Differential Mobility Mass Spectrometry Research Articles

Quantitation of Cyclosporin A in Cell Culture Media by Differential Mobility Mass Spectrometry (DMS-MS/MS).

Cell permeability is an important factor in determining the bioavailability of therapeutics that is usually measured by cell culture testing. The concentration of pharmaceutical in a medium such as Hank's Balanced Salt Solution with HEPES organic buffer (HBSS-HEPES) is measured at a series of time points, making simplicity and high throughput of the analytical method important characteristics. We report an electrospray differential mobility spectrometry mass spectrometry method (nanoESI-DMS-MS) for the rapid determination of cyclosporin A (CsA, cyclosporine) concentration in such a buffer. DMS technology provides gas phase atmospheric pressure ion filtration for small-molecule bioanalytical methods that suppresses interfering ions and reduces chemical noise, without the use of chromatography. This allows simplified sample preparation, fast calibration curve development, and shortened analysis times. It has also been noted that the DMS prefilter can reduce contamination of the mass spectrometer by salts, thereby extending mass spectrometer system uptime.In the application described here, DMS-MS/MS is applied to cyclosporine A (CsA) in cell medium. Sample preparation is limited to dilution with an ammonium acetate-methanol-water mobile phase and the addition of CsA-d4 internal standard. The isotope ratio data are obtained in DMS-MS MRM mode observing NH3 loss from the ammonium adduct of the two species. A calibration curve with high linearity (R2=0.998) is rapidly obtained with nearly zero intercept, while it was found that a liquid chromatography LC-MS method required a preliminary SPE step to obtain a linear calibration curve. The time for data acquisition in the DMS-MS MRM method with flow injection (FIA) or infusion introduction at ESI flow of 400nL/min is typically 30s leading to a cycle time of less than 1min.

Plasma Lipidomics Profiles After a Diet Characterized by Whole Grains Compared to a Diet High in Refined Grains and Added Sugars (FS03-07-19)

ObjectivesDietary patterns high in fiber from sources including whole grains, legumes, fruits, vegetables, nuts and seeds, are associated with lower risk of chronic disease, such as cardiovascular disease and cancer. We investigated how plasma lipidomics profiles differed between a diet high in whole grains (WG) versus a diet high in refined grains and added sugars (RG). MethodsUsing a randomized, crossover, controlled feeding study, 80 healthy participants (n = 40 men, n = 40 women, 40 normal weight, 40 overweight/obese), 18–45 y, were randomized to receive either a WG or RG diet for 28 days. After a 28-day washout period where participants resumed their habitual diet, they crossed over to the other diet. Targeted, differential mobility mass spectrometry was performed on fasting plasma samples collected at the baseline and end of each diet period and quantified the concentrations of 863 lipids from 13 classes. Paired t-tests and pairwise partial least squares-discriminant analysis (PLS-DA) were used to evaluate differences in lipid profiles between the two diets. ResultsAt a class level, only ceramides were significantly different when comparing the two diets. After removing lipid species with > 20% missing values or CVs < 25%, 606 were retained for species analysis. Sixty-seven lipid species were significantly different between diets at day 28 (FDR < 0.05): 38 of 414 detected triglycerides, 9 of 59 phosphatidylethanolamines, 9 of 63 phosphatidylcholines, 4 of 22 cholesterol esters, 3 of 11 sphingomyelins, 2 of 13 lysophosphatidylcholines, and 1 of 5 ceramides. The majority of significant lipids were higher in plasma after the WG diet. PLSDA analysis showed the first and second components explaining 49% and 8.4%, respectively. Based on the selected components, lipidomic profiles showed fair separation for the two groups of diet. R2 values were 0.07 and 0.43, and Q2 values were -0.03 and 0.04 for components 1 and 2, respectively. ConclusionsHigher concentrations of some lipid species such as cholesterol ester 12:0, a carrier of high-density lipoprotein, could indicate a favorable shift in lipid profiles. Further investigation using more complex models are being conducted. Funding SourcesNational Cancer Institute - National Institutes of Health.

Characterization of acyl chain position in unsaturated phosphatidylcholines using differential mobility-mass spectrometry

Glycerophospholipids (GPs) that differ in the relative position of the two fatty acyl chains on the glycerol backbone (i.e., sn-positional isomers) can have distinct physicochemical properties. The unambiguous assignment of acyl chain position to an individual GP represents a significant analytical challenge. Here we describe a workflow where phosphatidylcholines (PCs) are subjected to ESI for characterization by a combination of differential mobility spectrometry and MS (DMS-MS). When infused as a mixture, ions formed from silver adduction of each phospholipid isomer {e.g., [PC (16:0/18:1) + Ag](+) and [PC (18:1/16:0) + Ag](+)} are transmitted through the DMS device at discrete compensation voltages. Varying their relative amounts allows facile and unambiguous assignment of the sn-positions of the fatty acyl chains for each isomer. Integration of the well-resolved ion populations provides a rapid method (< 3 min) for relative quantification of these lipid isomers. The DMS-MS results show excellent agreement with established, but time-consuming, enzymatic approaches and also provide superior accuracy to methods that rely on MS alone. The advantages of this DMS-MS method in identification and quantification of GP isomer populations is demonstrated by direct analysis of complex biological extracts without any prior fractionation.

Radiation metabolomics and its potential in biodosimetry

Purpose: Radiation exposure triggers a complex network of molecular and cellular responses that impacts metabolic processes and alters the levels of metabolites. Such metabolites have potential as biomarkers for radiation dosimetry. This review provides an overview of radiation signalling and metabolism, of metabolomic approaches used in the discovery phase, and of instrumentation with the potential to assess radiation injury in the field.Approach: Recent developments in fast, high-resolution chromatography and mass spectrometry and new data analysis methods allow the quantitative assessment of thousands of metabolites based on biofluids obtained non-invasively. This complex analysis leads to the discovery-phase identification of groups of metabolites useful for screening and biodosimetry by targeted quantitative measurement. Instrumentation for target analysis can be simpler than that used for discovery, so we examine current technologies based on ion mobility.Conclusions: Recent published results and ongoing studies examine the complex changes in the levels of many metabolites caused by radiation exposure, and identify groups of small-molecule biomarkers for radiation biodosimetry. Based on results showing separation orthogonal to mass, chemical noise suppression, and high sensitivity, differential mobility mass spectrometry (DMS-MS) ion mobility spectrometry appears highly promising for the development of deployable instrumentation.

UV-Induced Bond Modifications in Thymine and Thymine Dideoxynucleotide: Structural Elucidation of Isomers by Differential Mobility Mass Spectrometry

Differential mobility spectrometry has been applied to reveal the occurrence of isomerization of thymine nucleobase and of thymine dideoxynucleotide d(5'-TT-3') due to bond redisposition induced by UV irradiation at 254 nm of frozen aqueous solutions of these molecules. Collision-induced dissociation (CID) spectra of electrosprayed photoproducts of the thymine solution suggest the presence of two isomers (the so-called cyclobutane and 6,4-photoproducts) in addition to the proton-bound thymine dimer, and these were separated using differential mobility spectrometry/mass spectrometry (DMS/MS) techniques with water as the modifier. Similar experiments with d(5'-TT-3') revealed the formation of a new isomer of deprotonated thymine dideoxynucleotide upon UV irradiation that was easily distinguished using DMS/MS with isopropanol as the modifier. The results reinforce the usefulness of DMS/MS in isomer separation.