By Dan Starr
The past three years I had the opportunity to teach the incoming BMCDB students in the rotation course. I was lucky to have great partners in this endeavor, Ted Powers for the first year, and Jodi Nunnari the past two years. The following are some of the highlights from my experience.
Far and away the best thing about teaching this course is the way I got to know the whole class, and watch them as they work hard to constantly improve their skills! I now know the students of these three classes better than any faculty member in BMCDB, and I can say with confidence, we have an awesome group of students!
We made some significant changes to the curriculum of MCB220L. I think the most important change was the requirement of writing an NSF-style grant proposal at the end of each rotation. This not only teaches the students how to write grants, but more importantly, gets them to think about the big picture before joining a lab. I feel this exercise was very successful. Especially to Amy, Nadia, and Alex, who turned their assignments into NSF fellowships—congrats you three! For all the other students, I think the assignment made you better scientists.
The second addition to the curriculum was the chalk talk. This is an important means of scientific communication that was completely new to the students. I hope that with the experience (and stress) of the chalk talks, now any of my students can give you a 5-10 minute version of their research at a chalkboard in a chance encounter in the hallway.
There were of course humorous moments to teaching the class—Ralph’s “pointer” comes immediately to mind. The other occurred at the MCB NIH training grant retreat at Fallen Leaf Lake when all the then second years cornered me after my talk. I still can’t believe I forgot the hypothesis slide!
In all, teaching MCB220L was one of the most rewarding things I have done as a professor! Watching my former students give a talk or hearing about them get a grant fills me with pride. We have an awesome group of students! I’m sure Bob, Elva, and Enoch will continue the high quality experiences of the class. Have fun!
A note from V&E’s resident veteran, Luke Bohanan
All,Before we set off in our different directions to enjoy (or work through) this Memorial day weekend, I would like to take a moment of you time, to get on my soap box.Yesterday I went with a few of my Student Veterans club members to the Memorial Union to lay flowers at the Aggie veterans memorial tucked away in the corner next to the fireplace in the Griffin lounge in the MU. There, a stainless steel plaque lists the names of 134 UC Davis Graduates that were killed in combat from World War I through 2006, accompanied by a book encased in glass that talks about each service member. I had never realized that the MU, the Memorial Union, was originally dedicated to these heroes, and I realized how easy it is to forget what memorial day is all about. For me, the break is always bitter sweet. Every year since 2003 I have lost at least one of the original 400 some odd soldiers that I crossed the boarder with in Iraq, many of whom I worked closely with, and all of whom I have called my brother.So, if you have time this weekend, or later on, I invite you to go down to the MU Griffin lounge and take a moment to think about those who sacrificed so much to stand up when the call came out. Also, if you are at a party, bbq, camping trip, or stuck behind your computer, take a moment, and take a moment and have a drink for all the great men and women who fought so hard and are no longer here to drink with us.Here is a link to the article about the re-dedication of the wall, if you are interested.http://dateline.ucdavis.edu/dl_detail.lasso?id=8836Thank you, and have fun this weekend.
Contributed by Alex Gulevich
Imagine preparing for an elegant night out at a ballroom. Everyone in attendance will be wearing their finest evening gown or tailor-made suit, and most likely many of these people will be wearing their favorite perfume or cologne, say three sprays of Chanel No. 5 or a men’s fragrance from Dolce and Gobanna, These stimulating bouquets of aromas arouse our olfactory system, and those wearing the higher end fragrances will stimulate our senses throughout the night, while those wearing the lower end fragrances will go amiss and fail to last. This is because higher end fragrances have an additive within it that prolongs the lifetime of their scent, and this additive is derived from the dyspeptic discharge of a sperm whale, or in a more crude of way saying it, whale barf.
Ambergris, a French compound word that translates to grey amber, is a smelly viscous black discharge from the sperm whale’s intestinal tract. A sperm whale’s diet consists primarily of the elusive giant squid, where they dive up to 3000 meters to chow down on fresh deep-sea calamari. Although a hearty meal, these giant squids also have giant indigestible beaks. The whale must produce ambergris in its intestine to help aid in its passage as fecal matter. However, if the ambergris mass becomes too large to pass, the whale will regurgitate (experts emphasize this is assumed, no one has actually observed this) the ambergris with beaks and all. This freshly vomited mass is less dense than seawater and floats to the surface where it is weathered by the sun and the salt from the sea itself, turning into a solid waxy grey substance. Its fate is then left to the tides and eventually washes ashore to Pacific, Atlantic and Caribbean coasts. Aimless and profiteering beachcombers then stroll along the coast and manually harvest the weathered ambergris, to be sold at a market value of $10 per gram (gold is $53 per gram) with the average decent sized lump selling for $6000.
Fresh ambergris smells like fresh fecal matter. It’s speculated that Captain Ahab from Herman Melville’s Moby Dick was able to track sperm whales by using his nose and following this foul odor. However, as ambergris matures its loses its displeasing odor and gains sweeter earthy overtones. Once matured, crude ambergris is treated with heat and alcohol to extract the white ambrein crystals that lie within, which is then further oxidized to ambrox, the main additive in higher end fragrances, and ambrinol. The fragrance molecules in perfumes and colognes naturally have high rates of vaporization, thus a short lifetime. However, when ambrox is added with these molecules their aromas persist and have longer lifetimes. This is because the fragrance molecules are lipophilic and have a high affinity for ambrox, which prevents the molecules from entering the vapor phase all at once and disappearing into thin air. This is why ambrox is highly sought after, but is difficult to obtain because of its scarcity and it’s a byproduct of an endangered species, which technically makes it illegal to harvest in the United States. However, Jörg Bohlmann and his research group at the University of British Columbia have found a new way of obtaining ambrox without making a trip to the beach, or the courts.
Diterpenoids serve as chemical defense molecules produced by coniferous trees and protects them against herbivores and pathogens, and one such compound is cis-abienol. This compound is synthesized in the bark of the balsam fir and is commercially valuable because it’s a precursor two steps removed from chemically synthesizing ambrox. Bohlmann’s group recently identified a diterpene synthase gene, cis-abienol synthase (CAS), being actively expressed in the bark tissue of the balsam fir. Since cis-abienol has the highest abundance in bark tissue, looking at gene expression in the bark made most sense. These researchers were able to create a transcriptome of actively transcribed genes and assemble full-length cDNA sequences of candidate CAS genes by comparing sequence homologies of known diterpene synthases. They then took these genes and expressed them in Escherichia coli to test for cis-abienol biosynthesis, and of the four identified candidates, they conclusively found one candidate gene specifically producing cis-abienol from the appropriate precursor molecules, and uncovered the function of a previously unknown enzyme.
By discovering this enzyme, this opens up the possibility of engineering a microorganism, or perhaps a plant crop, to biosynthesize ambrox through metabolic engineering. People may feel more comfortable knowing that they are spraying themselves with ambrox from a plant product rather than sperm whale vomit, but the future discussion here centers around realizing the potential of metabolic engineering to biosynthesize valuable chemicals that are otherwise difficult to obtain. As the list of characterizations of novel enzymes grows, so do the possibilities of how we can design microorganisms or plant crops as living factories to make products with commercial value for human consumption. But despite all this, if anything is to be learned here, it’s that a little sperm whale barf can go a long way, at least with perfumes and colognes.
Read the original manuscript published in the Journal of Biological Chemistry.