Thank you cell phone typing for the inadvertent prophanity. Sorry! On Dec 9, 2014 1:00 PM, "Artem Evdokimov" <[email protected]> wrote:
> Generally fab geometry presents problems for mr due to variable > interdomain angle. Assuming your sg is correct and this is not a twin, i > would try searching at 4 or even 5 a resolution. I would not reject the > chance that you have high solvent content, so you might have fewer > molecules in au than expected from vm estimates. We recently solved a whole > bunch of structures with large unit cell dimensions and high solvent > content in the 75% or even 82% range. All had issues with resolution, > freezing, and twinning - similar to shat you describe. In a few cases we > screened over 35 crystals (of the same protein variant, same condition, > just repeats) to find one that diffracted beyond 4a. Don't give up! May the > pork be with you. > > Artem > On Dec 9, 2014 12:32 PM, "Mo Wong" <[email protected]> wrote: > >> Hi all, >> >> I’m stuck on a rather complex molecular replacement problem. The crystals >> are of an antigen-Fab complex totaling ~67 kDa (waiting to confirm using >> PAGE gel). They diffract to ~3.5A at the synchrotron and process in C2 with >> dimensions 220x130x230 and beta at 103 so it looks like there are round >> 9to12-ish copies in the ASU. The overall Rmerge is high at ~25% with I/sig >> cutoff ~2 and redundancy of 5; however, at 4.5A this drops to ~15%. >> Furthermore, processing in P1 gives similar Rmerge values too. >> >> Self-Patterson doesn’t suggest translational symmetry, but the >> self-rotation function (SRF) suggests high NCS (see below/attached). >> >> I’m hoping the SRF might be helpful in trying to confirm/dismiss C2 is >> the likely space group, and perhaps suggest a logical assembly with the ASU >> (I see strong 2-fold and 3-fold NCS operators suggesting to me dimeric >> trimers or vice versa - however, I’ve never had to really analyze SRFs in >> the absence of a mol. rep. solution so my interpretation could be wrong). >> >> Anyway, any help to bringing a molecular replacement solution closer to >> reality would be appreciated. >> >> Thanks! >> >> [image: Inline image 1] >> >
