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Size comparison between proteins PEGylated with branched and linear poly(ethylene glycol) molecules
Author(s) -
Fee Conan J.
Publication year - 2007
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.21482
Subject(s) - peg ratio , ethylene glycol , pegylation , chemistry , molecular mass , size exclusion chromatography , viscosity , chromatography , polyethylene glycol , biophysics , biochemistry , organic chemistry , materials science , biology , enzyme , finance , economics , composite material
Therapeutic proteins conjugated with branched poly(ethylene glycol) (PEG) have extended in vivo circulation half‐lives compared to linear PEG‐proteins, thought to be due partly to a greater hydrodynamic volume of branched PEG‐proteins, which reduces the glomerular sieving coefficient. In this paper, viscosity radii of PEGylated α‐lactalbumin ( M r = 14.2 kDa) and bovine serum albumin ( M r = 67 kDa) prepared with linear and branched PEGs (with nominal molecular weights 5, 10, 20 and 40 kDa) were compared experimentally using size exclusion chromatography (SEC). PEG adduct:protein molecular weight ratios of the PEGylated proteins covered the range 1:12 to 6:1. Direct comparisons of experimentally measured viscosity radii were found to be misleading due to differences between actual and nominal molecular weights of the PEG reagents used. Comparison with predicted viscosity radii shows that there is no significant difference between the viscosity radii of branched and linear PEG‐proteins having the same total molecular weight of PEG adducts. Therefore, longer in vivo circulation half‐lives of branched PEG‐proteins compared to linear PEG‐proteins are not explained by size difference. It is also calculated that the molecular size cut‐off for glomerular filtration, 60 Å for a 30 kDa PEG, matches the 30–50 Å size range for the pores of the glomerular basement membrane. Finally, it is confirmed that prediction of PEG‐protein viscosity radii should be based upon conservation of the total PEG adduct surface area to volume ratio for both linear and branched PEG‐proteins regardless of PEGylation extent. Biotechnol. Bioeng. 2007;98: 725–731. © 2007 Wiley Periodicals, Inc.