Predicting and tuning physicochemical properties in lead optimization: amine basicities

This review describes simple and useful concepts for predicting and tuning the pK(a) values of basic amine centers, a crucial step in the optimization of physical and ADME properties of many lead structures in drug-discovery research. The article starts with a case study of tricyclic thrombin inhibitors featuring a tertiary amine center with pK(a) values that can be tuned over a wide range, from the usual value of around 10 to below 2 by (remote) neighboring functionalities commonly encountered in medicinal chemistry. Next, the changes in pK(a) of acyclic and cyclic amines upon substitution by fluorine, oxygen, nitrogen, and sulfur functionalities, as well as carbonyl and carboxyl derivatives are systematically analyzed, leading to the derivation of simple rules for pK(a) prediction. Electronic and stereoelectronic effects in cyclic amines are discussed, and the emerging computational methods for pK(a) predictions are briefly surveyed. The rules for tuning amine basicities should not only be of interest in drug-discovery research, but also to the development of new crop-protection agents, new amine ligands for organometallic complexes, and in particular, to the growing field of amine-based organocatalysis.     

Differenzierung von Theobroma cacao und Theobroma grandiflorum mittels PCR

Zusammenfassung:  Die Gattung Theobroma umfasst etwa 20 Arten, von denen insbesondere die Art Theobroma cacao L. mit den beiden Hauptsorten (Variet?ten) „Criollo“ und „Forastero“ wirtschaftliche Bedeutung hat. Bislang erfolgte die Unterscheidung der Kakaosorten und -arten nur morphologisch und, dadurch bedingt, nur in einem sehr frühen Verarbeitungsstadium, d. h. eine Reinheitskontrolle ist zu einem sp?teren Zeitpunkt nicht mehr m?glich. Andererseits erfolgt die Herstellung von Kakaomasse heute zunehmend im Erzeugerland, Schokolade oder Kakaohalberzeugnisse werden vom verarbeitenden Unternehmen zugekauft. Eine genaue und reproduzierbare Spezifikationskontrolle ist aus den skizzierten Gründen bislang nicht m?glich. Im Gegensatz zur alten Kakaoverordnung liefert die neue Kakaoverordnung vom 15. Dezember 2003 keine Definition des Kakaos mehr. Die Kakao- und Schokoladenindustrie geht aber nach wie vor davon aus, dass nur die Kakaoart T. cacao bei der Herstellung von Schokolade zur Anwendung kommt (allgemeine Verkehrsauffassung in Anlehnung an die alte Kakaoverordnung). Die Kakaoart T. grandiflorum (Cupuassu) gewinnt auf dem südamerikanischen Markt immer mehr an Bedeutung. Beispielsweise werden die Bohnen vermehrt zu Schokolade-artigen Produkten (Cupu-lade) verarbeitet. Im Rahmen dieser Arbeit wurden eine PCR- und eine PCR-RFLP Methode entwickelt, die eine Detektion beider Theobroma-Arten in Kakao und Schokoladenprodukten erlauben.

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The genus Theobroma comprises about 20 species. The highest economic attention is paid to the cultivars (varieties) “Criollo” and “Forastero” of the species Theobroma cacao L., which are used for chocolate production. Up to now, the differentiation of cocoa species and cultivars is performed morphologically. Hince, a purity control in late processing steps of chocolate production is not possible. However, most of the cocoa mass production takes place in the countries of cocoa origin and is then bought as semi-finished products by the chocolate industry. Species identification is not possible at this stage due to the manufacturing process. In the former “Kakaoverordnung” a definition of the cocoa species (T. cacao) used for chocolate production was given. The current “Kakaoverordnung” (passed in December 2003) lacks such a definition. Nevertheless, it is general acceptance in the chocolate industry to exclusively use the species T. cacao for chocolate production. On the other hand, the species T. grandiflorum (Cupuassu) is getting more and more important on the South American market where beans are used for the creation of chocolate-like products e.g. Cupu-late. This work describes the development of a PCR and a PCR-RFLP method for the detection of cocoa species in chocolate products.

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Eingegangen: 20. Juli 2007; angenommen: 8. August 2007     

Legs evolved only at the end!

Talking about legged locomotion often evokes the idea that animals using such devices are perfectly adapted to this kind of motion and should be copied by robotics. The aim of this contribution is to show that the evolution of legs comes late in phylogeny, be it in arthropods or vertebrates. Neural control of legs in vertebrates has to deal with conservative arrangements 'invented' for axial locomotion of metameric organisms. The structure of this paper is to show the importance of axial driven propulsion in vertebrates without legs, with legs and only at the end how limbs move the body in eutherian mammals.     

Orientations of overdamped magnetic nanorod-gyroscopes

Overdamped magnetic nanorod-gyroscopes driven by a rotating magnetic field undergo a series of reorientations when sedimenting on top of a surface in a viscous liquid. By changing the amplitude and the rotation frequency of the driving magnetic field, the nanorod-gyroscope either synchronizes or desynchronizes with the field and rotates either around its long or short axis. The different regimes of motion are explained theoretically by coupling the nanorod-gyroscopes motion to the creeping flow equations of the surrounding fluid. It is shown that friction anisotropy plays an important role for the orientation of the nanorod-gyroscopes.     

Neuroadaptations in ionotropic and metabotropic glutamate receptor mRNA produced by cocaine treatment

The expression of glutamate receptor/subunit mRNAs was examined 3 weeks after discontinuing 1 week of daily injections of saline or cocaine. The level of mRNA for GluR1-4, NMDAR1, and mGluR5 receptors was measured with in situ hybridization and RT-PCR. In nucleus accumbens, acute cocaine treatment significantly reduced the mRNA level for GluR3, GluR4, and NMDAR1 subunits, whereas repeated cocaine reduced the level for GluR3 mRNA. Acute cocaine treatment also reduced the NMDAR1 mRNA level in dorsolateral striatum and ventral tegmental area. In prefrontal cortex, repeated cocaine treatment significantly increased the level of GluR2 mRNA. The GluR2 mRNA level was not changed by acute or repeated cocaine in any other brain regions examined. Repeated cocaine treatment also significantly increased mGluR5 mRNA levels in nucleus accumbens shell and dorsolateral striatum. Functional properties of the ionotropic glutamate receptors are determined by subunit composition. In addition, metabotropic glutamate receptors can modulate synaptic transmission and the response to stimulation of ionotropic receptors. Thus, the observed changes in levels of AMPA and NMDA receptor subunits and the mGluR5 metabotropic receptor may alter excitatory neurotransmission in the mesocorticolimbic dopamine system, which could play a significant role in the enduring biochemical and behavioral effects of cocaine.     

Molecular typing of Neisseria gonorrhoeae causing repeated infections: evolution of porin during passage within a community

Thirty-three Neisseria gonorrhoeae isolates from 15 persons infected multiple times with the same serovar were compared using por gene sequencing, opa-typing, and arbitrarily primed-polymerase chain reaction. All three molecular techniques were more discriminatory than serotyping and identified differences between some isolates belonging to the same serovar. Although there were differences among Por sequences within some serovars, 10 of 15 subjects became reinfected with gonococci expressing identical Por proteins. Sequence analysis of por genes revealed evidence of horizontal genetic exchange and point mutations in potential surface-exposed regions during passage in the community.     

Impact of either elevated or decreased levels of cytochrome bd expression on Shigella flexneri virulence

Shigella spp. are the major cause of bacillary dysentery worldwide. The pathogenic process involves bacterial invasion and lysis of the phagocytic vacuole, followed by replication and movement within the cell cytoplasm and, ultimately, spread directly into adjacent cells. This study demonstrates that S. flexneri cytochrome bd expression is necessary for normal intracellular survival and virulence. Cytochrome bd is one of two terminal oxidases in the bacterial respiratory chain that reduce molecular oxygen to water, utilizing intermediates shuttled through the electron transport chain. S. flexneri mutants that contain a disruption in the cydC locus, which leads to defective cytochrome bd expression, or in the riboflavin (ribE) or ubiquinol-8 (ubiH) biosynthetic pathway, which leads to elevated cytochrome bd expression, were evaluated in intracellular survival and virulence assays. The cydC mutant formed significantly smaller plaques, had significantly decreased intracellular survival, and had a 100-fold increase in lethal dose for mice compared with the wild type. The ribE and ubiH mutants each formed significantly larger plaques and had a 10-fold decrease in lethal dose for mice compared with the wild type. The data indicate that expression of cytochrome bd is required for S. flexneri intracellular survival and virulence.     

Procedural results and late clinical outcomes following multivessel coronary stenting

OBJECTIVES: To evaluate in-hospital and long-term clinical outcomes in a large consecutive series of patients undergoing percutaneous multivessel stent intervention. BACKGROUND: High restenosis and recurrent angina rates have limited the clinical outcomes of multivessel coronary angioplasty before stents were available to improve angioplasty results. METHODS: We evaluated in-hospital and long-term clinical outcomes (death, Q-wave myocardial infarction [MI], and repeat revascularization rates at one year) in 398 consecutive patients treated with coronary stents in two (94% of patients) or three native arteries, compared to 1,941 patients undergoing stenting procedure in a single coronary artery between January 1, 1994 and August 29, 1997. RESULTS: Overall procedural success was obtained in 96% of patients with two- or three-vessel stenting and in 970% of patients with single-vessel stent intervention (p = 0.36). Procedural complications were also similar (3.8% for multivessel versus 2.9% for single vessel, p = 0.14). During follow up, target lesion revascularization was 15% in multivessel and 16% in single-vessel interventions (p = 0.38), and repeat revascularization (calculated per treated patient) was also similar for both groups (20% vs. 21%, p = 0.73). There was no difference in death (1.4% vs. 0.7%, p = 0.26), and Q-wave MI (1.2% vs. 0%, p = 0.02) was lower following multivessel interventions. Overall cardiac event-free survival was similar for both groups (p = 0.52). CONCLUSIONS: Unlike previous conventional angioplasty experiences, multivessel stenting has (1) similar in-hospital procedural success and major complication rates and (2) similar long-term (one year) clinical outcomes compared with single-vessel stenting. Thus, stents may be a viable therapeutic strategy in carefully selected patients with multivessel coronary disease.