Non-covalent interactions in organotin(IV) derivatives of 5,7-ditertbutyl- and 5,7-diphenyl-1,2,4-triazolo[1,5-a]pyrimidine as recognition motifs in crystalline self- assembly and their in vitro antistaphylococcal activity

Non-covalent interactions are known to play a key role in biological compounds due to their stabilization of the tertiary and quaternary structure of proteins [1]. Ligands similar to purine rings, such as triazolo pyrimidine ones, are very versatile in their interactions with metals and can act as model systems for natural bio-inorganic compounds [2]. A considerable series (twelve novel compounds are reported) of 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) and 5,7-diphenyl- 1,2,4-triazolo[1,5-a]pyrimidine (dptp) were synthesized and investigated by FT-IR and 119Sn M\uf6ssbauer in the solid state and by 1H and 13C NMR spectroscopy, in solution [3]. The X-ray crystal and molecular structures of Et2SnCl2(dbtp)2 and Ph2SnCl2(EtOH)2(dptp)2 were described, in this latter pyrimidine molecules are not directly bound to the metal center but strictly H-bonded, through N(3), to the -OH group of the ethanol moieties. The network of hydrogen bonding and aromatic interactions involving pyrimidine and phenyl rings in both complexes drives their self-assembly. Noncovalent interactions involving aromatic rings are key processes in both chemical and biological recognition, contributing to overall complex stability and forming recognition motifs. It is noteworthy that in Ph2SnCl2(EtOH)2(dptp)2 \u3c0\u2013\u3c0 stacking interactions between pairs of antiparallel triazolopyrimidine rings mimick basepair interactions physiologically occurring in DNA (Fig.1). M\uf6ssbauer spectra suggest for Et2SnCl2(dbtp)2 a distorted octahedral structure, with C-Sn-C bond angles lower than 180\ub0. The estimated angle for Et2SnCl2(dbtp)2 is virtually identical to that determined by X-ray diffraction. Ph2SnCl2(EtOH)2(dptp)2 is characterized by an essentially linear C-Sn-C fragment according to the X-ray all-trans structure. The compounds were screened for their in vitro antibacterial activity on a group of reference staphylococcal strains susceptible or resistant to methicillin and against two reference Gramnegative pathogens [4] . We tested the biological activity of all the specimen against a group of staphylococcal reference strains (S. aureus ATCC 25923, S. aureus ATCC 29213, methicillin resistant S. aureus 43866 and S. epidermidis RP62A) along with Gram-negative pathogens (P. aeruginosa ATCC9027 and E. coli ATCC25922). Ph2SnCl2(EtOH)2(dptp)2 showed good antibacterial activity with a MIC value of 5 \u3bcg mL-1 against S. aureus ATCC29213 and also resulted active against methicillin resistant S. epidermidis RP62A

Paramagnetic NMR in solution and the solid state

The field of paramagnetic NMR has expanded considerably in recent years, both in solution and the solid state. This review addresses both the theoretical description of paramagnetic NMR, and the way in which it is currently practised. We provide a review of the theory of the NMR parameters of systems in both solution and the solid state. Here we unify the different languages used by the NMR, EPR, quantum chemistry/DFT, and magnetism communities to provide a comprehensive and coherent theoretical description. We cover the theory of the paramagnetic shift and shift anisotropy in solution both in the traditional formalism in terms of the magnetic susceptibility tensor, and using a more modern formalism employing the relevant EPR parameters, such as are used in first-principles calculations. In addition we examine the theory first in the simple non-relativistic picture, and then in the presence of spin-orbit coupling. These ideas are then extended to a description of the paramagnetic shift in periodic solids, where it is necessary to include the bulk magnetic properties, such as magnetic ordering at low temperatures. The description of the paramagnetic shift is completed by describing the current understanding of such shifts due to lanthanide and actinide ions. We then examine the paramagnetic relaxation enhancement, using a simple model employing a phenomenological picture of the electronic relaxation, and again using a more complex state-of-the-art theory which incorporates electronic relaxation explicitly. An additional important consideration in the solid state is the impact of bulk magnetic susceptibility effects on the form of the spectrum, where we include some ideas from the field of classical electrodynamics. We then continue by describing in detail the solution and solid-state NMR methods that have been deployed in the study of paramagnetic systems in chemistry, biology, and the materials sciences. Finally we describe a number of case studies in paramagnetic NMR that have been specifically chosen to highlight how the theory in part one, and the methods in part two, can be used in practice. The systems chosen include small organometallic complexes in solution, solid battery electrode 3 materials, metalloproteins in both solution and the solid state, systems containing lanthanide ions, and multi-component materials used in pharmaceutical controlled-release formulations that have been doped with paramagnetic species to measure the component domain sizes.This work was supported by the People Programme (Marie Curie Actions Initial Training Networks (ITN)) of the European Union’s Seventh Framework Programme FP7/2007-2013/ under REA grant agreement no. 317127, the “pNMR” project. AJP received funding from the Swedish Research Council (Vetenskapsrådet) (2016-03441)

Bio-effectors for improved growth, nutrient acquisition and disease resistance of crops

Recent scientific approaches to sustain agricultural production in face of a growing world food demand, limited natural resources, and ecological concerns have been focusing on biological processes to support soil fertility and healthy plant growth. In this context, the use of bio-effectors, comprising living (micro-) organisms and active natural compounds, has been receiving increasing attention. In contrast to conventional fertilizers and pesticides, the effectiveness of bio-effectors is essentially not based on the substantial direct input of mineral plant nutrients, neither in inorganic nor organic forms, nor of a-priori toxic compounds. Their direct or indirect effects on plant performance are rather based on the functional implementation or activation of biological mechanisms, in particular those interfering with soil-plant-microbe interactions. The general objective of the present research work was to improve the empirical and conceptual understanding concerning the utilization of bio-effectors in agricultural practice, following the principles of plant growth stimulation, bio-fertilization and bio-control. One main aspect of investigation was the application of bio-effectors to improve the efficiency of phosphorus (P) acquisition by the plant. Promising bio-preparations based on microbial inoculants (e.g. Bacillus, Pseudomonas, Trichoderma species) as well as natural compounds (e.g. algae extracts, humic acids) were tested in screening assays, greenhouse, and field experiments to characterize their potential effectiveness under varying environmental conditions. The most significant effects on plants appeared under severely low phosphate availability, but even under controlled conditions, bio-effectors required a narrow range of conductive environmental settings to reveal their potential effectiveness. Another focus of research was the application of bio-effectors to control soil borne pathogens, which typically appear in unsound crop rotations. Emphasis was set on take-all disease in wheat induced by the fungus Gaeumannomyces graminis. While the effectiveness of oat precrops to control take-all in subsequent wheat has been attributed to microbial changes and enhanced manganese (Mn) availability in soils, the take-all fungus is known to decrease the availability of Mn by oxidation. Against this background, the effectiveness of oat precrops and alternative crop management strategies to improve the Mn status and suppress the severity of take-all in wheat was investigated under controlled and field conditions. In conclusion, none of the tested supplemental treatments, such the application of microbial bio-effectors, stabilized ammonium or manganese fertilizers, could fully substitute for the multiple effectiveness of oat precrops, which was further confirmed by the results of a field experiment. Finally, some general conclusions and perspectives are summarized. Selected bio-effectors showed a strong capacity to improve the nutrient acquisition and healthy growth of crop plants under controlled conditions, but not in field experiments. However, even under controlled conditions the strongest effects occurred when plants were exposed to abiotic or biotic stresses, such as severely limited P availability or pathogen infestation of the soil substrate, still restricting plant growth to unproductive levels. Facing this situation, there is no perspective to improve the field efficiency of promising bio-effectors applications as a stand-alone approach. The only chance to develop viable alternatives to the conventional use of fertilizers or pesticides, for an ecological intensification of agriculture that maintains high yield levels, seems to be a reasonable integration of bio-effectors into the whole crop management of sound agricultural practice.Angesichts eines weltweit wachsenden Bedarfs an Nahrungsmitteln, begrenzter natürlicher Ressourcen und ökologischer Probleme streben neuere wissenschaftliche Ansätze zur nachhaltigen Gestaltung der Landwirtschaft verstärkt die Nutzung biologischer Prozesse zur Föderung der Bodenfruchtbarkeit und eines gesunden Kulturpflanzenwachstums an. In diesem Zusammenhang hat der Einsatz von Bio-Effektoren, einschließlich lebender (Mikro-)Organismen und wirkaktiver Naturstoffe, wachsendes Interesse gefunden. Im Gegensatz zu konventionellen Düngemitteln und Pestiziden beruht die Wirksamkeit von Bio-Effektoren nicht auf dem substantiellen Direkteintrag von Pflanzennährstoffen, weder in anorganischer noch organischer Form, noch von a priori toxischen Stoffen. Die direkten oder indirekten Wirkungen von Bio-Effektoren auf die Pflanze basieren vielmehr auf der Implementierung oder Aktivierung von biologischen Wirkungsmechanismen, insbesondere solcher die mit den Interaktionen von Boden, Pflanze und Mikroorganismen interferieren. Ziel der vorliegenden Arbeit war es, das Verständnis zur Nutzung von Bio-Effektoren in der landwirtschaftlichen Praxis anhand der prinzipiellen Wirkungskategorien von direkter Stimulans des Pflanzenwachstums, biologischer Pflanzenernährung (bio-fertilization) und biologischem Pflanzenschutz (bio-control) zu erweitern. Ein Hauptaspekt galt der Anwendung von Bio-Effektoren um die Aneignungseffizienz von Phosphor (P) durch die Pflanze zu steigern. Aussichtsreiche Präparate, basierend auf mikrobiellen Inokula (z.B. Bacillus, Pseudomonas, Trichoderma Spezies) als auch Naturstoffen (z.B. Algenextrakte, Huminsäuren), wurden in Screeningassays, Gewächshaus- und Feldversuchen getestet um ihr Wirkungspotential unter variablen Umweltbedingungen zu charakterisieren. Die stärksten Effekte traten unter Bedingungen mit sehr geringer Phosphatverfügbarkeit auf, jedoch selbst unter kontrollierten Bedingungen war der Einfluss förderlicher und teilweise eng bestimmter Umweltfaktoren notwendig um die Wirksamkeit von Bio-Effektoren zu zeigen. Ein weiteres Thema war der Einsatz von Bio-Effektoren zur Bekämpfung bodenbürtiger Krankheitserreger, welche durch unausgewogene Fruchtfolgen gefördert werden. Die Untersuchungen befassten sich insbesondere mit der Schwarzbeinigkeit des Weizens, einer bedeutenden Wurzelkrankheit hervorgerufen durch den Pilz Gaeumannomyces graminis. Eine effektive Vorfrucht zur Bekämpfung der Schwarzbeinigkeit ist Hafer, was in Zusammenhang mit mikrobiellen Veränderungen im Boden und einer erhöhten Verfügbarkeit von Mangan (Mn) für die Folgefrucht Weizen gestellt wurde. Vor diesem Hintergrund wurde die Wirksamkeit von Hafer als Vorfrucht im Vergleich mit alternativen Maßnahmen des pflanzenbaulichen Managements zur Steigerung der Mn-Versorgung und Bekämpfung der Schwarzbeinigkeit in Weizen untersucht. Fazit war, daß keine der getesten Alternativmaßnahmen, wie die Anwendung mikrobieller Bio-Effektoren, stabilisierten Ammonium- oder Mangandüngers, die vielseitige Vorfruchtwirkung von Hafer vollständig substituieren konnte, was auch durch die Ergebnisse eines Feldversuches bestätigt wurde. Abschließend folgen generelle Schlussfolgerungen aus der vorliegenden Arbeit und sich daraus ergebende Perspektiven zur Nutzung von Bio-Effektoren. Ausgewählte Bio-Effektoren zeigten unter kontrollierten Bedingungen ein hohes Wirkungspotential zur Förderung der Nährstoffaneignung und des gesunden Wachstums von Kulturpflanzen, nicht jedoch in Feldversuchen. Zudem waren die stärksten Effekte dann zu beobachten, wenn die Pflanzen abiotischen oder biotischen Stresssituationen, wie stark limitierter P-Verfügbarkeit oder einem pathogenbelasteten Bodensubstrat, ausgesetzt waren, welche das Pflanzenwachstum auch weiterhin auf ein unproduktives Maß beschränkten. Diese Ergebnisse eröffnen keine Perspektive den praktischen Nutzen von Bio-Effektoren durch Einzelmaßnahmen zu steigern. Vielmehr schein der einzig erfolgversprechende Ansatz leistungsfähige Alternativen zum konventionellen Einsatz von Düngemitteln und Pestiziden für eine ökologische Intensivierung der Agrarproduktion auf hohem Ertragsniveau zu entwickeln, eine sinnvolle Integration von Bio-Effektoren in das gesamte pflanzenbauliche Management einer fachgerechten Landwirtschaft zu sein