Two technologies to ensure accuracy
Quant-peptides are available in two formats: without or with a Quant-Tag.
Both technologies offer high precision peptide standards, and may be complementary
Quant-Peptides with no Quant-Tag
When the peptide sequence does allow*, we can determine the net peptide content using a proprietary method which combines an optimized AAA with a detection in mass spectrometry (MS). A fee for service will apply, and 3 mgs of the peptide will be dedicated to the analysis.
* The peptide sequence should contain at least one, and ideally at least two of the following residues: Phe, Ile, Lys, Leu, Pro, Arg, Val.
Quant-Peptides with a Quant-Tag
When the peptide sequence does not contain any of the residues listed above, another proprietary technology may be used (“Quant-Peptides with a Quant-Tag”):
A Quant-Tag (proprietary dye) will be conjugated to the C-term of the peptide after an Arginine (R) or a Lysine (K) residue to allow its sub-sequence release by trypsin digestion.
This approach nicely fits wits with the SRM/MRM (Single/Multiple Reaction Monitoring) technology, where a protein from a sample is indirectly quantified by spiking a calibration peptide, and trypsinizing the sample.
The precise molecular mass of the tag (1356,7 Da) can be used in assessing the cleavage efficacy, and hence in setting the optimal trypsinization conditions of a sample using i.e. MS:MS methods. To do so, the Quant-Peptide must be spiked into the sample prior to trypsin digestion. The Quant-Tag is then used as a reporter of the trypsin digestion efficacy: a peak correspond-ing to the tag mass is indicative of trypsin di-gestion.
Quantitative Proteomics & High-Throughput Assays
Absolute quantification of protein-based biomarkers from complex samples is central to pharmaceutical and diagnostic proteomics. The identification and quantification of peptides derived from the protein of interest is routinely used in several mass spectrometry based methods, including Single/ Multiple Reaction Monitoring (SRM/MRM). Accurately quantified peptides is prerequisite to their use as internal calibrators.