Absolute Quantitation of Phosphopeptides and Glycopeptides Using Coulometric Mass Spectrometry.

Phosphorylation and glycosylation are two important protein post-transitional modifications (PTMs). However, quantification of these PTMs is challenging due to the lack of protein or peptide standards. In this study, we introduced a novel approach using coulometric mass spectrometry (CMS) for absolute quantitation of phosphopeptides and glycopeptides without using standards.

Nitric oxide and peroxynitrite as new biomarkers for early diagnosis of autism.

Autism spectrum disorder, or autism, is a neurodevelopmental disorder of the developing child's brain with a genetic causality. It can be diagnosed at about three years after birth when it begins to present itself via a range of neuropsychiatric symptoms. Nitric oxide is a crucial small molecule of life synthesized within cells of our body systems, including cells of our brain.

Nitroxidative stress in human neural progenitor cells: In situ measurement of nitric oxide/peroxynitrite imbalance using metalloporphyrin nanosensors.

Nitric oxide (NO) is an essential inorganic signaling molecule produced by constitutive NO synthase (cNOS) in the neurological system. Under pathological conditions, NO rapidly reacts with superoxide (O) to generate peroxynitrite (ONOO). Elevated ONOO concentrations induce nitroxidative stress, potentially contributing to numerous pathological processes as observed in neurodegenerative diseases including Alzheimer's disease (AD).

Influence of endothelial nitric oxide synthase haplotypes on nitric oxide and peroxynitrite productions.

The impact of four clinically significant genetic variants of endothelial nitric oxide synthase (eNOS) polymorphisms on the concentrations of nitric oxide [NO] and peroxynitrite [ONOO] has been given scant consideration. This study utilized a [NO]/[ONOO] ratio to determine the extent of endothelial dysfunction caused by these variations in the eNOS gene. The single nucleotide polymorphisms (T-786C, C-665T, and Glu298Asp) and a variable number of tandem repeats (intron 4 a/b/c) were genotyped in human umbilical vein endothelial cells (HUVEC), using sanger sequencing and DNA electrophoresis, respectively.

Using Metalloporphyrin Nanosensors for Monitoring and Measurement of Nitric Oxide and Peroxynitrite in a Single Human Neural Progenitor Cell.

Nitric oxide (NO) is an inorganic signaling molecule that plays a crucial role in the regulation of numerous physiological functions. An oxidation product of the cytoprotective NO is cytotoxic peroxynitrite (ONOO). In biological systems, the concentrations of NO and ONOO are typically transient, ranging from nanomolar to micromolar, and these increases are normally followed by a swift return to their basal levels due to their short life spans.

Standard-Free Absolute Quantitation of Antibody Deamidation Degradation and Host Cell Proteins by Coulometric Mass Spectrometry.

Proteomic absolute quantitation strategies mainly rely on the use of synthetic stable isotope-labeled peptides or proteins as internal standards, which are highly costly and time-consuming to synthesize. To circumvent this limitation, we recently developed a coulometric mass spectrometry (CMS) approach for absolute quantitation of proteins without the use of standards, based on the electrochemical oxidation of oxidizable surrogate peptides, followed by mass spectrometry measurement of the peptide oxidation yield. Previously, CMS was only applied for single-protein quantitation.

Absolute Quantitation of Proteins by Coulometric Mass Spectrometry.

Accurate quantification is essential in the fields of proteomics, clinical assay, and biomarker discovery. Popular methods for absolute protein quantitation by mass spectrometry (MS) involve the digestion of target protein and employ isotope-labeled peptide internal standards to quantify chosen surrogate peptides. Although these methods have gained success, syntheses of isotope-labeled peptides are time-consuming and costly.

Online Monitoring of Methanol Electro-Oxidation Reactions by Ambient Mass Spectrometry.

Online detection of methanol electro-oxidation reaction products [e.g., formaldehyde (HCHO)] by mass spectrometry (MS) is challenging, owing to the high salt content and extreme pH of the electrolyte solution as well as the difficulty in ionizing the reaction products.

Coupling Electrochemistry with Probe Electrospray Ionization Mass Spectrometry.

A new coupling of electrochemistry with mass spectrometry (MS) using probe electrospray ionization (PESI) is presented. Due to the high salt tolerance of PESI, the detection of electrochemical reaction products in room-temperature ionic liquids (RTILs) is realized for the first time. Furthermore, PESI-MS allows the analysis of electrochemical reaction products on different or multiple electrode surfaces.

Online Investigation of Aqueous-Phase Electrochemical Reactions by Desorption Electrospray Ionization Mass Spectrometry.

Electrochemistry (EC) combined with mass spectrometry (MS) is a powerful tool for elucidation of electrochemical reaction mechanisms. However, direct online analysis of electrochemical reaction in aqueous phase was rarely explored. This paper presents the online investigation of several electrochemical reactions with biological relevance in the aqueous phase, such as nitrosothiol reduction, carbohydrate oxidation, and carbamazepine oxidation using desorption electrospray ionization mass spectrometry (DESI-MS).

Recent advances of electrochemical mass spectrometry.

This review article surveys some recent developments of electrochemistry (EC) in combination with mass spectrometry (MS) including instrumentation and bioanalytical applications.

Study of electrochemical reactions using nanospray desorption electrospray ionization mass spectrometry.

The combination of electrochemistry (EC) and mass spectrometry (MS) is a powerful analytical tool for studying mechanisms of redox reactions, identification of products and intermediates, and online derivatization/recognition of analytes. This work reports a new coupling interface for EC/MS by employing nanospray desorption electrospray ionization, a recently developed ambient ionization method. We demonstrate online coupling of nanospray desorption electrospray ionization MS with a traditional electrochemical flow cell, in which the electrolyzed solution emanating from the cell is ionized by nanospray desorption electrospray ionization for MS analysis.

Electrochemistry-assisted top-down characterization of disulfide-containing proteins.

Covalent disulfide bond linkage in a protein represents an important challenge for mass spectrometry (MS)-based top-down protein structure analysis as it reduces the backbone cleavage efficiency for MS/MS dissociation. This study presents a strategy for solving this critical issue via integrating electrochemistry (EC) online with a top-down MS approach. In this approach, proteins undergo electrolytic reduction in an electrochemical cell to break disulfide bonds and then undergo online ionization into gaseous ions for analysis by electron-capture dissociation (ECD) and collision-induced dissociation (CID).

Coupling of liquid chromatography with mass spectrometry by desorption electrospray ionization (DESI).

A liquid chromatography/mass spectrometry (LC/MS) method using desorption electrospray ionization (DESI) as a versatile interface has been established, which allows a wide range of elution flow rates, online derivatization via reactive DESI and further combination with electrochemistry.

Online mass spectrometric analysis of proteins/peptides following electrolytic cleavage of disulfide bonds.

The disulfide bond bridge is an important post-translational modification for proteins. This study presents a structural analysis of biologically active peptides and proteins containing disulfide bonds using electrochemistry (EC) online combined with desorption electrospray ionization mass spectrometry (DESI-MS), in which the sample undergoes electrolytic disulfide cleavage in an electrochemical flow cell followed by MS detection. Using this EC/DESI-MS method, the disulfide-containing peptides can be quickly identified from enzymatic digestion mixtures, simply based on the abrupt decrease in their relative ion abundances after electrolysis.

Online coupling of electrochemical reactions with liquid sample desorption electrospray ionization-mass spectrometry.

The combination of electrochemistry (EC) and mass spectrometry (MS) is a powerful analytical tool to study redox reactions. This work reports the online coupling of a thin-layer electrochemical flow cell with liquid sample desorption electrospray ionization mass spectrometry (DESI-MS) and its applications in investigating various electrochemical reactions of biological molecules such as oxidative formation and reductive cleavage of disulfide bonds and online derivatization of peptides/proteins. As a result of the direct sampling nature of DESI, several useful features of such a coupling have been found, including simple instrumentation, fast response time (e.