: CCP4 bulletin board [CCP4BB@JISCMAIL.AC.UK] on behalf of Ganesh Natrajan
[ganesh.natra...@ibs.fr]
Sent: Monday, February 11, 2013 3:37 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] protein crystals or salt crystals
Dear Amro,
What you could try is this. Make a solution of 0.5 % (w/v
Amro
Here is an extract from our paper, describing a method that is almost
infallible, and not too hard to do if you're organized. It can never
give false positives and (in the 3 cases we looked at it) only gave
false negatives when there was heavy precipitate in the drop.
Best wishes, Patrick
Dear Amro,
What you could try is this. Make a solution of 0.5 % (w/v) commassie
brilliant blue in 10% (v/v) ethanol in water. Pipet 1 ul of this into
your drop and close the cover slip. If the crystals are protein, they
should turn blue after some time (typically 30 mins). Salt crystals will
Michael,
It seems to me we have no disagreement, as we both say that it is
*unusual* for protein crystals to be non-fragile. Furthermore, my
objection is to "gelatin" characterization. I may be, as is my custom,
wrong, but in terms of elasticity gels are purely entropic. Protein
crystals, even
Ed,
> Protein crystals are fragile but not soft.
> If your crystals are like gelatine it's unusual.
I hate to disagree with the disagreement, but there are many exceptions to this
rule. I have seen many protein crystals that are quite malleable and bendable.
One protein produced rod-shape
On Fri, 2013-02-08 at 09:57 -0500, Jacob Keller wrote:
> do you have a reference quickly on hand
http://www.ncbi.nlm.nih.gov/pubmed/8129868
and references therein
http://www.sciencedirect.com/science/article/pii/S0022024801010922
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1300955/
The last r
: [ccp4bb] protein crystals or salt crystals
I'd have to disagree on that. Protein crystals are fragile but not
soft. If your crystals are like gelatine it's unusual. It has been
demonstrated that elastic properties of protein crystals are similar to
"organic solids"
Intere
I'd have to disagree on that. Protein crystals are fragile but not
> soft. If your crystals are like gelatine it's unusual. It has been
> demonstrated that elastic properties of protein crystals are similar to
> "organic solids"
>
Interesting--do you have a reference quickly on hand for those
On Fri, 2013-02-08 at 14:53 +0400, Evgeny Osipov wrote:
> Protein crystals behave rather as gelatine and not as solid
I'd have to disagree on that. Protein crystals are fragile but not
soft. If your crystals are like gelatine it's unusual. It has been
demonstrated that elastic properties of pro
So, if you are bored and have nothing else to do (which is how we all
are at times; kidding), can you set up a control experiment with
everything in the crystal dip except protein (so buffer and whatever)?
I know protein plays a role in the process, but I have done this before
when I had suspe
On Fri, 2013-02-08 at 09:13 -0500, Edward A. Berry wrote:
> I like to take a 5-sec 180* oscillation which gives plenty of
> spots in a nice pattern for a salt crystal
Second that
It also confuses bystanders really well - what a strange diffraction
pattern - half salt (small unit cell) / half pr
Raji Edayathumangalam wrote:
(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.
But before
lization. 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
> Date:
> To: CCP4BB@JISCMAIL.AC
CMAIL.AC.UK
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 a
runs the
expected size of your protein
*From:*Patrick Shaw Stewart [mailto:patr...@douglas.co.uk]
*Sent:* Friday, February 08, 2013 11:47 AM
*To:* CCP4BB@JISCMAIL.AC.UK
*Subject:* Re: [ccp4bb] protein crystals or salt
Hi Patrick
Did you mean that to go to BB? To put pressure on us? :)
We've not done that analysis, no - good idea though. No standard
purification buffer, though most commonly it's HEPES pH 7.5ish, varying
amounts of NaCl and glycerol. Like most people, I assume.
There certainly are w
11:47 AM
To: CCP4BB@JISCMAIL.AC.UK
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 wher
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
bject: Re: [ccp4bb] protein crystals or salt crystals
If SPG buffer is what I think it is, that means you have a significant
concentration of inorganic phosphate, which forms salt crystals when
mixed with divalent metal ions.
-Nat
On Thu, Feb 7, 2013 at 2:24 PM, amro selem 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 toda
If SPG buffer is what I think it is, that means you have a significant
concentration of inorganic phosphate, which forms salt crystals when
mixed with divalent metal ions.
-Nat
On Thu, Feb 7, 2013 at 2:24 PM, amro selem wrote:
>
>
>
>
> Hallo my colleagues.
> i hope every one doing ok . i did s
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