Hi Will, I previously used an extinction coefficient of 600M-1cm-1 for phosphotyrosine at 280nm estimated from figure 2 of this publication:
http://www.ncbi.nlm.nih.gov/pubmed/2418612 Hope that helps, Bernhard Bernhard C. Lechtenberg, PhD Postdoctoral Fellow Riedl Lab Sanford-Burnham Medical Research Institute 10901 North Torrey Pines Road La Jolla, CA 92037, USA Phone: 858.646.3100 x 4216 Email: [email protected]<mailto:[email protected]> On May 21, 2014, at 10:41 AM, Will Stanley <[email protected]<mailto:[email protected]>> wrote: Hello folks, I would like to measure the concentrations of proteins containing phosphotyrosines using absorbance at 280nm. I'm wondering about calculating extinction coefficients by the Edelhoch method - as used in ProtParam for example: http://web.expasy.org/protparam/protparam-doc.html Given that phosphotyrosine absorbs less strongly at 280nm than tyrosine, has anyone developed a modified extinction coefficient calculation that treats tyrosine and phosphotyrosine separately and has the same kind of accuracy that Edelhof achieved using amino acid analogues (e.g. comparing glycyl-L-tyrosylglycine to the phophorylated equivalent)? Cheers, Will.
