AVS 53rd International Symposium
    Biomaterial Interfaces Friday Sessions
       Session BI-FrM

Paper BI-FrM9
Biomolecule Adsorption Studies at Interfaces using Sum Frequency Generation Vibrational Spectroscopy, Quartz Crystal Microbalance, Dielectric Spectroscopy, and Conducting-Probe Atomic Force Microscopy

Friday, November 17, 2006, 10:40 am, Room 2014

Session: Biomolecular Surface Characterization II
Presenter: O. Mermut, UC, Berkeley and Lawrence Berkeley National Lab
Authors: O. Mermut, UC, Berkeley and Lawrence Berkeley National Lab
R.L. York, UC, Berkeley and Lawrence Berkeley National Lab
D.C. Phillips, UC, Berkeley and Lawrence Berkeley National Lab
J.Y. Park, UC, Berkeley and Lawrence Berkeley National Lab
K.R. McCrea, Polymer Technology Group
R.S. Ward, Polymer Technology Group
G.A. Somorjai, UC, Berkeley and Lawrence Berkeley National Lab
Correspondent: Click to Email
A combination of different surface-specific techniques (probing macroscopic and molecular-scale properties) was employed to examine the adsorption behavior of biomolecules onto surfaces of variable chemistry and hydrophobicity. Various short-chain model peptides, composed to two types of amino acids (hydrophilic and hydrophobic) were synthesized to investigate the effect of the amino acid side-chain chemistry on adsorption at the water/polystyrene and the water/silica interface. Specifically, these peptides contain hydrophobic (X) and charged (Y) amino acids with sequence: Ac-XYYXXYXXYYXXYX-NH@sub 2@ (designed to yield an alpha-helical peptide) or Ac-XYXYXYX-NH@sub 2@ (designed to yield a beta-strand peptide). Sum Frequency Generation (SFG), a non-linear optical spectroscopic tool, provided molecular-level information regarding the orientation of the adsorbed biomolecules. Specifically, the hydrophobic amino acid residues preferentially order on hydrophobic polystyrene/water interfaces. This ordering is strongly dependent on chain length and sequence. Quartz Crystal Microbalance (QCM) allowed quantitative in situ determination of the adsorbed mass of material, which is influenced by the surface hydrophobicity. Impedance measurements were obtained using Dielectric Spectroscopy to investigate perturbations of the electrical double layer in the presence of adsorbed biomaterial. Lastly, we measured the morphological properties (topography, aggregation), mechanical properties (adhesion and friction force), and electrical transport properties (conductance) of adsorbed peptide at these various liquid-solid interfaces using a Conducting Probe-Atomic Force Microscopy (CP-AFM). Using this combinatorial approach of techniques, we will discuss how molecular level information correlates with macromolecular properties.