ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb09616.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTIn systems that are known to generate electronically excited species, the tris(bipyridine) ruthenium(II) cation, Ru(bpy)32+, ion is found to be an efficient, chemically stable, emissive energy acceptor for probing excited state formation. The chemiexcitation system employed was the thermolysis of tetramethyldioxetane. The system employed for enzymatic generation of excited species was the horseradish peroxidase‐catalyzed oxidation of appropriate substrates such as isobutyraldehyde, phenylacetal‐dehyde and indoleacetic acid. The versatility of the Ru(bpy)32+ion is exemplified by its capacity to detect excited state formation in both chemical and enzymatic systems and in homogeneous and microheterogeneous media. The long wavelength emission and chemical stability of Ru(bpy)32+facilitate quantitative studies of the sensi‐tization process. Possible routes leading to excitation of the Ru(bpy)32+ion by the chemi‐ or enzyme‐generated excited species include electronic energy transfer and electron transfer‐induced l

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb09617.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTHorseradish peroxidase catalyzes the aerobic oxidation of 2‐phenylpropanal and diphenylacetaldehyde at physiological pH to yield acetophenone and benzophenone partly in the triplet state, respectively. These excited products plus formic acid are expected from the thermolysis of dioxetane intermediates. The presence of acetophenone was demonstrated spectrophotometr‐ically and the chemiluminescence spectrum (δmax‐ 430 nm) was consistent with its triplet state. Energy transfer to 9,10‐dibromoanthracene‐2‐sulfonate ion, a triplet carbonyl counter, but not to anthracene‐2‐sulfonate ion, a singlet carbonyl acceptor, occurred, confirming the triplet nature of the main emitter. In the case of the diphenylacetaldehydelperoxidase system, benzophenone could also be detected spectrophotometrically but the corresponding chemiluminescence spectrum showed only red emission (δmax‐ 630 nm), which was tentatively attributed to singlet oxygen formed by triplet‐triplet energy transfer to ground state oxygen. Horseradish peroxidase can be replaced by other he‐meproteins such as myoglobin, hemoglobin and micro‐peroxidase as catalyst of the chemiluminescent reaction. The distinct emission spectra achieved with different hemeproteins suggest a role of the microenvi‐ronment in totally or partly protecting the excited species from oxygen collisions, resulting in emission maxima ar

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb09618.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTAn equation is proposed for the evaluation of partition or association constants from fluorescence properties (such as spectrum shape or anisotropy) whose values are not linearly related to the solute distribution. The proposed procedure is applied to the binding of pyrene to β‐cyclodextrin (employing the I1/I3relationship and fluorescence anisotropy) and to the association of pyrene to dioctadecyldimethylammonium small unilamellar vesicles (sonicated) and large unilamellar vesicles (injected). The results obtained in the latter system indicate that the pyrene partition constant between the vesicles and the aqueous medium is nearly 10 times larger in the small vesicl

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb09619.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTUltraweak light emission was detected upon injection of firefly luciferin into liveTenebriolarvae. A chemilumi‐nescent enzymatic activity dependent on molecular oxygen, D‐luciferin and MgATP was then isolated from larval fat body extracts by precipitation with 70% ammonium sulfate. D‐Luciferin and ATP can be replaced by luciferyl‐adenylate. Pyrophosphate is a main product from the chemiluminescent reaction. Thein vitrochemiluminescence intensity was not affected by peroxidase inhibitors such as N3−‐(0.5 mM) and CN−(1 mM), attesting to its nonperoxidatic nature but was strongly inhibited by AMP (1 mM), luciferin 6′‐ethyl ether (1 mM) and sodium pyrophosphate (2 mM), well‐known firefly lucifer‐ase inhibitors. Some physical‐chemical properties of this enzymatic activity were similar to those of firefly lucif‐erase (KMATP = 195 μM;K0.5luciferin ‐ 0.8 mM; optimum pH 8.5; δmax= 610 nm at pH 8.5; firefly lucifer‐ase: δmax= 565 nm at pH 8.0 and 619 mm at pH 6.0), but the chemiluminescence was not affected by addition of polyclonal antibodies raised againstPhotinus pyralisluciferase. These data suggest that this chemiluminescence results from a

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb09620.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe primary quantum yield, Φ1700, for the photoconver‐sion of the red‐absorbing form of phytochrome, Pr, to the set of primary intermediates, Ii700, was redetermined by laser‐induced optoacoustic spectroscopy at very low excitation laser fluences. The Ii700value obtained is in the range of ΦPfrreported for the complete phototransformation Pr→ Pfr(J. M. Kelly and C. Lagarias, 1985,Biochemistry24, 4003–6010). An energy level ofca150 kJ/ mol was found for the intermediates Ii700,i.e. ca85% of the 0–0 level of Pr. Furthermore, a molecular expansion of 7 mL/mol (equivalent to 11 Å3/molecule) was determined for the Pr→ Ii700transformation. It reflects the protein reorganization induced by the geometrical pho‐toisomerization of the chromophore, which results in changes of bonding interactions, in particular between the chromophore and its p

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb09621.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe Norrish‐Yang photochemistry of three isomericp‐alkyl alkanophenones (p‐propyl nonadecanophenone,p‐pentyl heptadecanophenone andp‐octyl tetradecano‐phenone) and the photo‐Fries reactions of 2‐naphthyl myristate have been investigated in the ordered (layered) phases of three isomeric alkyl alkanoates. Comparisons of photoproduct selectivity for irradiation of one substrate in the isotropic and ordered phases of one host ester provide information concerning the influence of the cylindrically shaped reaction cavities on the relative motions and conformational changes necessary to convert the reactants to products. Comparisons of photoproduct distributions from one substrate in comparable phases of two or more esters provide details concerning the “wall stiffness” and importance of functional group interactions of the reaction cavities. Finally, comparisons using one substrate and two ordered phases of the same ester indicate the role of wall stiffness on photoproduct selectivity. The results show that the course of the photochemical reactions can be controlled effectively within the ordered media and provide an indication of how to design and select ordered media to effect other photochemical transfor

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb09622.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe inhibition of horseradish peroxidase (HRP)‐cata‐lyzed oxidation of indole‐3‐acetic acid (IAA) by a phenol, caffeic acid (CA), was studied using both a kinetic approach and computer simulation. The presence of CA resulted in a lag period in IAA oxidation. The lag period increased slowly with increasing [CA] until a critical concentration, [CA]cr, was reached, then it increased much faster when [CA] was greater than [CA]cr. The [CA]crwas proportional to [IAA] and did not depend upon [HRP]. Caffeic acid was oxidized by compound I and compound II of HRP with bimolecular rate constants (6.8 ± 107and 2.1 ± 107M‐1s−l), which were much higher than the corresponding rate constants for IAA oxidation (2.3 ± 103and 2.0 ± 102M−1s−1). Our experimental data show that CA inhibits IAA oxidation because it is able to compete effectively as a peroxidase substrate. A model based on a detailed mechanism of IAA oxidation was investigated using computer simulation. A rate constant driving nonenzymatic hydroperoxide formation in IAA solution was determined, 3.0 × 10−‐7s−1. The model quantitatively describes the experimental results of this work and also qualitatively explains data published earlier. The critical inhibitor concentration is approximately equal to twice the concentration of hydroperoxide in IAA solution at the time of inhibitor addition. Therefore hydroperoxide Concentration can be calculated from the determination of critic

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb09623.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACT2‐Methyl‐1‐propenyl acetate (MPA) was hydrolyzed by wheat lipase, pancreatic lipase, hydrolases and lipopro‐tein lipase from serum in a reaction that produces 2‐methyl‐1‐propenol. The latter was subsequently oxidized by horseradish peroxidase (HRP)/H2O2/O2yielding triplet acetone that emits visible light. The integrated light emission was proportional to the units of lipase or volume of serum present. When pancreatic lipase was assayed, light emission was observed in the presence of bile salt as surfactant and chlorophyllaas light sensitizer. The potential application of this reaction in determinations of hydrolase/Iipase activities

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb09624.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTA method for determining counterion exchange selectivities at the surface of ionic micelles from time‐resolved fluorescence quenching measurements is developed. This method is employed to determine selectivity coefficients for thiosulfate/chloride exchange at the surface of cati‐onic hexadecyltrimethylammonium chloride micelles (KTS/CI,=1.1 ± 0.4) and for copper (II)/sodium exchange at the surface of anionic sodium dodecyl sulfate micelles (KCu/Na= 1.3 ± 0.3). In both cases, the selectivity coefficients are found to be independent of detergent and added salt concentr

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1996.tb09625.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY