Analysis of Fluorescence Lifetime of Protochlorophyllide and Chlorophyllide in Isolated Etioplast Membranes Measured from Multifrequency Cross-correlation Phase Fluorometry

The fluorescence decays of protochlorophyllide (Pchlide) and of chlorophyllide (Chlide) in wheat etioplast membranes were analyzed using a multiexponential fluorescence decay model. Using different excitation wavelengths from 430 to 470 nm, we found that a triple-exponential model at 14°C and a double-exponential model at — 170°C were adequate to describe the Pchlide fluorescence decay. We discuss the origin of the three fluorescence lifetime components at 14°C on the basis of the dependence of their fractional intensities on the excitation wavelength and by correlating the fractional intensities with integrated fluorescence intensities of different Pchlide forms in steady-state fluorescence spectra. The fluorescence decay of the main Pchlide form, photoactive Pchlide-F657, is shown to have a complex character with a fast component of 0.25 ns and a slower component of about 2 ns. Two lifetime components of 2 ns and 5.5–6.0 ns are ascribed to the second photoactive form, Pchlide-F645, and to nonphotoactive Pchlide forms, respectively. In etioplast membranes preilluminated by a short saturating light pulse, we found a single 5.0 ns component for Chlide-F688 (the Chlide-NADPH: protochlorophyllide oxidoreductase [PORJ-NADP⁺complex) and an additional 1.6 ns component when the formation of Chlide-F696 (the Chlide-POR-NADPH complex) was promoted by exogenous NADPH. From the fluorescence lifetime results we evaluated the quantum yield of the primary photoreaction by Chlide-F696 as being 70%.     

Study of Immunoassay Methods for Recombinant Human Erythropoietin （rhEPO） Using Competitive ELISA

Two different immunoassay methods,competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) and amplificative competitive indirect ELISA(ACI-ELISA) using biotin-avidin complex system were studied to detect rhEPO.The linear ranges were 50-20000ng/mL and 10-50000ng/mL for CI-ELISA and ACI-ELISA,respectively.The low detection limits of CI-ELISA and ACI-ELISA were 62.8ng/mL and 8.5ng/mL,respectively.     

稀水溶液中聚乙烯吡咯烷酮构象行为的荧光研究

以苊烯(ACE)为荧光标记物,8-苯胺基-萘磺酸(ANS)为荧光探针,利用荧光各向异性、荧光猝灭以及非辐射能量转移等静态荧光技术研究了聚乙烯吡咯烷酮(PVP)在稀水溶液中的构象行为.结果表明,PVP在稀水溶液中呈松散自由线团构象,这种构象不随溶液pH的变化而显著变化.不同于其它水溶性高分子,PVP有很强的氢键形成能力,易与具有活泼氢的其它高分子或小分子相结合,并易被金属氧化物类吸附剂吸附.因此PVP可被用来修饰某些具有疏水结构的水溶性高分子.PVP水溶液在pH=7以上相当稳定,放置1周性质没有显著变化.     

An ab initio Molecular Orbital Study of the Conformational Properties of all-(Z)-Cyclododeca-1,4,7,10-tetraene

Summary.  Ab initio HF/6-31G^* and MP2/6-31G^*//HF/6-31G^* methods were used to calculate the structure optimization and conformational interconversion pathways for all-(Z )-cyclododeca-1,4,7,10-tetraene. This compound adopts the symmetrical crown (C _4v) conformation. Ring inversion takes place via symmetrical intermediates, such as boat-chair (BC, C _s) and twist (C _2h) conformers and requires about 22.3 kJ · mol⁻¹. The calculated strain energies for BC and twist conformers are 5.9 and 13.5 kJ · mol⁻¹. The results of semiempirical AM1 calculations for structural parameters and relative energies of the important geometries of the title compound are in good agreement with the results of ab initio methods. Received July 9, 2001. Accepted September 26, 2001     

同步荧光光谱法研究明胶蛋白质与铜(II)的相互作用

利用同步荧光光谱技术,研究了pH为10.0时,Cu2+离子与明胶的相互作用,推导出含有n个键合位置的明胶大分子与Cu2+离子的结合公式;用明胶中两种荧光基团的荧光强度变化数据,线性拟合出Cu2+离子与明胶的结合常数K和结合位点数n.讨论了Cu2+离子对明胶分子构象的影响.非线性拟合结果与实验值相当吻合.     

蝶呤类化合物的荧光性能研究

研究了蝶呤类化合物的天然荧光特性。着重考察了新蝶呤、生物蝶呤、黄蝶呤和蝶呤在 p H7.7磷酸盐缓冲溶液条件下的荧光光谱及各种因素对其荧光强度的影响。在最佳实验条件下 ,四种蝶呤类化合物的线性范围为 :蝶呤 0 .6～ 2 .8μg/m L,新蝶呤 0～ 2 .6μg/m L,生物蝶呤 0～ 2 .4μg/m L,黄蝶呤 0～ 6.0 μg/m L,检出限依次为 :4.2 9× 1 0 - 7g/m L,6.71× 1 0 - 8g/m L,5.79× 1 0 - 9g/m L和 1 .75× 1 0 - 8g/m L     

单分散PPE齐聚物的合成及其荧光性质

合成了PPE的齐聚物{1,4-二[3,5-二（3-甲基-3-羟基-1-丁炔基）苯炔基]苯）（4）,通过^1H—NMR对其结构进行表征,并对其荧光性质做了研究。研究结果表明引入四个2-甲基-2-羟基-丁炔基作为取代基团后,溶解性提高。取代基的引入导致齐聚物4旋转阻力增大,溶液荧光有明显的精细结构。而4具有较好的荧光单色性,因而是一种潜在的新型荧光发射材料。     

Study on Aromatic Phosphines for Novel Fluorometry of Hydroperoxides (I) -Synthesis and Spectral Properties of Diphenyl Aryl Phosphines and Their Oxides

Abstract

1-Naphthyldiphenylphosphine (NDPP), 9-anthryldiphenylphosphine (ADPP) and diphenyl-1-pyrenylphosphine (DPPP) and their oxides were prepared from triphenyl-phosphine (TPP) and the corresponding aryl bromides. These phosphines had no fluorescence, but their oxides showed blue fluorescence. The order of fluorescence intensities of these oxides were DPPP oxide > ADPP oxide > NDPP oxide. Hydroperoxides oxidized these phosphines to the corresponding oxides quantitatively. The relative reactivities were TPP > NDPP > DPPP > ADPP. The phosphines were stable in the dark, however, unstable in the light in chloroform. The reaction is proposed as novel type of fluorometry for hydroperoxides.     

Synthesis and Conformational Properties of Bis（calix [4] arene）

The bis(calix [4] arene)3 was synthesized in moderate yield by the reaction of p-tert-butylcalix [4] arene (1) with 1,4-bis(chloromethyl) benzene (2). The conformation of all alkylated product 4 was investigated by the variable-temperature ^1H-NMR.     

Fluorescence Determination of Merucury(II) Using a Thymine Aptamer

A label-free thymine-rich sequence and a molecular beacon were synthesized to construct a highly sensitive and selective fluorescence probe for the determination of mercury(II). The aptamer of the thymine-rich sequence selectively bonded with mercury(II) with an accompanying change in the fluorescence intensity of the molecular beacon due to the higher affinity of the aptamer with mercury(II). The limit of detection was 12.7 nanomolar, and a linear relationship was obtained between the fluorescence and mercury(II) concentrations up to 1 micromolar. The assay was highly selective for the mercury(II) and not significantly affected by other metal ions.     

稳态荧光探针法研究对-烷基-苄基聚氧乙烯醚羧酸甜菜碱的聚集行为

利用荧光探针法和表面张力法测定了一类疏水基中含有苯基的新型甜菜碱两性离子表面活性剂对-烷基-苄基聚氧乙烯醚羧酸甜菜碱(ABECB)的临界胶团浓度(cmc)、胶团微极性和表面张力(γ_cmc).研究结果表明,荧光探针(芘)法可用来测定这类表面活性剂的临界胶团浓度(cmc),且测定结果与表面张力法(吊片法)接近;ABECB具有较低的cmc和γ_cmc值,表明此类表面活性剂具有优良的表面活性; 胶团的微极性随着疏水链长的增大而略微减小,氧乙烯(EO)单元数的增大对ABECB胶团核内的微极性影响不明显.     

Synthesis and Striking Fluorescence Properties of Hyperbranched Poly(amido amine)

Hyperbranched poly(amido amine) (h‐PAMAM) was synthesized from different feed ratios of diethylene triamine and methyl acrylate by the simple one‐pot and commercial synthesis method. Reaction procedures and products were intensively studied by FTIR, inherent viscosity and fluorescence techniques. The ill‐structured h‐PAMAM shared similar chemical and physical properties with well defined poly(amido amine) (PAMAM) dendrimers in generation 2 or 3. Its strong fluorescence properties were influenced by pH values, solvents, concentrations, terminal groups and other factors.     

Simulation Study of the Conformational Properties of Diblock Polyelectrolytes in Salt Solutions

Coarse-grained molecular dynamics simulations are performed to understand the behavior of diblock polyelectrolytes in solutions of divalent salt by studying the conformations of chains over a wide range of salt concentrations. The polymer molecules are modeled as bead spring chains with different charged fractions and the counterions and salt ions are incorporated explicitly. Upon addition of a divalent salt, the salt cations replace the monovalent counterions, and the condensation of divalent salt cations onto the polyelectrolyte increases, and the chains favor to collapse. The condensation of ions changes with the salt concentration and depends on the charged fraction. Also, the degree of collapse at a given salt concentration changes with the increasing valency of the counterion due to the bridging effect. As a quantitative measure of the distribution of counterions around the polyelectrolyte chain, we study the radial distribution function between monomers on different polyelectrolytes and the counterions inside the counterion worm surrounding a polymer chain at different concentrations of the divalent salt. Our simulation results show a strong dependence of salt concentration on the conformational properties of diblock copolymers and indicate that it can tune the self-assembly behaviors of such charged polyelectrolyte block copolymers.     

Multifrequency EPR studies on the Mn(II) centers of oxalate decarboxylase

Oxalate decarboxylase from Bacillus subtilis is composed of two cupin domains, each of which contains a Mn(II) ion coordinated by four identical conserved residues. The similarity between the two Mn(II) sites has precluded previous attempts to distinguish them spectroscopically and complicated efforts to understand the catalytic mechanism. A multifrequency cw-EPR approach has now enabled us to show that the two Mn ions can be distinguished on the basis of their differing fine structure parameters and to observe that acetate and formate bind to Mn(II) in only one of the two sites. The EPR evidence is consistent with the hypothesis that this Mn-binding site is located in the N-terminal domain, in agreement with predictions based on a recent X-ray structure of the enzyme.     

反相高效液相色谱法分离重组促红细胞生成素

利用反相高效液相色谱法对重组促红细胞生成素进行了纯化。结果表明,利用Ｃ４反相柱和乙腈－三氟乙酸流动相在洗脱梯度和上样样品纯度等条件都较适当时,可以简单、快速、高效地从粗品中分离出重组促红细胞生成素,获得的产品纯度高,接近１００％;比活性好,约为１．９６×１０８ＩＵ／ｇ蛋白。     

一种新型的荧光探针化合物用于研究水溶性高分子的构象问题

本工作合成了一种聚合的分子内电荷转移化合物，作为荧光探针。利用荧光探针技术来研究水溶性高聚物在水溶液中的构象变化，进一步证实了在聚甲基丙烯酸的水溶液中存在着疏水微区。     

4-酰基-双(1,3-二苯基-5-吡唑啉酮)铽(Ⅲ)配合物的合成及荧光性质

合成了3种4-酰基-双(1,3-二苯基-5-吡唑啉酮),1,5-双(1,3-二苯基-5-吡唑啉酮-4-基)-1,5-戊二酮;1,6-双(1,3-二苯基-5-吡唑啉酮-4-基)-1,6-己二酮和1,10-双(1,3-二苯基-5-吡唑啉酮-4-基)-1,10-癸二酮,通过元素分析、红外光谱和核磁共振氢谱对产物组成进行了表征.合成了它们的Tb(Ⅲ)二元和三元[1,10-二氮杂菲(Phen) 或2,2-联吡啶(Dipy)]配合物,测定了配合物的荧光光谱,对其荧光性质进行了研究.结果表明,配合物发射Tb(Ⅲ)的特征荧光,4-酰基-双(1,3-二苯基-5-吡唑啉酮)配体的三重态能级与Tb(Ⅲ)的最低激发态(5D4)能级匹配较好;配合物荧光强度随4-酰基-双(1,3-二苯基-5-吡唑啉酮)配体2个吡唑环间碳链的增长而减弱;第2配体Phen 和Dipy具有荧光增强作用,且前者优于后者.     

Synthesis and Conformational Properties of the Sterically Crowded D3d-Symmetric all-trans Hexa(spirotetrahydrofuranyl)cyclohexane System

An unprecedented high barrier to ring inversion [Eq. (1)] prevents 1 from engaging in bifacial complexation with lithium ions. The X-ray crystal structure analysis of this hexaspiro compound corroborates the adoption of a cyclohexane chair with all six C−O bonds projected equatorially ( 1 -eq).     

Electrooptical and Conformational Properties of Poly(1-Trimethylsilyl-1-Propynes) with Different Chain Microstructures

The methods of the Kerr effect and solution hydrodynamics were applied to study the electrooptical and hydrodynamic properties of samples of disubstituted polyacetylenes, poly(1-trimethylsilyl-1-propynes), prepared by polymerization of 1-trimethylsilyl-1-propyne with NbCl₅ and TaCl₅/BuLi as catalysts. The experimental electrooptical characteristics of polymers were compared with those calculated by PM3 semiempirical quantum-chemical method.     

Conformational Analysis of Sulfated α-(1→3)-Linked D-Galactobioses Using the Mm3 Force-Field

Abstract

The conformational maps of eight derivatives of the disaccharide α-D-Galp-(1→3)-β-D-Galp sulfated in different positions were obtained using the MM3 force-field specially parameterized for sulfate ester groups. As occurred with MM2, the conformational flexibility of the glycosidic linkage is only slightly hindered by sulfation. A substantial effect of sulfation of the β-D-galactose unit on position 4 shifts the global minimum to positive Ψ_H (C1′-O3-C3-H3) angles, while sulfation at position 2 of the same unit deepens the well at negative Ψ^H angles. On the other hand, sulfation on the α-D-galactose unit has a lesser effect, which in any case tends to stabilize the minimum at negative Ψ_H angles.