Stabilization of human haemoglobin by naturally occurring osmolytes

The influence of the naturally occurring osmolytes xylitol, glycine and betaine on the thermal stability of human haemoglobin was investigated. Experiments were made in the temperature range of 55-70degreesC, adding up to 30% w/w of osmolytes to the protein solution. All the additives stabilized haemoglobin, with xylitol and glycine appearing more effective. A kinetic analysis based on the Lumry-Eyring inactivation scheme showed that the denaturation process can be described by a second-order rate expression, with an apparent activation energy ranging from 45 to 82 kcal/mol. (C) 2002 Elsevier Science B.V. All rights reserved.