Frequently Asked Questions

You get a panel of pre-aliquoted and dried heavy labeled internal standards, engineered for high-throughput, multiplex quantification of blood plasma proteins by mass spectrometry. Upon purchase you also get access to Skyline files with library, including iRT calculator, suggested peptides and transitions and exact amounts of each standard.

Read more about the technology and our products.

Yes, our Quantitative Recombinant Protein Standards (qRePS) are Lys and Arg ¹³C and ¹⁵N labeled recombinant human protein fragments, designed to serve as internal standards in mass spectrometry based quantitative proteomics experiments.

Read more about qRePS and our technology.

Each well includes qRePS for all different protein targets in the panel.

There are no peptides in the plate. Each well of the plate includes qRePS for all protein targets in the panel. When digested, every qRePS generates multiple proteotypic peptides, meaning that in one single well you get hundreds to thousands of quantitative peptides. All suggested quantitative peptide sequences are available in the Skyline library provided upon purchase.

Yes, suggested peptide sequences are available in the Skyline library, found with the lot specific data provided upon purchase. If you are interested in getting the information prior to purchase, please send an email to contact@proteomedge.com.

Send us an email to contact@proteomedge.com and we will be happy to discuss a solution with you.  

Add your diluted samples equivalent to 1 µL plasma to the well of the product plate to dissolve the dry panel. Run your standard workflow for digestion, reduction and alkylation or look at one of our suggested protocols.

If you need technical support, don’t hesitate to write to us at contact@proteomedge.com

Our panels are designed to be used with an equivalent of 1 µL of blood plasma, however, the technology is compatible with other bodily fluids such as CSF or urine as well as cell lines or tissues. There are also cases where other species were successfully analyzed using qRePS, such as samples from mouse.

Yes, you can. Extract the sample and use an equivalent of 1 µL plasma to each well.

Yes, use 1 µL of serum as the total protein composition is similar to 1 µL plasma. Please note that some of our panels, e.g. DiscoveryEdge175, contain coagulation proteins that are not present in serum.

In our 8-well plates, the first column holds the panel (A1-H1).

For our 48-well plates, the first 6 columns hold the panel (A1-A6, B1-B6, …H1-H6).

Add your diluted sample to the dry standards to dissolve, then continue with the digestion and your standard workflow.

We advise to pre-dilute your plasma to facilitate reproducible pipetting. For example you can use 10x dilution with 5 µL of plasma + 45 µL of buffer.

Yes, though we recommend you perform all steps of the digestion protocol in the wells of the product plate for best precision and accuracy. If you want to use only some of the wells or need to use another format for your experiments, or prepare a calibration curve, the qRePS panels are easy to dissolve. Follow our step-by-step procotol for dissolving the panels.

No, if your instrument setup does not require desalting or other sample clean up, you can inject directly for LC-MS/MS analysis after the digestion. If you regularly perform a sample clean-up, you can perform for example solid-phase extraction using C18 StageTips or similar.

No. The standards should be digested together with your sample prior to injection to the MS instrument.

Yes, you can. For such sample preparation, we recommend performing the digestion outside the plate. The qRePS panels are easy to dissolve to transfer from the plate. Follow our step-by-step procotol for dissolving the panels.  

Send us an email to contact@proteomedge.com and we will be happy to discuss a solution with you.

qRePS – Quantitative Recombinant Protein Standards – are recombinant human protein fragments incorporating heavy isotope labeled (¹³C/¹⁵N) lysine and arginine residues. Each qRePS covers 50-150 amino acids of a single endogenous protein, the sequence carefully selected to achieve the best performance during MS analysis.

Sample and qRePS are to be digested/enzymatically cleaved together and will thus follow the same dynamics, ensuring accurate and precise multi-peptide quantification.

Read more about the technology.

The Skyline files are available on our lot data web page. Search for the lot number of the product you purchased or scan the QR code on the plate label to get access to the Skyline library and more.

The detection range is specific for every LC-MS/MS setup and can also differ between plasma or serum. We can help guide you to investigate these parameters on your own system.

We recommend starting with a peptide-centric analysis to be able to spot any biological signal that can be presented on a peptide level. The protein concentrations can thereafter be calculated as the mean value of all quantitative peptides for each target.

In some cases, peptides need to be excluded from such calculation due to presence of PTMs on the endogenous protein which affects the quantitative results. As qRePS don’t have PTMs, the quantitative results don’t reflect the protein abundance in this case but rather degree of modification or its proxy. This could be interesting from a biological point of view if you would like to expand above absolute quantitation. In other cases, peptides could be excluded from protein quantification for their low ionization, matrix effects, low intensity or low precision.

All qRePS are internally produced by recombinant protein expression in E. Coli using minimal media containing heavy isotope labeled (¹⁵N and ¹³C) arginine and lysine. Each purified qRePS is quality controlled with regards to purity and absolutely quantified using LC-MS.

Read more about the technology.

The products are shipped at ambient temperature as they are stable in room temperature for at least a month. Freeze (-20°C) upon arrival for long term storage.

Long term storage should be -20°C, though the dry standards are stable at room temperature for at least a month.

The products are stable when stored in -20°C and we guarantee performance for at least 24 months from the date of purchase when recommended storage and handling conditions are met.