Trimesityltriangulene: a persistent derivative of Clar's hydrocarbon

Triangulene, known as Clar’s hydrocarbon, is a prototypical non-Kekule ́ diradical comprised of six benzenoid rings fused in a trian-gular shape. We synthesized and characterized its trimesityl derivative, illustrating that three bulky substituents installed in the centers of the zigzag edges suffice to protect all reactive positions. This work brings prospects to use triangulene and its open-shell analogs in spintronic materials via solution-phase synthesis

Fucoidan Does Not Exert Anti-Tumorigenic Effects on Uveal Melanoma Cell Lines

Background. The polysaccharide fucoidan is widely investigated as an anti-cancer agent. Here, we tested the effect of fucoidan on uveal melanoma cell lines. Methods. The effect of 100 µM fucoidan was investigated on five cell lines (92.1, Mel270 OMM1, OMM2.3, OMM2.5) and of 1 µg/mL–1 mg/mL fucoidan in two cell lines (OMM1, OMM2.3). Cell proliferation and viability were investigated with a WST-1 assay, migration in a wound healing (scratch) assay. Vascular Endothelial Growth Factor (VEGF) was measured in ELISA. Angiogenesis was evaluated in co-cultures with endothelial cells. Cell toxicity was induced by hydrogen-peroxide. Protein expression (Akt, ERK1/2, Bcl-2, Bax) was investigated in Western blot. Results. Fucoidan increased proliferation in two and reduced it in one cell line. Migration was reduced in three cell lines. The effect of fucoidan on VEGF was cell type and concentration dependent. In endothelial co-culture with 92.1, fucoidan significantly increased tubular structures. Moreover, fucoidan significantly protected all tested uveal melanoma cell lines from hydrogen-peroxide induced cell death. Under oxidative stress, fucoidan did not alter the expression of Bcl-2, Bax or ERK1/2, while inducing Akt expression in 92.1 cells but not in any other cell line. Conclusion. Fucoidan did not show anti-tumorigenic effects but displayed protective and pro-angiogenic properties, rendering fucoidan unsuitable as a potential new drug for the treatment of uveal melanoma

The impact of spin–orbit coupling on fine-structure and spin polarisation in photoexcited porphyrin triplet states

The photoexcited triplet states of porphyrins show great promise for applications in the fields of opto-electronics, photonics, molecular wires, and spintronics. The magnetic properties of porphyrin triplet states are most conveniently studied by time-resolved continuous wave and pulse electron spin resonance (ESR). This family of techniques is singularly able to probe small yet essential details of triplet states: zero-field splittings, g-anisotropy, spin polarisation, and hyperfine interactions. These characteristics are linked to spin–orbit coupling (SOC) which is known to have a strong influence on photophysical properties such as intersystem crossing rates. The present study explores SOC effects induced by the presence of Pd2+ in various porphyrin architectures. In particular, the impact of this relativistic interaction on triplet state fine-structure and spin polarisation is investigated. These properties are probed using time-resolved ESR complemented by electron-nuclear double resonance. The findings of this study could influence the future design of molecular spintronic devices. The Pd2+ ion may be incorporated into porphyrin molecular wires as a way of controlling spin polarisation

Enhanced Intersystem Crossing and Transient Electron Spin Polarization in a Photoexcited Pentacene-Trityl Radical

Identifying and characterizing systems that generate well-defined states with large electron spin polarization is of high interest for applications in molecular spintronics, high-energy physics and magnetic resonance spectroscopy. The generation of electron spin polarization on free-radical substituents tethered to pentacene derivatives has recently gained a great deal of interest for its applications in molecular electronics. After photoexcitation of the chromophore, pentacene-radical derivatives can rapidly form spin-polarized triplet excited states through enhanced intersystem crossing. Under the right conditions, the triplet spin polarization, arising from mS-selective intersystem crossing rates, can be transferred to the tethered stable radical. The efficiency of this spin polarization transfer depends on many factors: local magnetic and electric fields, excited state energetics, molecular geometry, and spin-spin coupling. Here we present transient electron paramagnetic resonance (EPR) measurements on three pentacene derivatives tethered to Finland trityl, BDPA or TEMPO radicals to explore the influence of the nature of the radical on the spin polarization transfer. We observe efficient polarization transfer between the pentacene excited triplet and the trityl radical, but do not observe the same for the BDPA and TEMPO derivatives. The polarization transfer behavior in the pentacene-trityl system is also investigated in different glassy matrices and is found to depend markedly on the solvent used. The EPR results are rationalized with the help of femtosecond and nanosecond transient absorption measurements, yielding complementary information on the excited-state dynamics of the three pentacene derivatives. Notably, we observe a two orders of magnitude difference in the timescale of triplet formation between the pentacene-trityl system and the pentacene systems tethered with the BDPA and TEMPO radicals

Die komplexe Virosphäre von Knoblauch (Allium sativum)

Der Virusstatus und die Ertragsstabilität der für den ökologischen Anbau interessanten Knoblauchsorten und Herkünfte wurde bestimmt sowie der Einfluss des Virusbefalls auf den Knollenertrag und -qualität ermittelt

Excited-State Dynamics of Organic Dyes at Liquid/Liquid Interfaces

Liquid/liquid interfaces play a crucial role in numerous areas of science. However, direct spectroscopic access to this thin (∼1 nm) region is not possible with conventional optical methods. After a brief review of the most used techniques to perform interfacial optical spectroscopy, we will focus on time-resolved surface second harmonic generation, which allows the measurement of the excited-state dynamics of probe molecules at interfaces. By comparing these dynamics with those measured in bulk solutions, precious information on the properties of the interfacial region can be obtained. To illustrate this, several studies performed in our group will be presented

Ultrafast Photoinduced Dynamics at Air/Liquid and Liquid/Liquid Interfaces

Although liquid/liquid and air/liquid interfaces are omnipresent, very little is known up to now about the dynamics of processes occurring at such interfaces. As a detailed understanding of these processes could be of invaluable technological, environmental, and medical importance, considerable effort has been invested over the last two decades in developing new interface-selective techniques that allow for gaining further insight into the dynamics of these processes. Whereas several major results have been achieved that helped to contribute to a deeper understanding, there are still many aspects concerning the properties of liquid interfaces that are not yet fully understood. In this Perspective, the work that has been carried out so far on photoinduced interfacial dynamics will be reviewed and the current challenges in this still emerging field of research discussed

Exploring template-bound dinuclear copper porphyrin nanorings by EPR spectroscopy

Electron paramagnetic resonance (EPR) spectroscopy has been used to study the molecular geometry as well as metal-ligand interactions in ten-membered porphyrin nanorings (c-P10Cu2) containing two copper and eight zinc centers. The presence of copper in the structures allows intramolecular interactions, including dipolar interactions between electron spins and hyperfine interactions to be quantified. Results obtained for c-P10Cu2 samples bound to two molecular templates with four or five binding sites, respectively, are compared to those obtained for a sample of the porphyrin ring in the absence of any templates. It is shown that the observed lower binding affinity of the nitrogen ligand to copper as compared to zinc has a strong impact on the geometries of the respective template-bound c-P10Cu2 structures. The interaction between the central copper atom and nitrogen ligands is weak, but pulsed EPR hyperfine techniques such as ENDOR and HYSCORE are very sensitive to this interaction. Upon binding of a nitrogen ligand to copper, the hyperfine couplings of the in-plane nitrogen atoms of the porphyrin core are reduced by about 3 MHz. In addition, the copper hyperfine couplings as well as the g-factors are altered, as detected by continuous wave EPR. DFT calculations of the hyperfine coupling tensors support the assignment of the measured couplings to the nuclei within the structure and reproduce the experimentally observed trends. Finally, Double Electron Electron Resonance (DEER) is used to measure the distances between the copper centers in a range between 2.5 and 5 nm, revealing the preferred geometries of the template-bound nanorings

Effects of Zinc and Lipid Alimentation on Delta3,Delta2-Enoyl-CoA Isomerase and Selected Aspects of Lipid Metabolism in Growing Rats

Die meisten Veränderungen, von denen der Lipidstoffwechsel im Zinkmangel betroffen ist, werden auch vom Fettsäuremuster der Nahrungsfette beeinflusst. Ziel dieser Arbeit war es, den Einfluss einer marginalen Zinkversorgung auf die Delta3,Delta2-Enoyl-CoA-Isomerase (ECI) als essentielles Enzym der beta-Oxidation ungesättigter Fettsäuren in Abhängigkeit vom Sättigungsgrad alimentärer Fettsäuren (FS) am Modelltier Ratte zu untersuchen. Gleichzeitig sollten zinkmangelbedingte Veränderungen im hepatischen FS-Muster und an charakteristischen Parametern des Lipidstoffwechsels bestimmt werden. Fünf Gruppen junger männlicher Wistar-Ratten wurden 4 Wochen lang entweder mit einer zinkarmen (7 mg Zn/kg) oder zinkadäquaten (50 mg Zn/kg) Diät ernährt, die 22 % Kakaobutter (gesättigte FS, GFS-Diät) oder 22 % Distelöl (ungesättigte FS, UFS-Diät) plus jeweils 3 % Sojaöl enthielt. Die marginal zinkversorgten Gruppen 7Zn-GFS und 7Zn-UFS wurden ad libitum, die adäquat zinkversorgten Gruppen 50Zn-GFS und 50Zn-UFS entsprechend restriktiv ernährt (pair feeding). Zusätzlich wurde eine ad libitum-Kontrollgruppe (50Zn-UFS ad libitum) mitgeführt. Beide 7Zn-Gruppen wiesen zu Versuchsende einen signifikant verminderten Zinkstatus auf. Im Vergleich zur 7Zn-GFS-Gruppe zeigte sich bei der 7Zn-UFS-Gruppe eine stärker reduzierte Futteraufnahme, eine geringere Lebendmasse sowie stärker reduzierte Zinkkonzentrationen in Plasma und Femur der Tiere. Die Aktivität der ECI wurde in mitochondrienreichen Fraktionen von Leber, Niere, Testis, Herz, Skelettmuskulatur und Fettgewebe mit trans-3-Hexenoyl-CoA bestimmt und zusätzlich auf die Aktivität der Succinatdehydrogenase (SDH) als mitochondrialen Marker bezogen. Die Aktivität der ECI der Leber war in den GFS-Gruppen niedriger als in den UFS-Gruppen (7Zn-GFS: 2,4 U/mg, 50Zn-GFS: 2,8 U/mg, 7Zn-UFS: 5,9 U/mg, 50Zn-UFS: 8,2 U/mg, 50Zn-UFS ad libitum: 8,0 U/mg Protein). Das ECI/SDH-Verhältnis war bei marginaler Zinkzufuhr der UFS-Tiere um 38 % niedriger als bei adäquater Zinkversorgung. Bezüglich der Höhe der mRNA-Expression der ECI in der Leber wurden keine Gruppenunterschiede beobachtet. In allen übrigen untersuchten Geweben wurde die Aktivität der ECI weder von der Zinkversorgung noch den alimentären FS beeinflusst. Die PPARalpha-Expression in der Leber war in beiden pair fed-Gruppen um mehr als den Faktor 2 höher als in den ad libitum-Gruppen und unabhängig von der alimentären Fettquelle. Die GFS-Gruppen wiesen im Plasma höhere Cholesterin- und Triglyceridkonzentrationen und in der Leber niedrigere Gesamtfettgehalte, niedrigere Cholesterin- und Triglycerid- sowie höhere Phospholipid-Konzentrationen auf. Unterschiede zwischen den 7Zn- und 50Zn-Gruppen stellten in der Mehrzahl Effekte der restriktiven Fütterung dar. Erwartungsgemäß reflektierte das FS-Muster der Leberlipide deutlich das Muster der alimentären FS. Zwischen den Gruppen 7Zn-UFS und 50Zn-UFS fanden sich Unterschiede nur im Gehalt an C 20:1n-9, C 20:2n-6 und C 20:3n-6 der Gesamtlipide und Phospholipide. Das Linolsäure/Arachidonsäure-Verhältnis war bei keiner der 7Zn-Gruppen gegenüber der pair fed-Gruppe erhöht und gab daher keinen Hinweis auf eine verminderte Desaturaseaktivität. Die Ergebnisse zeigen, dass die hepatische Delta3,Delta2-Enoyl-CoA-Isomerase, deren Aktivität in der Leber einer Regulation durch alimentäre FS unterliegt, bereits bei einer marginalen Zinkversorgung eine verminderte Aktivität aufweist. Dieser Aktivitätsverlust könnte einen geringeren Abbau ungesättigter FS im Zinkmangel signalisieren. Am FS-Muster der Leber, welches deutlich durch die Nahrungsfette beeinflusst wurde, ließ sich hingegen keine beeinträchtigte Degradation ungesättigter FS im marginalen Zinkmangel erkennen.Most alterations of lipid metabolism observed in zinc deficiency are also influenced by the fatty acid profile of the diet. The aim of this study was to determine the effect of marginal zinc deficiency on delta3,delta2-enoyl-CoA isomerase (ECI), a key enzyme of unsaturated fatty acid beta-oxidation, in response to dietary fats either rich in saturated or in unsaturated fatty acids in growing rats. Changes in liver fatty acid profile and in characteristic parameters of lipid metabolism were also examined. Five groups of young male Wistar rats were fed either low-zinc (7 mg Zn/kg) or zinc-adequate (50 mg Zn/kg) diets containing 22 % cocoa butter (saturated fatty acids, GFS diet) or 22 % safflower oil (unsaturated fatty acids, UFS diet), each supplemented with 3 % soy bean oil for four weeks. The 7Zn-GFS and 7Zn-UFS diets were offered ad libitum, whereas intake of the 50Zn-GFS and 50Zn-UFS diets was restricted through pair feeding. Additionally, an ad libitum-fed control group was included (50Zn-UFS ad libitum). At the end of the trial both 7Zn groups displayed a significantly impaired zinc status. Compared to the 7Zn-GFS group, the animals of the 7Zn-UFS group had a lower food intake, lower live weights and lower zinc concentrations in plasma and femur. The ECI activity was assayed in mitochondrial fractions of liver, kidney, testis, heart, skeletal muscle and adipose tissue with trans-3-hexenoyl-CoA and was additionally related to succinate dehydrogenase (SDH) activity as a mitochondrial marker. The mean ECI activity in the liver of the GFS groups was lower than that in the UFS groups (7Zn-GFS: 2.4 U/mg, 50Zn-GFS: 2.8 U/mg, 7Zn-UFS: 5.9 U/mg, 50Zn-UFS: 8.2 U/mg, 50Zn-UFS ad libitum: 8.0 U/mg protein). The marginal zinc supply to the UFS-fed animals reduced the ECI/SDH ratio by 38 %. No group differences were found in the mRNA expression level of ECI in the liver. In the other tissues examined, the ECI activity was affected neither by the zinc supply nor by the alimentary fatty acids. mRNA expression of PPARalpha in the liver of both pair-fed groups was more than twofold higher than in the ad libitum-fed groups, but was not influenced by the dietary fat. The GFS groups showed higher cholesterol and triglyceride concentrations in plasma as well as lower total lipids, lower cholesterol, lower triglyceride and higher phospholipid concentrations in the liver. Differences observed between 7Zn and 50Zn zinc-supplied animals were mainly attributable to the effects of restrictive feeding. As expected, the fatty acid composition of the liver lipids essentially reflected the fatty acid profile of the dietary fats. Differences between the 7Zn-UFS and 50Zn-UFS groups were detected only in the case of C 20:1n-9, C 20:2n-6 and C 20:3n-6 in total lipids and phospholipids. In both 7Zn-groups the linoleic acid/arachidonic acid ratio was not increased and did not point towards a diminished desaturase activity, compared to their pair-fed controls. These results suggest that the hepatic delta3,delta2-enoyl-CoA isomerase activity, which is controlled by alimentary fatty acids in the liver, is impaired in marginal zinc deficiency. This loss of activity might indicate a reduced degradation of unsaturated fatty acids in zinc deficiency. Yet the fatty acid profile of the liver, mainly influenced by the dietary fat, did not show changes indicating a diminished degradation of unsaturated fatty acids in marginal zinc deficiency