Fig. 2: Membrane-purification based synthesis of defined mPEG-OH4966.

a Chain elongation cycle consisting of the coupling of the building block (DmtrO-Eg28-OTs) to the free nanostar-PEG alcohol (chain extension, (i)), removal of the protecting group (deprotection, (ii)) and diafiltration (iii). Repeating this cycle three times results in the nanostar-Eg112-OH species. b The terminal hydroxyls are then methylated (v) and subsequently the PEG chains are cleaved from the nanostar (vi) to obtain defined mPEG-OH with a molecular weight of 4966 Da (mPEG-OH4966).