Interaction Of Human Serum Albumin Research Articles

HSA, free Radicals, and antibacterial interaction with ferrous oxide nanoparticles synthesized from Amorphophallus paeoniifolius

This work provides a sustainable method for producing iron oxide nanoparticles (FeONPs) using an extract from Amorphophallus paeoniifolius (AP) tubers. The nanoparticles were then thoroughly characterized by TGA/DSC, UV, FTIR, and SEM examination. They demonstrated their strong antibacterial properties against Gram-positive and Gram-negative microbes. The sizes of the ZOI were found to be 19, 25, 16 and 14 at 100 mg/mL as compared to cefoxitin as 18, 23, 8 and 12 mm for Pseudomonas aeruginosa (P. aeruginosa), Escherichia coli (E. coli), Bacillus subtilis (B. subtils) and Staphylococcus aureus (S. aureus) respectively. Their interaction with 2,2-diphenylpicrylhydrazyl (DPPH) revealed their free radical scavenging up to 70 %. NPs at 260 nm (λmax) have shown a hypo-chromic effect in the spectrophotometric approach, suggesting that FeONPs are intercalating in nature. The fluorescence quenching tests indicated the development of a non-fluorescent complex, implying FeONPs interaction with human serum albumin (HSA). As per Scatchard parameters, five binding sites observed in HSA during the interaction with FeONPs, where the Kb value indicated the NPs strong binding strength. The HSA and DPPH interaction nature of FeONPs suggests that they might be helpful in medical applications.

Protopine and Allocryptopine Interactions with Plasma Proteins

A comprehensive study of the interactions of human serum albumin (HSA) and α-1-acid glycoprotein (AAG) with two isoquinoline alkaloids, i.e., allocryptopine (ACP) and protopine (PP), was performed. The UV-Vis spectroscopy, molecular docking, competitive binding assays, and circular dichroism (CD) spectroscopy were used for the investigations. The results showed that ACP and PP form spontaneous and stable complexes with HSA and AAG, with ACP displaying a stronger affinity towards both proteins. Molecular docking studies revealed the preferential binding of ACP and PP to specific sites within HSA, with site 2 (IIIA) being identified as the favored location for both alkaloids. This was supported by competitive binding assays using markers specific to HSA’s drug binding sites. Similarly, for AAG, a decrease in fluorescence intensity upon addition of the alkaloids to AAG/quinaldine red (QR) complexes indicated the replacement of the marker by the alkaloids, with ACP showing a greater extent of replacement than PP. CD spectroscopy showed that the proteins’ structures remained largely unchanged, suggesting that the formation of complexes did not significantly perturb the overall spatial configuration of these macromolecules. These findings are crucial for advancing the knowledge on the natural product–protein interactions and the future design of isoquinoline alkaloid-based therapeutics.

Circular dichroism spectrum of (R)-(+)-3,3'-dibromo-1,1'-bi-2-naphthol in albumin: Alterations caused by complexation-Experimental and in silico investigation.

This study describes the interaction of human serum albumin (HSA) with the binol derivative (R)-(+)-3,3'-dibromo-1,1'-bi-2-naphthol (R-BrB), which has its optical activity based on the prohibitive energetic barrier for conversion into the enantiomer (S)-(+)-3,3'-dibromo-1,1'-bi-2-naphthol (S-BrB). The objective was to assess the ability of HSA to differentiate axial enantiomers based on their binding efficiency and their impact on the CD spectra. We discovered that both enantiomers were effective ligands, and the CD signal disappeared when equimolar amounts of R-BrB and S-BrB were simultaneously added, indicating no preference for either enantiomer. The complexation resulted in a significant signal increase at 250 nm and a bathochromic effect at 370 nm. Molecular docking simulations were performed, and the lower energy pose of R-BrB was selected for DFT calculations. The theoretical CD spectra of free and complexed R-BrB were obtained and showed alterations corroborating the experimental results. By comparing the difference spectrum (HSA:R-BrB minus HSA) with the spectrum of free RBrB in water or ethyl alcohol, we concluded that the CD signal intensification was due to the increased solubilization of R-BrB upon binding to HSA.

Protein-Mediated Changes in Membrane Fluidity and Ordering: Insights into the Molecular Mechanism and Implications for Cellular Function.

Probing protein-membrane interactions is vital for understanding biological functionality for various applications such as drug development, targeted drug delivery, and creation of functional biomaterials for medical and industrial purposes. In this study, we have investigated interaction of Human Serum Albumin (HSA) with two different lipids, dipalmitoylphosphatidylglycerol (dDPPG) and dipalmitoylphosphatidylcholine (dDPPC), using Vibrational Sum Frequency Generation spectroscopy at different membrane fluidity values. In the liquid-expanded (LE) state of the lipid, HSA (at pH 3.5) deeply intercalated lipid chains through a combination of electrostatic and hydrophobic interactions, which resulted in more ordering of the lipid chains. However, in the liquid-condensed (LC) state, protein intercalation is decreased due to tighter lipid packing. Moreover, our findings revealed distinct differences in HSA's interaction with dDPPG and dDPPC lipids. The interaction with dDPPC remained relatively weak compared to dDPPG. These results shed light on the significance of protein mediated changes in lipid characteristics, which hold considerable implications for understanding membrane protein behavior, lipid-mediated cellular processes, and lipid-based biomaterial design.

Insight into the interaction of 5,6 epoxy-cholesterols with human serum albumin

5,6-Epoxy-cholesterols has been recently revealed to control metabolic pathway in breast cancer, which makes investigating their binding interaction with human serum albumin (HSA) an attractive field of research. The main aim of this article is to examine the binding interaction of 5,6 α-epoxy-cholesterol (5,6 α EC) and 5,6 β-epoxy-cholesterol (5,6 β- EC) with HSA using different spectroscopic methods and molecular modeling. These compounds interact with HSA via hydrophobic interactions and hydrogen bonds with binding constants 6.3 × 105 M−1 for 5,6 α-epoxy-cholesterol and 6.9 × 105 M−1 for 5,6 β-epoxy-cholesterol besides, the mechanism of the interaction can be attributed to static quenching. Circular dichroism data indicated that the α-helical content of HSA increased from 50.5 to 59.8 and 61.1 % after the addition of 5,6 α-ECs and 5,6 β-EC, respectively, with a ratio of 1:2. Thermodynamic analysis revealed that binding between 5,6-epoxy-cholesterols and HSA is spontaneous and entropy-driven. The molecular docking and esterase-like activity experiments were performed to envision a link between the experimental and theoretical results. The optimal binding site of 5,6-epoxy-cholesterols with HSA was located in subdomain IIA. Moreover, theoretical calculations were performed using the B3LYP function with the 6-311++G (d,p) basis set, indicating the HOMO-LUMO energy gap of 7.874 eV for 5,6 α-epoxy-cholesterol and 7.873 eV for 5,6 β-epoxy-cholesterol. The obtained findings are assumed to provide basic data for understanding the binding interactions of HSA with oxysterol compounds, which could help explore the pharmacokinetics and pharmacodynamics of oxysterol compounds.

Effects of ultraviolet radiation and reactive oxygen species on the structure and ligand-binding ability of human serum albumin for norfloxacin

To explore the influence of ultraviolet radiation (UV) and reactive oxygen species (ROS) on the structure and ligand-binding ability of human serum albumin (HSA) for norfloxacin (NFLX), HSA was treated with UV (HSAUV) and UV/H2O2 (HSAUV/H2O2), respectively. The structure difference of HSA, HSAUV and HSAUV/H2O2 were investigated by Fourier transform infrared, fluorescence (i.e., emission fluorescence, synchronous fluorescence and fluorescence lifetime) and circular dichroism spectroscopy. The intermolecular interactions of HSA, HSAUV and HSAUV/H2O2 with NFLX were studied at pH 7.4 and temperatures 291, 310, and 318 K, using fluorescence emission and synchronous fluorescence spectroscopy, and combined with molecular docking. The results suggested that UV and ROS could destroy the α-helix of HSA and induce the loose of HSA structure, and the average fluorescence lifetimes of HSA decreased from 6.12 ns to 3.76 ns (HSAUV) and 3.40 ns (HSAUV/H2O2). The conformational changes of HSA caused by UV and ROS allowed NFLX to get access to more potential binding sites and promoted the binding affinity of HSA for NFLX, while the temperature stability of the HSA-NFLX complex significantly decreased. The results are useful and valuable for evaluating the protein damage caused by UV and ROS in organisms.

A comprehensive investigation of the interactions of human serum albumin with polymeric and hybrid nanoparticles.

Nanoparticles (NPs) engineered as drug delivery systems continue to make breakthroughs as they offer numerous advantages over free therapeutics. However, the poor understanding of the interplay between the NPs and biomolecules, especially blood proteins, obstructs NP translation to clinics. Nano-bio interactions determine the NPs' in vivo fate, efficacy and immunotoxicity, potentially altering protein function. To fulfill the growing need to investigate nano-bio interactions, this study provides a systematic understanding of two key aspects: (i) protein corona (PC) formation and (ii) NP-induced modifications on protein's structure and stability. A methodology was developed by combining orthogonal techniques to analyze both quantitative and qualitative aspects of nano-bio interactions, using human serum albumin (HSA) as a model protein. Protein quantification via liquid chromatography-mass spectrometry, and capillary zone electrophoresis (CZE) clarified adsorbed protein quantity and stability. CZE further unveiled qualitative insights into HSA forms (native, glycated HSA and cysteinylated), while synchrotron radiation circular dichroism enabled analyzing HSA's secondary structure and thermal stability. Comparative investigations of NP cores (organic vs. hybrid), and shells (with or without polyethylene glycol (PEG)) revealed pivotal factors influencing nano-bio interactions. Polymeric NPs based on poly(lactic-co-glycolic acid) (PLGA) and hybrid NPs based on metal-organic frameworks (nanoMOFs) presented distinct HSA adsorption profiles. PLGA NPs had protein-repelling properties while inducing structural modifications on HSA. In contrast, HSA exhibited a high affinity for nanoMOFs forming a PC altering thereby the protein structure. A shielding effect was gained through PEGylation for both types of NPs, avoiding the PC formation as well as the alteration of unbound HSA structure.

Analysis on the interaction of coumarin isomers with human serum albumin in the presence of cisplatin

Many drugs combined with human serum albumin (HSA) are commonly used for medical treatment. Various drugs can bind to HSA through hydrogen bonding and hydrophobic action, changing the binding affinity and binding mode between drugs and HSA and avoiding rapid drug metabolism. Through multispectral analysis and molecular docking simulation, the interaction between HSA and two coumarin isomers (pimpinellin and isopimpinellin) was analyzed and studied. Fluorescence quenching explained that regardless of cisplatin (cDDP), the amino acid residues of HSA could interact with pimpinellin and isopimpinellin. This interaction changed the inherent fluorescence intensity of HSA and formed the ground-state complexes through hydrogen bonding and hydrophobic interaction whether cDDP was present or not. Pimpinellin and isopimpinellin mainly bound to site I of the IIA subdomain in HSA, which could cause changes in the micro-environment surrounding amino acid residues. In addition, cDDP increased the conformational change during the interaction of HSA and pimpinellin/isopimpinellin. This work compared the interactive binding properties of pimpinellin/isopimpinellin with HSA in the presence of cDDP, which paved the way for the perfection of HSA as a drug delivery system in vivo.

Unveiling the molecular association of novel benzohydrazide-substituted Schiff base complexes with human serum albumin

So far, various Schiff base zinc (II) complexes with potential applications in biomedicine have been reported as medicinal agents in diagnosis, imaging and treatment of diseases such as cancer and Alzheimer. Therefore, it is important to understand their interaction with carrier proteins, such as human serum albumin (HSA). The present paper focuses on synthesis, characterization and the binding interactions between HSA and two novel Schiff-base complexes, [Zn(SL)(N-N)](NO3)2 (SL = Schiff base ligand; N-N = 2,2′-bipyridine (bpy, C1), 1,10-phenanthroline (phen, C2)), using experimental and molecular docking techniques. The antioxidant performance of compounds increased as follows: C2 > C1 > SL. Two complexes quenched the protein fluorescence emission by the same mechanism (static quenching). The binding constant values obtained from the interaction of HSA and complexes were in the ideal range for biological applications (Kb = 0.07 × 104 M−1 for C1, 5.01 × 104 M−1 for C2 at 303 K). The binding of the C1/C2 somewhat reduced the stability of the protein structure and led to a change in polarity around tyrosine and tryptophan. In this research, we found that the increase of the planar aromatic part in the metallodrug can affect the strength of the interaction, the type of force involved during the interaction process, and the medicinal properties such as their antioxidant capabilities.

Elucidating the influence of some metal ions on the binding of antimalarial drugs to human serum albumin: spectroscopic approach

Influence of six metal ions viz. Mg2+, K+, Ca2+, Mn2+, Cu2+ and Ba2+ on the binding affinity of human serum albumin (HSA) towards three antimalarial drugs, namely, sulfadoxine (SDN), mefloquine (MEF) and lumefantrine (LUM) was investigated using fluorescence quenching titrations. The effects of metal ions (Mn2+, Cu2+ and Ba2+) were similar on the affinity of HSA towards SDN, MEF and LUM. Values of the association constant, Ka, for SDN/MEF/LUM ̶ HSA interactions in the presence of these metal ions, decreased significantly in the order: Mn2+ > Cu2+ > Ba2+. On the other hand, the presence of Mg2+, K+, and Ca2+ affected the binding affinity for these drugs differently. Whereas a slight increase in the Ka value of the SDN ̶ HSA complex was seen in the presence of Mg2+, Ca2+ produced a similar effect on the LUM ̶ HSA system. For MEF ̶ HSA and LUM ̶ HSA systems, effects of K+ and Mg2+ were similar, showing a decrease in the Ka value, being more effective with K+; however, this decrease was more significant than Mn2+, Cu2+ and Ba2+. Values of ‘n’ remained approximately equal to 1, hinting at a single binding site for each drug.

Elucidation of the intermolecular interactions of human serum albumin with pyrene and its derivatives: The effects of substituents

The intermolecular interactions between pyrene (Pyr) or its derivatives with different types of substituents (i.e., 1-hydroxypyrene (HPyr), 1-nitropyrene (NPyr), 1-aminopyrene (APyr), and 1-methylpyrene (MPyr)) and human serum albumin (HSA) were explored by multispectroscopy combined with molecular docking. Fluorescence spectral analysis showed that Pyr and its derivatives quenched the fluorescence of HSA mainly through the static mechanism and could form 1:1 complexes with HSA in the growing affinity order of Pyr (0.26 × 105 L mol−1), APyr (0.33 × 105 L mol−1), HPyr (1.23 × 105 L mol−1), NPyr (2.53 × 105 L mol−1) and MPyr (12.49 × 105 L mol−1) at 298 K. Molecular docking indicated that hydrophobic and π-stacking interactions were formed between Pyr/HPyr/NPyr/APyr/MPyr and its surrounding amino acid residues in the IB subdomain of HSA, while hydrogen bonds only existed in HSA‒HPyr and HSA‒APyr systems. As the concentration of HPyr/NPyr/APyr/MPyr increased, the proportion of α-helical structures in HSA increased initially and then decreased. The α-helical component of HSA, however, kept rising with the growing concentration of Pyr. Based on the results of synchronous fluorescence spectra, these conformational changes of HSA did not disturb the microenvironment around tryptophan and tyrosine residues. This work is helpful for improving our understanding of the significance of the types of substituents on polycyclic aromatic hydrocarbon‒HSA interactions.

Human serum albumin as a potential drug delivery system for N-methylated hot spot insulin analogs inhibiting hormone aggregation

The purpose of this study was to investigate whether Human Serum Albumin (HSA) can bind N-methylated analogs of hot spots of native insulin. Three N-methylated derivatives of the A13–A19 fragment of native insulin were used: L(N-Me)YQLENY (1), LYQ(N-Me)LENY (2), and L(N-Me)YQ(N-Me)LENY (3). The studied N-methylated insulin fragments possess inhibiting potential against hormone aggregation. A variety of research techniques, including spectroscopic methods and microscopy assays, were used to study the interaction of HSA with the N-methylated insulin fragments. Based on spectroscopic measurements with Congo Red and Thioflavin T, all the analyzed N-methylated peptides were able to interact with the HSA surface. The CD spectrum registered for HSA in the presence of L(N-Me)YQLENY showed the smallest content of α-helix conformation, indicating the most compact HSA structure. Based on the results of MST, the dissociation constants (Kd) for complexes of HSA and peptides 1–3 were 19.2 nM (complex 1), 15.6 nM (complex 2), and 8.07 nM (complex 3). Microscopy assays, dynamic light scattering measurements as well as computer simulation of protein–ligand interaction also confirmed the possibility of docking the N-methylated inhibitors within HSA.

Inhibition of toxic metal-alpha synuclein interactions by human serum albumin.

Human serum albumin (HSA), the most abundant protein in plasma and cerebrospinal fluid, not only serves as a crucial carrier of various exogenous and endogenous ligands but also modulates the aggregation of amyloidogenic proteins, including alpha synuclein (αSyn), which is associated with Parkinson's disease and other α-synucleinopathies. HSA decreases αSyn toxicity through the direct binding to monomeric and oligomeric αSyn species. However, it is possible that HSA also sequesters metal ions that otherwise promote aggregation. Cu(ii) ions, for example, enhance αSyn fibrillization in vitro, while also leading to neurotoxicity by generating reactive oxygen species (ROS). However, it is currently unclear if and how HSA affects Cu(ii)-binding to αSyn. Using an integrated set of NMR experiments, we show that HSA is able to chelate Cu(ii) ions from αSyn more efficiently than standard chelators such as EDTA, revealing an unexpected cooperativity between the HSA metal-binding sites. Notably, fatty acid binding to HSA perturbs this cooperativity, thus interfering with the sequestration of Cu(ii) ions from αSyn. We also observed that glycation of HSA diminished Cu(ii)-binding affinity, while largely preserving the degree of cooperativity between the HSA metal-binding sites. Additionally, our results show that Cu(ii)-binding to HSA stabilizes the interactions of HSA with αSyn primarily at two different regions, i.e. the N-terminus, Tyr 39 and the majority of the C-terminus. Our study not only unveils the effect of fatty acid binding and age-related posttranslational modifications, such as glycation, on the neuroprotective mechanisms of HSA, but also highlights the potential of αSyn as a viable NMR-based sensor to investigate HSA-metal interactions.

Spectroscopy and molecular simulation on the interaction of Nano-Kaempferol prepared by oil-in-water with two carrier proteins: An investigation of protein–protein interaction

In this work, the interaction of human serum albumin (HSA) and human holo-transferrin (HTF) with the prepared Nano-Kaempferol (Nano-KMP) through oil-in-water procedure was investigated in the form of binary and ternary systems by the utilization of different spectroscopy techniques along with molecular simulation and cancer cell experiments. According to fluorescence spectroscopy outcomes, Nano-KMP is capable of quenching both proteins as binary systems by a static mechanism, while in the form of (HSA-HTF) Nano-KMP as the ternary system, an unlinear Stern–Volmer plot was elucidated with the occurrence of both dynamic and static fluorescence quenching mechanisms in the binding interaction. In addition, the two acquired Ksv values in the ternary system signified the existence of two sets of binding sites with two different interaction behaviors. The binding constant values of HSA-Nano KMP, HTF-Nano-KMP, and (HSA-HTF) Nano-KMP complexes formation were (2.54 ± 0.03) × 104, (2.15 ± 0.02) × 104 and (1.43 ± 0.04) × 104M−1at the first set of binding sites and (4.68 ± 0.05) × 104 M−1 at the second set of binding sites, respectively. The data of thermodynamic parameters confirmed the major roles of hydrogen binding and van der Waals forces in the formation of HSA-Nano KMP and HTF-Nano KMP complexes. The thermodynamic parameter values of (HSA-HTF) Nano KMP revealed the dominance of hydrogen binding and van der Waals forces in the first set of binding sites and hydrophobic forces for the second set of binding sites. Resonance light scattering (RLS) analysis displayed the existence of a different interaction behavior for HSA-HTF complex in the presence of Nano-KMP as the ternary system. Moreover, circular dichroism (CD) technique affirmed the conformational changes of the secondary structure of proteins as binary and ternary systems. Molecular docking and molecular dynamics simulations (for 100 ns) were performed to investigate the mechanism of KMP binding to HSA, HTF, and HSA-HTF. Next to observing a concentration and time-dependent cytotoxicity, the down regulation of PI3K/AkT/mTOR pathway resulted in cell cycle arrest in SW480 cells.

Complexes and supramolecular associates of dodecyl-containing oligonucleotides with serum albumin

Serum albumin is currently in the focus of biomedical research as a promising platform for the creation of multicomponent self-assembling systems due to the presence of several sites with a high binding affinity of various compounds in its molecule, including lipophilic oligonucleotide conjugates. In this work, we investigated the stoichiometry of the dodecyl-containing oligonucleotides binding to bovine and human serum albumins via electrophoretic mobility shift assay. The results testify to the formation of albumin-oligonucleotide complexes with a stoichiometry of about 1 : (1.25 ± 0.25) under physiological-like conditions. Using atomic force microscopy, it was found that interaction of human serum albumin with a duplex of complementary dodecyl-containing oligonucleotides resulted in associates of round shape with a diameter of 165.5 ± 94.3 nm and 28.9 ± 16.9 nm in height, and with polydeoxyadenylic acid and dodecyl-containing oligothymidylate also resulted in formation of supramolecular associates with a size of about 315.4 ± 70.9 and 188.3 ± 43.7 nm. The obtained data allow considering dodecyl-containing oligonucleotides and albumin as potential components for the development of methods to design self-assembled systems for solving problems of molecular biology, biomedicine, and the development of unique theranostics with targeted action.

Investigating haloacetic acids - human serum albumin interactions: A comprehensive approach using multi-spectroscopy, DFT calculations, and molecular docking

Haloacetic acid (HAAs) has been shown in studies to be teratogenic and mutagenic. The toxicity of HAAs to macromolecules and their mechanism of action are still unclear. To further explore the potential impact of HAAs on organisms, this study used multi-spectroscopy, density functional theory (DFT), and molecular docking to analyze the characteristics and mechanisms of five typical HAAs interactions with HSA.Multispectral analysis indicates that the binding energies of the interactions between the five HAAs and HSA are weaker than other HSA-ligand complex systems. The order of binding constants at 298 K was as follows: DBAA (458.14 L mol−1) > TCAA (374.71 L mol−1) > DCAA (242.89 L mol−1) > MBAA (140.73 L mol−1) > MCAA (102.05 L mol−1). The quenching processes of the interactions between the five HAAs and HSA belong to static quenching, an exothermic reaction process. Hydrogen bonds and van der Waals forces are the main driving forces in the formation process of the HSA-HAAs complex.Molecular docking results indicate that TCAA, DBAA, and DCAA are more likely to bind with HSA. Correlation analysis based on DFT calculations reveals the intrinsic relationship between the chemical structural features of HAAs and the binding performance of HSA-HAAs. For the first time, the research discovered that among the quantum chemical descriptors, the highest ALIE maximum, the highest ESP maximum, and the maximum local electrophilic index f−(r) all correlate well with the HSA-HAAs binding constants. Their correlation coefficients are 0.83, 0.94, and -0.56, respectively, which can effectively predict the binding performance of HAAs with HSA.In-vitro toxicity experiments on LO2 cells show that within the concentration range of 0.002–10 mmol·L−1, MBAA, MCAA, and DBAA exhibit higher toxicity to normal human liver cells. In contrast, DCAA and TCAA show low or no toxicity.Through comprehensive research combining experimental and theoretical analysis, the mechanism of HSA-HAAs has been deeply revealed. This holds significant scientific value for assessing the environmental risks of HAAs and understanding their impact on biological activities.

Molecular docking approach on the binding stability of derivatives of phenolic acids (DPAs) with Human Serum Albumin (HSA): Hydrogen-bonding versus hydrophobic interactions or combined influences?

Molecular docking (Mol.Doc) techniques were employed to ascertain the binding affinity and energetics of hydroxy derivatives of benzoic and cinnamic acids extract from Psidium guajava L. with Human Serum Albumin (HSA). Caffeic acid (CA), Ferullic acid (FA), Sinapic acid (SA), Syringic acid (SyA) and Vanillic acid (VA) are the derivatives phenolic acids (DPA) employed in docking studies which acts as the guest molecule. Docking of various feasible conformers of DPA with HSA (host) was explored and these conformers were categorized based on the docking score which is correlated to the binding energy (BE) and the stability depends upon the molecular interactions. Among the phenolic acids, SA-HSA complex was energetically more favorable and feasible based on BE and the order of binding stability upon complex formation of various DPA-HSA follows the order SA > FA = CA > VA > SyA, though SA and SyA are structurally similar to each other, likewise FA and VA exhibit a similar structure. The stability upon complex formation is correlated to the docking of the guest molecule in the binding domains of HSA and several molecular interactions. Hydrogen-bonding (HB) interaction governs the stability of host-guest complex is established. Interestingly, the presence of multiple hydrophobic interactions (pi-pi, pi-alkyl, pi-cation or anion, pi-sigma and pi-amide) competes over HB interaction in several conformers resulting in a decrease in BE. We report that SA acts as an excellent site selective and site-specific ligand that prefers to dock in Sudlow binding site II comprising of sub domains IIIA and IIIB respectively. However, all other phenolic acids do not behave neither as site selective nor site specific ligand such that they prefer to reside both in site II and site III (non-Sudlow binding site) of HSA. We authenticate that all the DPA as well as the amino acid moieties in HSA act as HB donor as well as acceptor sites apart from several hydrophobic interactions. We further establish that all the DPA has the least probable affinity to reside in binding site I (warfarin binding site), whereas sub domain IIIA of site II is the most preferred site which is energetically most favoured among all the sub domains.

In Vitro Study of the Interaction between Ochratoxin A and Human Serum Albumin by Spectroscopic and Molecular Docking Methods

AbstractOchratoxin A (OA) is a mycotoxin that has a potential risk to human health due to its nephrotoxic, immunotoxic and carcinogenic effects. For these reasons the interaction of ochratoxin A with human serum albumin (HSA) was investigated in physiological media by various techniques such as UV‐Vis, fluorescence (FL), circular dichroism (CD), attenuated total reflection (ATR), differential scanning calorimetry (DSC), atomic force microscopy (AFM) and molecular docking study via Auto Dock‐vina software. The fluorescence intensity of tryptophan in HSA was strongly quenched in the present of OA and the quenching constants and binding constant were valued 108 M−1 and 1.04 M−1, respectively. The CD spectra showed alteration in the secondary structure of HSA in the presence of ochratoxin by reducing the regular alpha helical structure and increasing the beta‐sheet structure. By increasing the concentration of OA to 1.25 μM, the intensity of absorption spectrum at 282 nm was increased, indicating the strong interaction of OA and HSA. The enthalpies of these molecular interaction calculated from DSC analysis indicate OA interaction with HAS is exothermic. The docking calculations showed that the amino acids of Lys190, ASP187, LYS519, ARG186 and ARG428 were interacted with OA by hydrogen bonding.

High affinity of protocatechuic acid to human serum albumin and modulatory effects against oxidative stress and inflammation in alveolar epithelial cells: Modulation of pulmonary fibrosis

Protocatechuic acid (PCA), C7H6O4, has been shown to possess potential antioxidant properties. But its interaction with the main plasma carrier protein, human serum albumin (HSA), as well as its antioxidant mechanism remains largely unknown. It has been shown that induced pulmonary fibrosis can be modulated through mitigating epithelial apoptosis mediated by the prohibition of oxidative stress. Therefore, in this study, the interaction of PCA and HSA was explored by spectroscopy, calorimetry (DSC), as well as molecular docking studies. Also, the protective effects of PCA against lipopolysaccharide (LPS)-induced cytotoxicity and oxidative stress were evaluated by MTT, ROS, ELISA, real-time PCR, and western blot assays. It was shown that under the interaction of HSA with PCA a spontaneous interaction occurs with the contribution of hydrophobic forces, which results in the formation of a stable complex. Cellular assays showed that PCA reduced LPS-induced cytotoxicity in human type II alveolar epithelial cells (AECs) through mitigation of ROS production, release and gene expression of TNf-α and IL-1β as pro-inflammatory mediators, and caspase-3 gene and protein as an apoptotic factor. Also, it was shown that PCA can reduce the expression of NF-κB at the protein level, indicating a possible inhibition of pulmonary fibrosis via regulating the NF-κB signaling pathway. In conclusion, PCA could be a promising therapeutic agent for the control of oxidative stress in AECs which is an important factor in redox modulatory therapy, while its pharmacodynamics can be modulated by interaction with HSA.

Complexes and Supramolecular Associates of Dodecyl-Containing Oligonucleotides with Serum Albumin.

Serum albumin is currently in the focus of biomedical research as a promising platform for the creation of multicomponent self-assembling systems due to the presence of several sites with high binding affinity of various compounds in its molecule, including lipophilic oligonucleotide conjugates. In this work, we investigated the stoichiometry of the dodecyl-containing oligonucleotides binding to bovine and human serum albumins using an electrophoretic mobility shift assay. The results indicate the formation of the albumin-oligonucleotide complexes with a stoichiometry of about 1 : (1.25 ± 0.25) under physiological-like conditions. Using atomic force microscopy, it was found that the interaction of human serum albumin with the duplex of complementary dodecyl-containing oligonucleotides resulted in the formation of circular associates with a diameter of 165.5 ± 94.3 nm and 28.9 ± 16.9 nm in height, and interaction with polydeoxyadenylic acid and dodecyl-containing oligothymidylate resulted in formation of supramolecular associates with the size of about 315.4 ± 70.9 and 188.3 ± 43.7 nm, respectively. The obtained data allow considering the dodecyl-containing oligonucleotides and albumin as potential components of the designed self-assembling systems for solving problems of molecular biology, biomedicine, and development of unique theranostics with targeted action.