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Rocky protein crystals grown in silica gel

Jose Antonio Gavira Alexander E. Van Driessche 1Juan Manuel Garcia-Ruiz 

1. Instituto Andaluz de Ciencias de la Tierra, CSIC-UGR (LEC-IACT), Avda. Las Palmeras, nº 4, Granada 18100, Spain


Protein crystals are generally considered as soft material. The low reticular energy and the high solvent content make them very fragile and sensitive to any physical stress such as mechanical shocks, osmotic pressure, drying, etc.  Fragility and stability are two of the main features of protein crystals that make difficult their manipulation and limit the feasibility of using them for technological purposes [1-3].  We have shown that macromolecular crystals grown in gelled media (such as agarose, sephadex, polyacrylamide or silica), incorporate large volumes of the solid gel network into the body of the crystals.  In this communication we extend our results with lysozyme crystals grown in silica gels [4] to other proteins (thaumatin, insulin, ferritin, etc) proving that the phenomenon is universal.

Crystals were obtained by counter-diffusion or batch method in silica gels at silica concentrations ranging from 2 to 22% (v/v) . The protein crystals incorporate the solid silica fibers during their growth making the crystal appear optically translucent while maintaining crystal order at short and long-range scale. Silica incorporation was measured by termogravimetry, and the internal texture of the crystals showing the location of the silica fibers was studied by scanning electron microscopy. The mechanical properties and the stability of the crystals are improved by the incorporation of the highly hydrophilic silica phase. Increasing the silica gel concentration reduces the surface energy anisotropy to such an extend that spherical single crystals can be obtained as growth forms. The reinforced protein crystal enhances the mechanical stability and the drying behavior, as shown by scanning differential calorimetry. The crystals can be handled at room condition out of their mother solution using tweezers.  X-ray diffraction data can be collected outside capillaries without mounting to preserve the moisture. The application of these rocky crystals in Materials Science and Chemical Engineering is also discussed.

[1]   Y. Shen et al. (1993), Nature 366, 48.

[2]   K. Douglas et al. (1992), Science 257, 642.

[3]   T. Thomson. (1996), BYTE April 79.

[4]   J.M. García-Ruiz et al. (1998), Materials Research Bulletin, Vol 33, 11, 1593


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Related papers

Presentation: Poster at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, General Session 3, by Alexander E. Van Driessche
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-04-15 11:13
Revised:   2013-04-15 11:13