Chen Dieyan

Quantum dot-labeled trichosanthin

Semiconductor quantum dots have been used for the first time to label trichosanthin. The absorption and fluorescent spectra of quantum dot-labeled trichosanthin were different from those of trichosanthin, but no changes were found in the enzymatic activity of quantum dot-labeled trichosanthin in comparison with trichosanthin. The distribution of quantum dot-labeled trichosanthin in the cytoplasm of a human choriocarcinoma cell is observed with two-photon laser scanning microscopy, and the aggregation of quantum dot-labeled trichosanthin in the cytoplasm is discussed.

Trichosanthin induced calcium-dependent generation of reactive oxygen species in human choriocarcinoma cells

The type-I ribosome-inactivating protein trichosanthin (TCS) has a broad spectrum of biological and pharmacological activities, including abortifacient, anti-tumor and anti-HIV. We found for the first time that TCS induced the generation of reactive oxygen species (ROS) in human choriocarcinoma cells (JAR cells) at the level of the single cell by using the fluorescent probe 2′,7′-dichlorofluorescein diacetate with confocal laser scanning microscopy. TCS-induced ROS formation was shown to be dependent on the presence of extracellular Ca2+ and was further reduced when cytosolic Ca2+ was chelated by BAPTA-AM. The production of ROS increased rapidly after the application of TCS, which paralleled TCS-induced increase in intracellular calcium monitored using fluo 3-AM. Simultaneous observation of the nuclear morphological changes via two-photon laser scanning microscopy and production of ROS via confocal laser scanning microscopy revealed that ROS were involved in the apoptosis of JAR cells. The contribution of ROS was confirmed by experiments in which the antioxidant α-tocopherol prevented TCS-induced ROS formation and cell death. The finding that TCS induced calcium-dependent generation of ROS in JAR cells and that ROS were involved in the apoptosis of JAR cells might provide new insight into the anti-tumor and anti-HIV mechanism of TCS.

STUDY OF HIGH-LYING EXCITED STATES OF RARE-EARTH ELEMENT Dy BY LASER RESONANCE IONIZATION SPECTROSCOPY

This paper describes the investigation of high-excited states of Dy, which includes the measurement of high Rydberg states and autoionizing states, by means of laser resonance ionization spectroscopy (LRIS). Two high Rydberg series (n> 40), 4f10(5I8) 6sns and 4f10(5I8) 6snd, have been obtained by exciting the state of 4f10(5I8) 6s6p (3P20)5I80 using two-step laser excitation-electric field ionization method. With the data obtained, we determined the first ionization potential of Dy. It is 47901.7 ± 0.6 cm-1, that is, about one order more accurate than the results given in the literature. Using the same technique, we found 97 autoionizing states by exciting the state of 4f95d6s (7H70).

Autoionizing Process of the Double Rydberg State

Using five-laser resonance excitation and double time-of-flight spectroscopy, the double Rydberg states N Lnl (N ≤ 66;n ≤ 85;L, l < 4) of Ca have been obtained. The distribution of Ca+ Rydberg states, which is from the autoionization of the double Rydberg state has been measured. A novel result has been observed.

NEW AUTOIONIZING STATES NEAR THE FIRST IONIZATION LIMIT OF RARE EARTH ELEMENT Dy

This paper describes the investigation of autoionizing states near the first ionization limit of rare-earth element Dy. The 62, 51, 97 and 25 new autoionizing states resulting from the states of 4f10(5I8)6s6p(3P20) 3I70, 4f9(6H0)5d2(3F) (8G0)6s9G70, 4f9(6F0)5d6s2 7H70 and 4f95d6s2 7K70, respectively, were found by using a laser resonance ionization time-of-flight mass spectrometer (LRI-TOFMS). The photoionization efficiencies for different channels were compared with each other. In addition, the Shore-Fano parameters of autoionizing states were determined by a nonlinear fitting program.