Binding studies of L-3,4-dihydroxyphenylalanine with human serum albumin

Synthesis and structural elucidation of a unique turn-off fluorescent sensor based on oxo-bridged tin (IV) cluster for selective detection of dopamine in biological fluids

An oxo-bridged Sn (IV) Cluster, (TOC) was synthesized and fully characterized by FT-IR, UV-vis, 1H NMR, 119Sn NMR, Mass spectrometry and single crystal X-ray diffraction studies. The single-crystal X-ray analysis revealed that the crystal crystallizes in the monoclinic crystal system possessing the P 21/c space group and exhibited a distorted trigonal bipyramidal geometry. The TOC exhibited a unique turn-off fluorescence response for the selective detection of dopamine (DA) over other analytes. The stoichiometry between the TOC and DA was calculated using Job's plot. The value of the detection limit was found to be 1.33 µM. The Hirshfeld surface analysis was carried out on the crystal structure to investigate the H-H, Cl-H, Cl-Cl, Sn-Cl and Cl-C interaction studies in the molecule. Density Functional Theory (DFT) studies further supported the sensing mechanism, which closely agreed with the experimental results. Furthermore, the TOC chemosensor was used to detect DA in human blood plasma, and molecular docking studies validated the interaction between the chemosensor and protein. Confocal fluorescence imaging studies were carried out and validated TOC sensing ability for DA in human blood plasma.

Investigation on the binding behavior of human α1-acid glycoprotein with Janus Kinase inhibitor baricitinib: Multi-spectroscopic and molecular simulation methodologies

Baricitinib is a Janus Kinase (JAK) inhibitor that is primarily used to treat moderately to severely active rheumatoid arthritis in adults and has recently been reported for the treatment of patients with severe COVID-19. This paper describes the investigation of the binding behavior of baricitinib to human α1-acid glycoprotein (HAG) employing a variety of spectroscopic techniques, molecular docking and dynamics simulations. Baricitinib can quench the fluorescence from amino acids in HAG through a mix of dynamic and static quenching, according to steady-state fluorescence and UV spectra observations, but it is mainly static quenching at low concentration. The binding constant (K_b) of baricitinib to HAG at 298 K was at the level of 10⁴ M^-1, indicating a moderate affinity of baricitinib to HAG. Hydrogen bonding and hydrophobic interactions conducted the main effect, according to thermodynamic characteristics, competition studies between ANS and sucrose, and molecular dynamics simulations. For the change in HAG conformation, the results of multiple spectra showed that baricitinib was able to alter the secondary structure of HAG as well as increase the polarity of the microenvironment around the Trp amino acid. Furthermore, the binding behavior of baricitinib to HAG was investigated by molecular docking and molecular dynamics simulations, which validated experimental results. Also explored is the influence of K⁺, Co²⁺, Ni²⁺, Ca²⁺, Fe³⁺, Zn²⁺, Mg²⁺ and Cu²⁺plasma on binding affinity.

Patient-specific in vitro drug release testing coupled with in silico PBPK modeling to forecast the in vivo performance of oral extended-release levodopa formulations in Parkinson's disease patients

Biorelevant in vitro release models are valuable analytical tools for oral drug development but often tailored to gastrointestinal conditions in 'average' healthy adults. However, predicting in vivo performance in individual patients whose gastrointestinal conditions do not match those of healthy adults would be of great value for optimizing oral drug therapy for such patients. This study focused on establishing patient-specific in vitro and in silico models to predict the in vivo performance of levodopa extended-release products in Parkinsońs disease patients. Current knowledge on gastrointestinal conditions in these patients was incorporated into model development. Relevant in vivo pharmacokinetic data and patient-specific in vitro release data from a novel in vitro test setup were integrated into patient-specific physiologically-based pharmacokinetic models. AUC, c_max and t_max of the computed plasma profiles were calculated using PK-Sim®. For the products studied, levodopa plasma concentration-time profiles modeled using this novel approach compared far better with published average plasma profiles in Parkinsońs disease patients than those derived from in vitro release data obtained from the 'average' healthy adult setup. Although further work is needed, results of this study highlight the importance of addressing patient-specific gastrointestinal conditions when aiming to predict drug release in such specific patient groups.

A Metabolomic Analysis of Cirrhotic Ascites

Ascites is a common complication of decompensated liver cirrhosis, and yet relatively little is known about its biochemical composition. We conducted two metabolomic investigations, comparing the profile of ascites from 33 cirrhotic patients and postoperative peritoneal drainage fluid from 33 surgical patients (Experiment 1). The profile of paired ascites and plasma was also compared in 17 cirrhotic patients (Experiment 2). Gas chromatography−mass spectrometry-based metabolomics identified 29 metabolites that significantly characterized ascites fluid, whether postoperative drainage fluid or plasma were used as controls. Ten elevated amino acids (glutamine, proline, histidine, tyrosine, glycine, valine, threonine, methionine, lysine, phenylalanine) and seven diminished lipids (laurate, myristate, palmitate, oleate, vaccenate, stearate, cholesterol) largely comprised the cirrhotic ascites metabolomic phenotype that differed significantly (adjusted p < 0.002 to 0.03) from peritoneal drainage fluid or plasma. The pattern of upregulated amino acids in cirrhotic ascites did not indicate albumin proteolysis by peritoneal bacteria. Bidirectional clustering showed that the more severe the cirrhosis, the lower the lipid concentration in ascitic fluid. The metabolomic compartment of ascites in patients with decompensated cirrhosis is characterized by increased amino acids and decreased lipids. These novel findings have potential relevance for diagnostic purposes.

Multi-Spectroscopic, thermodynamic and molecular docking studies to investigate the interaction of eplerenone with human serum albumin

The binding of small molecular drugs with human serum albumin (HSA) has a crucial influence on their pharmacokinetics. The binding interaction between the antihypertensive Eplerenone (EPL)and HSA was investigated using multi-spectroscopic techniques for the first time. These techniques include UV-Vis spectroscopy, Fourier Transform Infrared (FT-IR), native fluorescence spectroscopy, synchronous fluorescence spectroscopy and molecular docking approach. The fluorescence spectroscopic study showed that EPL quenched HSA inherent fluorescence. The mechanism for quenching of HSA by EPL has been determined to be static in nature and confirmed by UV absorption and fluorescence spectroscopy. The modified Stern-Volmer equation was used to estimate the binding constant (K_b ) as well as the number of bindings (n). The results indicated that the binding occurs at a single site (Kb;2.238 x 10³ L mol^-1 at 298 K). The enthalpy and entropy changes (∆H and ∆S) were 58.061 and 0.258 K J mol^-1 , respectively, illustrating that the principal intermolecular interactions stabilizing the EPL-HSA system are hydrophobic forces. Synchronous fluorescence spectroscopy revealed that EPL binding to HSA occurred around the tyrosine residue (Tyr) and this agreed with the molecular docking study. The FRET analysis confirmed the static quenching mechanism. The esterase enzyme activity of HSA was also evaluated showing its decrease in the presence of EPL. Furthermore, docking analysis and site-specific markers experiment revealed that EPL binds with HSA at subdomain IB (site III).

Spectroscopic study of L-DOPA and dopamine binding on novel gold nanoparticles towards more efficient drug-delivery system for Parkinson's disease

Nano-drug delivery systems may potentially overcome current challenges in the treatment of Parkinson's disease (PD) by enabling targeted delivery and more efficient blood-brain penetration ability. This study investigates novel gold nanoparticles (AuNPs) to be used as delivery systems for L-DOPA and dopamine by considering their binding capabilities in the presence and absence of a model protein, bovine serum albumin (BSA). Four different AuNPs were prepared by surface functionalization with polyethylene glycol (PEG), 1-adamantylamine (Ad), 1-adamantylglycine (AdGly), and peptidoglycan monomer (PGM). Fluorescence and UV-Vis measurements demonstrated the strongest binding affinity and L-DOPA/dopamine loading efficiency for PGM-functionalized AuNPs with negligible impact of the serum protein presence. Thermodynamic analysis revealed a spontaneous binding process between L-DOPA or dopamine and AuNPs that predominantly occurred through van der Waals interactions/hydrogen bonds or electrostatic interactions. These results represent PGM-functionalized AuNPs as the most efficient at L-DOPA and dopamine binding with a potential to become a drug-delivery system for neurodegenerative diseases. Detailed investigation of L-DOPA/dopamine interactions with different AuNPs was described here for the first time. Moreover, this study highlights a cost- and time-effective methodology for evaluating drug binding to nanomaterials.

Interaction of remimazolam benzenesulfonate and human serum albumin: a simulated physiological study

Here, to elucidate the interaction mechanism and physicochemical properties of remimazolam and human serum albumin interactions, techniques such as fluorescence, circular dichroism (CD) spectroscopy, and isothermal titration calorimetry have been applied for study. The thermodynamic parameters at body temperature (ΔS = -207 J·mol^-1 ·K^-1 , ΔS = -9.76 × 10⁴  J·mol^-1 and ΔG = -3.34 × 10⁴  J·mol^-1 ; 310 K) manifests one strong binding site on the protein, which was modulated by van der Waals forces and hydrogen bonds. What is more, the results of CD, synchronous and three-dimensional fluorescence showed that remimazolam altered the microenvironment of the protein amino acid residues. A distance of 2.1 nm between the remimazolam and Trp shows the potential for resonance energy transfer. Furthermore, these results potentially provide information for illustrating the pharmacodynamics and toxicodynamics of remimazolam when it is applied clinically.

Multi-spectroscopic and molecular docking studies for binding interaction between fluvoxamine and human serum albumin

In the present study, different spectroscopic techniques have been used to study the binding interaction between the antidepressant drug fluvoxamine and human serum albumin under simulated physiological conditions (pH 7.4). The utilized spectroscopic techniques include fluorescence emission spectroscopy, synchronous fluorescence spectroscopy, UV-Vis absorption spectroscopy, Fourier Transform Infrared spectroscopy (FT-IR), and molecular modeling methods. The obtained results revealed that the formation of a complex between human serum albumin and fluvoxamine was responsible for quenching the native fluorescence of human serum albumin. The results indicated that the quenching mechanism between human serum albumin and fluvoxamine was static. Besides, the binding constant (K), number of binding sites (n), thermodynamic parameters (ΔH, ΔS, and ΔG), and binding forces were calculated at three different temperatures (298, 310, and 318 K). These data proposed that hydrophobic forces were the principal intermolecular forces stabilizing the complex. From the molecular docking results, it could be deduced that fluvoxamine was inserted into sub-domain II A (site I) of human serum albumin and led to a slight change in human serum albumin conformation.

Development of an In Vitro Airway Epithelial-Endothelial Cell Culture Model on a Flexible Porous Poly(Trimethylene Carbonate) Membrane Based on Calu-3 Airway Epithelial Cells and Lung Microvascular Endothelial Cells

Due to the continuing high impact of lung diseases on society and the emergence of new respiratory viruses, such as SARS-CoV-2, there is a great need for in vitro lung models that more accurately recapitulate the in vivo situation than current models based on lung epithelial cell cultures on stiff membranes. Therefore, we developed an in vitro airway epithelial–endothelial cell culture model based on Calu-3 human lung epithelial cells and human lung microvascular endothelial cells (LMVECs), cultured on opposite sides of flexible porous poly(trimethylene carbonate) (PTMC) membranes. Calu-3 cells, cultured for two weeks at an air–liquid interface (ALI), showed good expression of the tight junction (TJ) protein Zonula Occludens 1 (ZO-1). LMVECs cultured submerged for three weeks were CD31-positive, but the expression was diffuse and not localized at the cell membrane. Barrier functions of the Calu-3 cell cultures and the co-cultures with LMVECs were good, as determined by electrical resistance measurements and fluorescein isothiocyanate-dextran (FITC-dextran) permeability assays. Importantly, the Calu-3/LMVEC co-cultures showed better cell viability and barrier function than mono-cultures. Moreover, there was no evidence for epithelial- and endothelial-to-mesenchymal transition (EMT and EndoMT, respectively) based on staining for the mesenchymal markers vimentin and α-SMA, respectively. These results indicate the potential of this new airway epithelial–endothelial model for lung research. In addition, since the PTMC membrane is flexible, the model can be expanded by introducing cyclic stretch for enabling mechanical stimulation of the cells. Furthermore, the model can form the basis for biomimetic airway epithelial–endothelial and alveolar–endothelial models with primary lung epithelial cells.

Ex vivo binding studies of the anti-cancer drug noscapine with human hemoglobin: a spectroscopic and molecular docking study

Noscapine binds human hemoglobin spontaneously forming a stable complex that affects noscapine's ADMET profile, bioavailability and toxicity.

Exploring the binding mechanisms of inorganic magnetic nanocarrier containing L-Dopa with HSA protein utilizing multi spectroscopic techniques

In this study, the interaction of Fe₃O₄@CaAl-LDH@L-Dopa nanoparticles (NPs) with human serum albumin (HSA) was investigated in simulated physiological conditions applying UV-visible, fluorescence, and circular dichroism (CD) spectroscopic techniques. The consequences of UV-vis and CD spectroscopy demonstrated that the interaction of HSA to Fe₃O₄@CaAl-LDH@L-Dopa NPs enforced some conformational alterations within HSA. The fluorescence spectroscopy analysis indicated that by enhancing temperature, the Stern-Volmer quenching constant (K_sv) was decreased, which is relevant to a static quenching mechanism. The binding constant (K_b) was 7.07 × 10⁴ M^-1 while the number of the binding site (n) was 0.94 which is in compromise with its binding constant. Also, thermodynamic parameters (ΔH° > 0, ΔG° < 0, and ΔS° > 0) have suggested that hydrophobic forces perform a key role in the interaction of HSA with Fe₃O₄@CaAl-LDH@L-Dopa NPs. Displacement studies successfully carried out using the Warfarin and Ibuprofen have predicted that the binding of Fe₃O₄@CaAl-LDH@L-Dopa NPs to HSA is situated at site II (subdomain IIIA).Communicated by Ramaswamy H. Sarma.

Binding of levobupivacaine-loaded gold nanoparticles to human serum albumin: a simulated physiological study

Techniques such as Fourier transform infrared (FTIR), ultraviolet-visible (UV-vis) spectra, fluorescence, circular dichroism (CD) and spectroscopy were applied to elucidate the formation, structure and physicochemical properties of levobupivacaine-gold nanoparticle (LGN) binding to human serum albumin (HSA). Thermodynamic parameters (ΔG = -2.58 × 10⁴ J·mol^-1 , ΔS = -7.80 J·mol^-1 ·K^-1 , and ΔS = -2.82 × 10⁴ J·mol^-1 at 305 K) suggested one weak binding site on HSA, which was governed by van der Waals forces as well as hydrogen bonds. Moreover, the outcomes of UV-vis, CD, FTIR, synchronous and three-dimensional fluorescence suggested that the microenvironment of HSA had been changed with addition of LGN. Based on the results of fluorescence resonance energy transfer, a distance of 2.8 nm between the LGN and HSA was observed. This approach has potential value for illustrating the pharmacodynamics of LGN when in combination with transmembrane transport, biomolecular function effect, and other experiments.

Bound, free, and total L-dopa measurement in plasma of Parkinson's disease patients

Peaks and troughs of levodopa in plasma contribute to pulsatile postsynaptic dopamine receptor stimulation in patients with Parkinson's disease. Measurement of levodopa plasma levels mostly only considers the total levodopa plasma concentration. Objectives were to determine bound, free, and total plasma levodopa and to investigate their correlations to each other. We employed reversed-phase high-performance liquid chromatography combined with electrochemical detection. Bound levodopa was computed as difference between total and free L-dopa values. Close correlations between free and total (R = 0.93, p < 0.0001), bound and total (R = 0.91, p < 0.0001) plasma levodopa appeared. A considerable variability of levodopa concentrations occurred. The ratio between bound and free levodopa did not differ in patients with a higher and lower oral daily levodopa dosing. Free, bound, and total levodopa plasma levels are closely related. Estimation of the total levodopa level only seems to be meaningful.

Steroidal thiazolidinone derivatives: Design, synthesis and their molecular interaction with human serum albumin

A series of steroidal thiazolidinone derivatives have been synthesized through one-pot multicomponent reaction involving steroidal ketone, thiosemicarbazide/methyl-thiosemicarbazide and DMAD in presence of AlCl₃ as a Lewis acid catalyst. Among all the synthesized steroidal thiazolidinone derivatives, compound 7-9 (ST 7-9) were investigated for their in vitro molecular interaction with human serum albumin. Intrinsic fluorescence spectroscopy, constant wavelength synchronous fluorescence spectroscopy, circular dichroism and UV-visible absorption techniques have been exploited to characterize the binding phenomena in phosphate buffer solution at pH 7.4. The experimental results indicated that ST 7-9 bind to HSA and the intrinsic fluorescence of HSA was quenched through static quenching mechanism. The binding parameters were calculated and the binding constants obtained were 1.44 × 10⁵ M^-1 for ST 7, 0.84 × 10⁵ M^-1 for ST 8 and 1.06 × 10⁵ M^-1 for ST 9. Circular dichroism analysis confirms that the presence of ST 7-9, altered the secondary structure of HSA due to partial unfolding of the polypeptide chain. Furthermore, hemolytic activity assay demonstrated that the synthesized steroidal thiazolidinone derivatives have good compatibility towards human red blood cells. Finally, molecular docking studies revealed that the steroidal thiazolidinones can bind in the hydrophobic cavity of HSA, by hydrophobic and hydrogen bonding interaction. These results provided valuable information about the binding mechanism of ST 7-9 with HSA and play a pivotal role in the development of steroidal heterocycle inspired compounds.

Elucidating the active interaction mechanism of phytochemicals withanolide and withanoside derivatives with human serum albumin

Withania somnifera (Ashwagandha) is an efficient medicinal plant known in Ayurveda and Chinese medicine since ancient times, whose extracts are consumed orally as food supplement or as a health tonic owing to its several restorative properties for various CNS disorders, inflammation, tumour, stress, rheumatism etc. In this study, we have analyzed the binding interaction of four derivatives of Withania somnifera (Withanolide A, Withanolide B, Withanoside IV and Withanoside V) with HSA because of their important pharmacological properties. To unravel the binding between derivatives of Withania somnifera and HSA, fluorescence spectroscopy was used. Binding studies were further studied by molecular docking and dynamics and results confirmed greater stability upon binding of derivatives with HSA. Circular dichroism data illustrated change in the secondary structure of protein upon interaction with these derivatives, particularly the helical structure was increased and β-sheets and random coils were decreased. Furthermore, morphological and topological changes were observed using AFM and TEM upon binding of ligands with HSA indicating that HSA-withnoside/withanolide complexes were formed. All the results cumulatively demonstrate strong binding of withanosides and withanolides derivatives with serum albumin, which should further be explored to study the pharmacokinetics and pharmacodynamics of these derivatives.

Insights into the binding mechanism of BODIPY-based photosensitizers to human serum albumin: A combined experimental and computational study

Photodynamic therapy (PDT) is a noninvasive and effective approach in clinical cancer treatments. Boron-dipyrromethene (BODIPY)-based derivatives have emerged as novel and promising photosensitizers (PSs) in PDT, attributed to their strong near-infrared singlet oxygen luminescence emissions and high photostabilities. However, the binding mechanism of BODIPY derivatives to proteins, key for their therapeutic and biomedical applications is still poorly understood. Here, we investigated the molecular interactions of two 2, 6-diiodo-BODIPY derivatives with human serum albumin (HSA) using combined experimental and computational techniques. Our spectroscopic results showed that both BODIPY derivatives formed stable complexes with HSA. Strikingly, the BODIPY/HSA complexes exhibited notably enhanced water solubility and singlet oxygen generation efficiency with respect to the BODIPY alone. Furthermore, molecular docking, molecular dynamics simulations, and binding free energy calculations provided the structural and energetic insights into the binding mechanism of BODIPY-based derivatives to HSA. Our work demonstrated that conjugation of BODIPYs with HSA may be a promising strategy to enhance the performance of BODIPY-based PSs, and the combination of computational and experimental techniques is expected to play key roles in the design and development of novel PSs with improved bioavailability and biocompatibility for cancer therapeutic applications.

Sudlow site II of human serum albumin remains functional after gold nanocluster encapsulation: a fluorescence-based drug binding study of L-Dopa

Fluorescent protein-encapsulated gold nanoclusters (AuNCs) offer a non-toxic means of sensing and imaging biological phenomena on the nanoscale. However, the biofunctionality of proteins encapsulating AuNCs has not been fully elucidated to date. Here we studied the biofunctionality of the second major drug binding site (Sudlow II) of Human Serum Albumin (HSA) encapsulated AuNCs after AuNC synthesis. L-Dopa, a fluorescent drug molecule associated with the clinical treatment of Parkinson's disease, which commonly binds to the Sudlow II site, was used to study the availability of the site before and after AuNC synthesis through changes to its fluorescence characteristics. L-Dopa was observed using its intrinsic fluorescence to readily bind to HSA-AuNCs complexes. Interestingly, the fluorescence emission intensity of AuNCs linearly increased with L-Dopa concentration while exciting the AuNC directly at 470 nm, Using a 400 nM HSA-AuNC solution, L-Dopa was rapidly detected at a limit of 300 pM, indicating that HSA-AuNCs fluorescence is extremely sensitive to molecular binding at the Sudlow II binding site. Future research may be able to utilize this sensitivity to improve the fluorescence characteristics of AuNCs within HSA-AuNCs for imaging and sensing including drug binding studies.

Spectroscopic evaluation of synthesized 5β-dihydrocortisol and 5β-dihydrocortisol acetate binding mechanism with human serum albumin and their role in anticancer activity

Our study focus on the biological importance of synthesized 5β-dihydrocortisol (Dhc) and 5β-dihydrocortisol acetate (DhcA) molecules, the cytotoxic study was performed on breast cancer cell line (MCF-7) normal human embryonic kidney cell line (HEK293), the IC₅₀ values for MCF-7 cells were 28 and 25 μM, respectively, whereas no toxicity in terms of cell viability was observed with HEK293 cell line. Further experiment proved that Dhc and DhcA induced 35.6 and 37.7% early apoptotic cells and 2.5, 2.9% late apoptotic cells, respectively, morphological observation of cell death through TUNEL assay revealed that Dhc and DhcA induced apoptosis in MCF-7 cells. The complexes of HSA-Dhc and HSA-DhcA were observed as static quenching, and the binding constants (K) was 4.7 ± .03 × 10⁴ M^-1 and 3.9 ± .05 × 10⁴ M^-1_, and their binding free energies were found to be -6.4 and -6.16 kcal/mol, respectively. The displacement studies confirmed that lidocaine 1.4 ± .05 × 10⁴ M^-1 replaced Dhc, and phenylbutazone 1.5 ± .05 × 10⁴ M^-1 replaced by DhcA, which explains domain I and domain II are the binding sites for Dhc and DhcA. Further, FT-IR, synchronous spectroscopy, and CD results revealed that the secondary structure of HSA was altered in the presence of Dhc and DhcA. Furthermore, the atomic force microscopy and transmission electron microscopy showed that the dimensions like height and molecular size of the HSA-Dhc and HSA-DhcA complex were larger compared to HSA alone. Detailed analysis through molecular dynamics simulations also supported greater stability of HSA-Dhc and HSA-DhcA complexes, and root-mean-square-fluctuation interpreted the binding site of Dhc as domain IB and domain IIA for DhcA. This information is valuable for further development of steroid derivative with improved pharmacological significance as novel anti-cancer drugs.

Multi-spectroscopic and molecular modeling approaches to elucidate the binding interaction between bovine serum albumin and darunavir, a HIV protease inhibitor

Darunavir (DRV), a second-generation HIV protease inhibitor, is widely used across the world as an important component of HIV therapy. The interaction of DRV with bovine serum albumin (BSA), a major carrier protein, has been studied under simulated physiological conditions (pH7.4) by multi-spectroscopic techniques in combination with molecular modeling. Fluorescence data revealed that the intrinsic fluorescence of BSA was quenched by DRV in terms of a static quenching procedure due to the formation of the DRV-BSA complex. The results indicated the presence of single weak affinity binding site (~10³M^-1, 310K) on protein. The thermodynamic parameters, namely enthalpy change (ΔH⁰), entropy change (ΔS⁰) and Gibbs free energy change (ΔG⁰) were calculated, which signified that the binding reaction was spontaneous, the main binding forces were hydrogen bonding and van der Waals forces. Importantly, competitive binding experiments with three site probes, phenylbutazone (in sub-domain IIA, site I), ibuprofen (in sub-domain IIIA, site II) and artemether (in the interface between sub-domain IIA and IIB, site II'), suggested that DRV was preferentially bound to the hydrophobic cavity in site II' of BSA, and this finding was validated by the docking results. Additionally, synchronous fluorescence, three-dimensional fluorescence and Resonance Rayleigh Scattering (RRS) spectroscopy gave qualitative information on the conformational changes of BSA upon adding DRV, while quantitative data were obtained with Fourier transform infrared spectroscopy (FT-IR).

Elucidating the binding interaction of andrographolide with the plasma proteins: biophysical and computational approach

A phytochemical andrographolide is an anticancer agent with a stable conformation that strongly binds to the plasma proteins.

Elucidating the interaction of l-cysteine-capped selenium nanoparticles and human serum albumin: spectroscopic and thermodynamic analysis

The adsorption of HSA on the surface of Se nanoparticles.

Unravelling the binding mechanism and protein stability of human serum albumin while interacting with nefopam analogues: a biophysical and insilico approach

In this study, molecular binding affinity was investigated for Nefopam analogues (NFs), a functionalized benzoxazocine, with human serum albumin (HSA), a major transport protein in the blood. Its binding affinity and concomitant changes in its conformation, binding site and simulations were also studied. Fluorescence data revealed that the fluorescence quenching of HSA upon binding of NFs analogues is based on a static mechanism. The three analogues of NFs binding constants (K_A) are in the order of NF3 > NF2 > NF1 with values of 1.53 ± .057 × 10⁴, 2.16 ± .071 × 10⁴ and 3.6 ± .102 × 10⁵ M^-1, respectively. Concurrently, thermodynamic parameters indicate that the binding process was spontaneous, and the complexes were stabilized mostly by hydrophobic interactions, except for NF2 has one hydrogen bond stabilizes it along with hydrophobic interactions. Circular dichroism (CD) studies revealed that there is a decrease in α-helix with an increase in β-sheets and random coils signifying partial unfolding of the protein upon binding of NFs, which might be due to the formation of NFs-HSA complexes. Further, molecular docking studies showed that NF1, NF2 and NF3 bound to subdomains IIIA, IB and IIA through hydrophobic interactions. However, NF1 have additionally formed a single hydrogen bond with LYS 413. Furthermore, molecular simulations unveiled that NFs binding was in support with the structural perturbation observed in CD, which is evident from the root mean square deviation and R_g fluctuations. We hope our insights will provide ample scope for engineering new drugs based on the resemblances with NFs for enhanced efficacy with HSA.

Studies on the interaction between promethazine and human serum albumin in the presence of flavonoids by spectroscopic and molecular modeling techniques

Fluorescence, absorption, time-correlated single photon counting (TCSPC), and circular dichroism (CD) spectroscopic techniques as well as molecular modeling methods were used to study the binding characterization of promethazine (PMT) to human serum albumin (HSA) and the influence of flavonoids, rutin and baicalin, on their affinity. The results indicated that the fluorescence quenching mechanism of HSA by PMT is a static quenching due to the formation of complex. The reaction was spontaneous and mainly mediated by hydrogen bonds and hydrophobic interactions. The binding distance between the tryptophan residue of HSA and PMT is less than 8nm, which indicated that the energy transfer from the tryptophan residue of HSA to PMT occurred. The binding site of PMT on HSA was located in sites I and the presence of PMT can cause the conformational changes of HSA. There was the competitive binding to HSA between PMT and flavonoids because of the overlap of binding sites in HSA. The flavonoids could decrease the association constant and increase the binding distance. In addition, their synergistic effect can further change the conformation of HSA. The decrease in the affinities of PMT binding to HSA in the presence of flavonoids may lead to the increase of free drug in blood, which would affect the transportation or disposition of drug and evoke an adverse or toxic effect. Hence, rationalising dosage and diet regimens should be taken into account in clinical application of PMT.

Investigation of binding mechanism of novel 8-substituted coumarin derivatives with human serum albumin and α-1-glycoprotein

Coumarin molecules have biological activities possessing lipid-controlling activity, anti-hepatitis C activity, anti-diabetic, anti-Parkinson activity, and anti-cancer activity. Here, we have presented an inclusive study on the interaction of 8-substituted-7-hydroxy coumarin derivatives (Umb-1/Umb-2) with α-1-glycoprotein (AGP) and human serum albumin (HSA) which are the major carrier proteins in the human blood plasma. Binding constants obtained from fluorescence emission data were found to be KUmb-1=3.1 ± .01 × 10(4) M(-1), KUmb-2 = 7 ± .01 × 10(4) M(-1), which corresponds to -6.1 and -6.5 kcal/mol of free energy for Umb-1 and Umb-2, respectively, suggesting that these derivatives bind strongly to HSA. Also these molecules bind to AGP with binding constants of KUmb-1-AGP=3.1 ± .01 × 10(3) M(-1) and KUmb-2-AGP = 4.6 ± .01 × 10(3) M(-1). Further, the distance, r between the donor (HSA) and acceptor (Umb-1/Umb-2) was calculated based on the Forster's theory of non-radiation energy transfer and the values were observed to be 1.14 and 1.29 nm in Umb-1-HSA and Umb-2-HSA system, respectively. The protein secondary structure of HSA was partially unfolded upon binding of Umb-1 and Umb-2. Furthermore, site displacement experiments with lidocaine, phenylbutazone (IIA), and ibuprofen (IIIA) proves that Umb derivatives significantly bind to subdomain IIIA of HSA which is further supported by docking studies. Furthermore, Umb-1 binds to LYS402 with one hydrogen bond distance of 2.8 Å and Umb-2 binds to GLU354 with one hydrogen bond at a distance of 2.0 Å. Moreover, these molecules are stabilized by hydrophobic interactions and hydrogen bond between the hydroxyl groups of carbon-3 of coumarin derivatives.

Protein stability, conformational change and binding mechanism of human serum albumin upon binding of embelin and its role in disease control

Here, we present the inclusive binding mode of phytochemical embelin, an anticancer drug with human serum albumin (HSA) established under physiological condition. Also, to understand the pharmacological role of embelin molecule, here, we have studied the anti-cancer activity of embelin on human cervical cancer cell line (HeLa cell line), which revealed that embelin showed dose dependent inhibition in the growth of cancer cells and also induces 26.3% of apoptosis at an IC50 value of 29μM. Further, embelin was titrated with HSA and the fluorescence emission quenching of HSA due to the formation of the HSA-embelin complex was observed. The binding constant of this complex is 5.9±.01×10(4)M(-1) and the number of bound embelin molecules is approximately 1.0. Consequently, molecular displacement and computational docking experiments show that the embelin is binding to subdomain IB to HSA. Further evidence from microTOF-Q mass spectrometry showed an increase in mass from 66,563Da to 66,857Da observed for free HSA and HSA+embelin complex, signifying that there is robust binding of embelin with HSA. In addition, the variations of HSA secondary structural elements in presence of embelin were confirmed by circular dichroism which indicates partial unfolding of protein. Furthermore, the transmission electron micrographs established that complex formation leads to aggregation of HSA plus embelin. Molecular dynamics simulations revealed that the stability of the HSA-embelin complexes and results suggests that at around 3500ps the complex reaches equilibration state which clearly contributes to the understanding of the stability of the HSA-embelin complexes.

Modeling techniques and fluorescence imaging investigation of the interactions of an anthraquinone derivative with HSA and ctDNA

A new anthraquinone derivative (AORha) was synthesized. Its interactions with human serum albumin (HSA) and calf thymus DNA (ctDNA) were investigated by fluorescence spectroscopy, UV-visible absorption spectroscopy and molecular modeling. Cell viability assay and cell imaging experiment were performed using cervical cancer cells (HepG2 cells). The fluorescence results revealed that the quenching mechanism was static quenching. At different temperatures (290, 300, 310 K), the binding constants (K) and the number of binding sites (n) were determined, respectively. The positive ΔH and ΔS values showed that the binding of AORha with HSA was hydrophobic force, which was identical with the molecular docking result. Studying the fluorescence spectra, UV spectra and molecular modeling also verified that the binding mode of AORha and ctDNA might be intercalative. When HepG2 cells were treated with AORha, the fluorescence became brighter and turned green, which could be used for bioimaging.

A comparative binding mechanism between human serum albumin and α-1-acid glycoprotein with corilagin: biophysical and computational approach

The interaction between corilagin and serum proteins was studied by biophysical and molecular dynamics techniques which in turn provides valuable information about the interaction of phytochemical corilagin with serum proteins.

Strychnos nuxvomica, Piper longum and Mucuna pruriens seed extracts as eco-friendly corrosion inhibitors for copper in nitric acid

The inhibitive effect of the Strychnos nuxvomica (SN), Piper longum (PL) and Mucuna pruriens (MP) seeds extract on the corrosion of copper in 3 M HNO₃ solution was studied using gravimetric and electrochemical techniques.

Binding of a potential anti-hepatoma drug cis,cis,trans-[Pt(NH3)2Cl2(O2CCH2CH2COOH)-(OCONHC16H33)] with serum albumin – thermodynamic and conformational investigations

A potential anti-cancer compound with high activity was synthesized and its binding properties with human serum albumin were tested.