The electrochemical behavior of Eastman AQ/meldola blue-coated microelectrodes

Eastman-AQ 55D was coated onto a carbon fiber microelectrode surface, and the resulting modified electrodes exhibited high stability. Substantial improvement in the stability was observed as a result of good adhesion and the strong binding of large hydrophobic cations of Eastman AQ 55D. The electrode reaction of meldola blue bound in the polymer film showed a reversible, one-electron transfer process. The effects of solution pH and influence of supporting electrolyte on the modified carbon fiber microelectrode are discussed. The diffusion coefficient of meldola blue in the AQ polymer film determined by chronoamperometry is 2.3 x 10(-18) cm(2) s(-1), and the heterogeneous rate constant of meldola blue at the AQ polymer film/electrode determined by normal pulse voltammetry is 3.97 x 10(-3) cms(-1).

胆红素胆绿素在铂电极上氧化还原反应的现场光谱电化学研究

本文采用现场光谱电化学技术研究了胆红素(BR Ⅳα)、胆绿素(BV Ⅳα)及其氧化产物胆汁红紫素(Bi-Pu)在铂电极上的电氧化还原行为,并着重对上述过程的动力学进行了探讨。结果表明,在洁净的铂电极上,上述胆汁色素可通过控制电位实现Ⅳ构成的反应循环中,Ⅰ,Ⅱ可达到准可逆电子转移反应,式量非均相速率常数=1.5×10~(-4)cm·s~(-1),而Ⅲ,Ⅳ的氧化还原则为不可逆,=4.8×10~(-5)cm·s~(-1)。

肌红蛋白在聚天青A薄膜修饰电极上电极过程的研究

本文采用电聚合方法成功地制备了聚天青A(AZA)薄膜修饰电极。利用现场光透薄层光谱电化学方法研究了肌红蛋白于聚AZA薄膜修饰铂网光透电极上的准可逆异相电子传递过程,给出了电极反应的热力学参数[标准式电位E~0′=0.055V(vs·NHE),电子反应数n=1.1]和动力学参数(异相电子传递速率常数k_(sh)=1.73×10~(-4)cm·s~(-1),电子传递系数α=0.68).X光电子能谱表面分析表明肌红蛋白于修饰电极表面存在吸附。用现场循环电位吸收和循环伏安法解析了肌红蛋白于膜电极上的伏安响应,提出了肌红蛋白于聚AZA薄膜修饰电极上的异相电子传递过程机理。

电活性质点Fe~(2+)离子在六氰亚铁钒薄膜中的传输

电活性质点Fe~(2+)可穿透六氰亚铁钒薄膜在玻璃碳基体电极表面于较负电位处直接氧化,也可经VHF膜中氧化还原点位的媒介在较正电位处于膜-溶液界面及膜内部发生催化氧化.两个过程分别在用VHF修饰过的旋转GC电极上的伏安曲线中产生,可明确分辨的第一波和第二波.第一波的极限电流受Fe~(2+)离子在溶液中和膜中的扩散速率控制.VHF薄膜对Fe~(2+)离子的透过能力,kD_m/d,为10~(-3)-10~(-2)cm·s~(-1)数量级,随膜厚度增大而减小,不随溶液中Fe~(2+)离子浓度改变.

Characterization of the main light-harvesting chlorophyll a/b-protein complex of green alga, Bryopsis corticulans

The main light-harvesting chlorophyll a/b -protein complex (LHC II) has been isolated directly from thylakoid membranes of shiphonous green alga, Bryopsis corticulans Setch. by using two consecutive runs of anion exchange and gel-filtration chromatography. Monomeric and trimeric subcomplexes of LHC 11 were obtained by using sucrose gradient ultracentrifugation. Pigment analysis by reversed-phase high performance liquid chromatography showed that chlorophyll a (Chl a), chlorophyll b (Chl b), neoxanthin, violaxanthin and siphonaxanthin were involved in LHC 11 from B. corticulans. The properties of electronic transition of monomeric LHC II showed similarities to those of trimeric LHC II. Circular dichroism spectroscopy showed that strong intramolecular interaction of excitonic dipoles between Chl a and between Chl b exist in one LHC II apoprotein, while the intermolecular interaction of these dipoles can be intensified in the trimeric structure. The monomer has high efficient energy transfer from Chl b and siphonaxanthin to Chl a similarly to that of the trimer. Our results suggest that in B. corticulans, LHC II monomer has high ordered pigment organization that play effective physiological function as the trimer, and thus it might be also a functional organization existing in thylakoid membrane of B. corticulans.

Isolation of the main light-harvesting chlorophyll a/b-protein complex from thylakoid membranes of marine alga, Bryopsis corticulans by a direct method

The main chlorophyll a/b light-harvesting complex (LHC 11) has been isolated directly from thylakoid membranes of marine green alga (Bryopsis corticulans Setch.) by two consecutive runs of anion exchange and gel-filtration chromatography. LHC 11 proteins in the membrane extracts treated with 3% n-Octyl-b-D-glucopyranoside (OG) obtained specific binding ability on Q Sepharose column, and thus were isolated from the thylakoid membranes in a highly selective fraction. The monomeric, trimeric and oligomeric subcomplexes of LHC 11 have been obtained by fractionation of the LHC 11 mixes with sucrose density gradient ultracentrifugation. The SDS-PAGE analysis of peptide composition and absorption spectrum showed that LHC 11 monomers, trimers and oligomers prepared through this work were intact and in high purity. Our report is the first to show that it is possible to purify LHC If directly from thylakoid membranes without extensively biochemical purification.

Structural analysis of peptides of PSII light-harvesting complexes in siphonous green algae, Codium fragile

peptide composition and arrangement of 4 major light-harvesting complexes LHCP1-3 and LHCP3, isolated from siphonous green algae (Codium fragile (Sur.) Hariot.) were investigated. LHCP1 showed five main peptides, 34.4, 31.5, 29.5, 28.2 and 26.5 kD in SDS-PAGE, the 34.4 and 31.5 kD peptides were never found in higher plants. LHCP3 contained the other four kinds of LHCP1 peptides except 34.4 kD, while LHCP3, consisted of only 28.2 and 26.5 kD peptides. We found that 34.4, 28.2 and 26.5 kD peptides were easy to decompose from LHCP1 when subjected to SDS-PACE without pretreatment. They might be located at the exterior of LHCP1, while the 31.5 and 29.5 kD peptides were at the central part. The 28.2 and 26.5 kD peptides often occurred in CPa, the center complex of PS II. They are possibly the LHC II peptides tightly associated with CC II. According to the results described above, a peptide map of LHCP1 was sketched.

Isolation of PSI from a siphonous marine green alga, Codium fragile

Three different forms of PS I complexes were isolated from a siphonous marine green alga, Codium fragile, by Triton X-100 sucrose gradient centrifugation. Zone III had a Chl a/b>20, and designated as PS I. core complex CC I because it created only CP I band in mild PAGE. Zone IV and V had absorption at 436 and 674 nm, 467 and 650 nm, and 540 nm, suggesting the presence of Chl a, Chl b, siphonaxanthin and siphonein, Chl a/b were 3.23 and 2.4, respectively. Both CP I and CP I a bands were observed when they were subjected to mild PAGE. Therefore, Zone IV and V were different forms of PS I complexes that consisted of CC I and different amount of light-harvesting complex LHC I. Zone III contained only 66 and 56 ku peptides in SDS-PAGE, while Zone IV and V had 4 different LHC I peptides of 25, 26, 26.2 and 27.5 ku in addition to 66, 56 ku peptides. Fluorescence emission spectra showed that efficient energy transfer were kept among pigments in isolated PS I complexes. Excitation energy absorbed by Chl b, siphonaxanthin and siphonein can be transferred to Chl a.

Characteristics and comparative study of chlorophyll-protein complexes from siphonous green algae

By mild PAGE method, 11, 11, 7 and 9 chlorophyll-protein complexes were isolated from two species of siphonous green algae ( Codium fragile (Sur.) Harlot and Bryopsis corticulans Setch.), green alga (Ulothrix flacca (Dillw.) Thur.), and spinach (Spinacia oleracea Mill.), respectively. Apparent molecular weights, Chi a/b ratios, distribution of chlorophyll, absorption spectra, low temperature fluorescence spectra of these complexes were determined, and compared with one another. PS I complexes of two siphonous green algae are larger in apparent molecular weight because of the attachment of relative highly aggregated LHC I. Four isolated light-harvesting complexes of PSII are all siphonaxanthin-Chl a/b-protein complexes, and they are not monomers and oligomers like those in higher plants. Especially, the absence of 730 nn fluorescence in PS I complexes indicates a distinct structure and energy transfer pattern.

Diversity of pigment-protein complexes of photosynthetic organisms.

PS I, PS II and light-harvesting complexes (LHC) in oxygen evolving photosynthetic organisms were reviewed. These organisms include cyanobacteria, red algae, brown algae, diatoms, chrysophytes, dinophytes, xanthophytes, crypophytes, green algae and green plants. The diversity of pigment-protein complexes that fuel the conversion of radiant energy to chemical bond energy was highlighted, and the evolutionary relationships among the LHC structural polypeptides and the characteristics of the fluorescence emission of PS I at 77 K was discussed.

机器人手臂弹性动力学分析的高效算法

本文提出一种用于机器人手臂弹性动力学分析的新方法,该方法采用了动力学方程缩减技术,使计算时间大为减少。在此基础上针对关节型机器人结构特点,提出了考虑手臂关节之间的弹性连接的数学模型,使计算精度得到提高,最后给出了一个实例。

Ammonia synthesis over Ru/C catalysts with different carbon supports promoted by barium and potassium compounds

Ammonia synthesis over ruthenium catalysts supported on different carbon materials using Ba or K compounds as promoters has been investigated. Ba(NO3)(2), KOH, and KNO3 are used as the promoter or promoter precursor, and activated carbon (AC), activated carbon fiber (ACF). and carbon molecular sieve (CMS) are used as the support. The activity measurement for ammonia synthesis was carried out in a flow micro-reactor under mild conditions: 350-450 degreesC and 3.0 MPa. Results show that KOH promoter was more effective than KNO3. and that Ba(NO3)(2) was the most effective promoter among the three. The roles of promoters can be divided into the electronic modification of ruthenium, the neutralization of surface functional groups on the carbon support and the ruthenium precursor. The catalyst with AC as the support gave the highest ammonia concentration in the effluent among the supports used, while the catalyst with ACF as the support showed the highest turnover-frequency (TOF) value. It seems that the larger particles of Ru on the carbon supports are more active for ammonia synthesis in terms of TOF value. (C) 2001 Elsevier Science B.V. All rights reserved.