Hi, I beg to differ. Evaporation rates change dramatically between a
drop lying on a flat surface open to air flow; a drop lying in a
depression; and a drop lying in a depression with some reservoir
solution next to it. We're talking seconds to minutes.
So especially when using robotics to set up lots of drops, you might
find increased precipitation (or nucleation?) events in hanging drops --
but also less repeatable experiments.
As for visualisation: a proper drop shape (e.g. as used in the SwissCi
MRC or 3-drop plates) can make a big difference; certainly those are
superior to average hanging drop, I argue. (Whatever "superior" means.)
phx
Bostjan Kobe wrote:
> There is really not much difference in terms of setup between hanging and
> sitting drop, especially if the drops are set up on tape. Visualization is
> also usually easier with hanging drops.
>
> Bostjan
>
>
> On 1/05/09 1:37 AM, "Poul Nissen" <[log in to unmask]> wrote:
>
>
>> We often find results to be very different between hanging and sitting
>> drops (equilibration kinetics for one may be the explanation). Then
>> there's the good thing of hanging drops that crystals rarely stick to
>> the surface of the support facilitating the mounting procedure, in
>> particular for fragile crystals.
>> All in all we much prefer hanging drops for our membrane proteins -
>> the bottle neck is not in the extra few minutes for set-up, but in the
>> months it takes to produce the protein.
>>
>> Poul
>> On 30/04/2009, at 16.45, Jacob Keller wrote:
>>
>>
>>> I have noticed that a significant majority of crystallizations are
>>> done in hanging- rather than sitting-drop configuration, and
>>> considering the significant extra labor involved in hanging drops,
>>> can only understand this preference as a historical bias. I
>>> understand that sometimes one technique works and not the other, but
>>> all things being equal, why is hanging drop still "hanging around?"
>>> Any insights appreciated...
>>>
>>> Jacob Keller
>>>
>>> *******************************************
>>> Jacob Pearson Keller
>>> Northwestern University
>>> Medical Scientist Training Program
>>> Dallos Laboratory
>>> F. Searle 1-240
>>> 2240 Campus Drive
>>> Evanston IL 60208
>>> lab: 847.491.2438
>>> cel: 773.608.9185
>>> email: [log in to unmask]
>>> *******************************************
>>>
>>>
>
> ---
> Bostjan Kobe
> ARC Federation Fellow
> Professor of Structural Biology
> School of Chemistry and Molecular Biosciences
> and Institute for Molecular Bioscience
> Cooper Road
> University of Queensland
> Brisbane, Queensland 4072
> Australia
> Phone: +61 7 3365 2132
> Fax: +61 7 3365 4699
> E-mail: [log in to unmask]
> URL: http://profiles.bacs.uq.edu.au/Bostjan.Kobe.html
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