The use of mass defect in modern mass spectrometry

Abstract

Mass defect is defined as the difference between a compound's exact mass and its nominal mass. This concept has been increasingly used in mass spectrometry over the years, mainly due to the growing use of high resolution mass spectrometers capable of exact mass measurements in many application areas in analytical and bioanalytical chemistry. This article is meant as an introduction to the different uses of mass defect in applications using modern MS instrumentation. Visualizing complex mass spectra may be simplified with the concept of Kendrick mass by plotting nominal mass as a function of Kendrick mass defect, based on hydrocarbons subunits, as well as slight variations on this theme. Mass defect filtering of complex MS data has been used for selectively detecting compounds of interest, including drugs and their metabolites or endogenous compounds such as peptides and small molecule metabolites. Several strategies have been applied for labeling analytes with reagents containing unique mass defect features, thus shifting molecules into a less noisy area in the mass spectrum, thus increasing their detectability, especially in the area of proteomics. All these concepts will be covered to introduce the interested reader to the plethora of possibilities of mass defect analysis of high resolution mass spectra.

Elemental composition and clustering behaviour of α-pinene oxidation products for different oxidation conditions

“…Mass defect plots are a convenient way to visualise highresolution mass spectral data (Kendrick, 1963;Sleno, 2012).…”

An integrated strategy for the systematic characterization and discovery of new indole alkaloids from Uncaria rhynchophylla by UHPLC/DAD/LTQ-Orbitrap-MS

“…For instance, NLF of 176 Da was able to select licorice saponins or the phase II metabolites of a drug which possesses a glucuronic acid residue [14,15]. Additionally, due to the increasing use of highresolution mass spectrometers, mass defect filtering (MDF) of complex MS data has been applied for the selective detection of compounds of interest, including drugs, their metabolites, endogenous ingredients, and naturally occurring plant metabolites [16,17]. More importantly, by setting different filters, stepwise MDF can be used to extract different components [18,19].…”

“…Moreover, the vinyl bond between C-17 and C-18 was replaced by a bisubstituted hydroxyethyl (δ H-16 2.83/δ C-16 47.2, δ H-17 3.78, 3.86/ δ C-17 63.4). It was possible to confirm the substructure of the proposed C-15 side chain due to the key HMBC correlations H-16/C-22, H-15/C-22, and H-17/C-15…”

Engaging Challenges in Glycoproteomics: Recent Advances in MS-Based Glycopeptide Analysis

“…Accordingly, distinction of different compound classes based on high accuracy monoisotopic mass measurements is an actively developing application area. Such applications are made possible by the unique mass defects of the elements, which thus encode elemental composition information into the exact masses of molecules [80]. The use of accurate mass measurements in glycopeptide analysis will be discussed below.…”