Mean Square Displacement Research Articles

In silico targeting CYP51 of Naegleria fowleri using bioactive compounds from Indonesian plants

Context: Given the elusive nature of Primary Amoebic Meningoencephalitis (PAM), caused by Naegleria fowleri, early detection is vital, yet challenging due to limited clinical indicators. This research leverages Indonesia's rich biodiversity to explore novel sources of traditional medicine. Aims: To evaluate the potential compounds from Indonesian plants that possess antiamoebic and antifungal properties for inhibiting the N. fowleri CYP51 protein, crucial for cell integrity. Methods: Initially, 92 compounds were screened, and six were shortlisted following ADMETox evaluation. Subsequent steps encompassed QSAR analysis, molecular docking, and molecular dynamics simulations. Results: The QSAR analysis verified the activity potential of these six compounds, progressing them to molecular docking analysis. Among these, curcumenol from Curcuma longa emerged as a promising contender, displaying the lowest binding affinity at -9.2 kcal/mol, indicative of superior binding compared to other ligands. Molecular dynamics simulations underscored the stability of all compounds, with root mean square fluctuation (RMSF) values within 1-3 Å. Conclusions: Consequently, employing a comprehensive approach spanning ADMETox, QSAR, molecular docking, and dynamics simulations, curcumenol emerged as the prime candidate for inhibiting the N. fowleri CYP51 protein, suggesting its potential as a PAM therapeutic agent.

Masoprocol: a promising candidate for targeting insulin resistance by inhibiting resistin with optimal druglikeness Potentials: an in silico approach

Resistin is a cysteine-rich secretory hormone that induces resistance to insulin, and its elevated expression is correlated with the onset of diabetes and several related metabolic disorders. Resistin performs its inhibitory role by connecting three identical subunits through Cys22-based disulfide linkages. The necessity to inhibit the formation of resistin trimer is one of the essential means to prevent the aggravation of diabetes mellitus type 2, obesity, and atherosclerosis. This study was conducted to screen the clinically approved drugs to find the most potent one to inhibit resistin with the best pharmacokinetics and drug-likeness properties. A total of 4654 clinically approved drugs were docked against the Cys22 residue of resistin. The top ten drugs with the highest high-precision (XP) docking scores were selected. Ioversol and masoprocol showed the highest XP docking and Molecular Mechanics-Generalized Born Surface Area (MMGBSA) scores, respectively, with double hydrogen bonding with the targeted Cys22. Molecular dynamics (MD) simulations showed that the masoprocol-resistin complex exhibited lower root mean square deviation (RMSD), radius of gyration, and root mean square fluctuation (RMSF) values than those observed in the ioversol-resistin complex. Both drugs induced drastic conformational changes in resistin monomer interactions. However, ioversol did not prove satisfying drug-likeness properties, while masoprocol showed the most favourable pharmacokinetic and drug-likeness properties. This study has demonstrated that masoprocol offers a novel inhibitory effect on resistin with the highest ligand affinity, making it a promising drug for combating insulin resistance. Communicated by Ramaswamy H. Sarma

Effect of Fluctuations in Complex Plasmas on the Dynamics of Charged Dust Grains

The effect of random forces, which are caused by fluctuations in a complex plasma, on the dynamics of charged dust grains is studied. Analytical dependences are obtained for the kinetic energy, the autocorrelation functions of velocities, the mass transfer functions, and the mean-square average displacements of the grains in the case of a grain moving under the effect of two random forces. A method is proposed for accounting for more than two random forces of different nature. The possibility is discussed of simulating the motion of dust grains in complex plasma by the Langevin equations with a temperature that is not equal to the temperature of the surrounding gas.

Anomalous diffusion, non-Gaussianity, and nonergodicity for subordinated fractional Brownian motion with a drift.

The stochastic motion of a particle with long-range correlated increments (the moving phase) which is intermittently interrupted by immobilizations (the trapping phase) in a disordered medium is considered in the presence of an external drift. In particular, we consider trapping events whose times follow a scale-free distribution with diverging mean trapping time. We construct this process in terms of fractional Brownian motion with constant forcing in which the trapping effect is introduced by the subordination technique, connecting "operational time" with observable "real time." We derive the statistical properties of this process such as non-Gaussianity and nonergodicity, for both ensemble and single-trajectory (time) averages. We demonstrate nice agreement with extensive simulations for the probability density function, skewness, kurtosis, as well as ensemble and time-averaged mean-squared displacements. We place a specific emphasis on the comparisons between the cases with and without drift.

Molecular Dynamics Study of Peptide in Water at Different Temperature

Molecular dynamics approach has been carried out to study the structural properties of peptide to estimate the self-diffusion coefficients of water at different temperatures 290 K, 300 K, and 310 K respectively. The energy profiles show the stability of system which ensures a well-balanced molecular structure of the system. The radial distribution functions (RDFs) of the solvent-solvent, solute-solute, and solute-solvent show the distribution of system within the required references. The self-diffusion coefficients of water have been determined using respective mean square displacement (MSD) curves through the Einstein’s relation. The self-diffusion coefficients of water at different temperatures are 0.44 ×10-5 cm2s-1, 0.48 ×10-5 cm2s-1, and 0.50 ×10-5 cm2s-1 respectively. Calculations show that the MSD of water throughout the system is increasing on increasing temperature. The results are also valid with the theoretical as well as available experimental data.

Molecular simulation of CO2 capturing by dual functionalized phosphonium-based amino acid ionic liquids

Various solvents have been proposed considering the importance of CO2 gas removal from the environment. Over the past few decades, ionic liquids (ILs) have elicited much attention due to their unique properties. In this regard, capturing the CO2 gas by phosphonium-based amino acid ILs (AAILs) was studied by molecular dynamics (MD) simulation. The effect of cation functionalization was studied. The anion was glycinate, [GLY]-, and the cation was tetrabutylphosphonium, [P4444]+, functionalized by different functional groups including acidic (−COOH), alcoholic (−OH), amine (−ΝΗ2), and ether (−OCH3). Density, absorption energy, radial distribution function (RDF), mean square displacement (MSD), concentration profile, free volume, and fractional free volume were under investigation. According to density values calculated from MD simulation, functionalized AAIL with a carboxylic acid group ([P4444COOH][Gly]) is the most concentrated system with the maximum interaction energy between AAIL and the trapped CO2 gas equal to − 1.917 kcal.mol−1. In addition, the lowest volume variation was observed through this physical absorption. RDF analysis reveals that anion interaction with CO2 gas is the most considerable one in the case of [P4444COOH][Gly] AAIL. The CO2 uptake is 2:1 for functionalized AAILs that shows cation functionalization improves CO2 gas absorption capacity; each mole of [P4444COOH][Gly] AAIL is capable of surrounding 2.11 mol of CO2. Finally, the gas diffusion coefficient is the lowest one in [P4444COOH][Gly] AAIL as the solvent-free volume is observed as a continuous channel to trap CO2 gas with the lowest gas diffusivity parameter.

Molecular simulation on the mechanical and thermal properties of modified insulating paper cellulose doped with trapezoidal polyphenylsesquisiloxane at different temperature

AbstractWith the further development of the transmission and distribution network, the requirements for the insulating system of power equipment are further deepened. As one of the important factors, insulating paper is of great value to improve its performance. The pure cellulose model and trapezoidal polyphenylsesquisiloxane (T‐PPSQ) composite model are established to analyze the mechanical and thermal properties of insulating paper cellulose. The effects of T‐PPSQ doping at different temperature on properties of cellulose are investigated by comparing the radial distribution function, mechanical parameters, glass transition temperature, mean square displacement (MSD), and free volume fraction (FVF) through molecular dynamics method. The results show that T‐PPSQ can improve the ability of cellulose to resist shear stress at different temperatures, showing good mechanical properties. When the temperature is 423 K, the mechanical performance parameters elastic modulus, bulk modulus and shear modulus can be increased by 47.2%, 18.2%, and 38.56% at most. The glass transition temperature of the insulating paper cellulose with T‐PPSQ increases by 64 K, the MSD and the FVF all decrease at different temperature which demonstrated it has improved thermal stability. The research in this paper is of great significance for improving the life of the insulating system of power equipment.

Potential Effect of Baobab's Polyphenols as Antihyperlipidemic Agents: In Silico Study.

Adansonia digitata L. is an African tree commonly called baobab. This tree is effectively used in traditional medicine to treat cardiovascular disorders. Hyperlipidemia is a well-known cardiovascular risk factor associated with the increased incidence of mortality worldwide. This study aimed to demonstrate the mechanism of baobab polyphenols in the activities of hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and pancreatic lipase as lipid metabolic enzymes. Molecular docking and an incentive for drug design showed that all the polyphenols in baobab bound to the proteins with higher affinity and a lower binding energy compared with simvastatin as the positive control (ΔG: from -5.5 kcal/mol to -6.5 kcal/mol). The same polyphenols exhibited a considerable binding affinity to pancreatic lipase (ΔG: from -7.5 kcal/mol to -9.8 kcal/mol) in comparison with the control and HMG-CoA reductase. Quercetin showed the best docking score from the selected Baobab polyphenols (ΔG = -9.8 kcal/mol). The root mean square deviation (RMSD) results indicated that stable epicatechin and quercetin complexes were demonstrated with HMG-CoA reductase, and other less stable complexes were developed using rutin and chlorogenic acid. Moreover, the analysis of the root mean square fluctuation (RMSF) simulation results was consistent with that of the RMSD. The RMSF value for all the baobab polyphenols, including the crystal control ligand, was kept between 0.80 and 8.00 Å, similarly to simvastatin, and less than 4.8 Å for pancreatic lipase. Chlorogenic acid, quercetin, epicatechin, and rutin had negative ΔG binding scores from highest to lowest. The same ligands displayed more negative ΔG binding scores than those observed in HMG-CoA reductase and crystal control ligand (methoxyundecyl phosphinic acid) in their simulation with pancreatic lipase. In conclusion, baobab polyphenols interact with HMG-CoA reductase and pancreatic lipase to inhibit their substrate binding and block their activity.

Differences in the Effect of Water on Deep Eutectic Solvents Based on Choline Chloride/Lauric Acid and Choline Chloride/Myristic Acid: Molecular Dynamics Simulations at Three Different Temperatures

AbstractApplication of deep eutectic solvents based on fatty acids in different fields of biological and therapeutic sciences, such as novel hydrophobic Volatile organic compounds (VOC) absorbents, etc. However, industries need knowledge and precise investigation of the structural and dynamic properties of these solvents. In this work, the effect of water on the dynamical and structural properties of the binary mixtures of choline chloride+two types of Fatty acids; Lauric (LUA), and Myristic (MRA) acids have been investigated at T=343 K, 443 K, 543 K. An additional NPT production run of 30 ns was considered for the binary mixtures. In order to understand the effective interactions in the formation of the eutectic mixture based on fatty acid and choline chloride, the combined distribution functions (CDFs) involving the radial distribution functions (RDFs) and the angular distribution functions (ADFs), the hydrogen‐bonding network, and spatial distribution functions (SDFs), interaction energies between species were calculated for the binary mixtures. Also, the dynamical properties of DESs have been evaluated by calculating the mean‐square displacement (MSD), the velocity autocorrelation function (VACF) of the centers of mass of the molecules, and the self‐diffusion coefficient.

Understanding the swap Monte Carlo algorithm in a size-polydisperse model glassformer.

The dynamics of a polydisperse model glassformer are investigated by augmenting molecular dynamics (MD) simulation with swap Monte Carlo (SMC). Three variants of the SMC algorithm are analyzed with regard to convergence and performance. We elucidate the microscopic mechanism responsible for the drastic speed-up of structural relaxation at low temperature. It manifests in a stepwise increase of the mean-squared displacement when the timescale between the application of swap sweeps is significantly larger than a characteristic microscopic timescale. Compared to Newtonian dynamics, with the hybrid MD-SMC dynamics the glass transition shifts to a lower temperature and a different temperature dependence of the localization length is found.

Identification of natural potent inhibitors against Mycobacterium tuberculosis isocitrate lyase: an in silico study.

Tuberculosis (TB) is a global burden to humanity due to its adverse effects on health and society since time is not clearly defined. The existence of drug-resistant strains and the potential threat posed by latent tuberculosis act as strong impetuses for developing novel anti-tuberculosis drugs. In this study, various flavonoids were tested against the Mycobacterium tuberculosis (Mtb) Isocitrate Lyase (ICL), which has been identified as an authorised therapeutic target for treating Mtb infection. Using in silico drug discovery approach, a library of 241 flavonoid compounds was virtually screened against the binding pocket of the crystalline ligand, the VGX inhibitor, in the Mtb ICL protein. As a result, the top four flavonoids were selected based on binding score and were further considered for redocking and intermolecular contact profiling analysis. The global and local fluctuations in the protein and ligand structure were analysed using their root mean square deviation (RMSD) and root mean square fluctuation (RMSF) values obtained from the GROMACS generated 100ns molecular dynamics (MD) simulation trajectories. The end-state binding free energy was also calculated using the MMPBSA approach for all the respective docked complexes. All four selected compounds exhibited considerable stability and affinity compared to control ligands, i.e. VGX inhibitor; however, Vaccarin showed the highest stability and affinity against the Mtb ICL protein active site, followed by the Genistin, Glabridin, and Corylin. Therefore, this study recommends selected flavonoids for in vitro and in vivo experimental studies to check their potency and efficacy against Mtb.

Time-fractional Caputo derivative versus other integrodifferential operators in generalized Fokker-Planck and generalized Langevin equations.

Fractional diffusion and Fokker-Planck equationsare widely used tools to describe anomalous diffusion in a large variety of complex systems. The equivalent formulations in terms of Caputo or Riemann-Liouville fractional derivatives can be derived as continuum limits of continuous-time random walks and are associated with the Mittag-Leffler relaxation of Fourier modes, interpolating between a short-time stretched exponential and a long-time inverse power-law scaling. More recently, a number of other integrodifferential operators have been proposed, including the Caputo-Fabrizio and Atangana-Baleanu forms. Moreover, the conformable derivative has been introduced. We study here the dynamics of the associated generalized Fokker-Planck equationsfrom the perspective of the moments, the time-averaged mean-squared displacements, and the autocovariance functions. We also study generalized Langevin equationsbased on these generalized operators. The differences between the Fokker-Planck and Langevin equations with different integrodifferential operators are discussed and compared with the dynamic behavior of established models of scaled Brownian motion and fractional Brownian motion. We demonstrate that the integrodifferential operators with exponential and Mittag-Leffler kernels are not suitable to be introduced to Fokker-Planck and Langevin equationsfor the physically relevant diffusion scenarios discussed in our paper. The conformable and Caputo Langevin equationsare unveiled to share similar properties with scaled and fractional Brownian motion, respectively.

Molecular dynamics investigation of thermo-physical properties of molten salt with nanoparticles for solar energy application

Molten salt is an important medium for thermal storage, which is widely used in concentrating solar power plants. The addition of nanomaterials becomes an effective way to overcome the unsatisfactory thermo-physical properties of pure molten salt. In the present study, molecular dynamics simulations are performed to investigate the influence of SiO2 nanoparticle on the thermo-physical properties of solar salt. Two kinds of models of solar salt nanofluids, i.e., different sizes of boxes with the same size of nanoparticles and the same size of boxes with different sizes of nanoparticles, at the mass fractions of nanoparticles of 1%, 2%, 3%, 4%, 5%, and 6% are built to analyze the size effects on the simulation results. The effects of SiO2 nanoparticles on the specific heat capacity, viscosity and thermal conductivity of the composited thermal energy storage (CTES) materials are studied extensively. The microscopic mechanism of the thermo-physical properties variation is revealed by calculating the mean square displacement (MSD), diffusion coefficient, Radial distribution function (RDF) and energy of systems. It is proved that the calculations of shear viscosity, specific heat capacity and MSD do not have size effect. An enhancement as large as 2.05% in the specific heat capacity of the CTES materials has been found with 2 wt% addition of nanoparticles. The presence of the compressed layer on the surface of the nanoparticles might be responsible for the enhancement of the specific heat capacity according to the calculation of RDF. It is also found that with the increase of mass fraction of nanoparticles, the viscosity of the CTES materials increases due to the enhancement of interaction between ions in the base fluid. Therefore, in order to avoid the negative effects caused by excessive viscosity of solar salt in thermal energy storage system, it is suggested to consider the appropriate amount of nanoparticles. The addition of SiO2 nanoparticles enhances the thermal conductivity of the CTES materials with the increase of mass fraction of nanoparticles. It is demonstrated that the enhancement of ion collision frequency in the base fluid is the main factor for the enhancement of thermal conductivity by the addition of SiO2 nanoparticles.

The LDL receptor is regulated by membrane cholesterol as revealed by fluorescence fluctuation analysis

Membrane cholesterol-rich domains have been shown to be important for regulating a range of membrane protein activities. Low-density lipoprotein receptor (LDLR)-mediated internalization of cholesterol-rich LDL particles is tightly regulated by feedback mechanisms involving intracellular sterol sensors. Since LDLR plays a role in maintaining cellular cholesterol homeostasis, we explore the role that membrane domains may have in regulating LDLR activity. We expressed a fluorescent LDLR-mEGFP construct in HEK293T cells and imaged the unligated receptor or bound to an LDL/DiI fluorescent ligand using total internal reflection fluorescence microscopy. We studied the receptor’s spatiotemporal dynamics using fluorescence fluctuation analysis methods. Image cross correlation spectroscopy reveals a lower LDL-to-LDLR binding fraction when membrane cholesterol concentrations are augmented using cholesterol esterase, and a higher binding fraction when the cells are treated with methyl-β-cyclodextrin) to lower membrane cholesterol. This suggests that LDLR’s ability to metabolize LDL particles is negatively correlated to membrane cholesterol concentrations. We then tested if a change in activity is accompanied by a change in membrane localization. Image mean-square displacement analysis reveals that unligated LDLR-mEGFP and ligated LDLR-mEGFP/LDL-DiI constructs are transiently confined on the cell membrane, and the size of their confinement domains increases with augmented cholesterol concentrations. Receptor diffusion within the domains and their domain-escape probabilities decrease upon treatment with methyl-β-cyclodextrin, consistent with a change in receptor populations to more confined domains, likely clathrin-coated pits. We propose a feedback model to account for regulation of LDLR within the cell membrane: when membrane cholesterol concentrations are high, LDLR is sequestered in cholesterol-rich domains. These LDLR populations are attenuated in their efficacy to bind and internalize LDL. However, when membrane cholesterol levels drop, LDL has a higher binding affinity to its receptor and the LDLR transits to nascent clathrin-coated domains, where it diffuses at a slower rate while awaiting internalization.

Local Einstein relation for fractals

We study single random walks and the electrical resistance for fractals obtained as the limit of a sequence of periodic structures. In the long-scale regime, power laws describe both the mean-square displacement of a random walk as a function of time and the electrical resistance as a function of length. We show that the corresponding power-law exponents satisfy the Einstein relation. For shorter scales, where these exponents depend on length, we find how the Einstein relation can be generalized to hold locally. All these findings were analytically derived and confirmed by numerical simulations.

Molecular dynamics simulations on the water diffusion in modified silica membrane with TiO2

Today, the use of modified silica membranes for the osmosis process has received attention. Titanium dioxide (TiO2) has a significant application in increasing the efficiency of osmotic membranes due to its hydrophilic, antibacterial, and nontoxic properties. A molecular dynamics (MD) simulations approach is applied to theoretical insights into the effect of concentration of TiO2 in silica membrane on the water molecules diffusion. The diffusion coefficient of water in modified forward osmosis silica membranes with 10−6, 10−4, 10−2, 0, 1, and 100-mole ratios of TiO2 has been calculated from the mean square displacement (MSD) of H2O molecules and obtained (0.015,1.952,2.570,2.810,0.078and0.086)×10−9m2s, respectively. The results of our simulations are in excellent agreement with the experimental results and also can be compared to the diffusion coefficient of water in Polyamide (PA) membrane as one of the most important membranes at reverse osmosis for water desalination about 0.600×10−9m2s.

Ion clustering, aggregation and diffusion in amide based deep eutectic solvents: A microstructural investigation using various NMR spectroscopic techniques and molecular dynamics simulation

A thorough understanding of the structure and dynamics of deep eutectic solvents (DESs) is necessary to optimize the uses of this new class of solvents for many potential applications. Herein, we have studied ion clustering, aggregation and diffusion mechanism in DESs composed of acetamide and sodium/potassium thiocyanate using 1D NMR, pulsed field gradient stimulated echo (PFGSE) NMR and 2D nuclear Overhauser effect spectroscopy (2D NOESY) techniques, and molecular dynamics simulation. We have varied the fraction of salts to investigate the composition dependent microscopic structural insight. A great enhancement in diffusion coefficient (D) of acetamide with increasing the fraction of KSCN (fKSCN) has been observed in PFGSE measurements. The experimental diffusion activation energy (Ea) decreases significantly with increasing fKSCN, which is in excellent agreement with the Ea values obtained from simulated mean squared displacements (MSD). The calculated radial distribution functions (RDF) indicate that the Na+ ions strongly coordinate with acetamide molecules and form ion-clusters and aggregated structures in the medium. However, as Na+ ions are gradually replaced by K+ ions, ion-clustering and aggregation decrease due to relatively weak coordination ability of larger cation, which supports the enhancement of experimental D with increasing fKSCN. In the 2D NOESY study, the intensity of the cross peaks between methyl and amide protons of acetamide decreases relative to the diagonal peak intensity as the fKSCN increases in the medium. This study indicates that the extent of intermolecular NOE reduces as the structural flexibility increases due to less efficient ion-clustering with increasing K+ ion concentration, thus strongly corroborates the results from PFGSE experiment and simulation. Furthermore, 1D and 2D NMR data exhibit an intramolecular chemical exchange between two amide protons in acetamide, the extent of which increases with increasing temperature as well as fKSCN in the DES system. The present study provides a multifaceted picture of composition-dependent distinct microstructures in DES.

Pharmacophore based virtual screening for identification of effective inhibitors to combat HPV 16 E6 driven cervical cancer

Targeting HPV16 E6 has emerged as an effective drug target for the treatment/management of cervical cancer. We utilized pharmacophore-based virtual screening, molecular docking, absorption, distribution, metabolism and excretion (ADME) prediction, and molecular dynamics simulation approach for identifying potential inhibitors of HPV16 E6. Initially, we generated a ligand-based pharmacophore model based on the features of four known HPV16 E6 inhibitors (CA24, CA25, CA26, and CA27) via the PHASE module implanted in the Schrödinger suite. We constructed four-point pharmacophore features viz., three hydrogen bond acceptors (A) and one aromatic ring (R). The common pharmacophore feature further employed as a query for virtual screening against the ASINEX database via Schrödinger suite. The pharmacophore-based virtual screening filtered out top 2000 hits, based on the fitness score. We then applied the high throughput virtual screening (HTVS), standard precision (SP) and extra precision (XP). 1000 compounds were obtained from HTVS docking. Based on the glide score, they were further filtered to 500 hits by employing docking in standard precision mode. Finally, the best four hits and a negative molecule were identified using docking in XP mode. The four lead compounds and a negative molecule were then further subjected to ADME profile prediction by engaging Qikprop module. The ADME properties of the four lead molecules indicate good pharmacokinetic (PK) properties rather than the negative molecule. The binding stability of the HPV16 E6-hit complexes were investigated at a different time scale (100 ns) by using the desmond package and the results were examined using Root Mean Square Deviation (RMSD) and Root Mean Square Fluctuation (RMSF) and it revealed the stability of the protein-ligand complex throughout the simulation. Key residues, CYS 51 and GLN 107, also play a crucial role in enhancing the stability of the protein-ligand complex during the simulation. Furthermore, the binding free energy of the HPV16 E6-leads complexes was analyzed by prime which revealed that the ΔGbind coulomb and ΔGbind vdW interactions are crucially contributes to the binding affinity. In order to validate the computational findings, the efficacy of benzoimidazole and benzotriazole were ascertained for regulating ME180 cervical cancer cell survival, migration and ability to release MMP-2.

Evaluating the interfacial properties between crumb rubber modified asphalt and aggregates using molecular dynamics simulation methods

In the present study, the molecular dynamics (MD) simulation methods were used to investigate the interfacial properties of crumb rubber modified asphalt (CRMA)-aggregates considering the effects of crumb rubber (CR) degradation behavior and moisture. The interface models with different CR degradation degrees were then constructed. The interfacial adhesion properties between CRMA and aggregates were discussed by the interaction energy and work of adhesion; the agglomeration characteristics of CRMA on aggregates surface were evaluated by the radial distribution function (RDF); the diffusion behaviors of CRMA on aggregates surfaces were investigated using the mean square displacements (MSD); the asphalt adhesion strength test was performed to further verify the reliability of the simulation results. The results showed that the incorporation of CR into asphalt could significantly improve the adhesion and moisture damage resistance of the asphalt mixtures, while the CR degradation would slightly decrease these properties. The results of asphalt adhesion strength test exhibited similar trends with those of the work of adhesion, indicating that the simulation possessed a certain rationality. The RDF curves showed that the intrusion of water enlarged the distance between the polar components and aggregates, whereas the CR molecules displayed satisfactory agglomeration properties. Furthermore, the addition of CR weakened the mobility of asphalt on aggregates surface. This was mainly attributed to the poor mobility of the CR and its limitation on the mobility of the constituent components of asphalt. However, these problems would be alleviated as the CR degradation.

Interfacial interaction behavior of recycled asphalt pavement: Molecular dynamics simulation

Recycling waste asphalt mixture (WAM) to prepare recycled asphalt pavement (RAP) is an important measure to handle road construction waste. Asphalt-aggregate interface (AAI) and matrix-aged asphalt interface (MAI), as weak interfaces in RAP, interface interaction behavior directly affects the road performance of RAP. In this paper, molecular models of asphalt and aggregate were constructed. Molecular dynamics simulation was used to analyze and evaluate the interaction behavior of the AAI and the MAI in RAP. The mean square displacement (MSD), relative concentration function (RCP), and radial distribution function (RDF) were used to quantitatively analyse the interface interaction behavior. The research results are as follows: For the AAI, the temperature, the aging level of asphalt, and chemical composition of aggregates will affect the interaction behavior of the AAI. Increasing temperature accelerates the diffusion of asphalt on the surface of aggregate. However, the increase of the aging level of asphalt and the alkalinity of aggregate will decrease the interaction rate of asphalt on the surface of aggregate. For the MAI, the temperature and the ratio of filler-asphalt (RFA) significantly affect the interaction behavior of the MAI. The molecular diffusion rate of matrix asphalt and aged asphalt increases significantly with the increasing temperature. The addition of filler will decrease the diffusion rate of asphalt, and the diffusion rate decreases with the increase of RFA. This article comprehensively and systematically studies and evaluates the effect of various factors on the interface interaction behavior. The results provide guidance for improving the adhesion ability of AAI and enhancing the degree of incorporation of MAI.