Paper BI-TuM5
Bioactivity of Adsorbed Protein Layers Correlated with Adsorbed Orientation and Conformation

Tuesday, October 21, 2008, 9:20 am, Room 202

It has been well established that protein interactions at biomaterial surfaces are of critical importance because it is the adsorbed protein layer that dictates how the body responds to an implanted material. In general, cells do not have receptors for synthetic materials thus lack the ability to directly respond to non-biological surfaces. Therefore, the critical factors that influence the subsequent cellular responses are the protein comprised in the adsorbed protein layer, their structures, and their bioactivities. Due to the complexity of protein structure and the inherent difficulty of studying surfaces, elucidating the detailed molecular mechanisms involved in protein adsorption is a daunting challenge. We have developed experimental methods to quantitatively assess the secondary structure of adsorbed protein layers using circular dichroism along with the bioactivity of the adsorbed protein layer using spectrophotometric assays. The following model proteins were investigated on alkanethiol (HS-(CH₂)₁₁-R, R = OH, CH₃, NH₂, COOH) modified gold surfaces: hen egg white lysozyme (14.4 kDa, pI ≈ 11, PDB# 1LYZ), xylanase from thermomyces lanuginosus (21.3 kDa, pI ≈ 3.9, PDB# 1YNA), and glucose oxidase from apergillus niger (63.3 kDa, pI ≈ 4.2, PDB# 1CF3). Since CD only provides information about the secondary structure of proteins, amino acid specific chemical modification was used to modify solvent accessible tryptophan residues to provide information about the tertiary structure of the adsorbed proteins and their adsorbed orientations. The results from these studies provide molecular-level insights regarding how surface chemistry influences the adsorbed structure of proteins and how this influences their bioactivity.