title: Colloid osmotic properties of modified hemoglobins: chemically cross-linked versus polyethylene glycol surface-conjugated.
abstract: Colloid osmotic pressures of hemoglobin solutions containing unmodified, intramolecularly cross-linked, intermolecularly polymerized, or polyethylene glycol (PEG) surface-conjugated hemoglobin have been measured to determine their macromolecular solution properties. Tetrameric and polymeric hemoglobins show nearly ideal solution behavior: whereas, hemoglobins conjugated to PEG have significantly higher colloid osmotic activity and exhibit solution non-ideality. From these studies, the average calculated molecular weights are 65.300 +/- 3500 for unmodified and intramolecularly cross-linked hemoglobin tetramers, 156,000 for ring-opened raffinose polymerized human hemoglobin, 97,000 for pyridoxalated human hemoglobin conjugated to a carboxy-PEG polymer, and 117,000 for bovine hemoglobin conjugated to a methoxy-PEG polymer. The calculated radius of gyration for tetrameric hemoglobins is 2.9 +/- 0.2 nm compared to 4.9 nm for the polymerized hemoglobin, and 7.2 and 14.1 nm for the human and bovine PEG-conjugated hemoglobins, respectively. Exclusion volumes are calculated to be 823 +/- 148 nm3 for tetramers, 4000 nm3 for polymers, and 13,000 nm3 and 94,000 nm3 for human and bovine PEG-conjugated hemoglobins, respectively. These studies show that polyethylene glycol conjugated to surface amino groups greatly increases the effective macromolecular size of hemoglobin in solution.
authors.affiliation: Department of Medicine, School of Medicine, University of California, San Diego 92161, USA.
authors.forename: K D
authors.initials: KD
authors.lastname: Vandegriff
authors.forename: M
authors.initials: M
authors.lastname: McCarthy
authors.forename: R J
authors.initials: RJ
authors.lastname: Rohlfs
authors.forename: R M
authors.initials: RM
authors.lastname: Winslow
mesh_terms: D000818:Animals; D002417:Cattle; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003102:Colloids; D003432:Cross-Linking Reagents / Q000737:chemistry*; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D046911:Macromolecular Substances; D008970:Molecular Weight; D009997:Osmotic Pressure; D011092:Polyethylene Glycols / Q000737:chemistry*; D012996:Solutions
chemical_list: D003102:Colloids; D003432:Cross-Linking Reagents; D006454:Hemoglobins; D046911:Macromolecular Substances; D012996:Solutions; D011092:Polyethylene Glycols