Insight into the Assembly Properties and Functional Organisation of the Magnetotactic Bacterial Actin-like Homolog, MamK

Magnetotactic bacteria (MTB) synthesize magnetosomes, which are intracellular vesicles comprising a magnetic particle. A series of magnetosomes arrange themselves in chains to form a magnetic dipole that enables the cell to orient itself along the Earth’s magnetic field. MamK, an actin-like homolog of MreB has been identified as a central component in this organisation. Gene deletion, fluorescence microscopy and in vitro studies have yielded mechanistic differences in the filament assembly of MamK with other bacterial cytoskeletal proteins within the cell. With little or no information on the structural and behavioural characteristics of MamK outside the cell, the mamK gene from Magnetospirillium gryphiswaldense was cloned and expressed to better understand the differences in the cytoskeletal properties with its bacterial homologues MreB and acitin. Despite the low sequence identity shared between MamK and MreB (22%) and actin (18%), the behaviour of MamK monitored by light scattering broadly mirrored that of its bacterial cousin MreB primarily in terms of its pH, salt, divalent metal-ion and temperature dependency. The broad size variability of MamK filaments revealed by light scattering studies was supported by transmission electron microscopy (TEM) imaging. Filament morphology however, indicated that MamK conformed to linearly orientated filaments that appeared to be distinctly dissimilar compared to MreB suggesting functional differences between these homologues. The presence of a nucleotide binding domain common to actin-like proteins was demonstrated by its ability to function both as an ATPase and GTPase. Circular dichroism and structural homology modelling showed that MamK adopts a protein fold that is consistent with the ‘classical’ actin family architecture but with notable structural differences within the smaller domains, the active site region and the overall surface electrostatic potential

Wplyw procesu kulinarnego na jakosc wybranych warzyw

W pracy przedstawiono wpływ procesu kulinarnego, w tym obierania i gotowania, na jakość wybranych warzyw (brukselka, marchew, ziemniaki) z uwzględnieniem wartości odżywczej, jakości sensorycznej i poziomu zanieczyszczeń chemicznych. Zastosowano 3 metody gotowania z użyciem dużej ilości wody: w garnku przy rozpoczęciu procesu od wody zimnej i od wody wrzącej, w szybkowarze w wodzie oraz 3 metody z wykorzystaniem małej ilości wody: w kuchni mikrofalowej, w szybkowarze w parze, w garnku akutermicznym. Na podstawie badań stwierdzono, że metoda gotowania powinna być uzależniona od wartości odżywczej i poziomu zanieczyszczeń chemicznych. Do warzyw o niskim stopniu zanieczyszczenia korzystniej jest stosować metody gotowania z małą ilością wody, gdyż lepiej zachowują one wartość odżywczą, a usuwanie zanieczyszczeń nie ma tu znaczenia. Warzywa znacznie zanieczyszczone chemicznie lepiej gotować w dużej ilości wody, ze względu na eluację zanieczyszczeń.Effect of peeling and cooking method on selected vegetables quality described by nutritional value, sensory quality and contamination level was investigated. Six cooking methods were used: in pot starting process from cold and boiling water; in pressure cooker in water and in steam; in microwave oven and in acuthermal pot. Cooking method should be depended on nutritional value and contamination level. For noncontaminated vegetables cooking methods with small amounts of water should be used because it allows to retain nutrients. Cooking methods with a lot amount of water should be advised for contaminated vegetables

Divalent cation-, nucleotide-, and polymerization-dependent changes in the conformation of subdomain 2 of actin.

Conformational changes in subdomain 2 of actin were investigated using fluorescence probes dansyl cadaverine (DC) or dansyl ethylenediamine (DED) covalently attached to Gln41. Examination of changes in the fluorescence emission spectra as a function of time during Ca2+/Mg2+ and ATP/ADP exchange at the high-affinity site for divalent cation-nucleotide complex in G-actin confirmed a profound influence of the type of nucleotide but failed to detect a significant cation-dependent difference in the environment of Gln41. No significant difference between Ca- and Mg-actin was also seen in the magnitude of the fluorescence changes resulting from the polymerization of these two actin forms. Evidence is presented that earlier reported cation-dependent differences in the conformation of the loop 38-52 may be related to time-dependent changes in the conformation of subdomain 2 in DED- or DC-labeled G-actin, accelerated by substitution of Mg2+ for Ca2+ in CaATP-G-actin and, in particular, by conversion of MgATP- into MgADP-G-actin. These spontaneous changes are associated with a denaturation-driven release of the bound nucleotide that is promoted by two effects of DED or DC labeling: lowered affinity of actin for nucleotide and acceleration of ATP hydrolysis on MgATP-G-actin that converts it into a less stable MgADP form. Evidence is presented that the changes in the environment of Gln41 accompanying actin polymerization result in part from the release of Pi after the hydrolysis of ATP on the polymer. A similarity of this change to that accompanying replacement of the bound ATP with ADP in G-actin is discussed

Plony i jakosc zielonki di- i tetraploidalnych form koniczyny czerwonej

The purpose of the study has been to determine the yield, chemical composition and nutritive value of green forage from di- and tetraploid forms of red clover grown in different seed density regimes. The yield of green forage was analysed in the first year of full use, in 2003 and 2004, having cut the plants in the early inflorescence phase (1st cut). In green forage samples, the following were determined: basic chemical composition, concentration of water soluble carbohydrates (WSC), fibre fractions (NDF, ADF and ADL) and macronutrients (P, K, Mg, Ca, Na). The nutritive value of green forage was expressed according to the INRA 1988 system. The yield of green matter from the tetraploid cultivars Bona and Jubilatka was higher than from the diploid cultivars Krynia and Parada. The cultivar Bona distinguished itself by its highest average yield of green matter, dry matter, total protein and net energy. The dry matter content was the most variable green forage quality characteristic. In both years, green forage from the diploid cultivars contained more dry matter than the one made from the tetraploid varieties. At the same time, seed density did not have any significant influence on the differentiation of green forage yields. Green forage from the two diploid cultivars was characterised by a similar energy and protein value and a better fill unit value (better potential intake by ruminants). The concentrations of phorphorus, potassium and calcium in green forage from the diploid forms were slightly higher compared to the tetraploid forms, unlike the level of magnesium, which was slightly lower. Irrespectively of the polidy level, the concentration of macronutrients, except phosphorus, was higher in the first year of the study. Considering the nutritional requirements of animals, green forage from the analysed red clover cultivars was characterised by an inadequate level of magnesium, deficient amount of sodium and an improper Ca:P ratio. The results suggest that diploid forms of red clover can potentially generate a higher nutrititive value than tetraploid ones.Celem badań było określenie plonowania oraz składu chemicznego i wartości pokarmowej zielonki di- i tetraploidalnych odmian koniczyny czerwonej uprawianej z zastosowaniem różnej gęstości siewu nasion. Plon zielonki analizowano w pierwszym roku pełnego użytkowania w latach 2003 i 2004, po skoszeniu roślin w fazie początku kwitnienia (I pokos). W próbach zielonki oznaczono podstawowy skład chemiczny, zawartość cukrów rozpuszczalnych w wodzie (WSC), frakcje włókna (NDF, ADF i ADL) i makroelementy (P, K, Mg, Ca, Na). Wartość pokarmową zielonki wyrażono według systemu INRA 1988. Plon zielonej masy odmian tetraploidalnych Bona i Jubilatka był wyższy niż odmian diploidalnych Krynia i Parada. Wyróżniała się odmian Bona, dla której stwierdzono najwyższy średni plon zielonej masy, suchej masy, białka ogólnego i energii netto. Cechą jakościową zielonki o największej zmienności była zawartość suchej masy. W obu latach użytkowania zielonka odmian diploidalnych miała wyższą zawartość suchej masy niż zielonka odmian tetraploidalnych. Jednocześnie gęstość siewu nasion nie miała istotnego wpływu na zróżnicowanie plonów zielonki. W przypadku zielonki odmian diploidalnych stwierdzono zbliżoną wartość energetyczną i białkową oraz korzystniejszą wartość wypełnieniową (większa możliwością pobrania przez przeżuwacze). Poziom fosforu, potasu i wapnia w zielonkach odmian diploidalnych był nieznacznie wyższy, a magnezu niższy w porównaniu z odmianami tetraploidalnymi. Niezależnie od poziomu ploidalności odmian koncentracja makroelementów, z wyjątkiem fosforu, była wyższa w pierwszym roku badań. Uwzględniając wymagania pokarmowe zwierząt, zielonka badanych odmian koniczyny miała odpowiedni poziom magnezu, niedoborową ilość sodu oraz niewłaściwy stosunek Ca:P. Uzyskane wyniki wskazują, że odmiany diploidalne koniczyny czerwonej mają możliwości osiągania wyższej wartości pokarmowej niż odmiany tetraploidalne

Neptune’s ring arcs from VLT/SPHERE-IRDIS near-infrared observations

International audienceContext. Neptune’s incomplete ring arcs have been stable since their discovery in 1984 by stellar occultation. Although these structures should be destroyed within a few months through differential Keplerian motion, imaging data over the past couple of decades have shown that these structures remain stable.Aims. We present the first SPHERE near-infrared observations of Neptune’s ring arcs taken at 2.2 μm (broadband Ks) with the IRDIS camera at the Very Large Telescope (VLT) in August 2016.Methods. The images were aligned using the ephemerides of the satellite Proteus and were suitably co-added to enhance ring and satellite signals.Results. We analyse high-angular-resolution near-infrared images of Neptune’s ring arcs obtained in 2016 at the ESO VLT-UT3 with the adaptive-optics-fed camera SPHERE-IRDIS. We derive accurate mean motion values for the arcs and the nearby satellite Galatea. The trailing arcs Fraternité and Égalité have been stable since they were last observed in 2007. Furthermore, we confirm the fading away of the leading arcs Courage and Liberté. Finally, we confirm the mismatch between the arcs’ position and the 42:43 inclined and eccentric corotation resonances with Galatea, thus demonstrating that no 42:43 corotation model works to explain the azimuthal confinement of the arcs’ materiel

Capability of Semiconducting NiO Films in Gamma Radiation Dosimetry

Electrical properties of RF magnetron sputtered p-NiO films were characterized after fabrication and after gamma irradiations using $\text{}^{137}Cs$ and $\text{}^{60}Co$ sources. Electrical parameters are obtained from the Hall measurements, impedance spectroscopy and C-V measurement of n-Si/p-NiO junction diodes. The results show that resistivity of the NiO film is gradually increased following after sequential irradiation processes because of the decrease in holes' concentration. Hole concentration of a NiO film decreases from the original value of $4.36 \times 10^{16} cm^{-3}$ to $2.86 \times 10^{16} cm^{-3}$ after $\text{}^{137}Cs γ$ irradiation with doses of 10 Gy. In the case of γ irradiation from $\text{}^{60}Co$ source, hole concentration of the film decreases from $6.3 \times 10^{16}//cm^3$ to $4.1 \times 10^{16}//cm^3$ and to $2.9 \times 10^{16}//cm^3$ after successive expositions with a dose of 20 Gy