dPEG Biotinylation Reagents Chain length from amide to terminal carbonyl is 19.2 Angstroms. 4 °C 500 mg 750 Ideal spacer length for binding streptavidin conjugates 1 g 1200 (M.W. 673.78) Amine Reactive Biotinylation Reagent D. Scott Wilbur, et al., Bioconjugate Chemistry, 17(6), 1514-1522 (2006).