Theoretical Analysis on the Stability of 1-Pyrenebutanoic Acid Succinimidyl Ester Adsorbed on Graphene

Abstract

The adsorbed structure of 1-pyrenebutanoic acid succinimidyl ester (PASE) on graphene was investigated based on density functional theory. We found two locally stable structures: a straight structure with the chainlike part of butanoic acid succinimidyl ester (BSE) lying down and a bent structure with the BSE part directed away from graphene, keeping the pyrene (Py) part adsorbed on graphene. Then, to elucidate the adsorption mechanism, we separately estimated the contributions of the Py and BSE parts to the entire PASE adsorption, and the adsorption effect of the BSE part was found to be secondary in comparison to the contribution of the Py. Next, the mobility of the BSE part at room temperature was confirmed by the activation energy barrier between straight and bent structures. To take account of the external environment, we considered the presence of amino acids and the hydration effect by a three-dimensional reference interaction site model. The contributions of glycine molecules and the solvent environment to stabilizing the bent PASE structure relative to the straight PASE structure were found. Therefore, the effect of the external environment around PASE is of importance when the standing-up process of the BSE part from graphene is considered.

Possible bi-stable structures of pyrenebutanoic acid-linked protein molecules adsorbed on graphene: theoretical study

“…Lys indicates lysine, and RC is the active center of the antigen/antibody reaction. (c) Structures of PASE linker on graphene for conformation 1 and 2, respectively [ 9 ]. (d) Schematic PBA-linked molecular structures on graphene for conformation I and II, respectively.…”

“…As introduced, on graphene, PASE is found to be straight as the most stable conformation (conformation1 in Figure 1c ) [ 9 ]. On the potential energy surface, a curved conformation (conformation 2 in Figure 1d ) exists.…”

“…Our previous results suggested that conformation 2 is a metastable state. The relative stability of these conformations is known to vary depending on the surrounding environment, e.g., solvents and solutes [ 9 ].…”

“…Therefore, understanding the adsorption mechanism of the PASE linker on graphene and identifying characteristic conformations of the adsorbed molecules are of great importance. Recently, a research group including two of the present authors theoretically investigated the adsorption structure of PASE [ 9 ], revealing that PASE on graphene has a stable configuration (conformation 1) in a straight form on graphene. There is at least one metastable bent configuration (conformation 2) on the potential energy surface.…”

“…In this paper, we further examine a reaction pathway on the adiabatic potential energy surface that connects these conformations caused by the deformation of the PASE linker. The reaction pathway for the conformational change of the PASE itself was found to have a reaction activation barrier [ 9 ]. First, we identify that the origin of the barrier is the steric hindrance effect between two hydrogen atoms in the molecule.…”