Tuesday, May 8, 2007

Odeur d'Asperge

Yes, it is asparagus season. I love this vegetable. Raw straight out of the garden, steamed with white wine and garlic, coated with olive oil and roasted on the grill, I can't get enough of it! Of course, for some of us that means plenty of malodorous urinary discharge. Yes, I'm talking about the infamous Asparagus Pee! The culprit - Asparagusic Acid. Derived from valine, this acid is unique to asparagus and appears to be the metabolic precursor to a number of odiferous sulfur-containing compounds. In its pure form, this colorless solid melts around 76 °C. For those with the enzyme to break it down (~40% of the population) the results appear in the urine usually within 15 minutes of ingestion. Interestingly, not everyone has the ability to smell the satisfying stench, thus complicating studies to determine why some have smelly piss and others do not. I am one of the lucky ones who can both produce copious quantities of metabolites such as methyl thioacrylate (among others) and delight in its pleasing perfume. For those of you deprived of this evolutionary gift, I have sympathy, as you will never truly enjoy the full experience of asparagus season. (edited 5/8/07, 5:28 pm to fix structures)

11 comments:

Chemgeek said...

I'm a big fan of asparagus as well. However, I have never experienced the malodorous piss. I may have to analyze my urine to see if I make the smelly metabolites or I just can't smell them. Time to pee into the GC/MS.

Anonymous said...

@greg: Your 3d structures are awesome. Could you tell me how you create them (which programme do you use)?

Greg the Chemist said...
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Greg the Chemist said...

Kutti,

I used Spartan '04 for Macintosh to make them. Wavefunction Inc.

Another good graphics program is Chimera (runs in Mac X11 or other platforms). It is available free from UCSF. UCSF Chimera It can beautifully render PDB files with lots of options. I used it to create my logo, for example.

Anonymous said...

@greg: Thx for the links. And how can I create a PDB file from say a structure I drew in Chemdraw? (Sorry for that silly question but I really don´t know). Maybe you could write a post "how to create good looking 3d models" or something like that ;-)

P.S. Did you receive my email?

Greg the Chemist said...

Kutti,

Well, I saved the chemdraw file as a MOL file. That could be opened with Spartan and then saved as a PDB file. I would guess you could search for a MOL to PDB program. There's probably some freeware or shareware that can read MOL and save as PDB.

PS, I did get your email (last Thursday). Apparently you never received my 2 replies? Check your junk box.

Anonymous said...
This comment has been removed by the author.
Anonymous said...

Oops, sorry for the delete above ...

I found a yummy asparagus for you. Try this at:

http://www.epicurious.com/images/
recipes/recipe_results/thumb/
photos/103567.jpg

Anonymous said...

Thanks for this post, I have been curious about my own asparagus piss for years and have never had it explained to me.

Anonymous said...

I have always wondered what that smell was. nice blog, btw.

Anonymous said...

Please learn to use its and it's properly. Really, for someone who has allegedly mastered E and Z, R and S, d and l, etc., how hard can this be?