Evaluation of the binding of perfluorinated compound to pepsin: Spectroscopic analysis and molecular docking

Binding interactions of Vildagliptin with pepsin: A multi-spectroscopic and in-silico approach and a comparative account with metformin

Vildagliptin (VDG) and Metformin (Met) belong to a class of dipeptidylpeptidase-4 (DPP-4) inhibitor and biguanide, respectively and used for the management of diabetes mellitus type II (DMTII). Both the drugs are orally available which leads to various side effects due to its oral ingestion. Occurrence of these side effects might be due to some interactions with pepsin at a molecular level. Therefore, in order to investigate these interactions, multi-spectroscopic and in-silico techniques have been extensively studied to identify the binding characteristics of VDG with pepsin. Fluorescence data suggested that the quenching is due to dynamic and static mechanism and static was dominant one. However, fluorescence and UV-Vis spectroscopic measurement analysis suggested that VDG tends to associate with pepsin, via ground-state complex formation. Fluorescence study revealed the binding-constant value which was found to be 0.559 × 103 M-1 at 298.15 K that is non-covalent in nature. VDG-pepsin complex shows exothermic and spontaneous binding as confirmed by the calculated values of ΔH, ΔS, and ΔG, are majorly caused by van der Waals forces and H-bonding interactions. CD spectra of pepsin in presence of VDG confirmed post binding conformational change. Enzyme-activity assay showed that activity of pepsin was decreased by upto 28 %. FRET analysis suggested that energy transfer efficiency is negligible for VDG-pepsin interaction. In-silico analysis reveals that H-bonding and electrostatic negative forces are the significant driving forces involved in the interaction of VDG and pepsin.

Tracing the Bioaccessibility of Per- and Polyfluoroalkyl Substances in Fish during Cooking Treatment

The effect of cooking on the contents of per- and polyfluoroalkyl substances (PFAS) in foods has been widely studied, but whether cooking-induced structural and chemical modifications in foods affect the oral bioaccessibility of PFAS remains largely unknown. In this study, three kinds of fishes with different fat contents were selected, and the bioaccessibility of PFAS during cooking treatment (steaming and frying) was evaluated using in vitro gastrointestinal simulation with gastric lipase addition. The results showed that related to their molecular structures, the bioaccessibility of an individual PFAS varied greatly, ranging from 26.0 to 108.1%. Cooking can reduce the bioaccessibility of PFAS, and steaming is more effective than oil-frying; one of the possible reasons for this result is that the PFAS is trapped in protein aggregates after heat treatment. Fish lipids and cooking oil ingested with meals exert different effects on the bioaccessibility of PFAS, which may be related to the state of the ingested lipid/oil and the degree of unsaturation of fatty acids. Gastric lipase boosted the release of long-chain PFAS during in vitro digestion, indicating that the degree of lipolysis considerably influences the bioaccessibility of hydrophobic PFAS. Estimated weekly PFAS intakes were recalibrated using bioaccessibility data, enabling more accurate and reliable dietary exposure assessments.

A review on structural mechanisms of protein-persistent organic pollutant (POP) interactions

With the advent of the industrial revolution, the accumulation of persistent organic pollutants (POPs) in the environment has become ubiquitous. POPs are halogen-containing organic molecules that accumulate, and remain in the environment for a long time, thus causing toxic effects in living organisms. POPs exhibit a high affinity towards biological macromolecules such as nucleic acids, proteins and lipids, causing genotoxicity and impairment of homeostasis in living organisms. Proteins are essential members of the biological assembly, as they stipulate all necessary processes for the survival of an organism. Owing to their stereochemical features, POPs and their metabolites form energetically favourable complexes with proteins, as supported by biological and dose-dependent toxicological studies. Although individual studies have reported the biological aspects of protein-POP interactions, no comprehensive study summarizing the structural mechanisms, thermodynamics and kinetics of protein-POP complexes is available. The current review identifies and classifies protein-POP interaction according to the structural and functional basis of proteins into five major protein targets, including digestive and other enzymes, serum proteins, transcription factors, transporters, and G-protein coupled receptors. Further, analysis detailing the molecular interactions and structural mechanism evidenced that H-bonds, van der Waals, and hydrophobic interactions essentially mediate the formation of protein-POP complexes. Moreover, interaction of POPs alters the protein conformation through kinetic and thermodynamic processes like competitive inhibition and allostery to modulate the cellular signalling processes, resulting in various pathological conditions such as cancers and inflammations. In summary, the review provides a comprehensive insight into the critical structural/molecular aspects of protein-POP interactions.

Exploration of binding mechanism of apigenin to pepsin: Spectroscopic analysis, molecular docking, enzyme activity and antioxidant assays

Pepsin plays an important role in nutrient metabolism. Apigenin (AP) is a beneficial polyphenol to human health. To enhance the bioavailability of AP and elucidate the inhibitory effect of AP on pepsin, the interaction mechanism of AP with pepsin was investigated using spectroscopic analysis and molecular docking, and the activity of pepsin and antioxidant activity of AP was also evaluated. Specifically, AP performed static quenching of pepsin and had only one binding site on pepsin. More interestingly, the interaction between AP and pepsin was spontaneous, while hydrogen bonds and van der Waals forces were the main binding forces. Generally, synchronous and three-dimensional fluorescence confirmed that AP induced the conformational changes of pepsin, and molecular docking proved the above results and illustrated the specific binding patterns. Specifically, AP inhibited the activity of pepsin, while pepsin decreased the antioxidant activity of AP. These results provided useful information for elucidating the interactions between AP and pepsin.

Perfluorooctanoic acid (PFOA)-induced alterations of biomolecules in the wetland plant Alismaorientale

Perfluoroalkyl substances (PFASs) have been widely studied by researchers due to their environmental persistence, chemical stability and potential toxicity. Some researchers have reported the physiological and biochemical toxicity of PFASs on plants through traditional and innovative methods; however, the changes in biological macromolecules caused by PFASs are rarely studied. Here, Fourier transform infrared spectroscopy (FTIR) was used to study how exposure to perfluorooctanoic acid (PFOA) alters the structure and function of biomolecules of the wetland plant Alisma orientale. Biomass results showed that PFOA had negative effects on plant growth. FTIR results showed that PFOA could result in changes in the structures, compositions, and functions of lipids, proteins and DNA in plant cells. In the treatment groups, the ratios of CH₃ to lipids and carbonyl esters to lipids increased compared with the control, while the ratios of CH₂ to lipids and olefinicCH to lipids decreased, which indicated lipid peroxidation caused by PFOA exposure. Changes in the compositions and secondary structures of proteins were also found, which were indicated by the decreased ratio of amide I to amide II and the increased ratio of β-sheet to α-helix in the treatment groups compared to the control. Moreover, PFOA affected the composition of DNA by promoting the B- to A-DNA transition. These results showed that the mechanism of PFOA toxicity toward plants at the biochemical level could be illustrated by FTIR.

A molecular dynamics simulation study of the ACE2 receptor with screened natural inhibitors to identify novel drug candidate against COVID-19

Background & Objectives

The massive outbreak of Novel Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) has turned out to be a serious global health issue worldwide. Currently, no drugs or vaccines are available for the treatment of COVID-19. The current computational study was attempted to identify a novel therapeutic inhibitor against novel SARS-CoV-2 using in silico drug discovery pipeline.

Methods

In the present study, the human angiotensin-converting enzyme 2 (ACE2) receptor was the target for the designing of drugs against the deadly virus. The 3D structure of the receptor was modeled & validated using a Swiss-model, Procheck & Errat server. A molecular docking study was performed between a group of natural & synthetic compounds having proven anti-viral activity with ACE2 receptor using Autodock tool 1.5.6. The molecular dynamics simulation study was performed using Desmond v 12 to evaluate the stability and interaction of the ACE2 receptor with a ligand.

Results

Based on the lowest binding energy, confirmation, and H-bond interaction, cinnamic acid (−5.20 kcal/mol), thymoquinone (−4.71 kcal/mol), and andrographolide (Kalmegh) (−4.00 kcal/mol) were screened out showing strong binding affinity to the active site of ACE2 receptor. MD simulations suggest that cinnamic acid, thymoquinone, and andrographolide (Kalmegh) could efficiently activate the biological pathway without changing the conformation in the binding site of the ACE2 receptor. The bioactivity and drug-likeness properties of compounds show their better pharmacological property and safer to use.

Interpretation & Conclusions

The study concludes the high potential of cinnamic acid, thymoquinone, and andrographolide against the SARS-CoV-2 ACE2 receptor protein. Thus, the molecular docking and MD simulation study will aid in understanding the molecular interaction between ligand and receptor binding site, thereby leading to novel therapeutic intervention.

Multi-spectral techniques and molecular docking to investigation of the interaction between ferulic acid and pepsin

In this work, the interaction between ferulic acid (FA) and pepsin was explored by UV-visible absorption spectroscopy, fluorescence spectroscopy, synchronous fluorescence, circular dichroism (CD) spectroscopy, Fourier transform infrared spectroscopy (FT-IR) and molecular docking. The results of fluorescence revealed that FA had a strong ability to quench the intrinsic fluorescence of pepsin through a static quenching procedure. The binding constant and the number of binding sites were determined. Thermodynamic dates and docking information suggest that FA combine with pepsin is mainly driven via electrostatic force. It also requires synergistic drive of hydrophobic and hydrogen bonding. The consequences from UV-Vis, synchronous, CD and FT-IR spectra measurements manifested that the secondary structure of pepsin was changed and the microenvironments of certain amino acid residues was modulated by the binding of FA. FA induced conformational changes in pepsin. The β-sheet, α-Helix, and Random fractions of pepsin increased and the β-turn decreased with the treatment of FA. In addition, analysis of pepsin activity assay measurements confirmed that FA reduced enzymatic activity of pepsin within the investigated concentrations. This work studied the inhibitory effects and revealed mechanisms of the interaction between FA and pepsin in vitro, and suggested that FA could be a potential component to affect the structure and properties of digestive enzyme.

Desorption of pharmaceuticals from pristine and aged polystyrene microplastics under simulated gastrointestinal conditions

Microplastics (MPs) in the environment usually undergo extensive weathering and can transport pollutants to organisms once being ingested. However, the transportation mechanism and effect of aging process are poorly understood. This study systematically investigated the desorption mechanisms of pharmaceuticals from pristine and aged polystyrene (PS) MPs under simulated gastric and intestinal conditions of marine organisms. Results showed that the increased desorption in stomach mainly depended on the solubilization of pepsin to pharmaceuticals and the competition for sorption sites on MPs via π-π and hydrophobic interactions. However, high desorption in gut relied on the solubilization of intestinal components (i.e. bovine serum albumin (BSA) and bile salts (NaT)) and the competitive sorption of NaT since the enhanced solubility increased the partition of pharmaceuticals in aqueous phase. Aging process suppressed the desorption of pharmaceuticals because aging decreased hydrophobic and π-π interactions but increased electrostatic interaction between aged MPs and pharmaceuticals, which became less affected by gastrointestinal components. Risk assessment indicated that the MP-associated pharmaceuticals posed low risks to organisms, and warm-blooded organisms suffered relatively higher risks than cold-blooded ones. This study reveals important information to understand the ecological risks of co-existed MPs and pollutants in the environment.

In-Silico Identification of Drug Lead Molecule Against Pesticide Exposed-neurodevelopmental Disorders Through Network-Based Computational Model Approach

Background:

Neurodevelopmental Disorders (NDDs) are impairment of the growth and development of the brain or central nervous system, which occurs at the developmental stage. This can include developmental brain dysfunction, which can manifest as neuropsychiatric problems or impaired motor function, learning, language or non-verbal communication. These include the array of disorder, including: Autism Spectrum Disorders (ASD), Attention Deficit Hyperactivity Disorders (ADHD) etc. There is no particular diagnosis and cure for NDDs. These disorders seem to be result from a combination of genetic, biological, psychosocial and environmental risk factors. Diverse scientific literature reveals the adverse effect of environmental factors specifically, exposure of pesticides, which leads to growing number of human pathological conditions; among these, neurodevelopmental disorder is an emerging issue nowadays.

Objective:

The current study focused on in silico identification of potential drug targets for pesticides induced neurodevelopmental disorder including Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder (ASD) and to design potential drug molecule for the target through drug discovery approaches.

Methods:

We identified 139 candidate genes for ADHD and 206 candidate genes for ASD from the NCBI database for detailed study. Protein-protein interaction network analysis was performed to identify key genes/proteins in the network by using STRING 10.0 database and Cytoscape 3.3.0 software. The 3D structure of target protein was built and validated. Molecular docking was performed against twenty seven possible phytochemicals i.e. beta amyrin, ajmaline, serpentine, urosolic, huperzine A etc. having neuroprotective activity. The best-docked compound was identified by the lowest Binding Energy (BE). Further, the prediction of drug-likeness and bioactivity analysis of leads were performed by using molinspiration cheminformatics software.

Result & Conclusion:

Based on betweenness centrality and node degree as a network topological parameter, solute carrier family 6 member 4 (SLC6A4) was identified as a common key protein in both the networks. 3-D structure of SLC6A4 protein was designed and validated respectively. Based on the lowest binding energy, beta amyrin (B.E = -8.54 kcal/mol) was selected as a potential drug candidate against SLC6A4 protein. Prediction of drug-likeness and bioactivity analysis of leads showed drug candidate as a potential inhibitor. Beta amyrin (CID: 73145) was obtained as the most potential therapeutic inhibitor for ASD & ADHD in human.

Biochemical and toxicological investigation of karanjin, a bio-pesticide isolated from Pongamia seed oil

Karanjin, a furanoflavonol from Pongamia pinnata L is used in agricultural practices for its pesticidal, insecticidal and acaricidal activities. It is commercially available as a bio-pesticide targeting a wide variety of pests. The present study was intended to evaluate the biochemical interactions of karanjin with bovine serum albumin (BSA) and study its toxicological effects on mammalian and bacterial cell lines. Karanjin bound to BSA at a single site with a dissociation constant of 19.7 μM. Evaluation of BSA-karanjin interactions at three different temperatures indicated the involvement of static mode of quenching. Binding experiments in the presence of warfarin and computational docking analysis indicated that karanjin bound closer to the warfarin binding site located in the Subdomain IIA of BSA. Using Förster resonance energy transfer analysis the distance between TRP 213 of BSA and karanjin was found to be 20 Å. Collective results from synchronous fluorescence spectra analysis, differential scanning calorimetry, and circular dichroism analysis indicated that binding of karanjin induced conformational changes in the secondary structure of BSA. Karanjin exhibited low toxicity against human cervical cancer cells and normal mouse fibroblast L929 cells and modestly inhibited the growth of B. subtilis and E. coli cells. The data presented in this study provides insights for understanding the binding interactions of karanjin with BSA and its possible toxicological effects on mammalian cell lines and bacteria.

Streptozocin; a GLUT2 binding drug, interacts with human serum albumin at loci h6DOM3-h7DOM3

Streptozocin (STZ) is a broad range antibiotic, highly genotoxic, antineoplastic and hyperglycemic. HSA is the most abundant protein in physiology and it binds to almost all exogenic and endogenic ligands, including drugs. STZ-induced fluorescence quenching of HSA has been done at pH 7.4, pH 3.5 and at pH 7.4 with 4.5 M urea at temperatures 286 K, 291 K, and 306 K. K_sv found to be 10³ M^-1, binding constant 1.5X10³M^-1 and binding sites ~1. But, K_sv for HSA and glucopyranose interaction was found lesser than that of HSA-STZ binding. Binding of STZ/glucopyranose on HSA seems to result in complex formation as calculated K_q > 10¹⁰ M^-1 s^-1. The number of binding sites, binding constants, and binding energies were increased with temperature. The ΔG⁰, ΔH⁰, and ΔS⁰ for HSA-STZ interaction were found to be -17.7 × 10³ J·mol^-1; 2.34 × 10⁵ J·mol^-1 and 841 JK^-1 mol^-1 respectively at pH 7.4 and 291 K. The comparative bindings of N, F and I states of HSA with STZ and their molecular docking analyses indicate that IIIA-B junction (i.e., inter-helix h6_DOM3-h7_DOM3) is the probable binding site, a locus close to fatty acid binding site-5. These results could be useful for therapeutic and analytical exploitation of STZ, as albumin used as the vehicle for drug delivery.

Binding of triclosan and triclocarban to pepsin: DFT, spectroscopic and dynamic simulation studies

The use of antibacterial agents, triclosan (TCS) and triclocarban (TCC), in personal care products can result in direct human exposure. Density Functional Theory (DFT) was utilized to evaluate the electronic properties of TCS and TCC, and the determined energetically accessible transitions across the HOMO-LUMO gap. Choosing pepsin as a model protein, we explored the binding effects of TCS or TCC on pepsin by molecular docking and dynamic simulations. Titration of pepsin with TCS or TCC at pH 2.2 led to quenching of the pepsin intrinsic fluorescence via formation of a ground-state complex. The binding constants of the TCS/TCC-pepsin complexes, determined at 296 K, were (7.053 ± 0.030) × 10⁴ M^-1 and (6.233 ± 0.060) × 10⁴ M^-1, respectively. Analysis of the thermodynamic properties of each system at various temperatures demonstrated that the binding reaction is a spontaneous process driven by hydrophobic interactions. The spectroscopic results revealed that changes in the secondary structure of pepsin are induced by TCS or TCC. The thermal stability of pepsin was evaluated, and no change in thermal stability was observed upon substrate binding. However, the binding of either TCS or TCC to pepsin effectively reduced the activity.

Bioaccessibility and exposure assessment of trace metals from urban airborne particulate matter (PM10 and PM2.5) in simulated digestive fluid

We describe a batch-extraction with simulated digestive fluid (salivary fluid, gastric fluid and intestinal fluid) to estimate the bioaccessibility of inhaled trace metals (TMs) in particulate matter less than 10 and 2.5 μm in aerodynamic diameter (PM₁₀ and PM_2.5). Concentrations of the assayed TMs (As, Cd, Cr, Ni, Mn, Cu, Zn, Sb, Hg and Pb) were determined in PM₁₀ and PM_2.5 samples by inductively coupled plasma-mass spectrometry. The TMs with the largest soluble fractions for airborne PM collected from winter and summer in saliva were Mn and Sb, respectively; in seasons this became Co in gastric fluid and Cu in intestinal fluid. Clearly, bioaccessibility is strongly dependent on particle size, the component of simulated digestive fluids (e.g., pH, digestive enzymes pepsin and trypsin), and the chemical properties of metal ions. The particle size and seasonal variation affected the inhaled bioaccessible fraction of PM-bound TMs during mucociliary clearance, which transported PM from the tracheal and the bronchial region to the digestive system. This study provides direct evidence for TMs in airborne PM being bioaccessible TMs are likely to possess an enhanced digestive toxic potential due to airborne PM pollution.

Role of cationic carbosilane dendrons and metallic core of functionalized gold nanoparticles in their interaction with human serum albumin

Functionalization of gold nanoparticles by different chemical groups is an important issue regarding the biomedical applications of such particles. Therefore we have analyzed the interaction between gold nanoparticles functionalized by carbosilane dendrons with human serum albumin at different pHs, and in the presence of the protein unfolding agent, guanidine hydrochloride, using circular dichroism, zeta-potential and fluorescence quenching. The effect of a nanoparticle dendronization and pure dendrons on the immunoreactivity of albumin was estimated using ELISA. In addition, the tool to estimate the binding capacity of dendronized gold nanoparticles using a hydrophobic fluorescent probe 1,8-ANS (1-anilinonaphthalene-8-sulfonic acid) was chosen. We concluded that the effect of a nanoparticle on the structure, immunochemical properties and unfolding of albumin significantly decreased with second and third generations dendrons attached. Differences in pH dependence of the interaction between nanoparticles, their dendrons and albumin showed several effects of the "dendritic corona" and the metallic part of nanoparticle on the protein. These interactions indicate changes in the immunoreactivity of the protein, whereas dendron coating per se had no effect. Thus, dendronization of gold nanoparticles helps to shield them from interactions with plasma proteins.

Characterizing the binding interactions of PFOA and PFOS with catalase at the molecular level

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have effects on human health by inducing oxidative stress and catalase (CAT) is a vital enzyme involved in protection against oxidative damage. The interactions of PFOA and PFOS with CAT were investigated by using biophysical methods including spectroscopic techniques, molecular docking and enzyme activity measurements. UV-visible, circular dichroism (CD) and resonance light scattering (RLS) spectroscopy results showed that the structure and conformation of CAT were changed by PFOA and PFOS. PFOA could loosen and unfold the skeleton of CAT but PFOS affected the microenvironment around the aromatic amino acid residues and heme groups. Both PFOA and PFOS altered the secondary structure of CAT by decreasing α-helix and increasing β-sheet content. The size of CAT was smaller and CAT became dispersed when it was bound by perfluorinated compounds (PFCs). Furthermore, enzyme activity test showed that PFOS decreased the activity of CAT because the binding site of PFOS was close to the active center of CAT, but PFOA had little effect on the activity because PFOA bound at the surface of the enzyme. These results indicated that PFCs could damage the structures and conformations of CAT but the changes were not always related to the activity and function of CAT.

Interactions of perfluorooctanoic acid and perfluorooctanesulfonic acid with serum albumins by native mass spectrometry, fluorescence and molecular docking

The binding information of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) with bovine and human serum albumins was investigated and characterized in details by using a combination method of electrospray ionization mass spectrometry (ESI-MS), fluorescence, circular dichroism (CD) and molecular docking (MD). The ESI-MS analysis revealed that maximally eight PFOA or PFOS molecules could bind to serum albumins at high mole ratios of PFOA/PFOS. Association constants were measured by ESI-MS and suggested that PFOS had a better binding affinity than PFOA. PFOA and PFOS were likely to bind with serum albumins in more than one pocket. The CD data demonstrated that binding of PFOA and PFOS could change the conformation of serum albumins with decreasing α-helix content, which may affect the protein physiological function. The phenomenon of protein fluorescence quenching by the binding of PFOA and PFOS indicated that the hydrophobic pocket proximate to Trp 214 in human serum albumin might be one of the dominated binding sites. This assumption was further confirmed by MD simulation. Consistent to ESI-MS observation, MD results also displayed a stronger binding affinity of PFOS than PFOA according to the calculated binding free energy, which is probably ascribed to one more hydrogen bond formed in the PFOS-bound protein complexes.

Association of iminium and alkanolamine forms of the benzo[c]phenanthridine alkaloid chelerythrine with human serum albumin: photophysical, thermodynamic and theoretical approach

Association of isoforms of chelerythrine (CHL) with HSA.

The mechanism and conformational changes of polybrominated diphenyl ethers to TTR by fluorescence spectroscopy, molecular simulation, and quantum chemistry

Free energy contribution of amino acid LYS (B and D chains) and PDBEs was analyzed combining quantum chemistry and molecular modeling.

Probing the binding properties of dicyandiamide with pepsin by spectroscopy and docking methods

Dicyandiamide (DCD), considered to be a nitrification inhibitor, poses threat to human's health with exposure from milk, infant formula and other food products. In this work, DCD was investigated for its binding reaction with pepsin using spectroscopy and docking methods. Fluorescence experiments indicated DCD quenched the fluorescence of pepsin through a static process. Thermodynamic analysis of the binding data (ΔH⁰ = -21.72 kJ mol^-1 and ΔS⁰ = 17.61 J mol^-1 K^-1) suggested the involvement of hydrophobic and hydrogen bonding in the complex formation. The pepsin interacted with DCD at a hydrophobic cavity, leading to a conformational changes in the pepsin, as revealed from UV-vis absorption, Fourier transform infrared, the time-resolved fluorescence, three-dimensional fluorescence and circular dichroism spectral results.

Sensitive and Selective "Turn-On" Chemodosimetric Probes for Fe3+ Based on a Skeleton of 2-Hydroxy-1-Naphthaldehyde

A naked-eye colored chemodosimeteric probes 4a-f, based on Schiff-azo dye conjugates were synthesized and characterized. All compounds 4a-f exhibited excellent selectivity and high sensitivity in absorbance toward detection of Fe³⁺ in alcoholic solutions under neutral pH conditions. The detection limit of the probe was shown to be up to 0.05 ppm. A simple paper test strip system for the rapid monitoring of Fe³⁺ was developed, indicating their convenient use in environmental samples. Electrochemical analysis of metal free conjugates and iron chelated probes confirmed the chelation of ligands. Graphical Abstract.

Probing the mechanism of interaction of metoprolol succinate with human serum albumin by spectroscopic and molecular docking analysis

In the present work, the mechanism of the interaction between a β1 receptor blocker, metoprolol succinate (MS) and human serum albumin (HSA) under physiological conditions was investigated by spectroscopic techniques, namely fluorescence, Fourier transform infra-red spectroscopy (FT-IR), fluorescence lifetime decay and circular dichroism (CD) as well as molecular docking and cyclic voltammetric methods. The fluorescence and lifetime decay results indicated that MS quenched the intrinsic intensity of HSA through a static quenching mechanism. The Stern-Volmer quenching constants and binding constants for the MS-HSA system at 293, 298 and 303 K were obtained from the Stern-Volmer plot. Thermodynamic parameters for the interaction of MS with HSA were evaluated; negative values of entropy change (ΔG°) indicated the spontaneity of the MS and HSA interaction. Thermodynamic parameters such as negative ΔH° and positive ΔS° values revealed that hydrogen bonding and hydrophobic forces played a major role in MS-HSA interaction and stabilized the complex. The binding site for MS in HSA was identified by competitive site probe experiments and molecular docking studies. These results indicated that MS was bound to HSA at Sudlow's site I. The efficiency of energy transfer and the distance between the donor (HSA) and acceptor (MS) was calculated based on the theory of Fosters' resonance energy transfer (FRET). Three-dimensional fluorescence spectra and CD results revealed that the binding of MS to HSA resulted in an obvious change in the conformation of HSA. Cyclic voltammograms of the MS-HSA system also confirmed the interaction between MS and HSA. Furthermore, the effects of metal ions on the binding of MS to HSA were also studied.

Novel poly(ADP-ribose) polymerase inhibitor veliparib: biophysical studies on its binding to calf thymus DNA

Veliparib, an new anticancer drug in the class of poly (ADP-ribose) polymerase inhibitors, intercalates partially and binds to ctDNA and induces moderate conformational perturbation of the DNA.

Interaction of serum albumins with fluorescent ligand 4-azido coumarin: spectroscopic analysis and molecular docking studies

The investigation of the binding of 4-AC to biomolecular systems using photophysical techniques and molecular docking studies.

A novel Pd(ii) CNO pincer complex of MR (methyl red): synthesis, crystal structure, interaction with human serum albumin (HSA) in vitro and molecular docking

The C–H activation of methyl red (MR) (MR = 2-{[4-(dimethylamino)phenyl]diazenyl}benzoic acid) was achieved by reaction with Pd(OAc)₂under mild conditions.