Colloid osmotic properties of modified hemoglobins: chemically cross-linked versus polyethylene glycol surface-conjugated

Biophys Chem. 1997 Nov;69(1):23-30. doi: 10.1016/s0301-4622(97)00079-3.


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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cattle
  • Chemical Phenomena
  • Chemistry, Physical
  • Colloids
  • Cross-Linking Reagents / chemistry*
  • Hemoglobins / chemistry*
  • Humans
  • Macromolecular Substances
  • Molecular Weight
  • Osmotic Pressure
  • Polyethylene Glycols / chemistry*
  • Solutions


  • Colloids
  • Cross-Linking Reagents
  • Hemoglobins
  • Macromolecular Substances
  • Solutions
  • Polyethylene Glycols