Missing amide i mode in gap-mode tip-enhanced raman spectra of proteins

Carolin Blum, Thomas Schmid, Lothar Opilik, Norman Metanis, Simon Weidmann, Renato Zenobi*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

54 Scopus citations

Abstract

Tip-enhanced Raman spectroscopy is a surface sensitive analytical method that combines the advantages of scanning probe microscopy and Raman spectroscopy. It holds great promises for imaging of biological samples with high spatial resolution (10-50 nm), well below the optical diffraction limit. It offers the opportunity to directly localize and identify proteins and their conformation in a complex (e.g., native) environment. Tip-enhanced Raman (TER) spectra in the so-called "gap-mode" configuration with a metal tip in scanning tunnelling feedback with a metal substrate coated with different proteins (bovine serum albumin, immunoglobulin G, trypsin, and β-lactoglobulin) as well as of model octapeptides (with and without an aromatic amino acid residue) are presented. The goal was to determine if it is possible to reliably assign marker bands for proteins and if different secondary structures of proteins can be distinguished in their gap-mode TER spectra as reliably as by IR and conventional Raman spectroscopy. It is shown that contrary to the presented conventional Raman spectra of proteins the amide I mode, which is widely used to identify secondary structure motifs of proteins, is not visible in gap-mode TERS. Aromatic modes are prominent and can be used as reliable marker bands for imaging of proteins in a complex environment.

Original languageAmerican English
Pages (from-to)23061-23066
Number of pages6
JournalJournal of Physical Chemistry C
Volume116
Issue number43
DOIs
StatePublished - 1 Nov 2012
Externally publishedYes

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