Both fluorescamine assay (for free amine group) and TNSB assay (for S-S
bond) should work well to quantify your peptide. I do not have references
for fluorescamine handy, but you can find them in Rodionov's recent reply to
"peptide synthesis; fluorescamine labeling". The reference for TNSB assay is :
Thannhauser, T.W.; Konishi, Y. and Scheraga, H., Analysis for Disulfide
Bonds in Peptides and Proteins, in METHODS IN ENZYMOLOGY (1987), vol. 143.
Xiaohuui
Xiaohui Chen, Ph.D.
Department of Biochemistry
School of Medicine
Case Western Reserve University
2109 Adelbert Road
Cleveland, OH 44106
Ph: 216-368-3250
Fax: 216-368-3419
Email: xhchen@biochemistry.cwru.edu