Production of γ-Decalactone by a Psychrophilic and a Mesophilic Strain of the Yeast <Emphasis Type="Italic">Rhodotorula aurantiaca</Emphasis>

Among 18 psychrophilic strains isolated near the Antarctic Station, the psychrophilic strain Rhodotorula aurantiaca A19 was selected for its ability of growth and γ-decalactone production at low temperatures. The effects of temperature, initial pH, and castor oil concentration on the growth and γ-decalactone production by a psychrophilic and a mesophilic strain of R. aurantiaca were investigated. The highest γ-decalactone production in flasks (5.8 g/l) was obtained with the strain A19 at 14 °C and initial pH 7.0 in medium containing 20 g/l castor oil. On the other hand, these factors did not affect the production of γ-decalactone by the mesophilic strain. In fermentor, a γ-decalactone concentration of 6.6 g/l was reached with the strain A19, whereas a maximum of 0.1 g/l was obtained with the mesophilic strain. Our results suggest that the ability to synthesize γ-decalactone is a particularity of the strain A19, since the mesophilic strain (no. 30645) produced small amounts, and the other (no. 31354) did not exhibit this property. It is, to our knowledge, the first report of γ-decalactone production by R. aurantiaca and furthermore by a psychrophilic yeast strain. Moreover, the amount of γ-decalactone obtained in fermentor with the strain 19 was on the order of concentrations usually described in patents.     

Chiral recognition and resolution of the enantiomers of supramolecular triangular hosts: synthesis, circular dichroism, NMR, and X-ray molecular structure of [Li subset(R,R,R)-[CpRh(5-chloro-2,3-dioxopyridine)]3][Delta-Trisphat

The racemic triangular supramolecular host [CpRh(5-chloro-2,3-dioxopyridine)](3) (1) was prepared in high yield. Treatment with LiCl followed by addition of silver salt AgOTf gave the triflate salt species [Li subset[CpRh(5-chloro-2,3-dioxopyridine)](3)][OTf] (2). Subsequent anion metathesis using the optically pure chiral shift reagent [Cinchonidinium][Delta-Trisphat] produced a pair of diastereomers [Li subset(R,R,R)-[CpRh(5-chloro-2,3-dioxopyridine)](3)][Delta-Trisphat] (3a) and [Li subset(S,S,S)-[CpRh(5-chloro-2,3-dioxopyridine)](3)][Delta-Trisphat] (3b). The resolution of these diastereomers was achieved by fractional crystallization, and their stereochemistry relationship was established by circular dichroism studies. The X-ray molecular structure of 3a is reported and shows as an outstanding feature a chiral recognition between the Delta-Trisphat anion and a single enantiomer cation [Li subset(R,R,R)-[CpRh(5-chloro-2,3-dioxopyridine)](3)](+) manifested through a pi-pi interaction. (1)H NMR and circular dichroism studies in solution support the solid-state behavior.     

Positive Solutions of Nonlinear Elliptic Equations in Unbounded Domains in R 2

We study the existence of positive solutions of the nonlinear equation u+f(,u)=0, in D with u=0 on D, where D is an unbounded domain in R ² with a compact nonempty boundary D consisting of finitely many Jordan curves. The aim is to prove an existence result for the above equation in a general setting by using potential theory.     

Synthesis of new indole derivatives structurally related to donepezil and their biological evaluation as acetylcholinesterase inhibitors

New series of indole derivatives analogous to donepezil, a well known anti-Alzheimer and acetylcholinesterase inhibitor drug, was synthesized. A full chemical characterization of the new compounds is provided. Biological evaluation of the new compounds as acetylcholinesterase inhibitors was performed. Most of the compounds were found to have potent acetylcholinesterase inhibitor activity compared to donepezil as standard. The compound 1-(2-(4-(2-fluorobenzyl) piperazin-1-yl)acetyl)indoline-2,3-dione (IIId) was found to be the most potent.     

Spectroscopic characterizations on the N,N′-bis-alkyl derivatives of 1,4,6,8-naphthalenediimide charge-transfer complexes

Charge-transfer (CT) complexes formed from the reactions of two N,N′-bis-alkyl derivatives of 1,4,6,8-naphthalenediimide such as N,N′-bis-[2-hydroxyethyl]-1,4,6,8-naphthalenediimide (BHENDI) and N,N′-bis-[2-N,N-dimethylaminoethyl]-1,4,6,8-naphthalenediimide (BDMAE NDI) with DDQ, CHL, TCNQ, DCQ and DBQ as π-acceptors have been studied spectrophotometrically in chloroform and/or methanol at 25 °C. The photometric titration curves for the reactions indicated that the data obtained refer to 1:1 charge-transfer complexes of [(BHENDI)(DDQ)], [(BDMAENDI)(DDQ)], [(BHENDI)(CHL)], [(BDMAENDI)(CHL)], [(BHENDI)(TCNQ)], [(BDMAENDI)(TCNQ)], [(BHENDI)(DCQ)], [(BDMAENDI)(DCQ)], [(BHENDI)(DBQ)] and [(BDMAENDI)(DBQ)] were formed. Benesi–Hildebrand and its modification methods were applied to the determination of association constant (K), molar extinction coefficient (?). The solid CT complexes have been synthesized and characterization by different spectral methods.     

Proton-proton elastic scattering via the Trojan horse method

We address a successful indirect technique, the Trojan horse method, which allows one to measure the bare nucleus cross section for rearrangement reactions down to astrophysical energies. In particular, we consider here the application of the method to the p-p elastic scattering. This represents an important test of the main feature of the method, namely the suppression of Coulomb effects in the entrance channel due to off-energy-shell effects. In contrast to the on-energy-shell case, the extracted p-p cross section does not exhibit the Coulomb-nuclear interference minimum, as predicted by the half-off-energy shell calculations. This hypothesis is strengthened by the agreement between the Trojan horse p-p data and the calculated on-energy-shell n-n, n-p and nuclear p-p cross sections.     

On the magnitude of the Li + He → B + n reaction cross section at the Big-Bang temperature

The ⁸Li + ⁴He → ¹¹B + n reaction at Ecm<2 MeV$E_{\mathrm{cm}}<2\text{MeV}$ is a process of relevant astrophysical interest for which a remarkable experimental discrepancy between inclusive and exclusive cross-section measurements exists. In this Letter, a new inclusive neutron measurement at Ecm=1.05±0.16 MeV$E_{\mathrm{cm}}=1.05\pm 0.16\text{MeV}$ is given. The radioactive ⁸Li beam was delivered by the EXCYT facility. The cross section was determined by a low-background measurement of the time correlation between the ⁸Li projectile arrival to the target and the following neutron capture in a threshold-less 4π thermalization counter. This new data strengthens the reliability of the previous inclusive reaction cross-section data and altogether are consistent with a significant population of ¹¹B levels at high excitation energy.