Structure of commelinin,a blue complex pigment from the blue flowers of Commelina communis

The X-ray crystal structure of natural commelinin is investigated. The results demonstrate that commelinin is a tetranuclear (4 Mg²⁺) metal complex, in which two Mg²⁺ ions chelate to six anthocyanin molecules, while the other two Mg²⁺ ions bind to six flavone molecules, stabilizing the commelinin complex, a new type of supramolecular complex.     

X-ray diffraction analysis of the layer structure in a ferroelectric liquid crystal with a chiral nematic–chiral smectic C phase transition

A half-V-shaped switching ferroelectric liquid crystal (FLC) is a promising candidate for fast response displays. In the half-V FLC display, a liquid crystal with a chiral nematic–chiral smectic C phase transition is used, and the smectic layer is formed by cooling from N* to SmC* with an applied d.c. field. We studied the layer structure by means of X-ray measurements for two axes (ω and χ). By using a point-focused X-ray tube and optimizing the slit width, we succeeded in the two-axis measurement with a commercial X-ray system. The ω–χ profile of the half-V FLC showed two broad peaks in an arc-shaped high-intensity area. Our interpretation of this result is that the major part of the layer consists of a tilted-bookshelf structure and that the minor part consists of a near-bookshelf structure. Since optical microscopy observations on the half-V FLC cells showed a stripe-shaped texture, we consider that the coexistence of the tilted-bookshelf and the near-bookshelf structures forms the stripe-shaped patterns. The radius of the arc-shaped high-intensity area was nearly equal to the molecular tilt angle. This result can explain why the half-V FLC showed a desirable black appearance in spite of the stripe-shaped texture.     

Beamline AR‐NW12A: high‐throughput beamline for macromolecular crystallography at the Photon Factory

AR‐NW12A is an in‐vacuum undulator beamline optimized for high‐throughput macromolecular crystallography experiments as one of the five macromolecular crystallography (MX) beamlines at the Photon Factory. This report provides details of the beamline design, covering its optical specifications, hardware set‐up, control software, and the latest developments for MX experiments. The experimental environment presents state‐of‐the‐art instrumentation for high‐throughput projects with a high‐precision goniometer with an adaptable goniometer head, and a UV‐light sample visualization system. Combined with an efficient automounting robot modified from the SSRL SAM system, a remote control system enables fully automated and remote‐access X‐ray diffraction experiments.     

X-ray diffraction analysis of the layer structure in a ferroelectric liquid crystal with a chiral nematic-chiral smectic C phase transition

A half-V-shaped switching ferroelectric liquid crystal (FLC) is a promising candidate for fast response displays. In the half-V FLC display, a liquid crystal with a chiral nematic-chiral smectic C phase transition is used, and the smectic layer is formed by cooling from N* to SmC* with an applied d.c. field. We studied the layer structure by means of X-ray measurements for two axes (ω and χ). By using a point-focused X-ray tube and optimizing the slit width, we succeeded in the two-axis measurement with a commercial X-ray system. The ω-χ profile of the half-V FLC showed two broad peaks in an arc-shaped high-intensity area. Our interpretation of this result is that the major part of the layer consists of a tilted-bookshelf structure and that the minor part consists of a near-bookshelf structure. Since optical microscopy observations on the half-V FLC cells showed a stripe-shaped texture, we consider that the coexistence of the tilted-bookshelf and the near-bookshelf structures forms the stripe-shaped patterns. The radius of the arc-shaped high-intensity area was nearly equal to the molecular tilt angle. This result can explain why the half-V FLC showed a desirable black appearance in spite of the stripe-shaped texture.     

Gas chromatography applied to cultural heritage. Analysis of dark patinas on granite surfaces

The formation of dark patinas has been mainly related with deposition of gases and particles, and sulphation mechanisms particularly in calcareous rocks. However, in granitic monuments located in Galicia (northwest of Spain), especially in rural areas, this origin is unlikely since granite is a very poor calcium-containing rock and the atmospheric pollution in this area is negligible. A biological origin seems to be most probable. In order to know the importance of biological and atmospheric factors in the formation of dark patinas on granitic monuments, a number of analyses using several techniques are needed. The characterization of fatty acids in patinas by gas chromatography has established clear differences among samples. Thus, all of the samples having a biological origin displayed a similar fatty acid pattern, with unsaturated fatty acids predominating, especially oleic and linoleic acids; these were followed in abundance by the branched fatty acid 18:00 anteiso, and palmitic acid. Different patterns of fatty acid allowed establishment of an anthropogenic origin of the some of the patinas analysed.     

Microscopic measurement of circular dichroism spectra

A microscope device to measure the circular dichroism (CD) spectra of a specified microscopic region of chiral samples was constructed by combining of a couple of objective lenses and a CCD camera, which was installed in a sample chamber of a commercially available CD spectropolarimeter. By using this apparatus, high quality micro-CD spectra in the 60 x 60 microm region of samples could be measured. Micro-CD spectra of thin film of chiral DNA samples on glass and a natural kidney bean leaf were measured, and the potential of the micro-CD apparatus was successfully demonstrated.     

Synthesis and Crystal Structure of Dimethyl-7-oxabicyclo[2.2.1]hept-5-ene exo,exo-2,3-dicarboxylate

Dimethyl-7-oxabicyclo[2.2.1]hept-5-ene exo,exo-2,3-dicarboxylate (1) was prepared by Fisher esterification of 7-oxabicyclo[2.2.1]-hept-5-ene exo-2,3-dicarboxylic anhydride (2) in methanol. The colorless plates obtained were characterized by FT-IR, ¹H- and ¹³C-NMR, TGA-DSC, and single crystal X-ray diffraction. The material crystallizes in space group P2₁/c, with a = 9.2375(14) Å, b = 12.8757(18) Å, c = 9.4608(15) Å, β = 115.327(3)°, V = 1017.1(3) Å³, and Z = 4. Chains of hydrogen-bonded molecules along the c-axis interact in the b direction to form layers parallel to the bc plane.     

UV LED lighting for automated crystal centring

A direct outcome of the exponential growth of macromolecular crystallography is the continuously increasing demand for synchrotron beam time, both from academic and industrial users. As more and more projects entail screening a profusion of sample crystals, fully automated procedures at every level of the experiments are being implemented at all synchrotron facilities. One of the major obstacles to achieving such automation lies in the sample recognition and centring in the X-ray beam. The capacity of UV light to specifically react with aromatic residues present in proteins or with DNA base pairs is at the basis of UV-assisted crystal centring. Although very efficient, a well known side effect of illuminating biological samples with strong UV sources is the damage induced on the irradiated samples. In the present study the effectiveness of a softer UV light for crystal centring by taking advantage of low-power light-emitting diode (LED) sources has been investigated. The use of UV LEDs represents a low-cost solution for crystal centring with high specificity.