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March 20, 2008


UPJ prof earns patent

Maddu Karunaratne, an electrical engineering technology faculty member at Pitt-Johnstown, was awarded a U.S. patent for methods for estimating power requirements of circuit designs. The patent, No. 7,313,510, was issued Dec. 25, 2007.


Retinal coding of information described

The retina performs an information-coding function once thought to be performed by the brain, according to research by a Pitt-Bradford professor.

A paper co-authored by David Merwine, assistant professor of biology at Pitt-Bradford, and published in the journal Visual Neuroscience, describes experiments that investigate the nature of information coding in the retina. Surprisingly, individual optic nerve fibers from the retina do not seem to carry completely separate information. Instead, some information is encoded by synchronizing the activity across fibers.

“This study demonstrates that the retina performs a function once thought to occur only in the brain,” Merwine said.

The work was performed in collaboration with researchers at the University of Southern California and the University of Alabama at Birmingham.


GlpD enzyme mapped

Using X-ray crystallography, researchers at the School of Medicine led by structural biologist Joanne I. Yeh have become the first to decipher the three-dimensional structure of a membrane-bound enzyme that plays a crucial role in glycerol metabolism. Their discovery, reported in the March 4 issue of the Proceedings of the National Academy of Sciences, could lead to advances against obesity, diabetes and other conditions.

Glycerol is an essential source of energy needed to help drive cellular respiration. In addition to powering some of the most central reactions of the body, glycerol also provides key precursors needed to regulate fatty acid and sugar metabolism.

Figuring out the complex ways that cells break down or produce glycerol and use this vital chemical could be critical to combating obesity, diabetes and other chronic disorders. Recent findings also have linked glycerol metabolism to cellular processes related to aging, infectivity and other energy-related illnesses.

The protein structure Yeh’s team solved is a large enzyme called Sn-glycerol-3-phosphate dehydrogenase, or GlpD. GlpD’s main role in the cell is to remove hydrogen from a form of glycerol called glycerol-3-phosphate to generate dihydroxyacetone phosphate, a biochemical compound vital to the process of metabolizing glycerol. In the process, electrons are produced and shuttled to a molecule called ubiquinone that works to power cellular respiration.

The team developed and used peptide-based detergents called “peptergents” to separate GlpD from cell membranes and keep it in an active form to ensure that their studies revealed a physiologically relevant enzyme structure. They then used detergents to crystallize the enzyme and screened the protein crystals in Pitt’s new X-ray crystallography facility, directed by Yeh. Next, they applied beams of high intensity parallel X-rays to the protein crystals to collect the diffraction data necessary to determine the protein’s atomic configuration. These experiments were performed using cyclic particle accelerators at the Argonne National Laboratory in Illinois and the Paul Scherrer Institute in Switzerland.

Based on the structural information acquired in their study, Yeh’s team proposed mechanisms by which the enzyme carries out its fundamental metabolic reaction.

“These findings and data help to fill an important scientific and technical gap in the structural field and present new information and ideas about how the enzyme works and the importance of the cell membrane in stabilizing the enzyme and in processes related to energy production,” said Yeh, who published the paper along with postdoctoral research associate Unmesh N. Chinte and research assistant professor Shoucheng Du of the Department of Structural Biology.

With the GlpD structure in hand, Yeh’s team is examining how changing certain amino acids in the enzyme affects its function and fold. These studies target the roles that these specific amino acids play in enzymatic function and regulation of activity. These questions are important because glycerol metabolism is a key link between sugar and fatty acid metabolism.

The Pitt group also has determined the atomic resolution structures of other enzymes involved in mediating glycerol and oxidative metabolism. In all, these structural results provide some of the first three-dimensional views of these highly important proteins and enzymes.

A link to the online paper is available at


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