Hi Christine As Nagarajan mentioned, we do have a "UV Pen" that we offer at a reasonably modest price.
However we have not been promoting it because we've been struggling to find a camera that we can recommend to use with it. We use it with an old Russian microscope (normal glass optics) and a cheap consumer Panasonic camera on a "starlight" setting, which works very well. We developed it for our own crystallization project and we have found it very useful, although we occasionally get both false positives and false negatives. One problem is that the cheap camera we use is now obsolete, and we are investigating our own solution, which will involve writing our own software for an off-the-shelf CCD and lens. (CCD seems better than CMOS.) If anyone knows of a suitable more expensive SLR-type consumer camera, please let me know. We can't find one. We are looking at just the tail end of the fluorescence, the part that is in the visible or near-UV spectrum, so you need a sensitive camera. We have found that you need to push everything, taking e.g. 30 exposures and combining them, subtracting the "dark" image etc. Presumably the Panasonic point-and-click camera does this. One solution is to buy a camera from one of the microscope suppliers, but they use very old technology, and charge you a fortune for e.g. the controller (which is essentially a laptop that was designed 15 years ago). The results are no better than the Panasonic camera, and we hesitate to sell you a UV source for around 1000 pounds then recommend a camera system for 6,000. However the pens are available to anyone who wants to order one! We're not claiming that our approach is as good as the more expensive commercial systems, some of which have quartz optics. Each image takes 30s, you have to work in a dark room, and you can't use it in transmission mode (allowing you to see absorbance) for which you need quartz optics. Another way to go is to use the approach that we published recently, where you covalently (therefore unambiguously) label your crystals *after *they have grown. It's pretty much 100% accurate. See the methods section of the ref below. Hope this helps Best wishes Patrick Patrick D. Shaw Stewart, Stefan A. Kolek, Richard A. Briggs, Naomi E. Chayen and Peter F.M. Baldock. “Random Microseeding: A Theoretical and Practical Exploration of Seed Stability and Seeding Techniques for Successful Protein Crystallization” *Crystal Growth and Design*, 2011, 11 (8), p3432. On-line at http://pubs.acs.org/doi/abs/10.1021/cg2001442 On Fri, Sep 16, 2011 at 6:13 PM, Shiva Bhowmik <gene1...@gmail.com> wrote: > Would be curious to know the current limitations on UV microscopy employed > for screening protein crystals - such as content of aromatic amino acids, > protein size etc. > > Cheers, > > Shiva > > > On Fri, Sep 16, 2011 at 1:19 AM, Klaus Fütterer <k.futte...@bham.ac.uk>wrote: > >> From the experience when our (commercial) UV imaging system was set up, I >> can confirm that signal-to-noise is a non-trivial parameter for imaging in >> the UV range. >> >> I find the additional info gained from the UV capability very useful, not >> just to distinguish salt from protein crystals, but also to tell protein >> from buffer precipitate, buffer phase separation from protein phase >> separation, etc. >> >> Klaus >> >> >> ======================================================================= >> >> Klaus Fütterer, Ph.D. >> Reader in Structural Biology >> Undergraduate Admissions >> >> School of Biosciences P: +44-(0)-121-414 5895 >> University of Birmingham F: +44-(0)-121-414 5925 >> Edgbaston E: k.futte...@bham.ac.uk >> Birmingham, B15 2TT, UK W: http://tinyurl.com/futterer-lab >> ======================================================================= >> >> >> >> >> >> On 16 Sep 2011, at 04:57, Nagarajan V wrote: >> >> > Typically, what you image is Trp fluorescence by exciting at around 280 >> nm and observing at around 350 nm. Standard silicon based detectors do fine >> at the detection wavelength, although, as you can imagine, increased >> sensitivity in the UV means increase in the price of the detector. If your >> excitation and emission light paths do not overlap, you also can get by with >> standard glass (crown, flint, etc.) optics since they do allow some of the >> 350-nm light to get through. Therefore, yes, it is possible to build an >> inexpensive UV imager based on inexpensive excitation light source (Douglas >> Instruments offers a pen light), and standard lab microscope. Of course, for >> increased sensitivity and contrast you need a very good light source, optics >> made of quartz and calcium fluoride that let almost all the UV light >> through, highly discriminating filters and a sensitive detector. >> > >> > V. Nagarajan >> > JANSi >> > http://janscientific.com >> > >> > On Thu, Sep 15, 2011 at 7:07 PM, Edward A. Berry <ber...@upstate.edu> >> wrote: >> > A "real" UV microscope requires quartz optics, right? >> > Probably conventional microscopes use glass. >> > And you can't see 280 nm (and its not good for your eyes) >> > so you need some kind of phosphor screen to view the image? >> > >> > >> > Bosch, Juergen wrote: >> > I'm replying here to myself :-) >> > >> > So in an off-board discussion it turns out that the "microscope" in >> question was a special >> > emitted light and not a UV microscope. So real UV microscopes might be >> better for the >> > purpose of detecting real crystals. >> > >> > Sorry for the confusion - had too much sun today :-) >> > >> > Jürgen >> > >> > On Sep 15, 2011, at 4:19 PM, Jürgen Bosch wrote: >> > >> > I once tested such a commercial system in Seattle about 4 years ago. It >> did not impress >> > me. In particular the discrimination between salt and protein did not >> work for about 10 >> > different proteins from which we already had collected data. sure those >> were small >> > between 10 and 100 micrometer. Excuse was to few tryptophans >> > So in theory it is nice but a cheaper variant might be to add Gfp to >> your protein and >> > screen for something green. >> > Jürgen >> > >> > ...................... >> > 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/ >> > >> > On Sep 15, 2011, at 16:03, Frank von Delft <frank.vonde...@sgc.ox.ac.uk> >> wrote: >> > >> > A while ago I was trying to be cheap, so we played around with it quite >> > a bit in the lab. After rediscovering some of the basics of >> > signal-to-noise and microscope transmission efficiency and that sort of >> > rot, I realised that the commercial systems may not be all that >> > ridiculously overpriced after all. Not if one wants to be able to say >> > something useful about really really small crystals -- the only ones >> > that really matter in the grand scheme of things (big ones are quick to >> > test; little ones must first be optimized = money+time). >> > >> > But maybe I was just being incompetent. Happens. >> > phx. >> > >> > >> > >> > >> > On 15/09/2011 20:50, Andrew Purkiss-Trew wrote: >> > Quoting "Harman, Christine"<christine.har...@fda.hhs.gov>: >> > >> > Hi All, >> > I was curious if any of you have tried or even know if it is >> > possible to adapt a stereoscope (in my case an Olympus SZX10 model) >> > so as to view protein crystals with UV illumination. Basically, I >> > want a cheap manual version of what a Rock UV Imager does. I know >> > this is probably a crazy dream. However, I would greatly appreciate >> > any comments, advice or experience any of you may have. >> > >> > Molecular Dimension do such an adaptor which fits to existing >> microscopes. >> > >> > See >> > < >> http://www.moleculardimensions.com/shopdisplayproducts.asp?id=121&cat=X%2DtaLight%3Csup%3E%99%3C%2Fsup%3E+100+%2D+UV+for+Microscope+ >> > >> > >> > >> > ---------------------------------------------------------------- >> > This message was sent using IMP, the Internet Messaging Program. >> > >> > ...................... >> > Jürgen Bosch >> > Johns Hopkins University >> > Bloomberg School of Public Health >> > Department of Biochemistry & Molecular Biology >> > Johns Hopkins Malaria Research Institute >> > 615 North Wolfe Street, W8708 >> > Baltimore, MD 21205 >> > Office: +1-410-614-4742 >> > Lab: +1-410-614-4894 >> > Fax: +1-410-955-2926 >> > http://web.mac.com/bosch_lab/ >> > >> > >> > >> > >> > >> > >> > > -- patr...@douglas.co.uk Douglas Instruments Ltd. Douglas House, East Garston, Hungerford, Berkshire, RG17 7HD, UK Directors: Peter Baldock, Patrick Shaw Stewart http://www.douglas.co.uk Tel: 44 (0) 148-864-9090 US toll-free 1-877-225-2034 Regd. England 2177994, VAT Reg. GB 480 7371 36
