Are there any direct methods for relative quantitation of a peptide (protein) in a complex sample by using a light synthetic peptide of the same?

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John S Wishnok

Can you clarify your question? What do you mean by a 'light' synthetic peptide (i.e., does this refer to stable isotopes)? Are you trying to quantitate a protein by measuring a specific peptide following digestion of the protein? How have you chosen the synthetic peptide? Is it an isotopomer of a prominent peptide in the digest or is it something that's not expected in the digest?

Sartaj Ahmad Mir

I am actually talking about proteotypic peptide(s) of a protein, that I am planning to synthesize-not heavy or stable isotopic counterparts. Yes I am planning to quantitate the protein following trypsin digestion. I am choosing this proteotypic peptide after observing the response in preliminary MRM type experiment carried out on tryptic digest of a complex sample. Thanks for your time, looking forward to your suggestions..