I must agree that the less stressed part of a needle may be the end not contacting the loop or meniscus, but protrudes out the end/top. One can carefully manipulate the crystal so that it is not parallel with the pin either by having a bent loop or setting the crystal slightly diagonal to the loop. If it is held out long enough, then only that part is in the beam with no background from the loop or mother liquor. In fact, I have seen where the meniscus was the problem as it "curved" the crystal in question....the part overhanging the loop diffracting quite nicely. Additionally, small molecule people will regularly use a small dab of grease (I prefer Apiezon N) on a loop or fiber to adhere the crystal and remove it from the batch...then freeze it. The advantage is simplicity, and one can remove a crystal from virtually all mother liquor. The disadvantages are it a bare crystal free from all liquor (must be frozen ASAP before it dehydrates) and depending on your skill and luck sometimes one gets more than one crystal. Finally, if there is a worry about dehydration, a tip is to move the crystal from the crystallization drop to oil increasing time for manipulation. (Again, my preference is PFPE). Kris
PS For a thin layer of grease, try disolving the grease in a volatile solvent, dipping the loop or fiber in the solution, and let "dry". ________________________________ From: Jürgen Bosch <jubo...@jhsph.edu> To: CCP4BB@JISCMAIL.AC.UK Sent: Tuesday, October 6, 2009 9:04:51 AM Subject: Re: [ccp4bb] Mounting needle-shaped crystals Hi Jack, you could try the following strategy: a) use a larger loop than your needle, then before freezing carefully dip the loop onto the glass slide to reduce the amount of liquid b) if your crystal is larger than your largest loop cut it c) see attached figure. The way I mount those type of crystals is not to break through the surface but instead to retract the loop and lift the crystal out of the drop. The tip of the crystal comes out as last. Typically the part of the crystal in the loop has a higher mosaicity due to this treatment as you slightly need to bend the crystal when fishing it out of the drop. d) The Mitegen loops are very useful Good luck, Jürgen On Oct 5, 2009, at 6:52 PM, Tanner, John J. wrote: Dear CCP4, > >I'm looking for advice on mounting thin needles for low temperature data >collection. Our needles are fairly long (100-200 microns) but only 20 >microns or less thick. When I pick them up with Hampton loops (0.05-0.1 mm >size), the crystals tend to break as they are moved out of the drop and >through the liquid-air interface. > >I see that Mitegen sells MicroLoops E, which are advertised as working well >for mounting needles. Can anyone recommend them? Can anyone recommend >Mitegen MicroMeshes or another tool for mounting needles? > >Thanks, > >Jack Tanner > > >-- >John J. Tanner >Professor of Chemistry and Biochemistry >University of Missouri-Columbia >125 Chemistry Building >Columbia, MO 65211 >Phone: 573-884-1280 >Fax: 573-882-2754 >Email: tanne...@missouri.edu >http://www.chem.missouri.edu/TannerGroup/tanner.html > > - Jürgen Bosch Johns Hopkins Bloomberg School of Public Health Department of Biochemistry & Molecular Biology Johns Hopkins Malaria Research Institute 615 North Wolfe Street, W8708 Baltimore, MD 21205 Phone: +1-410-614-4742 Lab: +1-410-614-4894 Fax: +1-410-955-3655 http://web.mac.com/bosch_lab/
