The applicability of the heteroepitaxic nucleant method using molecular sieves (MS) to sparse matrix screening of protein crystallization was examined using xylanase as a test protein. The sparse matrix screening with MS provided three crystal forms I-III under 80% of conditions, which confirmed a much higher yield of crystal formation when compared to the conventional screening without MS. In the form I crystals, an MS-dependent improvement in X-ray diffraction quality was observed. Furthermore, form III of xylanase crystals was obtained only in the presence of MS 5A or 13X, demonstrating an MS-dependent packing-space expansion of protein crystals.

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