Where's North? Ask Superoxide!


Many animals have a magnetic sense that tells them North from South. Migratory birds, salmon, or sea turtles migrate thousands of miles relying on this sense, but also animals staying closer to home like honeybees, newts or lobsters use it. Most likely, the animal magnetic sense is based on two types of receptors, one based on magnetite, another one on a protein called cryptochrome found in animal eyes, including human eyes. So why do we humans not enjoy the magnetic sense? A recent report, offers a very intriguing answer. In sensing the Earth's magnetic field, cryoptochrome relies on so-called redox reactions which exchange electrons between molecules. Such reactions are crucial for life, but can also be damaging; antioxidants are used by organisms, but also in pharmacology and as dietary supplements to keep the reactions in check. Apparently, cryptochrome recruits as a reaction partner in its magnetosensitive behavior a special form of molecular oxygen, namely its negatively charged brethren superoxide. For this purpose cryptochrome requires superoxide in low doses, which is good since superoxide, though arising in organisms and used in signaling elsewhere in the body, is actually toxic. The human body has an extremely efficient enzyme, superoxid dismutase, that keeps superoxid at a very low concentration level, apparently too low for human cryptochromes to capture it and tell North from South. Humans, somewhere in evolution, might have lost the magnetic sense, but gained longevity. More on our cryptochrome web site.

Magnetoreception through cryptochrome may involve superoxide. Ilia A. Solov'yov and Klaus Schulten. Biophysical Journal, 96:4804-4813, 2009.

12/31/2013 Mark Pajor, ECE ILLINOIS

Thomas Comberiate, who earlier this month earned his PhD in electrical and computer engineering at Illinois, won the Best Student Paper Award at EPEPS 2013, the conference on Electrical Performance of Electronic Packaging and Systems. The conference took place in San Jose, California, in October. Comberiate earned the award for his paper entitled “Modeling I/O Buffers Using X-Parameters,” co-written with his PhD advisor, ECE Professor Jose E Schutt-Aine.

Thomas Matthew Comberiate
Thomas Matthew Comberiate
Comberiate’s paper is noteworthy for its innovative application of X-Parameters* to model input/output buffers. X-Parameters, a superset of S-parameters, represent a modeling tool typically used to model amplifiers, mixers, and other microwave elements. One of the key benefits of X-Parameters is their ability to characterize non-linear components. Comberiate saw their potential to model non-linear input/output buffers, as is demonstrated in the winning paper. Traditionally, the signal integrity industry has used IBIS (Input/output Buffer Information Specification) to model input/output buffers, but the method has its limitations. “The problem with it is that it’s essentially a DC model, and we’re dealing with high frequency microwave circuits,” Comberiate explained, “so you need a high-frequency non-linear microwave modeling tool.” Comberiate’s paper determines that X-parameters can be that needed modeling tool.

EPEPS is an international conference on advanced and emerging issues in electrical modeling, analysis, and design of electronic interconnections, packages, and systems. It is jointly sponsored by the IEEE Components, Packaging, and Manufacturing Technology Society and the IEEE Microwave Theory and Techniques Society. While Comberiate had to leave the conference early to defend his dissertation, he appreciated the opportunity to attend and present at the conference.

After earning his BS and MS at Illinois, Comberiate transferred into Schutt-Aine’s research group while working on his PhD. “I switched into his group because he was doing interesting research,” said Comberiate. “Our group has nearly tripled in size over the last semester, and I think it’s because we’re trying to tackle more exciting problems.” Comberiate served as a TA in Schutt-Aine’s instructional lab, ECE 451: Advanced Microwave Measurements. In the class, students learned how to measure X-parameters. “We believe it’s the first time X-parameters have ever been taught in a classroom setting,” said Comberiate. Schutt-Aine received a gift from Agilent Technologies, who established the use of X-parameters, to help explore the possibilities of the modeling tool. Because of this association, Illinois is the first university to have access to a Non-linear Vector Network Analyzer (NVNA), the device that captures X-parameter measurements.

Schutt-Aine praised Comberiate’s work and expertise in the study and use of X-Parameters. “He’s been exceptional. He actually took this method and he developed it, he pushed it to a level that I did not anticipate. In fact, if I were to name five experts in the area of X-Parameters, I would definitely count him as one of them.” Now that he has earned his PhD, Comberiate is in the process of interviewing with several esteemed companies and research centers. In the meantime, he plans to take some time to travel, including a trip to walk a portion of the Camino de Santiago in Spain in the spring.

Comberiate and Schutt-Aine are confident that further progress in the modeling of input/output buffers will build on their research of X-Parameters, and that more researchers will harness the capabilities of X-Parameters for out-of-the-box applications. Schutt-Aine and his research group continue their research and the use of the NVNA equipment. He said, “There are a lot of challenges ahead, but we’re very excited about not only having the equipment but also helping make some contributions to the industry, on something that we think would potentially be very useful.”

*X-parameters is a registered trademark of Agilent Technologies. The X-parameter format and underlying equations are open and documented.