I would like to covalently label an antibody with Alexa 647 following the protocol described in E. Lundberg et al. (J Immunol Methods. 322 (2007) 40-49) but I am not sure about the use of the TopTip Protein G micropipette tips (Glygen Corp.). In the paper it is mentioned that one micropipette tip contains 30 -50 Āµg of protein A according to the manufacturer. However, I can't find any information as to how much protein G is contained in the corresponding tips containing protein G. I need this piece of information to calculate the amount of dye needed. Has anyone already tried this method of antibody labeling? I would appreciate any piece of advice. Thanks.