Following an early commissioning stage, XChem crystallised its core xray collection protocol as 180 degrees rotation in 60 seconds, which provides PanDDA with good datasets. But what has never been fully characterised is the lowest dose per crystal required for PanDDA to work. XChem now has an established hit rate profile where, based on our core xray protocol, we expect between 8 and 40 fragment hits out of the standrad supply screen of 400 fragments from the DSIP library (2% to 10% hit rate using the Diamond, SGC and Enamine fragment library poised for follow up [cox et al 2017]).
In a short series of posts I will tell my journey to arrive at the first round of xray dose optimisation, notably to reduce the core expriment to 30s per 180 degree rotation, currently (December 2018) at its first pilot runs as a protocol after 3 rounds of characterisation experiments.