Study on the resonance light scattering spectrum of berberine-cetyltrimethylammonium bromide system and the determination of nucleic acids at nanogram levels

The interaction of berberine with nucleic acid in the presence of cetyltrimethylammonium bromide (CTMAB) in aqueous solution has been studied by spectrophotometry and resonance light scattering (RLS) spectroscopy. At pH 7.30, the RLS signals of berberine were greatly enhanced by nucleic acid in the region of 300-600 nm characterized by four peaks at 324.0, 386.5, 416.5 and 465.0 nm. The binding properties were examined by using a Scatchard plot based on the measurement of enhanced RLS data at 416.5 nm. Under optimum conditions, the increase of RLS intensity of this system at 416.5 nm is proportional to the concentration of nucleic acid. The linear range is 7.5 x 10(-9)-7.5 x 10(-5) g ml(-1) for calf thymus DNA, 7.5 x 10(-9)-2.5 x 10(-5) g ml(-1) for herring sperm DNA, and 5.0 x 10(-9)-2.5 x 10(-5) g ml(-1) for yeast RNA. The detection limits (S/N = 3) are 2.1 ng ml(-1) for calf thymus DNA, 6.5 ng ml(-1) for herring sperm DNA and 3.5 ng ml(-1) for yeast RNA, respectively. Three synthetic samples were analyzed satisfactorily.     

Sensitive Determination of Carbohydrates by Fluorimetric Method with Ce(IV) and Sodium Triphosphate

A new simple and sensitive fluorimetric method for the determination of carbohydrates is described. The method is based on the reaction between carbohydrates and Ce(IV) in the presence of sulfuric acid. All the reductive carbohydrates can be detected indirectly by the fluorescence of Ce(III) produced. The addition of sodium triphate enhances the sensitivity of the method by more than 10-folds. Under optimum conditions, an excellent linear relationship was obtained between the fluorescence intensity and the concentration of carbohydrates. The limits of detection lie in the range of 9.3 x 10(-10) - 1.3 x 10(-9) mol/L. As compared to the normal fluorimetric method, the proposed method is faster and more sensitive.     

On the bound of the Lyapunov exponents for continuous systems

In this paper, both upper bounds and lower bounds for all the Lyapunov exponents of continuous differential systems are determined. Several examples are given to show the application of the estimates derived here.     

Study of the Reaction Between the Nucleic Acid and Y-BPMPHD-CTMAB Complex and Its Analytical Application

The fluorescence quenching of the Y-BPMPHD-CTMAB by nucleic acids is reported. It is considered that the Y-BPMPHD-CTMAB can form a large complex with nucleic acid through the electrostatic attraction in the pH range of 4.2-6.8. Under optimal conditions, the difference of fluorescence intensity between the system without and with nucleic acids is proportional to the concentration of nucleic acids over the range of 4.5 x 10(-8)-1.2 x 10(-5) g/mL for fsDNA and 3.2 x 10(-8)-3.0 x 10(-5) g/mL for yRNA, respectively. The detection limits are 14.0 ng/mL for fsDNA and 21.0 ng/mL for yRNA. The method is applied for the determination of nucleic acids in actual sample, and the result obtained is satisfactory.     

Some recent developments in the chemical synthesis of inorganic nanotubes

Inorganic nanotubes have been a subject of intensive research in the past decade. We recently developed a number of synthetic strategies for generating nanotubes from inorganic materials that do not have a layered structure. It is the intention of this contribution to provide a brief account of these research activities.     

Measurement of the total cross section for hadronic production by e(+)e(-) annihilation at energies between 2.6-5 GeV

Using the upgraded Beijing Spectrometer, we have measured the total cross section for e(+)e(-) annihilation into hadronic final states at center-of-mass energies of 2.6, 3.2, 3.4, 3.55, 4.6, and 5.0 GeV. Values of R, sigma(e(+)e(-)-->hadrons)/sigma(e(+)e(-)-->&mgr;(+)&mgr;(-)), are determined.     

Characterization of Annealed, Proton Exchange Optical Waveguides in Y-cut MgO∶LiNbO3 Crystal

It is reported the results of a systematic study on planar waveguides fabricated in Y-cut MgO∶LiNbO3 crystal. The index profile of the as-exchanged waveguide can be modeled as a step-like one. It is deduced the diffusion coefficient and the activation energy for the proton exchange process. The surface index increases Δne of around 0.127 after proton exchange can be reduced by post thermal annealing. The effects of the annealing on the index profile and guide depth were found not as fast as it does on a pure LiNbO3 crystal.     

Sensitivity enhancement of HCACO by using an HMQC magnetization transfer scheme

Previous theoretical calculations have demonstrated that the multiquantum relaxation rate of (1)H(alpha)-(13)C(alpha)(R(MQ)) is, on average, 1.3 +/- 0.4 or 1.7 +/- 0.6 times slower than the single-quantum relaxation rate of (13)C(alpha)(R(C)) for a sample with or without, respectively, amide protons. By taking advantage of this fact and by using the PEP sensitivity enhancement scheme, an HMQC version of the HCACO experiment has been developed. We demonstrate that this new experiment is 23 and 55% more sensitive than the original HSQC version of the HCACO experiment, at constant times of 7 and 27 ms, respectively, for a sample of the BC domain of the ciliary neurotrophic factor receptor protein dissolved in D(2)O at 20 degrees C.     

Direct mass measurements of short-lived A=2Z-1 nuclides (63)Ge, (65)As, (67)Se, and (71)Kr and their impact on nucleosynthesis in the rp process

Mass excesses of short-lived A=2Z-1 nuclei (63)Ge, (65)As, (67)Se, and (71)Kr have been directly measured to be -46,921(37), -46,937(85), -46,580(67), and -46,320(141) keV, respectively. The deduced proton separation energy of -90(85) keV for (65)As shows that this nucleus is only slightly proton unbound. X-ray burst model calculations with the new mass excess of (65)As suggest that the majority of the reaction flow passes through (64)Ge via proton capture, indicating that (64)Ge is not a significant rp-process waiting point.