroscopy and synchronous fluorescence spectroscopy showed that ligands (L1, L2 and L3) can bind to HSA and that the binding of ligands induced some microenvironmental and conformational changes in HSA. The calculated distance between the donor and the acceptor according to fiFörster's theory confirms the energy transfer efficiency between the acceptor and HSA. Results of site marker competitive experiments showed that the tested compounds bind to HSA in domain IIA (Site I). Molecular dynamics and docking calculations demonstrated that L3 binds to the Sudlow site I of HSA with lower values of binding energies compared to L1 and L2, indicating the formation of the most stable ligand-HSA complex. Understanding the binding mechanisms of S-isoalkyl derivatives of the thiosalicylic acid to HSA may provide valuable data for the future studies of their biological activity and application as potential antitumor drugs.Communicated by Ramaswamy H. Sarma.

Comprehending the intermolecular interaction of JAK inhibitor fedratinib with bovine serum albumin (BSA)/human alpha-1-acid glycoprotein (HAG): Multispectral methodologies and molecular simulation

The primary coverage of this paper is to investigate the molecular interaction of JAK2 inhibitor, fedratinib (FED) with BSA/HAG proteins through multispectral approaches and molecular docking as well as MD calculation. Arrival at a conclusion, the endogenous fluorescence of BSA/HAG protein was quenched separately in the form of static and mixed quenching. The FED-BSA and FED-HAG complexes with the stoichiometric ratio of 1:1 were formed in the interaction process. And, The Kb values of these complexes were of 104-105 M-1 and 105-106 M-1, respectively, representing that the FED-HAG complex exhibited a comparatively high affinity compared to the FED-BSA complex. It is confimed that FED inserted into the interface area between subdomain IIA and IIB of BSA (marked as site II') and the bucket-shaped hydrophobic cavity of HAG, respectively, resulting in the slight alteration in the secondary structure of BSA/HAG and the micro-environment round Tyr and Trp residues. The expetimental results also confirmed that van der Waals forces (VDW), hydrogen bonds and hydrophobic interaction played a dominant role in the formation of two stable complexes. The above experimental results were supplemented and verified through molecular docking and MD simulation. Meanwhile, the effects of common ions on affinity were explored. This study could shine a light on evaluating the pharmacological properties of the JAK inhibitor FED, understanding the distribution and operation of the drug in the body, and leading to the development of the creation of novel medication devise.

A phenanthroline-based erbium (III) complex: molecular docking, DNA/BSA -binding and biological evaluation

With the help of both theoretical as well as experimental research, in vitro binding research with CT-DNA (calf thymus) and BSA (bovine serum albumin) were carefully examined to figure out the chemotherapeutic and pharmacokinetic facets of the Erbium complex, which contains 1,10-phenanthroline (Phen). The binding characteristics and the mechanism of complex's interaction with DNA as well as the protein were determined utilizing fluorescence quenching method. Findings indicated that the complex's interaction with DNA via groove binding into DNA's minor grooves, with their binding constants falling within the 104 M-1 range. Furthermore, thermodynamic characteristics and the fluorescence emission of the tryptophan residues of the protein were obtained through fluorescence quenching studies at different temperatures. According to the results of the binding constants, the protein's interactions with the Er- complex were moderate, demonstrating that the compound may be transported effectively by the protein. Molecular docking results supported that of the experimental research. The HeLa and MCF-7 cancer cell lines, along with the normal human fibroblast cell line, were used in an MTT assay evaluation of the Er-complex cytotoxicity. The Er-complex displayed a selective inhibitory effect on the proliferation of different cancer cells.Communicated by Ramaswamy H. Sarma.

Structural alterations and inhibition of lysozyme activity upon binding interaction with rotenone: Insights from spectroscopic investigations and molecular dynamics simulation

The pervasive employment of pesticides such as rotenone on a global scale represents a substantial hazard to human health through direct exposure. Therefore, exploring the interactions between such compounds and body macromolecules such as proteins is crucial in comprehending the underlying mechanisms of their detrimental effects. The present study aims to delve into the molecular interaction between rotenone and lysozyme by employing spectroscopic techniques along with Molecular dynamics (MD) simulation in mimicked physiological conditions. The binding interaction resulted in a fluorescence quenching characterized by both dynamic and static mechanisms, with static quenching playing a prominent role in governing this phenomenon. The analysis of thermodynamic parameters indicated that hydrophobic interactions primarily governed the spontaneous bonding process. FT-IR and circular dichroism findings revealed structural alternations of lysozyme upon complexation with rotenone. Also, complexation with rotenone declined the biological activity of lysozyme, thus rotenone could be considered an enzyme inhibitor. Further, the binding interaction substantially decreased the thermal stability of lysozyme. Molecular docking studies showed the binding location and the key residues interacting with rotenone. The findings of the spectroscopic investigations were confirmed and accurately supported by MD simulation studies.

Preparation of Ribes nigrum L. polysaccharides-stabilized selenium nanoparticles for enhancement of the anti-glycation and α-glucosidase inhibitory activities

Seven kinds of selenium nanoparticles (RP-SeNPs) were prepared by using the polysaccharides extracted from Ribes nigrum L. (RP) as the stabilizer and dispersant. Among them, RP-SeNPs-1 (94.2 nm), RP-SeNPs-2 (101.2 nm) and RP-SeNPs-3 (107.6 nm) with relatively smaller mean particle size exhibited stronger α-glucosidase inhibitory activity than other RP-SeNPs (115.3-164.2 nm) and SeNPs (288.9 nm). Ultraviolet-visible spectrophotometry, Fourier transform-infrared, X-ray diffraction, energy dispersive X-ray and X-ray photoelectron spectroscopy analyses confirmed that SeNPs were ligated with RP to form nanocomposites and displayed amorphous form. Electron microscopy images revealed that RP-SeNPs-1 - RP-SeNPs-3 were regular shape spherical nanocomposites with much better dispersion than SeNPs. Compared with SeNPs, RP-SeNPs displayed relatively high thermal, storage, pH and salt ion stability. Moreover, RP-SeNPs-1-RP-SeNPs-3 showed significantly better anti-glycation and α-glucosidase inhibitory activity than SeNPs, especially RP-SeNPs-1 with the smallest particle size. Inhibitory kinetics analysis indicated that SeNPs and RP-SeNPs inhibited α-glucosidase with competitive type and reversible mechanism. In addition, the conformation of the α-glucosidase was changed after binding with the SeNPs and RP-SeNPs-1. Fluorescence quenching and isothermal titration calorimetry assays revealed that these two nanoparticles could interact with α-glucosidase to form non-fluorescent complexes through hydrogen bonding, and the formation was spontaneously driven by enthalpy.

Multispectroscopic and computational study of interaction of the bovine serum albumin with atropine and atropine-loaded chitosan nanoparticles (synthesized and characterized)

Two different systems of bovine serum albumin (BSA) were used for multiple spectroscopic and computational studies to determine interaction of BSA and atropine (Atrop), that is, BSA-Atrop system and Atrop-loaded chitosan nanoparticles (Atrop@CS NPs), that is, BSA-Atrop@CS NPs system. The study suggests that BSA-Atrop system and BSA-Atrop@CS NPs system involve non-fluorescent complexes of Ksv = 3.2 × 103 Lmol-1 and 3.1 × 104 Lmol-1, kq = 3.2 × 1011 Lmol-1 s-1 and 3.1 × 1012 Lmol-1 s-1, the binding constant Kb = 1.4 × 103 Lmol-1, 2.0 × 102 Lmol-1, respectively, and number of binding sites n ∼ 1 for both the systems. The negligible conformational changes induced in BSA were also observed. Synchronous fluorescence spectroscopic study revealed that more quenching occurred in intrinsic fluorescence of tryptophan (Trp, W) than that in tyrosine residue (Tyr, Y). UV-vis spectroscopic study verified the presence of static quenching from the presence of BSA-Atrop and BSA-Atrop@CS NPs complexes. CD spectra confirmed the conformational changes induced in BSA upon increment of concentrations of Atrop and Atrop@CS NPs separately into the constant concentration of BSA. The coherent observations from various spectroscopic studies were in agreement with those of computational study, showing BSA-Atrop complex formation and other related details. The hydrogen bonds (H-bonds), van der Walls (vdW) interactions and π -type of interactions were mainly involved in stabilization of the formed BSA-Atrop complex.Communicated by Ramaswamy H. Sarma.

In-silico and in-detail experimental interaction studies of new antitumor Zn(II) complex with CT-DNA and serum albumin

In this study, a novel Zn(II) complex with the formula [Zn(pyrr-ac)2] (pyrr-ac: pyrrolidineacetate) was synthesized and characterized through molar conductivity, elemental analysis, 1H Nuclear Magnetic Resonance (1H NMR), UV-Visible spectroscopy, and Fourier transform infrared (FT-IR) methods. B3LYP level of DFT method along with aug-cc-pVTZ-PP/6-311G(d,p) basis set was utilized to perform the geometry optimization and HOMO-LUMO analysis. In addition, MEP, NLO and NBO computations were also performed at the same level of theory. In vitro antitumor activity of the mentioned complex on leukemia cell line, K562, was investigated using the MTT assay which surprisingly revealed the effective antitumor activity of the studied zinc complex. Interaction of this compound with biological macromolecules viz., CT-DNA and BSA was studied via different spectroscopic methods. The results of fluorescence experiment displayed that the metal complex binds to both macromolecules through hydrogen bond (H-bond) and van der Waals (vdW) forces. UV-Vis tests indicated a decline in the absorption spectra of CT-DNA/BSA in the presence of the compound. The interaction was further corroborated for CT-DNA via gel electrophoresis, CD spectroscopy and viscosity experiments and for BSA using CD spectroscopy. Furthermore, molecular docking simulation was done to evaluate the nature of interaction between the aforementioned zinc complex and CT-DNA/BSA. These results were in agreement with experimental findings and demonstrated that the main interaction is hydrogen bonding. The above type of investigations may provide a pathway through which zinc complexes join the anticancer category.[Figure: see text]The in-silico and in-vitro results confirm that the newly made [Zn(pyrr-ac)2] complex interacts with CT-DNA than BSA.Communicated by Ramaswamy H. Sarma.

Assessment on binding characteristics of ethiprole and a model protein bovine serum albumin (BSA) through various spectroscopic techniques integrated with computer simulation

To investigate the binding characteristics of pesticide ethiprole (ETP) with serum albumin is of great significance for pathological analysis of pesticide poisoning, gene mutation, and clinical detection. In present work, the binding characteristics of ETP with a model protein BSA has been estimated by means of multi-spectroscopic approaches integrated with computer simulation. The outcomes testified that the intrinsic fluorescence of BSA was mainly quenched by ETP in a static quenching mode and the stable ETP-BSA complex with the stoichiometry of 1:1 and the binding constant of 6.81 × 103 M-1 (298 K) was produced. The outcomes revealed that ETP combined preferentially to the subdomain IIA (Site I) of BSA and caused the decline in the content of α-helix of BSA and the enhancement in the hydrophobicity of environment centered on Trp residues. The outcomes of experimental and theoretical studies provide the sufficient evidence about the driving forces for the complexation of ETP with BSA, which included van der Waals forces (vdW), hydrogen bonding (H-bonding) interaction, and hydrophobicity. Simultaneously, the theoretical calculation results also confirmed the existence of the significant changes in the physicochemical natures of ETP including molecular conformation, dipole moment, frontier orbital energy, and the atomic charge distribution, which was a responsible for the complexation with BSA.Communicated by Ramaswamy H. Sarma.

Comparative assessment of 9-bromo noscapine ionic liquid and noscapine: Synthesis, in-vitro studies plus computational & biophysical evaluation with human hemoglobin

Noscapine is a proficient anticancer drug active against wide variety of tumors including lung cancer. Over time, several noscapine analogues have been assessed to maximize the efficiency of the drug, amongst which 9-bromo noscapine remains one of the most potent analogues till date. In the present work, we have synthesized 9-bromo noscapine ionic liquid [9-Br-Nos]IBr2, an active pharmaceutical ingredient based ionic liquid (API-IL) to address the existing issues of solubility and targeted drug delivery in the parent alkaloid as well as the synthesized analogues. We have devised a novel two-step synthesis route (first-ever ionic to ionic bromination) to obtain the desired [9-Br-Nos]IBr2 which is advantageous to its organic analogue in terms of increased solubility, lesser reaction time and better yield. Furthermore, we have compared 9-bromo noscapine ionic liquid with noscapine based on its binding interaction with human hemoglobin (Hb) studied via computational along with spectroscopic studies, and bioactivity against non-small cell lung cancer. We inferred formation of a complex between [9-Br-Nos]IBr2 and Hb in the stoichiometric ratio of 1:1, similar to noscapine. At 298 K, [9-Br-Nos]IBr2-Hb binding was found to exhibit Kb and ∆G of 36,307 M-1 and -11.5 KJmol-1, respectively, as compared to 159 M-1 and -12.5 KJmol-1 during Noscapine-Hb binding. This indicates a more stronger and viable interaction between [9-Br-Nos]IBr2 and Hb than the parent compound. From computational studies, the observed higher stability of [9-Br-Nos]I and better binding affinity with Hb with a binding energy of -91.75 kcalmol-1 supported the experimental observations. In the same light, novel [9-Br-Nos]IBr2 was found to exhibit an IC50 = 95.02 ± 6.32 μM compared to IC50 = 128.82 ± 2.87 μM for noscapine on A549 (non-small lung cancer) cell line at 48 h. Also, the desired ionic liquid proved to be more cytotoxic inducing a mortality rate of 87 % relative to 66 % evoked by noscapine at concentrations of 200 μM after 72 h.

Molecular Recognition Study toward the Mitochondrial Electron Transport Chain Inhibitor Mubritinib and Human Serum Albumin

The ability to bind plasma proteins helps in comprehending relevant aspects related to the pharmacological properties of many drugs. Despite the vital role of the drug mubritinib (MUB) in the prophylaxis of various diseases, its interaction with carrier proteins still needs to be clarified. The present work focuses on the interaction between MUB and Human serum albumin (HSA), investigated by employing multispectroscopic, biochemical, and molecular docking approaches. The results reveal that MUB has quenched HSA intrinsic fluorescence (following a static mechanism) by attaching very close (r = 6.76 Å) and with moderate affinity (Kb ≈ 104 M-1) to the protein site I (mainly by H-bonds, hydrophobic and Van der Waals forces). On one side, the HSA-MUB interaction has been accompanied by a slight disturbance in the HSA chemical environment (around the Trp residue) and protein secondary structure modifications. On another side, MUB competitively inhibits HSA esterase-like activity, which is very similar to other Tyrosine kinase inhibitors, and evidence that protein functional alterations have been triggered by MUB interaction. In summary, all of the presented observations can shed light on diverse pharmacological factors associated with drug administration.

Exploring the binding effect and mechanism of glycyrrhizin to ovomucin by combining spectroscopic analysis and molecular docking

Ovomucin (OVM) is an ideal natural macromolecular glycoprotein extracted from eggs with good adhesion. Based on the defect that glycyrrhizin (GL) has good antiviral activity but fast metabolism, this study aimed to explore the binding effect and mechanism of GL to OVM, using multi-spectroscopic techniques, isothermal titration calorimetry (ITC), and molecular docking. The adhesion ability of OVM to the hydrophilic interface and GL was first demonstrated by dual polarization interferometry (DPI) analysis and binding capacity assay, and the OVM-GL complex exhibited a similar affinity for the spike protein of COVID-19. The spectroscopic results show that GL can quench the inherent fluorescence and change the glycosidic bond and secondary structure of OVM. The ITC measurements suggested that the binding was exothermic, the hydrogen bond was the dominant binding force for forming OVM-GL. Finally, molecular docking results indicated that GL has hydrogen bond interaction with several amino acid residues located in α-OVM and β-OVM while embedding into the hydrophobic pocket of OVM via hydrophobic interactions. In conclusion, OVM can adhere to the hydrophilic interface and bind to GL through hydrogen bonding and hydrophobic interactions to form a stable complex, that is expected to be helpful in virus prophylaxis.

Inhibitory potential of N-acetylaspartate against protein glycation, AGEs formation and aggregation: Implication of brain osmolyte in glycation-related complications

Protein glycation and aggregation have a pivotal role in many diseases including diabetes and neurodegenerative disorders. N-acetyl aspartate (NAA), an osmolyte derived from L-aspartic acid, is one of the most abundant metabolites in the mammalian brain. Although NAA is supposed to be a substitute for a neuronal marker, its function is not fully elucidated. Herein, we have investigated the effect of NAA on glycation, AGEs formation and aggregation of irisin. AGE-specific fluorescence showed the strong inhibition of AGEs formation in the presence of NAA, demonstrating its anti-glycating property. The aggregates present in MG-modified irisin were also reduced by NAA, which was confirmed by Thioflavin T fluorescence and fluorescence microscopy. Further, for the explanation of the strong anti-glycating potential of NAA, the interaction between irisin and NAA was also examined. Interaction studies involving steady-state fluorescence and molecular docking demonstrated that hydrogen bonding and salt bridges by NAA stabilize the irisin. It was found that glycation-prone residues i.e., lysine and arginine are specifically involved in the interaction which might prevent them from getting modified during the process of glycation. This study for the first time reported the antiglycating potential of NAA which can be implicated in the therapeutic management of various glycation-related complications.

Insights on the in-vitro binding interaction between donepezil and bovine serum albumin

In this work, the binding mechanism between donepezil (DNP) and bovine serum albumin (BSA) was established using several techniques, including fluorimetry, UV- spectrophotometry, synchronous fluorimetry (SF), fourier transform infrared (FTIR), fluorescence resonance energy transfer (FRET) besides molecular docking study. The fluorescence quenching mechanism of DNP-BSA binding was a combined dynamic and static quenching. The thermodynamic parameters, binding forces, binding constant, and the number of binding sites were determined using a different range of temperature settings. Van't Hoff's equation was used to calculate the reaction parameters, including enthalpy change (ΔH^ο) and entropy change (ΔS^ο). The results pointed out that the DNP-BSA binding was endothermic. It was shown that the stability of the drug-protein system was predominantly due to the intermolecular hydrophobic forces. Additionally, the site probing method revealed that subdomain IIA (Site I) is where DNP and BSA's binding occurs. This was validated using a molecular docking study with the most stable DNP configuration. This study might help to understand DNP's pharmacokinetics profile and toxicity as well as provides crucial information for its safe use and avoiding its toxicity.

Synthesis, spectral, DFT calculation, antimicrobial, antioxidant, DNA/BSA binding and molecular docking studies of bio-pharmacologically active pyrimidine appended Cu(II) and Zn(II) complexes

A new pyrimidine derivative Schiff base (HL) [HL = 2-((4-amino-6-chloropyrimidin-2-ylimino)methyl)-4-nitrophenol] has been synthesized using 2,6-diamino-4-chloropyrimidine and 5-nitrosalicylaldehyde. Transition metal complexes of Cu(II) and Zn(II) complexes [CuL(OAc)] (1), [ZnL(OAc)] (2) are prepared with HL/metal(II) acetate with molar ratio of 1:1. The Schiff base (HL) and the complexes 1 and 2 are evaluated by UV-Visible, 1H-NMR, FT-IR, EI-MS and ESR spectral techniques. Complexes 1 and 2 are confirmed as square planar geometry. Electrochemical studies of the complexes 1 and 2 are used to analyse the quasi reversible process. Density Functional Theory (DFT) using the B3LYP/6-31++G(d,p) level basis set was used to get the optimised geometry and non-linear optical properties. The complexes 1 and 2 are good antimicrobial agents than Schiff base (HL). The interactions of the HL and complexes 1 and 2 with Calf Thymus (CT) DNA are investigated by electronic absorption methods and viscosity measurements. Various molecular spectroscopy techniques, such as UV absorption and fluorescence, were used to explore the mechanism of interaction between the BSA and the ligand HL and complexes 1 & 2 under physiological settings. Complexes 1 and 2 are act as potential antioxidants than free Schiff base (HL) by DPPH radical scavenging assay. Furthermore, the purpose of the molecular docking studies was to better understand how metal complexes interact with biomolecules (CT-DNA and BSA). From these biological analyses, complex 1 acts as good intercalator with CT DNA & BSA and potent antioxidant with DPPH radical than complex 2.Communicated by Ramaswamy H. Sarma.

Interaction between Chinese quince fruit proanthocyanidins and bovine serum albumin: Antioxidant activity, thermal stability and heterocyclic amine inhibition

Heterocyclic amines (HCAs) are carcinogenic and mutagenic substances produced in fried meat. Adding natural antioxidants (e.g., proanthocyanidins (PAs)) is a common method to reduce HCAs; however, the interaction between the PAs and protein can affect the inhibitory efficacy of PAs on the formation of HCAs. In this study, two PAs (F1 and F2) with different degrees of polymerization (DP) were extracted from Chinese quince fruits. These were combined with bovine serum albumin (BSA). The thermal stability, antioxidant capacity and HCAs inhibition of all four (F1, F2, F1-BSA, F2-BSA) were compared. The results showed that F1 and F2 interact with BSA to form complexes. Circular dichroism spectra indicate that complexes had fewer α-helices and more β-sheets, β-turns and random coils than BSA. Molecular docking studies indicated that hydrogen bonds and hydrophobic interactions are the forces holding the complexes together. The thermal stabilities of F1 and, particularly, F2 were stronger than those of F1-BSA and F2-BSA. Interestingly, F1-BSA and F2-BSA showed increased antioxidant activity with increasing temperature. F1-BSA's and F2-BSA's HCAs inhibition was stronger than F1 and F2, reaching 72.06 % and 76.3 %, respectively, for norharman. This suggests that PAs can be used as natural antioxidants for reducing the HCAs in fried foods.

A review on medicinally important heterocyclic compounds and importance of biophysical approach of underlying the insight mechanism in biological environment

Heterocyclic derivatives have more interesting biological properties which hold a remarkable place in pharmaceutical industries due to their unique physiochemical properties and ease of adaption in various biological environments. Of many, the above-said derivatives have been recently examined for their promising action against a few malignancies. Specifically, anti-cancer research has benefited from these derivatives' natural flexibility and dynamic core scaffold. In any case, concerning some other promising anti-cancer drugs, heterocyclic derivative doesn't come without deficiencies. To be a successful drug candidate it should poses Absorption, Distribution, Metabolism and Eliminations (ADME) parameter, and must also have good binding interaction towards carrier protein as well as DNA and less in toxic nature, economically feasible. In this review, we described the overview of biologically important heterocyclic derivatives and their main application in medicine. Further, we focus types of biophysical techniques to understand the binding interaction mechanism.Communicated by Ramaswamy H. Sarma.

Insights into the interaction between the kusaginin and bovine serum albumin: Multi-spectroscopic techniques and computational approaches

Kusaginin, as a phenylethanoid glycoside, which has exhibited wide antioxidant and antimicrobial properties. The molecular mechanism underlying the broad biological activities of kusaginin has not yet been well documented. In this paper, the interaction of kusaginin with bovine serum albumin (BSA) has been explored by fluorescence spectra, UV-vis absorption spectra, and circular dichroism (CD) spectra along with computational approaches. The fluorescence experiments showed that kusaginin could strongly quench the intrinsic fluorescence of BSA through both dynamic and static quenching mechanisms. The thermodynamic analysis suggested that hydrophobic force was the main force in stabilizing the BSA-kusaginin complex. In addition, conformation changes of BSA were observed from three-dimensional and synchronous fluorescence spectra, UV spectra, and CD spectra under experimental conditions. All these experimental results have been complemented and validated by the molecular docking and dynamic simulation studies, which revealed that kusaginin was bound on the hydrophobic cavity in subdomain IIA of BSA and formed a stable BSA-kusaginin complex. Finally, density functional theory (DFT) calculation further implied that hydrogen bonds also support stabilizing the BSA-kusaginin complex. This research may aid in understanding the pharmacological characteristics of kusaginin and provide a vital reference modeling for the design of analogues drugs.

Bovine serum albumin interaction, molecular docking, anticancer and antimicrobial activities of Co(II) Schiff base complex derived from Nophen ligand

In this report, synthesis, characterization, biological and molecular modeling studies of Nophen Schiff base [N,N-bis(2-hydroxy-1-naphthaldehyde)-o-phenylenediamine] and Co(II)-Nophen complex have been furnished. BSA binding affinities of the ligand and Co(II)-Nophen complex have been appraised by UV-visible, fluorescence and cyclic voltammetric techniques. Spectroscopic measurements indicate strong binding of the complex with BSA protein through static quenching mechanism with binding constant in the order of 10⁴ M^-1. The negative shift of the peak potential in cyclic voltammetry suggested an electrostatic interaction. Molecular docking analysis reveals significant binding affinity (-6.3 kcal/mol) of the complex towards BSA protein. It is amazing that the in vitro cytotoxicity of Co(II)-Nophen complex against A549 cell lines (Human lung carcinoma cells) has remarkable potentials with 29 ± 1.2 µM as IC₅₀ value. Comparing the biological activity towards microorganisms, Co(II)-Nophen complex show substantial response than the Nophen ligand.Communicated by Ramaswamy H. Sarma.

The interaction mechanism of candidone with calf thymus DNA: A multi-spectroscopic and MD simulation study

In this investigation, the effects of candidone on the structure and conformation of DNA were evaluated by spectroscopic methods, molecular dynamics simulation, and molecular docking studies. Fluorescence emission peaks, ultraviolet-visible spectra, and molecular docking exhibited the complex formation between candidone and DNA in a groove-binding mode. Fluorescence spectroscopy results also showed a static quenching mechanism of DNA in the presence of candidone. Moreover, thermodynamic parameters demonstrated that candidone spontaneously bound to DNA with a high binding affinity. The hydrophobic interactions were the dominant forces over the binding process. Based on the Fourier transform infrared data candidone tended to attach to the A-T base pairs of the minor grooves of DNA. The thermal denaturation and circular dichroism measurements displayed that candidone caused a slight change in the DNA structure, which was confirmed by the molecular dynamics simulation results. According to the obtained findings from the molecular dynamic simulation, the structural flexibility and dynamics of DNA were altered to a more extended structure.

Molecular interactions between bovine serum albumin (BSA) and trihalophenol: Insights from spectroscopic, calorimetric and molecular modeling studies

The issue of disinfection byproducts (DBPs) in the water has received critical attention due to the health effects on humans. In the water environment, interactions between bovine serum albumins (BSA), the most abundant water-soluble protein, and DBPs unavoidably occur. In this study, comparative binding interactions of two aromatic DBPs - 2,4,6-trichlorophenol (TCP) and 2,4,6-tribromophenol (TBP) with BSA were investigated systematically utilizing fluorescence spectrometry, UV absorption spectrometry, isothermal titration calorimetry and molecular docking approach. The fluorescence quenching results indicated that TCP/TBP could quench the endogenous fluorescence of BSA through static quenching mechanisms, and TBP showed a more substantial quenching effect. The binding constants were determined for TCP-BSA (3.638 × 10⁵ L/mol, 303 K) and TBP-BSA (6.394 × 10⁵ L/mol, 303 K) complexes, with TBP showing higher binding affinity than TCP. The thermodynamic study and docking analysis suggested that hydrogen bonding and van der Waals forces were the primary interaction forces. Both of TCP and TBP were located in the subdomain IIIA of BSA, and TBP could form more stable complex than TCP. The results of the present study contributed valuable information on the environmental behaviors of halophenols in water environment from perspectives of binding with BSA.

Investigation on intermolecular interaction of synthesized azo dyes with bovine serum albumin

This research was performed using spectroscopic techniques and molecular docking to elucidate the mechanisms of interaction between bovine serum albumin (BSA) and two novel synthesized azo dyes. The titration of dyes into BSA solution results in quenching of fluorescence emission by complex formation. The UV-Vis spectroscopy confirms that formation of complex in ground state between both dyes and BSA induces conformational and micro environmental changes of the protein. Based on the calculation of the thermodynamic parameters, it can be concluded that both dyes spontaneously bind onto BSA, and van der Waals force and hydrogen bonding interaction played a predominant roles in the process of spontaneous bonding. The average binding distance (r) between protein and both dyes was calculated by Förster energy transfer measurements and revealed both dyes bind to the BSA residues of tryptophan over short distances. The results of molecular docking studies indicated that the probable binding location of both dyes is subdomain IB of BSA via hydrophobic interaction and hydrogen bond. Furthermore, as shown by synchronous fluorescence and Fourier transform infrared spectroscopy, both dyes can lead to conformational changes of BSA, which alter its biological functions.Communicated by Ramaswamy H. Sarma.

Investigation of the interaction behavior between quercetin and pepsin by spectroscopy and MD simulation methods

The ability of a therapeutic compound to bind to proteins is critical for characterizing its therapeutic impacts. We have selected quercetin (Qu), a most common flavonoid found in plants and vegetables among therapeutic molecules that are known to have anti-inflammatory, antioxidant, anti-genotoxic, and anti-cancer effects. The current study aimed to see how quercetin interacts with pepsin in an aqueous environment under physiological conditions. Absorbance and emission spectroscopy, circular dichroism (CD), and kinetic methods, as well as molecular dynamic (MD) simulation and docking, were applied to study the effects of Qu on the structure, dynamics, and kinetics of pepsin. Stern-Volmer (K_sv) constants were computed for the pepsin-quercetin complex at three temperatures, showing that Qu reduces enzyme emission spectra using a static quenching. With Qu binding, the V_max and the k_cat/K_m values decreased. UV-vis absorption spectra, fluorescence emission spectroscopy, and CD result indicated that Qu binding to pepsin leads to microenvironmental changes around the enzyme, which can alter the enzyme's secondary structure. Therefore, quercetin caused alterations in the function and structure of pepsin. Thermodynamic parameters, MD binding, and docking simulation analysis showed that non-covalent reactions, including the hydrophobic forces, played a key role in the interaction of Qu with pepsin. The findings conclude of spectroscopic experiments were supported by molecular dynamics simulations and molecular docking results.

Elucidation of the interaction mechanism of olmutinib with human α-1 acid glycoprotein: insights from spectroscopic and molecular modeling studies

Olmutinib, the third-generation tyrosine kinase inhibitor, is applied in treating non-small cell lung cancer (NSCLC). The aim of this study is to elucidate the interaction mechanism of olmutinib with human α-1 acid glycoprotein (HAG), an important carrier protein, by mean of multi-spectroscopic and molecular simulation techniques. Fluorescence spectral results confirmed that the fluorescence of this carrier protein can be quenched by olmutinib in the static quenching mode, and this anticancer drug possesses a moderate binding affinity on HAG. The evidence from thermodynamic analysis, replacement interaction with ANS and sucrose, and computational simulation results showed that hydrogen bonding, hydrophobic interactions, and van der Waals forces involved the olmutinib-HAG complexation process. The results from UV-vis, 3D fluorescence and synchronous fluorescence spectroscopy proved that binding anticancer drug olmutinib caused the alteration in the microenvironment around Trp residues. And, circular dichroism spectral results provided the support for the conformational alterations in the carrier protein. The data also proved that olmutinib preferably bound to the hydrophobic cavity of HAG and the binding distance between the two was 2.21 nm. In addition, it can be found that the presence of some metal ions such as Zn²⁺, Ca²⁺, Ni²⁺ and Cu²⁺ would exert a certain extent effect on the olmutinib-HAG complexation process.Communicated by Ramaswamy H. Sarma.

Biologically active oxovanadium(IV) Schiff base metal complex: antibacterial, antioxidant, biomolecular interaction and molecular docking studies

The oxovanadium(IV) Schiff base metal complex (ISNPV) have been synthesized as well as characterized by using micro analytical and traditional spectroscopic techniques. The spectral findings were utilized to validate the formation of ISNPV with structure exhibited square pyramidal geometry. The in vitro antibacterial activities of ISNPV were investigated to five different bacterial stains such as S. aureus, S. epidermidis, B. cereus, B. amyloliquefaciens and B. subtilis. The obtained result have suggested that the ISNPV has highest antibacterial activity against S. aureus than the other bacterial stains. The in vitro antioxidant activity like DPPH free radical scavenging assay method was studied by ISNPV in DMSO medium. Because it scavenges all free radicals, the ISNPV possesses higher antioxidant activity than the free ligand. UV-visible absorption and emission spectral techniques were used to investigate the binding of CT-DNA to the ISNPV. Both the spectral data indicate that the ISNPV binds the double helix structure of CT-DNA via an intercalation mode. Additionally, investigate the interactions of ISNPV with the protein molecules like BSA/HAS has been investigated using absorption and emission techniques. The absorption intensity of metal complex increases as well as the emission intensity of protein molecules ability decreases due to the binding nature of ISNPV with BSA/HSA protein molecules. The binding nature of ISNPV with bio molecules such as CT-DNA, BSA and HSA was also validated using molecular docking approach.

Binding elucidation of azo dyes with human serum albumin via spectroscopic approaches and molecular docking techniques

The large number of synthesized azo dyes is widely applied in the food, pharmaceutical, cosmetic, textile, and leather industries. In this study, the binding mechanism of two synthesized dyes with human serum albumin (HSA); as the most abundant protein in plasma; was elucidated by fluorescence spectroscopy, Fourier-transform infrared spectroscopy and molecular modeling methods. The fluorescence quenching measurements showed that each dye can quench the intrinsic fluorescence of HSA via a dynamic quenching mechanism with an increase in concentration. From the thermodynamic data observations, revealed that the binding process is a spontaneous molecular force for each dye with HSA due to hydrophobic interactions and hydrogen bonding. FT-IR spectra showed that the secondary structure of the protein changes due to interaction of each dye with HSA. Furthermore, docking simulation demonstrated that the probable binding location of both dyes is subdomain IIA of HSA (Sudlow site I) and that complex formed is stabilized by hydrophobic interactions and hydrogen bonding.Communicated by Ramaswamy H. Sarma.

Design and synthesis of atorvastatin derivatives with enhanced water solubility, hepatoselectivity and stability

Statins are effective 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-R) inhibitors, which are successfully used for cardiovascular disease treatment. Statins' side effects are generally attributed to poor bioavailability and hepatoselectivity, which are closely related to their high lipophilicity. Targeted delivery of statins to the liver is considered as a way to reduce unwanted side effects. Herein we report on synthesis and evaluation of atorvastatin conjugates targeting the galactose-specific hepatic asialoglycoprotein receptor (ASGPR). The prepared conjugates showed greater water solubility compared to unmodified atorvastatin. The synthesised compounds demonstrated potent binding to the ASGPR with submicromolar K D values. The conjugates with an amide bond connecting atorvastatin and the targeting moiety displayed the optimal stability under model conditions, as they underwent hydrolysis only when incubated with the intracellular protease. The hydrolysis products effectively inhibited HMG-R activity. The results suggest that the designed amide-based compounds have the potential to be further developed as orally administered prodrugs of atorvastatin.

DNA binding studies of antifungal drug posaconazole using spectroscopic and molecular docking methods

The binding studies of DNA with small molecules have been an emerging field of research all the time since DNA as the genetic material is a major biological target for various drugs. Interpretation of small molecule-DNA binding helps in understanding their interactions with designing new drugs of greater medicinal activity. Posaconazole is an antifungal drug in the class of triazoles which are known to possess numerous pharmacological properties. In this work, the nature of the binding of posaconazole with calf-thymus DNA has been studied using spectroscopic techniques and molecular docking studies. A binding constant of the order of 10³ M^-1 was observed from UV-visible and fluorescence studies for the interaction between posaconazole and calf-thymus DNA. The fluorescence property of posaconazole was found to be quenched by calf-thymus DNA with a quenching constant of the order of 10³ M^-1. Competitive displacement of ethidium bromide and Hoechst 33258 by posaconazole using fluorescence technique suggested minor groove binding of posaconazole in calf-thymus DNA. Confirmation of the binding mode was further complemented by the viscosity measurement and DNA melting studies followed by KI quenching experiments. The studies on the effect of ionic strength on the binding suggested a possible role of electrostatic force in the interaction. Molecular docking studies reflected a crescent shape of the posaconazole within the minor groove of calf-thymus DNA validating the experimental findings showing the residues involved in the interaction.

Binding ability of roxatidine acetate and roxatidine acetate supported chitosan nanoparticles towards bovine serum albumin: characterization, spectroscopic and molecular docking studies

The RxAc drug loaded on Tween80-chitosan-TPP nanoparticles (NRxAc) has been characterized and probed by UV-Vis, PXRD, FTIR, DLS and SEM technique. The physicochemical characteristics of NRxAc have been employed and evaluated for formulation of drug, particle size, external morphology, drug content and in vitro drug release. Multi-spectroscopic (i.e. fluorescence, UV-Vis, CD spectroscopy) and molecular docking techniques were also used to study the interaction of BSA with RxAc and NRxAc. RxAc and NRxAc quenched the fluorescence emission of BSA via a static quenching mechanism. The experimental data of Fluorescence demonstrated that the binding constant of RxAc and NRxAc were found around 10⁴ L.mol^-1, which suggests moderate binding affinity with BSA via hydrophobic forces. Through the site marker displacement experiments and molecular docking, the probable binding location of RxAc and NRxAc has been suggested in subdomain IB (site III) of BSA. Altogether, the results of present study can provide an important insight and a great deal of helpful information for future design of antiulcer drugs. Hence, The RxAc-loaded chitosan nanoparticles produced might be utilized as a successful tool for developing and using antiulcer drugs.Communicated by Ramaswamy H. Sarma.