Barrett has been doing research with Dr. Petersen, and at the final SIP session Barrett said he will be employed by her lab full time starting next semester. On Monday of this week, Dr Petersen talked with us in class about her research a bit, but she focused mainly on her goal of synthesizing small chemical building blocks with chiral stereocenters which can be used to synthesize larger molecules of medical importance.
At the seminar Barrett presented third, and from what I heard, the research that he has been doing in Dr Petersen's lab did not involve any stereocenters, but instead involved substituting an aromatic compound with COOH groups. The commercially available aromatic compound they were starting with was:
They wish to synthesize each of these three molecules:
 |
| These are drawn from memory, so please correct me if I got them wrong! |
Once those compounds are synthesized they will be shipped to Virginia Tech so that they may be used in the construction of semiconductors. The collaborator at Virginia Tech who needs these compounds is a friend of Dr Petersen's from graduate school.
Dr Petersen explained the specifics of the semiconductors to me after the seminar, but I'm afraid most of it was over my head. MOFs (Metal Organic Frameworks) were mentioned during Barrett's talk, and online I found some references to MOFs being used as semiconductors, so it may be that these compounds they are creating will act as ligands in metallic compounds like the ones we worked with in chapter 11. Speculation aside, there is reason to believe that molecules like those shown above will have qualities useful in the production of semiconductors, and once they are isolated, they will be tested at to see if they function as expected.
As of last Friday, the first compound with the COOH groups substituted para on the second ring of tetracene had been successfully created. It was a rust colored solid. The other two compounds have not yet been made. Barrett proposed a mechanism but he sped through it too fast for me to copy it down. Sorry! There was a bridge formed between the two carbons on ring two of tetracene, perhaps with a Diels-Alder reaction. Once the bridge was formed across the two desired carbons, it could be treated with an oxidizing agent which would lead to the desired carboxyl groups. (I'm working from memory here, so I'm sure there will be some corrections from Dr Petersen in the comments.)
The following compound was used for something, but I'm not sure what it was, and I couldn't find any information about it online:
When creating that first molecule, Barrett put some reagents together, and then left them in the microwave for 30 hours. (There was some laughter at the top of the room at this part, but Barrett stared them down like he didn't see what was so funny.) Along with the desired compound, an impurity was formed. I think the impurity was substituted twice, on both ring 2 and 3. Barrett worked hard to remove that impurity, and there was a 77% yield. After this there was a reflux with 40% NaOH at 120 degrees Celsius for 2 hours. Oxidative cleavage (or splitting the bridge) was carried out using periodinane. Then Pinnick oxidation was used to form the carboxyl groups.
Dr Petersen and Barrett are trying to manage the workup so that yield and purity will be improved. There were a few helpful suggestions from the audience after Barrett's presentation.
Because this summary is already getting way too long, I'll include descriptions of the other four undergraduate research presentations in the comments of this post if anyone is interested.
-EK
The first person presenting was named Jamie Tran. She is from Vietnam. She is a Biochem major who plans to go to pharmacy school. Between her accent and her soft voice it was difficult to make out what she was saying sometimes.
ReplyDeleteJamie was presenting research on Photosystem II. Iodine and Nitrate are both necessary for proper Photosystem II functionality. It is known that certain ions (Azide Nitrite and Iodide) inhibit the function of Photosystem II, and Jamie wanted to figure out why. She thought that maybe the reason was because those ions would donate their electrons, and she tested her hypothesis, but it was found that electron donation was not the reason for the inhibition. So this mystery is still waiting to be solved!
The second undergraduate researcher was named Scott and he is apparently very good at impressions. I have yet to see any proof of this though.
ReplyDeleteScott was doing research on alkaloid production of endophytes. Endophytes are fungi that grow inside plants, and they often produce chemicals which help the plant survive, such as loline alkaloids which are insecticidal. GCMS (gas chromotography mass spectroscopy) can be done on loline alkaloids.
Scott first attempted to isolate loline alkaloids from sleepy grass, but failed to do so. He was puzzled by this for a while, until he found in the literature that the endophytes in sleepy grass do not produce alkaloids. So he switched his focus to meadow fescue, a species whose endophytes definitely do produce loline alkaloids. Interestingly, meadow fescue's endophytes are in the same genus as the endophytes in sleepy grass that do not produce alkaloids.
A new technique, HILIC (hydrophilic interaction liquid chromatography), was used to examine the 7 alkaloids obtained from meadow fescue. High Resolution Mass Spectroscopy was also used. The alkaloids were identified. Atmospheric Pressure Chemical Ionization as well as another technique that did not give as good of results were used.
The fourth presentation was given by Obeth Gutierrez. His research focused on trying to target particular organs in the body of mice with gold nanoparticles. Of course, the mice are supposed to be a stepping stone on the path to applicability in humans. Gold nanoparticles have potential applicability in cancer treatment.
ReplyDeleteThe organ of interest in this study was the brain.
Two different types of gold nanoparticles (ascnp and pronp) were inserted into the mice at the base of their tail. By the time Obeth gets involved, the mice have already been dosed with the nanoparticles, killed, and dissected. Obeth basically received labeled bags of mice organs.
He took all of the organs in the same category (for example, all the livers from the mice dosed with ascnp and killed exactly four hours later) and digested them in nitric acid overnight. Processing the organs in this way effectively took the average of the concentration of nanoparticles found in each organ under particular circumstances. An autosampler was used to analyze the digested samples, and then the data was normalized. A hollow cathode lamp with wavelength of 242.8 nanometers was used and the sample was heated.
They found that up until about 100 parts per billion, it didn't matter which nanoparticle was used. Neither of the nanoparticles were retained well in the brain, unfortunately, but the ascnp was retained at a slightly higher effectiveness. A surprising result from this analysis was that the spleen had the largest retention of both sorts of nanoparticles. In the literature, other studies have seen the liver absorbing the most nanoparticles.
If this research is to continue, they will need more replicates in the future. As it stands now, if there is only one freak mouse retaining all the gold in his spleen but nowhere else, it is enough to throw off all of their data.
I am always fascinated when reading about strides towards cancer research. This presentation was most interesting to me, especially the part about the spleen having the highest uptake of the nanoparticles. However, I also see that the liver, in other literature, is seen to have the most absorbancy of nanoparticles. Here's a thought. I know the spleen is a large reservoir for monocytes (WBCs used for tissue healing and immune health). If the nanoparticles are to help with ridding the body of cancerous cells, could it be a reason why the spleen has the largest retention of these particles? Just wondering.
DeleteThis comment has been removed by the author.
ReplyDeleteThe final presenter was Phillip Drum from Hickory, NC. He was studying a sillus bacteria that is uniquely able to do a defluorination reaction. The human body also has an enzyme that can be used to defluorinate compounds picked up from the environment, but it is membrane bound, so it is not convenient to study.
ReplyDeleteDefluorination reactions are important to study because many of the chemicals with fluorine that humans are releasing into the environment may be toxic.
Haha Barret Suit was not that snazzy!! But I did like his glasses!!
ReplyDelete