Theoretical analysis of adsorption thermodynamics for hydrophobic peptide residues on SAM surfaces of varying functionality

Abstract

At a fundamental level, protein adsorption to a synthetic surface must be strongly influenced by the interaction between the peptide residues presented by the protein's surface (primary protein structure) and the functional groups presented by the synthetic surface. In this study, semi-empirical molecular modeling was used along with experimental wetting data to theoretically approach protein adsorption at this primary structural level. Changes in enthalpy, entropy, and Gibbs free energy were calculated as a function of residue-surface separation distance for the adsorption of individual hydrophobic peptide residues (valine, leucine, phenylalanine) on alkanethiol self-assembled monolayers on gold [Au-S(CH(2))(15)-X; X = CH(3), OH, NH(3)(+), COO(-)]. The results predict that the adsorption of each type of hydrophobic residue is energetically favorable and entropy dominated on a methyl-terminated hydrophobic surface, energetically unfavorable and enthalpy dominated on a hydroxyl-terminated neutral hydrophilic surface, and very slightly favorable to unfavorable and enthalpy dominated on charged surfaces. These theoretical results provide a basis for understanding some of the fundamental effects governing protein adsorption to synthetic surfaces. This level of understanding is needed for the proactive design of surfaces to control protein adsorption and subsequent cellular response for both implant and tissue engineering applications.

Bioadhesion: a review of concepts and applications

“…In contrast, the hydrophilic, neutrally charged SAM (OH terminus) has been found to induce the least extent of unfolding or denaturation, leading to a good cell adhesion on the fibronectin/SAM surface [35]. The extent of denaturation of fibronectin on the OH and CH 3 surfaces is attributed to functional group dehydration and water-restructuring effects brought about by the substrate surface [36,37].…”

Comparison Between Empirical Protein Force Fields for the Simulation of the Adsorption Behavior of Structured LK Peptides on Functionalized Surfaces

“…The two SAM surfaces used in this study were represented by a hydrophobic, methyl-terminated SAM (CH 3 -SAM) and a hydrophilic, negatively charged carboxylic acid-terminated SAM (COOH-SAM). These surfaces were constructed using methods that Latour and coworkers [16][17][18][19][20][21][22] and others [23][24][25][26][27][28] have used in several previous simulation studies involving SAMs. The SAM surfaces were each represented as consisting of functionalized alkyl chains of 10 carbons, including the functional group carbon.…”

The phase state of NiTi implant material affects osteoclastic attachment

“…The outcome of protein adsorption process to a specific surface is contributed by the substrate surface free energy level [i.e., proteins with different properties (e.g., confirmation) can adsorb to a surface depending on the free energy level of that surface]. 10 Our hypothesis was simple; if there were differences in surface free energy between the two NiTi phases, it would probably result in different protein adsorption processes and finally to different cellular reactions.…”