1,721,141 research outputs found
The deep-water Xestoleberidinae Sars, 1928 (Crustacea: Ostracoda) in the Pliocene - Early Pleistocene of the M. San Nicola Section (Gela, Sicily)
No full textThree species of the Xestoleberidinae Sars, 1928 have been found in the Plio-Pleistocene section of Monte S. Nicola (Sicily) which are x. pasta n. sp., X. prognata Bonaduce & Danielopol, 1988 and Platyleberis profunda (Breman, 1975). The ostracode assemblage of the section pertains without any doubt to the bathyal environment, a fact which confirms that the subfamily is not restricted to the shallow marine and brackish waters
Kunihirella, a new marine ostracod genus (Podocopa, Cytheruridae) from the Early Pliocene of Eraclea Minoa (Sicily)
No full textKunihirella n.g. (type-species K. eracleaensis n.sp.) of the Eraclea Minoa Trubi Formation (Southern Sicily, Italy) is erected from the Early Pliocene. A second species, previously attributed to Swainocythere Ishizaki, 1981, is considered to pertain to the proposed new genus
Accurate Mass Analysis of N-Acyl-Homoserine-Lactones and Cognate Lactone-Opened Compounds in Bacterial Isolates of Pseudomonas aeruginosa PA01 by LC-ESI-LTQ-FTMS
No full textN-acyl-homoserine-lactones (AHSLs) are widely conserved signal molecules present in quorum sensing systems of Gram-negative bacteria such as Pseudomonas aeruginosa. We present here the results obtained with a hybrid linear trap/Fourier transform ion cyclotron resonance (LTQ-FTICR) mass spectrometer used to investigate the occurrence of AHSLs and cognate N-acyl-homoserines (AHSs) in bacterial isolates of P. aeruginosa (strain PAO1). Two hydrolysed AHSs were found in significant amounts, most likely formed through the lactone opening of N-3-oxo-decanoyl-L-homoserine-lactone (3OC(10)-HSL) and N-3-oxo-dodecanoyl-L-homoserine-lactone (3OC(12)-HSL). Structure elucidation of these ring-opened molecules, i.e. N-3-oxo-decanoyl-L-homoserine (3OC(10)-HS), and N-3-oxo-dodecanoyl-L-homoserine (3OC(12)-HS), which are not detected by bacterial biosensors, was performed by high-resolution and accurate mass measurements upon liquid chromatography (LC) and confirmed by tandem MS in the LTQ analyser. Assignment of chemical formula, with mass spectra in the form of [M + H](+), was significantly expedited by extracted ion chromatograms (XICs) because the number of potentially plausible formulae for each protonated signalling molecule was considerably reduced a priori by the LC behaviour, the high mass measurement accuracy available in FTICR mass spectra and the isotopic patterns. At least two concentration levels were observed in spent culture supernatants of P. aeruginosa: compounds at a relatively high content (5-15 mu M) that is C(4)-HSL, 3OC(10)-HS, and 3OC(12)-HS and those occurring at a lower content (<0.2 mu m) that is C(6)-HSL and C(8)-HSL. The implications of this work extend to a great variety of Gram-negative bacteria
The deep-water Xestoleberidinae Sars, 1928 (Crustacea: Ostracoda) in the Pliocene - Early Pleistocene of the M. San Nicola Section (Gela, Sicily)
No full textThree species of the Xestoleberidinae Sars, 1928 have been found in the Plio-Pleistocene section of Monte S. Nicola (Sicily) which are x. pasta n. sp., X. prognata Bonaduce & Danielopol, 1988 and Platyleberis profunda (Breman, 1975). The ostracode assemblage of the section pertains without any doubt to the bathyal environment, a fact which confirms that the subfamily is not restricted to the shallow marine and brackish waters
Profiling of N-Acyl-Homoserine Lactones by Liquid Chromatography Coupled with Electrospray Ionization and a Hybrid Quadrupole Linear-Ion-Trap and Fourier-Transform Ion-Cyclotron-Resonance Mass Spectrometry (LC-ESI-LTQ-FTICR-MS)
No full textA method for the comprehensive profiling of the N-acyl-homoserine lactone (AHL) family of bacterial quorum-sensing molecules is presented using liquid chromatography (LC) coupled to a hybrid quadrupole linear ion trap (LTQ) and Fourier-transform ion-cyclotron-resonance mass spectrometer (FTICR). We demonstrate an increase in signal intensity in MS with electrospray ionization (ESI) of the protonated molecules, [M + H](+), by using acetonitrile (ACN) instead of methanol (MeOH) as the organic solvent under the conditions in which the samples were supplied to the probe by direct infusion at constant flow rates. The presence of ACN prevents the formation of methanol adducts such as [M + MeOH + H](+) and [M + MeOH + Na](+), while also lowering the signal intensity of sodiated [M + Na](+) ions. Sensitivity of these signaling molecules in terms of signal-to-noise ratio (S/N) using low-resolution LTQ-MS and high-resolution FTICR-MS were compared under reversed-phase (RP) LC separations with ESI interface. Special emphasis was paid to the choice of the separation column, its elution conditions and detection of the major AHL compounds produced by the Serratia liquefaciens strain ATCC 27592. The most promising results were obtained using a RP C16-amide column eluted with a linear mobile phase gradient ACN/H2O containing 0.1% formic acid. The whole set of AHL homologs in bacterial extracts was detected in the extracted-ion chromatographic (XIC) mode, and the calculations of molecular formulae were performed by including the isotopic pattern. This mode of displaying data, with a very narrow mass-to-charge ratio window (i.e. +/- 0.0010 as m/z unit) around each selected ion, has allowed the identification of all the eight known homoserine lactones, viz. C-4-HSL, 3-oxo-C-6-HSL, C-6-HSL, 3-oxo-C-8-HSL, C-8-HSL, C-10-HSL, C-12-HSL and C-14-HSL. In addition, at least four uncommon signaling mediators previously unreported, namely, 3-oxo-C-10:1-HSL, 3-oxo-C-11:2-HSL, 3-oxo-C-13:2-HSL and 3-OH-C-16-HSL, were identified and characterized; their roles in cell-to-cell communication has to be elucidated
Kunihirella, a new marine ostracod genus (Podocopa, Cytheruridae) from the Early Pliocene of Eraclea Minoa (Sicily)
Full text linkKunihirella n.g. (type-species K. eracleaensis n.sp.) of the Eraclea Minoa Trubi Formation (Southern Sicily, Italy) is erected from the Early Pliocene. A second species, previously attributed to Swainocythere Ishizaki, 1981, is considered to pertain to the proposed new genus
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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