Exploring the complex map of insulin polymorphism: a novel crystalline form in the presence of m-cresol.

In this study, the first crystal structure of a novel crystal form of human insulin bound to meta-cresol in an acidic environment is reported. The combination of single-crystal and powder X-ray diffraction crystallography led to the detection of a previously unknown monoclinic phase (P21). The structure was identified from the powder patterns and was solved using single-crystal diffraction data at 2.2 Šresolution. The unit-cell parameters at pH 6.1 are a = 47.66, b = 70.36, c = 84.75 Å, ß = 105.21°. The structure consists of two insulin hexamers per asymmetric unit. The potential use of this insulin form in microcrystalline drugs is discussed.

Human insulin polymorphism upon ligand binding and pH variation: the case of 4-ethylresorcinol.

This study focuses on the effects of the organic ligand 4-ethylresorcinol on the crystal structure of human insulin using powder X-ray crystallography. For this purpose, systematic crystallization experiments have been conducted in the presence of the organic ligand and zinc ions within the pH range 4.50-8.20, while observing crystallization behaviour around the isoelectric point of insulin. High-throughput crystal screening was performed using a laboratory X-ray diffraction system. The most representative samples were selected for synchrotron X-ray diffraction measurements, which took place at the European Synchrotron Radiation Facility (ESRF) and the Swiss Light Source (SLS). Four different crystalline polymorphs have been identified. Among these, two new phases with monoclinic symmetry have been found, which are targets for the future development of microcrystalline insulin drugs.

Novel crystalline phase and first-order phase transitions of human insulin complexed with two distinct phenol derivatives.

The primary focus of the present work is the study of the effects that two ligands and the crystallization pH have on the crystalline forms of human insulin. For this purpose, human insulin (HI) was co-crystallized with two distinct phenolic derivatives: the organic ligands meta-cresol (m-cresol) and 4-nitrophenol. The formation of polycrystalline precipitates was then followed by means of structural characterization of the individual specimens in terms of unit-cell symmetry and parameters. In both cases, two different polymorphs were identified via X-ray powder diffraction measurements, the first of hexagonal symmetry (R3 space group) at higher pH values and the second of monoclinic symmetry (space group P21) with unit-cell parameters a = 87.4282 (5), b = 70.5020 (3), c = 48.3180 (4) Å, ß = 106.8958 (4)°, the latter of which to our knowledge has never been observed before.

Modulation of atomic positions in CaCuxMn(7-x)O12 (x < or = 0.1).

The modulation of atomic positions in CaCu(x)Mn(7-x)O12 (x = 0 and 0.1) was studied using synchrotron radiation powder diffraction below 250 and 220 K, respectively. The copper-rich member CaCu(x)Mn(7-x)O12 (x = 0.23) does not show any modulation of the atomic positions at temperatures as low as 10 K. Using low-temperature neutron powder diffraction the modulation of the magnetic moments of Mn ions in CaCu(x)Mn(7-x)O12 (x = 0, 0.1 and 0.23) has been investigated. Long-range modulated magnetic ordering in CaCu(x)Mn(7-x)O12 (x = 0, 0.1 and 0.23) is observed below 90.4, 89.2 and 78.1 K. (0,0,q(p)) and (0,0,q(m)) are the propagation vectors describing the modulations of the atomic positions and the magnetic moments. For CaCu(x)Mn(7-x)O12 (x = 0 and 0.1) the magnetic modulation and atomic modulation lengths are related by a factor of 2 satisfying the relation (1-q(p)) = 2(1-q(m)).

Powder crystallography on macromolecules.

Following the seminal work of Von Dreele, powder X-ray diffraction studies on proteins are being established as a valuable complementary technique to single-crystal measurements. A wide range of small proteins have been found to give synchrotron powder diffraction profiles where the peak widths are essentially limited only by the instrumental resolution. The rich information contained in these profiles, combined with developments in data analysis, has stimulated research and development to apply the powder technique to microcrystalline protein samples. In the present work, progress in using powder diffraction for macromolecular crystallography is reported.

Magnetic and electronic properties of Bi(0.75)Ca(0.25)MnO(3).

The magnetic, structural and electronic properties of Bi(0.75)Ca(0.25)MnO(3) have been investigated in comparison with those of Bi(0.75)Sr(0.25)MnO(3). Magnetometry, diffraction and muon spin relaxation (µSR) data confirm different structural, magnetic and electronic transitions in the two compounds. The anisotropic changes of cell parameters across the structural transition in Bi(0.75)Ca(0.25)MnO(3) (275 K) differ markedly from the lattice anomalies in Bi(0.75)Sr(0.25)MnO(3) (600 K) and also from those in Bi(0.50)Ca(0.50)MnO(3) (325 K). The ground state of Bi(0.75)Ca(0.25)MnO(3) is characterized by a high degree of spin disorder and frustrated interactions. There is no evidence of a ferromagnetic component in the ground state of Bi(0.75)Ca(0.25)MnO(3). However, the application of a magnetic field (even of a few gauss) produces a continuous progressive polarization of the Mn moments (≈2 µ(B)/Mn at 5 T, ZFC, 5 K). Differences between Ca and Sr perovskites with x = 1/4 are greater than for the x = 1/2 counterparts, and point to distinct ground states and charge/orbital configurations.

A chromium terephthalate-based solid with unusually large pore volumes and surface area.

We combined targeted chemistry and computational design to create a crystal structure for porous chromium terephthalate, MIL-101, with very large pore sizes and surface area. Its zeotype cubic structure has a giant cell volume (approximately 702,000 cubic angstroms), a hierarchy of extra-large pore sizes (approximately 30 to 34 angstroms), and a Langmuir surface area for N2 of approximately 5900 +/- 300 square meters per gram. Beside the usual properties of porous compounds, this solid has potential as a nanomold for monodisperse nanomaterials, as illustrated here by the incorporation of Keggin polyanions within the cages.