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[en] Due to variable amino acid residues at positions 2 and 4, microcystins (MCs) had diversified variants with different toxicities. To evaluate the discrepant toxicity, the inhibition effects of five typical MC variants (with the changed amino acid residues at position 4) target to PP1 were evaluated. The inhibition sequence was verified as follows: MCLR (IC50 = 2.6 μg/L) > MCLF (IC50 = 4.4 μg/L) > MCLA (IC50 = 5.5 μg/L) > MCLY (IC50 = 7.9 μg/L) > MCLW (IC50 = 13.6 μg/L). To further clarify the inhibition mechanism for variant toxicity, the interactions between MCs and PP1 were evaluated with the assistance of MOE molecule simulation. Results show the hydrophobic interaction (Adda5 with PP1) and the hydrogen bonds (especially for Z4 → Glu275) were positively correlated with MC toxicity, while the hydrogen bonds (Leu2 ← Arg96, IsoAsp3 ← Arg96, and IsoAsp3 ← Tyr134) and the ion bonds (between Mn2+ and His173/Asn124/Asp92) were negatively correlated with toxicity. However, the hydrogen bonds (Ala1 → Glu275, Mdha7 ← Gly274, Z4 ← Arg221, and Adda5 ← His125), the covalent combination (between Mdha7 and Cys273), and the ion bonds (between Mn2+ and His248/Asp64/His66) were weakly correlated with toxicity. By further analysis, the steric hindrance and hydrophobicity introduced by different Z4 residues affected the changes for combination area and energy of MC-PP1 complexes, leading to the discrepancies in MC toxicity.
[en] Thermoluminescence spectra of manganiferous carbonatite has been studied from 30 °C to 400 °C over the wavelength range from 200 nm to 800 nm. The natural thermoluminescence appears above 200 °C and shows continuous spectral distribution from 240 nm to 800 nm. Above 500 nm the emission appears in the form of line structure emission. These are reproduced by laboratory irradiation which also produces broad bands near 100 °C. The emission features are attributed to presence of Mn2+ impurities in the carbonatite matrix. The spectral study was supplemented by kinetic analysis of the most prominent peaks and their kinetic features are reported. -- Highlights: • Thermoluminescence spectra of manganiferous carbonatite over 200 nm to 800 nm is reported. • A detailed kinetic analysis of associated electron traps has been carried out. • The emission is linked to Mn2+ impurities and transitions involved are proposed
[en] The indirect-coupling model is used to analyze the exchange magnetic structure of Pb3Mn7O15 in the hexagonal setting. The ratios of manganese ions Mn4+/Mn3+ in each nonequivalent position are determined. Pb3(Mn0.95Ge0.05)7O15 and Pb3(Mn0.95Ga0.05)7O15 single crystals are grown by the solution–melt method in order to test the validity of the proposed model. The structural and magnetic properties of the single crystals are studied. The magnetic properties of the grown single crystals are compared with those of nominally pure Pb3Mn7O15.
[en] The electron spin resonance in single crystals of manganese acetate tetrahydrate has been studied from the liquid nitrogen temperature to 373 K. The spectrum at any temperature consists of one single resonance line with an isotropic g-value. The effect of the temperature on the line position and on the linewidth was investigated and some possible sources of the behaviour against the temperature have been presented. (author)
[en] The GB virus-B (GBV-B) nonstructural protein 5B (NS5B) encodes an RNA-dependent RNA polymerase (RdRp) with greater than 50% sequence similarity to the hepatitis C virus (HCV) NS5B. Recombinant GBV-B NS5B was reported to possess RdRp activity (W. Zhong et al., 2000, J. Viral Hepat. 7, 335-342). In this study, the GBV-B RdRp was examined more thoroughly for different RNA synthesis activities, including primer-extension, de novo initiation, template switch, terminal nucleotide addition, and template specificity. The results can be compared with previous characterizations of the HCV RdRp. The two RdRps share similarities in terms of metal ion and template preference, the abilities to add nontemplated nucleotides, perform both de novo initiation and extension from a primer, and switch templates. However, several differences in RNA synthesis between the GBV-B and HCV RdRps were observed, including (i) optimal temperatures for activity, (ii) ranges of Mn2+ concentration tolerated for activity, and (iii) cation requirements for de novo RNA synthesis and terminal transferase activity. To assess whether the recombinant GBV-B RdRp may represent a relevant surrogate system for testing HCV antiviral agents, two compounds demonstrated to be active at nanomolar concentrations against HCV NS5B were tested on the GBV RdRp. A chain terminating nucleotide analog could prevent RNA synthesis, while a nonnucleoside HCV inhibitor was unable to affect RNA synthesis by the GBV RdRp
[en] Magnetotransport properties of the compound Ca4Mn3O10 are interpreted in terms of activated hopping of small magnetic polarons in the non-adiabatic regime. Polarons are most probably formed around Mn3+ sites created by oxygen sub-stoichiometry. The application of an external field reduces the size of the magnetic contribution to the hopping barrier and thus produces an increase in the conductivity. We argue that the change in the effective activation energy around TN is due to the crossover to variable range hopping conduction as antiferromagnetic order sets in
[en] Highlights: •The Curie–Weiss law is redefined in the studied temperature range. •This will lead to a homogeneous macroscopic electronic state picture. •It is in contrast with the coexistence of insulating and metallic regions. -- Abstract: We study the nature of short-range magnetic interactions observed in the paramagnetic phase of colossal magnetoresistance compounds. Our results reveal that ferromagnetic-like interaction between Mn ions cannot be explained by the conventional double exchange mechanism. The results show evidence that the eg electrons are localized in Mn3+ ions regardless the introduction of holes leading to ferromagnetic/antiferromagnetic superexchange-like interactions
[en] The interfacial spin state of the multiferroic heterostructure PbZr0.52Ti0.48O3/La0.67Sr0.33MnO3 and its dependence on ferroelectric polarization is investigated with magnetic second-harmonic generation at 78 K. The spin alignment of Mn ions in the first unit cell layer at the heterointerface can be tuned from ferromagnetic to antiferromagnetic exchange coupled, while the bulk magnetization remains unchanged. Multiple domains of both phases coexist as the ferroelectric polarization is switched. The results will help promote the development of new interface-based functionalities and device concepts