Frequently Asked Questions about MicroSolv Peptides for Mass Spec, CE or HPLC Calibration and Tests
- What is a Tryptic Digest?
- Why should I buy these peptides if I could make them myself?
- Why is it important to insure limit digestion on each digestion? What will that do for me?
- How do you determine that the concentration of each vial of the peptides is accurate enough to measure sensitivity specs of mass spectrometers?
- How long will these peptides last?
- What analysis is done on each batch and what documentation is supplied?
- What is the concentration of peptides in each vial?
- What is the digestion chemistry that is used for these peptides?
- After I dilute these peptides according to the package instructions, can I further dilute them?
- Is there any special care I should take if I am going to use these peptides in HPLC?
- Are molecular weights of individual peptides provided with the purchase of the peptides?
- Is the sequence of the original protein supplied?
1. What is a Tryptic Digest? [top]
A tryptic digest is accomplished simply by taking a pure, whole protein and subjecting it to certain enzymatic
activity that breaks down the protein into specific peptides and or peptide chains. If the digesting is done
consistently and precisely, the peptides can be used to calibrate detectors such as Mass Spectrometers or they can
be used as standards in separation techniques such as CE or HPLC to measure and help identify peptides and proteins.
2. Why should I buy these peptides if I could make them myself? [top]
The answer is consistency and in process quality control. Using SOP’s that we have developed for consistency, we
insure limit digestion. Greater than 95% of the starter protein is digested as determined by HPLC of each batch in
production. Our production staff is well trained in proprietary techniques to match batch to batch consistency.
Since the batches will be the same, day to day, year to year, your analysis have a better chance for high degree of
precision. Also, actual batch test data is performed and supplied saving you the time and money it could take to
produce peptides of equal quality.
3. Why is it important to insure limit digestion on each digestion? What will that do for me? [top]
One common problem with tryptic digests is undigested protein that results could block your column or interfere with
the peptide map. With over 95% of the protein certainly digested, this problem is virtually eliminated. This will
give you more confidence that your peptide map is accurate and should eliminate the fear that you are destroying
your column.
4. How do you determine that the concentration of each vial of the peptides is accurate enough to measure sensitivity specs of mass spectrometers? [top]
To insure that each vial has the same amount of peptide in it, we quantitate the digests with RP-HPLC with UV at
200nm and provide this information with each purchase. This is important because to measure the sensitivity of a
Mass Spectrometer, you have to be able to calibrate against the known amounts in our vials. Mass spectrometer
manufacturers use our peptides to measure sensitivity worldwide.
5. How long will these peptides last? [top]
If the peptides are stored dry in the vials that they came in and have not been opened, they will last 1 year if
stored frozen and 1 month if stored at room temperature. Once they are reconstituted, they will last 2 days if kept
cold and the vial remains capped most of the time. Avoid freeze-thaw cycles once reconstituted.
6. What analyses are done on each batch and what documentation is supplied? [top]
Each purchase of peptides from MicroSolv includes a test certificate including Mass Spec data and HPLC Chromatograms
and instructions for dilution and storage.
7. What is the concentration of peptides in each vial? [top]
There are exactly 500 picomoles in each vial. Depending on the volume of your diluent, you can create any
concentration you would like.
8. What are the digestion chemicals that are used to produce these peptides? [top]
Reduction: (Dithiothreitol)
Alkylation: (IodoAcetic Acid)
Digestion: (TPCK Treated Trypsin)
9. After I dilute these peptides according to the package instructions, can I further dilute them? [top]
Yes, this is not a problem. Using serial dilution you can dilute down to 10fmol/µl.
10. Is there any special care I should take if I am going to use these peptides in HPLC? [top]
Yes, If you choose to dilute these peptides with an Acetonitrile concentration below 30% with the suggested 0.1%
formic acid for HPLC, do not use a mobile phase with the least polar solvent which is stronger than the injection
solvent matrix. This could result in band broadening.
11. Are molecular weights of individual peptides provided with the purchase of the peptides? [top]
Yes, each peptide is supplied with mass spectral data.
12. Is the sequence of the original protein supplied? [top]
The sequence of the original protein is supplied by contacting our technical service department.
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