Identification and structural elucidation of new caprazamycins from Streptomyces sp. MK730-62F2 by liquid chromatography/electrospray ionization tandem mass spectrometry

The development of reliable analytic methods, capable of separating mixtures of secondary metabolites as well as providing structural information, is essential for the investigation of secondary metabolites, e.g. from Streptomyces. Here we report a liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method using a triple quadrupole mass analyzer for the structural elucidation of caprazamycins and liposidomycins from culture extracts of the wild-type producer strains. Comparison of the fragmentation patterns in positive as well as in negative ionization mode revealed several characteristic product ions used for identification of six new caprazamycins. Furthermore, a chromatographic method for the purification of nucleosides from cell cultures using a boronic acid gel was adapted for the partial purification of the culture extracts.     

Resonance Raman studies of photochemical molecular devices for multielectron storage

Resonance Raman spectroscopy was utilized for the first time to characterize the nature of the ¹metal‐to‐ligand charge transfer (MLCT) state of a ruthenium complex containing the redoxactive tetraazatetrapyrido‐pentacene (tatpp) ligand. The presented results show that the long‐wavelength absorption is originating from transitions involving the terminal phenanthroline and the tatpp ligands. Copyright © 2008 John Wiley & Sons, Ltd.     

Investigation of substitution effects on novel Ru–dppz complexes by Raman spectroscopy in combination with DFT methods

We present a combined Raman–density functional theory (DFT) study of novel dipyridophenazine (dppz) derivatives and their Ru–bipyridine complexes. Our results show that the molecular architecture of dppz and its Ru complexes can be considered to consist of two independent moieties, the structural ground state properties of which can be tuned independently by means of side‐specific substitution. These results are expected to be of importance for the design of highly specific dppz‐based DNA sensors. Methodologically, the results presented in this paper highlight the power of a combined Raman–DFT approach to unravel the details of the structural properties of complex molecules. Copyright © 2009 John Wiley & Sons, Ltd.     

Differentiation of Monofloral Honey Using Volatile Organic Compounds by HS-GCxIMS

Honey is a natural product and can be described by its botanical origin, determined by the plants from which the bees collect nectar. It significantly influences the taste of honey and is often used as a quality criterion. Unfortunately, this opens up the possibility of food fraud. Currently, various methods are used to check the authenticity of monofloral honey. The laborious, manual melissopalynology is considered an essential tool in the verification process. In this work, the volatile organic compounds obtained from the headspace of honey are used to prove their authenticity. The headspace of 58 honey samples was analyzed using a commercial easy-to-use gas chromatography-coupled ion mobility spectrometer with a headspace sampler (HS-GCxIMS). The honey samples were successfully differentiated by their six different botanical origins using specific markers with principal component analysis in combination with linear discriminant analysis. In addition, 15 honey-typical compounds were identified using measurements of reference compounds. Taking a previously published strategy, retention times of marker compounds were correlated with GC-coupled mass spectrometry (GC-MS) measurements to assist in the identification process.     

Multiple Triplet Metal-Centered Jahn-Teller Isomers Determine Temperature-Dependent Luminescence Lifetimes in [Ru(bpy)3]2+

Understanding the factors that determine the luminescence lifetime of transition metal compounds is key for applications in photocatalysis and photodynamic therapy. Here we show that for (bpy = 2,2’-bipyridine), the generally accepted idea that emission lifetimes can be controlled optimizing the energy barrier from the emissive triplet metal-to-ligand charge-transfer (³MLCT) state to the thermally-activated triplet metal-centered (³MC) state or the energy gap between both states is a misconception. Further, we demonstrate that considering a single relaxation pathway determined from the minimum that is lowest in energy leads to wrong temperature-dependent emission lifetimes predictions. Instead, we obtain excellent agreement with experimental temperature-dependent lifetimes when an extended kinetic model that includes all the pathways related to multiple Jahn–Teller isomers and their effective reaction barriers is employed. These concepts are essential to correctly design other luminescent transition metal complexes with tailored emission lifetimes based on theoretical predictions.     

Implementation of Thermomechanical Coupling for Shape Memory Alloys into the Finite Element Method

NiTi alloys open up new fields of application on the basis of their distinctive thermomechanical properties. Many options of practical application of shape memory alloys are imaginable. For example catheters or stents made of NiTi play an important role in medical technology. Thus the further development and optimisation of simulation tools for shape memory alloys (SMA) structures will play an important role in the future. Based on the powerful material model of Helm [1] the present contribution focuses on the coupling between mechanical and thermal fields. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Solid-Shell Finite Elements for Tesselated Geometries

Sandwich structures made of sheets of composite materials are in widespread use, particularly in the transportation industry. Finite Element simulation of the thin, tesselated structures with complex, three-dimensional material behaviour is a challenging task for the underlying element technology. In particular, frequently used linear isoparametric approaches exhibit unphysical stiffening phenomena. Recent developments in solid-shell finite element technology aim to overcome these undesirable effects. Here, they are applied to an example of a corrugated sandwich core under transversal compression. A study of convergence is conducted with respect to commercially available shell and solid finite elements, and their ability to reproduce the bending dominated deformation state. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)