Ed, > Protein crystals are fragile but not soft. > If your crystals are like gelatine it's unusual.
I hate to disagree with the disagreement, but there are many exceptions to this rule. I have seen many protein crystals that are quite malleable and bendable. One protein produced rod-shaped crystals (150x40x40 um) that I could bend by almost 60 degrees and it would slowly snap back. Mounting it old school was a real pain, and their diffraction was mediocre. However, the majority of the crystals I have worked with adhere to the general rule you describe. Where the crystal physical behavior is anomalous, it is often when PEG is used and/or there are multiple components that contribute to the crystal's integrity (as in the case of membrane protein crystals with detergent). In the former case, crystals that sit in PEG solutions too long tend to be cross-linked (most likely due to the aldehydes that can exist in some batches of PEG). One could argue that the crosslinking adds long-range elasticity and a resistance to fracturing. In the latter case, I have observed large beautiful crystals of membrane proteins that have the consistency and malleability of warm butter. Sometimes optimization improved their integrity, and other times a new crystal form is needed. Regards, Michael **************************************************************** R. Michael Garavito, Ph.D. Professor of Biochemistry & Molecular Biology 603 Wilson Rd., Rm. 513 Michigan State University East Lansing, MI 48824-1319 Office: (517) 355-9724 Lab: (517) 353-9125 FAX: (517) 353-9334 Email: rmgarav...@gmail.com **************************************************************** On Feb 8, 2013, at 9:23 AM, Ed Pozharski wrote: > On Fri, 2013-02-08 at 14:53 +0400, Evgeny Osipov wrote: >> Protein crystals behave rather as gelatine and not as solid > > I'd have to disagree on that. Protein crystals are fragile but not > soft. If your crystals are like gelatine it's unusual. It has been > demonstrated that elastic properties of protein crystals are similar to > "organic solids". > > Cheers, > > Ed. > > -- > "I'd jump in myself, if I weren't so good at whistling." > Julian, King of Lemurs
