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[protein aqua strategy]http://www.creative-proteomics.com/services/absolute-quantification-aqua.htm Absolute Quantification is a targeted quantitative proteomics technique that exhibits robust efficacy and is being increasingly utilized for a wide variety of quantitative proteomics studies. AQUA strategy is for the absolute quantification (AQUA) of proteins and their modification states. Peptides are synthesized with incorporated stable isotopes as ideal internal standards to mimic native peptides formed by proteolysis. These synthetic peptides can also be prepared with covalent modifications (e. g. , phosphorylation, methylation, acetylation, etc.) that are chemically identical to naturally occurring posttranslational modifications. Such AQUA internal standard peptides are then used to precisely and quantitatively measure the absolute levels of proteins and post-translationally modified proteins after proteolysis by using a selected reaction monitoring analysis in a tandem mass spectrometer.

Advances in biological mass spectrometry have resulted in the development of numerous strategies for the large-scale quantification of protein expression levels within cells. Besides the measurements of protein expression accomplished through differential incorporation of stable isotopes into cellular proteins, the absolute quantification is a useful method in proteomics analysis.

The absolute quantification strategy: a general procedure for the quantification of proteins and post-translational modification. AQUA provides absolute quantification by employing synthetic peptides containing stable isotopes.

The absolute quantification method is based on the discovery of an unexpected relationship between MS signal response and protein concentration: the average MS signal response for the three most intense tryptic peptides per mole of protein is constant within a coefficient of variation of less than 10%. Given an internal standard, this relationship is used to calculate a universal signal response factor. The universal signal response factor (counts/mol) was shown to be the same for all proteins tested.

protein identification by peptide mass fingerprinting

Creative Proteomics provides [protein identification by peptide mass fingerprinting]http://www.creative-proteomics.com/services/peptide-mass-fingerprinting-pmf.htm (PMF) analysis and ions searching against database for rapid identification of proteins.

Peptide mass fingerprinting (PMF) is an analytical technique for protein identification. Basically, the unknown protein of interest is first cleaved into smaller peptides, whose absolute masses can be accurately measured with a mass spectrometer such as MALDI-TOF or ESI-TOF. Then these masses are compared to either a database containing known protein sequences or even the genome sequence which can be translated into proteins through computer programs. Then the absolute masses of the peptides from each protein are calculated theoretically for mass comparison between the peptides of the unknown protein and the theoretical peptide masses of each protein to find the best match.

glycan analysis of therapeutic glycoproteins

As one of the most important post-translational modifications of proteins in eukaryotic cells, protein glycosylation is involved in a wide range of biological and physiological processes, including recognition & regulatory functions, cellular communication, gene expression, cellular immunity, growth and development.

[glycan analysis of therapeutic glycoproteins]http://www.creative-proteomics.com/application/n-glycan-analysis.htm functions are usually determined by the structures of the oligosaccharides, which are covalently attached to proteins primarily at 2 structural motifs: the amide group of an asparagine (N-glycans) or the hydroxyl group on serine or threonine (O-glycans). Because of the diversity of the oligosaccharides, even glycosylation at a single site can generate considerable heterogeneity of the mass and charge of glycoproteins. Although different approaches for N-glycans analysis have been described, usually these methods are based on enzymatic release of N-glycans from the protein by PNGase F, and derivation of released glycans, due to the lack of intrinsic chromophores, with a fluorescent labelling before analysis.