A Montana soil actinomycete,
Streptomyces anulatus, produced (1×10
−2% yield) a new cancer cell growth inhibitory cyclooctadepsipeptide named montanastatin (
1) accompanied by the potent anticancer ...antibiotic valinomycin (
2) in very high (5.1%) yields. Valinomycin but not montanastatin inhibited growth of a number of pathogenic bacteria and fungi. Interpretation of high-field (500
MHz) NMR and high-resolution FAB mass spectral data allowed assignment of the structure
cyclo-(
d-Val-
l-Lac-
l-Val-
d-Hiv) to montanastatin. Valinomycin (
2) was also isolated from actinomycetes cultured from a tree branch and animal feces collected in Malaysia.
Streptomyces exfoliatus, isolated from the tree branch, was found to contain valinomycin in 1.6% yield, while the fecal isolate,
S. anulatus, gave valinomycin in 0.9% yield.
Context. In 2009, the Sun and the Earth passed through the equatorial plane of Jupiter and therefore the orbital planes of its main satellites. It was the equinox on Jupiter. This occurrence made ...mutual occultations and eclipses between the satellites possible. Experience has shown that the observations of such events provide accurate astrometric data able to bring new information on the dynamics of the Galilean satellites. Observations are made under the form of photometric measurements, but need to be made through the organization of a worldwide observation campaign maximizing the number and the quality of the data obtained. Aims. This work focuses on processing the complete database of photometric observations of the mutual occultations and eclipses of the Galilean satellites of Jupiter made during the international campaign in 2009. The final goal is to derive new accurate astrometric data. Methods. We used an accurate photometric model of mutual events adequate with the accuracy of the observation. Our original method was applied to derive astrometric data from photometric observations of mutual occultations and eclipses of the Galilean satellites of Jupiter. Results. We processed the 457 lightcurves obtained during the international campaign of photometric observations of the Galilean satellites of Jupiter in 2009. Compared with the theory, for successful observations, the r.m.s. of O–C residuals are equal to 45.8 mas and 81.1 mas in right ascension and declination, respectively; the mean O–C residuals are equal to –2 mas and –9 mas in right ascension and declination, respectively, for mutual occultations; and –6 mas and +1 mas in right ascension and declination, respectively, for mutual eclipses.
Novel Cytotoxic Diterpenes from Casearia arborea Beutler, John A; McCall, Kate L; Herbert, Kathryn ...
Journal of natural products (Washington, D.C.),
05/2000, Letnik:
63, Številka:
5
Journal Article
Recenzirano
Cytotoxicity-guided fractionation of the dichloromethane−methanol extract of the roots of Casearia arborea yielded five novel clerodane diterpenes, casearborins A−E (1−5), as well as cucurbitacin B. ...The presence of cucurbitacins glycosides was also detected. The absolute configuration of casearborin E was determined by X-ray crystallography.
The wide ranging marine sponge
Hyrtios erecta is the source of the spongistatins, a new class of macrocyclic lactone antineoplastic agents. Continuation of a detailed investigation of cancer cell ...growth inhibitory (P388 lymphocytic leukemia) fractions (trace) from
H. erecta has revealed the presence (10
−5 to 10
−7% yield) of cytotoxic pentacyclic sesterterpenes. Employing P388 leukemia and human tumor cell line-guided bioassay techniques, two new moderate inhibitors of cancer cells were isolated and named sesterstatins
4 (
1a, P388 ED
50 4.9 μg/mL) and 5 (
1b, DU-145 prostate
GI
50 1.9 μg/mL). Similar to other sesterterpenes, sesterstatin 5 inhibited growth of a Gram-positive bacterium. High field (500 MHz) 2-D NMR techniques were primarily employed for initial structural assignments, and structural assignments were confirmed by X-ray crystal structure determination of sesterstatin 4 (
1a) and 5 (
1b).
We use data from five stellar occultations observed between 2013 and 2016 to constrain Chariklo's size and shape, and the ring reflectivity. We consider four possible models for Chariklo (sphere, ...Maclaurin spheroid, triaxial ellipsoid, and Jacobi ellipsoid), and we use a Bayesian approach to estimate the corresponding parameters. The spherical model has a radius R = 129 3 km. The Maclaurin model has equatorial and polar radii and , respectively, with density . The ellipsoidal model has semiaxes , , and . Finally, the Jacobi model has semiaxes a = 157 4 km, b = 139 4 km, and c = 86 1 km, and density . Depending on the model, we obtain topographic features of 6-11 km, typical of Saturn icy satellites with similar size and density. We constrain Chariklo's geometric albedo between 3.1% (sphere) and 4.9% (ellipsoid), while the ring I/F reflectivity is less constrained between 0.6% (Jacobi) and 8.9% (sphere). The ellipsoid model explains both the optical light curve and the long-term photometry variation of the system, giving a plausible value for the geometric albedo of the ring particles of 10%-15%. The derived mass of Chariklo of 6-8 × 1018 kg places the rings close to 3:1 resonance between the ring mean motion and Chariklo's rotation period.
Amateur contributions to professional publications have increased exponentially over the last decades in the field of planetary astronomy. Here we review the different domains of the field in which ...collaborations between professional and amateur astronomers are effective and regularly lead to scientific publications.We discuss the instruments, detectors, software and methodologies typically used by amateur astronomers to collect the scientific data in the different domains of interest. Amateur contributions to the monitoring of planets and interplanetary matter, characterization of asteroids and comets, as well as the determination of the physical properties of Kuiper Belt Objects and exoplanets are discussed.
The (E)-stilbene isomer (2a) of the (Z)-combretastatin A-4 prodrug (1b) was efficiently prepared from (E)-combretastatin A-4 by a reaction sequence employing phosphorylation (dibenzyl ...chlorophosphite), cleavage (trimethyliodosilane) of the benzyl ester and reaction of the resulting phosphoric acid with sodium methoxide. The sodium phosphate product (2c) was also found to be an important side-product, presumably from iodine-catalyzed isomerization, when the analogous synthetic route was used to obtain the combretastatin A-4 prodrug (1b). The phosphoric acid precursor of prodrug 1b derived from (Z)-combretastatin A-4 (1a) was converted into a series of metal cation and ammonium cation salts to evaluate effects on human cancer cell growth, antimicrobial activities and solubility behavior.
A new cell growth inhibitory (P-388 murine leukemia ED50 7.5 micrograms/ml) cycloheptapeptide designated phakellistatin 1 was isolated from two Indo-Pacific sponges, Phakellia costata and Stylotella ...aurantium. Structural elucidation was accomplished utilizing high field nmr, amino acid analyses, and mass spectral techniques (fab, tandem ms/ms), followed by chiral gas chromatographic procedures for absolute configuration assignments (all S-amino acid units). By these methods phakellistatin 1 1 was found to be cyclo (Pro-Ile-Pro-Ile-Phe-Pro-Tyr), and this assignment was finally confirmed by an X-ray crystal structure determination.
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