Ronald C. Hamlin

2012 Charles Supper Award Lecture by Ron Hamlin

- An Update

Editor's Note: Following Ron's talk at the 2012 Boston ACA meeting, some questions were asked about the status of the dual-mode pixel array detectors that he had described there. A video of Ron's lecture is available on the ACA History website, and a transcript will be coming there soon. Here's an update from Ron on those detectors.

The 512 by 512 HF-262 k pixel 'proof-of-principle' dual mode HF-262 detector was delivered to Wayne Hendrickson's beamline X4A at NSLS in September of 2013 where, in spite of its relatively small area for protein crystallography, the detector was used to collect good-quality data from crystals of several standard proteins in both the pure pulse-counting mode and in the charge-ramp mode. Remarkably, one data set from crystals of insulin collected at 7 keV with the detector pixels in charge-ramp mode was good enough to yield an ab initio structure solution with phasing obtained only from the sulfur anomalous scattering  (sulfur-SAD).

The much larger 2 k by 2 k HF-4M (4 million pixel) dual-mode pixel array detector specified in our contract with Wayne Hendrickson was successfully delivered to APS (Chicago) beamline 24ID-E (NECAT) in December of 2015 where it has been used to collect protein crystallographic data for several new protein structures, some using seleno-met phasing. Quite remarkably one data set from crystals of thaumatin collected in December with the HF-4M detector pixels set to the charge-ramp mode was accurate enough to yield an ab initio sulfur-SAD structure solution using X-rays of 12.4 keV. At this relatively high X-ray energy the anomalous scattering signal from sulfur is extremely weak and so it requires very accurate spot intensity measurements to get adequate structure factor phasing information from only the sulfur atoms in the structure. This HF-4M detector will be moved to Wayne's new beamline at NSLS II sometime in 2016 when the new beamline is completed.

Ron Hamlin