Our ChromaLink™ Biotin Labeling Reagent will work very well for your protein plasma serum biotinylation. The product that we recommend depends on how much you plan to biotinylate. Our ChromaLink™ Biotin Labeling Kit allows for 5 separate reactions of 1 mg of total protein each. This kit comes with desalting apparatus with a molecular weight cut off of 7,000 kDa. The ChromaLink™ labeling reagent labels any amino groups so these desalting columns will remove any amine-containing small molecules that may be in the serum (i.e., hormones, minerals, etc.). This will allow for labeling of large amine-containing biomolecules only. If you were hoping to biotinylate more than 5 mg of protein, then we would recommend bypassing the kit and just buying the ChromaLink™ reagent and then following the protocol on our website to biotinylate your proteins. It will be necessary for you to purchase the Zeba desalting columns from Thermo Scientific. We recommend that you make a few modifications to the protocol to account for the fact that you will be working with a variety of different plasma proteins. You should determine the protein concentration of your serum solution using a BCA assay (Thermo Scientific) or the A280 and then use an average protein mw (perhaps ~70,000 kDa) to determine the number of moles of protein in the solution. Then add 10 molar equivalents of our ChromaLink™ Biotin Labeling Reagent. All of the proteins should be sufficiently biotinylated with this method.