Four new colchicinoids, gloriosamines A-D, from Gloriosa rothschildiana

Four new colchicinoids, gloriosamines A-D, were isolated from the aerial parts of Gloriosa rothschildiana. The structure of gloriosamine A, including the absolute configuration, was determined by chemical conversion from colchicine.     

Applications of Terahertz Spectroscopy in Biosystems

Terahertz (THz) spectroscopic investigations of condensed‐phase biological samples are reviewed ranging from the simple crystalline forms of amino acids, carbohydrates and polypeptides to the more complex aqueous forms of small proteins, DNA and RNA. Vibrationally resolved studies of crystalline samples have revealed the exquisite sensitivity of THz modes to crystalline order, temperature, conformational form, peptide sequence and local solvate environment and have given unprecedented measures of the binding force constants and anharmonic character of the force fields, properties necessary to improve predictability but not readily obtainable using any other method. These studies have provided benchmark vibrational data on extended periodic structures for direct comparisons with classical (CHARMm) and quantum chemical (density functional theory) theories. For the larger amorphous and/or aqueous phase samples, the THz modes form a continuum‐like absorption that arises because of the full accessibility to conformational space and/or the rapid time scale for inter‐conversion in these environments. Despite severe absorption by liquid water, detailed investigations have uncovered the photo‐ and hydration‐induced conformational flexibility of proteins, the solvent shell depth of the water/biomolecule boundary layers and the solvent reorientation dynamics occurring in these interfacial layers that occur on sub‐picosecond time scales. As such, THz spectroscopy has enhanced and extended the accessibility to intermolecular forces, length‐ and timescales important in biological structure and activity.     

1,4,6,9‐Tetraoxa‐5λ4‐selena‐spiro[4.4]nonane – A Combined Theoretical and Experimental Study

The symmetric spiro‐selenurane derived from ethylene glycol, 1,4,6,9‐tetraoxa‐5λ⁴‐selena‐spiro[4.4]nonane, was prepared from selenium tetrachloride and ethylene glycol and its molecular structure was determined by single crystal X‐ray diffraction. NBO analyses for the title compound and a related compound were conducted to assess the role of the stereochemical active lone pair on the selenium atom on the structure.     

X‐Ray Diffraction as a Local Probe Tool

For the structural characterization of nanoscale objects, X‐ray diffraction is widely used as a technique complementing local probe analysis methods such as scanning electron microscopy and transmission electron microscopy. Details on strain distributions, chemical composition, or size and shape of nanostructures are addressed. X‐ray diffraction traditionally obtains very good statistically averaged properties over large ensembles—provided this averaging is meaningful for ensembles with sufficiently small dispersion of properties. In many cases, however, it is desirable to combine different analysis techniques on exactly the same nano‐object, for example, to gain a more detailed insight into the interdependence of properties. X‐ray beams focused to diameters in the sub‐micron range, which are available at third‐generation synchrotron sources, allow for such X‐ray diffraction studies of individual nano‐objects.     

A New Main Group Metal Coordination Polymer: Synthesis,Structure, and Dielectric Constant Property of [Na(C6H4N5)(H2O)2]n

The reaction of NaOH with 4‐(2H‐tetrazol‐5‐yl)pyridine affords the first tetrazole‐pyridine sodium coordination polymer with chain structure, [Na(C₆H₄N₅)(H₂O)₂]_n ( 1 ). The compound could be characterized by single‐crystal X‐ray diffraction analysis. The temperature dependence of dielectric permittivity remains unchanged almost within the measured temperature range of 80 K to 270 K at 1 <SC>MH</SC>z, and the frequency dependence of the permittivity showed rapidly drops from 31.5 to 4.3 within the measured frequency range of 200 to 1 MHz at room temperature.