Diffraction from protein powder is a relatively new development which requires the beam properties of synchrotrons. As you know, of course, the number of Debye-Scherrer rings are increasing dramatically with diffraction angle. Since proteins have such a large unit cell, the reflections are very closely spaced in angle and make the ring pattern extremely crowded. Only with advanced data reduction methods the overlap of the ring intensities can be deconvoluted up to a certain resolution. This is typically in the 3 A range for moderately sized proteins. So, I dont expect any review to be older than 10 years. >From the literature I know that the structures that come out of these investigations are identical or at least extremely similar to those from single crystals.
Greetings Marius > It would be interesting to know about such reviews if they exist. > > I would worry that in powder form the structure of the protein is not > the same as in solution, that is, proteins would denature upon > dehydration. So are there any powders for which the structure is > still intact? > > Conversely, in crystalline form, we know that the structure is (can > be) relevant. The best example I can think of that borders on your > question is the case of insulin. Insulin is stored and preserved in > crystalline form and the crystals are very small and the protein is > active (so the structure must be relevant). (The size of the crystals > matters for medical purposes, that's another story.) So when we think > of a powder as a collection of very small crystals - as is typically > the case in organic and inorganic chemistry, then your question is > very good indeed. But other than insulin, I cannot think of many > examples. Lysozyme is sold as a crystalline powder. So are some other > egg proteins, such as albumin, lactalbumin, etc. In a lot of other > cases a crystalline suspension is sold (for example xylose > isomerase), but I think it does not survive when dried. > > If experiments have been done and reviews have been written, I would > expect them to be old (>30-40 years). > > Mark > > > > > > -----Original Message----- > From: Marius Schmidt <[EMAIL PROTECTED]> > To: CCP4BB@JISCMAIL.AC.UK > Sent: Tue, 13 Nov 2007 12:59 pm > Subject: [ccp4bb] > > > > > > > > Somebody out there who could direct me to > a nice review of protein powder diffractometry > including the application of Rietveld refinement > to such data. > > Any hint appreciated > many thanks in advance > > Marius > > Dr.habil. Marius Schmidt > Asst. Professor > University of Wisconsin-Milwaukee > Department of Physics Room 454 > 1900 E. Kenwood Blvd. > Milwaukee, WI 53211 > > phone: +1-414-229-4338 > email: [EMAIL PROTECTED] > http://users.physik.tu-muenchen.de/marius/ > > > > > _____________________________________________________________________ > ___ > Check Out the new free AIM(R) Mail -- Unlimited storage and > industry-leading spam and email virus protection. Dr.habil. Marius Schmidt Asst. Professor University of Wisconsin-Milwaukee Department of Physics Room 454 1900 E. Kenwood Blvd. Milwaukee, WI 53211 phone: +1-414-229-4338 email: [EMAIL PROTECTED] http://users.physik.tu-muenchen.de/marius/
