Interaction Of Human Serum Albumin Research Articles

Exploring the combination characteristics of lumefantrine, an antimalarial drug and human serum albumin through spectroscopic and molecular docking studies

Binding of lumefantrine (LUM), an antimalarial drug to human serum albumin (HSA), the main carrier protein in human blood circulation was investigated using fluorescence quenching titration, UV–vis absorption and circular dichroism (CD) spectroscopy as well as molecular docking. LUM-induced quenching of the protein (HSA) fluorescence was characterized as static quenching, as revealed by the decrease in the value of the Stern-Volmer quenching constant, Ksv with increasing temperature, thus suggesting LUM-HSA complex formation. This was also confirmed from the UV–vis absorption spectral results. Values of the association constant, Ka for LUM–HSA interaction were found to be within the range, 7.27–5.01 × 104 M−1 at three different temperatures, i.e. 288 K, 298 K and 308 K, which indicated moderate binding affinity between LUM and HSA. The LUM–HSA complex was stabilized by hydrophobic interactions, H-bonds, as well as van der Waals forces, as predicted from the thermodynamic data (ΔS = +50.34 J mol−1 K−1 and ΔH = −12.3 kJ mol−1) of the binding reaction. Far-UV and near-UV CD spectral results demonstrated smaller changes in both secondary and tertiary structures of HSA upon LUM binding, while three-dimensional fluorescence spectra suggested alterations in the microenvironment around protein fluorophores (Trp and Tyr). LUM binding to HSA offered stability to the protein against thermal stress. Competitive drug displacement results designated Sudlow’s Site I, located in subdomain IIA of HSA as the preferred binding site of LUM on HSA, which was well supported by molecular docking analysis.Communicated by Ramaswamy H. Sarma

Pearl-necklace assembly of human serum albumin with the poly(acrylic acid) polyelectrolyte investigated using small angle X-ray scattering (SAXS).

In this comprehensive study, the interaction of human serum albumin (HSA) with poly(acrylic acid) (PAA) was explored using small angle X-ray scattering (SAXS) combined with chromatography. The results revealed the formation of a complex between HSA macromolecules and PAA chains but solely under some specific conditions of the ionic strength and pH of the medium. In fact, this binding was found to take place only at pH close to 5 and at low ionic strength (0.15 M). Otherwise, for a higher pH and a salt concentration of 0.75 M the HSA-PAA complex tends to dissociate completely showing the reversibility of the complexation. The assessment of the influence of the HSA/PAA molar ratio on the radius of gyration of the complex suggests that 4 HSA molecules could bind to each 100 kDa PAA chain. In addition, the Porod volume evaluation for the same range of the HSA/PAA ratio confirms this assumption. Finally, an all-atom SAXS modelling study using the BUNCH program was conducted to find a compatible model that fits the HSA-PAA complex scattering data. This model allows us to portray the HSA/PAA complex as a pearl-necklace assembly with 4 HSA molecules on the 100 kDa PAA chain.

The Difference of Serum Protein Transport between Echinosides and Verbascoside

Verbascoside (VER) is the enzymatic hydrolysis product of echinacoside (ECH). The molecular structures of ECH and VER have different glucosyl groups so they bind to serum albumin in different ways, resulting in different pharmacological actions. In this report, we have examined the binding characteristics between human serum albumin (HSA) and ECH/VER by molecular modeling and spectroscopic approaches. Molecular modeling revealed that VER bound to HSA mainly through hydrogen bonds, van der Waals forces and hydrophobic forces. The spectroscopic results showed that the interactions between HSA and VER/ECH involved a static binding process, and the bonding strength of the VER-HSA complex was stronger than that of the ECH-HSA complex. The value of the binding distances (r) was low, which indicated the occurrence of energy transfer. The reaction conformational pattern of HSA-VER and HSA-ECH gave a “two-state model” based on fluorescent phase diagram analysis. According to the thermodynamic model, the main forces between interaction of VER and HSA were hydrogen bonds and van der Waals forces, whereas the interaction between ECH and HSA was hydrophobic force. The fluorescence polarization analysis demonstrated that the interaction between HSA and VER or ECH generated a non-covalent complex. Compared with ECH, VER was more likely to bind with HSA because of its smaller molecular size and low polarity. The results of the spectral analysis concurred with the molecular modeling data, which provides a helpful reference for the study of the molecular reaction mechanism of VER/ECH binding to HSA.

The Difference of Serum Protein Transport between Echinosides and Verbascoside

Verbascoside (VER) is the enzymatic hydrolysis product of echinacoside (ECH). The molecular structures of ECH and VER have different glucosyl groups so they bind to serum albumin in different ways, resulting in different pharmacological actions. In this report, we have examined the binding characteristics between human serum albumin (HSA) and ECH/VER by molecular modeling and spectroscopic approaches. Molecular modeling revealed that VER bound to HSA mainly through hydrogen bonds, van der Waals forces and hydrophobic forces. The spectroscopic results showed that the interactions between HSA and VER/ECH involved a static binding process, and the bonding strength of the VER-HSA complex was stronger than that of the ECH-HSA complex. The value of the binding distances (r) was low, which indicated the occurrence of energy transfer. The reaction conformational pattern of HSA-VER and HSA-ECH gave a “two-state model” based on fluorescent phase diagram analysis. According to the thermodynamic model, the main forces between interaction of VER and HSA were hydrogen bonds and van der Waals forces, whereas the interaction between ECH and HSA was hydrophobic force. The fluorescence polarization analysis demonstrated that the interaction between HSA and VER or ECH generated a non-covalent complex. Compared with ECH, VER was more likely to bind with HSA because of its smaller molecular size and low polarity. The results of the spectral analysis concurred with the molecular modeling data, which provides a helpful reference for the study of the molecular reaction mechanism of VER/ECH binding to HSA.

Hydrophobic association of sodium cholate with human serum albumin evades protein denaturation induced by urea

Human Serum Albumin (HSA) is a prominent protein in plasma. Protein binds with different types of ligands such as fatty acids, drugs and surfactants. Interaction of serum albumin and bile salts is studied, due to its important application in drug delivery and biopharmaceuticals. The bile salts are amphibilic molecules, synthesized by liver and undergo aggregation in aqueous media. In the present work, sodium cholate (NaC) is used as model bile salt. The interaction of NaC and HSA is monitored using intrinsic Trp-214 fluorescence. Urea (U) ([U] = 0–9.6 M) is added to the pre-formed HSA-NaC system to study.The association of NaC with Trp 214, which is buried within the hydrophobic core of sub domain IIA (Sudlow site I) of HSA, shows a prominent nature of maintaining the protein in the native conformation and hence there is very minimal change in photophysical properties of HSA-NaC system. The denaturation study carried out on HSA-NaC system by using chemical denaturant urea, shows very minimal change in the photophysical property of Trp 214, up to a 6 M concentration of U. Whereas, from 7.2 to 9.6 M [U] the fluorescence intensity show a decrease along with a 3 nm red shift.

Study of HSA interactions with arachidonic acid using spectroscopic methods revealing molecular dynamics of HSA-AA interactions.

The interaction between human serum albumin (HSA) and arachidonic acid (AA) as an unsaturated fatty acid were investigated in the present study using methods including UV-VIS spectrophotometry, fluorescence and circular dichroism (CD) spectroscopy, lifetime measurements, fluorescence anisotropy measurements and visual molecular dynamics (MD). The thermodynamic parameters were assessed from HSA thermal and chemical denaturation in the presence and absence of AA. From the thermal denaturation, the Tm and ΔG˚(298K) magnitudes obtained were 327.7 K and 88 kJ/mol, respectively, for HSA alone, and 323.4 K and 85 kJ/mol, respectively, following treatment with a 10 µM AA concentration. The same manner of reduction in Gibbs free energy as a criterion of protein stability was achieved during chemical denaturation by urea in the presence of AA. The present study investigates HSA binding nature through MD approaches, and the results indicated that the binding affinity of AA to the subdomain IIA of HSA is greater compared with that of subdomain IIIA. Although the HSA regular secondary structure evaluation by CD exhibited a minor change following incubation with AA, its tertiary structure revealed an observable fluctuation. Thus, it appears that the interaction between AA and HSA requires minor instability and partial structural changes.

Probing the Binding of Valacyclovir Hydrochloride to the Human Serum Albumin

UV-visible and Fluorescence spectroscopic methods were employed to study the interaction of human serum albumin (HSA) with Valacyclovir Hydrochloride. Additionally, molecular dynamics and molecular docking simulations were used to visualize and specify the binding site of Valacyclovir Hydrochloride. The Stern-Volmer and van't Hoff equations along with spectroscopic observations, were used to determine the binding and thermodynamic parameters. Overall obtained results revealed the presence of dynamic type of quenching mechanism in binding of Valacyclovir Hydrochloride to HSA, while the interaction was found to be entropy driven at domain III of HSA. Analyzing the protein ligand interactions with LIGPLOT, confirmed the dominance of hydrophobic interactions, while the hydrogen bonding interactions play the minor role.

Cycloplatinated(II) Derivatives of Mercaptopurine Capable of Binding Interactions with HSA/DNA.

In this study, two new bis-cyclometalated Pt(II) complexes, [Pt(C^N)(S^N)] [S^N = deprotonated 6-mercaptopurine (6-MP) and C^N = deprotonated 2-phenylpyridine (ppy), 2a; C^N = deprotonated benzo[h]quinoline (bhq), 2b], are synthesized by the reaction of [PtR(SMe2)(C^N)] (R = Me or p-MeC6H4) with 1 equiv of 6-mercaptopurine (6-HMP) at room temperature. The complexes are fully characterized using 1H and 13C NMR spectroscopies, electrospray ionization mass spectrometry, and elemental analysis. Biomolecular interaction of complex 2a with human serum albumin (HSA) is studied by fluorescence, UV-vis, and circular dichroism (CD) spectroscopies. The binding constants (Kb) and number of binding sites (n) are evaluated using the Stern-Volmer equation. The intrinsic fluorescence of protein is quenched by a static quenching mechanism, with a binding constant of Kb ∼ 105 reflecting a high affinity of complex 2a for HSA. The thermodynamic parameters (ΔH°, ΔG°, and ΔS°) indicate that the interaction is a spontaneous process and hydrophobic forces play a main role in the reaction. The displacement experiments demonstrate that the reactive binding sites of HSA to complex 2a are mainly located within its hydrophobic cavity in subdomain IIA (site I). Synchronous fluorescence spectra reveal that complex 2a affected the microenvironment of tryptophan-214 residues in subdomain IIA of HSA. In the case of interaction of complex 2b and HSA, because of overlapping of the emission spectra of complex 2b with HSA, chemometric approaches are applied. The results indicate significant interaction between the tryptophan residue of HSA and complex 2b. Moreover, the binding of Pt(II) complexes 2a and 2b causes a reduction of the α-helix content of HSA, as obtained by far-UV CD spectroscopy. The average binding distance (r) between Pt(II) complexes and HSA is obtained by Förster's resonance energy-transfer theory. Also, a molecular docking simulation reveals that π-π-stacking and hydrophobic interactions between these complexes and HSA are significant. Furthermore, the interactions of platinum complexes, 2, with calf-thymus DNA (CT-DNA) are investigated. The UV-vis results and ethidium bromide competitive studies support an intercalative interaction of both Pt(II) complexes with DNA. The new complexes 2 are also screened for anticancer activities. The results show that complexes 2 exhibit significant anticancer activity against the K562 (chronic myelogenous leukemia) cell line.

Exploring the interaction between tyrphostin 9 and human serum albumin using biophysical and computational methods

Tyrphostin 9 (Tyr 9) is a potent platelet-derived growth factor receptor (PDGFR) inhibitor, which induces apoptosis in various cancer cell types. The binding of Tyr 9 to the major transport protein, human serum albumin (HSA) was investigated using several spectroscopic techniques and molecular docking method. Fluorescence quenching titration results showed progressive decrease in the protein fluorescence with increasing drug concentrations. A decreasing trend of the Stern-Volmer constant, K sv with increasing temperature characterized the drug-induced quenching as static quenching, thus pointed towards the formation of Tyr 9–HSA complex. The binding constant of Tyr 9–HSA interaction was found to lie within the range 3.48–1.69 × 105 M−1 at three different temperatures, i.e. 15 °C, 25 °C and 35 °C, respectively and suggested intermediate binding affinity between Tyr 9 and HSA. The drug–HSA complex seems to be stabilized by hydrophobic forces, van der Waals forces and hydrogen bonds, as suggested from the thermodynamic data as well as molecular docking results. The far-UV and the near-UV CD spectral results showed slight alteration in the secondary and tertiary structures, respectively, of the protein upon Tyr 9 binding. Interaction of Tyr 9 with HSA also produced microenvironmental perturbations around protein fluorophores, as evident from the three-dimensional fluorescence spectral results but increased protein’s thermal stability. Both competitive drug binding results and molecular docking analysis suggested Sudlow’s Site I of HSA as the preferred Tyr 9 binding site. Communicated by Ramaswamy H. Sarma

Characterization of human serum albumin's interactions with safranal and crocin using multi-spectroscopic and molecular docking techniques

Interaction mechanisms of human serum albumin (HSA) with safranal and crocin were studied using UV–Vis absorption, fluorescence quenching and circular dichroism (CD) spectroscopies as well as molecular docking techniques. Changes in absorbance and fluorescence of HSA upon interactions with both compounds were attributed to their binding to amino acid chromophores located in subdomains IIA and IIIA. Fluorescence secondary inner filter effect was excluded using 278 nm and 340 nm as the wavelengths of HSA's excitation and fluorescence while safranal and crocin absorbed at 320 nm and 445 nm, respectively. Stern-Volmer model revealed a static quenching mechanism involve the formation of non-fluorescent ground state complexes. Stern-Volmer, Hill, Benesi-Hilbrand and Scatchard models gave apparent binding constants ranged in 4.25 × 103 - 2.15 × 105 for safranal and 7.67 × 103 - 4.23 × 105 L mol−1 for crocin. CD measurements indicated that 13 folds of safranal and crocin unfolded the α-helix structure of HSA by 7.47–21.20%. In-silico molecular docking revealed selective exothermic binding of safranal on eight binding sites with binding energies ranged in −3.969 to −6.6.913 kcal/mol. Crocin exothermally bound to a new large pocket located on subdomain IIA (sudlow 1) with binding energy of −12.922 kcal/mol.These results confirmed the formation of HSA stable complexes with safranal and crocin and contributed to our understanding for their binding characteristics (affinities, sites, modes, forces … etc.) and structural changes upon interactions. They also proved that HSA can solubilize and transport both compounds in blood to target tissues. The results are of high importance in determining the pharmacological properties of the two phytochemical compounds and for their future developments as anticancer, antispasmodic, antidepressant or aphrodisiac therapeutic agents.

Thermodynamics, molecular modelling and denaturation studies on exploring the binding mechanism of tetramethylpyrazine with human serum albumin

Tetramethylpyrazine (TMPZ), a Chinese herb effectively used for cardiovascular disorders. The present study reports in vitro interaction studies of TMPZ with human serum albumin (HSA) using various spectroscopic, isothermal titration calorimetric (ITC), molecular modelling studies. The association constant (Ka), standard enthalpy change (ΔH°), standard entropy change (ΔS°) and standard Gibbs free energy change (ΔG°) were obtained from ITC. The thermodynamic investigations suggest that the interaction of HSA and TMPZ is an exothermic process and enthalpy driven. Far-UV CD spectroscopy has been applied to check the stability of HSA in presence of TMPZ under thermal and chemical denaturant condition. Molecular docking was performed to confirm the binding site of TMPZ on HSA and amino acids involved in the binding process and it is found that TMPZ binds at Sudlow site I of HSA. Comparative MD simulation study of HSA and HSA-TMPZ complex shows that the structure of HSA in both systems is stable and has almost similar properties. The binding free energies calculated from the molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) method showed that van der Waals forces are the predominant intermolecular forces. Esterase-like activity of HSA decreases in the presence of TMPZ. Thus, this study will provide useful information regarding the interaction of TMPZ with HSA, helping to understand the activity and mechanism of drug binding and highlights its importance in the clinical medicine.

Kinetic and Thermodynamic Investigation of Human Serum Albumin Interaction with Anticancer Glycine Derivative of Platinum Complex by Using Spectroscopic Methods and Molecular Docking

In this paper, a new anticancer Pt (II) complex, cis-[Pt (NH3)2(tertpentylgly)]NO3, was synthesized with glycine-derivative ligand and characterized. Cytotoxicity of this water-soluble Pt complex was studied against human cancer breast cell line of MCF-7. The interaction of human serum albumin (HSA) with Pt complex was studied by using UV-Vis, fluorescence spectroscopy methods, and molecular docking at 27 and 37°C in the physiological situation (I = 10mM, pH = 7.4). The negative [Formula: see text] and positive [Formula: see text] indicated that electrostatic force may be a major mode in the binding between Pt complex and HSA. Binding constant values were obtained through UV-Vis and fluorescence spectroscopy that reveal strong interaction. The negative Gibbs free energy that was obtained by using the UV-Vis method offers spontaneous interaction. Fluorescence quenching the intensity of HSA by adding Pt complex confirms the static mode of interaction is effective for this binding process. Hill coefficients, nH, Hill constant, kH, complex aggregation number around HSA, <J>, number of binding sites, g, HSA melting temperature, Tm, and Stern-Volmer constant, kSV, were also obtained. The kinetics of the interaction was studied, which showed a second-order kinetic. The results of molecular docking demonstrate the position of binding of Pt complex on HSA is the site I in the subdomain IIA.

Site-Selective Interaction of Human Serum Albumin with 4-Chloro-7-nitro-1,2,3-benzoxadiazole Modified Olanzapine Derivative and Effect of β-Cyclodextrin on Binding: In the Light of Spectroscopy and Molecular Docking.

Here, we present a detailed investigation on the interaction of 4-chloro-7-nitro-1,2,3-benzoxadiazole (NBD) embedded olanzapine derivative (OLA-NBD) with a model transport protein, human serum albumin (HSA). The thermodynamic parameters, ΔHo, ΔSo, and ΔGo, as evaluated by considering the van't Hoff relationship imply the major contribution of electrostatic/ionic interactions for the HSA-OLA-NBD association. The OLA-NBD induced quenching of HSA emission occurs through static quenching mechanism, indicating a 1:1 association, as portrayed from Benesi-Hildebrand plot, with ∼104 M-1 association constant value, and it is in good harmony with the value estimated from anisotropy experiment. The invariance of the time-resolved decay behavior of HSA with added OLA-NBD concentration, along with matching dependency of the binding constant (Kb) value on temperature, also supports the occurrence of static quenching. The effect of β-cyclodextrin on HSA-OLA-NBD binding is characterized by a smaller Kb value revealing that the OLA-NBD molecules are gradually removed from β-CD by HSA to achieve its medicinal outcome of drug delivery. The outcome from circular dichroism (CD) illustrates the variation of HSA secondary structure upon interaction with OLA-NBD. Concurrently, HSA-OLA-NBD association kinetics is also explored by applying the fluorescence technique. The possible interaction zone of OLA-NBD in HSA is investigated from AutoDock-based docking simulation study.

Maleic anhydride and acetylene plasma copolymer surfaces for SPR immunosensing

We report on the successful application of carboxyl-rich plasma polymerized (PP) films as a matrix layer for bioreceptor immobilization in surface plasmon resonance (SPR) immunosensing. Composition and chemical properties of the carboxyl-rich PP films deposited from a mixture of maleic anhydride and acetylene were investigated. Changes in the films stored in air, water, and buffer were studied and the involved chemical changes were described. Performance in SPR immunosensing was evaluated on interactions of human serum albumin (HSA) with a specific monoclonal antibody. The comparison with the mixed self-assembled monolayer of mercaptoundecanoic acid and mercaptohexanol (MUA/MCH) and one of the most widely used surfaces for SPR, the 2D and 3D carboxymethylated dextran (CMD), was presented to show the efficacy of plasma polymerized matrix layers for biosensing. The PP film-based SPR immunosensor provided a similar detection limit of HSA (100ng/mL) as MUA/MCH- (100ng/mL) and 3D CMD (50ng/mL)-based sensors. However, the response levels were about twice higher in case of the PP film-based immunosensor than in case of MUA/MCH-based alternative. The PP film surfaces had similar binding capacity towards antibody as the 3D CMD layers. The response of PP film-based sensor towards HSA was comparable to 3D CMD-based sensor up to 2.5μg/mL. For the higher concentrations (> 10μg/mL), the response of PP film-based immunosensor was lower due to inaccessibility of active sites of the immobilized antibody inside the flat PP film surface. We have demonstrated that due to its high stability and cost-effective straightforward preparation, the carboxyl-rich PP films represent an efficient alternative to self-assembled monolayers (SAM) and dextran-based layers in label-free immunosensing. Graphical abstract.

Towards the functional high-resolution coordination chemistry of blood plasma human serum albumin

Human serum albumin (HSA) is a monomeric, globular, multi-carrier and the most abundant protein in the blood. HSA displays multiple ligand binding sites with extraordinary binding capacity for a wide range of ions and molecules. For decades, HSA's ability to bind to various ligands has led many scientists to study its physiological properties and protein structure; indeed, a better understanding of HSA-ligand interactions in human blood, at the atomic level, will likely foster the development of more potent, and overall more performant, diagnostic and therapeutic tools against serious human disorders such as diabetes, cardiovascular disorders, and cancer. Here, we present a concise overview of the current knowledge of HSA's structural characteristics, and its coordination chemistry with transition metal ions, within the scope and limitations of current techniques and biophysical methods to reach atomic resolution in solution and in blood serum. We also highlight the overwhelming need of a detailed atomistic understanding of HSA dynamic structures and interactions that are transient, weak, multi-site and multi-step, and allosterically affected by each other. Considering the fact that HSA is a current clinical tool for drug delivery systems and a potential contender as molecular cargo and nano-vehicle used in biophysical, clinical and industrial fields, we underline the emerging need for novel approaches to target the dynamic functional coordination chemistry of the human blood serum albumin in solution, at the atomic level.

Effect of Geometrical Structure, Drying, and Synthetic Method on Aminated Chitosan-Coated Magnetic Nanoparticles Utility for HSA Effective Immobilization.

Human serum albumin (HSA) is one of the most frequently immobilized proteins on the surface of carriers, including magnetic nanoparticles. This is because the drug–HSA interaction study is one of the basic pharmacokinetic parameters determined for drugs. In spite of many works describing the immobilization of HSA and the binding of active substances, research describing the influence of the used support on the effectiveness of immobilization is missing. There are also no reports about the effect of the support drying method on the effectiveness of protein immobilization. This paper examines the effect of both the method of functionalizing the polymer coating covering magnetic nanoparticles (MNPs), and the drying methods for the immobilization of HSA. Albumin was immobilized on three types of aminated chitosan-coated nanoparticles with a different content of amino groups long distanced from the surface Fe3O4-CS-Et(NH2)1–3. The obtained results showed that both the synthesis method and the method of drying nanoparticles have a large impact on the effectiveness of immobilization. Due to the fact that the results obtained for Fe3O4-CS-Et(NH2)2 significantly differ from those obtained for the others, the influence of the geometry of the shell structure on the ability to bind HSA was also explained by molecular dynamics.

Role of Herborn (K240E) and Milano Slow (D375H) human serum albumin variants towards binding of phenylbutazone and ibuprofen

Human serum albumin (HSA) is the binding cargo in blood plasma. The binding of drugs to HSA determines the pharmacokinetics and pharmacodynamics of the drugs. There are 67 natural genetic variants of HSA were reported in literature. Studying the effect of albumin modifications on drug binding helps to treat the patients with proper medication. In the present study, we have aimed to understand the effect of two natural variants of HSA, such as Herborn (K240E) and Milano Slow (D375H) on the binding of phenylbutazone and ibuprofen. For this, we have generated K240E and D375H mutants and also double mutant (K240E/D375H) of HSA using site directed mutagenesis. The recombinant HSA and its variants were expressed in Pichia pastoris. The interaction of HSA and its variants to phenylbutazone and ibuprofen was studied using fluorescence spectroscopy. Our results showed that there is no significant effect of K240E and D375H mutations on phenylbutazone and ibuprofen binding. But the effect is significant when both the mutations were there in a single protein (K240E/D375H). Further, the CD spectroscopy data showed that there is no effect of phenylbutazone and ibuprofen binding on the conformation of protein, except in case of D375H, where there is a conformational change in the binding pocket with the ibuprofen binding.

Binding interaction study on human serum albumin with bactericidal gold nanoparticles synthesized from a leaf extract of Musa balbisiana: a multispectroscopic approach.

This study describes the eco-friendly, low-cost and room-temperature synthesis of gold nanoparticles from Musa balbisiana leaf extract, which acts as both reducing and stabilizing agent, and characterized by ultraviolet-visible (UV-vis) light spectroscopy, fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FE-SEM), analytical transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDAX) and dynamic light scattering (DLS) instruments. These nanoparticles showed an average diameter of 33.83±3.39nm, which was confirmed from the size distribution histogram. The bactericidal activity of these nanoparticles was confirmed using bacteria Escherichia coli and Staphylococcus aureus at 1 and 2nM minimum inhibitory concentrations, respectively. The interaction between nanoparticles and human serum albumin (HSA) was investigated, as this plays significant roles in biological systems. The nature of interaction, binding parameters and structural variation of HSA in the presence of these nanoparticles have been evaluated using several useful spectroscopic approaches such as UV-vis, FTIR, time-resolved and steady-state fluorescence, and circular dichroism in addition to the measurement of zeta potential. This interaction study revealed that static quenching occurs in this process with minimal alteration in the secondary structure, but the native structure of HSA remained unaltered. The binding constant and thermodynamic parameters of this interaction process were also evaluated.

In silico study: the antiglycation potency of aloin on the protein surface of human serum albumin

Advanced glycation end products (AGEs) is an end product of glycemic protein/fat/nucleic acid reactions with excessive glucose. One protein that is susceptible to glycemic reactions is the human serum albumin (HSA). Aloin is a proven natural substance in vitro can be used as an antiglycation, but not yet known as antiglycation target for HSA protein. Therefore, this study objective is to produce in silico prediction for antiglycation potency of aloin based on the pattern and binding affinity of aloin-protein HSA interactions. This study was performed by molecular docking methods using autodock vina program which integrated in PyRx 0.8 software. The ligands used are aloin, and glucose. The results of this study indicate that sub-domains 1B and 2A of HSA protein are the main target of antiglycation of aloin, with aloin’s antiglycation ability increased in further glycation.

Domain-Specific Stabilization of Structural and Dynamic Responses of Human Serum Albumin by Sucrose.

Human Serum Albumin (HSA) is the most abundant protein present in human blood plasma. It is a large multi-domain protein with 585 amino acid residues. Due to its importance in human body, studies on the interaction of HSA with different external agent is of vital interest. The denaturation and renaturation of HSA in presence of external agents are of particular interest as they affect the biological activity of the protein. The objective of this work is to study the domain-specific and overall structural and dynamical changes occurring to HSA in the presence of a denaturing agent, urea and a renaturing agent, sucrose. In order to carry out the domain-specific studies, HSA has been tagged using N-(7- dimethylamino-4-methylcoumarin-3-yl) iodoacetamide (DACIA) at Cys-34 of domain-I and pnitrophenyl coumarin ester (NPCE) at Tyr-411 site in domain-III, separately. Steady-state absorption, emission and solvation dynamic measurements have been carried out in order to monitor the domain-specific alteration of HSA caused by the external agents. The overall structural change of HSA have been monitored using circular dichroism spectroscopy. The α-helicity of HSA was found to decrease from 65% to 11% in presence of urea and was found to further increase to 25% when sucrose is added, manifesting the denaturing and renaturing effects of urea and sucrose, respectively. The steady state studies show that domain-III is more labile towards denaturation as compared to domain-I. The presence of an intermediate state is observed during the denaturation process. The stabilization of this intermediate state in presence of sucrose is attributed as the reason for the stabilization of HSA by sucrose. From solvation dynamics studies, it could be seen that the solvation time of DACIA inside domain-I of HSA decreases and increases regularly with increasing concentrations of urea and sucrose, respectively, while in the case of NPCE-tagged domain-III, the effect of sucrose on solvation time is evident only at high concentrations of urea. The denaturing and renaturing effects of urea and sucrose could be clearly seen from the steady state studies and circular dichroism spectroscopy measurements. A regular change in solvation time could only be observed in the case of domain-I and not in domain-III. The results indicate that the renaturing effect of sucrose on domain-III is not very evident when protein is in its native state, but is evident in when the protein is denatured.