Discipline: Chemistry and Chemical Sciences
Taylor Dorlus - Clark Atlanta University
Co-Author(s): Dalia Daggag, Clark Atlanta University, Atlanta, GA Dr. Tandabany Dinadayalane, Clark Atlanta University, Atlanta, GA
The knowledge on the interactions between graphene and amino acids is a key to produce graphene-based biochemical sensors, and biomedical implants. Graphene provides high sensitivity and selectivity when different molecules are adsorbed [1, 2]. In the present work, density functional theory (DFT) calculations were performed to examine the binding of two naturally occurring alpha-amino acids (Histidine and Proline) individually with the graphene. Two finite size graphene sheets of 62 and 186 carbon atoms were considered in our study. We have performed the conformational analysis for those two amino acids using HF/3-21G level as implemented in Spartan ’16. From the set of conformers generated for two amino acids, we have taken two most stable and one least stable conformers for optimization at the DFT level and to build the complexes with two different sizes of the graphene sheets. For each of the conformer considered for the amino acids, different possible orientations were taken into account in building the complexes. All of the complexes were fully optimized at the M06-2X/6-31G(d) level using Gaussian 16 program package. Binding energies with and without basis set superposition error (BSSE) were calculated. The effect of solvation on the binding affinity of amino acids with graphene was estimated in the aqueous medium. Our aim is to understand the binding affinity of histidine and proline with graphene, and the effect of varying the graphene sheet on the binding affinity. In case of histidine-graphene complexes, the competition between pi-pi and C-H/N-H…pi interactions exists. Proline is a cyclic amino acid. It should be noted that histidine exhibits higher binding energy than proline. This may be due to the presence of pi-electrons and two nitrogen atoms in five-membered ring of histidine. The most stable complex of proline-graphene shows multiple C-H…pi interactions along with N-H…pi interactions. Graphene size effect is negligible (within 0.7 kcal/mol) for both amino acids. Charge analysis indicates that small amount of electronic charge is transferred from graphene to amino acid.
Funder Acknowledgement(s): National Science Foundation HBCU-UP Research Initiation Award (Grant number 1601071), Saudi Arabian Cultural Mission (SACM), Extreme Science and Engineering Discovery Environment (XSEDE)
Faculty Advisor: Dr. Tandabany Dinadayalane, firstname.lastname@example.org
Role: I completed conformational analysis of the amino acids histidine and proline. I took the two most stable and one least stable conformers for optimization at the DFT level and to build the complexes with two different sizes of the graphene sheets. I performed calculations for all of the complexes, which were fully optimized at the M06-2X/6-31G(d) level using Gaussian 16 program package. I also calculated deformation energy for each amino acid and graphene by complexation. I also calculated HOMO, LUMO energies and HOMO-LUMO energy gaps. I have completed over 90 percent of the calculations for this project. I have written the first draft of the abstract and my advisor suggested corrections. I worked with my advisor to finalize the abstract.