Bile acids are relevant markers for clinical research. This study reports the production of antibodies for isolithocholic acid, the isomer of the extensively studied lithocholic acid. The IgG titer and affinity maturation were monitored during the immunizations of three mice and two rabbits. In both animal models, polyclonal antibodies with a high selectivity and affinity were produced. The development of a direct competitive ELISA with a test midpoint of 0.69 ± 0.05 µg/L and a measurement range from 0.09–15 µg/L is reported. Additionally, the crystal structure of isolithocholic acid is described for the first time.
The absolute configuration of the title compound, C18H24O5·H2O, was not been determined by anomalous-dispersion effects, but has been assigned by reference to an unchanging chiral centre in the synthetic procedure. Intramolecular O—H···O hydrogen bonds stabilize the molecular conformation. In the crystal, O—H···O hydrogen bonds link the main molecules and the water molecules, forming an infinite three-dimensional network.
A new proton-transfer organic salt, quinolinium hydrogensquarate (C13H9NO4), has been synthesized and fully characterized by single crystal x-ray diffraction. The salt crystallizes in the monoclinic space group P21/n with the parameters:
a = 3.8290(12) Å, b = 20.960(6) Å, c = 13.802(4) Å, β = 95.452(5)°, V = 1102.7(6) Å3, Z = 4 formula units. The structure consists of uncommon supramolecular neutral dimers which pile up parallel to [100] forming infinite sheets. These centrosymmetric dimers are held together by lateral hydrogen-bonds whereby two neighboring coplanar hydrogensquarate anions act as a bridge between two terminal quinolinium cations and C-H...O bridgings interlink next neighboring sheets. The bulk structure of this salt is consolidated by weak ππ interactions within the sheets which are neatly ordered side-by-side relative to one another.
Ergometrinine
(2010)
The absolute configuration of ergometrinine, C19H23N3O2 {systematic name: (6aR,9S)-N-[(S)-1-hydroxypropan-2-yl]-7-methyl-4,6,6a,7,8,9-hexahydroindolo[4,3-fg]quinoline-9-carboxamide}, was established based on epimerization reaction of ergometrine, which was followed by preparative HPLC. The non-aromatic ring (ring C of the ergoline skeleton) directly fused to the aromatic rings is nearly planar [maximum deviation = 0.271 (3) Å] and shows an envelope conformation, whereas ring D, involved in an intramolecular N-HN hydrogen bond, exibits a slightly distorted chair conformation. The structure displays undulating layers in the ac plane formed by O-H...O and N-H...O hydrogen bonds.
Deacetyl tenuazonic acid
(2009)
The title compounds Zn2[S2CN(n-C4H9)2]4 1 and Zn2[(S(SO)CN(n-C4H9)2)(S2CN(n-C4H9)2)]2 3 build mixed crystals in the ratio 0.42: 0.58. Each compound forms dimers, in which the monomer moieties are related via a two-fold axis, coinciding with that of the monoclinic space group C2/c. The lattice parameters are a = 23.581(9), b = 17.112(5), c = 16.372(9) Å, and β = 128.33(3)°.
High-pressure studies on molecular crystals - relations between structure and high-pressure behavior
(2008)
This paper summarizes attempts to understand structureproperty relationships for a large class of aromatic diphenyl-1,3,4-oxadiazole molecules. Starting from the investigation of the crystal structure several common packing motifs as well as characteristic differences are derived. Many different molecules show a rather planar conformation in the solid state. A stronger intermolecular twist is only observed for compounds with substituents occupying the ortho-positions of the phenyl rings. Most crystal structures are characterized by the formation of stacks leading to intense ππ acceptordonor interactions between oxadiazole and phenyl rings. High-pressure investigations result in a soft compression behavior typical for organic molecular crystals. The bulk behavior may be described by the Murnaghan equation of state with similar coefficients (bulk modulus and its pressure derivative) for nearly all investigated compounds but also for related substances. The compression shows a strong anisotropy resulting from the specific features and packing motifs of the crystal structure. This is clearly indicated by a corresponding strain analysis. Additionally to the crystal structure the Raman spectrum was also investigated under increasing pressure. The different pressure behavior of external and internal modes reflects the difference between intra- and intermolecular interactions.