Functionalized biotin. Biotinylated polyethylene glycol (PEG-Biotin) is an avidine or streptavidin reactive PEG derivative that can be used to modify biomolecues or other surfaces through biotin-streptavidin interaction. Used for addition of biotin-PEG to the N-terminus of resin-bound peptides. Can be introduced using standard coupling methods, such as PyBOP or TBTU and has better solubility in DMF and NMP than comparable non-PEG-containing derivatives, such as biotin-Ahx and biocytin.