We have proteins that melt at >60˚C but they don't crystallize. According to your 45 degree rule we should have crystals, what are we doing wrong ?
Jürgen On Sep 28, 2011, at 10:05 AM, Artem Evdokimov wrote: For what it's worth, we've been using thermofluor to compare the 'apparent' melting points of enzymes with their thermal stability measured as inhibition of their respective reactions by elevated temperature. The data so far make sense - the differences in apparent enzyme Tm (using the same conditions as the reaction mix!) match the differences in the half-inhibition T. Not the absolute number,though (which is not unexpected givn the different kinds of measurements involved). So I'd say thermofluor is reasonably good at comparing different proteins. Qualitatively at least. Artem On Wed, Sep 28, 2011 at 6:25 AM, Patrick Shaw Stewart <patr...@douglas.co.uk<mailto:patr...@douglas.co.uk>> wrote: I actually think you can make comparisons between different proteins. We heard a very nice talk by Jose Marquez about exactly this at the RAMC meeting recently. Basically, 45C seemed to be the dividing line. If your protein melts below this it's a bad sign for crystallization and may point to setting up your crystallization experiments at lower temperatures. Patrick On Thu, Sep 23, 2010 at 6:04 PM, Anastassis Perrakis <a.perra...@nki.nl<mailto:a.perra...@nki.nl>> wrote: Hello - The excellent paper of McCrary, uses differential scanning calorimetry, which will give an absolute measure of thermostability. Using Thermofluor I would be afraid you can only assess the relative thermostability of one protein in different conditions. As your fluorescence reporter would interact differently with exposed hydro[hobic patches in different proteins, I would be a bit more careful in comparing the Thermofluor results between different proteins ... I am not aware of anyone correlating differential scanning calorimetrywith Thermofluor data, but I must admit I have not looked up that literature recently. A. On 23 Sep 2010, at 18:40, Philippe DUMAS wrote: > Le 23/09/2010 17:28, Raji Edayathumangalam a écrit : > > Raji > I suggest having a look to this paper: > McCrary et al. J. Mol. Biol. 264(1996) 784 > where you will find an interesting study on protein stability and an > interesting comparison with other proteins. > Philippe Dumas > >> Hi Folks, >> >> Sorry for the pre-xtallo question; pre-xtallo right now, but hoping >> to >> take my protein the xtallo way one of these days! >> >> I am currently performing Thermofluor assays with my protein and the >> results show that the Tm is ~45C. I am looking for some examples of >> proteins and their melting temperatures so that I can gauge where my >> protein falls in the spectrum of unstable-to-stably folded. For >> example, the melting temperature of some forms of lysozyme is 73.8C >> (very stable, I suppose). >> >> Just need a sense for whether my protein is considered unstable or >> somewhat stable. Please could you share some examples. >> >> Many thanks. >> Raji >> >> ----------- >> Raji Edayathumangalam >> Joint Research Fellow >> Harvard Medical School/ >> Brigham and Women's Hospital >> Brandeis University >> > > <McCrary-JMB264(1996)784.pdf><p_dumas.vcf> -- patr...@douglas.co.uk<mailto: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<http://www.douglas.co.uk/> Tel: 44 (0) 148-864-9090 US toll-free 1-877-225-2034<tel:1-877-225-2034> Regd. England 2177994, VAT Reg. GB 480 7371 36 ...................... 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/
