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Human Nudt16 (hNudt16) is a member of the Nudix family of hydrolases, comprising enzymes catabolizing various substrates including canonical (d) NTPs, oxidized (d) NTPs, nonnucleoside polyphosphates, and capped mRNAs. Decapping ac...
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Human Nudt16 (hNudt16) is a member of the Nudix family of hydrolases, comprising enzymes catabolizing various substrates including canonical (d) NTPs, oxidized (d) NTPs, nonnucleoside polyphosphates, and capped mRNAs. Decapping activity of the Xenopus laevis (X29) Nudt16 homolog was observed in the nucleolus, with a high specificity toward U8 snoRNA. Subsequent studies have reported cytoplasmic localization of mammalian Nudt16 with cap hydrolysis activity initiating RNA turnover, similar to Dcp2. The present study focuses on hNudt16 and its hydrolytic activity toward dinucleotide cap analogs and short capped oligonucleotides. We performed a screening assay for potential dinucleotide and oligonucleotide substrates for hNudt16. Our data indicate that dinucleotide cap analogs and capped oligonucleotides containing guanine base in the first transcribed nucleotide are more susceptible to enzymatic digestion by hNudt16 than their counterparts containing adenine. Furthermore, unmethylated dinucleotides (GpppG and ApppG) and respective oligonucleotides (GpppG-16nt and GpppA-16nt) were hydrolyzed by hNudt16 with greater efficiency than were m7GpppG and m7GpppG-16nt. In conclusion, we found that hNudt16 hydrolysis of dinucleotide cap analogs and short capped oligonucleotides displayed a broader spectrum specificity than is currently known.
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This Letter discusses the role of key physical and chemical effects in the emergence of pattern formation in microtubule assemblies in vitro under the influence of gravity. The roles of chemical kinetics, diffusion, gravitational ...
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This Letter discusses the role of key physical and chemical effects in the emergence of pattern formation in microtubule assemblies in vitro under the influence of gravity. The roles of chemical kinetics, diffusion, gravitational drift and electrostatic interactions affected by thermal fluctuations are discussed. The subtle interplay of these factors leads to the observed self-organization phenomena exhibiting the features of a typical polar liquid crystal phase. (c) 2005 Elsevier B.V. All rights reserved.
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Silver nanoparticles have gained worldwide attention in the scientific community due to their high antimicrobial activity. However, they tend to agglomerate and lose their shape and properties, thus capping agents necessary to pro...
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Silver nanoparticles have gained worldwide attention in the scientific community due to their high antimicrobial activity. However, they tend to agglomerate and lose their shape and properties, thus capping agents necessary to protect their shapes, sizes, and properties. To enhance their antimicrobial activity, this research aimed to cap silver nanoparticles with cellulosic matrices from wheat straws. The wheat straw was delignified with 6% HNO_3, and the residual was treated with 1% NaOH and NaCIO: CH_3COOH (1:1), then used to synthesize cellulose nanocrystals via acid hydrolysis. AgNPs were incorporated into the CPC and CNCs by in-situ synthesis using NaHB_4 as the reducing agent. Fourier Transform Infrared, Scanning Electron Microscopy, and X-ray diffraction were used to investigate their features. The findings exhibited crystallinity increased with subsequent treatments, according to XRD analysis. Ultraviolet-visible, FTIR, TEM, and XRD analysis confirmed the capping of AgNPs onto the cellulosic materials. Antibacterial activity against Staphylococcus aureus and Escherlchia coli, with CNCs-AgNPs composite, exhibited higher activity compared to CPC-AgNPs composite due to the increased surface area and excellent binding on the surface of the composite.
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The kinetics of the hydrolysis of P 1-(7-methylguanosinyl-5) P 3-(guanosinyl-5) triphosphate (m 7GpppG), P 1-(7-methylguanosinyl-5) P 4-(guanosinyl-5) tetraphosphate (m 7GppppG), and diadenosine 5, 5-P 1,P 3 -triphosphate (ApppA) ...
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The kinetics of the hydrolysis of P 1-(7-methylguanosinyl-5) P 3-(guanosinyl-5) triphosphate (m 7GpppG), P 1-(7-methylguanosinyl-5) P 4-(guanosinyl-5) tetraphosphate (m 7GppppG), and diadenosine 5, 5-P 1,P 3 -triphosphate (ApppA) in the presence of several Cu 2+ or Zn 2+ ions complexed with bi- or terpyridine has been studied at pH 8.0 and 60C. Time-dependent product distributions at various metal complex concentrations have been determined by capillary zone electrophoresis and reversed-phase high performance liquid chromatography. The results show that the predominant hydrolytic reaction is the cleavage of 5,5-oligophosphate bridge, with Cu 2+ complexes being approximately 15-fold more efficient catalysts than Zn 2+ chelates. In addition, the effect of metal ions complexes at pH 7.0 and 8.0 on the imidazole ring opening in m 7Gua mononucleotides has been studied. The influence of Cu 2+ complexes on imidazole ring cleavage of mononucleotides is modest, whereas Zn 2+ complexes are almost inactive.
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In this work, the selective synthesis of pure cadmium telluride (CdTe) quantum dots and cadmium telluride and cadmium sulfide (CdTe:CdS) nanocomposites was accomplished. The thiol capping agent played a dual role in the preparatio...
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In this work, the selective synthesis of pure cadmium telluride (CdTe) quantum dots and cadmium telluride and cadmium sulfide (CdTe:CdS) nanocomposites was accomplished. The thiol capping agent played a dual role in the preparation of CdTe and CdTe:CdS nanocomposites. Thioglycolic acid acted as a capping agent at the starting stage of the refluxing process and also acted as a sulfur source in the fabrication of CdTe:CdS nanocomposite through partial hydrolysis at longer refluxing time. The fluorescence quantum yield of the CdTe quantum dots was significantly increased in the preparation of CdTe:CdS nanocomposites. The maximum quantum yield by CdTe:CdS nanocomposites was achieved as 47% for a refluxing time of 58 h. The structural studies revealed the formation of CdTe:CdS nanocomposites at longer refluxing time. The homogeneous size distribution of the CdTe:CdS nanocomposites was confirmed by high resolution transmission electron microscopic studies. The optical studies clearly demonstrated the formation of CdTe:CdS nanocomposites through partial hydrolysis of capping agent with the extended refluxing time. The size dependent energy transfer of the CdTe quantum dots was studied by the absorption and emission characteristics.
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In vitro motility assays are commonly used to study the mechanisms regulating the activity of motor proteins. Transport properties of active biofilaments in these systems are examined. A dynamics depending on surface concentration...
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In vitro motility assays are commonly used to study the mechanisms regulating the activity of motor proteins. Transport properties of active biofilaments in these systems are examined. A dynamics depending on surface concentration of biological motors is proposed in order to model gliding of individual filaments. Statistical analysis leads to purely diffusive dynamic laws. The presence of polymerization processes altering the length of fibres induces a breakdown of the central-limit theorem and leads to anomalous diffusion. [References: 25]
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Background: The labile nature of microtubules is critical for establishing cellular morphology and motility, yet the molecular basis of assembly remains unclear. Here we use optical tweezers to track microtubule polymerization aga...
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Background: The labile nature of microtubules is critical for establishing cellular morphology and motility, yet the molecular basis of assembly remains unclear. Here we use optical tweezers to track microtubule polymerization against microfabricated barriers, permitting unprecedented spatial resolution. Results: We find that microtubules exhibit extensive nanometer-scale variability in growth rate and often undergo shortening excursions, in some cases exceeding five tubulin layers, during periods of overall net growth. This result indicates that the guanosine triphosphate (GTP) cap does not exist as a single layer as previously proposed. We also find that length increments (over 100 ms time intervals, n = 16,762) are small, 0.81 +/- 6.60 nm (mean +/- standard deviation), and very rarely exceed 16 nm (about two dimer lengths), indicating that assembly occurs almost exclusively via single-subunit addition rather than via oligomers as was recently suggested. Finally, the assembly rate depends only weakly on load, with the average growth rate decreasing only 2-fold as the force increases 7-fold from 0.4 pN to 2.8 pN. Conclusions: The data are consistent with a mechanochemical model in which a spatially extended GTP cap allows substantial shortening on the nanoscale, while still preventing complete catastrophe in most cases.
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A microtubule of a given length undergoes all possible scenarios of transitions between growing and shrinking phases, so-called microtubule dynamic instability. In this Paper we utilize a minimal two-state model proposed by Kill [...
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A microtubule of a given length undergoes all possible scenarios of transitions between growing and shrinking phases, so-called microtubule dynamic instability. In this Paper we utilize a minimal two-state model proposed by Kill [Proc. Natl. Acad. Sci. USA 81, 6728 (1984)] that is equivalent to a two-state random walk. Using a technique for classifying discrete random walk configurations by introducing a counting variable in evolution equations, we have derived expressions for probability densities (which contain information about all transition histories) of phase transitions before the complete disappearance of a microtubule. As a result, the mean lifetime of a microtubule turns out to be equal to the total lifetime of growing and shrinking phases times the average number of transitions. An attractive feature of this simple model is that elementary formulas relating statistical averages to rate parameters are obtained. [S1063-651X(99)02001-2]. [References: 19]
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The catalytic hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) by metallomicelle composed of analogous Cu(11) complex in CTAB micellar solution was investigated at 30 degrees C and different pH. The results indicate that the anal...
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The catalytic hydrolysis of bis(p-nitrophenyl) phosphate (BNPP) by metallomicelle composed of analogous Cu(11) complex in CTAB micellar solution was investigated at 30 degrees C and different pH. The results indicate that the analogous complex with 1:2 ratio of ligand to metal ion in CATB micellar solution is the active species for catalyzing the hydrolysis of BNPP. The ternary complex kinetic model for metallomicellar catalysis was employed to obtain the relative kinetic and thermodynamic parameters for taking apart the mechanism of the catalytic hydrolysis of BNPP. (c) 2006 Elsevier B.V. All rights reserved.
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An ABA triblock copolymer of polyvinyl acetate-b-polystyrene-b-polyvinyl acetate (PVAc-PS-PVAc) was successfully synthesized with a binary system composed of polystyrene with N,N-dimethylaniline end groups (PS_(da)) and benzopheno...
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An ABA triblock copolymer of polyvinyl acetate-b-polystyrene-b-polyvinyl acetate (PVAc-PS-PVAc) was successfully synthesized with a binary system composed of polystyrene with N,N-dimethylaniline end groups (PS_(da)) and benzophenone to initiate the polymerization of vinyl acetate under UV irradiation. The PS_(da) was obtained by capping the living polystyrene macrodianion with p-(dimethylamino) benzaldehyde in excess. The PVA-PS-PVA could then be obtained by hydrolysis of PVAc-PS-PVAc in the sodium ethoxide benzene solution. The intermediates and desirable copolymers were characterized by GPC, IR, and ~1H-NMR in detail.
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