Atomically flat, fully strained Si 1−x Ge x layers with thicknesses ranging from 40 to 240 nm were grown on Si͑001͒ at 450°C by ultrahigh-vacuum chemical vapor deposition and subjected to annealing at 1000°C for 20 min to induce relaxation. In order to minimize surface diffusion during annealing and thereby inhibit strain-induced roughening in favor of misfit dislocation formation, SiO 2 capping layers are deposited prior to annealing. The overall process results in smooth, relaxed alloy layers without the necessity of using several-m-thick compositionally graded buffer layers.

-Xylosidases are involved in the breakdown of xylans into xylose and belong to either family 39 or 43 of the glycosyl hydrolases. At present, no structural information is available for any member of these families. -Xylosidase from the thermophilic anaerobe Thermoanaerobacterium saccharolyticum, a member of glycosyl hydrolase family 39, has been crystallized at 296 K using the hanging-drop vapour-diffusion method. The crystal diffracts to 2.4 A Ê resolution with synchrotron X-rays and belongs to space group 4 1 2 1 2 (or P4 3 2 1 2), with unit-cell parameters a = b = 92.75, c = 241.37 A Ê . The asymmetric unit contains two monomers of the recombinant enzyme, giving a corresponding V M of 2.21 A Ê 3 Da À1 and a solvent content of 44.3%.

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