Aliens from chemistry notes

Well, this last week has been a hard one--Fortunately I'm far enough along in my graduate career that I don't have to deal with the stress of final exams, but my body decided to play tricks on me anyway. After dealing with the stomach flu last week, this week I've been suffering from a head/neckache. Since I'd had it for over 5 days, I decided to go to the student health center, which was a big mistake--for some reason, they thought I had meningitis (Normally I would put a wikipedia link there, but the picture that came up when I did that made me sick to my stomach, so today I'll leave the link out), and they sent me to the emergency room. The doctors there assured me that I was only suffering from a muscle spasm in my neck, gave me some pain killers, and left me with a hefty bill to pay. When they can't tell the difference between muscular pain and a deadly illness, I start to doubt the effectiveness of the university health care system....So that explains why my post today will be relatively light :o)

If you're like me, when you think of aliens, you think of little green men with saucer shaped eyes and strange metallic clothing. Why do we always imagine aliens to be green--Is this really an accurate representation of animals or plants in other solar systems? Well after a lengthy review of photosynthesis on Earth, researchers at Rice University, Washington University, UIUC, and NASA have come up with a set of rules for predicting what colors might be photosynthetically relevant on other planets. Photosynthetic pigments evolve over time in sync with the atmosphere of a planet and the characteristics of its parent star; it is proposed that they have peak absorbance at the blue and red ends of the atmospheric transmittance window for light harvesting, as well as at the wavelength of peak incident photon flux. Thus, if we know the patterns of incident radiation for other stars, we can begin to predict what kind of photosynthetic machinery might be necessary on those planets, as well as the color of these photosynthetic pigments. So we can basically predict what color the trees might be on Jupiter.

Cool, huh?

I first read about these articles on heise.de, but a nice summary can also be found here on the Goddard Institute for Space Studies (part of NASA) website, with reprints of the two Astrobiology papers here and here.

Random observation from chemistry notes

Why does it disturb me so much that chemistry.com is not a chemistry website at all, but an online dating community? That is just wrong.

Going Decaf... from chemistry notes

Several months ago, Justin P. Gallivan gave quite an entertaining seminar for the chemical biology department. While I'm officially a member of the organic division, I really enjoy the biological side of things, so I try to attend these seminars as often as possible (or sometimes I attend them when my boss sends out an email "please attend," which really means "required seminar"). If I remember correctly, Prof. Gallivan did a little "bacteria dance," and if a speaker goes that far to get our attention, he has my respect :o) His lab actually has done some extremely interesting work, and I've been waiting for a publication to come out ever since that seminar.

Last week, the article "Guiding Bacteria with Small Molecules and RNA" finally appeared in JACS. E. coli have 5 chemoreceptor proteins and thus can maneuver their way through complex chemical environments. While they naturally perform chemotaxis toward 30+ compounds, it would be useful in terms of bio-nanotechnology to reprogram these bacteria to respond to new and unique chemical signals. The pathway responsible for converting chemical ligand binding into a change in direction of the bacteria consists of 6 chemotaxis proteins, with the protein known as CheZ ultimately responsible for bacterial motility. With this in mind, Shana Topp from the Gallivan group created a theophylline-sensitive synthetic riboswitch to control translation of CheZ; without theophylline, the conformation of mRNA prevents translation of CheZ, forcing the bacteria to tumble in place. Once theophylline is added to the mixture, the mRNA adapts a different conformation in which the ribosome binding site is open, which allows for expression of CheZ and forward movement of the bacterial cells. Caffeine, which has a structure similar to that of theophylline, did not elicit a response from bacteria, indicating that the observed changes in bacterial motiliy are dependent on the riboswitch. As Topp and Gallivan jokingly state, "E. coli pick decaf!"