Detection of Native Amino Acids and Peptides Utilizing Sinusoidal Voltammetry

Abstract

Native amino acids and peptides were detected at a copper microelectrode using sinusoidal voltammetry (SV). Traditionally, these molecules can only be measured after derivatization with either a fluorescent or electroactive tag. In this work, an electrocatalytic oxidation reaction at copper is used to detect underivatized peptides and amino acids. The oxidation reaction is somewhat independent of peptide structure (i.e., it is not limited to the detection of aromatic amino acids) and is therefore able to produce nanomolar detection limits for all amino acids and peptides tested. A scanning technique, sinusoidal voltammetry, is used to provide the sensitivity of constant-potential techniques but also provide selectivity gained through utilization of the frequency domain. The frequency spectrum due to the oxidation of each molecule has a unique "fingerprint" response resulting from the kinetics of oxidation at the electrode surface. Through examination of the frequency spectra, even structurally similar molecules can be easily distinguished from one another. Flow injection analysis is used to demonstrate the sensitive and selective detection of a variety of amino acids and peptides. This technique can also be easily coupled to a separation step, i.e., high-performance liquid chromatography or capillary electrophoresis without electrode fouling from the adsorption of the analytes.

Use of an electrochemically labeled nucleotide terminator for known point mutation analysis

“…The SV detection system has been described in great detail in previous publications from our group [40][41][42].…”

“…In previous work, the dependence of the frequency domain "fingerprint" response on the electrochemical characteristics of the analyte and experimental parameters chosen has been discussed [40][41][42]. The three-dimensional frequency response for the analyte of interest was obtained from the scan in time where the background subtracted signal was at its maximum (i.e., the top of the analyte peak).…”

Highly Sensitive and Rapid Assay of Substance P and Streptolysin O in Human Serum Using Immuno-liposomes and Gramicidin Channels

“…SP levels in human serum are typically in the range from 10 to 220 pg mL -1 . 9-12 A variety of methods have been exploited for the quantification of SP in biological fluids, including HPLC, 13,14 capillary electrophoresis, 15,16 electrochemical methods, 17,18 radioimmunoassay (RIA) [19][20][21][22] and competitive enzyme immunoassay (EIA). [23][24][25] The extraction of SP from biological fluids has frequently been used for enrichment of a smallmolecule weight peptide, i.e., SP, and the exclusion of largemolecular weight plasma or serum proteins.…”

A Versatile System for Arbitrary Function Large‐Amplitude Fourier Transformed Voltammetry

“…Kuhr and co-workers did some work in the analytical detection aspect of this form of voltammetry. With the so-called "digital equivalent of look-in amplifier" and phase-selective Fourier transform methods, they achieved ultra sensitive and selective detection of native carbohydrates [4], amino acids [5], nucleotides [6] and DNA [7]. They even coupled this technique to microchip electrophoresis device to obtain a more sensitive and selective detection [8].…”