_______________________________________________

Friday, February 3, 2012

David Schuller, Staff Scientist
MacCHESS, Cornell University

Abstract:  Dr. Schuller will be discussing 2 papers which are listed below:
1)  "X-ray Structure of Snow Flea Antifreeze Protein Determined by Racemic Crystallization of Synthetic Protein Enantiomers", Brad L. Pentelute, Zachary P. Gates, Valentina Tereshko, Jennifer Dashnau, Jane M. Vanderkooi, Anthony A. Kossiakoff, and Stephen B. H. Kent; J Am Chem Soc, 130, 9695-9701 (2008) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2719301/?tool=pubmed

2)  "Single-wavelength Phasing Strategy for Quasi-racemic Protein Crystal Diffraction Data", MR Sawaya, BL Pentelute, SB Kent, and TO Yeates; Acta Crystallography. Sec D, 68: 62-8 (2012) http://scripts.iucr.org/cgi-bin/paper?S0907444911049985

_______________________________________________

Friday, January 27, 2012

Darby Harris, Postdoc
Department of Plant Pathology and CHESS, Cornell University

"Cellulose Microfibril Crytallinity is Reduced by Mutating C-terminal Transmembrane Region Residues CESA1-A903V and CESA3-T942I"

Abstract:  The mechanisms underlying the biosynthesis of cellulose in plants are complex and still poorly understood. A central question concerns the mechanism of microfibril structure and how this is linked to the catalytic polymerization action of cellulose synthase (CESA). Furthermore, it remains unclear whether modification of cellulose microfibril structure can be achieved genetically, which could be transformative in a bio-based economy. To explore these processes in planta, we developed a chemical genetic toolbox of pharmacological inhibitors and corresponding resistance-conferring point mutations in the C-terminal transmembrane domain region of CESA1-A903V and CESA3-T942I in Arabidopsis thaliana. Using 13C solid-state nuclear magnetic resonance spectroscopy and synchrotron X-ray diffraction, we show that the cellulose microfibrils displayed reduced width and an additional cellulose C4 peak indicative of a degree of crystallinity that is intermediate between the surface and interior glucans of wild-type, suggesting a difference in glucan chain association during microfibril formation. Consistent with measurements of lower microfibril crystallinity, cellulose extracts from mutated CESA1A903V and CESA3T942I displayed greater saccharification efficiency than wild-type. Using live-cell imaging to track fluorescently labeled CESA, we found that these mutants show increased CESA velocities in the plasma membrane, an indication of increased polymerization rate. Collectively, these data suggest that CESA1A903V and CESA3T942I have modified microfibril structure in terms of crystallinity and suggest that in plants, as in bacteria, crystallization biophysically limits polymerization.

_______________________________________________

Friday, January 20, 2012

Etienne Forest
KEK

Abstract:  In 1987, I tried to explain the difference between a horizontally integrated code and a vertically integrated tracking code. Today, I like to call them democratic and totalitarian. The concept of the totalitarian code was perhaps invented by R. Talman who referred to TEAPOT as “exact”.  Embracing Talman’s concept, I added the claim that Courant-Snyder theory is its universal doctrine. Courant-Snyder is the party propaganda in its purest form.

I will explain these concepts using spin as an example, the delusional papers that we published, and “PTC“ (the North Korea of codes).

_______________________________________________