To surmount these difficulties and with the goal of greater
functional precision we aim to create purer PEG-ylated
proteins. Notably, enhancement of in vivo serum half-life is
most significant above 20 KDa.[15] Whilst discrete PEG512[16]
(MW 22.6 kDa) is beyond the reach of current synthesis, a
strategy can be envisaged through which the same functional
effects can be achieved additively by attaching multiple,
shorter chains. Statistical modeling[17] of such combinations
revealed that current PEG sources[18–20] would be insufficiently
pure (Figure 1).