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81.
Peled D Daube SS Naaman R 《Langmuir : the ACS journal of surfaces and colloids》2008,24(20):11842-11846
The adsorption of DNA on surfaces is a widespread procedure and is a common way for fabrication of biosensors, DNA chips, and nanoelectronic devices. Although the biologically relevant and prevailing in vivo structure of DNA is its double-stranded (dsDNA) conformation, the characterization of DNA on surfaces has mainly focused on single-stranded DNA (ssDNA). Studying the structure of dsDNA on surfaces is of invaluable importance to microarray performance since their effectiveness relies on the ability of two DNA molecules to hybridize and remain stable. In addition, many of the enzymatic transactions performed on DNA require dsDNA, rather than ssDNA, as a substrate. However, it is not established that adsorbed dsDNA remains in its structure and does not denature. Here, two methodologies have been developed for distinguishing between surface-adsorbed single- and double-stranded DNA. We demonstrate that, upon formation of a dense monolayer, the nonthiolated strand comprising the dsDNA is released and the monolayer consists of mostly ssDNA. The fraction of dsDNA within the ssDNA monolayer depends on the length of the oligomers. A likely mechanism leading to this rearrangement is discussed. 相似文献
82.
Structure Elucidation of a Complex Faldaprevir‐(±)‐α‐Tocopherol Addition Product Reveals Reactivity of Common Excipient Vitamin E‐TPGS
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Nina C. Gonnella Shirley A. Rodriguez Scott Pennino Daniel Norwood 《Journal of heterocyclic chemistry》2016,53(6):1878-1891
Vitamin E‐TPGS (d ‐α‐tocopheryl polyethylene glycol succinate) is a common excipient used in drug formulations. This excipient is formed by esterification of Vitamin E succinate with polyethylene glycol. As part of an oral formulation for active pharmaceutical ingredient (API) Faldaprevir, Vitamin E‐TPGS was found to decompose under ambient conditions producing free (±)‐α‐Tocopherol which subsequently formed an adduct composed of α‐Tocopherol and the API. The addition product was isolated using liquid chromatography with collections onto solid‐phase extraction cartridges, and full structure elucidation was achieved using mass spectrometry and nuclear magnetic resonance spectroscopy. The results revealed a regioselective addition of α‐Tocopherol to the API that likely occurs through the formation of a stabilized ortho‐quinone methide intermediate. This finding demonstrates the propensity of the common excipient (Vitamin E‐TPGS) to generate chemically active intermediates that may react with formulation ingredients. 相似文献
83.
Let \({\Omega}\) be a Lipschitz bounded domain of \({\mathbb{R}^N}\), \({N\geq2}\), and let \({u_p\in W_0^{1,p}(\Omega)}\) denote the p-torsion function of \({\Omega}\), p > 1. It is observed that the value 1 for the Cheeger constant \({h(\Omega)}\) is threshold with respect to the asymptotic behavior of up, as \({p\rightarrow 1^+}\), in the following sense: when \({h(\Omega) > 1}\), one has \({\lim_{p\rightarrow 1^+}\left\|u_{p}\right\| _{L^\infty(\Omega)}=0}\), and when \({h(\Omega) < 1}\), one has \({\lim_{p\rightarrow 1^+}\left\|u_p\right\| _{L^\infty(\Omega)}=\infty}\). In the case \({h(\Omega)=1}\), it is proved that \({\limsup_{p\rightarrow1^+}\left\|u_p\right\|_{L^\infty(\Omega)}<\infty}\). For a radial annulus \({\Omega_{a,b}}\), with inner radius a and outer radius b, it is proved that \({\lim_{p\rightarrow 1^+}\left\|u_p\right\| _{L^\infty(\Omega_{a,b})}=0}\) when \({h(\Omega_{a,b})=1}\). 相似文献
84.
85.
Sizing large proteins and protein complexes by electrospray ionization mass spectrometry and ion mobility 总被引:1,自引:0,他引:1
Kaddis CS Lomeli SH Yin S Berhane B Apostol MI Kickhoefer VA Rome LH Loo JA 《Journal of the American Society for Mass Spectrometry》2007,18(7):1206-1216
Mass spectrometry (MS) and ion mobility with electrospray ionization (ESI) have the capability to measure and detect large noncovalent protein-ligand and protein-protein complexes. Using an ion mobility method of gas-phase electrophoretic mobility molecular analysis (GEMMA), protein particles representing a range of sizes can be separated by their electrophoretic mobility in air. Highly charged particles produced from a protein complex solution using electrospray can be manipulated to produce singly charged ions, which can be separated and quantified by their electrophoretic mobility. Results from ESI-GEMMA analysis from our laboratory and others were compared with other experimental and theoretically determined parameters, such as molecular mass and cryoelectron microscopy and X-ray crystal structure dimensions. There is a strong correlation between the electrophoretic mobility diameter determined from GEMMA analysis and the molecular mass for protein complexes up to 12 MDa, including the 93 kDa enolase dimer, the 480 kDa ferritin 24-mer complex, the 4.6 MDa cowpea chlorotic mottle virus (CCMV), and the 9 MDa MVP-vault assembly. ESI-GEMMA is used to differentiate a number of similarly sized vault complexes that are composed of different N-terminal protein tags on the MVP subunit. The average effective density of the proteins and protein complexes studied was 0.6 g/cm(3). Moreover, there is evidence that proteins and protein complexes collapse or become more compact in the gas phase in the absence of water. 相似文献
86.
Shukoor MI Natalio F Tahir MN Ksenofontov V Therese HA Theato P Schröder HC Müller WE Tremel W 《Chemical communications (Cambridge, England)》2007,(44):4677-4679
Polymer coated superparamagnetic gamma-Fe(2)O(3) nanoparticles were derivatized with a synthetic double-stranded RNA [poly(IC)], a known allosteric activator of the latent (2-5)A synthetase, to separate a single 35 kDa protein from a crude extract which cross reacted with antibodies raised against the sponge enzyme. 相似文献
87.
The new ternary compound ThTe2I2, which crystallizes in the NbS2Cl2 structure type, was prepared from the elements and characterized by single‐crystal X‐ray diffraction. It adopts a monoclinic layer structure where binuclear [Th2(Te2)2]4+ units with square‐antiprismatically coordinated thorium are linked together by I– anions to form sheets parallel to the (001) plane. The space group is C2/m and the lattice constants are a = 7.642(1) Å, b = 14.336(4) Å, c = 7.727(2) Å, and β = 111.27(2)° for Z = 4. The final R1/wR2 for the crystal structure refinement was 0.029/0.073. 相似文献
88.
89.
90.
Volkmar Derstroff Jürgen Ensling Vadim Ksenofontov Philipp Gütlich Wolfgang Tremel 《无机化学与普通化学杂志》2002,628(6):1346-1354
A new chromium thiophosphate, K3Cr2(PS4)3 has been prepared and characterized by single‐crystal diffraction, temperature dependent magnetic susceptibility measurements and optical spectroscopy. K3Cr2(PS4)3 crystallizes in the monoclinic space group P21/n (No. 14) with a = 9.731(2) Å, b = 11.986(2) Å, c = 17.727(4) Å, β = 96.52(2)°, V = 2054.2(2) Å3, Z = 4, and R = 0.044. The anionic part of the structure consists of dimeric Cr2(μ3‐S3PS)2 units which are linked by bidentate PS4 groups to form infinite one‐dimensional [S2PS2Cr2(μ3S3PS)2]3— chains separated by K+ cations. The CrIII centers of the Cr2(μ3‐S3PS)2 units are antiferromagnetically coupled. The magnetic susceptibility data may be fitted using a D‐Heisenberg model for S = 3/2 with g = 2.02 and J/k = 10K. K3Cr2(PS4)3 is semiconducting with an optical band gap of 1.35 eV. 相似文献