Description
Date/Time: 04-05-2018 - Thursday - 05:00 PM - 07:00 PM
Sidong Tu1 Chandan Choudhury1 Samantha Collins3 Nataraja Yadavalli2 Nikolay Borodinov1 Igor Luzinov1 Sergiy Minko2 Olga Kuksenok1

1, Clemson University, Clemson, South Carolina, United States
3, Coe College, Cedar Rapids, Iowa, United States
2, Georgia University, Athens, Georgia, United States

Enhancing stability and activity of various enzymes is beneficial for applications ranging from food processing to biomedical applications. Enzyme stabilization can be achieved via conjugation of enzymes with solid substrates or other molecules. Our recent study demonstrated formation of highly thermostable enzyme-copolymer self-assembled structure with improved activity (Yadavalli, Nataraja S., et al. ACS Catalysis 7.12 (2017): 8675-8684). These studies showed that conjugates of the lysozyme (LYZ) with poly glycidyl methacrylate-oligo (ethylene glycol) methyl ether methacrylate (poly(GMA-OEGMA)) remained active even after prolonged heating at temperatures exceeding 1000C. Herein, we carry out molecular dynamics (MD) simulations at high temperatures using GROMACS Molecular Dynamics package. The crystal structure of LYZ (3TXJ) is solvated with TIP3P water model and CHARMM36 force field is used. We represent poly(GMA-OEGMA) with triads, with GMA unit sandwiched between the two OEGMA units (keeping the same ratio between the GMA and OEGMA as in our experiments). Our simulation results show significant stabilization of the LYZ structure at high temperatures in triad-water solution with respect to that in pure water. Time evolutions of a root mean square deviation (RMSD), a number of intra-protein hydrogen bonds (H-bonds) of LYZ and Dictionary of Secondary Structure in Proteins (DSSP) plots confirm the stabilization of the enzyme in the triad-water solution. We show that the robust stabilization is observed only at a high concentration of triads (90% w/w of polymers), in the remaining scenarios considered herein with lower concentration of polymers increasing triads content slows down unfolding process at high temperatures but does not prevent it. To summarize, our simulation show that the LYZ enveloped by copolymers (triads) remains stable at high temperatures only at high concentrations of the triads in the close vicinity of the enzyme, which prohibits water access to the enzyme. These studies are in a good agreement with our experimental findings showing significant improvement of the thermal stability of LYZ and densification of the polymer shell close to its surface. OK gratefully acknowledges NSF DMR #1460836 for financial support of SC and NSF EPSCoR OIA # 1655740 for partial financial support of ST.

Meeting Program
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5:00 PM–7:00 PM Apr 5, 2018

PCC North, 300 Level, Exhibit Hall C-E