> Anyway, with the improvements in software we may have reached a stage > where the limitation of the search model is not whether or not you can > find a MR solution, but whether or not that solution is going to help > you determine the structure. What you can and can't get away with > depends on the resolution of your native dataset and the power of > density modification, in particular the presence/absence of NCS.
I'll second this (although I'm a bit late to the conversation). When I was doing some test runs on phaser (using a known structure with experimental amplitudes), I got good solutions using a partial model that was only 10% of the total mass (which I only tested because I had my script incorrect...I wouldn't have expected this to work). These agreed with the known position, allowing for origin shifts. Even allowing for the fact that this is with 100% sequence identity, I was very impressed by phaser. > It's always worth a try but if finding a MR solution is a challenge you > should consider how useful a solution, if found, is going to be. An MR solution that's very incomplete could still be very useful for anomalous/heavy atom site location (no issues with alternative origins or handedness), particularly with weak sites. 10% total mass would probably give too much noise in anomalous difference fourier, but ~40-50% seems to work fine. Pete Pete Meyer Fu Lab BMCB grad student Cornell University
