title: Freeze-thawing induced structural and functional changes in glucose oxidase.
abstract: BACKGROUND
  Glucose oxidase enzyme may be a suitable model for studying the effect of low temperatures on structural and functional properties of biomacromolecules.
  
  
  OBJECTIVE
  The research aim was to study the freeze-thawing effect on glucose oxidase isolated and immobilized by cross-linking with glutaraldehyde
  
  
  METHODS
  Effects of freezing rates on conformation and activity of glucose oxidase isolated and cross-linked in solution with gluteraldehyde was studied.
  
  
  RESULTS
  Freezing with slow rate (2 degree C per min) induces significant protein aggregation, activity reduction and conformational changes in polar and hydrophobic regions. Freezing at 100 degree C per min, however, causes conformational changes primarily in polar regions, insignificant aggregation, depending on the number of freeze-thawing cycles and increases enzyme activity.
  
  
  CONCLUSIONS
  With the rise in glucose oxidase concentration in solution the low temperature-induced destabilization effect is reduced both during low and rapid freezing. At the slow cooling rate, cross-linking with glutaraldehyde results in more conformation alterations in polar regions of proteins, accompanied with an increase in enzyme activity.
authors.affiliation: Institute for Problems of Cryobiology and Cryomedicine, National Academy of Sciences of Ukraine, Kharkov, Ukraine. olnard@mail.ru.
authors.forename: O A
authors.initials: OA
authors.lastname: Nardid
authors.affiliation: Institute for Problems of Cryobiology and Cryomedicine, National Academy of Sciences of Ukraine, Kharkov, Ukraine.
authors.forename: E D
authors.initials: ED
authors.lastname: Rozanova
authors.affiliation: Institute for Problems of Cryobiology and Cryomedicine, National Academy of Sciences of Ukraine, Kharkov, Ukraine.
authors.forename: E I
authors.initials: EI
authors.lastname: Naumenko
mesh_terms: D001234:Aspergillus niger / Q000737:chemistry / Q000201:enzymology; D003080:Cold Temperature; D003432:Cross-Linking Reagents / Q000737:chemistry; D004800:Enzymes, Immobilized / Q000737:chemistry*; D005615:Freezing; D005656:Fungal Proteins / Q000737:chemistry*; D005949:Glucose Oxidase / Q000737:chemistry*; D005976:Glutaral / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D011487:Protein Conformation; D012996:Solutions
chemical_list: D003432:Cross-Linking Reagents; D004800:Enzymes, Immobilized; D005656:Fungal Proteins; D012996:Solutions; D005949:Glucose Oxidase; D005976:Glutaral