Transport properties of isoleucine peptides in water

Isoleucine is physically and medically important to the human body. We conducted a molecular dynamics study to investigate the self-diffusion and binary diffusion coefficients of isoleucine peptides with different chain lengths (1, 2, 4, and 16) in an aqueous medium using Einstein’s and Darken’s relations, respectively. The estimated value of the self-diffusion coefficient of an isoleucine monomer is 8.85 × 10−10 m2 s−1, which decreases systematically with increasing chain length, reaching a minimum value of the self-diffusion coefficient 3.04 × 10−10 m2 s−1 for 16 monomer chain. Furthermore, the dependence of the self-diffusion coefficient on system size was examined, revealing that the self-diffusion coefficient of water molecules increases with system size. In addition, we have observed the shear viscosity of the isoleucine peptide using the Einstein relation. The result shows that shear viscosity decreases with increasing number of molecules, as the number of molecules varies across different simulation boxes.