Re: Acoustical coagulation of protein?

hi Joel,

This is a very entertaining, fun question and I enjoyed the chance to read such an old paper!

It's not easy to draw firm conclusions from the work of Chambers and Flosdorf - in fact they seem a little unsure themselves as to what's going on in their experiments. However, we can make a few points. First, although heating and physical agitation can both cause proteins to denature and coagulate, the physical effect of sound on protein is in no way similar to cooking. Their apparatus generates 175 W of acoustic energy - even if all of that were converted to heat (which it is not), it's far below the amount of energy used in cooking (think of a 600 or 800 W microwave oven).

In their paper they refer to "cavitation" - that is, the formation of bubbles in solution which then collapse rapidly. In some circumstances this can generate extremely high localised temperatures and pressures - high enough, some claim, to promote nuclear fusion. This is not the case though in this experiment. The authors also discover that the types of gas present, the pH and the type of protein all affect the result - egg albumin coagulates whereas horse serum albumin does not.

There's not much more work in the literature on this phenomenon - it's not the kind of science that would be acceptable for publication these days. The simplest explanation is that the coagulation is caused by physical agitation due to the vibrating sound waves - in much the same way as cream or egg white stiffens when you whisk it or lumps form in milk when you shake it for long enough. Proteins often denature (unfold) at the interfaces of liquid/gas or liquid/solid and depending on the chemical nature of the amino acids that become exposed, will associate and coagulate to an extent. Presumably the chemical bonds and/or the surface properties of the serum albumin make it less susceptible to denaturation and coagulation under these conditions.

I've searched the PubMed archive for articles on the medical effects of rock concerts - there are papers on ear injuries, broken bones, fainting and drug/alcohol-related mishaps, but nothing about protein denaturation! I'd consider it extremely unlikely - most of the acoustic energy is probably absorbed at the surface of the body, in bones and soft tissues and is far below the intensity required to affect proteins in the body at all.

The egg story is very funny - and apocryphal. That is to say, it sounds just plausible, but more unlikely than not and cannot be confirmed unless you were to do the experiment yourself. Perhaps the Mythbusters might take it on.