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排序方式: 共有139条查询结果,搜索用时 913 毫秒
1.
Kimia Ekramzadeh Chantal Brämer Thore Frister Jörg Fohrer Andreas Kirschning Thomas Scheper Sascha Beutel 《Biotechnology progress》2020,36(2):e2935
The patchoulol synthase (PTS) from Pogostemon cablin is a versatile sesquiterpene synthase and produces more than 20 valuable sesquiterpenes by conversion of the natural substrate farnesyl pyrophosphate (FPP). PTS has the potential to be used as a biocatalyst for the production of valuable sesquiterpenes such as (−)-patchoulol. The objective of the present study is to develop an efficient biotransformation and to characterize the biocatalytic mechanism of the PTS in detail. For this purpose, soluble PTS was prepared using an optimized cultivation protocol and continuous downstream process with a purity of 98%. The PTS biotransformation was then optimized regarding buffer composition, pH-value, and temperature for biotransformation as well as functional and kinetic properties to improve productivity. For the bioconversion of FPP, the highest enzyme activity was reached with the 2-(N-morphlino)ethanesulfonic acid (MES) buffer containing 10% (v/v) glycerol and 10 mM MgCl2 at pH 6.4 and 34°C. The PTS showed an unusual substrate inhibition for sesquiterpene synthases indicating an intermediate sesquiterpene formed in the active center. Deuteration experiments were used to gain further insights into the biocatalytic mechanism described in literature. Thus it could be shown that a second substrate binding site must be responsible for substrate inhibition and that further protonation and deprotonation steps are involved in the reaction mechanism. 相似文献
2.
Babak Sharifimajd Carl-Johan Thore Jonas Stålhand 《Biomechanics and modeling in mechanobiology》2016,15(3):497-510
Contractions of uterine smooth muscle cells consist of a chain of physiological processes. These contractions provide the required force to expel the fetus from the uterus. The inclusion of these physiological processes is, therefore, imperative when studying uterine contractions. In this study, an electro-chemo-mechanical model to replicate the excitation, activation, and contraction of uterine smooth muscle cells is developed. The presented modeling strategy enables efficient integration of knowledge about physiological processes at the cellular level to the organ level. The model is implemented in a three-dimensional finite element setting to simulate uterus contraction during labor in response to electrical discharges generated by pacemaker cells and propagated within the myometrium via gap junctions. Important clinical factors, such as uterine electrical activity and intrauterine pressure, are predicted using this simulation. The predictions are in agreement with clinically measured data reported in the literature. A parameter study is also carried out to investigate the impact of physiologically related parameters on the uterine contractility. 相似文献
3.
Cortés-Ortiz Liliana Baiz Marcella D. Hermida-Lagunes Javier García-Orduña Francisco Rangel-Negrín Ariadna Kitchen Dawn M. Bergman Thore J. Dias Pedro A. D. Canales-Espinosa Domingo 《International journal of primatology》2019,40(1):114-131
International Journal of Primatology - Interspecific hybridization allows the introgression or movement of alleles from one genome to another. While some genomic regions freely exchange alleles... 相似文献
4.
Evan T. Sloan Jacinta C. Beehner Thore J. Bergman Amy Lu Noah SnyderMackler Hans Jacquemyn 《Ecology and evolution》2022,12(3)
Nonhuman primates are an essential part of tropical biodiversity and play key roles in many ecosystem functions, processes, and services. However, the impact of climate variability on nonhuman primates, whether anthropogenic or otherwise, remains poorly understood. In this study, we utilized age‐structured matrix population models to assess the population viability and demographic variability of a population of geladas (Theropithecus gelada) in the Simien Mountains, Ethiopia with the aim of revealing any underlying climatic influences. Using data from 2008 to 2019 we calculated annual, time‐averaged, and stochastic population growth rates (λ) and investigated relationships between vital rate variability and monthly cumulative rainfall and mean temperature. Our results showed that under the prevailing environmental conditions, the population will increase (λ s = 1.021). Significant effects from rainfall and/or temperature variability were widely detected across vital rates; only the first year of infant survival and the individual years of juvenile survival were definitively unaffected. Generally, the higher temperature in the hot‐dry season led to lower survival and higher fecundity, while higher rainfall in the hot‐dry season led to increased survival and fecundity. Overall, these results provide evidence of greater effects of climate variability across a wider range of vital rates than those found in previous primate demography studies. This highlights that although primates have often shown substantial resilience to the direct effects of climate change, their vulnerability may vary with habitat type and across populations. 相似文献
5.
The Sm proteins are conserved in all three domains of life and are always associated with U-rich RNA sequences. Their proposed function is to mediate RNA-RNA interactions. We present here the crystal structures of Pyrococcus abyssi Sm protein (PA-Sm1) and its complex with a uridine heptamer. The overall structure of the protein complex, a heptameric ring with a central cavity, is similar to that proposed for the eukaryotic Sm core complex and found for other archaeal Sm proteins. RNA molecules bind to the protein at two different sites. They interact specifically inside the ring with three highly conserved residues, defining the uridine-binding pocket. In addition, nucleotides also interact on the surface formed by the N-terminal alpha-helix as well as a conserved aromatic residue in beta-strand 2 of the PA-Sm1 protein. The mutation of this conserved aromatic residue shows the importance of this second site for the discrimination between RNA sequences. Given the high structural homology between archaeal and eukaryotic Sm proteins, the PA-Sm1.RNA complex provides a model for how the small nuclear RNA contacts the Sm proteins in the Sm core. In addition, it suggests how Sm proteins might exert their function as modulators of RNA-RNA interactions. 相似文献
6.
Wojtaszewski JF Mourtzakis M Hillig T Saltin B Pilegaard H 《Biochemical and biophysical research communications》2002,298(3):309-316
During prolonged, low intensity exercise, the type of substrate utilized varies with time. If 5' AMP-activated protein kinase (AMPK) regulates muscle metabolism during exercise, signaling through AMPK would be expected to change in concordance with changes in substrate utilization. Six healthy, young males cycled (approximately 45% VO(2peak)) until exhaustion (approximately 3.5h). During exercise, leg glucose uptake and rate of glycogenolysis gradually decreased whereas free fatty acid uptake gradually increased. In the thigh muscle, the alpha AMPK subunits became progressively more phosphorylated on Thr(172) during exercise eliciting a parallel increase in alpha2 but not alpha1 AMPK activity. In contrast, after 1h of exercise, Ser(221) phosphorylation of acetyl-CoA carboxylase-beta (ACCbeta) peaked at 1h of exercise and returned to resting levels at exhaustion. Protein expression of alpha2 AMPK, alpha1 AMPK or ACCbeta did not change with time. These data suggest that AMPK signaling is not a key regulatory system of muscle substrate combustion during prolonged exercise and that marked activation of AMPK via phosphorylation is not sufficient to maintain an elevated ACCbeta Ser(221) phosphorylation during prolonged exercise. 相似文献
7.
Jia-Yee S. Yap Thore Rohner Abigail Greenfield Marlien Van Der Merwe Hannah McPherson Wendy Glenn Geoff Kornfeld Elessa Marendy Annie Y. H. Pan Alan Wilton Marc R. Wilkins Maurizio Rossetto Sven K. Delaney 《PloS one》2015,10(6)
The Wollemi pine (Wollemia nobilis) is a rare Southern conifer with striking morphological similarity to fossil pines. A small population of W. nobilis was discovered in 1994 in a remote canyon system in the Wollemi National Park (near Sydney, Australia). This population contains fewer than 100 individuals and is critically endangered. Previous genetic studies of the Wollemi pine have investigated its evolutionary relationship with other pines in the family Araucariaceae, and have suggested that the Wollemi pine genome contains little or no variation. However, these studies were performed prior to the widespread use of genome sequencing, and their conclusions were based on a limited fraction of the Wollemi pine genome. In this study, we address this problem by determining the entire sequence of the W. nobilis chloroplast genome. A detailed analysis of the structure of the genome is presented, and the evolution of the genome is inferred by comparison with the chloroplast sequences of other members of the Araucariaceae and the related family Podocarpaceae. Pairwise alignments of whole genome sequences, and the presence of unique pseudogenes, gene duplications and insertions in W. nobilis and Araucariaceae, indicate that the W. nobilis chloroplast genome is most similar to that of its sister taxon Agathis. However, the W. nobilis genome contains an unusually high number of repetitive sequences, and these could be used in future studies to investigate and conserve any remnant genetic diversity in the Wollemi pine. 相似文献
8.
9.
Nowadays a growing demand for green chemicals and cleantech solutions is motivating the industry to strive for biobased building
blocks. We have identified the tertiary carbon atom-containing 2-hydroxyisobutyric acid (2-HIBA) as an interesting building
block for polymer synthesis. Starting from this carboxylic acid, practically all compounds possessing the isobutane structure
are accessible by simple chemical conversions, e. g. the commodity methacrylic acid as well as isobutylene glycol and oxide.
During recent years, biotechnological routes to 2-HIBA acid have been proposed and significant progress in elucidating the
underlying biochemistry has been made. Besides biohydrolysis and biooxidation, now a bioisomerization reaction can be employed,
converting the common metabolite 3-hydroxybutyric acid to 2-HIBA by a novel cobalamin-dependent CoA-carbonyl mutase. The latter
reaction has recently been discovered in the course of elucidating the degradation pathway of the groundwater pollutant methyl
tert -butyl ether (MTBE) in the new bacterial species Aquincola tertiaricarbonis. This discovery opens the ground for developing a completely biotechnological process for producing 2-HIBA. The mutase enzyme
has to be active in a suitable biological system producing 3-hydroxybutyryl-CoA, which is the precursor of the well-known
bacterial bioplastic polyhydroxybutyrate (PHB). This connection to the PHB metabolism is a great advantage as its underlying
biochemistry and physiology is well understood and can easily be adopted towards producing 2-HIBA. This review highlights
the potential of these discoveries for a large-scale 2-HIBA biosynthesis from renewable carbon, replacing conventional chemistry
as synthesis route and petrochemicals as carbon source. 相似文献
10.
Carbon Conversion Efficiency and Limits of Productive Bacterial Degradation of Methyl tert-Butyl Ether and Related Compounds 下载免费PDF全文
The utilization of the fuel oxygenate methyl tert-butyl ether (MTBE) and related compounds by microorganisms was investigated in a mainly theoretical study based on the YATP concept. Experiments were conducted to derive realistic maintenance coefficients and Ks values needed to calculate substrate fluxes available for biomass production. Aerobic substrate conversion and biomass synthesis were calculated for different putative pathways. The results suggest that MTBE is an effective heterotrophic substrate that can sustain growth yields of up to 0.87 g g−1, which contradicts previous calculation results (N. Fortin et al., Environ. Microbiol. 3:407-416, 2001). Sufficient energy equivalents were generated in several of the potential assimilatory routes to incorporate carbon into biomass without the necessity to dissimilate additional substrate, efficient energy transduction provided. However, when a growth-related kinetic model was included, the limits of productive degradation became obvious. Depending on the maintenance coefficient ms and its associated biomass decay term b, growth-associated carbon conversion became strongly dependent on substrate fluxes. Due to slow degradation kinetics, the calculations predicted relatively high threshold concentrations, Smin, below which growth would not further be supported. Smin strongly depended on the maximum growth rate μmax, and b and was directly correlated with the half maximum rate-associated substrate concentration Ks, meaning that any effect impacting this parameter would also change Smin. The primary metabolic step, catalyzing the cleavage of the ether bond in MTBE, is likely to control the substrate flux in various strains. In addition, deficits in oxygen as an external factor and in reduction equivalents as a cellular variable in this reaction should further increase Ks and Smin for MTBE. 相似文献