E- and Z-Proxamidines,Unprecedented 1,3-Diazacyclooct-1-ene Alkaloids from Fruiting Bodies of Laccaria proxima

Fruiting bodies of Laccaria proxima were screened for the presence of new secondary metabolites by means of HPLC-UV and LC-HR-(+)-ESIMS. Thus, two isomeric alkaloids with a highly unusual core structure, E-proxamidine and its Z-isomer, were isolated from Laccaria proxima. The proxamidines consist of an eight-membered heterocyclic ring system with a formamidine unit. The structures were established by 2D NMR spectroscopic methods, HR-(+)-ESIMS, and HR-(+)-ESIMS/MS. The proxamidines are probably biosynthetically derived from tryptophan, dimethylallyl pyrophosphate, and S-adenosylmethionine and the eight-membered ring of the proxamidines is likely to be generated by a rearrangement of the tryptophan sceleton. Metabolic profiling of fruiting bodies of some other Laccaria species revealed that the proxamidines appear in significant amounts only in L. proxima making the compounds suitable as chemotaxonomic markers. E-Proxamidine exhibits herbicidal activity against Lepidium sativum.     

Excited states of bound excitons in ZnO

The bound exciton lines I₅, I₆, and I_{$\text{7}\text{8}$} in ZnO at 5 K are studied in the energetic region of the free excitons and below by means of excitation spectroscopy. Apart from the maxima at the free exciton energies, additional resonances are observed and interpreted as the direct creation of bound excitons in excited states which lie 6meV and 4.5 meV above the ground states.     

Aminotenuazonic Acid: Isolation,Structure Elucidation,Total Synthesis and Herbicidal Activity of a New Tetramic Acid from Fruiting Bodies of Laccaria Species

(5S,6S)-Aminotenuazonic acid, a new 3-acyltetramic acid, related to the well-known mycotoxin tenuazonic acid has been isolated from fruiting bodies of Laccaria bicolor. Its structure was mostly established by analysis of its 2D NMR and HR-(+)-ESI-MS spectra. A total synthesis starting from N-Boc-l -isoleucine gave (5S,6S)-aminotenuazonic acid in 8 % yield over nine steps (67 % de). The key steps of the total synthesis are a light-initiated Hofmann–Löffler–Freytag radical chain reaction and a Dieckmann cyclisation. The relative and absolute configurations of the natural product were determined by comparison of its NMR and CD spectra with those of the corresponding enantiopure synthetic compounds. Metabolic profiling of crude extracts of different mushrooms showed that aminotenuazonic acid is present in all four of the investigated Laccaria species. Aminotenuazonic acid shows phytotoxic activities against the root and shoot growth of Lepidium sativum, Pinus sylvestris and Arabidopsis thaliana comparable to those of tenuazonic acid.     

The thermal decomposition of aqueous manganese (II) nitrate solution

The thermal decomposition of commercially available aqueous solutions of manganese(II) nitrate was investigated using the conventional thermal analytical techniques of thermogravimetry (TG), differential thermal analysis (DTA), and evolved gas analysis (EGA). Infrared spectra and X-ray diffraction patterns were used to help characterize intermediate species.     

Luminescence-assisted two-photon spectroscopy (LATS) - a new spectroscopic method applied to biexciton levels in highly excited CdS and ZnO

We present a new “economic” method for performing two-photon spectroscopy using just one exciting dye-laser and taking advantage of the hereby produced broad emission bands of highly excited semiconductors. It is applied to the biexciton ground state in CdS (E_biex = 5.0983 eV, symmetry Γ₁) and to an excited biexciton state in ZnO (6.7407 eV, symmetry Γ₅).     

Zur Bestimmung des Leistungsverhaltens bei mehrreihigen,luft- bzw. gasgekühlten Kondensatoren mit Inerten

Zusammenfassung Bei mehrreihigen, luft- oder gasgekühlten Kondensatoren besteht die Gefahr einer Totzonenbildung durch Ansammlung von Inerten. Bei Kondensatoren, die mit Überschußdampf arbeiten, besteht ebenso die Gefahr einer Totzonenbildung. Es werden einfache analytische Gleichungen angegeben, mit denen sich die Abhängigkeit von Überschußdampfmenge und Totzonengröße bestimmen läßt. Die vorgestellte Lösung gestattet ebenso die Berechnung der zweidimensionalen Geschwindigkeitsund Temperaturverteilung des Kondensators.

---

Performance of single-pass aircooled or gascooled condensers with inerts

In single-pass gascooled condensers the accumulation of noncondensables within the tubes may cause the formation of a dead zone. This may also happen in condensers that are operating with excess vapour. Simple arithmetic expressions are developed to describe the dependency of excess vapour and size of the dead zone. More over, the solution enables the calculation of the twodimensional temperature and vapour flow distribution within the condenser.

---

Nomenklatur A ₁ Rohrquerschnitt - B Hilfsgröße (Gl. 6) - C Druckverlustkoeffizient - d _h hydraul. Durchmesser - E Row Effectiveness - F Wärmeübergangsfläche - k Wärmedurchgangskoeffizient - l aktive Rohrlänge - L Gesamt-Rohrlänge - M Dampfmengenstrom - n ₁ Zahl der Rohre der 1. Reihe - N Gesamt-Rohrreihenzahl - NTU kF/W _L - NTU ^* NTU bezogen auf 1 Reihe (NTU/N) - P dampfseitiger Druckverlust - Q Wärmeleistung - r Kondensationswärme - T Temperatur - u Dampfaustrittsgeschwindigkeit - v Dampfgeschwindigkeit - w Dampfeintrittsgeschwindigkeit - W Kapazitätsstrom - y Rohrlängenkoordinate - z Reihenkoordinate Griechische Symbole passiver Reihenanteil - Reibungsbeiwert - aktives Längenverhältnis - Grenzlängenverhältnis (L/l₀) - Temperaturabstand (Luftseite/Produktseite) - Dichte - Totzonenanteil - Grenzpunkt der Totzone Indizes 0 Stelle z=0 - a Bereicha - A Austritt - ab Abgleich - b Bereichb - E Eintritt - K Kondensat - L Luft-, Kühlgasseite - v Dampfseite - 1 Bereich 1 - 2 Bereich 2     

Electrophysiological response of cultured trabecular meshwork cells to synthetic ion channels

The response of living cells of the trabecular meshwork to synthetic ion channels is described. The THF-gramicidin hybrids THF-gram and THF-gram-TBDPS as well as a linked gA-TBDPS and gramicidin A were applied to cultured ocular trabecular meshwork cells. THF-gram application (minimal concentration, 10(-8) M; saturation, 10(-7) M) led to an additional conductance which displayed characteristics of weak Eisenman-I-selective cation channels, no cell destruction, an asymmetric change of the inward/outward currents, and higher current densities using Cs(+) as charge carrier compared to Na(+) and K(+). Linked-gA-TBDPS showed at 10(-12) M increases of the membrane conductance comparable to gA at 10(-7) M and a much faster response of the cells. Thus, THF-gramicidin hybrids form a basis for the use of synthetic ion channels in biological systems, which eventually may lead to new therapeutic approaches.     

Macrooxazoles A–D,New 2,5-Disubstituted Oxazole-4-Carboxylic Acid Derivatives from the Plant Pathogenic Fungus Phoma macrostoma

In our ongoing search for new bioactive fungal metabolites, four previously undescribed oxazole carboxylic acid derivatives (1–4) for which we proposed the trivial names macrooxazoles A–D together with two known tetramic acids (5–6) were isolated from the plant pathogenic fungus Phoma macrostoma. Their structures were elucidated based on high-resolution mass spectrometry (HR-MS) and nuclear magnetic resonance (NMR) spectroscopy. The hitherto unclear structure of macrocidin Z (6) was also confirmed by its first total synthesis. The isolated compounds were evaluated for their antimicrobial activities against a panel of bacteria and fungi. Cytotoxic and anti-biofilm activities of the isolates are also reported herein. The new compound 3 exhibited weak-to-moderate antimicrobial activity as well as the known macrocidins 5 and 6. Only the mixture of compounds 2 and 4 (ratio 1:2) showed weak cytotoxic activity against the tested cancer cell lines with an IC₅₀ of 23 µg/mL. Moreover, the new compounds 2 and 3, as well as the known compounds 5 and 6, interfered with the biofilm formation of Staphylococcus aureus, inhibiting 65%, 75%, 79%, and 76% of biofilm at 250 µg/mL, respectively. Compounds 5 and 6 also exhibited moderate activity against S. aureus preformed biofilm with the highest inhibition percentage of 75% and 73% at 250 µg/mL, respectively.