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A novel fluorescent probe for Ca2+based on coumarin containing an aza-crown ether unit was synthesised. The probe recognised Ca2+, and formed a 1 : 1 complex with Ca2+ in acetonitrile. A novel fluorescent probe for Ca2+ based on coumarin containing an aza-crown ether unit was synthesised. The probe recognised Ca2+, and formed a 1 : 1 complex with Ca2+ in acetonitrile. [ABSTRACT FROM AUTHOR]

PDE4 (phosphodiesterase-4)-selective inhibitors have attracted much attention as potential therapeutics for the treatment of both depression and major inflammatory diseases, but their practical application has been compromised by side effects. A possible cause for the side effects is that current PDE4-selective inhibitors similarly inhibit isoforms from all four PDE4 subfamilies. The development of PDE4 subfamily-selective inhibitors has been hampered by a lack of structural information. In the present study, we rectify this by providing the crystal structures of the catalytic domains of PDE4A, PDE4B and PDE4D in complex with the PDE4 inhibitor NVP {4-[8-(3-nitrophenyl)-[1,7]naphthyridin-6-yl]benzoic acid} as well as the unliganded PDE4C structure. NVP binds in the same conformation to the deep cAMP substrate pocket and interacts with the same residues in each instance. However, detailed structural comparison reveals significant conformational differences. Although the active sites of PDE4B and PDE4D are mostly comparable, PDE4A shows significant displacements of the residues next to the invariant glutamine residue that is critical for substrate and inhibitor binding. PDE4C appears to be more distal from other PDE4 subfamilies, with certain key residues being disordered. Our analyses provide the first structural basis for the development of PDE4 subfamily-selective inhibitors. [ABSTRACT FROM AUTHOR]

A novel fluorescent probe for Mg2+ based on coumarin Schiff-base was synthesized and characterized. The sensor displayed high selectivity toward Mg in acetonitrile, and shows 1:1 complex formation with Mg2+ in acetonitrile. [ABSTRACT FROM AUTHOR]

Synchrotron radiation X-ray topography is a nondestructive characterization technique for imaging the defect microstructure of crystalline materials. In this research, monochromatic X-ray surface-reflection topographic images were obtained of gem-quality pezzottaite from Madagascar using synchrotron radiation. Compared to polychromatic ("white") X-ray topography, the monochromatic technique provides an image of a certain lattice plane instead of a "superimposed" image of a series of atomic planes of the same orientation. It provides a higher resolution image with specific information about the orientation and features of dislocations and strain patterns in the sample. Since surface reflection topography is extremely sensitive to surface microstructure, sample preparation (i.e., polishing) is essential. X-ray topographic reflection images for (0006), (00012), and (00018) lattice planes at different angular positions along the rocking curve (a curve of the diffraction intensity versus the angular distance from a reference plane) were collected for seven pezzottaite samples. The full width at half maximum (FWHM) and the shape of the diffraction rocking curves reflect the degree of deformation of the sample. The pezzottaite samples exhibited various degrees of crystal perfection. Some crystals showed a mosaic structure containing orientation contrast (a type of X-ray topographic contrast that arises from portions of a sample that are crystallographically misoriented and show variations in diffracted intensity), but with a relatively sharp single-peaked rocking curve, which indicates fairly good crystallinity. However, other samples showed low degrees of crystal perfection, having a fairly wide rocking curve (angles ranging from 300-500 seconds FWHM) with several sharp peaks (see figure). X-ray topographic images from the imperfect crystals showed large amounts of strain and dislocations with a mosaic structure. Microscopic tubes were observed in the topographs of all seven samples. They were predominantly seen at the boundaries between different domains and along dislocations. We believe that the dislocations are caused by stress and the heterogeneous chemical composition of the material--as revealed by backscattered electron imaging and chemical analysis by electron microprobe and high-resolution inductively coupled plasma-mass spectrometry for Be and Li. Local variations in the crystal structure may cause internal strain resulting in lattice dislocation. This would explain the formation of the "tabby" extinction effect and anomalous biaxial character seen in some pezzottaite samples between crossed polarizers. [ABSTRACT FROM AUTHOR]

Diamonds are not only important for jewelry, but also have a variety of industrial applications. The presence of defects can often produce desirable properties in diamond. For example, plastic deformation may cause diamonds to appear pink or red. In addition to spectroscopic methods and transmission electron microscopy, we have recently used synchrotron "white beam" X-ray diffraction topography to observe the microstructures and defects in diamonds. The use of synchrotron X-ray radiation has the advantages of high intensity, polarization, and collimation, along with a small beam size and an adjustable energy level. This nondestructive method provides an ideal and effective way to detect crystal structure defects. Compared to conventional X-ray topography; it requires much less exposure time and provides higher resolution. However, it involves complex equipment that is not easy to operate. We used the "white beam" of 4W1A X-ray synchrotron radiation in Beijing, China, to investigate crystal structure defects and obtain diffraction patterns of 34 faceted colored diamonds (six natural-color diamonds, three HPHT-grown synthetic colored diamonds, six HPHT-treated colorless and colored diamonds, ten irradiated colored diamonds, and nine fixed-orientation polished colorless or brown natural diamond films). We calculated and defined the index of each diffraction spot on the Laue pattern for each sample. The diffraction spots varied from even, oval, and stretched, to fragmented shapes that corresponded to an increase in the degree of deformation of the diamonds. Various crystal structure defects, such as dislocations, twins, and numerous inclusions, were also located in the samples. From this study, the extent of defect deformation could be classified as very weak, weak, moderate, and strong (see table in the G&G Data Depository at www.gia.edu/gemsandgemology). All of the brown diamonds had strong defect deformation. Diamonds with impurities such as nitrogen, boron, and hydrogen (as determined by spectroscopic methods) had weak-to-moderate degrees of defect deformation. Most of the irradiated natural diamonds showed weak-to-moderate degrees of defect deformation. Colorless and yellowish green diamonds that were HPHT treated from natural brown starting material showed moderate-to-strong degrees of defect deformation. HPHT-grown synthetic diamonds showed a moderate degree of defect deformation. [ABSTRACT FROM AUTHOR]