Why freeze-thaw cycles generate a gradient

[Dima Klenchin]

rosie.redfield at zoology.oxford.ac.uk (Rosie Redfield) wrote:
>The presence of a solute such as sucrose interferes with formation of ice
>crystals and so lowers the freezing point of the solution.  But solutions
>usually become less homogeneous as they freeze, and that's why melting
>causes a gradient to form.

Sorry, incorrect. It's not melting that causes it to form. It is freezing 
(ice floats). Anyone who ever stuck serum in -20C saw a gradient of 
hemoglobin formed in the forzen tube/bottle.

- Dima