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21.
Hiroaki Nakayama Koji Nakayama Ritsuko Nakayama Yasuhiko Kato 《Archives of microbiology》1982,131(4):308-312
Hydrophobic and charge-charge interactions of Salmonella typhimirium and Serratia marcescens were determined and related to their content of fimbriae and lipopolysaccharide (LPS). The cell surface structures were characterized with hydrophobic interaction chromatography (HIC), electrostatic interaction chromatography (ESIC) and particle electrophoresis measurements. The degree of interaction at the air-water interface was tested using a monolayered lipid film applied to an aqueous surface. The cell surface hydrophobicity of S. typhimurium in the presence of fimbriae was less in smooth than in rought bacteria. Examination of a series of rough mutants of S. typhimurium indicates that reduction of the O-side chain and core oligosaccharides was correlated with increased cell hydrophobicity. The enrichment factors at the air-water interface were significantly higher for fimbriated than for non-fimbriated S. typhimurium cells. Fimbriated S. marcescens cells were less hydrophobic and adhered to a lesser degree at the air-water surface than non-fimbriated counterparts. Electrophoretic measurements and adsorption to ion exchangers gives different information about the surface charge of bacteria. The latter technique gives the interaction between localized charged surfaces.Abbreviations HIC
hydrophobic interaction chromatography
- ESIC
electrostatic interaction chromatography
- LPS
lipopolysaccharide
- PBS
phosphate buffered saline solution 相似文献
22.
(1) Current models for the mechanism of cyclic electron transport in Rhodopseudomonas sphaeroides and Rhodopseudomonas capsulata have been investigated by observing the kinetics of electron transport in the presence of inhibitors, or in photosynthetically incompetent mutant strains. (2) In addition to its well-characterized effect on the Rieske-type iron sulfur center, 5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazole (UHDBT) inhibits both cytochrome b50 and cytochrome b?90 reduction induced by flash excitation in Rps. sphaeroides and Rps. capsulata. The concentration dependency of the inhibition in the presence of antimycin (approx. 2.7 mol UHDBT/mol reaction center for 50% inhibition of extent) is very similar to that of its inhibition of the antimycin-insensitive phase of ferricytochrome c re-reduction. UHDBT did not inhibit electron transfer between the reduced primary acceptor ubiquinone (Q?I) and the secondary acceptor ubiquinone (QII) of the reaction center acceptor complex. A mutant of Rps. capsulata, strain R126, lacked both the UHDBT and antimycin-sensitive phases of cytochrome c re-reduction, and ferricytochrome b50 reduction on flash excitation. (3) In the presence of antimycin, the initial rate of cytochrome b50 reduction increased about 10-fold as the Eh(7.0) was lowered below 180 mV. A plot of the rate at the fastest point in each trace against redox potential resembles the Nernst plot for a two-electron carrier with Em(7.0) ≈ 125 ± 15 mV. Following flash excitation there was a lag of 100–500 μs before cytochrome b50 reduction began. However, there was a considerably longer lag before significant reduction of cytochrome c by the antimycin-sensitive pathway occurred. (4) The herbicide ametryne inhibited electron transfer between Q?I and QII. It was an effective inhibitor of cytochrome b50 photoreduction at Eh(7.0) 390 mV, but not at Eh(7.0) 100 mV. At the latter Eh, low concentrations of ametryne inhibited turnover after one flash in only half of the photochemical reaction centers. By analogy with the response to o-phenanthroline, it is suggested that ametryne is ineffective at inhibiting electron transfer from Q?I to the secondary acceptor ubiquinone when the latter is reduced to the semiquinone form before excitation. (5) At Eh(7.0) > 200 mV, antimycin had a marked effect on the cytochrome b50 reduction-oxidation kinetics but not on the cytochrome c and reaction center changes or the slow phase III of the electrochromic carotenoid change on a 10-ms time scale. This observation appears to rule out a mechanism in which cytochrome b50 oxidation is obligatorily and kinetically linked to the antimycin-sensitive phase of cytochrome c reduction in a reaction involving transmembrane charge transfer at high Eh values. However, at lower redox potentials, cytochrome b50 oxidation is more rapid, and may be linked to the antimycin-sensitive reduction of cytochrome c. (6) It is concluded that neither a simple linear scheme nor a simple Q-cycle model can account adequately for all the observations. Future models will have to take account of a possible heterogeneity of redox chains resulting from the two-electron gate at the level of the secondary quinone, and of the involvement of cytochrome b?90 in the rapid reactions of the cyclic electron transfer chain 相似文献
23.
Sediment pore water concentrations of Fe2+, Mn2+, NH
inf4
sup+
and CH4 were analyzed from both diver-collected cores and anin situ equilibration device (peeper) in Lake Erie's central basin. Sediment oxygen demand (SOD) was measured at the same station
with a hemispheric chamber (including DO probe and recorder) subtending a known area of sediments. The average SOD was 9.4
mM m−2 day−1 (0.3 g m−2 day−1). From pore water gradients within the near-surface zone, the chemical flux across the interface was calculated indirectly
using Fick's first law modified for sediments. These calculations, using core and peeper gradients, always showed sediment
loss to overlying waters, and variations between the two techniques differed by less than an order of magnitude for Fe2+ and CH4. The transport of these reduced constituents can represent a sizeable oxygen demand, ranging from less than 1% for Fe2+ and Mn2+ to as high as 26% for NH
inf4
sup+
, and 30% for CH4. The average flux of these constituents could account for about a third of the SOD at the sediment-water interface of this
station. 相似文献
24.
25.
The content of cytochrome c-420 in Rhodospirillum rubrum chromatophores prepared by grinding with alumina is 5–10% of that in whole cells, and 20–40% in chromatophores by ‘French’ pressing.Flash-induced phosphorylation of various chromatophores which varied in cytochrome content from 7 to 40% is proportional to the cytochrome content. Extrapolating the cytochrome c-420 content to that observed in whole cells, a ratio near 1 is calculated. At low flash intensity the phosphorylation per flash is proportional to flash energy.Photophosphorylation in flashes given after a time of several minutes is only slightly dependent on the number of flashes. If the flashes are spaced from 0.1 to 10 s, relative phosphorylation in the first flash is about 70% and in the second 90% of that observed in the following flashes. Proton binding is not affected by the cytochrome c-420 content and a ratio of of 2.3 was found.These results can be explained by a working hypothesis in which charge separation occurring at one reaction centre and the resulting electron transport mediated amongst others by c-420, results in the injection of two protons into an ATPase, this in contrast to a chemiosmotic mechanism, where the protons are released in the chromatophore inner space. 相似文献
26.
Hanna Grajek Regina Drabent Grażyna Żurkowska Czesław Bojarski 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,801(3):456-460
The electronic absorption spectra of the flavomononucleotide (FMN) in aqueous solution and in glycerine-water solution with change of the dye concentration have been measured. The FMN dimer absorption spectrum, monomer absorption spectrum, dimerization constant K and molar fraction of the monomer were calculated. It was found that FMN dimerization constants in aqueous solution were Ka = 118.0 l/mol and in glycerine Kg = 20.5 l/mol. In the region of the monomer absorption band two dimer absorption bands appear, in accordance with the Kasha molecular exciton theory. 相似文献
27.
《Bioscience, biotechnology, and biochemistry》2013,77(6):1388-1390
Two different kinds of bioprocess, ethanol fermentation and subsequent microbial esterification, were coupled using Issatchenkia terricola IFO 0933 in an interface bioreactor. The strain produced ethyl decanoate (Et-DA) by esterification of exogenous decanoic acid (DA) with ethanol produced via fermentation. The efficiency of the new coupling system depended on the concentration of glucose in a carrier and DA in an organic phase (decane) in an agar plate interface bioreactor. Optimum glucose content and DA concentration were 4% and 29 mM, respectively. 相似文献
28.
Akari Nishigaki Mihoko Maruyama Munenori Numata Chisako Kanzaki Shun‐Ichi Tanaka Hiroshi Y. Yoshikawa Masayuki Imanishi Masashi Yoshimura Yusuke Mori Kazufumi Takano 《Engineering in Life Science》2020,20(9-10):395-401
It is known that interfaces have various impacts on crystallization from a solution. Here, we describe crystallization of acetaminophen using a microflow channel, in which two liquids meet and form a liquid–liquid interface due to laminar flow, resulting in uniform mixing of solvents on the molecular scale. In the anti‐solvent method, the microflow mixing promoted the crystallization more than bulk mixing. Furthermore, increased flow rate encouraged crystal formation, and a metastable form appeared under a certain flow condition. This means that interface management by the microchannel could be a beneficial tool for crystallization and polymorph control. 相似文献
29.
Jung‐Gu Han Chihyun Hwang Su Hwan Kim Chanhyun Park Jonghak Kim Gwan Yeong Jung Kyungeun Baek Sujong Chae Seok Ju Kang Jaephil Cho Sang Kyu Kwak Hyun‐Kon Song Nam‐Soon Choi 《Liver Transplantation》2020,10(20)
High‐capacity Li‐rich layered oxide cathodes along with Si‐incorporated graphite anodes have high reversible capacity, outperforming the electrode materials used in existing commercial products. Hence, they are potential candidates for the development of high‐energy‐density lithium‐ion batteries (LIBs). However, structural degradation induced by loss of interfacial stability is a roadblock to their practical use. Here, the use of malonic acid‐decorated fullerene (MA‐C60) with superoxide dismutase activity and water scavenging capability as an electrolyte additive to overcome the structural instability of high‐capacity electrodes that hampers the battery quality is reported. Deactivation of PF5 by water scavenging leads to the long‐term stability of the interfacial structures of electrodes. Moreover, an MA‐C60‐added electrolyte deactivates the reactive oxygen species and constructs an electrochemically robust cathode‐electrolyte interface for Li‐rich cathodes. This work paves the way for new possibilities in the design of electrolyte additives by eliminating undesirable reactive substances and tuning the interfacial structures of high‐capacity electrodes in LIBs. 相似文献
30.
Shasha Zhang Zonghao Liu Wenjun Zhang Zhaoyi Jiang Weitao Chen Rui Chen Yuqian Huang Zhichun Yang Yiqiang Zhang Liyuan Han Wei Chen 《Liver Transplantation》2020,10(35)
Perovskite solar cells (PSCs) have attracted much attention in the past decade and their power conversion efficiency has been rapidly increasing to 25.2%, which is comparable with commercialized solar cells. Currently, the long‐term stability of PSCs remains as a major bottleneck impeding their future commercial applications. Beyond strengthening the perovskite layer itself and developing robust external device encapsulation/packaging technology, integration of effective barriers into PSCs has been recognized to be of equal importance to improve the whole device’s long‐term stability. These barriers can not only shield the critical perovskite layer and other functional layers from external detrimental factors such as heat, light, and H2O/O2, but also prevent the undesired ion/molecular diffusion/volatilization from perovskite. In addition, some delicate barrier designs can simultaneously improve the efficiency and stability. In this review article, the research progress on barrier designs in PSCs for improving their long‐term stability is reviewed in terms of the barrier functions, locations in PSCs, and material characteristics. Regarding specific barriers, their preparation methods, chemical/photoelectronic/mechanical properties, and their role in device stability, are further discussed. On the basis of these accumulative efforts, predictions for the further development of effective barriers in PSCs are provided at the end of this review. 相似文献