(a) SDS–PAGE analysis of azido installation by sortase A. Lane 1: MW marker, lane 2: GFP–srt–His6–ELP, lane 3: sortase A, lane 4: reaction mixture after 5 h of incubation, lane 5: purified GFP–C–N3. (b) MALDI–TOF of GFP–C–N3. (c) SDS-PAGE of click reaction between GFP–C–N3 and DBCO–PEG10k. Lane 1: MW marker, lane 2: GFP–C–N3, lane 3 to 5: reaction mixture of GFP–C–N3 and DBCO–PEG10k after 10, 30 and 180 min of reaction, lane 6: mixture of GFP–C–Gly3 and DBCO–PEG10k after 180 min of reaction. (d) SDS-PAGE of click reaction between GFP–C–N3 and DBCO–PEG with different MW. Lane 1: MW marker, lane 2: GFP–C–N3, lane 3 to 5: reaction mixture of GFP–C–N3 and DBCO–PEG with MW of 10, 20 and 30 kDa after reaction for 60 min. GPC curves of (e) GFP–C–PEG and (f) GFP–C–Polycarbonate, GFP–C–Polyphosphoester and GFP–C–PMPC, respectively.