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<div>Hi all,</div>
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At the risk of being repetitive, there are several possibilities for “teaching” specimens. Sigma (and others like Worthington) has catalase, which can be readily assembled into platelets as mentioned by David. Also, it is quite enlightening to add the catalase
in a rather diluted form on the grid to see what a single particle specimen with ~200kDa molecules looks like. Furthermore, Sigma also has GroEl and hemocyanin (no, I do not work for Sigma, but they are a convenient source). Another nice specimen that is easy
to prepare (but somewhat seasonal) is earth worm hemoglobin. You can just dig a couple of worms from any garden, homogenize them and put the solution on a PD-10 disposable column (it is very obvious when the hemoglobin peak is coming out).
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<div>Unfortunately, the Department of Agriculture has strengthened the restrictions on the traffic of live viruses, which has made sharing TMV a real headache in terms of all the paperwork that has to be filled, otherwise, that is also a really nice specimen.</div>
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<div>Cheers!</div>
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<div>Ruben.</div>
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<div>On Oct 15, 2014, at 12:26 PM, David Gene Morgan <<a href="mailto:dagmorga@indiana.edu">dagmorga@indiana.edu</a>> wrote:</div>
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Hi,<br>
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<span class="x_Apple-tab-span" style="white-space:pre"></span>Just to jump back in, I fully agree with Reinhard about the value of preparing the sample yourself.<br>
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<span class="x_Apple-tab-span" style="white-space:pre"></span>Another issue with grids of negatively stained catalase is that they don't age well. A freshly made grid with freshly prepared crystals will show multiple orders of diffraction from the stained
crystals either in electron diffraction mode or when looking at the Fourier transforms of images of the stained crystals. As time goes by (and especially if the grids are not stored under constant temperature and humidity), the number of diffraction orders
that are visible will decrease. In my experience, purchased grids with negatively stained catalase are never as good as ones I have made myself, and often only show one or maybe two diffraction orders when they arrive from the manufacturer.<br>
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<span class="x_Apple-tab-span" style="white-space:pre"></span>One other thing that preparing the crystals yourself allows is you can do things like glucose embedding, standard freezing for cryoTEM, etc. If you purchase a prepared grid, you only get the stained
crystals, and you can teach so much more if your students can prepare the same sample multiple ways.<br>
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On 10/15/2014 10:46 AM, Reinhard Rachel wrote:<br>
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<blockquote type="cite">15.10.2014 um 16:36:<br>
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This may not be clear from David's message, but you can buy already prepared<br>
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<blockquote type="cite">TEM grids of negatively stained catalase from at least two sources: Ted<br>
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Pella<br>
<blockquote type="cite">and Electron Microscopy Sciences.<br>
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this might be true - but this "eliminates" one important step - the sample<br>
preparation.<br>
Personally, I will always try to have this step included in teaching or<br>
demonstrating EM to the 'un-experienced' - it is so important; it is one of the<br>
key steps. - Even a 'not optimally' prepared biological sample is valuable for<br>
teaching, and for explaining the difficulties.<br>
kind regards,<br>
Reinhard<br>
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--<span class="x_Apple-converted-space"> </span><br>
David Gene Morgan<br>
Electron Microscopy Center<br>
047D Simon Hall<br>
IU Bloomington<br>
812 856 1457 (office)<br>
812 856 3221 (3200)<br>
<a href="http://bio.indiana.edu/~cryo">http://bio.indiana.edu/~cryo</a><br>
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