Abstract
Differential Scanning Fluorimetry (DSF) is a rapid, economical, and a straightforward technique for estimating the thermal stability of proteins. The principle involves the binding of a fluorescent dye to thermally exposed hydrophobic pockets of a protein. The dyes used in this technique are highly fluorescent in a non-polar environment and are quenched when exposed to aqueous solution. The change in fluorescence can be used to follow unfolding of proteins induced by temperature, pH, or chaotropic agents. The method is well characterized for monomeric proteins. Here, we extend the application to supramolecular protein and nucleo-protein complexes using virus particles as an example. SYPRO-orange™ dye is the dye of choice because it is matched for use with q-PCR instruments and the fluorescence response is stable across a wide range of pH and temperatures. Advantages of this technique over standard biophysical methods include the ability for high-throughput screening of biological and technical replicates and the high sensitivity.
Keywords: Biophysics, Virology, Fluorescence, Hydrophobic patches, Subunit interactions
Materials and Reagents
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Representative data
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Acknowledgments
The work was funded by the grant R01 AI081961-01A1 from National Institutes of Health (NIH). This protocol was adapted from Rayaprolu et al. (2012).
References
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Hi Kathrin,We determined concentrations using gel densitometry. You could also use UV 280 to determine the protein concentration but because our virus sample also had DNA, we preferred running the gel and doing the densitometry. You can increase your protein concentration using molecular a weight cut off filter though AAV samples tend to stick to the filters quite a bit. The samples were obtained from our collaborators. For more information on purification of the virus and checking integrity, please refer to http://jvi.asm.org/content/87/24/13150.fullI hope this helps.
Hi Vamseedhar,we produce our AAVs by calcium phosphate-based transfection of plasmid DNA into HEK cells. The viral titer we reach is bellow the titer you need to get a protein concentration that high even after concentration by a molecular cut off filter. So we can`t perform DSF. We really like to test this method. Maybe you know how many HEK cells were transfected.Thank you for your quick response.
Hi,Sorry for the delayed response. Please look at the original reference (I posted the link in the previous post). Also look at references 51-54 in that link. This method was developed by our collaborators in SF9 using a baculoviral expression system. Let me know if you need more information.