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241.
Self-assembling DNA tiling lattices represent a versatile system for nanoscale construction. Self-assembled DNA arrays provide an excellent template for spatially positioning other molecules with increased relative precision and programmability. Here we report an experiment using a linear array of DNA triple crossover tiles to controllably template the self-assembly of single-layer or double-layer linear arrays of streptavidin molecules and streptavidin-conjugated nanogold particles through biotin-streptavidin interaction. The organization of streptavidin and its conjugated gold nanoparticles into periodic arrays was visualized by atomic force microscopy and scanning electron microscopy. 相似文献
242.
Ke Jian Liu Jin Jie Jiang Li Li Ji Xianglin Shi Harold M. Swartz 《Research on Chemical Intermediates》1996,22(5):499-509
Application of the spin trapping technique in intact animals requires an understanding of the stability and distribution of the spin traps and their spin adducts in vivo. We studied the stability of DMPO in vivo in mice using HPLC and the stability of spin adducts of DMPO by EPR in plasma, whole blood, peritoneal fluid, and homogenized heart tissue of the rat. At 15 minutes after intraperitoneal injection DMPO had similar concentrations in the liver, heart, and blood of the mice and 40% remained in the organs 2 hours after the injection. In contrast, the spin adduct DMPO-OH was short lived, with a half-life of 3.0 minutes in plasma, and was not detectable 1 minute after formation in whole blood and homogenized heart tissue. The carbon centered spin adduct DMPO-CH(OH)CH3 was more stable, having half-lives of 16, 11, 3.6, and 0.79 minutes in plasma, peritoneal fluid, whole blood, and homogenized heart tissue, respectively. The spin adduct DMPO-SO3 was sufficiently stable for the adduct to be observed directly from living mice. 相似文献
243.
Hulin Li Boyan Zhang Lin Ma Liliu Wu James Q. Chambers 《Transition Metal Chemistry》1995,20(6):552-556
Summary The spectrochemical, electrochemical and electrocatalytic properties of Co[15]aneN4 ([15]aneN4 = 1,4,8,12-tetraazacyclopentadecane) have been investigated. The results show that, in aqueous solution, this compound mainly exists as three species whose axial coordination positions are occupied by water and/or hydroxy ligands; it is marginal whether other substrates such as Cl– and NO
inf3
sup–
interact with the central ion in acid-base solutions. The approximate Pourbaix diagram of CoIII/II[15]ane N4 was determined. There is an electrochemically-induced isomerization between two trans conformational isomers of the Co[15]aneN4 complexes in acid and netural solutions. The Co[15]aneN4 complex has electrocatalytic properties for reduction of nitrate and nitrite only in strong alkaline solution. 相似文献
244.
In this work a portable microfluidic device with a reusable integrated high voltage power supply is presented, which allows for quick exchange of inexpensive disposable poly(dimethylsiloxane)(PDMS) microfluidic chips on a carrier only slightly larger than a microscope slide. The device is powered by an onboard MN21 cell battery (5 mm radius, 30 mm long) and is demonstrated through the rapid and controlled transport of a fluorescent dye through an expansion chamber geometry. Power consumption experiments demonstrate the device's ability to complete over 40 dispense-flushing cycles on a single battery. 相似文献
245.
The structures and energies of the noble gas containing anions FNgO- (Ng = He, Ar, and Kr) have been calculated by high-level ab initio calculations. The FNgO- anions were found to be deep-energy minima at the singlet electronic state, and their energies are significantly lower than those at the triplet state. High dissociation energy barriers to Ng + OF- were also predicted. The unexpected stability of the FNgO- was due to the dramatic ion-induced O=Ng bond formation. The calculated results suggested possible experimental identification of the anionic species and even some related "ionic compounds" under cryogenic conditions. 相似文献
246.
Five different pure density functional theory (DFT) and hybrid Hartree-Fock/DFT methods have been used to search for the molecular structures, thermochemistry, and electron affinities of the bromine hydrogen fluorides HBrF(n)/HBrF(n)(-) (n = 2, 4). The basis sets used in this work are of double-zeta plus polarization quality in conjunction with s- and p-type diffuse functions, labeled as DZP++. Structures with Br-F and Br-H normal bonds, that is, HBrF(2)/HBrF(2)(-) with C(2v) or C(s) symmetry and HBrF(4)/HBrF(4)(-) with C(4v) or C(s) symmetry, are genuine minima. However, unlike the original BrF(3) and BrF(5) molecules, the global minima for HBrF(n)/HBrF(n)(-) (n = 2, 4) species are predicted to be complexes, some of which contain hydrogen bonds. The demise of the hypervalent structures is due to the availability of favorable dissociation products involving HF, which has a much larger dissociation energy than F(2). Similar reasoning suggests that PF(4)H, SF(3)H, SF(5)H, ClF(2)H, ClF(4)H, AsF(4)H, SeF(3)H, and SeF(5)H will all be hydrogen bond structures incorporating diatomic HF. The most reasonable theoretical values of the adiabatic electron affinities (EA(ad)) are 3.69 (HBrF(2)) and 4.38 eV (HBrF(4)) with the BHLYP method. These electron affinities are comparable to those of the analogous molecules: Br(2)F(n), ClBrF(n), and BrF(n)(+1) systems. The first F-atom dissociation energies for the neutral global minima are 60 (HBrF(2)) and 49 kcal/mol (HBrF(4)) with the B3LYP method. The first H-atom dissociation energies for the same systems are 109 (HBrF(2)) and 116 kcal/mol (HBrF(4)). The large Br-H bond energies are not sufficient to render the hypervalent structures energetically tenable. The dissociation energies for the complexes to their fragments are relatively small. 相似文献
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