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We Finally Know Why Oil and Water Don't Mix
CoveredTrax writes "Everyone knows oil and water don't mix. It's a simple concept, sure, but the hydrophobic interactions between fats and water are crucial to the mechanics of microbiology. The weird thing is, the base theories of chemistry suggest that there's no reason oil and water shouldn't mix, even though it's obvious that's not the case. Now there's an explanation: a team of chemical engineers at the University of California, Santa Barbara have defined an equation that measures a compound's hydrophobic character. It's the first such equation of its kind."
I'd like to add a few points to this useful post, as a related expert.
As implied by the parent post, one of the biggest reason scientists care is because this is a dominating contribution to the folding of soluble proteins--proteins in water. The hydrophic effect has been understood for a long time (half a centery), including the fact that the entropic contribution to the free energy is proportional to the surface area change between two separate oil droplets and one. (This is the a-a(0) term in their equation.)
Their equation further adds contributions for the surface tension of the solvent (gamma) and an exponential decay term for the drying of water between the two two hydrophobic surfaces are they approach each other. Such phenomena have been well characterized in the last ten or so years by molecular dynamics simulations, and this appears to be an experimental confirmation of this effect.
The statement, however, that this paper finally describes the enigmatic hydrophobic effect is a gross PR overstatement.