Identification of H ferritin-dependent and independent genes in K562 differentiating cells by targeted gene silencing and expression profiling

Ferritin is best known as the key molecule in intracellular iron storage, and is involved in several metabolic processes such as cell proliferation, differentiation and neoplastic transformation. We have recently demonstrated that the shRNA silencing of the ferritin heavy subunit (FHC) in a melanoma cell line is accompanied by a consistent modification of gene expression pattern leading to a reduced potential in terms of proliferation, invasiveness, and adhesion ability of the silenced cells.     

The mitochondrial genome of Ifremeria nautilei and the phylogenetic position of the enigmatic deep-sea Abyssochrysoidea (Mollusca: Gastropoda)

The complete nucleotide sequence of the mitochondrial (mt) genome of the deep-sea vent snail Ifremeria nautilei (Gastropoda: Abyssochrysoidea) was determined. The double stranded circular molecule is 15,664 pb in length and encodes for the typical 37 metazoan mitochondrial genes. The gene arrangement of the Ifremeria mt genome is most similar to genome organization of caenogastropods and differs only on the relative position of the trnW gene. The deduced amino acid sequences of the mt protein coding genes of Ifremeria mt genome were aligned with orthologous sequences from representatives of the main lineages of gastropods and phylogenetic relationships were inferred. The reconstructed phylogeny supports that Ifremeria belongs to Caenogastropoda and that it is closely related to hypsogastropod superfamilies. Results were compared with a reconstructed nuclear-based phylogeny. Moreover, a relaxed molecular-clock timetree calibrated with fossils dated the divergence of Abyssochrysoidea in the Late Jurassic–Early Cretaceous indicating a relatively modern colonization of deep-sea environments by these snails.     

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1'-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC₅H₁₀)_3-n(C₆H₁₁)_n})₂Pd(Cl)₂] (where n = 0-2), belong to a new family of easy accessible, very cheap, and air stable, but highly active and universally applicable C-C cross-coupling catalysts with an excellent functional group tolerance. Dichloro{bis[1,1'',1''''-(phosphinetriyl)tripiperidine]}palladium [(P(NC₅H₁₀)₃)₂Pd(Cl)₂] (1), the least stable complex within this series towards protons; e.g. in the form of water, allows an eased nanoparticle formation and hence, proved to be the most active Heck catalyst within this series at 100 °C and is a very rare example of an effective and versatile catalyst system that efficiently operates under mild reaction conditions. Rapid and complete catalyst degradation under work-up conditions into phosphonates, piperidinium salts and other, palladium-containing decomposition products assure an easy separation of the coupling products from catalyst and ligands. The facile, cheap, and rapid synthesis of 1,1'',1"-(phosphinetriyl)tripiperidine and 1 respectively, the simple and convenient use as well as its excellent catalytic performance in the Heck reaction at 100 °C make 1 to one of the most attractive and greenest Heck catalysts available.We provide here the visualized protocols for the ligand and catalyst syntheses as well as the reaction protocol for Heck reactions performed at 10 mmol scale at 100 °C and show that this catalyst is suitable for its use in organic syntheses.     

New herbicide-binding site in the photosynthetic electron-transport chain: Competitive herbicide binding at the photosystem I phylloquinone-(vitamin K1)-binding site

The binding of herbicides to the phylloquinone-(primary electron acceptor A₁)-binding site in green plant photosystem (PS) I reaction centers is shown. Dissociation constants (K_d) of various herbicides to the phylloquinone-binding site were estimated by analyzing their competitive inhibition of the reconstitution of the phylloquinone analogue, menadione (vitamin K₃), to the phylloquinone-extracted spinach PS I particles. The phylloquinone-binding site was found to bind o-phenanthroline (K_d = 1.2 × 10⁻⁴ M), but only weak binding was observed with atrazine (K_d > 10⁻² M), although both are known to bind specifically to the quinone-(Q_B)-binding site in reaction centers of purple photosynthetic bacteria or PS II. The inhibitors of the cytochrome b/c₁(ƒ) complex, myxothiazol (K_d=9.5 × 10⁻⁶ M) or antimycin A (K_d = 2.8 × 10⁻⁶ M), also strongly bound to the phylloquinone site. This is the first report showing that the PS I reaction center complex also has a herbicide-binding site, although the site is probably not sensitive in vivo to these herbicides due to its higher affinity for phylloquinone than herbicides. The inhibitor specificity of the PS I phylloquinone site is different from that of the other quinone-functioning sites in the photosynthetic or respiratory electron-transfer chain, suggesting it to have a unique structure.     

生物数学中的反应扩散系统的同伦映射方法

本文研究了一类非线性捕食-被捕食反应扩散系统,利用同伦映射理论,得到了初边值问题解的近似表示式。     

The effect of repetitive ankle perturbations on muscle reaction time and muscle activity

The use of a tilt platform to simulate a lateral ankle sprain and record muscle reaction time is a well-established procedure. However, a potential caveat is that repetitive ankle perturbation may cause a natural attenuation of the reflex latency and amplitude. This is an important area to investigate as many researchers examine the effect of an intervention on muscle reaction time. Muscle reaction time, peak and average amplitude of the peroneus longus and tibialis anterior in response to a simulated lateral ankle sprain (combined inversion and plantar flexion movement) were calculated in twenty-two physically active participants. The 40 perturbations were divided into 4 even groups of 10 dominant limb perturbations. Within-participants repeated measures analysis of variance (ANOVA) tests were conducted to assess the effect of habituation over time for each variable. There was a significant reduction in the peroneus longus average amplitude between the aggregated first and last 10 consecutive ankle perturbations (F_2.15,45.09 = 3.90, P = 0.03, ɳ_p² = 0.16). Authors should implement no more than a maximum of 30 consecutive ankle perturbations (inclusive of practice perturbations) in future protocols simulating a lateral ankle sprain in an effort to avoid significant attenuation of muscle activity.     

Mechanisms of sublethal copper toxicity damage to the photosynthetic apparatus of Rhodospirillum rubrum

Magnesium (Mg²⁺) is the ubiquitous metal ion present in chlorophyll and bacteriochlorophyll (BChl), involved in photosystems in photosynthetic organisms. In the present study we investigated targets of toxic copper binding to the photosynthetic apparatus of the anoxygenic purple bacterium Rhodospirillum rubrum. This was done by a combination of in vivo measurements of flash photolysis and fast fluorescence kinetics combined with the analysis of metal binding to pigments and pigment-protein complexes isolated from Cu-stressed cells by HPLC-ICPMS (ICP-sfMS). This work concludes that R. rubrum is highly sensitive to Cu²⁺, with a strong inhibition of the photosynthetic reaction centres (RCs) already at 2 μM Cu²⁺. The inhibition of growth and of RC activity was related to the formation of Cu-containing BChl degradation products that occurred much more in the RC than in LH1. These results suggest that the shift of metal centres in BChl from Mg²⁺ to Cu²⁺ can occur in vivo in the RCs of R. rubrum under environmentally realistic Cu²⁺ concentrations, leading to a strong inhibition of the function of these RCs.     

Regio- and stereospecific synthesis of rac-carbasugar-based cyclohexane pentols; Investigations of their α- and β-glucosidase inhibitions

In the present study, (3aR,7aS)-1,3,3a,4,7,7a-hexahydroisobenzofuran was submitted to photooxygenation and two isomeric hydroperoxides were successfully obtained. Without any further purification, reduction of the hydroperoxides with titanium tetraisopropoxide catalyzed by dimethyl sulfide gave two alcohol isomers in high yields. After acetylation of alcohol with Ac₂O in pyridine, epoxidation reaction of formed monoacetates with m-CPBA, then chromatographed and followed by hydrolysis of the acetate groups with NH₃ in CH₃OH resulted in the formation of epoxy alcohol isomers respectively. These epoxy alcohol isomers were subjected to trans-dihydroxylation reaction with acid (H₂SO₄) in the presence of water to afford triols. Acetylation of the free hydroxyl groups produced benzofuran triacetates in high yields. Ring-opening reaction of furan triacetates with sulfamic acid catalyzed in the presence of acetic acid/acetic anhydrate and subsequently hydrolysis of the acetate groups with ammonia gave the targeted cyclohexane carbasugar-based pentols. All products were separated and purified by chromatographic and crystallographic methods. Structural analyses of all compounds were conducted by spectral techniques including NMR and X-ray analyses. The biological inhibition activity of the target compounds was tested against glycosidase enzymes, α- and β-glucosidase.     

Delayed fluorescence from Rhodopseudomonas sphaeroides reaction centers. Enthalpy and free energy changes accompanying electron transfer from P-870 to quinones

Delayed fluorescence from isolated reaction centers of Rhodopseudomonas sphaeroides was measured to study the energetics of electron transfer from the bacteriochlorophyll complex (P-870, or P) to the primary and secondary quinones (Q_A and Q_B). The analysis was based on the assumption that electron transfer between P and Q reaches equilibrium quickly after flash excitation, and stays in equilibrium during the lifetime of the P⁺Q⁻ radical pair. Delayed fluorescence of 1Q reaction centers (reaction centers that contain only Q_A) has a lifetime of about 0.1 s, which corresponds to the decay of P⁺Q⁻_A. 2Q reaction centers (which contain both Q_A and Q_B) have a much weaker delayed fluorescence, with a lifetime that corresponds to that of P⁺Q⁻_B (about 1 s). In the presence of o-phenanthroline, the delayed fluorescence of 2Q reaction centers becomes similar in intensity and decay kinetics to that of 1Q reaction centers. From comparisons of the intensities of the delayed fluorescence from P⁺Q⁻_A and P⁺Q⁻_B, the standard free energy difference between P⁺Q⁻_A and P⁺Q⁻_B is calculated to be 78 ± 8 meV. From a comparison of the intensity of the delayed fluorescence with that of prompt fluorescence, we calculate that P⁺Q⁻_A is 0.86 ± 0.02 eV below the excited singlet state of P in free energy, or about 0.52 eV above the ground state PQ_A. The temperature dependence of the delayed fluorescence indicates that P⁺Q⁻_A is about 0.75 eV below the excited singlet state in enthalpy, or about 0.63 eV above the ground state.     

Reaction centers fromRhodopseudomonas sphaeroides in reconstituted phospholipid vesicles. I. Structural studies

Reaction centers (RCs) fromRhodopseudomonas sphaeroides were reconstituted into asolectin vesicles by cosonication. Equilibrium centrifugation on sucrose gradients showed that the vesicles were homogeneous in density (i.e., lipid-to-protein ratio) when reconstituted at a molar lipid-to-protein ratio between 500 to 1000. At lower ratios, a considerable fraction of RCs was not incorporated into closed vesicles, while at higher ratios, an increasing population of liposomes was protein-free. The average vesicle size decreased with increasing lipid-to-protein ratio, exhibiting considerable size heterogeneity within a sample. The average diameter of the largest and smallest population of vesicles, reconstituted at a molar lipid-to-protein ratio of 560, was 1200 and 400 nm, respectively. The orientation of reconstituted RCs with respect to the plane of the membrane was determined from the flash-induced rereduction kinetics of the special-pair bacteriochlorophyll dimer in the presence of reduced cytochromec. The predominant orientation of RCs was such that the cytochromec binding sites faced the external medium. The net orientation of RCs in reconstituted vesicles decreased with vesicle size and was strongly influenced by the ionic strength during reconstitution.Abbreviations RC reaction center - LDAO lauryldimethylamine-N-oxide - UQ₀/UQ₀H₂ oxidized and reduced form of 2,3-dimethoxy-5-methyl-1,4-benzoquinone - CCCP carbonyl-cyanide-trichloromethoxy phenylhydrazone - D/D⁺ reduced and oxidized form of the primary electron donor of the reaction centers. During the course of this study K. J. H. was supported by a grant from the Netherlands Organization for the Advancement of Pure Research (Z.W.O.). This research was supported by grants from the National Institutes of Health (EY-02084) and from the Office of Naval Research (ONR-NOOO 14-79-C 0798) to M. Montal.