Calorimetric study of crystal growth of ice in hydrated methemoglobin and of redistribution of the water clusters formed on melting the ice.
AUTOR(ES)
Sartor, G
RESUMO
Calorimetric studies of the melting patterns of ice in hydrated methemoglobin powders containing between 0.43 and 0.58 (g water)/(g protein), and of their dependence on annealing at subzero temperatures and on isothermal treatment at ambient temperature are reported. Cooling rates were varied between approximately 1500 and 5 K min-1 and heating rate was 30 K min-1. Recrystallization of ice during annealing is observed at T > 228 K. The melting patterns of annealed samples are characteristically different from those of unannealed samples by the shifting of the melting temperature of the recrystallized ice fraction to higher temperatures toward the value of "bulk" ice. The "large" ice crystals formed during recrystallization melt on heating into "large" clusters of water whose redistribution and apparent equilibration is followed as a function of time and/or temperature by comparison with melting endotherms. We have also studied the effect of cooling rate on the melting pattern of ice with a methemoglobin sample containing 0.50 (g water)/(g protein), and we surmise that for this hydration cooling at rates of > or = approximately 150 K min-1 preserves on the whole the distribution of water molecules present at ambient temperature.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1225534Documentos Relacionados
- Effect of type III antifreeze protein dilution and mutation on the growth inhibition of ice.
- The photochemistry of d(T-A) in aqueous solution and in ice.
- Diversity and association of psychrophilic bacteria in Antarctic sea ice.
- Thermodynamic characterization of the stability and the melting behavior of a DNA triplex: a spectroscopic and calorimetric study.
- Antifreeze protein modulates cell survival during cryopreservation: mediation through influence on ice crystal growth.