Like Nat points out, I suspect they are phosphate crystals. I have seen those before.
And I agree 100% with Frank, for once. Why would I risk making any guesses no matter how "salt like" my crystals look after all the time it took me to clone, express, purify and crystallize my precious protein. It takes MUCH less time than all of that slog to stick the crystal on a beam and here are a few possible scenarios: (1) Clear diffraction spots spaced planets apart in case of salt (2) Protein like diffraction (3) Inconclusive "no diffraction" situation, which could indicate a million things including the possibility that your cryoprotectant was sub-optimal for data collection done using flash cryocooled/flash frozen crystals in a stream of gaseous nitrogen. Note of caution: I may take more time to plan the diffraction test (room temperature, cryoprotectant etc.) if I only ever got one precious crystal and was never able to reproduce the crystallization. Cheers, Raji On Fri, Feb 8, 2013 at 8:18 AM, Ed. Pozharski <[email protected]>wrote: > Patrick, > > Something related: > > > http://strucbio.biologie.uni-konstanz.de/ccp4wiki/index.php/Conditions_prone_to_salt_crystallization > > Truth be told, we recently had a major breakthrough with the peg/fluoride > condition I came to consider a useless salt crystal generator. So tables > like these are undoubtedly useful but do not reduce workload. :) > > This is also a rather interesting finding > > http://www.google.com/url?sa=t&source=web&cd=12&ved=0CDEQFjABOAo&url=http%3A%2F%2Fwww.aseanbiotechnology.info%2FAbstract%2F21021153.pdf&ei=N_kUUYfkBafV0gG09ICoAg&usg=AFQjCNE7C-m6IkLPUay9gEEM60yJF46ZQg > > Basically, presence of protein may induce salt crustallization. To me, > this means that diffraction pattern is the best indicator. Frank already > said exactly that, of course. > > Cheers, > > Ed. > > > > > -------- Original message -------- > From: Patrick Shaw Stewart <[email protected]> > Date: > To: [email protected] > Subject: Re: [ccp4bb] protein crystals or salt crystals > > > > Good morning Frank > > On a related idea, do you typically use a limited number of "buffers" > (buffer plus salt) for the final purification step of your proteins? > > If so, do you have a chart of where salt crystals may appear in the > screens that you use most often? Could you put that chart on your web site > to help the community? > > People could pick one of your standard buffer mixes to make their lives > easier later on. > > Best wishes > > Patrick > > > > > > On 8 February 2013 07:18, Frank von Delft <[email protected]>wrote: > >> Test the diffraction - that's the only way. But given the other junk >> in the drop, chances are they're salt. >> >> (And don't post 5Mb attachments, please.) >> >> >> On 07/02/2013 22:24, amro selem wrote: >> >> >> >> >> >> Hallo my colleagues. >> i hope every one doing ok . i did screening since two weeks . i >> noticed today this crystals. i don`t know either it salt or protein crystal >> . my protein has zero tryptophan so i could distinguish by UV camera. >> the condition was conditions: >> 0.1M SPG buffer pH 8 and 25%PEG 1500. in addition to Nickle chlorid 1mM. >> >> >> best regards >> Amr >> >> >> >> >> >> >> >> > > > -- > [email protected] Douglas Instruments Ltd. > Douglas House, East Garston, Hungerford, Berkshire, RG17 7HD, UK > Directors: Peter Baldock, Patrick Shaw Stewart > > http://www.douglas.co.uk > Tel: 44 (0) 148-864-9090 US toll-free 1-877-225-2034 > Regd. England 2177994, VAT Reg. GB 480 7371 36 > -- Raji Edayathumangalam Instructor in Neurology, Harvard Medical School Research Associate, Brigham and Women's Hospital Visiting Research Scholar, Brandeis University
