Development of a defined medium for the heterotrophic cultivation of Metallosphaera sedula.

The heterotrophic cultivation of extremophilic archaea still heavily relies on complex media. However, complex media are associated with unknown composition, high batch-to-batch variability, potential inhibiting and interfering components, as well as regulatory challenges, hampering advancements of extremophilic archaea in genetic engineering and bioprocessing. For Metallosphaera sedula, a widely studied organism for biomining and bioremediation and a potential production host for archaeal ether lipids, efforts to find defined cultivation conditions have still been unsuccessful.

Dynamic behaviour of platinum and copper dopants in gold nanoclusters supported on ceria catalysts.

Understanding the behaviour of active catalyst sites at the atomic level is crucial for optimizing catalytic performance. Here, the evolution of Pt and Cu dopants in Au clusters on CeO supports is investigated in the water-gas shift (WGS) reaction, using operando XAFS and DRIFTS. Different behaviour is observed for the Cu and Pt dopants during the pretreatment and reaction.

Directing Intrinsic Chirality in Gold Nanoclusters: Preferential Formation of Stable Enantiopure Clusters in High Yield and Experimentally Unveiling the "Super" Chirality of Au.

Chiral gold nanoclusters offer significant potential for exploring chirality at a fundamental level and for exploiting their applications in sensing and catalysis. However, their widespread use is impeded by low yields in synthesis, tedious separation procedures of their enantiomeric forms, and limited thermal stability. In this study, we investigated the direct synthesis of enantiopure chiral nanoclusters using the chiral ligand 2-MeBuSH in the fabrication of Au, Au, and Au nanoclusters.

Electrospray Ionization Tandem Mass Spectrometric Study of Selected Phosphine-Based Ligands for Catalytically Active Organometallics.

Selected organometallic compounds are nowadays extensively used as highly efficient catalysts in organic synthesis. A great variety of different ligand systems exists, of which phosphine-based ligands are a significant subgroup. While mass spectrometry, predominantly electrospray ionization mass spectrometry (ESI-MS), is a standard analytical technique for the identification of new ligands and their metal complexes, there is little information on the behavior of phosphine-based ligands/molecules by electrospray ionization collision-induced dissociation tandem mass spectrometry (ESI-CID-MS/MS) at low collision energies (<100 eV) in the literature.

The role of lipid oxidation on electrical properties of planar lipid bilayers and its importance for understanding electroporation.

Electroporation is a useful tool for the manipulation with the cell membrane permeability. Underlying physicochemical processes taking place at the molecular level during electroporation are relatively well studied. However, various processes remain unknown, one of them is lipid oxidation, a chain reaction that causes degradation of lipids, and might explain the long-lasting membrane permeability after the electric field has ceased.

Fluorescence signal of proteins in birch pollen distorted within its native matrix: Identification of the fluorescence suppressor quercetin-3-O-sophoroside.

The properties of biogenic aerosol strongly depend on the particle's proteinaceous compounds. Proteins from primary biological aerosol particles (PBAPs) can cause allergic reactions in the human respiratory system or act as ice and condensation nuclei in clouds. Consequently, these particles have high impact on human health and climate.

Characterization of selected organometallic compounds by electrospray ionization- and matrix-assisted laser desorption/ionization-mass spectrometry using different types of instruments: Possibilities and limitations.

Rationale: Organometallic compounds are becoming increasingly important in their industrial application as catalysts. Mass spectrometry is an essential tool for the structural confirmation of such organometallics. Because the analysis of this class of molecules can be challenging, the ionization behavior and structural confirmation of selected transition metal catalysts are described in this work.

Manganese-Catalyzed Dehydrogenative Silylation of Alkenes Following Two Parallel Inner-Sphere Pathways.

We report on an additive-free Mn(I)-catalyzed dehydrogenative silylation of terminal alkenes. The most active precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex [Mn(dippe)(CO)(CHCHCH)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn-alkyl bond to yield an acyl intermediate which undergoes rapid Si-H bond cleavage of the silane HSiR forming the active 16e Mn(I) silyl catalyst [Mn(dippe)(CO)(SiR)] together with liberated butanal.

Structural and Electronic Properties of Iron(0) PNP Pincer Complexes.

In the present work we have prepared and fully characterized several Fe(0) complexes of the type [Fe(PNP)(CO)] treating Fe(II) complexes [Fe(PNP)(Cl)] with KC in the presence of carbon monoxide. While complexes [Fe(PNP-Pr)(CO)], [Fe(PNP-Pr)(CO)] adopt a trigonal bipyramidal geometry, the bulkier and more electron rich [Fe(PNP-Bu)(CO)] is closer to a square pyramidal geometry. Mössbauer spectra showed isomer shifts very close to 0 and similar to those reported for Fe(I) systems.

Synthesis and Catalytic Reactivity of Cobalt Pincer Nitrosyl Hydride Complexes.

The synthesis, characterization, and catalytic activity of low-spin {CoNO} pincer complexes of the type [Co(PCP)(NO)(H)] are described. These compounds are obtained either by reacting [Co(PCP)(κ-BH)] with NO and EtN or, alternatively, by reacting [Co(PCP)(NO)] with boranes, such as NH·BH in solution. The five-coordinate, diamagnetic Co(III) complex [Co(PCP-Pr)(NO)(H)] was found to be the active species in the hydroboration of alkenes with anti-Markovnikov selectivity.

Dynamics of Pd Dopant Atoms inside Au Nanoclusters during Catalytic CO Oxidation.

Doping gold nanoclusters with palladium has been reported to increase their catalytic activity and stability. PdAu nanoclusters, with the Pd dopant atom located at the center of the Au cluster core, were supported on titania and applied in catalytic CO oxidation, showing significantly higher activity than supported monometallic Au nanoclusters. After pretreatment, DRIFTS spectroscopy detected CO adsorbed on Pd during CO oxidation, indicating migration of the Pd dopant atom from the Au cluster core to the cluster surface.

Ligand engineering of immobilized nanoclusters on surfaces: ligand exchange reactions with supported Au(PPh)Br.

The properties of gold nanoclusters, apart from being size-dependent, are strongly related to the nature of the protecting ligand. Ligand exchange on Au nanoclusters has been proven to be a powerful tool for tuning their properties, but has so far been limited to dissolved clusters in solution. By supporting the clusters previously functionalized in solution, it is uncertain that the functionality is still accessible once the cluster is on the surface.

The influence of the specific growth rate on the lipid composition of Sulfolobus acidocaldarius.

Archaeal lipids are constituted of two isoprenoid chains connected via ether bonds to glycerol in the sn-2, 3 position. Due to these unique properties archaeal lipids are significantly more stable against high temperature, low pH, oxidation and enzymatic degradation than conventional lipids. Additionally, in members of the phylum Crenarchaeota condensation of two (monopolar) archaeal diether lipids to a single (bipolar) tetraether lipid as well as formation of cyclopentane rings in the isoprenoid core strongly reduce permeability of the crenarchaeal membranes.

Nano electrospray differential mobility analysis based size-selection of liposomes and very-low density lipoprotein particles for offline hyphenation to MALDI mass spectrometry.

Gas-phase electrophoresis of single-charged analytes (nanoparticles) enables their separation according to the surface-dry particle size (Electrophoretic Mobility Diameter, EMD), which corresponds to the diameter of spherical shaped particles. Employing a nano Electrospray Differential Mobility Analyzer (nES DMA), also known as nES Gas-phase Electrophoretic Mobility Molecular Analyzer (nES GEMMA), allows sizing/size-separation and determination of particle-number concentrations. Separations are based on a constant high laminar sheath flow and a tunable, orthogonal electric field enabling scanning of EMDs in the nanometer size range.

Study of metabolism and identification of productive regions in filamentous fungi via spatially resolved time-of-flight secondary ion mass spectrometry.

Filamentous fungi are well-established production hosts that feature a strong interconnection between morphology, physiology, and productivity. For penicillin production in Penicillium chrysogenum, industrial processes frequently favor a pellet morphology comprising compact hyphal agglomerates. Inherently these tightly packed entanglements lead to inactive, degrading sections within the pellet's core because of limitations.

Investigations of the generality of quaternary ammonium salts as alkylating agents in direct C-H alkylation reactions: solid alternatives for gaseous olefins.

C-H alkylation reactions using short chain olefins as alkylating agents could be operationally simplified on the lab scale by using quaternary ammonium salts as precursors for these gaseous reagents: Hofmann elimination delivers in situ the desired alkenes with the advantage that the alkene concentration in the liquid phase is high. In case a catalytic system did not tolerate the conditions for Hofmann elimination, a very simple spatial separation of both reactions, Hofmann elimination and direct alkylation, was achieved to circumvent possible side reactions or catalyst deactivation. Additionally, the truly catalytically active species of a rhodium(i) mediated alkylation reaction could be identified by using this approach.

Rhenium-Catalyzed Dehydrogenative Coupling of Alcohols and Amines to Afford Nitrogen-Containing Aromatics and More.

An efficient synthesis of quinolines, pyrimidines, quinoxalines, pyrroles, and aminomethylated aromatic compounds catalyzed by a well-defined Re(I) PNP pincer complex is described. All reactions proceed with liberation of dihydrogen and elimination of water. Under optimized reaction conditions a wide range of organic functional groups are tolerated.

In-depth analysis of crocetin ester glycosides from dried/processed stigmas of Crocus sativus L. by HPLC-ESI-MS (n = 2, 3).

Introduction: Saffron stigmas from Crocus sativus L. (Iridaceae) are used as a drug in folk medicine, as a food additive and as a dying agent for at least 3500 years. Despite this long-term use the chemical composition of saffron seems still to be not fully known.

Development of an accelerated artificial ageing method for the characterization of degradation products of antioxidants in lubricants by mass spectrometry.

The understanding of ageing mechanisms of antioxidants in base oils is indispensable for the development of improved lubricants. In this study, a novel artificial ageing method based on the application of peroxide as oxidant is presented for improved monitoring of thermo-oxidative degradation processes in combination with mass spectrometry. Model oils containing aminic and phenolic antioxidants were aged and chemical structures of their oxidation products were elucidated by ultrahigh performance liquid chromatography and electrospray ionization high resolution (Orbitrap) mass spectrometry.

Formation of Mono Oxo Molybdenum(IV) PNP Pincer Complexes: Interplay between Water and Molecular Oxygen.

The synthesis of cationic mono oxo Mo PNP pincer complexes of the type [Mo(PNP-Pr)(O)X] (X = I, Br) from [Mo(PNP-Pr)(CO)X] is described. These compounds are coordinatively unsaturated and feature a strong Mo≡O triple bond. The formation of these complexes proceeds via cationic 14e intermediates [Mo(PNP-Pr)(CO)X] and requires both molecular oxygen and water.

A laser desorption ionization/matrix-assisted laser desorption ionization target system applicable for three distinct types of instruments (LinTOF/curved field RTOF, LinTOF/RTOF and QqRTOF) with different performance characteristics from three vendors.

Rationale: We have developed a target system which enables the use of only one target (i.e. target preparation set) for three different laser desorption ionization (LDI)/matrix-assisted laser desorption ionization (MALDI) mass spectrometric instruments.

Manganese-Catalyzed Aminomethylation of Aromatic Compounds with Methanol as a Sustainable C1 Building Block.

This study represents the first example of a manganese-catalyzed environmentally benign, practical three-component aminomethylation of activated aromatic compounds including naphtols, phenols, pyridines, indoles, carbazoles, and thiophenes in combination with amines and MeOH as a C1 source. These reactions proceed with high atom efficiency via a sequence of dehydrogenation and condensation steps which give rise to selective C-C and C-N bond formations, thereby releasing hydrogen and water. A well-defined hydride Mn(I) PNP pincer complex, recently developed in our laboratory, catalyzes this process in a very efficient way, and a total of 28 different aminomethylated products were synthesized and isolated yields of up to 91%.

Three Different Reactions, One Catalyst: A Cu(I) PNP Pincer Complex as Catalyst for C-C and C-N Cross-Couplings.

An air-stable, thermally robust, and well-defined Cu(I) PNP pincer complex based on the 2,6-diaminopyridine scaffold is described. This complex is an active catalyst for the cross-couplings of a range of aryl and heteroaryl (including benzoxazole, thiazole, pyridine, and thiophene) halides with different organomagnesium reagents, alkynes, and aryl-amines giving excellent to good isolated yields.

Sustainable Synthesis of Quinolines and Pyrimidines Catalyzed by Manganese PNP Pincer Complexes.

This study represents the first example an environmentally benign, sustainable, and practical synthesis of substituted quinolines and pyrimidines using combinations of 2-aminobenzyl alcohols and alcohols as well as benzamidine and two different alcohols, respectively. These reactions proceed with high atom efficiency via a sequence of dehydrogenation and condensation steps that give rise to selective C-C and C-N bond formations, thereby releasing 2 equiv of hydrogen and water. A hydride Mn(I) PNP pincer complex recently developed in our laboratory catalyzes this process in a very efficient way.

High-spin iron(II) complexes with mono-phosphorylated 2,6-diaminopyridine ligands.

Abstract: Several new monophosphorylated 2,6-diaminopyridine ligands bearing PPr and PBu units (PN-Pr, PN-Bu, PN-Pr, and PN-Pr) are prepared by treatment of the respective 2,6-diaminopyridines with the chlorophosphines PPrCl and PBuCl in the presence of a base. Treatment of anhydrous FeCl with 1 equiv of these afforded the tetracoordinated coordinatively unsaturated 14e complexes [Fe(κ-PN-Pr)Cl] and [Fe(κ-PN-Bu)Cl], while with PN-Pr and PN-Pr a phosphine transfer reaction of a second PN ligand took place to yield the known PNP pincer complexes [Fe(κ-PNP-Pr)Cl] and [Fe(κ-PNP-Pr)Cl]. The four-coordinate complexes [Fe(κ-PN-Pr)Cl] and [Fe(κ-PN-Bu)Cl] did not react with CO and the formation of iron PNC pincer complexes was not observed.