Which brings us back to the Hellma "TrayCell" solution where you can,
from the same spectrometer, have both the cuvette option and the
quickness of the NanoDrop/NanoVue system.
Anyone that can comment on the performance of the TrayCell from Hellma?
Cheers,
Martin
On Dec 5, 2008, at 9:06 AM, Gregor Witte wrote:
> Agree!
> I think for crystallographic use the nanodrop is perfectly okay to
> see if the protein is 5mg/ml or 30mg/ml. But in fact I also do not
> trust our instrument if it comes to more important issues like
> preparing solutions for titrations or assays. And due to the small
> pathlength I do not trust absorptions of small concentrated samples
> at all. I always prefer a “real” 2-beam spectrophotometer
> (monochromators) with a quarz-cuvette and a nice pathlength. Of
> course, you cannot reliably measure solutions exceeding Abs 1 or
> maybe 1.5 OD in a spectrophotometer with 1cm pathlength.
>
> There’s also one quite strange thing about the nanodrop – they sell
> the “calibration check solution” (which is some kind of yellow
> chromate-solution with known absorption), then you check your
> nanodrop with it and maybe find out that it’s off to some certain
> extend: But then you’re stuck(!), because you cannot calibrate it on
> your own. I guess it would be quite easy to integrate a calibration-
> option into the software, but at the moment the instrument tells you
> “calibration failure” and you have to call the service guys who then
> carry it home and calibrate it by turning of the two small screws at
> the top of it and then glue them with locktite.
> Anyway, at least for our mid to high concentrated samples the
> nanodrop is not showing large fluctuations so we are happy with it.
> But everyone using a nanodrop should check it from time to time – as
> I found out that ours was off more than 20% at one day - which
> raised some trouble of course…
>
> Cheers,
>
> Gregor
>
>
> Von: CCP4 bulletin board [mailto:[log in to unmask]] Im Auftrag
> von Filip Van Petegem
> Gesendet: Donnerstag, 4. Dezember 2008 22:20
> An: [log in to unmask]
> Betreff: Re: [ccp4bb] suggestions for UV spectrometer
>
> I want to add I absotely hate the nanodrop. We've had a demo for
> it, and found the readouts to be very unreliable. Fluctuations of
> 20% and more. Just leaving the same drop in and measuring the sample
> multiple times gives different values (going in both directions, so
> not only due to evaportations). Sure, it's easy and fast, and maybe
> good to have a rough idea about your protein concentration, but I
> would never want to use it for exact measurements such as needed for
> e.g. a CD or an ITC instrument. I've heard other labs in our
> department have similar issues. We've also had a demo for the
> Nanovue from GE Healthcare: same issues - very large fluctuations
> from one sample to another. I suppose this is simply an inherent
> problem with small volumes...
>
> Cheers
>
> Filip Van Petegm
>
>
> On Thu, Dec 4, 2008 at 12:48 PM, Patrick Loll <[log in to unmask]>
> wrote:
> At the risk of dragging this discussion even further afield from
> crystallography:
>
> How can you get realistic numbers for concentrated solutions using
> the Nanodrop? I understand that the instrument reduces absorbance
> by using a very short path length. However, I thought that in order
> for the Beer-Lambert formalism to be applicable, the solution needs
> to be sufficiently dilute so that the chance of molecules
> "shadowing" one another is negligible. Isn't this condition violated
> for concentrated solutions (even with short path lengths)?
>
> Pat
>
> On 4 Dec 2008, at 1:27 PM, Michael Giffin wrote:
>
>
> We also like the Nanodrop...
> ---------------------------------------------------------------------------------------
> Patrick J. Loll, Ph. D.
> Professor of Biochemistry & Molecular Biology
> Director, Biochemistry Graduate Program
> Drexel University College of Medicine
> Room 10-102 New College Building
> 245 N. 15th St., Mailstop 497
> Philadelphia, PA 19102-1192 USA
>
> (215) 762-7706
> [log in to unmask]
>
>
>
>
> --
> Filip Van Petegem, PhD
> Assistant Professor
> The University of British Columbia
> Dept. of Biochemistry and Molecular Biology
> 2350 Health Sciences Mall - Rm 2.356
> Vancouver, V6T 1Z3
>
> phone: +1 604 827 4267
> email: [log in to unmask]
> http://crg.ubc.ca/VanPetegem/
.
B. Martin Hallberg, PhD
Assistant professor
Department of Cell and Molecular Biology
Medical Nobel Institute
Karolinska Institutet
Von Eulersv. 1
SE-171 77 Stockholm
Sweden
Fax: +46-8-339380
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