Negative Enthalpy Change Research Articles

Nylon fibers coated with diclofenac: adsorption properties

Dried gauzes properly coated with anti-inflammatory drugs could be helpful in providing topical treatment in inflammatory process. Therefore, thermodynamic of adsorption of Diclofenac Sodium, over Nylon fibers, as a function of concentration, temperature, and pH of the medium, have been studied. Maximum amount adsorbed in the best conditions tested, pH 5.6, 323 K and initial concentration of 150 mg/L has been 2.6 mg/g. Isotherm adsorption data were well fitted to the Langmuir and Freundlich model; therefore, multilayer formation must be considered. Negative and low values of free-energy change, −17.9 kJ/mol and −15.9 kJ/mol, in addition to moderate value of activation energy 13.14 kJ/mol point to physical interactions governing the process that, besides, is exothermic with negative enthalpy-change, −43.44 kJ/mol, and also follows pseudo-first order kinetic model that is typical of this interaction. Desorption experiments carried out under physiological conditions confirm that the proposed procedure for DCF administration could be achieved.

Mechanistic insights into the inhibition of quercetin on xanthine oxidase

Quercetin, one of the most abundant flavonoid in the daily diet, was found to reversibly inhibit the generation of uric acid and superoxide radicals (O2−)catalyzed by xanthine oxidase (XOD) in a mixed-type manner with IC50 values of (2.74±0.04)×10−6 and (2.90±0.03)×10−6molL−1, respectively, and the inhibition of quercetin on O2− generation may be ascribed to the reduced form of XOD by a ping-pong mechanism. XOD had one high affinity binding site for quercetin with a binding constant of 4.28×104Lmol−1 at 298K, and the binding process was predominately driven by van der Waals forces and hydrogen bonds on account of the negative enthalpy and entropy changes. Moreover, molecular docking confirmed that the binding site for quercetin located in the isoalloxazine ring of the flavin adenine dinucleotide (FAD) domain of XOD, then the diffusion of O2− out of the FAD site was blocked in favor of another electron transferred from FADH2 to O2− to form hydrogen peroxide (H2O2). This study may clarify the role of quercetin on inhibiting XOD catalysis and provide a potential nutritional supplement for preventing gout and peroxidative damage.

Efficiency evaluation of arsenic(III) adsorption of novel graphene oxide@iron-aluminium oxide composite for the contaminated water purification

Abstract Prolong consumption of arsenic-rich drinking water causes serious health problem. Aiming to minimize the problem, it is attempted to develop cheap and advanced materials for arsenic extraction from the contaminated water. Thus, multifunctional graphene oxide (GO)-incorporated iron-aluminium mixed oxide (GIAMO) composite has been prepared with five different GO content, and evaluated by batch method for the arsenic(III) removal efficiency. Among the as-prepared GIAMO samples, three samples consisting 1.0, 2.0 and 3.0 g of GO show equally good (92–95%) arsenic(III) removal efficiency, which is 30–35% higher than pristine iron-aluminium oxide (IAMO) from an aqueous solution (5.0 mg AsIII·L−1) at pH 7.0 (± 0.2) and 303 K. Thus, 1.0 g GO-inserted GIAMO (GIAMO-1) sample was characterized as microcrystalline (10–15 nm) with BET surface area about 1.45 times higher than IAMO and investigated for the arsenic(III) adsorption. Optimized pH for arsenic(III) adsorption is 6.0–8.0. The kinetic data agree more closely with pseudo-first order equation (R2 = 0.98–0.99) than pseudo-second order equation (R2 = 0.92–0.93). The equilibrium data describe the Langmuir isotherm (R2 = 0.97–0.98) better than the Freundlich isotherm (R2 = 0.91–0.92), showing the Langmuir monolayer capacity 42.2836 mg·g−1 at 293 K which drops to 24.9170 mg·g−1 at 313 K. High negative enthalpy change (ΔH° ∼ −224 kJ. mol−1) is responsible for the spontaneous reaction (ΔG° = negative) despite unfavorable entropy change (ΔS° = −0.71 kJ. mol−1). The order of competitive effect of PO43−, SO42− and HCO3− on arsenic(III) removal efficiency is PO43− > SO42− > HCO3−. However, the high HCO3− (> 200 mg·L−1) enhances the arsenic(III) removal efficiency of this material. 2.0 M NaOH can regenerate arsenic adsorbed GIAMO-1 only up to 50–60%. 0.65 g. of composite per L of high arsenic (Astotal: 0.115 mg L−1) groundwater can upgrade to potable standard, encouraging possible safe use for high arsenic water treatment. Highly negative enthalpy change, poor regeneration, FTIR, XRD and CV analyses of arsenic-rich solid suggested that arsenic(III) is stabilized over the solid surface without oxidation by surface complex formation.

<i>Ab Initio</i> Study of Proton Transfer and Hydration in Phosphorylated Nata de Coco

This research aims to calculate energetics parameters, hydrogen bonding, characteristics local hydration, and proton transfer in phosphorylated nata de coco (NDCF) membrane using ab initio method. The minimum energy structure of NDCF membranes and the addition of n water molecules (n = 1-10) determined at the B3LYP/6-311G** level indicates that proton dissociation requires a minimum of four water molecules. Dissociated protons stabilize with the formation of (hydronium, Zundel, Eigen) ions. Calculation of the interaction energy with n water molecules indicates an increasingly negative change in energy (ΔE) and enthalpy (ΔH), and hence an increasingly positive interaction with water molecules. This interaction facilitates the transfer of protons in the membrane matrix. Calculation of the rotational energy at the center of C-O indicates that the pyranose ring structure, with a maximum barrier energies of ~ 12.5 J/mol, is much more flexible than the aromatic backbones of sulfonated poly(phenylene) sulfone (sPSO2) and the polytetrafluoroethylene (PTFE) backbones in perfluorosulfonic acid ionomers (PFSA). These energy calculations provide the basis that the flexibility of the pyranose ring and the hydrogen bonding between water molecules and phosphonate groups influence the transfer of protons in the membrane of NDCF.

Abiotic production of sugar phosphates and uridine ribonucleoside in aqueous microdroplets

Phosphorylation is an essential chemical reaction for life. This reaction generates fundamental cell components, including building blocks for RNA and DNA, phospholipids for cell walls, and adenosine triphosphate (ATP) for energy storage. However, phosphorylation reactions are thermodynamically unfavorable in solution. Consequently, a long-standing question in prebiotic chemistry is how abiotic phosphorylation occurs in biological compounds. We find that the phosphorylation of various sugars to form sugar-1-phosphates can proceed spontaneously in aqueous microdroplets containing a simple mixture of sugars and phosphoric acid. The yield for d-ribose-1-phosphate reached over 6% at room temperature, giving a ΔG value of -1.1 kcal/mol, much lower than the +5.4 kcal/mol for the reaction in bulk solution. The temperature dependence of the product yield for the phosphorylation in microdroplets revealed a negative enthalpy change (ΔH = -0.9 kcal/mol) and a negligible change of entropy (ΔS = 0.0007 kcal/mol·K). Thus, the spontaneous phosphorylation reaction in microdroplets occurred by overcoming the entropic hurdle of the reaction encountered in bulk solution. Moreover, uridine, a pyrimidine ribonucleoside, is generated in aqueous microdroplets containing d-ribose, phosphoric acid, and uracil, which suggests the possibility that microdroplets could serve as a prebiotic synthetic pathway for ribonucleosides.

Kinetics, isotherms and thermodynamic evaluation of amine functionalized magnetic carbon for methyl red removal from aqueous solutions

Global fresh water demand increases as population increases. Thus, the demand for cost-effective materials and efficient technologies for water treatment is on the rise. Here, we modified rubber-derived carbon by iron oxide and then the obtained material was subjected to surface modification using typical branched polyethylenimine (BPEI) to produce a magnetic composite of AC-FexOy-BPEI. The composite was characterized. The efficiency of the polymer anchored material was examined for methyl red (MR) removal from aqueous media in the batch and column systems. The results indicated a high percentage of removal (≈100%) and eequilibrium was observed in 10mins. The process followed models of the Langmuir isotherm and Pseudo-second order, with a capacity of 526mg/g. The negative standard enthalpy change (∆Ho) suggests that the adsorption of MR on the material is exothermic. The breakthrough was observed after 150mins using a 1mM concentration of methyl red flow through a designed short column. The AC-FexOy-BPEI demonstrated remarkable efficiency in removing MR from aqueous solutions. The high adsorption capacity does indeed make the amine-modified material as an effective sorbent. The material leverages its cost-effective source, in addition to the ease of preparation along with its fast uptake capacities, it offers great promise for wastewater remediation.

In vitro binding comparison of cephalosporins to human serum albumin by spectroscopy and molecular docking approaches: A novel structural pursuing

Contamination of antibiotic residues in food and water is an understudied safety concern and is increasingly gaining importance worldwide due to the rising rates of drug resistant organisms. As a class of antibiotics targeting β-lactam, cephalosporin is frequently used in treatment of bacterial infections. In this study, molecular modeling approaches in combination with absorbance, fluorescence and circular dichroism spectroscopy was employed to investigate the interactions of four cephalosporins (cefalexin, cefaclor, cefixime and cefepime) with human serum albumin (HSA). In the mechanism discussion, it was proved that the fluorescence quenching of HSA by cephalosporin is a result of the formation of cephalosporin-HSA complex. Binding parameters calculating from Stern-Volmer method and Scatchard method showed that cephalosporin bind to HSA with the binding affinities of the order 103–104L·mol−1. The thermodynamic parameters studies revealed that the binding was characterized by negative enthalpy and negative entropy changes and the hydrogen bonds and van der Waals interactions may play major role in complex formation. Furthermore, the investigated result indicates that azyl served as a hydrophilic group to change the chemical property for drug, the chlorine atom on the R1-group of cefaclor weakened the overall molecular polarity or hydrophilicity, while the binding site on HSA was determined by the carboxylate of cefepime. Some other structural characteristics for four kind of cephalosporins were also exhibited in this paper.

Assessment of fish scales waste as a low cost and eco-friendly adsorbent for removal of an azo dye: Equilibrium, kinetic and thermodynamic studies

In this study, AB113 dye was successfully sequestered using a novel adsorbent made of mixed fish scales (MFS). The influence of adsorbent dosage, initial pH, temperature, initial concentration and contact time on the adsorption performance was investigated. The surface chemistry and morphology of the adsorbent were examined by FTIR, TGA and SEM. Amides, phosphate and carbonate groups were evidently responsible for the high affinity of MFS towards the dye. The adsorption equilibrium and kinetic were well described by Langmuir and pseudo-second-order models, respectively. The maximum adsorption capacities of MFS were 145.3–157.3mg/g at 30–50°C. The adsorption of AB113 dye onto the adsorbent was exothermic and spontaneous as reflected by the negative enthalpy and Gibbs energy changes. The results support MFS asa potential adsorbent for AB113 dye removal.

Self-structure assembly in single stranded polyriboadenylic acid by benzophenanthridine alkaloid: Spectroscopic and calorimetric exploration

Present study allows us a better understanding of the interaction of nitidine, a benzophenanthridine alkaloid with single stranded polyriboadenylic acid [ss-poly (rA)]. The interaction leads to self-structure induction in ss-poly (rA) under the experimental condition of pH 7.0. Interaction of nitidine with ss-poly (rA) was ascertained by monitoring the change in absorbance, fluorescence intensity and circular dichroism values. Binding mode of nitidine with ss-poly (rA) was observed to be intercalation as confirmed from the quenching and viscometric studies. The association was characterized by both negative enthalpy and entropy changes accompanying with a moderately high binding constant of 5.10×105M−1. Nitidine induced double helical organization in single stranded poly (rA) under the experimental pH.

Molecular interaction between human serum albumin (HSA) and phloroglucinol derivative that shows selective anti-proliferative potential

Phloroglucinol and its derivatives possess wide array of biopotentials such as antimicrobial, antioxidant, anti-inflammatory, anticancer and anti-metastatic properties. In the present investigation, for the first time, we report the anticancer potential and pharmacokinetic properties of 2,4,6-triacetylphloroglucinol (TAPG) through anti-proliferative assay and its molecular interaction with human serum albumin (HSA). HSA – TAPG interaction was explored through steady-state fluorescence, time-resolved fluorescence (TRF), circular dichroism (CD), isothermal titration calorimetry (ITC) and computational approaches. TAPG showed significant cytotoxicity towards lung, breast, colon and cervical cancer cell lines with minimal effect on normal cells. In steady-state fluorescence, the binding of TAPG strongly quenched the intrinsic fluorescence of HSA through static quenching mechanism. This explains the ground-state complex formation which was also evidenced in lifetime measurements. At different molar concentrations of TAPG, the helical content of HSA decreased and thereby influenced the secondary structural content of protein. Calculation of binding constant through fluorescence and ITC studies revealed the reversible and moderate affinity of TAPG towards HSA which allows the compound to diffuse easily from circulatory system to target tissue. Thermodynamic parameters from ITC exhibited a negative enthalpy, positive entropy and negative free energy change for HSA – TAPG interaction. This elucidates the exothermic and spontaneous reaction of binding with involvement of electrostatic interactions. Molecular docking studies showed that TAPG formed interactions with polar residues of inner and outer cluster region of site I with more affinity than site II. It was also noticeable that TAPG interactions were more stable in site I than site II during 50ns molecular dynamic simulation. Altogether, these results explain the favorable binding of TAPG with HSA which affects the drug distribution making it more bioavailable.

Investigation of itraconazole ternary amorphous solid dispersions based on povidone and Carbopol

We investigate a ternary system that consists of itraconazole (ITZ) and two polymers: povidone K12 and Carbopol 907. The interactions between these two polymers and their effects on the properties of ternary ITZ amorphous solid dispersions (ASDs) are studied. These two polymers can form a water-insoluble complex in acidic aqueous media. The critical pH is determined to be 4.17. The weight percentage of Carbopol 907 in the interpolymer complex range from 59 to 70%, depending on the initial ratios between these two polymers in the starting solutions. This complexation is driven by a negative enthalpy change from the H-bonding between the two polymers and a positive entropy change from the freed water molecules. Due to the slow precipitation of the interpolymer complex in aqueous media, the attempt to prepare ternary ASD using solvent-controlled coprecipitation is not successful. Melt extrusion is identified to be the only viable method to prepare this ternary ASD. We find that interpolymer complex–based ASDs are physically less stable and demonstrate the poorest drug-release properties when compared to individual polymer-based binary ASDs. This study illustrates that the too strong interaction between polymers in ternary ASDs is detrimental to their performance.

The inclusion complex of oxyresveratrol in modified cyclodextrins: A thermodynamic, structural, physicochemical, fluorescent and computational study

The interaction between oxyresveratrol (a type of stilbene with high biological activity) and modified cyclodextrins (CDs) was studied. Using HPLC-RP, was seen to form a 1:1 complex with all the CDs tested. The best CD in this respect was MβCD (KF=606.65±30.18M−1), the complexation showing a strong dependence on pH and temperature: The complexation constant (KF) decreased as the pH and temperature increased. The thermodynamic parameters studied (ΔH°, ΔS° and ΔG°) showed negative entropy, enthalpy and Gibbs free energy change at 25°C. In addition, fluorescence signal of oxyresveratrol increased when MβCD was added. The oxyresveratrol emission and excitation spectra were obtained for first time. A 1H NMR was carried out to study the structure of the complex and, DSC studied demonstrated the complexation. A computational study by molecular docking was made to complement the structural study.

Synthesis, characterization, structure and DNA binding aspects of a trinuclear copper(II) complex having a Cu3O core

The oxime based ligand, 3-(thiophen-3-yl-methylene-hydrazono)-butan-2-one oxime, has been synthesised by the 1:1 Schiff-base condensation of diacetyl-monoxime monohydrazone with thiophene-2-carboxaldehyde in methanol. Subsequently, the trinuclear copper(II) complex was synthesized by 1:1 reaction of the above ligand with Cu(ClO4)2·6H2O. Both the ligand and complex have been characterized by C, H, N microanalyses, ESI-MS, FT-IR and UV–Vis spectra. The X-ray crystal structure of the complex has been determined. The structure revealed that the oximato bridged trinuclear copper(II) compound has a discrete Cu3O core. The DNA binding aspect of both the ligand and complex was studied by several spectroscopic techniques. The thermodynamic parameters of binding were also determined by temperature dependent fluorescence titrimetric means. The negative enthalpy and entropy change suggest that the interaction may take place via van der Waal’s interaction or hydrogen bond formation.

Investigation of BTEX compounds adsorption onto polystyrenic resin

In this study, the adsorptive capacity of polystyrenic resin was evaluated for the removal of benzene, toluene, ethylbenzene and isomers of xylene (BTEX) from an aqueous solution. Batch studies were performed to evaluate the effects of various experimental parameters such as mixing strength, contact time, internal diffusion, adsorbates and initial concentration on the removal of the BTEX compounds. The equilibrium isotherms for the adsorption of the adsorbates on the PAD 910 polystyrenic resin were analyzed by the Langmuir and linearized Dubinin–Radushkevich models at pH of 5.86. The Langmuir model fitted the data adequately; is concluded that the latter is the most practical model in representing the adsorption of aromatic compounds. The Langmuir model indicated that resin has the highest adsorption capacity of 79.44 mg/g. At temperature of 25 °C, resin was found to adsorb 98% of benzene, 88% of toluene, 59% of ethylbenzene, 84% m-;p-xylene and 90% o-xylene at an initial concentration of 14.47 mg/l. The pseudo-second order rate model fitted better to the adsorption kinetics. The thermodynamic analysis resulted in a negative equilibrium enthalpy change suggesting an exothermic process.

A Study of Disorder-to-Order Transition by Characterizing the Binding Partners using a Statistical Potential

It is crucial to understand the biophysical properties of intrinsically disordered proteins (IDPs) and protein regions (IDRs) as they participate in numerous biological functions by exhibiting a multitude of structural conformations and dynamics. While the molecular recognition functions of IDPs/IDRs include pathways to carry out signaling and regulation, the structural heterogeneity of IDPs are highly linked to the amyloid aggregation that is involved in critical human diseases such as Parkinson's disease, Alzheimer's disease, type II diabetes and others. The functional advantages of IDPs/IDRs are primarily facilitated by their disorder-to-order transitions, specifically in short regions, through low affinity binding with a variety of partners. We found that about 21% of the proteins in DisProt have structural models in PDB, either in full or in part. We developed and deployed a novel statistical potential, termed Position Specific Estimated Energy (PSEE), to study the mechanism of free energy change required for disorder-to-order transition, mediated by negative enthalpy change of the system and increased entropy of the surrounding water. PSEE computes the potential of each residue from protein sequence alone using the pairwise thermodynamic interactions and the solvent accessibility of the residues in local neighborhood. In this study of characterizing the partner-binding sites within IDPs/IDRs and their transitions from disorder-to-order, we emphasize on determining the level of energy of the partners that induce the respective binding and, PSEE was effective in segregating the disordered and ordered residues by computing the energy gap in between. Further, we identified the binding region's likelihood of being disordered in its unbound state using a Disorder Predictor (DisPredict) developed by us. DisPredict is a SVM model with optimized radial basis function kernel and optimized threshold that employs a set of distinguishing attributes for disorder and order characterization including the novel PSEE. DisPredict, PSEE and our novel mechanism of partner-based identification of binding regions together, can assist in the experiments for drug discovery exploiting binding sites within IDPs/IDRs.

Oligomerization affects the kinetics and thermodynamics of the interaction of a Bowman-Birk inhibitor with proteases

The black-eyed pea trypsin/chymotrypsin inhibitor (BTCI) forms concentration dependent homomultimers, as previously demonstrated by Light scattering and Atomic Force Microscopy. Considering that these self-aggregates might influence their binding to cognate enzymes, we investigated the interaction of BTCI at picomolar concentrations using surface immobilized Chymotrypsin (α-CT) and Trypsin (T) by Surface Plasmon Resonance. Our results indicate that BTCI has subnanomolar affinity to both immobilized enzymes, which is approximately two orders of magnitude higher than previously reported. Moreover, we probed the influence of temperature on protein binding equilibria in order to investigate their interaction energetics. While the BTCI/T interaction concurs with the canonical entropy-driven mechanism described for BBI interactions with serine proteinases, the BTCI/α-CT interaction does not. Our measurements indicate that bimolecular BTCI/α-CT complexes form with a negative enthalpy change and a moderate entropic increase. Direct calorimetric evaluation is in accord with the van't Hoff approximation obtained by SPR. We demonstrate that as protein concentrations increase to the micromolar range, secondary endothermic events become prevalent and affect both the kinetics and thermodynamics of protein associations. Our study reinforces that BBI interactions with serine proteinases should be studied in dilute solutions to abridge often neglected secondary interactions.

Thermodynamics of adsorption of aromatic compounds from non-aqueous solutions by MIL-53(Al) metal-organic framework

The thermodynamics of adsorption of mono-, di-, and tricyclic aromatic compounds by MIL-53(Al) metal-organic framework from their solutions in MeCN, MeOH and n-C6H14–PriOH was studied for the first time. It was found that the adsorption of the test substances from solutions in MeCN and MeOH is characterized by positive values of enthalpy and entropy changes, and the adsorption from n-C6H14–PriOH medium is characterized by negative enthalpy and entropy changes. Upon adsorption by MIL-53(Al) framework from polar media, aromatic compounds were proposed to transfer from the liquid phase with a higher degree of association into the solvent medium with a lower degree of association, molecules of which are disordered due to the strong interaction with the hydrophobic walls of the framework pores. It was concluded that the driving force of adsorption by MIL-53(Al) from MeCN and MeOH is increase in entropy of the system, while the factor of adsorption from n-C6H14–PriOH medium is decrease in enthalpy of the adsorption system. The compensation effect in liquid-phase adsorption of aromatic compounds by MIL-53(Al) framework was discovered. The effect of the liquid phase nature on selectivity of adsorption from solutions onto investigated metal-organic framework was demonstrated.

Binding interaction of phenothiazinium dyes with double stranded RNAs: Spectroscopic and calorimetric investigation

RNA targeting through small molecules is an emerging and promising therapeutic route that necessitates identification of small molecules that can selectively target specific RNA structures. In this context a comparative study of the interaction of two phenothiazinium dyes thionine (THN) and toluidine blue O (TBO) with three double stranded RNA polynucleotides (ds RNAs) viz. poly(I).poly(C), poly(A).poly(U) and poly(C).poly(G) was conducted by various biophysical techniques. A higher binding of THN with poly(I).poly(C) over poly(A).poly(U) and poly(C).poly(G) was observed. The intercalative binding and RNA induced fluorescence quenching of the dyes through a static mechanism was confirmed by viscosity studies and steady state polarization anisotropy experiments. Binding induced structural perturbation in the RNA polynucleotides was confirmed from circular dichroism spectroscopy. DSC and thermal melting experiments confirmed that the binding resulted in strong thermal stabilization. The binding affinity of THN with poly(I).poly(C) was the highest followed by that to poly(A).poly(U) and poly(C).poly(G). The trend was the same for TBO also, but THN bound stronger than TBO. The binding of the dyes was characterized by strong negative enthalpy changes with minimum positive entropy changes indicating typical intercalative interaction. The results presented here may be useful to design new types of RNA binding antitumor, antibacterial and anticancer agents.

Spectroscopic study on the binding of chelerythrine with duplex poly (rA): A model of RNA intercalation

Here we have reported a detail study on the interaction of the benzophenanthridine alkaloid chelerythrine (CHL) with double stranded polyriboadenylic acid [ds poly (rA)] by exploiting various spectroscopic techniques. The alkaloid shows high binding affinity (binding constant is 1.10×105M−1) towards the double stranded RNA as revealed from Scatchard plot. The binding was confirmed by hypochromic effect in the UV–vis spectrum of CHL, increase in fluorescence intensity of CHL and perturbations of the circular dichroism (CD) spectrum of ds poly (rA). Later fluorescence quenching, cooperative CD melting transition, viscometric and molecular modeling studies establish the fact that the alkaloid binds to the ds poly (rA) by the mechanism of intercalation. Thermodynamic parameters obtained from the isothermal titration calorimetric (ITC) study show that the binding is favoured by negative enthalpy and small positive entropy changes. This report may be a model for intercalation of small molecule like CHL to the double stranded RNA.

Insights into the Thermodynamics of Polymer Nanodot-Human Serum Albumin Association: A Spectroscopic and Calorimetric Approach.

With the advent of newer luminescent nanoparticles for bioimaging applications, their complex interactions with individual biomolecules need to be understood in great detail, before their direct application into cellular environments. Here, we have presented a systematic and detailed study on the interaction between luminescent polymer nanodots (PNDs) and human serum albumin (HSA) in its free and ligand-bound state with the help of spectrophotometric and calorimetric techniques. At physiological pH (pH = 7.4), PNDs quench the intrinsic fluorescence of HSA as a consequence of ground-state complex formation. The binding stoichiometry and various thermodynamic parameters have been evaluated by using isothermal titration calorimetry and the van't Hoff equation. It has been found that the association of PNDs with HSA is spontaneous (ΔG0 = -32.48 ± 1.24 kJ mol-1) and is driven by a favorable negative standard enthalpy change (ΔH0 = -52.86 ± 2.12 kJ mol-1) and an unfavorable negative standard entropy change (ΔS0 = -68.38 ± 2.96 J mol-1 K-1). These results have been explained by considering hydrogen bonding interactions between amino and hydroxyl groups (-NH2 and -OH) of PNDs and carboxylate groups (-COO-) of glutamate (Glu) and aspartate (Asp) residues of HSA. The binding constant of PNDs with HSA is estimated to be 4.90 ± 0.19 × 105 M-1. Moreover, it has been observed that warfarin-bound HSA (war-HSA) shows a significantly lower binding affinity (Kb = 1.15 ± 0.19 × 105 M-1) toward PNDs, whereas ibuprofen-bound HSA (ibu-HSA) shows a slightly lower affinity (Kb = 3.47 ± 0.13 × 105 M-1) compared with the free HSA. In addition, our results revealed that PNDs displace warfarin from site I (subdomain IIA) of HSA because of the partial unfolding of war-HSA. We hope that the present study will be helpful to understand the fundamental interactions of these biocompatible PNDs with various biological macromolecules.