Re: [ccp4bb] salt or protein?

Protein crystallography Programs for crystallography X-ray detectors
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From: artem {- at -} XTALS {- dot -} ORG artem {- at -} XTALS {- dot -} ORG
Date: 2007-04-16

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From: "Herbert J {- dot -} Bernstein" yaya {- at -} BERNSTEIN-PLUS-SONS {- dot -} COM
Date: 2007-04-16

Subject: Re: salt or protein?
From: artem {- at -} XTALS {- dot -} ORG artem {- at -} XTALS {- dot -} ORG
Date: 2007-04-16

Multiple overlapping salt lattices can sometimes look like protein
diffraction, as long as you're looking in only two dimensions. However, if
you can find the dominant rings, you should be able to discriminate since
the c-spacing of salt would nearly always be pretty small. Consider powder
patterns, and you should see what I mean.

Generally speaking, if your crystals visually appear to be single, and
give huge salt peaks - then they're probably salt. Exceptions - large,
non-diffracting protein crystals that have small salt crystals stuck to
them.

Ultimately, you can use the 'stick a fork in it' method: stick a needle in
your rod-like crystals and push. If you hear a crack, and see sharp clean
edges on the break - it's salt. If you feel the crystal 'give' and see
bending or pitting - it's probably protein.

Good luck!

Artem

> Hi All!
>
> I have been trying to screen for my protein crystals, from the
> crystals grown in 0.5 M Ammonium Sulphate, 1.0M Lithium Sulphate
> Monohydrate in 0.1 M TriSodium Citrate Buffer dihydrate Buffer at pH 5.6.
> Two different kinds of crystals observed: rod shaped and thin platy
> ones. Whenever I am trying to collect data from the rod shaped ones I am
> getting dominantly salt patterns but also spots at 15 A resolution bin
> repeatedly, where some of the spots very much look like from protein!
> what can be the reason for this? if anyone has come across similar
> situation please help.
>
> with regards,
> Sreeram Mahesh
>
>
> Research Student
> Prof S Ramakumar's lab
> PHYSICS department
> IISc Bangalore-560 012.
> ph:080-2293 2718.
> mobile: 9241145183.
>
>
> --
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CCP4bb <-- 2007 <-- April 2007 <-- 16 April 2007

Previous message:
Subject: Re: Selenomethionine reduction v.s. disulfide bond
From: artem {- at -} XTALS {- dot -} ORG artem {- at -} XTALS {- dot -} ORG
Date: 2007-04-16

Next message:
Subject: imgCIF workshop (new series) at BSR 2007
From: "Herbert J {- dot -} Bernstein" yaya {- at -} BERNSTEIN-PLUS-SONS {- dot -} COM
Date: 2007-04-16