Scientists Discover Equation that Explains Why Oil and Water Don’t Mix

by on July 24th, 2010
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Everyone knows that oil and water don’t mix. Oil is what chemists call “hydrophobic”, meaning it dislikes interacting with water – it has a phobia of water, in a sense. However, the exact physical model that explains why oil acts in this way has eluded scientists for many years. Understanding hydrophobic interactions is key to understanding such things as why proteins fold in their particular orientations and why biological membranes can perform such selective gate keeping – allowing some things in, while keeping other molecules out.

Now, researchers at the University of California (Berkeley) have discovered the mathematical equation that allows them to precisely model the hydrophobic interactions displayed by all molecules and biological systems. It’s an incredible breakthrough, the result of decades of painstaking work. The breakthrough was made possible by using beams of light (both visible and ultraviolet light) to study the forces between various layers of liquids interacting on the surface of water. It’s difficult to understate the importance of this discovery. Now, chemists and other researchers have the tools they need to precisely understand how water and oil-like substances interact. This will make studies of virus particles, biological systems (cell walls and membranes), and even chemistry in “green” solvents such as water containing organic reactants much easier. It is a critical breakthrough.

By increasing out understanding of how molecules behave at the surface of a cell membrane, we can begin to understand how virus infections propagate and can take the first initial step into devising strategies to boost our bodies own defenses against such things. Also, this new deeper understanding of hydrophobicity will allow researchers to design new medicines that are more easily absorbed into the bodies (largely water-based) tissues.

It’s not often that a simple equation makes such a dramatic impact on the field of science. A general understanding of what hydrophobicity “is” has been known for centuries. Now, we can assign a precise mathematical value to the property, and begin tailoring the system to raise / lower the value in the direction that we desire. The result will be more effective medications as well as a trickle-down effect of benefits in many different areas of science. It’s a perfect example of how math and chemistry can assist each other.

The source of this article can be found at: S. H. Donaldson, C. T. Lee, B. F. Chmelka, J. N. Israelachvili. ” General hydrophobic interaction potential for surfactant/lipid bilayers from direct force measurements between light-modulated bilayers” . Proceedings of the National Academy of Sciences , 2011, 108(38),15699.


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