Influenza virus is taken up from a pH-neutral extracellular milieu into an endosome, whose contents then acidify, causing changes in the viral matrix protein (M1) that coats the inner monolayer of ...the viral lipid envelope. At a pH of ~6, M1 interacts with the viral ribonucleoprotein (RNP) in a putative priming stage; at this stage, the interactions of the M1 scaffold coating the lipid envelope are intact. The M1 coat disintegrates as acidification continues to a pH of ~5 to clear a physical path for the viral genome to transit from the viral interior to the cytoplasm. Here we investigated the physicochemical mechanism of M1's pH-dependent disintegration. In neutral media, the adsorption of M1 protein on the lipid bilayer was electrostatic in nature and reversible. The energy of the interaction of M1 molecules with each other in M1 dimers was about 10 times as weak as that of the interaction of M1 molecules with the lipid bilayer. Acidification drives conformational changes in M1 molecules due to changes in the M1 charge, leading to alterations in their electrostatic interactions. Dropping the pH from 7.1 to 6.0 did not disturb the M1 layer; dropping it lower partially desorbed M1 because of increased repulsion between M1 monomers still stuck to the membrane. Lipid vesicles coated with M1 demonstrated pH-dependent rupture of the vesicle membrane, presumably because of the tension generated by this repulsive force. Thus, the disruption of the vesicles coincident with M1 protein scaffold disintegration at pH 5 likely stretches the lipid membrane to the point of rupture, promoting fusion pore widening for RNP release.
Influenza remains a top killer of human beings throughout the world, in part because of the influenza virus's rapid binding to cells and its uptake into compartments hidden from the immune system. To attack the influenza virus during this time of hiding, we need to understand the physical forces that allow the internalized virus to infect the cell. In particular, we need to know how the protective coat of protein inside the viral surface reacts to the changes in acid that come soon after internalization. We found that acid makes the molecules of the protein coat push each other while they are still stuck to the virus, so that they would like to rip the membrane apart. This ripping force is known to promote membrane fusion, the process by which infection actually occurs.
Core-shell FexOy@C nanoparticles (NPs) modified with Ag were studied with x-ray diffraction, transmission electron microscopy, energy dispersive elemental mapping, Mössbauer spectroscopy, static ...magnetic measurements, and optical magnetic circular dichroism (MCD). FexOy@C NPs synthesized by the pyrolysis process of the mixture of Fe(NO3)3 · 9H2O with oleylamine and oleic acid were added to a heated mixture of oleylamine and AgNO3 in different concentrations. The final product was a mixture of iron oxide crystalline NPs in an amorphous carbon shell and Ag crystalline NPs. The iron oxide NPs were presented by two magnetic phases with extremely close crystal structures: Fe3O4 and γ-Fe2O3. Ag is shown to form crystalline NPs located very close to the iron oxide NPs. An assumption is made about the formation of hybrid FexOy@C-Ag NPs. Correlations were obtained between the Ag concentration in the fabricated samples, their magnetic properties and the MCD spectrum shape. Introducing Ag led to a approximately linear decrease of the NPs saturation magnetization depending upon the Ag concentration, it also resulted into the MCD spectrum shift to the lower light wave energies. MCD was also studied for the Fe3O4@C NPs synthesized earlier with the same one-step process using different heat treatment temperatures, and MCD spectra were compared for two series of NPs. A possible contribution of the surface plasmon excitation in Ag NPs to the MCD spectrum of the FexOy@C-Ag NPs is discussed.
•Single crystals of of the warwickites Mn2-xFexBO4 (x=0.3, 0.5, 0.7) have been synthesized.•Crystal and local atomic structure has been studied through X-ray diffraction and X-ray absorption ...spectroscopy.•The Fe-doping was found to enhance the magnetic frustation giving rise to the supression of the long-range magnetic order.
Single crystalline Mn2-xFexBO4 with x=0.3, 0.5, 0.7 grown by the flux method have been studied by means of X-ray diffraction and X-ray absorption spectroscopy at both Mn and Fe K edges. The compounds were found to crystallize in an orthorhombic warwickite structure (sp. gr. Pnam). The lattice parameters change linearly with x thus obeying the Vegard’s law. The Fe3+ substitution for Mn3+ has been deduced from the X-ray absorption near-edge structure (XANES) spectra. Two energy positions of the absorption edges have been observed in Mn K-edge XANES spectra indicating the presence of manganese in two different oxidation states. Extended X-ray absorption fine structure (EXAFS) analysis has shown the reduction of local structural distortions upon Fe substitution. The magnetization data have revealed a spin-glass transition at TSG=11, 14 and 18K for x=0.3, 0.5 and 0.7, respectively.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Nanoparticles of Co
1 –
x
Mg
x
Fe
2
O
4
with
x
equal to 0, 0.2, 0.4, 0.6, 0.8, and 1.0 have been synthesized. For all values of
x
, they are nanocrystals with a cobalt ferrite structure and an ...average linear size (
nm. Based on the analysis of the Mössbauer effect spectra, the Co
2+
ions were shown to occupy only octahedral positions at all values of
x
. The experimentally obtained dependence of the nanoparticles magnetization on
x
corresponds to the dependence calculated using the Mössbauer effect data, except for the sample with
. The effective magnetic anisotropy constant estimated for 0 K from the analysis of the coercive force temperature dependences decreases from
at
to
erg/cm
3
at
and drops sharply to
erg/cm
3
at
.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Here, we suggested that the epigenetic mechanism of benzo(a)pyrene (BP) action might be based on the aryl hydrocarbon receptor (AhR)-mediated transcription of the target genes, including miRNAs, that ...have the dioxin response element (DRE) in their promoters. The effect of BP on the expression of the oncogenic miR-483-3p, its host gene
IGF2
, and target gene
IGF1
in primary hepatocytes and in the liver of Wistar female rats was investigated. The activation of AhR was confirmed using selective AhR inhibitor CH-223191 and by evaluating expression of the target
CYP1A1
gene. The lack of coordination between the expression of miR-483-3p and its host gene
IGF2
was revealed, which may be due to the presence of the binding site for the estrogen receptor alpha (ERα), which is a negative expression regulator. Our results confirm the existence of the AhR-mediated pathway in the regulation of expression of miR-483-3p,
IGF1
, and
IGF2
under BP exposure, which is of considerable interest for understanding the epigenetic mechanisms of the carcinogenic effect of BP.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Single‐crystalline MgFeBO4, Mg0.5Co0.5FeBO4, and CoFeBO4 have been grown by the flux method. The samples have been characterized by X‐ray spectral analysis, X‐ray diffraction, and X‐ray absorption ...spectroscopy. The X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS) spectra have been measured at the Fe and Co K‐edges over a wide temperature range (6.5–300 K). The composition, the charge state, and local environment of both Fe and Co atoms have been determined. The effects of Co substitution for Mg on the local structural distortions have been revealed experimentally and the MO bond anisotropy has been found.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Abstract
We report a study of the magnetodynamics of cobalt ferrite (CoFe
2
O
4
) nanoparticles with an average diameter of ∼6 nm. Hysteresis loops were measured under quasi-static conditions and in ...pulse fields with amplitudes H
0
of up to 130 kOe and for durations
τ
P
of 8 and 16 ms. The growth of coercivity
H
c
observed with an increase in the magnetic field variation rate
dH
/
dt
(determined by the values of
H
0
and
τ
P
) and the reduction of
H
c
with temperature is ascribed to the superparamagnetic effect. The proposed theoretical model explains the observed dependences fairly well. Notably, the effective magnetic anisotropy constant obtained exceeds the value for bulk crystals and might be indicative of the contribution of surface magnetic anisotropy.
Abstract
Core–shell Fe
x
O
y
@C nanoparticles (NPs) modified with Ag were studied with x-ray diffraction, transmission electron microscopy, energy dispersive elemental mapping, Mössbauer ...spectroscopy, static magnetic measurements, and optical magnetic circular dichroism (MCD). Fe
x
O
y
@C NPs synthesized by the pyrolysis process of the mixture of Fe(NO
3
)
3
· 9H
2
O with oleylamine and oleic acid were added to a heated mixture of oleylamine and AgNO
3
in different concentrations. The final product was a mixture of iron oxide crystalline NPs in an amorphous carbon shell and Ag crystalline NPs. The iron oxide NPs were presented by two magnetic phases with extremely close crystal structures: Fe
3
O
4
and γ-Fe
2
O
3
. Ag is shown to form crystalline NPs located very close to the iron oxide NPs. An assumption is made about the formation of hybrid Fe
x
O
y
@C-Ag NPs. Correlations were obtained between the Ag concentration in the fabricated samples, their magnetic properties and the MCD spectrum shape. Introducing Ag led to a approximately linear decrease of the NPs saturation magnetization depending upon the Ag concentration, it also resulted into the MCD spectrum shift to the lower light wave energies. MCD was also studied for the Fe
3
O
4
@C NPs synthesized earlier with the same one-step process using different heat treatment temperatures, and MCD spectra were compared for two series of NPs. A possible contribution of the surface plasmon excitation in Ag NPs to the MCD spectrum of the Fe
x
O
y
@C-Ag NPs is discussed.
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