Experimental and statistical analysis methods for peptide detection using surface‐enhanced Raman spectroscopy

Abstract

Surface-enhanced Raman spectroscopy (SERS) has the potential to make a significant impact in biology research due to its ability to provide information orthogonal to that obtained by traditional techniques such as mass spectrometry (MS). While SERS has been well studied for its use in chemical applications, detailed investigations with biological molecules are less common. In addition, a clear understanding of how methodology and molecular characteristics impact the intensity, the number of peaks, and the signal-to-noise of SERS spectra is largely missing. By varying the concentration and order of addition of the SERS-enhancer salt (LiCl) with colloidal silver, we were able to evaluate the impact of these variables on peptide spectra using a quantitative measure of spectra quality based on the number of peaks and peak intensity. The LiCl concentration and order of addition that produced the best SERS spectra were applied to a panel of synthetic peptides with a range of charges and isoelectric points (pIs) where the pI was directly correlated with higher spectral quality. Those peptides with moderate to high pIs and spectra quality scores were differentiated from each other using the improved method and a hierarchical clustering algorithm. In addition, the same method and algorithm was applied to a set of highly similar phosphorylated peptides, and it was possible to successfully classify the majority of peptides on the basis of species-specific peak differences.

Surface‐enhanced Raman scattering study of human serum on PVAAg nanofilm prepared by using electrostatic self‐assembly

“…[11] In recent years, it has been reported that single molecule detection is possible by SERS, suggesting that the enhancement factor can reach as much as 10 14 ∼ 10 15 . [12 -14] Recently, SERS has been increasingly employed in the study of biological molecules, [15,16] from DNA [15,17] and peptides [18,19] to whole proteins [20,21] and cells. [22 -25] The extensive employment of SERS in biological research is mainly because the data obtained are information rich and the method is nondestructive.…”

“…Additionally, this method is independent of mass, a common variable in many techniques used for biochemical analysis including mass spectrometry (MS), two-dimensional (2D) gel electrophoresis and western blots. [18] Because of its tremendous potential, particularly in the field of biophysical and biomedical spectroscopy, SERS has been widely applied for biophysical and biomedical analysis in recent years.…”

Adsorption of oligopeptides on silver nanoparticles: surface‐enhanced Raman scattering and theoretical studies

“…Mitchell et al [7] have recently reported that the SERS methodology is a key factor related with the success of the application of metal NPs in the appearance of strong SERS features from oligopeptides; also they used statistical analysis methods for the peptide detection by SERS. Wei et al [8] obtained the SERS spectra of three cysteine (Cys) containing aromatic peptides and penetratin, bound to nanoshell substrates.…”

A Cytosine-rich DNA Decorated Gold Nanoparticles Surface Enhanced Raman-Scattering Platform for Sensitive and Selective Detection of Silver Ions

“…Investigations have shown that nanogaps between two or more metal particles are associated with plasmonic "hot spots", and that SERS can greatly increase when the gap distance is reduced; 10,11 that is to say, the SERS signals can be controlled and modulated by electromagnetic field enhancement in interparticle plasmon coupling. Based on this mechanism, many biosensers have been established for the detection of various biomolecules, including peptides, [12][13][14] proteins, [15][16][17][18][19] DNA and RNA, [20][21][22] pathogen, [23][24][25] and living cells. [26][27][28] Studies have found that single-stranded DNA (ssDNA) can absorb on the surface of citrate-coated gold nanoparticles (AuNPs) through electrostatic interactions, which can prevent the AuNPs against salt-induced aggregation, 29 while the double-strand DNA (dsDNA) does not.…”