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1.
KL Britton HF Rogers Y Asano T Dairi Y Kato TJ Stillman DW Rice 《Acta crystallographica. Section D, Biological crystallography》1998,53(4):124-126
The novel NAD+-linked opine dehydrogenase from a soil isolate Arthrobacter sp. strain 1C belongs to an enzyme superfamily whose members exhibit quite diverse substrate specificites. Crystals of this opine dehydrogenase, obtained in the presence or absence of co-factor and substrates, have been shown to diffract to beyond 1.8 ? resolution. X-ray precession photographs have established that the crystals belong to space group P21212, with cell parameters a = 104.9, b = 80.0, c = 45.5 ? and a single subunit in the asymmetric unit. The elucidation of the three-dimensional structure of this enzyme will provide a structural framework for this novel class of dehydrogenases to enable a comparison to be made with other enzyme families and also as the basis for mutagenesis experiments directed towards the production of natural and synthetic opine-type compounds containing two chiral centres. 相似文献
2.
The liquid crystal (LC) alignment properties of LC cells fabricated with films of 2-naphthoxymethyl-substituted polystyrenes with different contents of naphthoxymethyl side groups were investigated. The polymer films exhibited good optical transparency in the visible light region (400–700 nm). The LC cells made from the unrubbed films of polymers having more than 57 mol%?of 2-naphthoxymethyl containing monomeric units showed homeotropic LC alignment with a high pretilt angle of about 90o. Good electro-optical characteristics, such as the threshold voltage, response time, voltage holding ratio and residual DC voltage were observed for the LC cells fabricated with the polymer having 100 mol%?of 2-naphthoxymethyl containing monomeric units as an LC alignment layer. 相似文献
3.
Ganesh Shenoy Jessica Ettedgui Chandrasekhar Mushti Jennifer Hong Kelly Lane Burchelle Blackman Hak-Sung Jung Yasuharu Takagi Yeonee Seol Martin Brechbiel Rolf E. Swenson Keir C. Neuman 《Molecules (Basel, Switzerland)》2022,27(3)
Carboxylic acid is a commonly utilized functional group for covalent surface conjugation of carbon nanoparticles that is typically generated by acid oxidation. However, acid oxidation generates additional oxygen containing groups, including epoxides, ketones, aldehydes, lactones, and alcohols. We present a method to specifically enrich the carboxylic acid content on fluorescent nanodiamond (FND) surfaces. Lithium aluminum hydride is used to reduce oxygen containing surface groups to alcohols. The alcohols are then converted to carboxylic acids through a rhodium (II) acetate catalyzed carbene insertion reaction with tert–butyl diazoacetate and subsequent ester cleavage with trifluoroacetic acid. This carboxylic acid enrichment process significantly enhanced nanodiamond homogeneity and improved the efficiency of functionalizing the FND surface. Biotin functionalized fluorescent nanodiamonds were demonstrated to be robust and stable single-molecule fluorescence and optical trapping probes. 相似文献
4.
Jong Seol Yuk Colette McDonagh Brian D. MacCraith 《Analytical and bioanalytical chemistry》2010,398(5):1947-1954
The technique of surface plasmon-coupled emission (SPCE) involves the coupling of light which is emitted from a fluorophore
into the surface plasmon of an adjacent thin metal film, giving rise to highly directional emission. We have combined the
advantages of SPCE with the high light collection efficiency of supercritical angle fluorescence by carrying out an immunoassay
on a paraboloid array biochip in the absence of the conventional SPCE spacer layer normally used to minimize metal quenching
of the fluorescence. In this work, we have successfully demonstrated an SPCE-based assay by utilizing the protein assay layer
as the spacer layer. A novel 3 × 3 injection molded polymer biochip with paraboloid elements was used. The paraboloid elements
served to enhance the light collection efficiency while the top surface was coated with a gold layer to use excitation of
surface plasmons and detection of SPCE emission. Theoretical modeling of the gold-protein layer structure showed that the
surface plasmon resonance angles were located in the detection range of the paraboloid biochip. The polarization dependence
of SPCE emission was also demonstrated. Finally, a human IgG sandwich immunoassay was carried out which exhibited a limit
of detection of ~10 ng/ml using 3σ. The results demonstrate the potential of the SPCE-based paraboloid array biochip as a novel platform for high-throughput
analysis of biomolecular interactions. 相似文献
5.
Quinto-Hernandez A Wodtke AM Bennett CJ Kim YS Kaiser RI 《The journal of physical chemistry. A》2011,115(3):250-264
Methyl azide (CH(3)N(3)) might be a potential precursor in the synthesis of prebiotic molecules via nonequilibrium reactions on interstellar ices initiated by energetic galactic cosmic rays (GCR) and photons. Here, we investigate the effects of energetic electrons as formed in the track of cosmic ray particles and 193 nm photons with solid methyl azide at 10 K and the inherent formation of methanimine (CH(2)NH), hydrogen cyanide (HCN), and hydrogen isocyanide (HNC). We present a systematic kinetic study and outline feasible reaction pathways to these molecules. These processes might be also important in solar system analogue ices. 相似文献
6.
Yeon SH Seol J Park Y Koh DY Kang YS Lee H 《Journal of the American Chemical Society》2008,130(29):9208-9209
A hydrogen molecule entrapped in the cages of icy hydrogen hydrate is confined in host water framework and thus behaves unlike pure solid or liquid hydrogen. The gamma-irradiated hydrogen radicals are for the first time observed from ESR and solid-state MAS 1H NMR spectra to stably exist in the icy hydrate channels without any collapse of the host framework, confirming the chemical shift consistency of ionized hydrogen derivatives. We discuss the confined icy hydrate channels, which can act as potential storage sites for simultaneously imprisoning both molecular and ionized hydrogen and further as icy nanoreactors. 相似文献
7.
We first report here that under strong surrounding gas of external CH4 guest molecules the sII and sH methane hydrates are structurally transformed to the crystalline framework of sI, leading to a favorable change of the lattice dimension of the host-guest networks. The high power decoupling 13C NMR and Raman spectroscopies were used to identify structure transitions of the mixed CH4 + C2H6 hydrates (sII) and hydrocarbons (methylcyclohexane, isopentane) + CH4 hydrates (sH). The present findings might be expected to provide rational evidences regarding the preponderant occurrence of naturally occurring sI methane hydrates in marine sediments. More importantly, we note that the unique and cage-specific swapping pattern of multiguests is expected to provide a new insight for better understanding the inclusion phenomena of clathrate materials. 相似文献
8.
9.
Woongchul Shin Seongmin Park Hyeyoon Ro Dong-Yeun Koh Jiwoong Seol Huen Lee 《The Journal of chemical thermodynamics》2012,44(1):20-25
We suggest two types of new amine-type sII formers: pyrrolidine and piperidine. These guest compounds fail to form clathrate hydrate structures with host water, but instead have to combine with light gaseous guest molecules (methane) for enclathration. First, two binary clathrate hydrates of (pyrrolidine + methane) and (piperidine + methane) were synthesized at various amine concentrations. 13C NMR and Raman analysis were done to identify the clathrate hydrate structure and guest distribution over sII-S and sII-L cages. XRD was also used to find the exact structure and corresponding cell parameters. At a dilute pyrrolidine concentration of less than 5.56 mol%, the tuning phenomenon is observed such that methane molecules surprisingly occupy sII-L cages. At the critical guest concentration of about 0.1 mol%, the cage occupancy ratio reaches the maximum of approximately 0.5. At very dilute guest concentration below 0.1 mol%, the methane molecules fail to occupy large cages on account of their rarefied distribution in the network. Direct-release experiments were performed to determine the actual guest compositions in the clathrate hydrate phases. Finally, we measured the clathrate hydrate phase equilibria of (pyrrolidine + methane) and (piperidine + methane). 相似文献
10.
Wetting and dewetting transitions play a central role in controlling the hydrophobicity of the lining of biological channels in order to regulate aqueous solution permeation. Understanding of the operational characteristics of biological nanochannels led to experimental efforts to mimic their behavior and to achieve potential-induced, repeatedly-switchable wettability transitions in synthetic nanochannels in the early 2010s. Since then, research has identified conditions needed to produce reversible wettability transitions using a number of different environmental stimuli—such as light, pH, and electrostatic charge—in addition to potential. Furthermore, nascent understanding of the underlying phenomena in synthetic nanochannels was rapidly followed by practical applications, including oil–water separations, drug release, and electroactive flow control based on switchable wettability. More practical applications are being developed continuously, as the physical and chemical principles that govern hydrophobic gating at the nanoscale are further elucidated, making it possible to exploit wettability as a design element in nanofluidic systems. 相似文献