Enthalpy-entropy Compensation Research Articles

NMR Dynamic View of the Stabilization of the WW4 Domain by Neutral NaCl and Kosmotropic Na2SO4 and NaH2PO4.

The Hofmeister series categorizes ions based on their effects on protein stability, yet the microscopic mechanism remains a mystery. In this series, NaCl is neutral, Na2SO4 and Na2HPO4 are kosmotropic, while GdmCl and NaSCN are chaotropic. This study employs CD and NMR to investigate the effects of NaCl, Na2SO4, and Na2HPO4 on the conformation, stability, binding, and backbone dynamics (ps-ns and µs-ms time scales) of the WW4 domain with a high stability and accessible side chains at concentrations ≤ 200 mM. The results indicated that none of the three salts altered the conformation of WW4 or showed significant binding to the four aliphatic hydrophobic side chains. NaCl had no effect on its thermal stability, while Na2SO4 and Na2HPO4 enhanced the stability by ~5 °C. Interestingly, NaCl only weakly interacted with the Arg27 amide proton, whereas Na2SO4 bound to Arg27 and Phe31 amide protons with Kd of 32.7 and 41.6 mM, respectively. Na2HPO4, however, bound in a non-saturable manner to Trp9, His24, and Asn36 amide protons. While the three salts had negligible effects on ps-ns backbone dynamics, NaCl and Na2SO4 displayed no effect while Na2HPO4 significantly increased the µs-ms backbone dynamics. These findings, combined with our recent results with GdmCl and NaSCN, suggest a microscopic mechanism for the Hofmeister series. Additionally, the data revealed a lack of simple correlation between thermodynamic stability and backbone dynamics, most likely due to enthalpy-entropy compensation. Our study rationalizes the selection of chloride and phosphate as the primary anions in extracellular and intracellular spaces, as well as polyphosphate as a primitive chaperone in certain single-cell organisms.

Micellization, interaction forces and physicochemical parameters of tetradecyltrimethylammonium bromide in aqueous solution of crystal violet dye: Assessment of the influences of temperature, electrolytes and hydrotrope

The present study explores the interactions between tetradecyltrimethylammonium bromide (TTAB) and crystal violet (CV) dye in aq. Na-based electrolytes (NaCl, NaOAc, Na2SO4) and hydrotrope (sodium salicylate (NaSal)) media using conductometric technique. Physicochemical parameters (critical micelle concentration (CMC), degree of counter ion binding (β)) and thermodynamic variables (ΔGmo, ΔHmo, and ΔSmo)) were estimated. The CMC values of the study system were reduced with the increase of the concentrations of three Na-salts and the CMC values increased with the content of NaSal while the values increased with the escalation temperature. The spontaneous micellization of the TTAB+CV mixture was characterized by negative ΔGmo values. The ΔHmo and ΔSmo values expose the existence of hydrophobic interaction between TTAB and CV dye in aq. medium while these values connote the presence of electrostatic interaction along with hydrophobic interaction in aq. salts and NaSal media. Moreover, the molar heat capacity (ΔCm0), the thermodynamic of transfer (ΔGm,tr0, ΔHm,tr0 and ΔSm,tr0) and enthalpy–entropy compensation parameters for TTAB+CV mixture were estimated and analyzed with proper reasoning. The findings contribute to a deeper understanding of the interaction dynamics between TTAB and CV dye in aq. solutions of salts and NaSal environments, providing valuable insights for applications in relevant fields.

Investigation of the impacts of several diols on the phase behavior and physico-chemical quantities associated with the Triton X-100 and antidiabetic drug mixture

Drug-surfactant interaction phenomena have received popularity in the pharmaceutical industry and technological sectors from the view point of wider applications. Herein, we aimed to investigate the clouding behavior and various thermodynamic properties of Triton X-100 (TX-100) and metformin hydrochloride drug (MNH; an antidiabetic drug) mixture in the attendance of diols followed by the cloud point measurement technique. The dosage form of metformin hydrochloride drug controls the glucose level in the blood. The different types of diols, i.e., ethylene glycol (EG), 1,2-propylene glycol (1,2-PrG), 2,3-butanediol (2,3-BD), and 1,5-pentanediol (1,5-PD) were uniformly used in this inspection. The effect of diols, with the variation of their concentrations on the clouding behavior of TX-100 + MNH mixture having fixed content of TX-100 (92.7 mmol kg−1) and MNH drug (2 mmol kg−1), were examined. The most enhanced CP value was experienced in the aqueous 1,5-PD medium, whereas the lowest CP value was observed in the aqueous EG medium. The CP values were recorded for the working system under the effect of changing concentrations of diols, which were observed to follow the sequential order: CPH2O+1,5−PD>CPH2O+2,3−BD>CPH2O+1,2−PrG>CPH2O+EG. The clouding progression of the working system was realized to be nonspontaneous as concluded from the positive free energy change (ΔGco) values. The positive and negative values of enthalpy (ΔHco) and entropy (ΔSco) change were documented, respectively, at the low and high concentrations of diols. The hydrophobic interactions amongst different components are predominant at the low concentrations of diols, whereas the electrostatic interactions are leading factors at the high concentrations of diols. Enthalpy-entropy compensation parameters were computed and interpreted with proper perceptive. The outcomes of this observation may be effective and helpful in the various industrial sectors, especially in the drug carrier system in the pharmaceutical arena.

Investigation on itraconazole solubility in aqueous solutions based on models, solvent effect, thermodynamic analysis and quantum chemical calculations

The mole-fraction solubility of itraconazole in four aqueous blends of ethanol/isopropanol/DMSO/methanol within the temperature range of 283.15 to 323.15 K was experimentally obtained using the isothermal shake-flask method. Under the identical temperature and ethanol/isopropanol/DMSO/methanol composition, itraconazole solubility in DMSO+water is much higher than that in ethanol/isopropanol/methanol + water. At the same temperature, the solubility increases monotonically with organic solvent concentration. X-ray power diffraction analysis demonstrated that over the course of the investigations, there was no crystal transition or solvate formation. The modified van’t Hoff-Jouyban-Acree and Jouyban-Acree models adequately related the solubility to solvent composition and temperature, with relative average deviations (RADs) not exceeding 7.65 %. Furthermore, the extended Hildebrand solubility approach was utilized to quantitatively characterize the solubility behavior at 298.15 K for the mixtures of ethanol/isopropanol/DMSO/methanol plus water. In both instances, the RADs were maintained below 4.12 %. The solubility parameter and dipolarity-polarizability of solutions have a major impact on the solubility fluctuation, as indicated by the analysis of the linear solvation energy relationship. The preferential solvation of itraconazole at 298.15 K was examined using the efficient approach of inverse Kirkwood-Buff integrals. The preferred solvation parameters showed positive values in blends within rich and moderate ethanol/isopropanol/DMSO/methanol composition regions. This suggests that the organic solvents preferentially solvated itraconazole. When itraconazole dissolved in the blends, thermodynamic analysis of the entropy-enthalpy compensation and dissolution parameters revealed both an endothermic and an enthalpy-driven mechanism. Furthermore, the microscopic electrostatic characteristics of basicity and acidity were effectively demonstrated by means of the electrostatic potential of molecular surface. The −C=O and −N=groups of the itraconazole molecule, which link the five-membered ring, are the primary targets of the electrophilic attack. An independent gradient model based on Hirshfeld partition analysis was used to demonstrate the weak interactions between itraconazole and solvents.

Unifying the temperature dependent dynamics of glass formers.

Strong changes in bulk properties, such as modulus and viscosity, are observed near the glass transition temperature, Tg, of amorphous materials. For more than a century, intense efforts have been made to define a microscopic origin for these macroscopic changes in properties. Using transition state theory (TST), we delve into the atomic/molecular level picture of how microscopic localized unit relaxations, or "cage rattles," evolve to macroscopic structural relaxations above Tg. Unit motion is broken down into two populations: (1) simultaneous rearrangement occurs among a critical number of units, nα, which ranges from 1 to 4, allowing a systematic classification of glass formers, GFs, that is compared to fragility; and (2) near Tg, adjacent units provide additional free volume for rearrangement, not simultaneously, but within the "primitive" lifetime, τ1, of one unit rattling in its cage. Relaxation maps illustrate how Johari-Goldstein β-relaxations stem from the rattle of nα units. We analyzed a wide variety of glassy materials and materials with a glassy response using literature data. Our four-parameter equation fits "strong" and "weak" GFs over the entire range of temperatures and also extends to other glassy systems, such as ion-transporting polymers and ferroelectric relaxors. The role of activation entropy in boosting preexponential factors to high "unphysical" apparent frequencies is discussed. Enthalpy-entropy compensation is clearly illustrated using the TST approach.

Drying kinetics and water adsorption properties of jalapeño pepper seeds (Capsicum annuum L.): A study aiming at their recovery and integral exploitation

Drying kinetics (DK) and water adsorption isotherms (WAI) of Jalapeño pepper seeds (JPS) were evaluated and modeled at different temperatures. The proximate composition, flavonoid content (FC), and total phenolic compounds (TPC) of JPS were determined. Furthermore, JPS oil was extracted and characterized. Five mathematical models were tested to describe the JPS drying kinetics at five temperatures (40–80 °C) as well as the effective diffusion coefficient (Deff) and activation energy (Ea) were calculated. The WAI of the JPS was determined at nine temperatures (8–72 °C) and five mathematical models were fitted to JPS adsorption data. Thermodynamic properties were also estimated. The JPS presented TPC (30.9 mg GAE/g), FC (17.4 mg catechin equivalents/g), fibers (54.8 g/100 d.b.), lipids (22.2 g/100 d.b.), and proteins (15.5 g/100 d.b.). The study on drying kinetics pointed out that the Weibull model best fitted to drying kinetics data, Deff increased directly to temperature, and the Ea = 30.302 kJ/mol. The GAB model presented good accuracy in describing the WAIs that were classified as BET Type II. The net isosteric heat of adsorption and differential entropy decreased with increasing EMC. Enthalpy-entropy compensation theory was corroborated and characterized the adsorption of JPS as enthalpy-driven and spontaneous.

Tuning the thermostability of GHG gels by salts at different positions on the Hofmeister scale

The influence of Hofmeister cations (NH4+, Na+, Mg2+) and anions (H2PO4−, CH3COO−, Cl−, NO3−) on the thermostability of a GHG hydrogel was investigated. The combined results of UV circular dichroism (UVCD) and Small Amplitude Oscillatory Shear Rheology experiments reveal that the addition of salt reduces the stability of the gel phase and the underlying fibrils. In line with the cationic Hofmeister hierarchy, the chaotropic Mg2+ ions caused the greatest thermal destabilization of the gel phase with the gel → sol transition temperature Tgs value lowered by 10 °C. In the absence of salt, the gel → sol transition probed by the storage modulus and microscopy is biphasic. In the presence of salt, it becomes monophasic. Contrary to expectations the presence of Hofmeister anions leads to a nearly identical reduction of the gel → sol transition temperatures. However, UVCD spectra suggest that they affect the ππ-stacking between imidazole groups to a different extent. We relate the absence of ion specificity regarding the solubility of fibrils (probed by UVCD) to the observed enthalpy-entropy compensation of the dissolution process. Our results combined show how CD spectroscopy and rheology combined yields a more nuanced picture of the processes underlying the gel → sol transition.

Gibbs Free Energy and Enthalpy–Entropy Compensation in Protein–Ligand Interactions

The thermodynamics of protein–ligand interactions seems to be associated with a narrow range of Gibbs free energy. As a consequence, a linear enthalpy–entropy relationship showing an apparent enthalpy–entropy compensation (EEC) is frequently associated with protein–ligand interactions. When looking for the most negative values of ∆H to gain affinity, the entropy compensation gives rise to a barely noticeable increase in affinity, therefore negatively affecting the design and discovery of new and more efficient drugs capable of binding protein targets with a higher affinity. Originally attributed to experimental errors, compensation between ∆H and T∆S values is an observable fact, although its molecular origin has remained obscure and controversial. The thermodynamic parameters of a protein–ligand interaction can be interpreted in terms of the changes in molecular weak interactions as well as in vibrational, rotational, and translational energy levels. However, a molecular explanation to an EEC rendering a linear enthalpy–entropy relationship is still lacking. Herein, we show the results of a data search of ∆G values of 3025 protein–ligand interactions and 2558 “in vivo” ligand concentrations from the Protein Data Bank database and the Metabolome Database (2020). These results suggest that the EEC may be plausibly explained as a consequence of the narrow range of ∆G associated with protein–ligand interactions. The Gaussian distribution of the ∆G values matches very well with that of ligands. These results suggest the hypothesis that the set of ∆G values for the protein–ligand interactions is the result of the evolution of proteins. The conformation versatility of present proteins and the exchange of thousands (even millions) of minute amounts of energy with the environment may have functioned as a homeostatic mechanism to make the ∆G of proteins adaptive to changes in the availability of ligands and therefore achieve the maximum regulatory capacity of the protein function. Finally, plausible strategies to avoid the EEC consequences are suggested.

Enthalpy–entropy compensation and isoequilibrium relationship in thermo-chemical conversion of cigarette butt filters (CBFs) based on cellulose acetate (CA): causes and effects

Enthalpy–entropy compensation and isoequilibrium relationship in thermo-chemical conversion of cigarette butt filters (CBFs) based on cellulose acetate (CA): causes and effects

Quantitative entropy-enthalpy compensation in intraprotein interactions from model compound data.

Many small globular proteins exist in only two states-the physiologically relevant folded state and an inactive unfolded state. The active state is stabilized by numerous weak attractive contacts, including hydrogen bonds, other polar interactions, and the hydrophobic effect. Knowledge of these interactions is key to understanding the fundamental equilibrium thermodynamics of protein folding and stability. We focus on one such interaction, that between amide and aromatic groups. We provide a statistically convincing case for quantitative, linear entropy-enthalpy compensation in forming aromatic-amide interactions using published model compound transfer-free energy data.

Desorption properties of taioba (Xanthosoma taioba E.G. Gonç.) leaves: A non-conventional edible plant

This study aimed to determine the desorption isotherms and the thermodynamic properties of taioba leaves. For this, gravimetric-static method was used to determine the equilibrium moisture content (EMC) and water activity of taioba leaves at nine storage and drying temperatures (5–80 °C). The proximate composition was also determined. The Clausius-Clapeyron and Gibb's-Helmholtz equations were used to determine the net isosteric heat of desorption and differential entropy, respectively. The enthalpy-entropy compensation theory was also investigated. The relationship between water activity and equilibrium moisture content was best described by GAB model (Radj2 ≥0.987; χ2.105≤3.126; RMSE≤0.006) for the whole range of relative moistures and temperatures. The sigmoid-shaped type II was predominant at all temperatures. The net isosteric heat of desorption decreased from 8907.62 to 1120.15 J/mol as the moisture content increased. The linear relationship between enthalpy and entropy endorsed the enthalpy-entropy compensation mechanism in which TB > Thm, thus, an enthalpy-driven process. The free Gibbs energy was less than zero spontaneous (ΔGBstorage = −728.79 J/mol and ΔGBdrying = −1217.20 J/mol), indicating that water desorption is spontaneous. The spreading pressure varied from 0.001 to 0.05 J/m2 for all temperatures studied. The water surface area tended to decrease with increasing temperature, ranging from 185.71 to 251.97 m2/g. Therefore, this study provided an understanding of the water desorption properties of taioba leaves, contributing to the development of storage and drying practices.

Effects of short-chain alcohols and urea on the association of tetradecyltrimethylammonium bromide surfactant and cefixime trihydrate antibiotic: Conductometric and physicochemical analysis

This study explores the interaction of tetradecyltrimethylammonium bromide (TTAB), with an antibiotic drug, cefixime trihydrate (CMT), with a particular focus on conductivity changes as a reliable indicator of micelle formation. Influence of various alcohols (methanol (MeOH), ethanol (EtOH), 1-propanol (1-PrOH), 2-propanol (2-PrOH)), and urea on the physicochemical properties for micellization of TTAB in aq. alcohols/urea solutions of CMT was investigated. As the concentration of alcohol and urea increases, the critical micelle concentration (CMC) undergoes a notable rise, while the degree of counterion binding (β) shows a decreasing trend as a function of [alcohols]/[urea]. Elevated temperatures impede the creation of micelles, directing to an increase in the CMC, thus necessitating a higher surfactant concentration for micelle development. The alterations in free energy (∆Gmo), enthalpy (∆Hmo), entropy (∆Smo), and molar heat capacity (∆Cm0) were analyzed to evaluate the feasibility and driving forces behind the process of micelle development. The negative values of ∆Gmo indicate that the formation of micelles in the system being studied occurs spontaneously. The ∆Hmo and ∆Smo values suggest the existence of electrostatic forces (ion-dipole and H-bonding) between the components (TTAB, CMT, and alcohol) in aq. MeOH media. In contrast, hydrogen bonding, electrostatic forces, and hydrophobic interactions are involved in the solutions of the other three alcohols and urea medium. The thermodynamic parameters of transfer (∆Gm,tr0, ∆Hm,tr0, and ∆Sm,tr0) and enthalpy-entropy compensation variables were computed and discussed for TTAB micelles in the presence of CMT drug in employed solvents. The discoveries hold significant implications for drug formulation and industrial processes concerning surfactants and additives, providing valuable insights for optimizing their performance and properties.

Entropy-Enthalpy Compensation in Electron-Transfer Processes.

Solvent reorganization energies, free energies, and entropies are obtained for photoexcitation of three molecules that exhibit strong solvatochromism [Nile red, 5-(dimethylamino)-5'-nitro-2,2-bisthiophene, and Reichardt's dye B30] by measuring their optical absorption spectra at temperatures between 150 and 300 K in solvents with a range of polarities. Energies, free energies, and entropies of solvent reorganization are also obtained from computer simulations of three intramolecular electron-transfer reactions (charge separation and recombination in Zn-porphyrin-quinone cyclophane and charge transfer in a bis-biphenylandrostane radical anion). Entropy-enthalpy compensation in the solvent reorganization free energy for photoexcitation or electron transfer is found to be essentially complete (having nearly equal and opposite contributions from entropic and enthalpic effects) for all of the processes with solvent reorganization energies less than about 0.1 eV. Compensation becomes less complete as the reorganization energy becomes larger. A semiclassical treatment of the solvent reorganization entropy can rationalize these results.

Effect of Particle Diameter on Water Sorption by Rice Grains

AbstractWater sorption of non‐glutinous Uruchi and sticky Mochi rice grains of different diameters is kinetically analyzed using linear driving force and autocatalytic models. Water‐sorption curves are classified into two types based on their shape and according to the state of rice grains below and above the gelatinization temperature. Below the gelatinization temperature, the apparent activation energy and the frequency factor decrease with increasing rice‐particle diameter. The water sorption mechanisms of both types of rice appear to be the same in terms of the enthalpy–entropy compensation effect. Above the gelatinization temperature, it appears that the gelatinizable areas of starch granules contribute to the equilibrium moisture content, whereas the non‐gelatinizable areas affect the rate constant.

Aggregation behavior and thermodynamic parameters of biosurfactants (NaC/NaDC) in aqueous medium of Emtricitabine and Lamivudine (anti-HIV drugs)

Abstract This paper investigates the interactions and aggregation behavior of biosurfactants, sodium cholate (NaC) and sodium deoxycholate (NaDC) in aqueous solutions of Emtricitabine and Lamivudine (anti-HIV drugs). The study uses conductometry and UV–visible spectroscopy techniques to evaluate the critical micelle concentration (CMC) at different temperatures ranging from 298.15 K to 313.15 K with a variation of 5 K. The temperature dependence of the CMC was examined, and the stability of micelles was analyzed in light of the hydrophobic-hydrophilic interactions involved in this system. The CMC obtained from both the methods are in agreement. Various thermodynamic parameters, such as ∆ H m 0 ${\increment}{H}_{m}^{0}$ , ∆ S m 0 ${\increment}{S}_{m}^{0\hspace{0.17em}}$ and ∆ G m 0 ${\increment}{G}_{m}^{0}$ have been estimated using a “pseudo-phase separation model” to understand the contribution of the chemical and de-solvation part in the micellization process. Furthermore, the enthalpy-entropy compensation plots validate the micellar stability of the studied systems.

The Gibbs-Helmholtz equation and the enthalpy–entropy compensation (EEC) phenomenon in the formation of micelles in an aqueous solution of surfactants and the cloud point effect

Here, the hidden thermodynamic processes in the micellization of an aqueous surfactant solution are analyzed analytically. Based on the hidden processes, an equation for the self-association process was obtained, which represents the Gibbs-Helmholtz equation. For the existence of the enthalpy–entropy compensation (EEC) effect, the temperature dependence of the Gibbs free energy of micellization is necessary. In order to compare the EEC parameters of the clouding point effect with the EEC parameters of micellization, it is necessary to observe the clouding process in the direction of the surfactant transfer from the aqueous solution to the crystalline phase (opposite to what is usual in the literature). EEC parameter b (enthalpy change when entropy changes have the zero value) in the micellization process always has a negative value. In contrast, in the clouding point effect process, it can have both positive and negative values.

Effect of electrolytes on the mechanism of clouding process and physico-chemical quantities of non-ionic surfactant and ciprofloxacin hydrochloride mixture

An investigation of the clouding behaviour of the aqueous solution of ciprofloxacin hydrochloride (CIPH) + Triton X-100 (TX-100) under different electrolytes media was performed by the phase-changing measurement method. The CP of the resultant mixture has been studied in aqueous solutions of some organic and inorganic salts (sodium carbonate (Na2CO3), sodium oxalate (NaOxa), sodium acetate (NaOAc) and magnesium sulphate (MgSO4)). The CP values of TX-100 (50 mmol kg−1) + CIPH (1 mmol kg−1) solution decreases in the presence of all electrolytes while the CP values satisfy the sequence: CP (aq. NaOAc) > CP (aq. MgSO4) > CP (aq. Na2CO3) > CP (aq. NaOxa). The decrease in the solubility of employed solution in the aq. electrolytes media was observed and obtained maximum solubility in aqueous NaOAc and minimum solubility in the aqueous NaOXa medium. The obtained positive Gibbs-free energy ( Δ G c 0 ) demonstrates the nonspontaneous nature of phase separation while the extent of nonspontaneity exhibits the reduction with enhancing electrolyte concentrations. The Δ H c 0 and Δ S c 0 values depict the existences of electrostatic and hydrophobic interactions between TX-100 and CIPH in aq. electrolytes solutions and the clouding process is enthalpy controlled. Entropy-enthalpy compensation variables were computed.

Water desorption isotherms and thermodynamic properties of Ora-pro-nóbis (Pereskia aculeata Miller)

Desorption isotherms of ora-pro-nóbis leaves were determined at storage (5 °C, 10 °C, 20 °C, 30 °C, and 40 °C) and drying (40 °C, 50 °C, 60 °C, 70 °C, and 80 °C) temperatures by the gravimetric static method using saturated saline solutions to obtain relative humidities ranging from 5.20% to 98.48%. The net isosteric heat of desorption and thermodynamic properties such as differential enthalpy, differential entropy, and Gibbs free energy were also estimated. The GAB model presented the best parameters of fitting and the lowest Akaike and Bayesian information criteria values. The desorption isotherm patterns presented a sigmoid shape and were categorized as BET Type II sigmoid shape. The monolayer moisture content was estimated in 0.06 kg of water/kg of dry matter using the GAB model, and it remained constant at all temperatures. The leaves presented an optimal water activity equal to 0.35 at storage temperatures. The net isosteric heat of desorption decreased with increasing Xeq, and differential entropy increased with rising equilibrium moisture content (Xeq > 0.07). The enthalpy-entropy compensation was evaluated, and the desorption process is revealed to be entropy-driven and non-spontaneous.

Entropy-Enthalpy Compensation in Solvent Geometry Regulated Supramolecular Polymerization of Luminescent Napthalimide via a Non-Cooperative, Isodesmic Mechanism.

Supramolecular polymers of π-conjugated systems are an important class of materials with fascinating functions and properties originated from the dynamic behavior and highly ordered molecular organizations. Here, a donor-π-acceptor based functionalized luminescent napthalene monoimide (NMI) undergoes J-type self-assembly by non-covalent interactions via a non-cooperative, isodesmic mechanism to form supramolecular 1D nanowire. The fundamental insights into the thermodynamics regulating the supramolecular polymerization were derived through the fitting of the isodesmic model to variable temperature UV/Vis data in linear (dodecane) and nonliner hydrocarbon (decalin) based solvents. This shows a significant role of entropy-enthalpy compensation in solvent geometry-regulated formation and stabilization of supramolecular polymer. Furthermore, we have quantitively estimated the influence of solvent geometry and found that NMI forms stronger self-assembly and spontaneous gel in linear hydrocarbon based solvent compared to nonliner one and thereby substantially increases the degree of polymerization in linear hydrocarbon solvent (dodecane). This is accredited to the effective influence of the linear hydrocarbon solvent molecules in the polymerization process by favourable van der waals interactions with the peripheral alkyl chains of the NMI monomers in contrast to unfavourable interaction of nonliner hydrocarbon solvent due to geometry mismatch.

The impact of chemical properties of the solid-liquid-adsorbate interfaces on the entropy-enthalpy compensation involved in adsorption.

Despite extensive studies on the thermodynamic mechanism governing molecular adsorption at the solid-water interface, a comprehensive understanding of the crucial role of interface properties in mediating the entropy-enthalpy compensation during adsorption is lacking, particularly at a quantitative level. Herein, we employed two types of surface models (hydroxyapatite and graphene) along with a series of amino acids to successfully elucidate how distinct interfacial features dictate the delicate balance between entropy and enthalpy variations. The adsorption of all amino acids on the hydroxyapatite surface is an enthalpy-dominated process, where the water-induced enthalpic component of the free energy and the surface-adsorbate electrostatic interaction term alternatively act as the driving force for adsorption in different regions of the surface. Although favorable interactions are observed between amino acids and the graphene surface, the entropy-enthalpy compensation exhibits dependence on the molecular size of the adsorbates. For small amino acids, favorable enthalpy changes predominantly determine their adsorption behavior; however, larger amino acids tend to bind more tightly with the graphene surface, which is thermodynamically dominated by the entropy variations despite the structural characteristics of amino acids. This study reveals specific entropy-enthalpy mechanisms underlying amino acid adsorption at the solid-liquid interface, providing guidance for surface design and synthesis of new biomolecules.