The interaction between alpha-amylase and 3 flavonoid compounds from tartary buckwheat bran, namely, quercetin (Que), its monoglycoside isoquercetin (Iso), and its diglycoside rutinb (Rut), has been studied by fluorescence spectroscopy and enzymatic kinetics. The results indicate that Que, Iso, and Rut could bind with alpha-amylase to form a new complex, which exhibits an obvious fluorescence quenching. We deduce that such a quenching is a static quenching via nonradiation energy transfer. Results from plots and calculations show that the sequence of binding constants (KA) is Iso > Que > Rut. Calculation on thermodynamic parameters reveals that the main driving force of above-mentioned interaction is hydrophobic. Enzyme activity measurements show that all of the 3 flavonoid compounds are effective inhibitors toward alpha-amylase, and the inhibitory mode belongs to a competitive type. The sequence of affinity (1/Ki) is in accordance with the results of binding constants (KA) from fluorescence experiments.

No abstract

Non-photon-number-resolving single-photon-counting modules ͑SPCM's͒, also called on-off photon detectors, have been used in quantum optics for investigating the properties of various light fields based on the Hanbury-Brown-Twiss ͑HBT͒ experiment. However, for different incident light fields the experimental conditions can affect the measured photon statistics. In this paper, the second-order degree of coherence g ͑2͒ , known as the important factor for quantitying a single-photon source, is experimentally investigated by means of the HBT scheme consisting of two SPCM's. By comparing the results of coherent field with that of the thermal field, we show that the measured g ͑2͒ is affected by the photon-counting rate and the resolution time from pulsed to continuous wave fields. The proper counting rate and resolution time for characterizing the exact photon statistical properties of input fields are determined.

Abstract. We report enhanced three-dimensional degenerated Raman sideband cooling (3D DRSC) of caesium (Cs) atoms in a standard single-cell vapour-loading magneto-optical trap. Our improved scheme involves using a separate repumping laser and optimized lattice detuning. We load 1.5 × 10 7 atoms into the Raman lattice with a detuning of -15.5 GHz (to the ground F = 3 state). Enhanced 3D DRSC is used to cool them from 60 µK to 1.7 µK within 12 ms and the number of obtained atoms is about 1.2 × 10 7 . A theoretical model is proposed to simulate the measured number of trapped atoms. The result shows good agreement with the experimental data. The technique paves the way for loading a large number of ultracold Cs atoms into a crossed dipole trap and efficient evaporative cooling in a single-cell system.

No abstract