||Wright-Patterson AFB, OH 454337817
Research relates to current and prospective interests in design of improved materials for aerospace applications. Methodologies include electronic structure theory, chemical kinetics modeling, and molecular dynamics (including coarse-grained MD). Properties of interest include computation of transport properties (diffusion, electrochemical characteristics) and physical properties (glass transition, fragility, and density), elucidation of reaction pathways, prediction of interfacial phenomenon, and calculation of mechanical properties. More recently, emphasis has shifted to the simulation of bio-inspired materials as a function of pH, ionic strength and peptide/nucleotide sequence and structure. Projects of interest are described below:
(1) Classical and coarse-grained molecular dynamics are being conducted to simulate the assembly and function of biopolymers. Knowledge gained from these studies will be used to produce both biological and bio-inspired materials with tailored mechanical properties for a variety of Air Force applications, including structural components and templates for materials processing.
For example, bacterial gas vesicles are hollow structures made entirely of proteins produced by marine bacteria to aid in flotation; gas molecules can diffuse in, but water cannot. Condensation of moisture inside the vesicles is prevented due to its superhydrophobic interior surface, one of the most hydrophobic known. Our investigations seek to elucidate the mechanism, selectivity and location of gas transport across the vesicle walls. The ultimate goal is to identify critical interactions and residues responsible for allowing certain gases in while keeping water out and for maintaining the stability and strength of the vesicles.
Nereis virens jaw protein 1 (Nvjp-1) is a protein that confers differential hardness as a function of ionic species and concentration. Hydrogels incorporating Nvjp-1 have been engineered that exhibit dramatic contraction and hardening on exposure to zinc. Our simulations aim first to predict the native structure of this highly disordered protein. Structure in hand, we seek to characterize molecular behavior, specifically the nature and location of metal-coordinated interactions and the effects of variation in pH and ionic concentrations on those interactions.
(2) Molecular dynamics simulations are being employed to evaluate the modulus, strength, and fracture toughness of polymers and composites. Automating the incorporation of quantum mechanical simulations as needed to represent bond rupture and subsequent reactions in these composites will provide an advanced framework for evaluating physical and mechanical properties in these materials at the most fundamental levels. This project is in conjunction with ongoing experimental measurements and micromechanics calculations.
(3) Atomistic simulations are being used to investigate peptides that have been experimentally identified as “good” binders to inorganic and organic surfaces. Goals include the estimation of binding constants, determination of conformational changes on adsorption and elucidation of the mechanism(s) of binding, all of which are compared with extant experimental data. Analysis of these results centers on parameters including peptide sequence, surface coverage, pH, and surface structure/roughness. Extensions of this work include investigations of bio-mineralization in order to determine the thermodynamic stability of various morphologies and particle shapes.
Quantum mechanics (DFT); Classical molecular dynamics (all-atom and coarse-grained); Development of hybrid QM-MD techniques; Mechanical properties of polymer composites, assembly and structure-function relationships of bio-inspired materials; Bio-mineralization; Biopolymers;