sentences:  Moreover, the experimental conditions of PEGylation reaction (i.e.pH, temperature, reaction time, overall cost of the process and molar ratio between PEG derivative and peptide) also have an impact on the stability of the final PEGylated products.To overcome the above mentioned limitations different strategies such as changing the size (Mw), the number, the location and the type of linkage of PEG molecule were offered by several researchers