Re: [ccp4bb] Heterogeneity during purification

Theresa, Are there any cysteines in your protein? Tony. On 9 Jul 2013, at 05:01, Theresa Hsu wrote: > Dear all > > I am working on a 30 kDa membrane protein which forms a functional dimer. The > protein is His-tagged at N-terminal. In small scale expression screening from > whole cells, the

[ccp4bb] crystallographic association

Hi everyone, I just wanted to ask if there is a professional association for crystallographers in the US. When I googled it I came across The American Crystallographic Association. Is that the only one? Thank you, Maher

[ccp4bb] Heterogeneity during purification

Dear all I am working on a 30 kDa membrane protein which forms a functional dimer. The protein is His-tagged at N-terminal. In small scale expression screening from whole cells, there is only a single band on Western blot at 30 kDa. But, after purification, additional bands appear at 60 and 120

[ccp4bb] Scientific Webinar Series: Cancer Research Technologies and TTP Labtech- July 16

Dear All, Our next scientific webinar will be on July 16th (3 PM London, 10 AM New York) with Dr. Andrew Turnbull, Cancer Research Technologies. Dr. Turnbull will discuss developing robust crystallography platforms for iterative protein-ligand complex structure determination to support structure

Re: [ccp4bb] ctruncate bug?

On Jul 7, 2013, at 1:44 PM, Ian Tickle wrote: > > On 29 June 2013 01:13, Douglas Theobald > wrote: > > > I admittedly don't understand TDS well. But I thought it was > > generally assumed that TDS contributes rather little to the > > conventional background measurement outside of the spot (so S

[ccp4bb] AW: [ccp4bb] AW: [ccp4bb] help identifying ligand

Dear Ed, For me, 3 mM is a significant concentration. If you have another crystal left, you could transfer it to a storage buffer without azide and collect a data set and see if the density disappears. A very small molecule, non-covalently bound on the outside of the protein should disappear in

Re: [ccp4bb] AW: [ccp4bb] help identifying ligand

Thanks all, the pH is 6.7, azide is 3 mM, and there is no added ammonium. I could get away with modeling as two waters since the separation is well above the 2.2A that gets flagged as a clash in the PDB, still it's close enough to suggest that two waters is not really what's there. Enrico Stura w

Re: [ccp4bb] AW: [ccp4bb] help identifying ligand

Dear CCP4BB, The most likely components are those at the highest concentration in the crystallization or cryosolution. And a few wild ideas to continue the discussion that is very important as the ligands are always very difficult to identify. Example: If you have 1.5 M ammonium sulfate y

[ccp4bb] AW: [ccp4bb] help identifying ligand

Dear Ed, What is the pH of your crystallization buffer? If it is acidic, either the azide or the carboxylate may be protonated. Also the local environment of the carboxylate can make a hugh difference in PKa. You could also use some Bayesian logic: given the elongated linear density, what else

[ccp4bb] modified amino acids in the PDB

Dear colleagues, We deposited protein structures with modified lysine side chains and were surprised that the PDB treats the modification as an independent molecule, with a “LINK” record indicating the covalent bond – instead of defining a modified residue (that’s what we had uploaded to the PDB).