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61.
62.
Narges Abdali Farhan Younas Samaneh Mafakheri Karunakar R. Pothula Ulrich Kleinekathöfer Andreas Tauch Roland Benz 《BMC biochemistry》2018,19(1):3
Background
Corynebacterium urealyticum, a pathogenic, multidrug resistant member of the mycolata, is known as causative agent of urinary tract infections although it is a bacterium of the skin flora. This pathogenic bacterium shares with the mycolata the property of having an unusual cell envelope composition and architecture, typical for the genus Corynebacterium. The cell wall of members of the mycolata contains channel-forming proteins for the uptake of solutes.Results
In this study, we provide novel information on the identification and characterization of a pore-forming protein in the cell wall of C. urealyticum DSM 7109. Detergent extracts of whole C. urealyticum cultures formed in lipid bilayer membranes slightly cation-selective pores with a single-channel conductance of 1.75 nS in 1 M KCl. Experiments with different salts and non-electrolytes suggested that the cell wall pore of C. urealyticum is wide and water-filled and has a diameter of about 1.8 nm. Molecular modelling and dynamics has been performed to obtain a model of the pore. For the search of the gene coding for the cell wall pore of C. urealyticum we looked in the known genome of C. urealyticum for a similar chromosomal localization of the porin gene to known porH and porA genes of other Corynebacterium strains. Three genes are located between the genes coding for GroEL2 and polyphosphate kinase (PKK2). Two of the genes (cur_1714 and cur_1715) were expressed in different constructs in C. glutamicum ΔporAΔporH and in porin-deficient BL21 DE3 Omp8 E. coli strains. The results suggested that the gene cur_1714 codes alone for the cell wall channel. The cell wall porin of C. urealyticum termed PorACur was purified to homogeneity using different biochemical methods and had an apparent molecular mass of about 4 kDa on tricine-containing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE).Conclusions
Biophysical characterization of the purified protein (PorACur) suggested indeed that cur_1714 is the gene coding for the pore-forming protein in C. urealyticum because the protein formed in lipid bilayer experiments the same pores as the detergent extract of whole cells. The study is the first report of a cell wall channel in the pathogenic C. urealyticum.63.
Noha Said Bedowr Rosiyah Binti Yahya Nesrain Farhan 《Journal of Saudi Chemical Society》2018,22(3):255-260
This paper presents synthesis, structural characterization and spintronic applications of copper (II) tetradecanoate derived magnetic complexes. The complexes were prepared by a chemical reaction between [Cu2(CH3(CH2)12COO)4](EtOH)2 and 2,2′-bipyridine-4,4′-bipyridine ligands respectively. The complexes were further reacted between the product of the first reaction and 4,4′-bipyridine-2,2′-bipyridine respectively. The structural characterization techniques included elemental analysis, Fourier transformed infrared spectroscopy (FTIR), Ultra-violet–Visible (UV–Vis) spectroscopy, polarized optical microscopy, magnetic moment and thermogravimetric analysis. The structural and characterization results suggested that the synthesized complexes were binuclear and mononuclear covalent complexes of copper(II) with structural formulas [Cu2(η2-(OOCR)4](4,4′-bpy)2H2O] and [Cu(η1-(OOCR)2(2,2′-bpy) (4,4′-bpy)] respectively. 相似文献
64.
Dr. Yevheniia Smortsova Dr. Clément Falaise Anam Fatima Dr. Minh-Huong Ha-Thi Prof. Rachel Méallet-Renault Dr. Karine Steenkeste Dr. Serge Al-Bacha Dr. Tesnim Chaib Dr. Loïc Assaud Dr. Marc Lepeltier Dr. Mohamed Haouas Dr. Nathalie Leclerc Dr. Thomas Pino Prof. Emmanuel Cadot 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):17094-17103
Polyoxothiometalate ions (ThioPOM) are active hydrogen-evolution reaction (HER) catalysts based on modular assembly built from electrophilic clusters {MoSx} and vacant polyoxotungstates. Herein, the dumbbell-like anion [{(PW11O39)Mo3S4(H2O)3(OH)}2]8− exhibits very high light-driven HER activity, while the active cores {Mo3S4} do not contain any exposed disulfido ligands, which were suspected to be the origin of the HER activity. Moreover, in the catalyst architecture, the two central {Mo3S4} cores are sandwiched by two {PW11O39}7− subunits that act as oxidant-resistant protecting groups and behave as electron-collecting units. A detailed photophysical study was carried out confirming the reductive quenching mechanism of the photosensitizer [Ir(ppy)2(dtbbpy)]+ by the sacrificial donor triethanolamine (TEOA) and highlighting the very high rate constant of the electron transfer from the reduced photosensitizer to the ThioPOM catalyst. Such results provide new insights into the field of molecular catalytic systems able to promote high HER activity. 相似文献
65.
66.
We determine the optimal way to enclose volume in a class of domains inside certain Friedmann–Robertson–Walker metrics. The method employed is an adaptation of the Bray–Morgan isoperimetric comparison procedure to the Lorentzian setting. We also make some remarks on isoperimetric comparison in the Riemannian setting, for rotationally-symmetric space-like slices in non-vacuum space-times. 相似文献
67.
Srinivasa Reddy Mothe Jacqueline S. J. Tan Lohitha R. Chennamaneni Farhan Aidil Yi Su Hway C. Kang Freda C. H. Lim Praveen Thoniyot 《Journal of polymer science. Part A, Polymer chemistry》2020,58(12):1728-1738
Radical ring-opening polymerization (rROP) reaction of cyclic ketene acetals (CKA) is an interesting route to biodegradable polymers. Contrary to their tremendous potential, fundamental understanding of their reaction kinetics and thermodynamics is still limited. We present experimental and theoretical investigations for rROP reactions of CKA to systematically elucidate the effects of monomer ring sizes on the homopolymerization. We aim to provide insights on the structural-reactivity relationship of CKA by studying the thermodynamics and kinetics of the forward ring-opening propagation reactions and key side reactions, namely ring-retained propagation and radical back-biting reaction leading to branching. Experimental results show that for the CKA with smaller ring sizes, significant amount of ring-retained side products are formed when up to 90% of the monomers are converted. However, for the larger ring sizes (7 and 8 membered), almost complete ring-opening polymerization with <1% of ring-retained products are formed. Density functional theory (DFT) calculations show that kinetic effects from the collision frequency dominate in differentiating between ring-opening propagation, ring-retained propagation, and backbiting. The results corroborate well with experiments and reports in the literature. Our systematic study from the first principle and experimental validation provide insights into CKA rROP to apply radical polymerization to generate biodegradable polymers. 相似文献
68.
We investigate the interaction of a standing-wave light field with the beam of two-level atoms moving in the Bragg regime.
The atomic beam consists of two different isotopes and the density is sufficiently small so that at most one atom is inside
the cavity at any time. The experimental setup is such that both the isotopes have the same momenta. The momentum transfer
between the atoms and photons in the process essentially effects the center-of-mass motion of the atoms, thus separating the
isotopes in different directions after specific interaction times. 相似文献
69.
Nazish Khan Akhtar Nadhman Sadiq Azam Inam Ullah Farhan Ahmad 《Green Chemistry Letters and Reviews》2020,13(2):69-82
ABSTRACT The current study aims to assess the aqueous extract of Pinus wallichiana stem for the synthesis of small spherical-shaped (10–30?nm) silver nanoparticles (AgNPs) and their in-vitro and in-vivo biomedical applications. The biosynthesized AgNPs were nonmutagenic and safe at all test doses as per Ames and acute toxicity assay (20, 40, 60, and 80?mg/kg). The percent writhing inhibitory effect generated by AgNPs was 42.51, 50.84, and 59.06 at test doses of 10, 20, and 30?mg/kg, respectively. The percent decreased in gastrointestinal tract motility observed was 41.34%, 32.69%, and 28.48% at 10, 20, and 30?mg/kg, respectively. They also showed a significant antipyretic effect after 1, 2, and 3?h in comparison to normal saline. The AgNPs of P. wallichiana showed good antibacterial activity against Acinetobacter baumannii (60% with MIC50?=?2.36?mg/ml and MBC?=?5.0?mg/ml). These nanoparticles also possessed good antioxidant activity of 61.77?±?0.828% and 70.25?±?0.56% at 400 and 500?µg/ml, respectively and lack phytoagglutinin potential. Because of their high potency as biomedical agents, these nanoparticles can be a good alternative to the currently available drugs and approaches. 相似文献
70.
R. K. Itawi S. M. Al-Jobori M. Jalil S. S. Farhan A. Mheemeed Kh. Saaeed E. Ahmed 《Journal of Radioanalytical and Nuclear Chemistry》1991,149(2):333-337
Eleven food colouring substances are analyzed for their elemental content by the method of instrumental neutron activation analysis, and the concentrations of fourteen elements present in these samples are presented. 相似文献