THE PHOTOPHYSICAL PROPERTIES OF PORPHYCENES: POTENTIAL PHOTODYNAMIC THERAPY AGENTS*

Porphycene and a tetra-n-propyl derivative remained unaltered on irradiation in toluene at room temperature. Quantum yields of fluorescence, S T intersystem crossing, and singlet molecular oxygen sensitization, as well as lifetimes of the singlet and triplet excited states were measured. In view of their structural relationship to porphyrin, their high absorption above 620 nm, their stability towards photooxidation, and their high quantum yields of fluorescence and singlet oxygen sensitization, these compounds qualify as potential agents for tumor marking and photodynamic therapy.     

LOCAL ELECTRIC FIELD EFFECT ON THE CHLOROPHYLL FLUORESCENCE

Abstract. Polarized absorption and fluorescence of chlorophyll a and bacteriochlorophyll solutions in nematic liquid crystal mixtures have been studied in the presence of an external electric field.
The electric field caused a reorientation of the pigment molecules as concluded from changes in the polarized absorption. However, no correlation was found between the change in the polarized absorption and the change in the polarized fluorescence as a function of the field strength. The field influence was much stronger than expected only from the molecular orientation. The fluorescence polarized parallel to the direction of the liquid crystal was found to increase, whereas the similarly polarized absorption decreases. As a whole, the fluorescence yield significantly increased. It is suggested that the additional electric field is reinforced by a local field, most probably due to a protonation of the liquid crystal molecules.
Charged solvent molecules are reoriented in an external electric field which changes the local electric field acting on chlorophylls. Similar changes in CHI fluorescence yield due to local electric field can be created in vivo by the shift of charged molecules present in surrounding pigments. Such effects can be at least partially responsible for slow induction of fluorescence phenomena.     

BORONIC ACIDS AS MECHANISTIC PROBES FOR THE BACTERIAL LUCIFERASE REACTION

Bacterial luciferase uses long chain aldehydes as substrates. Alkylboronic acid analogs of these substrates with chain lengths of C₇ and C₉ have been synthesized, characterized, and used as mechanistic probes for the light emitting reaction. They behave as inhibitors in the in vitro luminescence reaction. Contrary to an earlier report (Macheroux and Ghisla, 1985, Nachr. Chem. Tech. Lab. 33,785–790) they are not substrates for bacterial luciferase, in that they do not lead to light emission and are not oxidized by the flavin-4a-hydroperoxide to the products boric acid and the corresponding alcohol, as would be expected from a Baeyer-Villiger reaction. However, the particular conformation of a putative boronic acid hydroperoxide at the active center might be such that it would preclude a Baeyer-Villiger fragmentation. Thus, while the results do not support the postulate that luciferase proceeds via a Baeyer-Villiger mechanism, they also do not exclude it. A further observation was that the endogenous light emission (no added aldehyde) decays more rapidly than does the luciferase bound flavin-4a-hydroperoxide. This suggests that the endogenous light is not caused by the decomposition of the flavin-4a-hydroperoxide.     

TURNING-OVER OF THE ELECTRIC DIPOLE IN A POLYMER*

The transition from the biexciton to the exciton can turn over the direction of the electric dipole of a polymericmolecule. This turning-over action combined with the photoinduced polarization reversion can be used as a switch. Theswitching speed is governed by the relaxation time of the turning-over process, which can be determined by a dynamicalsimulation.     

THE EFFECT OF A PERMANENT ELECTRIC FIELD ON THERMOLUMINESCENCE OF CHLOROPLASTS

Abstract— The effect of a permanent electric field on the thermoluminescence (TL) of pea chloroplasts was studied. The field was applied to suspensions at lowtemperatures(–15 to -40_oC) and to dry films of various humidity. A permanent electric field increased TL at low temperatures at the expense of the peaks above OA_oC. When the field strength was high, an increase in the quantum yield could be observed. When a field was applied at -15_OC, the band around +10_oC was reduced preferentially, but when a field was applied at – 40_AoC, TL bands emitted above OA_oC decreased to a similar extent. Analogies between the behaviour of solid suspensions and dry films of various humidity, and the isotope effect with D₂O, indicated that the efficiency and mode of action of an electric field on TL depends on the conformational mobility of the microsurroundings of the traps in the membrane.     

TRANSITIONAL FIELD BEHAVIOUR FOR THE MATUYAMA-BRUNHES

Paleomagnetic study from Tongjing basalts, Shandong Province, China, provides a record of the transitional field behaviour for the Matuyama-Brunhes. Based on the record the transitional field configurations are studied. The reasons that make the virtual geomagnetic pole (VGP) at the low latitude are researched.     

THE USE OF EXOGENOUS FLUORESCENT PROBES FOR TEMPERATURE MEASUREMENTS IN SINGLE LIVING CELLS

The fluorescent membrane probes 7-nitrobenz-2-oxa-1,3-diazo1-4-y1 (NBD) and 6-dodeca-noy1-2-dimethylamino-naphthalene (laurdan) have been studied for use as optical thermometers in living cells. The thermal sensitivity of NBD is primarily a consequence of rapid, heat-induced electronic changes, which increase the observed fluorescence decay rate. As a result, fluorescence intensity and lifetime variations of membrane-bound NBD-conjugated phospholipids and fatty acids can be directly correlated with cellular temperature. In contrast, laurdan fluorescence undergoes a dramatic temperature-dependent Stokes shift as the membrane undergoes a gel-to-liquid-crystalline phase transition. This facilitates the use of fluorescence spectra to record the indirect effect of microenvironmental changes, which occur during bilayer heating. Microscope and suspension measurements of cells and phospholipid vesicles are compared for both probes using steady-state and fluorescence lifetime (suspension only) data. Our results show that NBD fluorescence lifetime recordings can provide reasonable temperature resolution (approximately 2°C) over a broad temperature range. Laurdan's microenvironmental sensitivity permits better temperature resolution (0.1-1°C) at the expense of a more limited dynamic range that is determined solely by bilayer properties. The temperature sensitivity of NBD is based on rapid intramolecular rotations and vibrations, while laurdan relies on a slower, multistep mechanism involving bilayer rearrangement, water penetration and intermolecular processes. Because of these differences in time scale, NBD appears to be more suitable for monitoring ultrafast phenomena, such as the impact of short-pulse microirradiation on single cells.     

芘四硫酸四钠盐/甲基紫精复合物光物理性质的研究

本文通过吸收光谱滴定和时间分辨瞬态吸收光谱对芘四硫酸四钠盐(pyrenetetrasulfonic acid tetrasodium salt,PyTS)/甲基紫精(methylviologen,MV²⁺)复合物在水溶液中的光物理性质进行研究。用甲基紫精滴定芘四硫酸四钠盐时,得到该复合物的组成成份是1:1,反之,用芘四硫酸四钠盐滴定甲基紫精时,同样得到1:1组成成份的复合物。该复合物的形成常数是2.4×10⁶mol^-1·L,当用光激发该复合物时,发现其中存在芘四硫酸四钠盐到甲基紫精的电子转移过程,并得到该过程的动力学模型。     

CCD技术应用于研究物理显影过程

本文使用一个线性CCD器件,通过反射光强(Intensity)随CCD单元及反应时间的变化,直接监测感光化学中银盐扩散转移体系中的物理显影过程,主要研究了加工液组分对物理显影的影响。实验结果表明,当使用KSCN作为银络合剂时,对苯二酚为显影剂,物理显影速率随络合剂浓度的增加而增加,随显影剂浓度的增加而下降;用Na₂S₂O₃为络合剂时,其结果相反;当用尿嘧啶为银络合剂时,显影剂浓度在0.1mol/L时反射光强出现最佳值。与此同时还研究了保护剂、溶液pH值等条件的影响。本文证明了CCD方法用于研究物理显影是可行的。     

THE PHOTOPHYSICAL PROPERTIES OF SOME C15 LUPINE ALKALOIDS:

Abstract Sparteine, the tetracyclic saturated amine alkaloid, is highly fluorescent in n-hexane solution (Φ_f= 0.64; ζ= 63 ns) and has a large Stokes shift [λ_max (abs) = 203 nm; λ_max (fluor) = 325 nm]. Its isomer, α-isosparteine, has similar properties: Φ_f= 0.55; ζ_f= 50 ns; λ_max (fluor) = 338 nm. Oxidized derivatives, such as lupanine, thermopsine, and α-diplospartyrine, are weakly fluorescent. Based on a comparison with spectroscopic and photophysical properties of the monoamine, quinolizidine, it is concluded that the excitation energy is delocalized over the two N-atoms in starteine and a-isosparteine. The self quenching rate constant for sparteine, ca. 1 times 10⁷M^-1 s^-1, is about 100 times smaller than that for quinolizidine, consistent with excited state derealization. The significant fluorescence quenching in lupanine is rationalized by the fact that N-methyl-2-piperidone mfe/molecularly quenches the fluorescence of quinolizidine at nearly the diffusion controlled rate in -hexane. Comparisons are made with the fluorescence properties of other diamines such as N, N'-dimethylbispidine and N, N'-disubstituted piperazines.     

THEORETICAL ANALYSIS OF THE PHOTOPHYSICAL PROPERTIES OF ε-ADENINE AND THE RNAphe Y-BASE

Abstract— …An analysis of the photophysical and theoretical properties of e-adenine and the RNA Y-base shows that these materials have a closer conceptual relationship to the indolizines than the purines.     

浅谈海洋环境监测质量保证工作的有效开展

总结近几年参与海洋环境监测质量保证工作的经验体会,对目前海洋环境监测质量保证工作中存在的主要问题进行了阐述,并就如何有效开展海洋环境监测质量保证工作提出建议。     

现场水分测定器的测试精度试验

现场测定机械用油中水分含量通常用ＧＢ８０３０－８７润滑油现场俊俏地。该方法读压力表数值的时间不定,人为因素大,测试结果不稳。文中对该测试方法的操作步骤及读数方法作了改进,使测定水分的时间缩短、精度提高。     

FT-RAMAN SPECTROSCOPY FOR MONITORING THE POLYMERIZATION OF ACRYLIC ACID IN AQUEOUS SOLUTION

FT-Raman spectroscopy was used to monitor the polymerization of acrylic acid in aqueoussolution. A simple method to avoid the noise in the background during the signal processing via Fouriertransformation was used in this work. The effects of the amount of initiator used on the polymerization arestudied. When the amount of the initiator in the polymerization was increased, both the rate and extent ofpolymerization of acrylic acid will be increased.     

PROTON TRANSLOCATION and CONFORMATIONAL CHANGES DURING THE BACTERIORHODOPSIN PHOTOCYCLE: TIME-RESOLVED STUDIES WITH MEMBRANE-BOUND OPTICAL PROBES and X-RAY DIFFRACTION*

Abstract– For the first time, we monitored time-resolved conformational changes inherent in bacterio-rhodopsin's reaction cycle as well as the H⁺-release events directly at the surface of bacteriorhodopsin (bR) at room temperature. Signals of optical pH-indicators in the aqueous bulk phase were compared with those of probes covalently linked to bR. The kinetics of H⁺-translocation and the correlation of the photocycle with the pumping cycle can only be determined with indicators bound to bR. The proton appears at the extracellular surface during the L₅₅₀ to M₄₁₂ transition. Upon short photo-excitation, diffraction patterns were obtained from both guanidine hydrochloride-treated wild type bR and an Asp96Asn mutant with millisecond time resolution by x-ray synchrotron radiation. The measured time course and location of the structural changes confirm and extend our previous static neutron diffraction study at -180°C. The temporal correlation of photocycle intermediates and proton translocation steps with structural changes in the protein under similar environmental conditions strongly contribute to the understanding of the pumping mechanism.     

MECHANISM FOR THE INITIATION OF ACRYLONITRILE POLYMERIZATION BY POLYPROPYLENE-BASED POLYAMIDOXIME-THIOUREA COMBINATION

Polymerization of acrylonitrile (AN) in aqueous nitric acid initiated by polypropylene-based polyamidoxime (PPAO)-thiourea (TU) combination has been investigated. The overall rate of polymerization (R_p) under the conditions of [TU]/[PPAO]<0.5 molar ratio isThe molecular weights of the polymers were found to be inversely proportional to 3/2-power of nitric acid concentration and 1-power of thiourea concentration. In addition, it is independent with the concentrations of monomer and PPAO, and decreases with increasing temperature.On the basis of these experimental results, a coordination-proton transfer mechanism for the initiation was proposed and discussed.