Sum frequency generation and solid-state NMR study of the structure, orientation, and dynamics of polystyrene-adsorbed peptides

Abstract

The power of combining sum frequency generation (SFG) vibrational spectroscopy and solid-state nuclear magnetic resonance (ssNMR) spectroscopy to quantify, with site specificity and atomic resolution, the orientation and dynamics of side chains in synthetic model peptides adsorbed onto polystyrene (PS) surfaces is demonstrated in this study. Although isotopic labeling has long been used in ssNMR studies to site-specifically probe the structure and dynamics of biomolecules, the potential of SFG to probe side chain orientation in isotopically labeled surface-adsorbed peptides and proteins remains largely unexplored. The 14 amino acid leucine-lysine peptide studied in this work is known to form an α-helical secondary structure at liquid-solid interfaces. Selective, individual deuteration of the isopropyl group in each leucine residue was used to probe the orientation and dynamics of each individual leucine side chain of LKα14 adsorbed onto PS. The selective isotopic labeling methods allowed SFG analysis to determine the orientations of individual side chains in adsorbed peptides. Side chain dynamics were obtained by fitting the deuterium ssNMR line shape to specific motional models. Through the combined use of SFG and ssNMR, the dynamic trends observed for individual side chains by ssNMR have been correlated with side chain orientation relative to the PS surface as determined by SFG. This combination provides a more complete and quantitative picture of the structure, orientation, and dynamics of these surface-adsorbed peptides than could be obtained if either technique were used separately.protein | surface | isotope labels | solid-liquid interface

Surface characterization of silicate bioceramics

“…Because of all these features, SFS is an ideal tool to analyse molecules at biointerfaces in contact with aqueous solutions. The orientation of model peptides and fibrinogen on both hydrophilic and hydrophobic surfaces was investigated with SFS (see Weidner et al [118] and references therein). Presently, there are no SFS studies of molecules adsorbed on silicate bioceramics; one of the reasons for this lack may be that SFS requires flat substrates.…”

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

“…Recently, a larger set of experimental studies has been published by Phillips and coworkers [8] on the adsorption behavior of this same set of LK peptides to both hydrophobic polystyrene and hydrophilic silica surfaces. Additionally and most recently, Castner and coworkers [9][10][11][12] have completed a comprehensive set of experiments studying the conformations and orientations of similar LK peptides adsorbed to a variety of material surfaces, including a hydrophobic methyl-terminated self-assembled monolayer (SAM) surface and a negatively charged carboxylic acid-terminated SAM on a gold substrate. The peptide-SAM surface studies completed by Castner and coworkers, coupled with results from similar previous studies, provide an excellent opportunity for the evaluation of different FFs in order to determine which FF is most capable of accurately representing peptide adsorption behavior for these types of systems.…”

In vitro observation of dynamic ordering processes in the extracellular matrix of living, adherent cells

“…[29][30][31][32][33][34][35][36][37][38][39][40] In particular, this technique has been applied to the in situ investigation of biomolecules, including peptides, [41][42][43][44][45][46][47][48][49][50][51][52] proteins, and DNA. [75][76][77][78][79] Previous work from our lab has demonstrated the ability of SFG spectroscopy to detect substrate modifications through a layer of adherent, fixed cells 80 and through living, nonadherent cells.…”