Thermodynamic Insights Research Articles

Thermodynamic and kinetic insights into the adsorption mechanism of Cd(II) using Chlorella vulgaris cells with coverage modified by culture media engineering

Microalgae biomass is an adsorbent of special interest for heavy metal removal due to the large number of functional groups on their surface that provide excellent removal yields. A previous work of this research team showed that growing Chorella vulgaris under light and nitrogen limitation resulted in significant differences in terms of functional group composition and cadmium adsorption. This work expanded on previous results by delving into the mechanisms and the thermodynamic behavior of cadmium adsorption using C. vulgaris cells with different cell wall coverage by comparing adsorption kinetics, equilibrium isotherms, and energy levels. The results showed that a combination of physical mechanisms, such as hydrogen bonds, and chemical interactions dominated adsorption in the light-deprived cells. The kinetic tests showed a faster equilibrium and lower activation energy. Thermodynamic parameters showed a favorable spontaneity and a relatively low reaction energy. The process seems to be slightly endothermic, as higher temperatures favor adsorption in this case. In contrast, chemical interactions mediated by ion exchange predominated in the nitrogen-deprived microalgae, with deacetylated amino groups seemingly playing a key role. Adsorption is slower and requires higher amounts of energy. Spontaneity and equilibrium decrease at higher temperature and the process was clearly exothermic.These results provide deeper insights into the mechanisms of heavy metal adsorption using microalgae cells with modified coverage, an important advance in the field of biosorption and heavy metal removal that opens up novel lines of research with great potential for the industrial application of this technology.

Conceptual process design and process optimization of triple-column pressure-swing distillation for the separation of ternary mixtures embedding two azeotropes with different feed composition via thermodynamic insights and genetic algorithm

In this article, we take the tetrahydrofuran (THF)/ethanol (ETOH)/methanol (MeOH) as an example to investigate the process design of the triple-column pressure-swing distillation (TCPSD) for the separation of Serafimov’s class 2.0-2b mixtures with different feed composition. Two basic topology structures (TSI, TSII) and two separation sequences (SSI, SSII) are investigated, then, process optimization with total annual cost (TAC) as objective function is conducted via genetic algorithms. Heat integration (HI) is also applied to TCPSD. From a new perspective, the separation of THF/ETOH/MeOH can be regarded as the azeotropic distillation for THF/ETOH with MeOH as azeotropic agents based on thermodynamic features of Serafimov’s class 2.0-2b mixtures. The feasible topology structure and separation sequence of TCPSD for Serafimov’s class 2.0-2b mixtures depend on the feed composition and operating pressure. The feed composition is divided into three regions according to the concentration of methanol in azeotropic distillation column. The two critical points are azeotropic points at allowed minimum and maximum operating pressure. Especially, when feed composition is below azeotropic point at allowed minimum operating pressure, TSI is not feasible due to less MeOH as azeotropic agents. Furthermore, TCPSD combining pure azeotropic agents (ATPSD) can be developed based on this new insight. Then, two feed compositions are used to illustrate the detailed conceptual design of three topology structures as well as corresponding two separation sequences and their economic performance. The results show that when feed composition is 0.4ETOH/0.25THF/0.35MeOH, TSI and TSII are feasible, the best economical configurations without and with heat integration is TSII-SSII and TSII-SSII-HI. When feed composition is 0.4ETOH/0.4THF/0.2MeOH, TSII and ATPSD are feasible, the best economical configurations without and with heat integration is ATPSD-SSI and ATPSD-SSI-HI. Furthermore, ATPSD-SSI and ATPSD-SSI-HI have 18.28% and 19.38% TAC reduction than TSII-SSI and TSII-SSI-HI, respectively. In summary, feasible and the best economic topology structure and separation sequence of TCPSD for Serafimov’s class 2.0-2b mixtures depend on the feed composition and operating pressure. In addition, the proposed ATPSD shows good economic performance for Serafimov’s class 2.0-2b mixtures.

Thermodynamics and Viscoelastic Property of Interface Unravel Combined Functions of Cationic Surfactant and Aromatic Alcohol against Gram-Negative Bacteria.

Lipopolysaccharides (LPSs), the major constituents of the outer membranes of Gram-negative bacteria, play a key role in protecting bacteria against antibiotics and antibacterial agents. In this study, we investigated how a mixture of cationic surfactants and aromatic alcohols, the base materials of widely used sanitizers, synergistically act on LPSs purified from Escherichia coli using isothermal titration calorimetry (ITC), surface tension measurements, and quartz crystal microbalance with dissipation (QCM-D). ITC data measured in the absence of Ca2+ ions showed the coexistence of exothermic and endothermic processes. The exotherm can be interpreted as the electrostatic binding of the cationic surfactant to the negatively charged LPS membrane surface, whereas the endotherm indicates the hydrophobic interaction between the hydrocarbon chains of the surfactants and LPSs. In the presence of Ca2+ ions, only an exothermic reaction was observed by ITC, and no entropically driven endotherm could be detected. Surface tension experiments further revealed that the co-adsorption of surfactants and LPS was synergistic, while that of surfactants and alcohol was negatively synergistic. Moreover, the QCM-D data indicated that the LPS membrane remained intact when the alcohol alone was added to the system. Intriguingly, the LPS membrane became highly susceptible to the combination of cationic surfactants and aromatic alcohols in the absence of Ca2+ ions. The obtained data provide thermodynamic and mechanical insights into the synergistic function of surfactants and alcohols in sanitation, which will enable the identification of the optimal combination of small molecules for a high hygiene level for the post-pandemic society.

Thermodynamic Insight into the Equilibrium Component Prediction in the Al-Ti-Ca-Oxide System

Thermodynamic Insight into the Equilibrium Component Prediction in the Al-Ti-Ca-Oxide System

Griseofulvin: Thermodynamic insight to solubility, solvation and partition processes

Griseofulvin: Thermodynamic insight to solubility, solvation and partition processes

Probing the Melting Transitions in Phase-Change Superlattices via Thin Film Nanocalorimetry

Phase-change superlattices with nanometer thin sublayers are promising for low-power phase-change memory (PCM) on rigid and flexible platforms. However, the thermodynamics of the phase transition in such nanoscale superlattices remain unexplored, especially at ultrafast scanning rates, which is crucial for our fundamental understanding of superlattice-based PCM. Here, we probe the phase transition of Sb2Te3 (ST)/Ge2Sb2Te5 (GST) superlattices using nanocalorimetry with a monolayer sensitivity (∼1 Å) and a fast scanning rate (105 K/s). For a 2/1.8 nm/nm Sb2Te3/GST superlattice, we observe an endothermic melting transition with an ∼240 °C decrease in temperature and an ∼8-fold decrease in enthalpy compared to those for the melting of GST, providing key thermodynamic insights into the low-power switching of superlattice-based PCM. Nanocalorimetry measurements for Sb2Te3 alone demonstrate an intrinsic premelting similar to the unique phase transition of superlattices, thus revealing a critical role of the Sb2Te3 sublayer within our superlattices. These results advance our understanding of superlattices for energy-efficient data storage and computing.

Thermodynamic insight into the interaction mechanism of an ESIPT drug with a serum transport protein: Slower solvent-relaxation dynamics explored through wavelength-sensitive fluorescence behavior

Recently, 3,5-diiodosalicylic acid (3,5-DISA) has garnered enormous research attention owing to its wide-spread medicinal/biological applications, use as a model to study the role of halogen bonding in drug-protein interaction and so forth. However, the arena of the study of interaction of 3,5-DISA with relevant biological targets, particularly serum transport protein still starves for meticulous exploration of a number of fundamental aspects, such as, the thermodynamics and strength of binding, effect of drug binding on the native protein conformation and functionality, rotational and solvent-relaxation dynamics within the protein scaffolds etc. The present investigation endeavors to unveil these important aspects of 3,5-DISA:HSA interaction scenario. Our spectroscopic results demonstrate a remarkable modification of the excited-state intramolecular proton transfer (ESIPT) photophysics of 3,5-DISA upon interaction with HSA. A detailed isothermal titration calorimetry (ITC) study reveals that the interaction process is governed by favorable enthalpic (∆H0 < 0) and unfavorable entropic (T∆S0 < 0) contributions. The modulation of the hydration structure at the interfaces accompanying the binding phenomenon is also delineated in this context. Circular dichroism (CD) spectroscopy has been exploited to show the slight perturbation of the native protein conformation as a result of drug binding. In complementarity, the functionality of HSA (in terms of esterase-like activity) has also been shown to decrease with added 3,5-DISA. Our cumulative exploration of the wavelength-sensitive fluorescence parameters including red-edge excitation shift (REES) points out a remarkably slower rate of solvent-relaxation dynamics of the HSA-bound 3,5-DISA in the photoexcited state. The modification of the rotational-relaxation behavior of 3,5-DISA within the protein is also addressed and rationalized on the basis of the two-step and wobbling-in-cone model.

Molecular liquids versus ionic liquids: Thermodynamic insights into the interplay between inter-molecular and intra-molecular hydrogen bonding

Inter- and intra-molecular hydrogen bonding (HB) was studied in series of molecular and ionic liquids, containing a five-membered aliphatic ring (hydroxy-alkyl-pyrrolidines) and a five-membered aromatic ring (hydroxy-ethyl-imidazole), as well as in a corresponding ionic liquids, also containing a five-membered aromatic ring (hydroxy-alkyl-imidazolium) with the hydroxyl attached to the alkyl chain of the cation. To quantify these types of hydrogen bonds, we measured the enthalpies of vaporisation using a number of experimental methods, including thermogravimetric analysis, quartz crystal microbalance, and gas chromatographic method. The method of homomorphs was applied to quantify the strength of inter-molecular hydrogen bonding. The group-additivity based “centerpiece” method was used to quantify the intra-molecular HB strength in both molecular and in ionic liquids. Two new methods based on the experimental vaporisation enthalpies and a well-balanced thermodynamic equations were developed and applied to estimate the intra-molecular hydrogen bond strength, and results of the three methods agreed well. The interesting interplay between intra- and intermolecular hydrogen bonding was observed and discussed for each ionic liquid.

Kinetics and thermodynamic insights on extractive fermentation of fibrinolytic protease by Burkholderia cenocepacia strain OK1899609.1 using glycol-based eutectic solvents

The current investigation proposes extractive fermentation as a thermodynamically favorable process intensification method for the production and purification of fibrinolytic protease (FLP) from Burkholderia cenocepacia (OK1899609.1) using glycol-based deep eutectic solvents (GDES). Out of the six GDES examined, the recovery rate (97.4%) and the partition coefficient (3.8) were found to be high for GDES 5 (TAC: BC) and sodium sulfate. Brewery liquid waste (BLW) has been utilized as a low-cost carbon source for FLP production yielding 88.5%. Response surface methodology has been performed for optimization of all independent variables such as GDES (20% v/v), salt (15% w/v), BLW (3% v/v), and batch duration of 20 h. The GDES-rich FLP was back extracted and purified by anion exchange chromatography to produce ultrapure fibrinolytic protease (44.6 folds). Thus extractive fermentation of FLP was proved to be thermodynamically favorable and more exergonic results ΔG°E (−8.96 kJ/mol) ΔH°E (6.389 kJ/mol) and ΔS°E (28.70 J/mol). The resultant FLP was also thermostable, as shown by the higher-order activation energy (48.3 kJ/mol), deactivation constant (0.055 min-1), and half-life period (12.6 min). These findings indicate a potential scaling-up of the extractive fermentation from the shaker flask to a large scale with a high recovery of protease and related products.

Key element course-tracked copyrolysis of sewage sludge and biomass for resource recovery and pollution control through kinetic and thermodynamic insights

Ameliorating sewage sludge (SS) pyrolysis process with biomass increasingly becomes an effective strategy to utilize SS-entraining resources and depress pollutant evolution, while real-time track of SS and biomass copyrolysis as well associating thermochemical reactions in aspects of kinetics and thermodynamics is yet to be unveiled. Here a combinative thermogravimetry combined with Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry (TG-FTIR-GC/MS) pyrolysis system, lab-scale furnace and theoretical calculation were adopted to develop a key element course-tracked copyrolysis of SS and corn stalk (CS) for simultaneous accommodation of profitable products and derived pollutants. The formation of alkanes and alkene with small carbon number (below 4) was promoted during copyrolysis, while those with heavy carbons (over 5) were contributed by the inherent organic fraction of SS. The release of those nitrogen (N)-/sulfur-/chlorine-involving inorganic pollutants was depressed with the increase in the CS addition. The increased release of CO2 and H2O as well carboxylic volatiles with a high CS addition evidenced the promoted dehydroxylation and decarboxylation. Consequently, the speciation of N and phosphorus (P) and the bioavailability of toxic metals (TMs) were regulated with the increasing CS addition, that is, enhancements of proteins and protein-like N transformation to the other nitrogen species, P within orthophosphate diesters to orthophosphate monoesters, and TM reactivity-dependent bioavailability depression. A low addition (below 20 %) was prone to maintain a congruent mechanism, while the total Gibbs energy tended to decrease with an increasing addition and pyrolysis temperature, leading to a converged pressure-constant heat capacity (∼1430 J/K) at 700 °C. Those thermochemical reactions occurring over sewage sludge ash matrix were pivoted with biomass addition, which can be adopted as a useful strategy for an efficient, cleaner and sustainable mining of waste resources.

Insight on the sustainable design and multi-objective optimization for separating the ternary azeotropic mixture of toluene/n-butanol/water by natural decanting coupled with pressure swing distillation

The effective recovery of n-butanol (BuOH) and toluene from wastewater via sustainable separation process is critical to promote environmental protection and resource utilization. In this work, we propose a comprehensive methodology to develop a natural decanting coupled with pressure-swing distillation (NDPSD) for the azeotropic separation of BuOH/toluene/water system. Firstly, the thermodynamic topologic insights are employed to analyze the feasibility of the NDPSD. Secondly, conceptual design involving the understanding of mass balance lines, the liquid–liquid envelope, and distillation boundaries were applied to develop initial design of the NDPSD with two different separation sequences (i.e., configurations). Then, both initial designs are optimized to obtain the optimum column configurations via an improved non-sorting genetic algorithm, with the total capital and operating cost as dual objective function. Finally, both optimized schemes are heat-integrated for the purpose of energy conservation. The performance of all the developed configurations were examined using three indicators, i.e., economic, environmental, and energy efficiency, and our results revealed that the heat-integrated configuration B with separation sequence of water → BuOH → toluene provides the best economic, environmental, and thermodynamic efficiency.

Thermodynamic Insights into MgBr2-Mediated Glucose Interconversion to Fructose Undertaking Multiple Reaction Pathways by Applying the Macro- and Micro-Kinetic Principles

While many reports on the kinetics and mechanism of glucose isomerization to fructose via a chemical pathway have been published, thermodynamic insights into the interconversion reaction are rarely reported. Here, we report the temperature-dependent characteristics of the cation- and anion-mediated glucose conversion to fructose. The counter ions of MgBr2 enabled the reaction via different pathways in water; e.g., Mg2+ influenced the reaction by undertaking the 1,2-hydride shift mechanism and accounted for up to 50% of the conversion. However, the counter ion (Br–) promoted the conversion via the proton transfer mechanism, which contributed to the remaining 50%, based on the results of the isotopic labeling experiments. This selective transformation (32% wt fructose yield and 76% selectivity) aided by MgBr2 is attributed to the formation of a weak water shell around Mg2+ (due to a lower ratio of MgBr2 to water), which permitted the cation to expose its catalytic activity and affected the administering activity by Br–, which induces maximum side reactions. By applying the principles of transition-state Eyring and Marcus theories to the elementary steps involving a proton transfer and electron transfer, respectively, the temperature-dependent characteristics of the corresponding pathways were determined. The Eyring model exhibited a linear trend in the ln(k/T) vs 1/T plot with an activation energy barrier of 70.25 kJ/mol (comparable to the value of the collision-based Arrhenius model). The semi-classical Marcus model disclosed that the hydride shift is a normal electron transfer rate based on the localization of kET in the λ< -ΔGo >0 region.

Thermo-catalytic co-pyrolysis of palm kernel shell and plastic waste mixtures using bifunctional HZSM-5/limestone catalyst: Kinetic and thermodynamic insights

Kinetic and thermodynamic parameters of catalytic co-pyrolysis of palm kernel shell (PKS) and high-density polyethylene (HDPE) with three different catalysts (zeolite HZSM-5, limestone (LS) and bifunctional HZSM-5/LS) using thermogravimetric analyser via nitrogen environment were studied. The experiments were carried out at different heating rates ranging from 10 to 100 K/min within temperature range of 50–900 °C. Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and modified Distributed Activation Energy Model (DAEM) methods were employed in this current study. The average Ea for PKS, HDPE, PKS/HDPE (2:8) – HZSM-5, PKS/HDPE (2:8) – LS, PKS/HDPE (2:8) – HZSM-5/LS, PKS/HDPE (5:5) – HZSM-5/LS, PKS/HDPE (8:2) – HZSM-5/LS are 137.26–145.49, 247.73–250.45, 168.97–172.50, 149.74–152.79, 115.30–120.39, 124.36–129.41, 151.03–154.47 and 152.67–157.31 kJ mol−1, respectively. Among the different catalysts used, LS demonstrated the lowest average Ea (151.30–120.39 kJ mol−1) and ΔH (109.65–114.74 kJ mol−1). Positive values for ΔH and ΔG were found for the catalytic co-pyrolysis of PKS/HDPE mixtures which indicates the process is in endothermic reaction and possess non-spontaneous nature. The kinetic and thermodynamic analyses revealed the potential of PKS and HDPE as a potential feedstock for clean bioenergy production.

Thermodynamic insights into phase behavior a new aqueous two-phase system at different temperatures: Experimental equilibria, data correlation and modeling

In the current research, a novel aqueous ternary-two-phase system (ATPS) containing a deep eutectic solvent (DES formed by mixing choline chloride with polyethylene glycol 400) and the non-ionic surfactant Triton X-100 was designed. The phase behavior of this system including phase diagrams (binodal curves) and tie-line compositions was thermodynamically investigated at the temperature range of 298.15 to 316.15 K under atmospheric pressure. This system presented a DES-rich top phase and a surfactant-rich bottom phase. The plait point of binodal diagrams together with the tie-lines length (TLL) and the slope of tie-lines (STL) were determined at each of the operational temperatures. The influence of temperature on the binodal curves and the tie-lines was analyzed from which it was found that an increase in the temperature expands the two-phase region in the binodal curve as well as increases the length of the tie-lines. Moreover, the binodal curves data and the tie-line compositions were successfully correlated using a series of semi-empirical models with satisfactory results. Finally, the molar Gibbs energy, molar enthalpy and molar entropy of the cloud points of binodal curve were calculated and the results showed that the formation of the two-phase system is spontaneous and endothermic as well as the entropy is its driving force.

Co-assembly-mediated biosupramolecular catalysis: thermodynamic insights into nucleobase specific (oligo)nucleotide attachment and cleavage.

Gaining control over the stability and cleavage of phosphoester and phosphodiester remains a matter of interest for their application in biotechnology to oligonucleotide-based therapeutics. Herein, we report an efficient unactivated phosphoester hydrolysis (stable mono/di/tri/cyclic nucleotide to nucleoside conversion) via a biosupramolecular system comprising of a non-covalent complex of enzyme, alkaline phosphatase (ALP), and Zn(II)-metallosurfactant. We also demonstrate the nucleobase selective activation or inhibition of ALP-mediated oligonucleotide digestion process using that complex. The higher binding affinity of Zn(II)-containing headgroup with phosphate-containing substrate enhanced the effective substrate concentration surrounding the enzyme, which, in turn, results in a drastic decrease in the Michaelis constant (KM), along with an increase in the turnover (kcat). The catalytic activation or inhibition of nucleobase-specific oligonucleotide digestion depends on the hydration, localization of the substrates, and viscosity of the resultant co-assembly upon substrate binding with the enzyme-metallosurfactant complex. Additionally, through isothermal titration calorimetry experiment, we demonstrate enthalpy-entropy change during both the supramolecular binding of (oligo)nucleotides and simultaneous activation/inhibition in catalytic cleavage. Overall, it showed the possible modularity of Zn(II)-mediated biosupramolecular interaction, describing intrinsic thermodynamic aspects in developing complex biocatalytic circuits with nucleobase-specific oligonucleotides inputs, which are relevant in designing nucleic acid-based cargo for drug delivery and bioimaging.

Study on molecular mechanisms of CD4 dependency and independency of HIV-1 gp120.

Different HIV-1 strains have different antibody neutralization phenotypes (or CD4-dependencies). However, the molecular mechanisms underlying these differences remain to be elucidated. In this study, we constructed gp120 structural models from the CD4-dependent, neutralization-resistant JR-FL strain and the CD4-independent, neutralization-sensitive R2 strain and carried out several conventional molecular dynamics (MD) simulations and free energy landscape (FEL) constructions. Comparative analyses of the MD simulations and FELs indicated that R2 gp120 had higher global structural flexibility and greater conformational diversity than JR-FL gp120. This provides the preconditions for R2 gp120 to adopt a more open conformation than JR-FL gp120. Essential dynamics (ED) analysis showed that the collective motions of R2 gp120 tend towards an open state while those of JR-FL gp120 tend to retain a closed state. Based on conformational selection theory, R2 gp120's more readily sampled open state makes it more sensitive to neutralizing antibodies (or more CD4-independent) than JR-FL gp120, which may explain why the HIV-1 R2 and JR-FL strains show CD4-independent and -dependent phenotypes, respectively. Our study provides thermodynamic and kinetic insights into the CD4-dependent and -independent molecular mechanisms of HIV-1 gp120 and helps shed light on HIV-1 immune evasion.

Disulfide radical anion as a super-reductant in biology and photoredox chemistry.

Disulfides are involved in a broad range of radical-based synthetic organic and biochemical transformations. In particular, the reduction of a disulfide to the corresponding radical anion, followed by S-S bond cleavage to yield a thiyl radical and a thiolate anion plays critical roles in radical-based photoredox transformations and the disulfide radical anion in conjunction with a proton donor, mediates the enzymatic synthesis of deoxynucleotides from nucleotides within the active site of the enzyme, ribonucleotide reductase (RNR). To gain fundamental thermodynamic insight into these reactions, we have performed experimental measurements to furnish the transfer coefficient from which the standard E0(RSSR/RSSR˙-) reduction potential has been determined for a homologous series of disulfides. The electrochemical potentials are found to be strongly dependent on the structures and electronic properties of the substituents of the disulfides. In the case of cysteine, a standard potential of E0(RSSR/RSSR˙-) = -1.38 V vs. NHE is determined, making the disulfide radical anion of cysteine one of the most reducing cofactors in biology.

Investigation on energy-saving extractive distillation for recovering ethanol and 1,4-dioxane from wastewater

Energy-saving extractive distillation for separating ethanol and 1,4-dioxane from the industrial effluent is proposed. From the point of COSMO-SAC model and thermodynamic insights, appropriate entrainer is screened. Ethylene glycol (EG) is chosen in direct extractive distillation process. Subsequently, it is observed that increasing the pressure can make the azeotropic point of ethanol and 1,4-dioxane disappear. Thus, both EG and dimethyl sulfoxide (DMSO) are used as entrainers in indirect extractive distillation (IED) process. The entropy generation of different sections of each column is analyzed. And then, heat integration and heat pump technologies are used to reduce more energy consumption. The comparison results show that the total annual cost (TAC), total energy consumption, CO2 emissions and entropy generation of IED process with DMSO as entrainer (IED-DMSO) is smaller than those processes with EG as entrainer. The IED-DMSO process in combination with heat integration performs best, the TAC is reduced by 41.96%, energy consumption is reduced by 50.28%, CO2 emissions is decreased by 50.28% and entropy generation is decreased by 57.46% comparison with the IED-EG process.

Kinetic and Thermodynamic Insights into Advanced Energy Storage Mechanisms of Battery-Type Bimetallic Metal–Organic Frameworks

The engineering of high-performance battery-type electrode materials highly depends on the guidance from the combination of experimental analysis and theoretical simulation. Herein, the joint experimental–theoretical investigation provides a mechanistic explanation for the electrochemical performance enhancement in bimetallic metal–organic frameworks (MOFs). The superior CoNi-MOF in our study exhibits advanced electrochemical energy storage performance, achieving a high specific capacity of 382 C g–1 (1 A g–1), 2.0 and 1.4 times that of Co-MOF and Ni-MOF, respectively. Such a significant enhancement results from the surface-controlled reaction kinetics and the low onset potential contributed by the well-tuned electronic structures of bimetallic MOFs. Our study opens up new perspectives for understanding the advantages of mixed metal sites in MOFs for electrochemical energy storage.

Molecular and thermodynamic insights into interfacial interactions between collagen and cellulose investigated by molecular dynamics simulation and umbrella sampling.

Cellulose/collagen composites have been widely used in biomedicine and tissue engineering. Interfacial interactions are crucial in determining the final properties of cellulose/collagen composite. Molecular dynamics simulations were carried out to gain insights into the interactions between cellulose and collagen. It has been found that the structure of collagen remained intact during adsorption. The results derived from umbrella sampling showed that (110) and ([Formula: see text]) faces exhibited the strongest affinity with collagen (100) face came the second and (010) the last, which could be attributed to the surface roughness and hydrogen-bonding linkers involved water molecules. Cellulose planes with flat surfaces and the capability to form hydrogen-bonding linkers produce stronger affinity with collagen. The occupancy of hydrogen bonds formed between cellulose and collagen was low and not significantly contributive to the binding affinity. These findings provided insights into the interactions between cellulose and collagen at the molecular level, which may guide the design and fabrication of cellulose/collagen composites.