聚电解质-磺化聚砜溶液的渗透压

本文以快速动态渗透压法,测定了磺化聚砜钠盐试样在无外加盐和有外加盐(NaNO_3)的二甲基甲酰胺中25±0.02℃时的渗透压,对实验现象进行了讨论,确认外加盐大于0.07N时,用渗透压法可以测得磺化聚砜的分子量。     

磺化间规聚苯乙烯和间规聚苯乙烯的非等温结晶动力学

对磺化度分别为 1 6 0mol% ,3 0 5mol% ,4 41mol%的磺化间规聚苯乙烯和间规聚苯乙烯的非等温结晶动力学进行了研究 ,用DSC测试了四种样品的非等温结晶过程 ,对所得数据分别用Mandelkern方法和莫志深方法进行了处理 ,发现磺化间规聚苯乙烯和间规聚苯乙烯的非等温结晶动力学参数差别较大 ,说明磺酸基团的引入对sPS结晶行为有较大的影响 ,磺酸基团之间的氢键相互作用使SsPS的结晶速率降低 ,结晶度减小 .此外 ,SsPS和sPS的Avrami指数n值均在 2～ 3之间 ,且为非整数 ,说明它们主要是以混合成核的方式结晶 .SsPS的成核与生长活化能ΔE值高于sPS的 ,并且随磺化度的增加而递增 ,sPS的ΔE值为 2 40 5 0kJ/mol,磺化度为 1 6 0mol% ,3 0 5mol%和 4 41mol%的SsPS的ΔE值分别为 2 5 1 70kJ/mol,2 72 33kJ/mol和2 90 79kJ/mol.     

聚电解质-磺化聚砜溶液的光散射

本文采用激光小角光散射法,测定了聚电解质-磺化聚砜(钠盐),在分别舍有NaNO_3、LiNO_3、LiCl、NaBr和NaI的DMF中各试样的表现分子量。结果表明,在含有0.07N NaNO_3的DMF中,磺化聚砜的表观分子量接近于试样的真实分子量。     

染料与表面活性物质间的相互作用—在胶束形成前的能量转移

近年来,在胶束体系中的能量转移问题由于人们对胶束研究的兴趣增长而受到重视^[1].胶柬的独特组成使它能在分子水平上组织反应物进行化学反应.把胶束研究中得到的数据和在均相体系中的结果相比较就可对所进行的反应的分子细节有更多的了解.胶束,作为一种荷电粒子,还可在某些要求实现电荷分离的场合起到作用,这在光能一电能转换的太阳能利用上是极为重要的^[2].对胶束体系能量转移的研究可对反应物和胶束间的相互作用以及胶束结构等问题提供许多有用的资料,有助于更好地了解和利用胶束.从七十年代起,Shinitzky^[3],Almgrensup>[4]和Gratzel^[5]等对此进行了大量研究,取得了进展.但是对胶束形成前或形成过程中,即体系中表面活性物质浓度低于临界胶束浓度(cmc)时的能量转移现象迄今还报道较少.最近Kusumoto^[6]等曾在胶束形成前的区域(premicellar region)内对罗丹明-6G染料和一种菁染料间的能量转移进行了研究,指出:由于染料的存在,有可能在表面活性物质浓度达到cmc之前形成了一种富染料的混合胶束,因而促进了能量转移的进行.这种“预胶束”的概念,Ghosh^[7]在研究染料和表面活性物质溶液的荧光光谱时曾于1970年提出过,但未正式公布所得结果.本工作对十二烷基硫酸钠(简称SLS)溶液胶束形成过程中几种阳离子染料间的能量转移进行了研究.     

聚电解质-磺化聚砜浓溶液的流变特性

本文采用NXS-11型旋转粘度计,在不同温度下测定了不同IEC的磺化聚砜试样,在DMF、3D/T、DMF+0.07N NaNO_3和3D/T+0.07N NaNO_3中浓溶液的流变性,讨论了聚电解质效应对实验结果的影响。     

疏水相互作用对阳离子聚电解质与染料键合的影响

用平衡渗析法研究了阳离子聚电解质PAm·MG 和P(St-Am·MG)与甲基橙(MO)及P(St-Am·MG)与MO的同系物乙基橙(EO)、橙武Ⅳ(O-Ⅳ)在25、35、45和55 ℃下相互作用的热力学. 由K1otz方程, 求得键合常数K_1和热力学参数ΔG、ΔH及ΔS. 含疏水基的P(St-Am·MG)与MO的键合能力比不含疏水基的PAm·MG 强. P(St-Am·MG)与不同染料作用时, 键合程度为O-Ⅳ>EO>MO, 即染料的疏水性越强, 与高聚物的作用程度越大.键合体系加入脲或甲醇, 疏水相互作用受到破坏, 导致高聚物与染料之间的键合受到削弱.     

聚电解质对离子型染料形成激基缔合物和能量传递的增强作用

在水溶液中聚苯乙烯磺酸钠(Napss)可以增加离子型染料吖啶橙和吡红的局部浓度,从而显著地促进吖啶橙形成激基缔合物,增大吖啶橙-吡红能量传递效率.在10^-^4mol.dm^-^3Napss存在下,形成吖啶橙激基缔合物的速率常数比Napps不存在时增大两个数量级,而离解常数小一个数量级.表明在聚电解质存在下,两个吖啶橙分子在基态时相互靠近处于液基缔合物的构型.加入小分子电解质可阻止染料形成激基缔合物.     

磺化酞菁在甲醇-水溶液中的二聚作用研究

研究了不同磺化度的酞菁在甲醇－水混合溶剂中的聚集行为，通过紫外－可见光谱测定，发现磺化度在１．０以上的时染料在稀溶液中主要单体和二聚体的形式存在，并可用简单的方法计算出聚集平衡常数和平衡时单体所占的百分化，得到磺化越低越易聚集的结论，有关激发态的实验表明，增加酞菁磺化度有助于提高表观荧光量子产率，但对荧光寿命影响较小。     

染色尼龙丝中光物理过程的研究——聚己内酰胺与染料1-氨基-4-羟基蒽醌之间的能量转移

在研究用染料1-氨基-4-羟基蒽醌染色的尼龙-6单丝的燐光光谱时,观察到染料的延迟荧光。这表明在这一体系中发生了聚合物的杂质基团与染料间的能量转移。用测定尼龙丝的燐光寿命随染料浓度变化的方法对此过程作动力学研究,测得能量转移速度常数k_t=2901·mol^-1·s^-1,能量转移的临界距离R₀=52.0Å,并证明该过程是以三线态-单线态的远程共振机理进行的,染料淬灭了尼龙-6中有害的杂质基团激发三线态,从而起到了光稳定化的作用。     

癸基硫酸钠和癸烷磺酸钠与阳离子聚电解质相互作用的差别

 通过表面张力及荧光探针方法, 研究了癸基硫酸钠和癸烷磺酸钠与阳离子聚电解质聚二甲基二烯丙基氯化铵(PDMDAAC)的相互作用. 结果表明, 虽然单一癸基硫酸钠和癸烷磺酸钠性质非常相似, 但它们与PDMDAAC的相互作用有明显差别, 癸基硫酸盐与PDMDAAC的相互作用明显强于癸烷磺酸盐. 通过量子化学计算结果对本文实验观测结果进行了解释.     

INTERACTION BETWEEN TYROSINE AND DIVALENT SULFUR IN FLUORESCENCE QUENCHING AND IN THE PHOTOCHEMISTRY OF RIBONUCLEASE

Abstract— –Ribonuclease is inactivated in aqueous solution by u.v. light through different mechanisms according to whether divalent sulfur or aromatic amino acids are the primary light absorbers. At 284 nm, absorbed mainly by tyrosine, the presence of O₂ inhibits photoinactivation and H₂S formation, but does less so at 254 or 313 nm. Based on data with model substances containing disulfide groups a mechanism is indicated in which excited tyrosine is quenched through electron transfer to adjacent divalent sulfur within the protein. Disulfide compounds are shown to be very efficient quenchers of tyrosine fluorescence.     

PHOTOCHEMISTRY OF HEPARIN-ACRIDINE ORANGE COMPLEXES IN SOLUTION: PHOTOCHEMICAL CHANGES OCCURRING IN THE DYE AND POLYMER ON FLUORESCENCE FADING

Abstract— Photolysis of acridine-orange-heparin complexes in N₂- and O₂-saturated solution results in permanent photooxidation of AO with little or no concomitant change in the heparin moiety. The major photoproduct is mono- N -demethylated acridine orange; in O₂-saturated solution an additional minor oxygenated product, most likely the 10-oxide (N-oxide) or the 9-acridanone (acridone) is also formed. The results suggest an intermolecular electron transfer between adjacently adsorbed dye molecules. The heparin moiety plays a significant role in the photochemistry by bringing dye molecules into favorable geometric orientation for biomolecular reaction and by means of specific dye-polymer interactions.     

FLUORESCENCE ENERGY TRANSFER BETWEEN DIMETHYLDIAZAPEROPYRENIUM DICATION AND ETHIDIUM INTERCALATED IN POLY d(A-T)

Dimethyldiazaperopyrenium is one of the largest known DNA intercalators. Fluorescence energy transfer occurred between dimethyldiazaperopyrenium (donor) and ethidium (acceptor) when these dyes were bound to a double-stranded polynucleotide such as poly d(A-T). The addition of increasing amounts of ethidium bromide led to a marked shortening of the fluorescence lifetime of the donor, whereas the excited state of the acceptor was progressively populated via energy transfer from the donor. Critical Förster distance between these two chromophores was calculated to be 3.8 nm. The observed transfer efficiency was lower than that calculated on the basis of this critical distance and a statistical distribution of bound drugs. These results are discussed taking into account the conformational change induced by intercalation of dimethyldiazaperopyrenium in the double-stranded polynucleotide.     

EXCITATION-ENERGY TRANSFER BETWEEN TYROSINE AND TRYPTOPHAN IN PROTEINS EVALUATED BY THE SIMULTANEOUS MEASUREMENT OF FLUORESCENCE AND ABSORBANCE

Abstract— The efficiencies of the excitation–energy transfer from tyrosine to tryptophan residues in eight globular proteins in the native and denatured states are obtained by studying the wavelength dependence of the fluorescence quantum yield. The measurements are made over a wide wavelength range using a computer-controlled spectrophotometer which can measure the fluorescence and absorbance simultaneously in one sample solution (Wada et al. , 1980). The values of the energy transfer efficiencies ranged from 0.17 ± 0.12 to 0.69 ± 0.06 in the native state and from -0.04 ± 0.09 to 0.12 ± 0.06 in the denatured state. These values are considerably lower than the values reported by Kronman and Holmes (1971); in particular, an almost complete absence of energy transfer for the denatured state is shown.     

ENERGY TRANSFER BETWEEN THE PRIMARY DONOR BACTERIOCHLOROPHYLL AND CAROTENOIDS IN Rhodopseudomonas sphaeroides

Abstract— The temperature dependencies of the primary donor triplet state spectra are presented for the phorosynthetic bacteria Rhodopseudomonas sphaeroides wild type. GIC and R26. The data suggest that energy transfer from the primary donor triplet state to the reaction center carotenoid is dependent on the type of carotenoid present, reversible in the case of strain GIC, and best understood by a model depicting the kinetic processes that can occur between two potential energy surfaces; one representing the state ³BChl₂*Car and the other representing BChl₂³Car*. Furthermore, it is shown that the onset of spin lattice relaxation in the primary donor triplet is most likely coupled to the same energy vibrational mode as that which promotes triplet state energy transfer from the primary donor to the reaction center carotenoid     

PICOSECOND FLUORESCENCE KINETICS and ENERGY TRANSFER IN THE ANTENNA CHLOROPHYLLS OF GREEN ALGAE*

Single-photon timing measurements on flowing samples of Chlorella vulgaris and Chlamydomonas reinhardtii at low excitation intensities at room temperature indicate two main kinetic components of the fluorescence at open reaction centers (F₀) of photosystem II with lifetimes of approx. 130 and 500 ps and relative yields of about 30 and 70%. Closing the reaction centers progressively by preincubation of the algae with increasing concentrations of 3-(3′,4′-dichlorophenyl)-l,l-dimethylurea (DCMU) and hydroxylamine gave rise to a slow component with a lifetime increasing from 1.4 to 2.2 ns (F_max) The yield of the slow component increased to 65-68% of the total fluorescence yield in parallel to a decrease in the yield of the fast component to a value close to zero at the f_max-level. The 130 ps lifetime of the fast component remained unchanged. The middle component showed an increase of its lifetime from 500 to 1100 ps and of its yield by a factor of 1.5. Spacing of the ps laser pulses by 12 μs allowed us to resolve a new long-lived fluorescence component of very small amplitude which is ascribed to a small amount of chlorophyll not connected to functional antennae. The opposite dependence of the yield of the fast and the slow component on the state of the reaction centers at almost constant lifetimes is consistent with a mechanism of energy conversion in largely separately functioning photosystem II units. Yields and lifetimes of these two components are in agreement with the high quantum yield of photosynthesis. The lower lifetime limit of 1.4 ns of the slow component is assigned to the average transfer time of an excited state from a closed to a neighboring open reaction center and the increase in the lifetime to 2.2 ns is evidence for a limited energy transfer between photosystems II. Relative effects of changing the excitation wavelength from 630 to 652 nm on the relative fluorescence yields of the kinetic components were studied at the fluorescence wavelengths 682, 703 and 730 nm. Our data indicate that (i) the middle component has its fluorescence maximum at shorter wavelength than the fast component and (ii) that the antennae chlorophylls giving rise to the middle component are preferentially excited by 652 nm light. It is concluded that the middle component originates from the light-harvesting chlorophyll alb protein complexes and the major portion of the fast component from the chlorophyll a antennae of open photosystem II reaction centers.     

INTERACTION BETWEEN UPOSOMES AND MONOLAYERS IN THE PRESENCE OF CALCIUM

Abstract

The interaction between phospholipid vesicles (phosphatidylcholine : phosphatide acid, 90:10 w/w) and phosphatidylcholine : cholesterol (70:30, molar ratio) monolayers at air/water interfscks has been studied at. several concentrations of calcium cation ( Ca²⁺). The liposome vesicles were SUVs and MLVS.

The vesicles interact with the monolayers, rapidly causing a large increase in surface pressure. Limiting values of surface pressure, 2.07-6.99 mN.m-1 for SUVs, and 7.01-11.11 mN.m^?1 for MLVs, were reached in less than 40?min.

Calcium ion concentration affects the liposome size in MLVs, producing an increase of gyration radius. The SUVs are little influenced. The change in size can be due to a variation of liposome composition induced by calcium: cholesterol molecules can migrate from monolayer to liposomes and the redistribution of exchanged lipids in the outer bilayer can also explain the size variation.