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Fri Mar 23, 2007 11:34 am  |
| TheresaL wrote: |
| Pachouli wrote: |
Having taken biochemistry and organic chemistry, I can say there are two uses of the word acid. In chemistry, something is named an acid if it has a carboxyl (-COOH) group. Acid is also used for anything that changes the pH of a solution, usually by releasing a proton. (So yeah, what guapagirl said, an acid doesn't necessarily have to act acidic. It depends on other groups attached to the molecule and on the pH of solution it is added to, and on the presence of a buffer.)
An acid can denature a peptide (protein) rendering it inactive. But since there are a few variables involved, so it would probably either have to be measured or a best guess made. I would prefer the word of someone who studied the peptide than trying to make a guess myself. |
Very interesting! Are acids only capable of denaturing peptides at a low pH or can this happen if the "acid" is a neutral pH? I guess what I am asking is are both types of acids that you defined capable of denaturing a peptide. Also, I thought that part of the problem with CPs and acids (using the term to indicate a low pH solution) was that the acid could cause the copper to dissociate from the peptide creating free copper which might not be a good thing. This is different from denaturing a peptide or am I wrong on this? And is there reason to be concerned about the copper and peptide dissociating. |
Yes, a substance that acts as an acid (releases a proton and lowers the pH of the solution) can denature a protein. Bases can denature proteins too, that is why your skin burns if you touch liquid plumber. There a strong acids and weak acids, they both can chemically be named an acid because they contain the carboxylic group, but some acids will not give up the proton at all. Even water at neutral pH can act as an acid by giving up a proton, but it is chemically not named as an acid because it does not have a carboxyl group. Water is neutral because it acts as an acid and a base. In other words, whether something acts like an acid depends on the pH of the solution it is introduced to. In this case the solution is either your face alone, or your face + CPs.
When you put a lactic or glycolic acid on your face, you want it to act as an acid, it denatures the structural proteins (keratin) and that is how it exfoliates. This is why the strength of the acid you use for exfoliating depends on the pH more than the percentage.
When you put Retin-A on your face you want it to act as a delivery for Vitamin A, not as an exfoliant. But it does irritate the skin with the time. Additionally, retinoic acid is usually delivered with a buffer. A buffer is a substance that counteracts pH changes and maintains pH.
But the question is whether retin-A is strong enough acid by itself to denature the peptide binding the copper ion. Retinoic is by itself a rather weak acid, which means it does not want to give up its proton very much. So my guess would be I doubt it. |
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