Many short cationic peptides have been identified as potent antimicrobial agents, but their modes of action are not well understood. Peptide synthesis on cellulose membranes has resulted in the ...generation of peptide libraries, while high-throughput assays have been developed to test their antibacterial activities. In this paper a microtiter plate-based screening method for fungi has been developed and used to test nine antibacterial peptides against the model fungus Aspergillus nidulans. Microscopical studies using sublethal peptide concentrations caused defects in polarized growth, including increased branch formation and depolarized hyphae. We characterized the mode of action for one of our target peptides, Sub5 (12 amino acids), which has already been shown to possess pharmacological potential as an antibacterial agent and is able to interact with ATP and ATP-dependent enzymes. The MIC for A. nidulans is 2 μg/ml, which is in the same range as the MICs reported for bacteria. Fluorescein isothiocyanate (FITC)-labeled Sub5 targeted the cytoplasmic membrane, particularly hyphal tips, and entered the cytoplasm after prolonged exposure, independent of endocytosis. Interestingly, Sub5 peptide treatment disturbed sterol-rich membrane domains, important for tip growth, at hyphal tips. A very similar peptide, FITC-P7, also accumulated on the cell membrane but did not have antibacterial or antifungal activity, suggesting that the cytoplasmic membrane is a first target for the Sub5 peptide; however, the antifungal activity seems to be correlated with the ability to enter the cytoplasm, where the peptides might act on other targets.
Most known compounds with five-coordinated Ti
are natural and synthetic titanosilicates. The crystal structure of natural fresnoite, Ba
TiSi
O
tetragonal, space group P4bm, a = 8.510 (1) Å, c = 5.197 ...(1) Å, V = 376.4 (1) Å
, Z = 2, has been refined to R = 0.011 on the basis of 807 unique single-crystal reflections with I > 2σ(I). Titanium has fivefold coordination with one short (`titanyl') bond of 1.692 (5) Å. Bonds in the TiO
polyhedron are discussed in comparison to analogous coordination polyhedra in other minerals and compounds. A review of all known compounds with Ti
O
polyhedra shows that most of them are titanosilicates in which titanium forms a short Ti-O bond (∼1.61 to ∼1.77 Å). Poor Gladstone-Dale compatibility between chemical composition, optical characteristics and density of these compounds is explained by the anomalous contribution of
Ti
to the optical properties as shown by calculations based on the relationship between electronic polarizabilities and refractive indices. An improved Gladstone-Dale coefficient of 0.29 is suggested for TiO
with
Ti
. A negative correlation between `titanyl' bond lengths and wavenumbers of the bands of Ti-O stretching vibrations (in the range of 890-830 cm
) in infrared and Raman spectra is observed.
Most known compounds with five‐coordinated Ti4+ are natural and synthetic titanosilicates. The crystal structure of natural fresnoite, Ba2TiSi2O8 tetragonal, space group P4bm, a = 8.510 (1) Å, c = ...5.197 (1) Å, V = 376.4 (1) Å3, Z = 2, has been refined to R = 0.011 on the basis of 807 unique single‐crystal reflections with I > 2σ(I). Titanium has fivefold coordination with one short (`titanyl') bond of 1.692 (5) Å. Bonds in the TiO5 polyhedron are discussed in comparison to analogous coordination polyhedra in other minerals and compounds. A review of all known compounds with Ti4+O5 polyhedra shows that most of them are titanosilicates in which titanium forms a short Ti—O bond (∼1.61 to ∼1.77 Å). Poor Gladstone–Dale compatibility between chemical composition, optical characteristics and density of these compounds is explained by the anomalous contribution of 5Ti4+ to the optical properties as shown by calculations based on the relationship between electronic polarizabilities and refractive indices. An improved Gladstone–Dale coefficient of 0.29 is suggested for TiO2 with 5Ti4+. A negative correlation between `titanyl' bond lengths and wavenumbers of the bands of Ti—O stretching vibrations (in the range of 890–830 cm−1) in infrared and Raman spectra is observed.
The crystal structure of natural fresnoite is refined. An improved Gladstone–Dale coefficient of 0.29 is suggested for TiO2 with 5Ti4+.
Cell wall formation and maintenance are crucial for hyphal morphogenesis. In many filamentous fungi, chitin is one of the main structural components of the cell wall. Aspergillus nidulans ChsB, a ...chitin synthase, and CsmA, a chitin synthase with a myosin motor-like domain (MMD) at its N-terminus, both localize predominantly at the hyphal tip regions and at forming septa. ChsB and CsmA play crucial roles in polarized hyphal growth in A. nidulans. In this study, we investigated the mechanism by which CsmA and ChsB accumulate at the hyphal tip in living hyphae. Deletion of kinA, a gene encoding conventional kinesin (kinesin-1), impaired the localization of GFP-CsmA and GFP-ChsB at the hyphal tips. The transport frequency of GFP-CsmA and GFP-ChsB in both anterograde and retrograde direction appeared lower in the kinA-deletion strain compared to wild type, although the velocities of the movements were comparable. Co-localization of GFP-ChsB and GFP-CsmA with mRFP1-KinArigor, a KinA mutant that binds to microtubules but does not move along them, was observed in the posterior of the hyphal tip regions. KinA co-immunoprecipitated with ChsB and CsmA. Co-localization and association of CsmA with KinA did not depend on the MMD. These findings indicate that ChsB and CsmA are transported along microtubules to the subapical region by KinA.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Nematode-trapping fungi (NTF), such as Arthrobotrys flagrans (Duddingtonia flagrans), are soil-borne fungi able to form adhesive trapping networks to attract and catch nematodes. In this forum piece ...we highlight some of their most fascinating features with a special focus on the role of small-secreted proteins in the predatory interaction.
Plant‐parasitic nematodes cause devastating agricultural damage worldwide. Only a few synthetic nematicides can be used and their application is limited in fields. Therefore, there is a need for ...sustainable and environment‐friendly alternatives. Nematode‐trapping fungi (NTF) are natural predators of nematodes. They capture and digest them with their hyphae and are starting to being used as bio‐control agents. In this study, we applied the NTF Arthrobotrys flagrans (Duddingtonia flagrans) against the wine pathogenic nematode Xiphinema index. A. flagrans reduced the number of X. index juveniles in pot cultures of Ficus carica, an alternative host plant for X. index, significantly. Sodium‐alginate pellets with A. flagrans spores were produced for vineyard soil inoculation under laboratory conditions. The NTF A. conoides, A. musiformis and A. superba were enriched from several soil samples, showing their natural presence. Trap formation is an energy‐consuming process and depends upon various biotic and abiotic stimuli. Here, we show that bacteria of the genus Delftia, Bacillus, Pseudomonas, Enterobacter and Serratia induced trap formation in NTF like A. conoides and A. oligospora but not in A. flagrans in the absence of nematodes. The application of NTF along with such bacteria could be a combinatorial way of efficient biocontrol in nematode‐infested soil.
Empirical electronic polarizabilities allow the prediction of total mineral polarizabilities and mean refractive indices of the vast majority of minerals and synthetic oxides. However, deviations ...from the valence-sum rule at cations in some minerals are associated with large deviations of observed from calculated total polarizabilities. We have identified several groups of minerals and compounds where deviations from the valence-sum rule at cations lead to polarizability deviations of 2–5%: M(SO
4
)·
n
H
2
O,
n
= 1–6, blödite-group minerals Na
2
M
2+
(SO
4
)
2
·4H
2
O, and the kieserite-related minerals: isokite, panasqueiraite and tilasite. In these minerals, the environment of the M ions contains both O and H
2
O: MgO
4
(H
2
O)
2
in kieserite, szmikite, and szomolnokite; MgO
2
(H
2
O)
4
in starkeyite, ilesite, and rozenite, and Mg(H
2
O)
6
in hexahydrite. In compounds where the ligands are only H
2
O, deviations from the valence-sum rule at the M(H
2
O)
6
groups are not accompanied by significant polarizability deviations. This is the case for epsomite, MgSO
4
·7H
2
O; bieberite, CoSO
4
·7H
2
O; goslarite, ZnSO
4
·7H
2
O, six silicofluorides, MSiF
6
·6H
2
O; eighteen Tutton’s salts, M
2
M′(SO
4
)
2
·6H
2
O, where M = K, Rb, Cs and M′ = Mg, Mn, Fe, Co, Ni, Cu, and Zn; and eleven MM′(SO
4
)
2
·12H
2
O alums, where M = Na, K, Rb and Cs, and M′ = Al, Cr, Ga and In. This is also the case for the sulfates alunogen, Al
2
(SO
4
)
3
·17H
2
O and halotrichite, FeAl
2
(SO
4
)
4
·22H
2
O; three hydrated nitrates; one phosphate; three antimonates and two hydrated perchlorates. A possible explanation for this different behavior is that the bond-valence model treats O and H separately, whereas polarizability calculations treat the polarizability of the entire H
2
O molecule.
We report on the temperature-dependent structural studies on the mullite-type Bi2Fe4O9 compound. The crystal structures were determined using both powder X-ray diffraction and single crystal neutron ...diffraction. The thermal expansion of the cell parameters from smallest to largest occurred in the order a<c<b; their expansion behavior was fit using either linear or nonlinear regression according to the region of choice. The anisotropic thermal expansion was monitored with respect to the expansion coefficients, anisotropy factor, and polyhedral geometry. At 900K an abrupt change of the anisotropy factor is observed which correlates with a slope in the BiO6 polyhedral volume. At the same temperature the FeO4 tetrahedral distortion starts to increase. The temperature-dependent stereochemically activity of the Bi3+ 6s2 lone electron pair was probed by the absolute value of eccentricity parameter. This parameter shows a significant drop at around 773K. Additionally, the average crystal size and micro-strain of the powder samples were studied. A healing of intrinsic defects is observed with respect to a decreasing micro-strain followed by crystal growth above about 900K. The temperature-dependent infrared spectra were described in three distinct zones. Deconvolution of the absorption features between 370cm−1 and 1000cm−1 required nine fitted bands, and the decomposed Pseudo-Voigt elements were assigned to Fe–O stretching, Fe–O–Fe bending and O–Fe–O bending vibrations. The shift of the observed modes was described with respect to temperature. An effective linewidth parameter Δcorr was determined by autocorrelation analysis between 740cm−1 and 900cm−1 for each temperature-dependent spectrum. The break of the slope of Δcorr at about 773K was interpreted as the change of some vibrational modes of the FeO4 tetrahedra. The intrinsic effects observed around 773K are responsible for extrinsic parameter changes found around 900K.
Temperature-dependent stereochemical activity (eccentricity |Φi|) of the Bi3+ 6s2 lone electron pair directing in the non-bonded region of the Bi–O coordination in the Bi2Fe4O9 iron framework (given as polyhedra). Display omitted
► Complex expansion–contraction mechanism explains anisotropic thermal expansion. ► Bi 6s2 lone electron pair sphericity influences analyses by FTIR autocorrelation. ► Intrinsic effects at 773K are responsible for extrinsic parameter changes at 900K.
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