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Underwater adhesives are critical for many applications, including marine coatings, sealants, and medical devices. Research on natural underwater adhesives has shown that L-3,4-dihydroxyphenylalanine (DOPA) and amyloid nanostructures are vital to their adhesive abilities. The fusion of DOPA-containing chains and amyloid-forming peptides creates a new space for designing underwater adhesives capable of multi-surface adhesion. One critical question for this design is the interplay between the DOPA and amyloid-forming peptide regions. Here we investigate the effect of the sequence pattern of DOPA-containing chains on the aggregation conformation of conjugates. Discontinuous molecular dynamics simulations were performed for fourteen DOPA-amyloid conjugates with different sequence patterns along the DOPA-containing portion. The amyloid-forming portion is represented by KLVFFAE from the Aβ42 peptide. The structural properties of the DOPA-amyloid conjugates are characterised by the percentages of ordered secondary structures and residue-residue contact maps. The results showed that certain patterns of DOPA and glycine in the DOPA-containing tail allowed the KLVFFAE portions of the conjugates to form distinct ordered β-sheets, and the DOPA-containing portion and the KLVFFAE portion of the conjugates to remain separated both within the same chain and amongst different chains. Among the designs, the most promising sequences are KLVFFAE-G-YYGYYGYY (where Y represents DOPA) and KLVFFAE-G-YYYYGGGG. [ABSTRACT FROM AUTHOR]

In this work, we investigated the effects of carboxybetaine (CB) and (ethylene glycol)4 (EG4) solutes on chymotrypsin inhibitor 2 (CI2) as a model protein using molecular dynamics simulations. The properties studied include the radial distribution functions of these two solutes to the C-α atoms of the 64 residues of CI2, the average numbers of solute-protein and water-protein hydrogen bonds, the root mean square deviation of the C-α atoms of the protein, and the solvent access surface area of the protein. Results show that these two solutes share some common properties while have some different effects on the protein. Both of these two solutes do not accumulate preferentially near the protein and CI2 is folded with either of them. However, CI2 is found to have properties in the CB solution closer to bulk water, whereas CI2 shows reduced flexibility and decreased SASA of the hydrophobic domain in the EG4 solution. Although the protein is folded with both CB and EG4, superhydrophilic CB has a minimal effect on the protein due to the shared zwitterionic nature of both CB and protein whereas amphiphilic EG4 alters the properties of the protein via hydrophobic interactions. [ABSTRACT FROM AUTHOR]

Sodium- (Na+) and potassium- (K+) ion batteries are cost-effective alternatives to lithium-ion (Li+) batteries due to the abundant sodium and potassium resources. Solid polymer electrolytes (SPEs) are essential for safer and more efficient Na+ and K+ batteries because they often exhibit low ionic conductivity at room temperature. While zwitterionic (ZW) materials enhance Li+ battery conductivity, their potential for Na+ and K+ transport in batteries remains unexplored. In this study, we investigated the effect of three ZW molecules (ChoPO4, i.e., 2-methacryloyloxyethyl phosphorylcholine, ImSO3, i.e., sulfobetaine ethylimidazole, and ImCO2, i.e., carboxybetaine ethylimidazole) on the dissociation of Na+ and K+ coordination with ethylene oxide (EO) chains in EO-based electrolytes through molecular dynamics simulations. Our results showed that ChoPO4 possessed the highest cation–EO10 dissociation ability, while ImSO3 exhibited the lowest. Such dissociation ability correlated with the cation–ZW molecule coordination strength: ChoPO4 and ImSO3 showed the strongest and the weakest coordination with cations. However, the cation–ZW molecule coordination could slow the cationic diffusion. The competition of these effects resulted in accelerating or decelerating cationic diffusion. Our simulated results showed that ImCO2 enhanced Na+ diffusion by 20%, while ChoPO4 and ImSO3 led to a 10% reduction. For K+, ChoPO4 reduced its diffusion by 40%, while ImCO2 and ImSO3 caused a similar decrease of 15%. These findings suggest that the ZW structure and the cationic size play an important role in the ionic dissociation effect of ZW materials. [ABSTRACT FROM AUTHOR]

Zwitterionic materials have showntheir excellent performance inmany biological and chemical applications. Zwitterionic materialspossess moieties that own both cationic and anionic groups. The associationsamong zwitterionic moieties through electrostatic interactions playan important role in properties of zwitterionic materials. However,the relationship between the molecular structures and associationsof zwitterionic moieties are still not well understood. This workcompared thermal- and salt-responsive behaviors of sulfobetaine andcarboxybetaine polymers by examining their rheological propertiesas a function of temperature and their hydrodynamic sizes as a functionof salt concentration. Results showed that carboxybetaine polymersdo not exhibit stimuli responses as expected from the antipolyelectrolytebehavior of zwitterionic polymers as observed in sulfobetaine polymers.We studied and compared the associations among zwitterionic moietiesin these two zwitterionic polymers using molecular dynamic simulations.Simulation results show that the charge-density difference betweencationic and anionic groups determines the associations among zwitterionicmoieties, which are responsible for different stimuli responses ofcarboxybetaine and sulfobetaine polymers. [ABSTRACT FROM AUTHOR]

Zwitterionic carboxybetaines (CBs) are ubiquitous innature andconsidered promising materials for biological and chemical applications.A thorough understanding of the effect of carbon spacer length (CSL)on molecular properties is important. In this work, using moleculardynamics simulation and quantum chemical calculation, we investigatedthe effect of CSL on the molecular properties of CB molecules. Thehydration number, structure, and dynamics of carboxylic and trimethylammonium groups were investigated and found to present different behaviorsin regards to the variation of CSL. The simulation results with partialcharges developed from quantum chemical calculations were comparedwith those with partial charges from the OPLS all atom (OPLSAA) forcefield. The hydration free energy of CB molecules and CB–Na+association was also studied as a function of CSL. [ABSTRACT FROM AUTHOR]

The differences in structural change between Au225 and Au369 clusters with their (111) facets supported on MgO(100) surfaces at 5 K are studied by using molecular-dynamics simulations with the atomic interchange potentials of the Au/MgO interface. The parameters are obtained from the ab initio energies using the Chen-Möbius inversion method. Analyses of the pair distribution functions show that the two Au clusters use different deformation processes to adjust the distances between the interface atoms, owing to the misfit between the atom distances among the clusters and the substrates. The local structural changes are identified by atomic density profiles. [ABSTRACT FROM AUTHOR]

In this work, molecular dynamics simulations were performed to study a carboxybetaine methacrylate (CBMA) hydrogel under various swelling states. The water content in this study ranged from 28% to 91% of the total weight of the hydrogel. Three transitions of the CBMA hydrogel were observed as the water content increased. The first transition occurs when the water content increases from 33% to 37%. The observed kink in the self-diffusion coefficient of water indicates that the hydration of the polymer network of the hydrogel is saturated; the further added water is in a less confined state. The second transition was found to be related to the physical cross-links of the polymer network. As the water content rises to above 62%, the lifetime of the physical cross-links decreases significantly. This abrupt change in the lifetime indicates that the transition represents the equilibrium swelling state of the hydrogel. Finally, the third transition was observed when the water content goes above 81%. The significant increases in the bond and angle energies of the polymer network indicate that the hydrogel reaches its upper limit swelling state at this transition. These results are comparable to previously published experimental studies of similar zwitterionic hydrogels. [ABSTRACT FROM AUTHOR]

Using molecular dynamics simulations, we investigated the associations between two zwitterions (carboxybetaine and sulfobetaine) and four types of cations (Li, Na, K, and Cs) in aqueous solutions. We studied the number and lifetime of various zwitterion–cation associations and observed that both carboxybetaine and sulfobetaine have the same order of association number and lifetime: Li> Na> K> Cs. Simulation results showed that the association variation as a function of cation types for these two zwitterions is significantly different. The effect of anion type on the order was also investigated by varying the type of anions from Cl–to Br–and F–. In order to further investigate zwitterion–cation association, we simulated the systems either with one type of zwitterion and two types of cations or with one type of cation and both carboxybetaine and sulfobetaine presented. This allowed direct competition between the solutes, and the observed association number and lifetime validated the order. Simulation results further demonstrated that, although CB associates stronger with Li橷 Na똖 SB, the latter is associated preferentially by K橷 Cs. [ABSTRACT FROM AUTHOR]

This work investigates the effect of zwitterionic molecules on ionic association in ethylene oxide (EO)-based electrolytes using molecular dynamics simulations. Zwitterionic molecules can associate with cations and anions because they possess both positively and negatively charged groups. This unique feature can be leveraged to develop electrolytes with high ionic conductivity if we understand how zwitterionic molecules influence ionic associations. We investigate the ionic associations in the electrolytes composed of oligo(ethylene oxide) (EO) (EO x , x = 2, 3, 4, and 5), LiTFSI and zwitterionic molecules containing cationic imidazole group and anionic sulfonate group using molecular dynamics simulations. The analyzed properties include the radial distribution functions between Li+, [TFSI]-, EO x and zwitterionic molecules, the structures and dynamics of Li+-[TFSI]-, Li+- EO x and Li+-zwitterion associations, and the diffusion coefficients of Li+, [TFSI]-, EO x and zwitterionic molecules. The simulation results show two distinct effects of zwitterionic molecules on ionic associations in the electrolytes. First, they could release Li+ from the trapping effect of EO x chains and accelerate Li+ transport. Second, they can associate with Li+ themselves and slow down the Li+ transport. The competition between these two effects relates to the length of the EO x chains. Our simulations suggest that zwitterionic molecules could help manipulate the ionic conductivity of polyethylene oxide electrolytes. Image 1 [ABSTRACT FROM AUTHOR]

[Display omitted] • Hydrogen bond microstructure of DESs and lignin played a major role in dissolution. • Strong dissolution abilities of the Lac:ChCl and Oxa:ChCl solvents for GGM and GSM were due to the different HB interactions. • Large extended structure of lignin would increase the active exposed areas of β–O–4 bond in DES solvents. • Small |HOMO–LUMO| gap suggested that GGM and GSM had high reactivities in the Lac:ChCl and Oxa:ChCl solvents. • Average surface potential charge confirmed that solvents had different solubilities and effects on the β–O–4 bond. Acid choline chloride (ChCl)–based deep eutectic solvents (DESs), are widely used as effective green solvents of lignin, which contributes to the high–value application of biomass. Understanding the underlying microscopic-scale lignin dissolution mechanism of different acid ChCl–based DESs is important for further DES design due to the heterogeneous and refractory structure of lignin. In this study, we employed molecular dynamics and quantum mechanics methods to investigate the behavior of lignin dimers (guaiacyl–guaiacyl [GGM] and guaiacyl–syringyl [GSM] dimers) in three acid ChCl–based DESs ([i] lactic acid [Lac]:ChCl [2:1], [ii] levulinic acid [Lev]:ChCl [2:1], and [iii] oxalic acid [Oxa]:ChCl [1:1]). Results showed that the dissolution tendencies of different lignin dimers in the three solvents followed different orders. Microstructural analysis revealed that the microstructure of the hydrogen bond (HB) between DESs and lignin dimer played a major role in dissolution. The high dissolution abilities of the Lac:ChCl and Oxa:ChCl solvents for GGM and GSM, respectively, can be attributed to the strong HB interactions between acid–GGM and Chol–GSM, respectively. Moreover, the large extended structure of the lignin dimer would increase the active area (β–O–4 had a large exposed area) in DES solvents. The highest occupied molecular orbital and lowest unoccupied molecular orbital gap between lignin dimers and choline molecules in the three solvents suggested that GGM and GSM had higher reactivities in Lac:ChCl and Oxa:ChCl solvents, respectively, than in other solvents. Finally, the statistical analysis of average surface potential charges further confirmed the different solubilities of the three solvents for different lignin dimers and their effect on β–O–4 bonds. [ABSTRACT FROM AUTHOR]

Oxytocin (OT) has long been deemed the 'love hormone' after its important role in social bonding has been documented. In the current study, the relative importance of five OT residues (X-X and X) was profiled systematically and quantitatively through an integrative approach. In the procedure, eight quantitative sequence-activity models were developed with classical amino acid descriptors and sophisticated random forest (RF) regression based on a panel of 49 known OT analogues. These models were further optimized to achieve both high internal fitting ability and strong external predictive power. The best model, which was built from the combination of VHSE descriptor and RF regression, was then employed to characterize the single position mutation profile of the five investigated OT residues. It is suggested that (i) the polar and charged amino acids presented at positions X, X and X are quite unfavorable to OTR-OT binding, and (ii) the positions X and X have only a moderate effect on the binding as compared to other three positions. Subsequently, three novel OT analogues, i.e. the single-point mutants [InlineMediaObject not available: see fulltext.], [InlineMediaObject not available: see fulltext.] and [InlineMediaObject not available: see fulltext.], were designed rationally in terms of the putative mutation profile, and their interaction mechanism with OTR were investigated at molecular level using atomistic molecular dynamics (MD) simulations and molecular mechanics/generalized Born surface area (MM/GBSA) analysis. Further, the agonistic potencies U of OA12 and OA90 were measured to be 0 and 190 IU/mg, respectively, by testing their agonistic capability against rat uterus, which are roughly consistent with the theoretical results arising from computational investigations. [ABSTRACT FROM AUTHOR]

As a growing concern in aqueous systems, micro- and nano-plastics, especially nanoplastics (NPs), have been widely detected in the environment and organisms, posing a potential threat to ecosystems and human health. Hydrophobic deep eutectic solvents (HDESs) have emerged as environmentally friendly solvents that have shown promise for extracting pollutants from water, either for detection or removal purposes. Herein, we investigated the extraction of polystyrene (PS) and polyethylene terephthalate (PET) NPs from aqueous solution using lignin based HDESs as sustainable solvents. Rapid extraction of both PET and PS NPs was observed with the high extraction efficiency achieved (> 95%). The extraction capacities for PET and PS could reach up to 525.877 mg/mL and 183.520 mg/mL, respectively, by the Thymol-2,6-dimethoxyphenol 1:2 HDES. Moreover, the extraction mechanism was studied using various techniques including Fourier-transform infrared analysis, contact angle measurements, molecular dynamics simulation, kinetics, and isotherm studies. This work lays a foundational basis for the future development of innovative HDES-based technologies in the detection and remediation of NPs as part of the grand challenge of plastic pollution. [Display omitted] • Sustainable lignin-based HDESs efficiently extracted NPs with extraction rates > 95%. • Physical interactions were the main driving force for the extraction process. • HDES-water interfacial properties could influence the extraction efficiency. • The dynamics and equilibrium states of NP extraction were studied. • High extraction capacities for NPs could be achieved. [ABSTRACT FROM AUTHOR]

Abstract: The behaviors of the ionic hydration in nanopore are of both biological and chemical interests. Using carbon nanotube (CNT) as the 1-D nanopore model, we investigated the effect of the modified groups (Cing on the pore inner wall on the hydration of Li+, Na+ and K+ with molecular dynamics simulation. The structures of the water molecules around the cations confined in the modified CNTs were compared with their counterparts in the pristine CNTs. Among the three cations, the sequence of the sensitivity for the spatial and orientation distributions of the water molecules in the first coordination shells is: K+ >Na+ >Li+. The same modification results in the opposite effects for the ionic hydration inside the (10, 10) and (8, 8) CNTs. Inside the (10, 10) CNT, the modification enhances the ionic hydration, whereas inside the (8, 8) CNT, the ionic hydration is weakened by the modification of CNT wall. [ABSTRACT FROM AUTHOR]

Peptide co-assembly is attractive for creating biomaterials with new forms and functions. Emergence of these properties depends on the peptide content of the final assembled structure, which is difficult to predict in multicomponent systems. Here using experiments and simulations we show that charge governs content by affecting propensity for self- and co-association in binary CATCH(+/−) peptide systems. Equimolar mixtures of CATCH(2+/2−), CATCH(4+/4−), and CATCH(6+/6−) formed two-component β-sheets. Solid-state NMR suggested the cationic peptide predominated in the final assemblies. The cationic-to-anionic peptide ratio decreased with increasing charge. CATCH(2+) formed β-sheets when alone, whereas the other peptides remained unassembled. Fibrillization rate increased with peptide charge. The zwitterionic CATCH parent peptide, "Q11", assembled slowly and only at decreased simulation temperature. These results demonstrate that increasing charge draws complementary peptides together faster, favoring co-assembly, while like-charged molecules repel. We foresee these insights enabling development of co-assembled peptide biomaterials with defined content and predictable properties. Co-assembly of peptide mixtures can yield interesting materials, but predictive understanding of assembly pathways is lacking. Here the self- and co-assembly preferences of oppositely-charged peptides are systematically studied experimentally and by molecular dynamics simulations. [ABSTRACT FROM AUTHOR]