Anjaiah Nalaparaju

Amid the bourgeoning demand for in‐silico designed, environmentally sustainable, and highly effective hair care formulations, a growing interest is evident in the exploration of realistic computational model for the hair surface. In this work, we present an atomistic model for the outermost layer of the hair surface derived through molecular dynamics simulations, which comprises 18‐Methyleicosanoic acid (18‐MEA) fatty acid chains covalently bound onto the keratin‐associated protein 10‐4 (KAP10‐4) at a spacing distance of ~1 nm. Remarkably, this hair surface model facilitates the inclusion of free fatty acids (free 18‐MEA) into the gaps between chemically bound 18‐MEA chains, up to a maximum number that results in a packing density of 0.22 nm² per fatty acid molecule, consistent with the optimal spacing identified through free energy analysis. Atomistic insights are provided for the organization of fatty acid chains, structural features, and interaction energies on protein‐inclusive hair surface models with varying amounts of free 18‐MEA (FMEA) depletion, as well as varying degrees of anionic cysteic acid from damaged bound 18‐MEA (BMEA), under both dry and wet conditions. In the presence of FMEA and water, the fatty acid chains in a pristine hair surface prefers to adopt a thermodynamically favored extended chain conformation, forming a thicker protective layer (~3 nm) on the protein surface. Our simulation results reveal that, while the depletion of FMEA can induce a pronounced impact on the thickness, tilt angle, and order parameters of fatty acid chains, the removal of BMEA has a marked effect on water penetration. There is a “sweet spot” spacing between the 18‐MEA whereby damaged hair surface properties can be reinstated by replenishing FMEA. Through the incorporation of the protein layer and free fatty acids, the hair surface models presented in this study enables a realistic representation of the intricate details within the hair epicuticle, facilitating a molecular scale assessment of surface properties during the formulation design process.

A well-known Werner complex, [Ni(4-methylpyridine)₄(NCS)₂], has been revisited to investigate its phase switching and shape-memory effect induced by p-xylene vapor.

In the last two decades, metal−organic frameworks (MOFs) have attracted overwhelming attention. With readily tunable structures and functionalities, MOFs offer an unprecedentedly vast degree of design flexibility from enormous number of inorganic and organic building blocks or via postsynthetic modification to produce functional nanoporous materials. A large extent of experimental and computational studies of MOFs have been focused on gas phase applications, particularly the storage of low‐carbon footprint energy carriers and the separation of CO₂‐containing gas mixtures. With progressive success in the synthesis of water‐ and solvent‐resistant MOFs over the past several years, the increasingly active exploration of MOFs has been witnessed for widespread liquid phase applications such as liquid fuel purification, aromatics separation, water treatment, solvent recovery, chemical sensing, chiral separation, drug delivery, biomolecule encapsulation and separation. At this juncture, the recent experimental and computational studies are summarized herein for these multifaceted liquid phase applications to demonstrate the rapid advance in this burgeoning field. The challenges and opportunities moving from laboratory scale towards practical applications are discussed.

Inspired by biological water channels (e.g., aquaporin with an hourglass shape), there is a growing interest in the use of conical nanopores for water purification; however, the surface roughness of conical nanopores has not been considered in the literature. In this work, a molecular dynamics simulation study is conducted to investigate water permeation through conical nanopores by considering both surface roughness and chemistry. In hydrophilic alumina nanopores, water permeability is found to increase with increasing surface roughness; however, a reverse trend is observed in hydrophobic carbon nanopores. Comprehensive microscopic analysis reveals that surface roughness in the carbon nanopores induces multiple high‐energy barriers and frequent forming/breaking of hydrogen bonding network, which impedes water permeation. In the alumina nanopores, water becomes more bulk‐like with increasing surface roughness, thus enhancing water permeation. The molecular insights from this simulation study provide quantitative understanding of water permeation in hydrophilic and hydrophobic conical nanopores and unravel the complex interplay between surface roughness and chemistry, facilitating the design of new materials for water purification.

Nanofiltration (NF) membranes with ultrahigh water flux and high ion rejection are substantially beneficial for desalination and wastewater treatment. However, synthesis of NF membranes with high water permeance while maintaining high ion rejection remains a great challenge. Herein, we report a highly stable covalent organic framework (COF) IISERP-COOH-COF1 membrane with high ion rejection and relatively high water flux. Through post-modification, the pore aperture of the IISERP-COOH-COF1 membrane can be constricted, thus preventing ions from accessing the pores. Further, covalent post-functionalization is helpful to reduce non-selective transport through invisible intercrystalline defects, thus enhancing salt rejection. Demonstrated by both experimental and simulation studies, the IISERP-COOH-COF1 membrane shows superior ion rejection (e.g., 96.3% for Na₂SO₄, 97.2% for MgSO₄, 99.6% for FeCl₃, 90.6% for MgCl₂, and 82.9% for NaCl) based on size exclusion, with a water flux above 0.5 L m⁻² h⁻¹ bar⁻¹.

In the quest for next-generation ceramic membranes, an embodiment of the gradient conical pore structure is foreseen as an intriguing route. In this proof-of-concept simulation study, we investigate water permeation through alumina membranes consisting of cylindrical and conical nanopores, respectively. For the cylindrical nanopores, water permeability increases with increasing the nanopore diameter (2.05, 3.10 and 7.62 nm). Due to the strong interaction of water with the hydrophilic pore surface, the effective viscosity of water in the nanopore is greater than the bulk viscosity; consequently, the simulated permeability is lower than the prediction by the Hagen–Poiseuille (HP) equation. For the conical nanopores with various apex angles (α = 0°, 9.6°, 19.2°, 28.9°, 38.9° and 49.2°), water permeability is predicted to be higher than the cylindrical counterparts and is the highest when α = 19.2°. The potentials of mean force reveal that the barrier for water permeation through the cylindrical nanopore is high and continuous over the entire nanopore, whereas the barrier through the conical nanopore is lower. Moreover, the nanofiltration of two solutes (sucralose and bisphenol A) is simulated. In the presence of solute, water permeability is reduced to a certain extent. Compared with hydrophobic bisphenol A, hydrophilic sucralose interacts more strongly with the nanopore, thus causing a greater pore blockage and a larger reduction in water permeability. This simulation study provides atomistic insights into the key factors governing water permeation through alumina nanopores, and validates the idea that water permeation can be enhanced using conical nanopores.

Molecular dynamics (MD) simulations are performed to study the adsorption of solute organic molecules (Ethinylestradiol (EE2) and testosterone) with different polymer membranes such as polyether sulfone (PES), polyvinylidene fluoride (PVDF). The equilibrium MD simulations results for the membrane solution interface system show that the interaction of EE2 with PES is specific and strong, whereas the interaction is weak and non-specific for PVDF. The binding free energies, the non-bonded short range interaction energies and mobility are also consistent with the interaction behaviour found in experiments. The adsorption of testosterone onto PES and PVDF is considered as control system. The result shows that binding free energies of PES and PVDF interacting with organic solute are consistent with experimental result in the order as; PES-EE2 > PES-Testosterone > PVDF-EE2 > PVDF-Testosterone. The formation hydrogen bonds and π–π interactions are observed between the EE2 and PES. In addition, adsorption of EE2 onto polyamide 6-12 (PA612) and polystyrene (PS) membranes are predicted. This simulation study provides molecular insights on the experimental observations and helps as a computational methodology to screen the membrane materials for EE2 removal from wastewater.

Biofilm formation by opportunistic pathogens serves as one of the major causes of chronic and persistent infections. Bacterial cells in the biofilms are embedded in their self-generated protective extracellular polymeric substances (EPS), which include exopolysaccharides, large adhesin proteins and extracellular DNA. In this study, we identified an antimicrobial peptide (AMP) LG21 that is able to interact specifically with the Psl exopolysaccharide of Pseudomonas aeruginosa, thus it can be used as a diagnostic tool for P. aeruginosa biofilms. Molecular dynamics simulation analysis showed that residues numbered from 15 to 21 (WKRKRFG) in LG21 are involved in interacting with Psl. Our study indicates that host immune systems might detect and interact with microbial biofilms through AMPs. Engineering biofilm EPS-targeting AMPs might provide novel strategies for biofilm detection and treatment.