The high‐pressure elastic properties behavior, phase stability, and mechanisms of amorphization of the alumino‐silicate 7:4 mullite and a corresponding mullite doped with boron were investigated in ...situ by powder synchrotron X‐ray diffraction with a diamond anvil cell in quasi‐hydrostatic conditions. The samples of 7Al2O3:4SiO2 (Al4.66Si1.33O9.67), referred to as 7:4 mullite and an alumino‐silicate mullite with 3.5(4) mol% B2O3, referred to as B‐mullite, were compressed, in small pressure steps, up to 27.8 and 28.9 GPa, respectively, and then decompressed back to ambient pressure. All along the compression path both samples' patterns are indexable with a mullite structure. Compression data are smooth up to a threshold pressure, from which point the diffraction peaks appeared to broaden, and the refined unit cell parameters deviate significantly down from the compressional trend. Above ~23 GPa the diffraction patterns are not indexable anymore, suggesting amorphization. Rietveld structural refinements allow for a description of the pressure‐induced main deformation mechanisms and structural trends. Pressure‐induced mechanisms of amorphization are also discussed. A third‐order Birch Murnaghan equation of state is fitted to the pressure‐volume data to obtain experimental bulk moduli, as well as axial compressibilities for 7:4 mullite and B‐mullite. Finally the volume compression in response to the applied pressure, combined with thermal expansion coefficients, allows a P–T–V equation‐of‐state for B‐mullite to be proposed.
Polarized growth of filamentous fungi requires continuous transport of biomolecules to the hyphal tip. To this end, construction materials are packaged in vesicles and transported by motor proteins ...along microtubules and actin filaments. We have studied these processes with quantitative superresolution localization microscopy of live
cells expressing the photoconvertible protein mEosFP
fused to the chitin synthase ChsB. ChsB is mainly located at the Spitzenkörper near the hyphal tip and produces chitin, a key component of the cell wall. We have visualized the pulsatory dynamics of the Spitzenkörper, reflecting vesicle accumulation before exocytosis and their subsequent fusion with the apical plasma membrane. Furthermore, high-speed pulse-chase imaging after photoconversion of mEosFP
in a tightly focused spot revealed that ChsB is transported with two different speeds from the cell body to the hyphal tip and vice versa. Comparative analysis using motor protein deletion mutants allowed us to assign the fast movements (7 to 10 μm s
) to transport of secretory vesicles by kinesin-1, and the slower ones (2 to 7 μm s
) to transport by kinesin-3 on early endosomes. Our results show how motor proteins ensure the supply of vesicles to the hyphal tip, where temporally regulated exocytosis results in stepwise tip extension.
Aspergillus nidulans is able to synthesize penicillin and serves as a model to study the regulation of its biosynthesis. Only three enzymes are required to form the beta lactam ring tripeptide, which ...is comprised of l-cysteine, l-valine and l-aminoadipic acid. Whereas two enzymes, AcvA and IpnA localize to the cytoplasm, AatA resides in peroxisomes. Here, we tested a novel strategy to improve penicillin production, namely the change of the residence of the enzymes involved in the biosynthesis. We tested if targeting of AcvA or IpnA (or both) to peroxisomes would increase the penicillin yield. Indeed, AcvA peroxisomal targeting led to a 3.2-fold increase. In contrast, targeting IpnA to peroxisomes caused a complete loss of penicillin production. Overexpression of acvA, ipnA or aatA resulted in 1.4, 2.8 and 3.1-fold more penicillin, respectively in comparison to wildtype. Simultaneous overexpression of all three enzymes resulted even in 6-fold more penicillin. Combination of acvA peroxisomal targeting and overexpression of the gene led to 5-fold increase of the penicillin titer. At last, the number of peroxisomes was increased through overexpression of pexK. A strain with the double number of peroxisomes produced 2.3 times more penicillin. These results show that penicillin production can be triggered at several levels of regulation, one of which is the subcellular localization of the enzymes.
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•Peroxisomal targeting of AcvA increases penicillin production.•Overexpression of penicillin enzymes cause higher penicillin titers.•Increased numbers of peroxisomes increase the penicillin yield.
Band 3 der Geschichte des deutschen Buchhandels im 19. und 20. Jahrhundert ist der brisantesten Periode der Buchbranche gewidmet - der Zeit der NS-Diktatur. Der erste Teilband behandelt die ...Entrechtung und Vertreibung jüdischer und oppositioneller Verleger, die "Gleichschaltung" des Buchhandels und seiner Organisationen in der "Reichsschrifttumskammer", die Situation der Autoren zwischen Anpassung und innerer Emigration, die Indoktrination der Leser, aber auch die Buchgestaltung. Ein eigenes Kapitel gilt dem Zwischenbuchhandel, der sich - teilweise erfolgreich - durch Betonung des rein logistischen Charakters seiner Tätigkeit gegen den Einfluss der Politik abzuschotten suchte. Genauer untersucht werden schließlich die literarisch-belletristischen Verlage und die Wissenschaftsverlage als die beiden ökonomisch wichtigsten und wirkmächtigsten Sparten des Verlagswesens, sowie der Lexikonverlag, bei dem sich die Frage einer Anpassung an die Ideologie der neuen Machthaber mit besonderer Dringlichkeit stellte.
•Bacteriophage T7 RNA polymerase was functionally introduced into Pichia pastoris.•A novel expression vector (pEZT7) was constructed.•T7 RNA polymerase dependent gene expression was not ...observed.•HCV-IRES and PARS1 display significant promoter activity.
A novel Pichia pastoris expression vector (pEZT7) for the production of recombinant proteins employing prokaryotic bacteriophage T7 RNA polymerase (T7 RNAP) (EC 2.7.7.6) and the corresponding promoter pT7 was constructed. The gene for T7 RNAP was stably introduced into the P. pastoris chromosome 2 under control of the (endogenous) constitutive P. pastoris glyceraldehyde-3-phosphate dehydrogenase (GAP) promoter (pGAP). The gene product T7 RNAP was engineered to contain a nuclear localization signal, which directed recombinant T7 RNAP to the P. pastoris nucleus. To promote translation of uncapped T7 RNAP derived transcripts, the internal ribosomal entry site from hepatitis C virus (HCV-IRES) was inserted directly upstream of the multiple cloning site of pEZT7. A P. pastoris autonomous replicating sequence (PARS1) was integrated into pEZT7 enabling propagation and recovery of plasmids from P. pastoris. Rapid amplification of 5′ complementary DNA ends (5′ RACE) experiments employing the test plasmid pEZT7-EGFP revealed that transcripts indeed initiated at pT7. HCV-IRES mediated translation of the latter mRNAs, however, was not observed. Surprisingly, HCV-IRES and the reverse complement of PARS1 (PARS1rc) were both found to display significant promoter activity as shown by 5′ RACE.
Mullite and mullite-type crystal structures Fischer, Reinhard X.; Gaede-Köhler, Andrea; Birkenstock, Johannes ...
International journal of materials research,
04/2012, Letnik:
103, Številka:
4
Journal Article, Conference Proceeding
Recenzirano
Synthetic mullites (Al
Si
) belong to one of the most important groups of ceramic materials. Their crystal structure consists of chains of edge-sharing AlO
octahedra interconnected by tetrahedral ...double chains of
(
= Al, Si) tetrahedra. The occurrence of oxygen vacancies is associated with the formation of triclusters of
groups. The distribution of oxygen vacancies and the distribution of Al and Si on the tetrahedral sites are partially ordered yielding an incommensurately modulated crystal structure with satellite reflections in diffraction patterns. The number of symmetrically independent distribution patterns of oxygen vacancies is given for a 2 × 2 × 2 and a 3 × 3 × 2 superstructure model. Many other compounds have chain structures similar to mullite. These compounds are assigned to subgroups, all derived from a hypothetical tetragonal aristotype structure.
In Bragg–Brentano powder X‐ray diffraction, incompletely filled sample holders result in a significant loss of intensity for diffraction peaks at small 2θ angles due to shadowing of the diffracted ...beam by the sample holder. This has to be considered in crystal structure refinements for samples with diffraction peaks in the low 2θ range when shifts of sample height cannot be avoided. Herein a geometrically derived correction algorithm to account for the intensity loss as a function of shift in sample height is presented. The algorithms were verified based on a series of zeolite A diffraction patterns from samples with deliberately induced, well defined reductions in sample height.
It is pointed out that it was Frans Maurits Jaeger who was the first scientist to determine the crystal structure of a zeolite. It was the structure of nosean, which has the SOD-type framework. This ...work was the culmination of his studies of ultramarines. Conventional wisdom has it that Linus Pauling with his crystal structure determination of sodalite was first. Alas, this is not the case.
Single crystals of B
2
O
3
are needed for the precise determination of the refractive indices used to calculate the electronic polarizability
α
of 3-coordinated boron. The
α
(B) values in turn are ...used to predict mean refractive indices of borate minerals. Since the contribution of boron to the total polarizability of a mineral is very low, the synthetic compound B
2
O
3
represents an ideal model system because of its high molar content of boron. Millimeter-sized crystals were synthesized at 1 GPa in a piston-cylinder apparatus. The samples were heated above the liquidus (800 °C), subsequently cooled at 15 °C/h to 500 °C and finally quenched. The refractive indices were determined by the immersion method using a microrefractometer spindle stage. The refractive indices
n
o
= 1.653 (3) and
n
e
= 1.632 (3) correspond to a total polarizability for B
2
O
3
of
α
= 4.877 Å
3
. These values were used to determine the electronic polarizability of boron of
α
(B) = 0.16 Å
3
. Although the surface of the B
2
O
3
crystals was coated with a hydrous film immediately after being exposed to air, its bulk crystallinity is retained for a period of at least 2 months.
Genetic analyses of nuclear distribution mutants have indicated that functions of the microtubule motor, cytoplasmic dynein, and its regulators are important for nuclear positioning in filamentous ...fungi. Here we review these studies and also present the need to further dissect how dynein and its associated microtubule cytoskeleton are involved mechanistically in nuclear positioning in the multinucleated hyphae.
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