50-NANOSECOND ENCODING OF SR PROTEIN CRYSTALLOGRAPHY DETECTORS

X-RAY CRYSTALLOGRAPHY IS THE PRINCIPAL TECHNIQUE CURRENTLY EMPLOYED TO STUDY THE STRUCTURE OF BIOLOGICAL PROTEINS. THESE PROTEINS ARE KNOWN TO ASSUME INTERMEDIATE STRUCTURES IN THE COURSE OF BIOCHEMICAL REACTIONS SUCH AS ENZYME ACTIVITY; THE DETAILS OF THESE CONFORMATIONAL CHANGES ARE CRITICAL TO A PRECISE UNDERSTANDING OF THE RELATIONSHIPS BETWEEN CHEMICAL STRUCTURE, PHYSICAL TOPOLOGY, AND BIOCHEMICAL ACTIVITY. BECAUSE THE INTERMEDIATE STATES ARE TRANSIENT, TIME-RESOLVEDCRYSTALLOGRAPHY IS REQUIRED TO STUDY THEM. THERE WILL BE SUFFICIENT X-RAY FLUX AVAILABLE AT THE NEXT GENERATION OF STORAGE RINGS TO CARRY OUT THESE STUDIES IN THE TIME REGIME BETWEEN MILLISECOND AND NANOSECOND, PROVIDED THAT INTEGRATING 2-D DETECTORS CAN BE DEVISED THAT CAN BE READ OUT IN THE TIME BETWEEN THE 100-PSEC X-RAY BURSTS PRODUCED BY THE STORAGE RING AT ABOUT 100-NSEC INTERVALS. HIGH-QUALITY INTEGRATING DETECTORS EXIST, IN THE FORM OF CCDS FOR EXAMPLE, BUT THEY ARE LIMITED BY THEIR SEQUENTIAL READOUT SCHEMES. THIS WORK WILL ADDRESS THIS PROBLEM BY DEVELOPING A READOUT SCHEME THAT CAN READ OUT ALL THE PIXELS OF A 2-D DETECTOR IN PARALLEL (1 FRAME) AND STORE THEIR CONTENTS IN TEMPORARY MEMORY UNTIL THE END OF AN EXPERIMENT (ABOUT 100 FRAMES), WHEN ALL THE DATA CAN BE TRANSFERRED TO PERMANENT STORAGE AT LEISURE.