I have a peptide sequence with a molecular Weight approximately 4.5 KD. They don't have any Tryptophan, Arginine, Lysine, cysteine, Phenylalanine or Tyrosine. Can anyone suggest me a method to determine this type of Peptides concentration?
If your sample is stable in water, you can buffer exchange it to DDi H2O, lyophilize it and measure the weight of the powder with an analytical balance. Redissolve in the desired volume of your buffer, and you will have very accurate concentration, provided you know the exact molecular weight of the peptide.
If peptide is not sable in water you can try lyophilization from buffer but you will have to account for the dry mass of the salt that will be left.
Hi Vishnu,
As per your question you can use Bradford assay and protocol you can get from this link
http://web.mnstate.edu/provost/BradfordProteinAssayProtocol.pdf
All the best.
Best option is to prepare a stock solution and take a fraction to quantitative amino acid analysis. If your research center does not have that analysis service, there are a number of companies that offer that. Just from a quick Google search: http://www.alphalyse.com/quantitive_aaa.html
By the way, you can also use the absorbance at 205 nm, although I've never used that method. All the information here:
http://www.ncbi.nlm.nih.gov/pubmed/23526461
you can use amino acid analysis which is described here:
http://www.sigmaaldrich.com/analytical-chromatography/analytical-reagents/amino-acid-analysis.html
at some universities they do this in analytical chemistry labs.
This method worked perfectly for my 30aa peptide which had only acidic amino acids.
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