Hi Alex, you can measure the absorbance at 214-220 nm, which is where the peptide bonds absorb, but you should know/calculate/predict the extinction coefficient of your peptide at that wavelength. Furthermore, you might try BCA assay which is colorimetric as the bradford but the reaction involves the peptide bonds (it has low sensitivity but an increase in temperature during the assay might help). Densitometry would be another way but but is give you only a rough idea: I would not recommend to do it. Finally, if you have the possibility to do it, the aminoacid analysis represents the golden standard analysis for a precise quantitation of peptides: this method involves a hydrolysis step, a separation by HPLC, detection.
Cheers, Mirella Sent from my iPhone > On 5 Feb 2017, at 22:33, Alex Lee <[email protected]> wrote: > > Dear All, > > Sorry for the off-topic question, I'd like to do Biacore SPR assay with > N-terminal biotinylated peptide as ligand (to Biacore SA chip) and my protein > as analyte. I have a question of how to determine the concentration of > biotinylated peptide （synthetic peptide), if the peptide has no Tyr and no > Trp residue, I guess amino acid analysis may not work because the N-terminal > of the peptide is biotinylated. > > I'd appreciate if anyone share his/her experience on this. > >
