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71.
An optimization procedure for the gallic acid-persulphate method for the ultratrace determination of vanadium is reported. The optimization step has improved the sensitivity by a factor of three. The linearity range of the calibration graph is also extended. 相似文献
72.
Accurate quantification of deoxyribonucleic acid (DNA) is critical for many analyses in molecular biology and genetic tests. We present a method in which the stoichiometrically existing phosphorus content in purified genomic DNA is quantitatively converted into orthophosphate ions by microwave assisted-UV digestion in the presence of microlitre quantities of dilute reagents (HCl, HNO(3), H(2)O(2)). The tandem use of microwave energy and ultraviolet photons for DNA digestion in pressurized quartz vessels enables a maximum reaction temperature of 240 °C resulting in efficient and fast mineralization of high molecular weight DNA within 30 minutes. Compared to hotplate digestion, the digestion time is reduced by a factor of 32. The MW-UV sample preparation approach coupled with the ion chromatographic measurement of phosphate using a high performance (HP) methodology provides an accurate quantitation of phosphorus mass fractions as low as 0.3 μg g(-1), corresponding to a DNA mass of 25 μg. The relative expanded uncertainties (% U) expressed at 95% confidence for these analyses range from 0.2 to 0.6%. Critically, the matrix of the calibrant solution is also matched with respect to the digested matrix anions (chloride, nitrate), without which significant bias in IC performance is observed. The phosphorus content of the calf thymus DNA was also measured using high-performance inductively coupled plasma optical emission spectroscopy (HP-ICP-OES), which provided independent data for comparison with the MW-UV digestion-IC based approach. Ion chromatography requires smaller volume of materials to perform the analysis and could be useful for characterizing primary calibration standards and certified reference materials with low uncertainties. 相似文献
73.
Ponnusamy Sami Natarajan Mariselvi Kandasamy Venkateshwari Murugesan Vairalakshmi Arunachalam Sarathi Kasi Rajasekaran 《Transition Metal Chemistry》2010,35(5):563-570
The kinetics of reduction of heteropoly 11-tungstovanadophosphate, [PVVW11O40]4−, (HPA1) and heteropoly 10-tungstodivanadophosphate, [PVVVVW10O40]5−, (HPA2) by thiourea has been investigated in HClO4/phthalate/acetate buffer solutions spectrophotometrically at 25 °C in aqueous medium. The stoichiometry of the reaction is
1:1 in both cases. The HPAs are converted into the corresponding one-electron reduced heteropoly blues, namely, [PVIVW11O40]5− and [PVIVVVW10O40]6−, and thiourea is oxidised to formamidine disulphide. The reaction shows first-order dependence in both [HPA] and [thiourea]
at constant pH. The rate–pH profile shows the participation of both the neutral and deprotonated forms of thiourea in the
reaction. The reaction proceeds through an outer sphere electron transfer mechanism in which activation-controlled electron
transfer is the rate-determining step. Self-exchange rate constants for the couples [PVVW11O40]4−/[PVIVW11O40]5−, [PVVVVW10O40]5−/[PVIVVVW10O40]6− and H2NCSNH2/H2NCS·+NH2 have been evaluated by Marcus theory. 相似文献
74.
Magnetic field induced exciton binding energy is investigated in a strained InAs/GaAs quantum wire within the framework of single band effective mass approximation. The strain contribution to the potential is determined through deformation potentials. The interband emission energy of strained InAs/GaAs wire is investigated in the influence of magnetic field with the various structural parameters. Magnetic field induced photoionization cross section of the exciton is studied. The total optical absorption and the refractive index changes as a function of normalized photon energy between the ground and the first excited state in the presence of magnetic field are analyzed. The optical absorption coefficients and the refractive index changes strongly depend on the incident optical intensity and the magnetic field. The occurred blueshift of the resonant peak due to the magnetic field will give the information about the variation of two energy levels in the quantum well wire. The optical absorption coefficients and the refractive index changes are strongly dependent on the incident optical intensity and the magnetic field. 相似文献
75.
Synthesis of a novel cryptand with an indole moiety in its architecture is described. Crystal structures of this newly synthesized cryptand and its trialdehyde precursor have been investigated. In the case of the cryptand molecule, a discrete cyclic S6-symmetric hexameric methanol cluster sandwiched between the hydrophobic ends of two cryptand units was characterized crystallographically. Moreover, a hexameric cyclic chair conformation composed of methanol and secondary nitrogen atoms from the cryptand skeleton was also identified. 相似文献
76.
An unidirectional orientation of all six arms of an arene based hexapodal amide receptor shows dimeric capsular assembly templated by a [F(4)(H(2)O)(10)](4-) cluster. 相似文献
77.
78.
Mercaptothiazolinyl functionalized hexapodal (L(1)) and tripodal (L(2)) receptors on the benzene platform have been synthesized easily in good yields and structurally characterized by a single-crystal X-ray crystallographic study. In the solid state, L(1) shows an orientation of six arms in 1,3,5 vs 2,4,6 facial steric gearing fashion, whereas L(2) adopted C(2v) symmetry where two of its thiazolinyl arms are oriented in one direction and the third arm in the another direction. Two silver complexes of L(1), 1 ([2(L(1))·6(AgClO(4))·2(CHCl(3))·HClO(4)]) and 2 ([2(L(1))·6(AgClO(4))]), that are suitable for single-crystal X-ray studies are isolated upon the slow diffusion of a dimethylformamide solution of AgClO(4) to the solution of L(1) in chloroform and dichloromethane, respectively. Similarly, upon the slow diffusion of an acetonitrile solution of AgClO(4) to the chloroform solution of L(2), colorless crystals of the silver complex of L(2), 3, are successfully isolated. The structural analyses of 1 and 2 show the formation of a silver ion assisted hexanuclear metallocage Ag(6)(L(1))(2) via dimeric assembly of L(1) with multiple clefts and pockets toward guests binding. In 1, two chloroform molecules sit in top and bottom pockets, whereas six perchlorate counteranions are bound in six clefts between the silver ion pillared side arms of the metallocage. Though complex 2 shows the formation of a metallocage like 1, the single crystal structural analysis depicts perchlorate counteranions bonded to the silver atoms of the metallocage. On the contrary, the silver complex of tripodal receptor L(2), 3, shows the formation of a metallo-organic polymeric network of L(2) and Ag(+). To the best of our knowledge, this work represents the first report on the formation of an M(6)L(2) type metallosupramolecular cage topology with multiple clefts for guest binding by a semirigid hexapodal receptor. 相似文献
79.
Kumar RS Paul P Riyasdeen A Wagniéres G van den Bergh H Akbarsha MA Arunachalam S 《Colloids and surfaces. B, Biointerfaces》2011,86(1):35-44
The characteristics of the binding reaction of surfactant-cobalt(III) complex, cis-[Co(phen)?(C??H??NH?)]Cl?·3H?O (phen=1,10-phenanthroline, C??H??NH?=tetradecylamine) with human serum albumin (HSA) were studied by fluorescence and UV-vis absorption spectroscopy. In addition, the effect of the surfactant-cobalt(III) complex on the conformation of HSA was analysed using synchronous fluorescence spectroscopy. The experimental results showed that surfactant-cobalt(III) complex caused the fluorescence quenching of HSA through a combination of static and dynamic quenching. The number of binding sites (n) and apparent binding constant (K(a)) of surfactant-cobalt(III) complex (above and below the critical micelle concentration (cmc) were determined at various temperatures. According to the thermodynamic parameters, it is likely that hydrophobic interactions are involved in the binding process. The cancer chemotherapeutic potential of surfactant-cobalt(III) complex on ME-180 cervical cancer cell was determined using MTT assay and specific staining techniques. The complex affected the viability of the cells significantly and the cells succumbed through an apoptosis process as seen in the nuclear morphology and cytoplasmic features. In addition, single-cell electrophoresis indicated DNA damage. 相似文献
80.
The Fourier transform Raman and Fourier transform infrared spectra for minoxidil have been recorded in the region 4000—100 cm?1 and 4000—450 cm?1, respectively. The structural and spectroscopy data of the molecule in the ground state were calculated by using density functional theory methods with 6-311G (d, p) basis set. A detailed vibrational analysis of the title compound has been done using normal coordinate analysis following the scaled quantum mechanical force field methodology. The calculated molecular geometry parameters and scaled vibrational wavenumbers are well compared with the experimental data. The electronic properties, such as excitation energies, absorption wavelength, highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) energies were performed by time-dependent density functional theory approach, and the results are in good agreement with experimental absorption spectrum. The charge delocalizations of these molecules have been analyzed using natural bond orbital analysis. The molecule orbital contributions are studied by density of energy states. Fukui functions, local softness, and electrophilicity indices for selected atomic sites of the title compound are determined. Finally, the thermal behaviors of the compound have been calculated by different temperature. 相似文献