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/ > > > > > > > > > > > > >
