I had actually noticed this before, that a lot of the good stuff I use for toning/astringing/aftershave had this "O" and "OH" arranged like a "V":
|acetic acid (vinegar)|
|citric acid (cologne, rosewater, witch hazel)|
|benzoic acid (aftershave)|
|glycolic acid ("AHA")|
|salicylic acid (exfoliating pepto-bismol mask, "psoriasis" creme)|
In organic chemistry skeleton structures (thanks, Wikipedia, for all the images in this post), "C"s and "H"s are left out so you can sort of see the shape, which is usually all the interest they provide. But these little forks of C(O)OH do something pretty neat:
|hydrogen bonding dimers|
And intuition tells me, that's got to be the key that unlocks desmosomes. It looks like the key on a can of SPAM, doesn't it? Maybe that's all this post amounts to, because even at the surface of the body, I am totally out of my depth as a scholar of biochemistry. But I vaguely remember a biology professor telling me something about lactic acid triggering adaptations in muscle tissue. The problem for my "theory" is, carboxylic acids are everywhere. Amino acids are carboxylic acids, fatty acids are carboxylic acids. These little guys from our shaving kit are small, polar, and easily soluble in water and alcohol, which may be the true selection factor, from an anthropological perspective. But I see the dimers coming together over the carboxyl binding sites between the much larger cadherins, then flossing them apart as osmotic pressure sucks them to and fro. The floss breaks, and each half then occupies a binding site, so the velcro won't stick anymore. (Until the skin dries, or the muscle gets some oxygen.)
Speaking of calcium-dependent protein binding: vinegar and citric acid are great for softening hard water. Is that why desmoglein and desmocollin seem to "need" calcium around, to occupy these ubiquitous chelators? I haven't installed a softener at my house: hard water is good for jelly making, and lower rates of heart disease. But the scale buildup is one reason I don't like to shower frequently. I let my family have all the hot water, so I don't have to crawl down in the subfloor as often to clean out the Rinnai.
Alcohol and carboxylic acids combine to make esters, which are interestingly prominent in both perfumery and fruits. So the new, "fruitier" me I've written about in relation to the former, may be less a personality development, and more a reflection of dietary needs related to my miserable skin condition. I didn't get much more than that from my reading about esters, though it did lead me to the theory above.
Triglycerides are actually tri-esters, of glycerol (glycerin) and fatty acids. The only thing special I could find about cocoa butter is that, whereas most oils have a variety in how the fatty acids are combined, cocoa butter consists mainly of a homogenous compound, with all the fatty acids in the same relative positions. Linoleic acid is especially facilitating to ester synthesis by our sebaceous glands, but the one that is actually converted is palmitic acid, found in the cocoa butter. So maybe the wrinkle-filling moisture gradient is derived from this metabolism.
It doesn't seem like the function of sebum esters are well understood; I think the reference article gives a fair assessment that these chemicals represent signals transmitted through the skin barrier. They're less polar than the acids, and thus able to traverse it dry. I would simplistically guess that they signal "dryness," therefore.
I conclude that Asquith and Somerset are even more clueless than me, having simply ascribed qualities to their soap on the basis of ingredients selected for fragrance. So they called their citrus soap "exfoliating," even though it is perfectly balanced for me, and their lavender "moisturizing," even though it dries me to the point of slight chapping. (Yes, I went back to the store, but they were out of my favorite!) We can't expect much from soap makers, is what I've learned over the years. But again, maybe these scent cues aren't just market appeal. I'm impressed by the lavender, but I don't want to hold it to my nose and sniff deeply.