[3DEM] Oxford-style cryo holder

[Bob Grassucci]

Hi Esther,
    We have a couple CT3500 holders and are happy with them once we got 
good ones. 

    * They do occlude at a lower tilt angle than the Gatan holders.  55
      vs 65 degrees
    * The grid boat is held in place by 4 small silica balls which
      thermally isolates the boat from the rest of the holder which
      warms up after you put the holder in the scope.  This means:
          o When it warms up it releases any contaminant that stuck to
            it when it was transfered but that contamination clears
            after abut 30 or less.
          o The boat is prone to dislodging if some one with a heavy
            hand screws in the ring.  This requires either you send it
            back to Gatan for repair or you find the little balls and
            the grub screws that press them in place.
    * Screw ring issues:
          o We went through a bunch of screw rings until we found some
            that held our grids in firmly.  Some bottomed out too soon
            before contacting the grid.
          o Take care with the groove in the ring so as not to damage it
            thus rendering it useless.
    * We place a stopper under the end of the transfer station is that
      the tip is down hill from the dewar.  This ensures that the o-ring
      does not get frozen.
    * The holder takes longer to cool than the Gatan holder since it is
      cooled using the drip tube rather than being immersed in liquid.
    * We have a few grid boxes that do not fit in the grid box holder
      and have not experienced freeze drying yet.  If you have the same
      unit as ours it can be removed and machined to enlarge it.  Wait
      for the nitrogen boiling to subside and the transfer area is
      cooled below the devitrification temperature.
    * Out unit has a shutter on the transfer station (white and
      perpendicular to the tube).  Closing it after transferring the 
      holder will prevent cold from entering it.

I hope this helps but if you have any more questions give me a call.
    Regards,
    Bob

Esther Bullitt wrote:
> **** Messages to this list are automatically archived ***
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>
> Hi,
>
> We have an Oxford-style cryo holder (CT3500) on loan from Gatan, and
> wonder about people's experience with it.
>
> In particular, is it really not a problem that your grid box sits only
> N2 gas, not liquid?  What if your grid box does not fit in their grid box
> holder (ours do not) and therefore has to sit on the metal mesh, does that
> make it worse?
>
> Are there any special tricks for doing a cold transfer, that is, taking
> out a cryo grid and putting another in right away, without warming up the
> holder in between?
>
> And, of course, any other advice you might have.
>
> Thanks very much.
> Sincerely,
> Esther
>
> ---
> Esther Bullitt, Ph.D.
> Dept. of Physiology & Biophysics, Room W302
> Boston University School of Medicine
> 715 Albany Street (mail only;  couriers 
> 		  use 700 Albany Street)
> Boston, MA  02118-2526
>
> Email:      bullitt at bu.edu
> Telephone:  617-638-5037           
> Facsimile:  617-638-4041
>
>
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-- 
********************************

-Robert Grassucci-

Howard Hughes Medical Institute

Wadsworth Center

Empire State Plaza

Albany, NY 12201-0509

bobg at wadsworth.org

Phone: (518)474-5821

Fax:	(518)486-2191




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