IsoTopics™ – November 2016

Described here is the rigorous development and application of highly multiplexed assays for the in-depth quantitation of hundreds of proteins in mouse plasma and heart tissue samples. The method features a targeted MRM approach with stable isotope-labeled peptides used as internal standards. 

Antoniewicz MR and colleagues have developed a new scoring scheme to identify optimal ¹³C tracers in single and parallel labeling experiments of metabolic flux analysis (MFA) studies. The scheme is based on precision and synergistic metrics that, for the first time, accounts for non-linear flux intervals and avoids biases due to flux value normalization. 

Given the importance of glycomic characterization in biological systems, Muddiman and co-workers developed a new workflow for the combined profiling of deamidated glycosites and N-linked glycans in the differentiating xylem of Populus trichocarpa. 

In an effort to better understand the synthesis and turnover rates of glycosphingolipid (GSL) species, Skotland T et al. conducted a time-course study with HEp-2 cells grown in the absence/presence of a stable isotope-labeled substrate (either U-¹³C glucose or serine). 

Given the increasing application of quantitative MS methods (with stable isotope internal standardization) to clinical samples, aspects of quality and risk management must be considered for the assays to ultimately be fit for diagnostic purposes.