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.

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.

On 8 February 2013 07:18, Frank von Delft <[log in to unmask]> 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

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