X-ray diffraction from magnetically oriented microcrystal suspensions detected by a shutterless continuous rotation method

Abstract

In this study, the magnetically oriented microcrystal suspension (MOMS) method is combined with the shutterless continuous rotation method. In the MOMS method, the suspension has to be rotated to maintain the three‐dimensional orientation of microcrystals. This means that it is compatible with the continuous rotation method, which also utilizes sample rotation. The time constants of the two methods should match to allow their successful combination. The conditions required for the MOMS method for combination with the continuous rotation method are investigated. Experiments are performed with a complementary metal–oxide semiconductor (CMOS) detector and the restriction imposed on the time constant for the MOMS method by the continuous rotation method is examined. The combination of these two methods is a promising approach for realizing the structure analyses of biomolecules from their microcrystalline powders.

Determination of the Anisotropic Rotational Diffusion Constant of Microcrystals Dispersed in Liquid Medium

“…For prolate or oblate particles, D rot is evaluated by where V is the volume of the particle and η is the viscosity of the suspending medium. F is a factor that depends on the particle shape . For a sphere, F = 1, and eq reduces to a well-known formula of Stokes’ law: D rot = k B T /(8 πηr 3 ), with r being the radius of the sphere.…”

“…If l a is larger than l b , the shape is prolate; if l a is shorter than l b , the shape is oblate. It is reported 31 that for the prolate shape the rotational diffusion constant about the symmetry axis is larger than the others, while for the oblate shape it is smaller than the others. In the present case, D θ is larger than the other two, and we conclude that the shape is prolate.…”

“…F is a factor that depends on the particle shape. 31 For a sphere, F = 1, and eq 3 reduces to a well-known formula of Stokes' law: D rot = k B T/(8πηr 3 ), with r being the radius of the sphere.…”

X-ray Single-Crystal Structural Analysis of a Magnetically Oriented Monoclinic Microcrystal Suspension of α-Glycine

“…In this method, a microcrystal suspension is biaxially aligned using a magnetic field to obtain a "magnetically oriented microcrystal suspension" (MOMS) [5,6]. Then, the MOMS is subjected to in situ single-crystal X-ray analysis [7][8][9], or its suspending medium is consolidated to obtain a "magnetically oriented microcrystal array" (MOMA) to perform the single-crystal X-ray analysis ex situ [10,11]. The biaxial alignment was first reported by Stainer to align superconducting materials [12,13].…”

“…Those crystals belong to the orthorhombic [11,14] and monoclinic [10] systems. We also performed single-crystal structure determination of orthorhombic crystals using MOMS [7][8][9]. Magnetically aligned monoclinic microcrystals exhibit twin orientations [10], which makes the analysis of MOMA complicated (sucrose [10], cellobiose [15], and zinc citrate dihydrate [16]).…”