Multiplexed Discrimination of Single Amino Acid Residues in Polypeptides in a Single SERS Hot Spot

Abstract

The SERS‐based detection of protein sequences with single‐residue sensitivity suffers from signal dominance of aromatic amino acid residues and backbones, impeding detection of non‐aromatic amino acid residues. Herein, we trap a gold nanoparticle in a plasmonic nanohole to generate a single SERS hot spot for single‐molecule detection of 2 similar polypeptides (vasopressin and oxytocin) and 10 distinct amino acids that constitute the 2 polypeptides. Significantly, both aromatic and non‐aromatic amino acids are detected and discriminated at the single‐molecule level either at individual amino acid molecules or within the polypeptide chains. Correlated with molecular dynamics simulations, our results suggest that the signal dominance due to large spatial occupancy of aromatic rings of the polypeptide sidechains on gold surfaces can be overcome by the high localization of the single hot spot. The superior spectral and spatial discriminative power of our approach can be applied to single‐protein analysis, fingerprinting, and sequencing.

Optical tweezers-controlled hotspot for sensitive and reproducible surface-enhanced Raman spectroscopy characterization of native protein structures

“…Nevertheless, when measuring analytes at low concentrations, it is inconvenient to locate and focus on the nanometer-size hotspots from the conventional aggregated nanoparticles in colloidal suspension for in situ detection, thus lowering the feasibility and efficiency of the technique. To address this dilemma, mechanical manipulations are desirable alternatives to create hotspots dynamically at the designated location 7 , 30 , 31 . Recently, optical tweezers-assisted SERS has been developed to increase the efficiency for the SERS analysis in aqueous conditions 32 – 41 , by introducing the additional trapping laser beams to manipulate SERS substrates 42 , 43 .…”

Hydrated Ionic Liquids Boost the Trace Detection Capacity of Proteins on TiO2 Support

“…Surface-enhanced Raman scattering (SERS) has received increasingly attention in the detection of trace amounts of biomolecules due to its extremely high sensitivity and broad tailoring capacity to detect the specific analytes through unique vibrational fingerprints. 5 − 7 Compared with other optical detection techniques, 8 − 10 SERS shows a great advantage in noninvasive detection properties due to its simple operation and sample preparation. To detect trace biomolecules with SERS, many techniques have been applied to further improve the enhancement performance in a variety of applications.…”

An overview of surface-enhanced Raman scattering substrates by pulsed laser deposition technique: fundamentals and applications

“…Previous works [ 9 , 68 – 71 ] have showed the excellent SERS effect in the gap between neighboring Au or Ag NPs, that is, hot spot. However, the SERS effect is weakened when the islands are cross-linked with each other resulting from the decreased numbers of hot spots.…”