More recently, techniques for imaging PG have been reported, including the use of fluorophore-tagged lectins or cell wall-binding antibiotics, metabolic labeling strategies based on the detection of free thiols or radioactivity and enzymatic methods utilizing fluorescent substrates.
Currently, there exists a variety of methods for studying metabolic networks in both quantitative and qualitative manners: flux balance analysis (FBA) [ 29- 31], C-labeling based metabolic flux analysis (C-MFA) [ 32], metabolic control analysis [ 33], elementary mode analysis (EMA) [ 34], extreme pathway analysis [ 35], cybernetic modeling [ 36, 37], and biochemical systems theory [ 38- 40].
Gene expression profiling was combined with proteomic analyses and the C isotope labelling based experimental determination of metabolic fluxes in the central carbon metabolism.
Label based quantitation (SILAC, TMT, iTRAQ): The foundation of the peptide labeling approach is incorporation of heavy isotopes into peptides or proteins by metabolic or chemical labeling.
The method is based on metabolic labeling combined with a modified radio-immunoassay and will routinely detect less than 5 pg/μl of de novo insulin synthesis in lysates from the insulinoma cell line MIN6.
It was previously shown that K8 and K19 are phosphorylated on tyrosine residues after treatment with the potent and irreversible tyrosine phosphatase inhibitor pervanadate, based on metabolic labeling using 32PO4 and phosphoamino acid analysis, as well as anti-phosphotyrosine antibodies [21].
Techniques for monitoring the dynamic changes within the proteome and metabolome are mostly based on metabolic labeling of metabolites and proteins using stable isotopes such as C or N in combination with mass spectrometry or nuclear magnetic resonance (NMR) analyses.
To date, several methods have been developed to detect protein S-glutathionylation based on immunological, metabolic labeling, and differential alkylation approaches.
The second method is based on the metabolic labeling of S-palmitoylated proteins in live cells with palmitate analogues containing an azide or alkyne group, and thus will reveal the proteins that have undergone S-palmitoylation during the labeling time.
Metabolic labelling techniques for MS based quantitative proteomics enable labelled and unlabelled samples to be combined at the tissue level.
