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151.
Francesc Lloret Miguel Julve Joan Cano Rafael Ruiz-García Emilio Pardo 《Inorganica chimica acta》2008,361(12-13):3432-3445
In this contribution we study and analyse the influence of the different parameters involved in the magnetic susceptibility of six-coordinated high-spin Co(II) complexes. We propose an empirical expression to fit the magnetic susceptibility of polycrystalline samples of mononuclear Co(II) complexes with an axial distortion, the variable parameters being Δ (axial distortion), α (orbital reduction factor) and λ (spin–orbit coupling). This expression avoids solving the 12 × 12 matrix associated to the distortion of the 4T1g term. In order to take into account the magnetic coupling (J) in the polynuclear Co(II) complexes, a perturbational approach is proposed to describe their magnetic susceptibility in the whole temperature range (2–300 K) as a function of J, Δ, α and λ. This approach is valid in the limit of the weak magnetic coupling as compared to the spin–orbit coupling, |J/λ| < 0.1. The model allows the treatment of each cobalt(II) ion in axial symmetry as an effective spin Seff = 1/2. That causes a drastic reduction of the matrix size of the polynuclear compounds from 12n × 12n to 2n × 2n, n being the number of Co(II) ions in the complex. The main advantage of the model is to make possible the fit of the magnetic susceptibility data of those polynuclear Co(II) complexes whose high nuclearity involved intractable matrices. 相似文献
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153.
Maria João Fernandes Martins Francesc Mezquita Olivier Schmit Juan Rueda Giampaolo Rossetti Tadeusz Namiotko 《Hydrobiologia》2009,636(1):219-232
Eucypris virens is a freshwater ostracod in which both sexual reproduction and parthenogenesis occur. Sympatric coexistence of both reproductive
modes is known in zones of overlap. This renders the species a potentially valuable model organism to study the ‘queen of
evolutionary problems’, i.e. why sex is so successful despite its costs (paradox of sex). In order to maximally exploit this
potential, a broad knowledge of the species’ ecology is essential, including an understanding of its life history and population
dynamics. Here, the phenology of the species was followed in three temporary ponds through monthly (Spain) or fortnightly
(Poland) samplings, throughout an inundation period. This study confirms the wide ecological tolerances of E. virens. Although the species is generally assumed to be univoltine, two hatching periods were observed in the Spanish sites. Biotic
interactions, especially predation, appear to be the important determinants of population dynamics in long-hydroperiod sites.
Abiotic conditions may influence population dynamics through their impact on egg hatching. In the site with male presence,
the initially female-biased sex ratio evolved towards a balanced sex ratio through the season. No consistent differences in
limb morphology were observed between females originating from the three study sites. On the other hand, valve size of adult
females varied among sites, possibly influenced by local environmental conditions (mainly salinity and pH) as well as the
expected genetic diversity. 相似文献
154.
The mixed-ligand complexes of manganese(II) of formula [Mn(pyim)2(C5O5)] (1) and [Mn(pyim)(H2O)(C5O5)]n · 2.5nH2O (2) [pyim = 2-(2-pyridyl)imidazole and = croconate (dianion of 4,5-dihydroxy-4-cyclopentene-1,2,3-trione)] have been prepared and their structures determined by X-ray crystallographic methods. Compound 1 is a tris-chelated mononuclear complex where the manganese atom is six-coordinate: four nitrogen atoms from two pyim molecules and two oxygen atoms from a croconate group build a somewhat distorted octahedral surrounding around the metal atom. The resulting neutral mononuclear units are linked to each other through double bridges which are constituted by the imidazole N-H and the metal-coordinated croconate-oxygen atom, the metal-metal separation through this supramolecular pathway being 7.6856(11) Å. Compound 2 is a croconato-bridged manganese(II) uniform chain with an intrachain metal-metal distance of 7.5118(9) Å. A bidentate pyim group, a water molecule and four oxygen atoms from two bis-bidentate croconate ligands build an irregular seven-coordination polyhedron around each manganese atom in 2. The investigation of the magnetic properties of 2 in the temperature range 1.9-295 K has shown the occurrence of a weak antiferromagnetic interaction [J = −0.066 cm−1 with the Hamiltonian defined as H = −J ∑i Si · Si+1] through the bis-bidentate croconate. The ability of the bis-chelating croconate to mediante magnetic interactions between paramagnetic first-row transition metal ions is discussed and compared to that of the related oxalate ligand. 相似文献
155.
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157.
Mercedes Ingelmo-Torres Elena González-Moreno Adam Kassan Michael Hanzal-Bayer Francesc Tebar Albert Herms Thomas Grewal John F. Hancock Carlos Enrich Marta Bosch Steven P. Gross Robert G. Parton Albert Pol 《Traffic (Copenhagen, Denmark)》2009,10(12):1785-1801
In recent years, progress in the study of the lateral organization of the plasma membrane has led to the proposal that mammalian cells use two different organelles to store lipids: intracellular lipid droplets (LDs) and plasma membrane caveolae. Experimental evidence suggests that caveolin (CAV) may act as a sensitive lipid-organizing molecule that physically connects these two lipid-storing organelles. Here, we determine the sequences necessary for efficient sorting of CAV to LDs. We show that targeting is a process cooperatively mediated by two motifs. CAV's central hydrophobic domain (Hyd) anchors CAV to the endoplasmic reticulum (ER). Next, positively charged sequences (Pos-Seqs) mediate sorting of CAVs into LDs. Our findings were confirmed by identifying an equivalent, non-conserved but functionally interchangeable Pos-Seq in ALDI, a bona fide LD-resident protein. Using this information, we were able to retarget a cytosolic protein and convert it to an LD-resident protein. Further studies suggest three requirements for targeting via this mechanism: the positive charge of the Pos-Seq, physical proximity between Pos-Seq and Hyd and a precise spatial orientation between both motifs. The study uncovers remarkable similarities with the signals that target proteins to the membrane of mitochondria and peroxisomes 相似文献
158.
Pablo Mobili María de los Ángeles Serradell Sebastián A. Trejo Francesc X. Avilés Puigvert Analía G. Abraham Graciela L. De Antoni 《Antonie van Leeuwenhoek》2009,95(4):363-372
Since the presence of S-layer protein conditioned the autoaggregation capacity of some strains of Lactobacillus kefir, S-layer proteins from aggregating and non-aggregating L. kefir strains were characterized by immunochemical reactivity, MALDI-TOF spectrometry and glycosylation analysis. Two anti-S-layer
monoclonal antibodies (Mab5F8 and Mab1F8) were produced; in an indirect enzyme-linked immunosorbent assay Mab1F8 recognized
S-layer proteins from all L. kefir tested while Mab5F8 recognized only S-layer proteins from aggregating strains. Periodic Acid-Schiff staining of proteins
after polyacrylamide gel electrophoresis under denaturing conditions revealed that all L. kefir S-layer proteins tested were glycosylated. Growth of bacteria in the presence of the N-glycosylation inhibitor tunicamycin
suggested the presence of glycosydic chains O-linked to the protein backbone. MALDI-TOF peptide map fingerprint for S-layer
proteins from 12 L. kefir strains showed very similar patterns for the aggregating strains, different from those for the non-aggregating ones. No positive
match with other protein spectra in MSDB Database was found. Our results revealed a high heterogeneity among S-layer proteins
from different L. kefir strains but also suggested a correlation between the structure of these S-layer glycoproteins and the aggregation properties
of whole bacterial cells. 相似文献
159.
A novel differential in gel electrophoresis (DIGE)-based method has been developed and applied to measure telomere length and appearance of two-dimensional structural DNA changes. It can be applied to any area requiring quick and evident measurement of structural DNA changes. 相似文献
160.
Rosanna Pescini Gobert Monique van den Eijnden Cedric Szyndralewiez Catherine Jorand-Lebrun Dominique Swinnen Linfeng Chen Corine Gillieron Fiona Pixley Pierre Juillard Patrick Gerber Caroline Johnson-L��ger Serge Halazy Montserrat Camps Agnes Bombrun Margaret Shipp Pierre-Alain Vitte Vittoria Ardissone Chiara Ferrandi Dominique Perrin Christian Rommel Rob Hooft van Huijsduijnen 《The Journal of biological chemistry》2009,284(17):11385-11395