There sure are a lot of you. Thanks for coming, I am glad people seem to be enjoying the site for the most part!

Again, another artificial sweetener discovered by sloppy, sloppy chemists. God bless them (us?). It makes me wonder sometimes whether I’m working with a bench full of delicious chemicals that are just waiting for an accidental taste.

Aspartame was discovered in 1965 by James M. Schlatter, a chemist working for G.D. Searle & Company. Schlatter had synthesized aspartame in the course of producing an anti-ulcer drug candidate. He discovered its sweet taste serendipitously when he licked his finger, which had accidentally become contaminated with aspartame.

Here is the structure of aspartame. It is the methyl ester of a dipeptide of aspartic acid and phenylalanine. That’s it. It’s an incredibly simple structure:

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One thing they touch on in biology class but never really get into is the fact that DNA is wound up into a tight little structure in the nucleus of eukaryotic cells, as well as sperm. Just how the cell gets the DNA to cooperate isn’t really explained. DNA is a polyanion - that is, it has a repeating negative charge.

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Monday, I remarked that cyanoacrylate (superglue) adhesives are used by some forensic scientists to expose fingerprints on objects. I actually hadn’t heard of the procedure before and was eager to try it out. As anyone who has known the pleasure of my company for very long can attest, I am not the most patient person in the world. It is with great pleasure that I bring you yet another MOTD experiment, with more camera phone quality pictures!

The general idea here is that cyanoacrylate adhesives are volatile. The most likely cyanoacrylates you’ll encounter are the methyl and ethyl esters, the boiling points of which people seem to disagree on a bit. I decided to just try using a bath of hot water from my faucet, which is about 60C, or 140F, and hoped that would vaporize enough adhesive. Superglue stinks quite a bit, so you know it’s got at least an OK vapor pressure.

I then had to find a) a developing chamber and b) some stuff to get fingerprints on. I’d read that light surfaces were bad for this, since white-on-white was hard to see, so I got whatever I could find that was opaque and in a variety of colors.

The developing chamber ended up being an old pipet tip box (I had intended to use one of those disposable tupperware/gladware containers, but they were occupied by a few, ahem, ongoing experiments with sourdough starters). For fingerprinty objects, I briefly manhandled a Gatorade cap, a Listerine Freshstrips box, and my old Blockbuster Rewards card. My usual clumsiness, compounded by cheap Chinese-manufactured superglue tubes, had resulted in an unfortunate accident which temporarily rendered my right hand incapable of leaving fingerprints, so I had to use old lefty. In the box these went, with about half a mL of superglue squirted into each of two corners. The whole mess went into my science breadpan, filled with an inch or so of hot water. I left it to float for half an hour or so. The image is right before I took it out:

After taking it out, in a rare case of before-the-fact common sense, I put the whole thing in the fridge for about 10 minutes to cool down. This way, I wouldn’t be greeted by a cloud of noxious cyanoacrylate fumes, aching to polymerize on my eyes and sinuses. Below, you can see that it worked, sort of. The fingerprints are actually quite clear in person. Mostly on the Blockbuster card, but you can see a bit on all three. It is probably for the best that I don’t have high-resolution shots of my fingerprints online.

If you haven’t handled much superglue, you might be inclined to think the exposed fingerprints are a powdery, flaky coating based on appearances. It’s not. They are just as hard as any other cured superglue. The exposure is actually a negative cast of my fingerprints, in polycyanoacrylate! This works because your fingerprints contain enough bases (water, certain basic parts of proteins, maybe even certain fats) to initiate superglue polymerization. Let me know if you try it! See you tomorrow.

This is one of those molecules that everyone who does chemistry has heard of, but you rarely hear about it outside chemistry and engineering. HF is a member of the acids of group VII - that is, HF, HCl, HBr, and HI. If you paid attention in general chemistry, you know all Bronsted acids dissociate into their conjugate base and a proton, that is, HX -> H⁺ + X^-. This is the definition of a Bronsted acid - I am only saying Bronsted to be technically correct since there is another type of acid that we won’t get into today that doesn’t have to involve protons at all.

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Everyone has heard of superglue. If it weren’t so entrenched in everyone’s mind as something that existed, you’d be absolutely amazed. Whenever I am at Wal-Mart, a drug store, a dollar store, or anywhere that has the six two-gram tubes of superglue for a dollar, I compulsively grab at least one, usually shaking my bemused shopping mate or getting one on the phone (”Guess what I just found at Wal-Mart?!” “The six tubes of superglue again, huh?” “Don’t patronize me, it’s AMAZING!”). I have tolerant friends.

Superglue is a trade name (probably a generic name, by now, I guess, considering my vast superglue collection is definitely not all marketed by the same company) for a class of adhesives called “cyanoacrylates.” The superglue you buy at the store is typically either methyl or ethyl cyanoacrylate. Another cyanoacrylate adhesive, 2-octyl cyanoacrylate, is available to seal wounds. I’ve heard it’s commercially available as “dermabond,” but I’ve never seen it, even in the suture cabinet back when I volunteered in a hospital for a few years. You can be sure I will own some someday.

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So, if you read a bit during the week, you might have guessed that I was alluding to the purple line on our chromatograph being an optical brightener. If not, here’s the idea:

You know the stereotype of the “blue-haired little old lady”? This comes from the fact that they used to use certain dyes, such as Prussian blue, to color their hair. This is because grey hair is often not grey but a little bit yellow. For whatever reason, some decided that a whitish tinge was aesthetically a bit better. Color mixing isn’t quite as simple as it seems. Adding a hint of blue to something yellow can actually make it look whiter. This was the idea with bluing hair - too much, though, and it was obvious. As anyone who’s owned a white undershirt for longer than a week can attest, these get a bit dingy too. Bluing to the rescue. Such dyes were commonly added to the laundry.
At least until quite recently. While I have no idea what the state of the art is in hair-dying, I know that laundry scientists have largely switched to a class of compounds called optical brighteners. These are compounds that absorb light in the UV and near-UV (a little bit of which is available even inside), and re-emit it at lower energy, in the blue end of the spectrum. This ends up making things look even whiter. I had a hard time picking an example; there are many dyes that do this. One subclass of optical whiteners is the coumarins, though, and I love coumarin:

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The last, fastest spot on the chromatograph is FD&C Blue #1, or Brilliant Blue FCF:

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The next spot on our chromatograph is Red 40, or Allura Red AC. Here is its structure:

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Here’s one of our paper chromatography spots - the yellow dye is the beloved Yellow #5, or tartrazine:

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