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Pawel Mierczynski Lukasz Szkudlarek Karolina Chalupka Waldemar Maniukiewicz Satriyo K. Wahono Krasimir Vasilev Malgorzata I. Szynkowska-Jozwik 《Materials》2021,14(9)
This work provides valuable information about unexplored catalytic systems tested in the transesterification reaction of vegetable oil with methanol. It was demonstrated that natural zeolite treatment leads to enhanced catalytic activity and yield of biodiesel production. The activation of the catalytic material in a mixture of 5% H2–95% Ar resulted in an improvement of the values of the TG conversion and fatty acid methyl esters (FAME) yield. In addition, it was proven that the incorporation of CaO, MgO and SrO oxides onto the natural zeolite surface improves the TG conversion and FAME yield values in the transesterification reaction. 相似文献
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The growing popularity of solution blow spinning as a method for the production of fibrous tissue engineering scaffolds and the vast range of polymer–solvent systems available for the method raises the need to study the effect of processing conditions on fiber morphology and develop a method for its qualitative assessment. Rheological approaches to determine polymer solution spinnability and image analysis approaches to describe fiber diameter and alignment have been previously proposed, although in a separate manner and mostly for the widely known, well-researched electrospinning method. In this study, a series of methods is presented to determine the processing conditions for the development of submicron fibrous scaffolds. Rheological methods are completed with extensive image analysis to determine the spinnability window for a polymer–solvent system and qualitatively establish the influence of polymer solution concentration and collector rotational speed on fiber morphology, diameter, and alignment. Process parameter selection for a tissue engineering scaffold target application is discussed, considering the varying structural properties of the native extracellular matrix of the tissue of interest. 相似文献
76.
Visualization of elongation factor G on the Escherichia coli 70S ribosome: The mechanism of translocation 总被引:9,自引:0,他引:9 下载免费PDF全文
Rajendra K. Agrawal Pawel Penczek Robert A. Grassucci Joachim Frank 《Proceedings of the National Academy of Sciences of the United States of America》1998,95(11):6134-6138
During protein synthesis, elongation factor G (EF-G) binds to the ribosome and promotes the step of translocation, a process in which tRNA moves from the A to the P site of the ribosome and the mRNA is advanced by one codon. By using three-dimensional cryo-electron microscopy, we have visualized EF-G in a ribosome–EF-G–GDP–fusidic acid complex. Fitting the crystal structure of EF-G–GDP into the cryo density map reveals a large conformational change mainly associated with domain IV, the domain that mimics the shape of the anticodon arm of the tRNA in the structurally homologous ternary complex of Phe-tRNAPhe, EF-Tu, and a GTP analog. The tip portion of this domain is found in a position that overlaps the anticodon arm of the A-site tRNA, whose position in the ribosome is known from a study of the pretranslocational complex, implying that EF-G displaces the A-site tRNA to the P site by physical interaction with the anticodon arm. 相似文献
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Breunig JJ Sarkisian MR Arellano JI Morozov YM Ayoub AE Sojitra S Wang B Flavell RA Rakic P Town T 《Proceedings of the National Academy of Sciences of the United States of America》2008,105(35):13127-13132
Primary cilia are present on mammalian neurons and glia, but their function is largely unknown. We generated conditional homozygous mutant mice for a gene we termed Stumpy. Mutants lack cilia and have conspicuous abnormalities in postnatally developing brain regions, including a hypoplasic hippocampus characterized by a primary deficiency in neural stem cells known as astrocyte-like neural precursors (ALNPs). Previous studies suggested that primary cilia mediate sonic hedgehog (Shh) signaling. Here, we find that loss of ALNP cilia leads to abrogated Shh activity, increased cell cycle exit, and morphological abnormalities in ALNPs. Processing of Gli3, a mediator of Shh signaling, is also altered in the absence of cilia. Further, key mediators of the Shh pathway localize to ALNP cilia. Thus, selective targeting of Shh machinery to primary cilia confers to ALNPs the ability to differentially respond to Shh mitogenic signals compared to neighboring cells. Our data suggest these organelles are cellular “antennae” critically required to modulate ALNP behavior. 相似文献
78.
Kolodziejski PJ Musial A Koo JS Eissa NT 《Proceedings of the National Academy of Sciences of the United States of America》2002,99(19):12315-12320
Inducible nitric oxide synthase (iNOS) is responsible for nitric oxide (NO) synthesis from l-arginine in response to inflammatory mediators. We have previously shown that iNOS is degraded through the 26S proteasome. Targeting of proteins for proteasomal degradation may or may not require their covalent linkage to multiubiquitin chains (ubiquitination). In addition, ubiquitination of a protein can serve functions other than signaling proteolysis. In this context, it is not known whether iNOS is subject to ubiquitination or whether ubiquitination is required for its degradation. In this study, we show that iNOS, expressed in HEK293 cells or induced in primary bronchial epithelial cells, A549 cells, or murine macrophages, is subject to ubiquitination. To investigate whether iNOS ubiquitination is required for its degradation, HEK293T cells were cotransfected with plasmids containing cDNAs of human iNOS and of the dominant negative ubiquitin mutant K48R. Disruption of ubiquitination by K48R ubiquitin resulted in inhibition of iNOS degradation. ts20 is a mutant cell line that contains a thermolabile ubiquitin-activating enzyme (E1) that is inactivated at elevated temperature, preventing ubiquitination. Incubation of ts20 cells, stably expressing human iNOS, at the nonpermissive temperature (40 degrees C) resulted in inhibition of iNOS degradation and marked accumulation of iNOS. These studies indicate that iNOS is subject to ubiquitination and that ubiquitination is required for its degradation. 相似文献
79.
Katarzyna Kusnierz Zdzislaw Lekston Dmytro Zhavoronkov Slawomir Mrowiec Pawel Lampe 《The Journal of surgical research》2014