22 October 2019 Hasan Demirci


Speaker: Hasan Demirci
Koç University
Title: Ambient-Temperature Serial Femtosecond X-ray Crystallographic Studies of Biomacromolecules
Date: October 22, 2019
Time: 14:30
Cookie & Tea: SCI 103, 14:15
Place: SCI 103
web: https://physics-seminars.ku.edu.tr/


High-resolution ribosome structures determined by cryo X-ray crystallography have provided important insights into the mechanism of translation. Such studies have thus far relied on large ribosome crystals kept at cryogenic temperatures to reduce radiation damage. Here I will describe the application of serial femtosecond X-ray crystallography (SFX) using an X-ray free-electron laser (XFEL) to obtain diffraction data from ribosome microcrystals in liquid suspension at ambient temperature. 30S ribosomal subunit microcrystals programmed with decoding complexes and bound to either antibiotic compounds or their next-generation derivatives diffracted to beyond 3.4 Å resolution. Our results demonstrate the feasibility of using SFX to better understand the structural mechanisms underpinning the interactions between ribosomes and other substrates such as antibiotics and decoding complexes. We have also collected full dataset from the dimer of large (50S) ribosomal subunit in 47 minutes of beamtime at the CXI instrument using less than 50 microliter of sample. This structure is the largest one solved to date by any FEL source to near atomic resolution (3 MDa). We expect that these results will enable routine structural studies, at near-physiological temperatures, of the large ribosomal subunit bound to clinically-relevant classes of antibiotics targeting it, e.g. macrolides and ketolides, also with the goal of aiding development of the next generation of these classes of antibiotics. Overall, the ability to collect diffraction data at near-physiological temperatures promises to provide new fundamental insights into the structural dynamics of the ribosome and its functional complexes.

 Short Bio:
I am a new member of Koc University MBGE department, a member of the Biosciences Division at SLAC National Accelerator Laboratory and also affiliated with Non-Periodic Imaging group at Stanford PULSE Institute. I completed my B.S. at Bosphorus University in 2002 and later obtained a Ph.D., in Molecular Biology, Cell Biology and Biochemistry at Brown University in 2007. My research focuses on structural biology of mutant prokaryotic ribosomes, where I am interested in characterizing the function and dynamics of these mutants, with an eye toward answering questions in structure and dynamics of ribosomes which are resistant to some of today’s commonly-used antibiotics. My current research efforts also include methods development for time-resolved ambient-temperature X-ray crystallography of large and challenging biomacromolecules at 4th-generation light sources like the Linac Coherent Light Source at SLAC.