Trends and Challenges in Experimental Macromolecular Crystallography

Macromolecular X-ray crystallography underpins the vigorous field of structural molecular biology having yielded many protein, nucleic acid and virus structures in fine detail. The understanding of the recognition by these macromolecules, as receptors, of their cognate ligands involves the detailed study of the structural chemistry of their molecular interactions. Also these structural details underpin the rational design of novel inhibitors in modern drug discovery in the pharmaceutical industry. Moreover, from such structures the functional details can be inferred, such as the biological chemistry of enzyme reactivity. There is then a vast number and range of types of biological macromolecules that potentially could be studied. The completion of the protein primary sequencing of the yeast genome, and the human genome sequencing project comprising some 105 proteins that is underway, raises expectations for equivalent three dimensional structural database

Structural evidence for the partially oxidized dipyrromethene and dipyrromethanone forms of the cofactor of porphobilinogen deaminase: structures of the Bacillus megaterium

The enzyme porphobilinogen deaminase (PBGD; hydroxymethylbilane synthase; EC 2.5.1.61) catalyses an early step of the tetrapyrrole-biosynthesis pathway in which four molecules of the monopyrrole porphobilinogen are condensed to form a linear tetrapyrrole. The enzyme possesses a dipyrromethane cofactor, which is covalently linked by a thioether bridge to an invariant cysteine residue (Cys241 in the Bacillus megaterium enzyme). The cofactor is extended during the reaction by the sequential addition of the four substrate molecules, which are released as a linear tetrapyrrole product. Expression in Escherichia coli of a His-tagged form of B. megaterium PBGD has permitted the X-ray analysis of the enzyme from this species at high resolution, showing that the cofactor becomes progressively oxidized to the dipyrromethene and dipyrromethanone forms. In previously solved PBGD structures, the oxidized cofactor is in the dipyromethenone form, in which both pyrrole rings are approximately coplanar. In contrast, the oxidized cofactor in the B. megaterium enzyme appears to be in the dipyrromethanone form, in which the C atom at the bridging α-position of the outer pyrrole ring is very clearly in a tetrahedral configuration. It is suggested that the pink colour of the freshly purified protein is owing to the presence of the dipyrromethene form of the cofactor which, in the structure reported here, adopts the same conformation as the fully reduced dipyrromethane form

Aussicht vom Stift St Gallen auf dem Buoch gegen Norden

Joh. Hädener ad. nat. delineavit ; J. C. Mayr sc. LindauNotiz mit Tinte auf dem Papier in der unteren rechten Ecke: 127[...?] Exemplar der Zentralbibliothek Zürich, Graphische Sammlung und Fotoarchi

Quantitative determination of CBD and THC and their acid precursors in confiscated cannabis samples by HPLC-DAD.

Analysis of cannabis has gained new importance worldwide, mainly for quality control within the legalized recreational and medical cannabis industry, but also for forensic differentiation between drug-type cannabis and legal products such as fiber hemp and CBD-rich/THC-poor cannabis. We herein present an HPLC-DAD method for quantitative analysis of major neutral and acidic cannabinoids in herbal cannabis and hashish: Δ-tetrahydrocannabinol (THC), Δ-tetrahydrocannabinolic acid A (THCA), cannabidiol (CBD), cannabidiolic acid (CBDA), and cannabinol (CBN). Plant material was dried, homogenized and extracted with a mixture of methanol/hexane. Chromatographic separation of the analytes was achieved on a core-shell C8 column using gradient elution with water/acetonitrile containing 0.1% formic acid. The analytical run time was 13 min and analytes were detected at 210 nm. The method is selective, sensitive, accurate, and precise, as confirmed through validation according to ICH and AOAC guidelines. Linearity in herbal cannabis ranged from 0.04 to 4.00% for the neutral cannabinoids, and from 0.40 to 20% for the acids. Linear ranges in hashish samples were 0.13-13.33% and 1.33-66.66%, respectively. The presented method was successfully applied to characterize 110 cannabis samples seized by the Swiss police, demonstrating its applicability for routine cannabis potency testing in the forensic setting