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1.
《结构化学》1985,(3)
<正> The principle and method for calculating the chemical shifts of substituted benzenes have been extended to the calculation of chemical shifts in disubstituted naphthalenes. We have set up a series of empirical parameters for the calculation of chemical shifts. The calculated results of 439 8 values from 78 compounds show that the standard deviation between the calculated and the experimental values is 0.08 ppm. The combination of this calculation with that of the coupling constants can be used to provide a criterion .for the determination of molecular structure in disubstituted naphthalenes as well as to assign NMR parameters for the experiment of proton simulated spectra of disubstituted naphthalenes. 相似文献
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《结构化学》1988,(3)
<正> The principle and Method for calculating the coupling constants of substituted benzenes have been extended to the calculation of coupling constants in disubstituted pyridines. The parameters 13 of some substi-tuents have been provided. The calculated results of 241 J values from 95 compounds show that the standard deviations between the calculated and the experimental values are within 0.11 Hz. 相似文献
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Abstract— Changes in light absorption in the region 450–540 nm were observed upon illumination of the red algae Iridaea splendens, Schizymenia pacifica and Porphyra perforata and the brown alga Pheostrophion irregulare . The difference spectra of these changes in Iridaea and Schizymenia showed maxima and minima at about 465, 480, 495, 515 nm. The spectra were similar to difference spectra earlier observed in photosynthetic bacteria, and the location of the maxima and minima suggested a shift towards longer wavelength of a compound with absorption maxima at about 440, 470, and 500 nm, probably a carotenoid. Similar, but more distorted difference spectra were observed in the other algae. Time courses and size of the signals induced by light of different wavelengths suggest that excitation of both photosynthetic pigment systems causes a shift in carotenoid absorption, with kinetics which appear to be similar to those of the well-known change at 515 nm in green plants. 相似文献
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Z. B. Maksicaccute K. Rupnik 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2)
Abstract The inner core binding energy shifts of sulphur atom in various chemical environments were studied by the semiempirical self-consistent charge molecular orbital method. The relaxation energy was taken into account by using two distinct approaches:(a) reorganizatinoo potential method and (b) transition potential method. The changes in ESCA chemical shifts of sulphur are satisfactorily accounted for by the latter method, the s tandard deviation from the experimental data being 0.2 eV. It appears that the reorganization energy plays an important role in rationlizing inner core binding energy shifts of sulphur. 相似文献
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Abstract— The excitation with a short flash of cells of a blue-green alga, Synechococcus sp., induced, besides photooxidation of cytochrome c -553 and P-700, small absorption changes of complex kinetics in the wavelength region between 450 and 570 nm. The absorption changes were resolved into two kinetic components different in their sensitivity to gramicidin D.
The ionophore-sensitive component (Gs), which rose very rapidly on flash illumination and decayed with a half-time of 3 ms, has spectral features indicating a red shift of carotenoid absorption bands. Gs was sensitive to valonomycin but not to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). The relaxation rate of Gs was markedly slowed down in the presence of tri- n -butyltin chloride. Phenazine methosulfate induced a secondary slow rise following the initial rapid rise. A similar slow rise appeared in the dark-starved cells but disappeared on the addition of methyl viologen. It is concluded from these results that Gs is an electrochromic band shift of carotenoid responding to the electric field formed by the primary charge separation of the photosystem I reaction center and its decay is related to the proton translocation through a proton channel of the membrane.
The ionophore-resistant component rose and decayed with the half-times of 0.2 and 2 ms, respectively. Its difference spectrum suggests a blue band shift of carotenoid. The ionophore-resistant component was also insensitive to DCMU. However, this component may be related in some way to flash-induced electron flow, because the photoresponse was altered by dibromothymoquinone, bathophenanthroline and 2- n -heptyl-hydroxyquinoline- N -oxide or the dark starvation of cells, which were all effective in inhibiting the cytochrome c -553 reduction. 相似文献
The ionophore-sensitive component (Gs), which rose very rapidly on flash illumination and decayed with a half-time of 3 ms, has spectral features indicating a red shift of carotenoid absorption bands. Gs was sensitive to valonomycin but not to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). The relaxation rate of Gs was markedly slowed down in the presence of tri- n -butyltin chloride. Phenazine methosulfate induced a secondary slow rise following the initial rapid rise. A similar slow rise appeared in the dark-starved cells but disappeared on the addition of methyl viologen. It is concluded from these results that Gs is an electrochromic band shift of carotenoid responding to the electric field formed by the primary charge separation of the photosystem I reaction center and its decay is related to the proton translocation through a proton channel of the membrane.
The ionophore-resistant component rose and decayed with the half-times of 0.2 and 2 ms, respectively. Its difference spectrum suggests a blue band shift of carotenoid. The ionophore-resistant component was also insensitive to DCMU. However, this component may be related in some way to flash-induced electron flow, because the photoresponse was altered by dibromothymoquinone, bathophenanthroline and 2- n -heptyl-hydroxyquinoline- N -oxide or the dark starvation of cells, which were all effective in inhibiting the cytochrome c -553 reduction. 相似文献
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Samuel O. Grim Anthony W. Yankowsky 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):191-195
Abstract The 31P chemical shifts of eleven (4-ZC6H4)3P compounds show a slight correlation with the Hammet [sgrave]para constant of Z. The unusually large upfield chemical shifts of (2-ZC6H4)3P compounds are attributed to an extreme “gamma” effect caused by the restricted conformations due to the steric influence of the ortho substituents. Chemical shifts are given for about thirty triarylphosphines, and group contributions to phosphine chemical shifts are listed for twenty-one aryl groups. 相似文献
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取代四苯基卟啉锌配合物与咪唑类和吡啶类等含氮化合物轴向配位反应的研究在模拟生物体中锌酶的作用机理方面具有重要意义。在现有的文献中 ,人们的研究主要集中在四苯基卟啉的苯环上连有如卤素、甲氧基、甲基等较小取代基的卟啉锌上[1~3] ,对于结构不对称且苯环上连有氨基酸的四苯基卟啉锌与含氮化合物轴向配位反应的研究尚不多见。有关尾式氨基酸四苯基卟啉锌配合物的合成和性质我们进行过较系统的研究[4~6] 。本文以 5 ( 4 甘氨酸丁氧苯基 ) 1 0 ,1 5 ,2 0 三苯基卟啉锌 (ZnP)为锌酶的模型化合物 ,用热力学方法研究了它与吡啶 (… 相似文献
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Abstract— The luminescence of freshly collected exudate from the post-cleithral organ of the deep-sea searsiid fish. Searsia koefoedi , was increased in intensity by the addition of hydrogen peroxide and exhibited emission maxima at 408 nm and 478 nm. Initially, the spectrum was unimodal with a long wavelength peak and a short wavelength shoulder. With time, the short wavelength peak increased in relative magnitude; the spectrum became bimodal, then the short wavelength peak predominated. The measured time-dependent changes in the spectral distribution resulted from differences in the rates of decay of the two peaks. The short wavelength peak exhibited first order exponential decay with a mean (± standard deviation) decay constant of -0.13 ± 0.02 min-1 ( N = 4). Decay of the long wavelength peak proceeded approximately twice as fast and was best defined by a double exponential function. 相似文献
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Minoru Sakurai Isao Ando Yoshio Inoue Riichirô Chûjô 《Photochemistry and photobiology》1981,34(3):367-374
Abstract— The carbon-13 NMR and UV absorption spectra of all- trans -retinal have been obtained as a function of dielectric constant of solvent. The chemical shift data have been analyzed by the CNDO/2 MO calculation with the 'solvaton' model and Pople's theory for carbon-13 shielding constant. It has been shown that the changes in chemical shifts are correlated with the electron densities on the corresponding carbon atoms. Considering this result, the ground state properties of all- trans -retinal have been discussed. An increase in the electronic charge alternation and a decrease in the bond alternation have been found along the polyene-chain with an increase of dielectric constant. The electronic structure of 11- cis -retinal has been compared with that of all- trans -retinal in solution. It is suggested that the solvent-induced red-shift of absorption maxima is caused by the π-electron derealization in the vicinity of the terminal oxygen atom. Finally, on the basis of these results, the environmental effect on the chromophore in rhodopsin has been discussed. 相似文献
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Thomas Glonek 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):235-238
Abstract For pure sodium polyphosphates, Na n + 2P n O3n + 1, exhibiting 3 through 6 phosphorus atoms per molecule, the 31P chemical shift of the middle group phosphorus atoms as measured in aqueous solution (0.1 M in P) at pH 7 was seen to increase with increasing magnesium ion concentration until there was one Mg atom per polyphosphate molecule, after which the chemical shift decreased. Finally the rate of decrease diminishes and precipitation occurs. For the longer-chain phosphates, Na n + 2P n O3n + 1 with n = 8, 9, 10, or an average of 100, as well as for the ring phosphates, Na n P n O3n for n ranging from 3 through 10, an increase in magnesium concentration simply leads to a decrease in chemical shift which diminishes at the higher concentrations. These data lend additional support to the concept that polymerized phosphate anions in solution exist in preferred conformations which depend on the nature of the counteraction. 相似文献
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Sueg-Geun Lee Wesley G. Bentrude 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2):219-222
Abstract A surprising linear downfield effect on the 31P chemical shift of a benzylphosphonate of deuterium substitution on the benzyl carbon has been noted. Its potential usefulness in mechanistic studies is suggested. 相似文献
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The correlation between ~(13)C chemical shifts of DNA and structure parameters (the mainaxis helix twist angle Ω, base--plane roll angle ρ, main chain torsion angle δ and pro-peller twist angle ω) has been discovered and proved indirectly. The carbons relating tothe structure parameters have been found and interpreted theoretically. Relative variationsin chemical shifts of these carbons obviously reflect purine-purine clash (steric hindrance)and have been compared with sum functions Σ of Calladine--Dickerson rules. It would bepossible to provide the information about conformation of DNA from ~(13)C NMR spectra andto observe the structure parameters of Ω,ρ,δ and ω of DNA in solution. 相似文献
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Abstract— Delayed light emission (measured 4 msec after excitation) and the light-induced red shifts of the bacteriochlorophyll and carotenoid absorption bands of chromatophores of Rhodopseudomonas spheroides were inhibited by a variety of reagents. These included anti-mycin A, NQNO, CCCP, desaspidin, quinacrine, chlorpromazine, 2,4-dinitrophenol, gramicidin D, Triton X-100 and valinomycin in the presence of potassium, cesium or ammonium ions. Delayed light emission was enhanced by orthophenanthroline, ethanol, succinate and glutathione.
Delayed light emission from chromatophores of Rhodospirillum rubrum was attenuated during photophosphorylation but restored approximately to its initial value in the presence of oligomycin. Since the delayed light and band shifts are inhibited under conditions which tend to deplete or block the formation of high energy phosphorylation intermediate, it is suggested that the presence of a high energy intermediate is a prerequisite for the appearance of each of the three phenomena. 相似文献
Delayed light emission from chromatophores of Rhodospirillum rubrum was attenuated during photophosphorylation but restored approximately to its initial value in the presence of oligomycin. Since the delayed light and band shifts are inhibited under conditions which tend to deplete or block the formation of high energy phosphorylation intermediate, it is suggested that the presence of a high energy intermediate is a prerequisite for the appearance of each of the three phenomena. 相似文献
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Per Ola Andersson Tomas Gillbro Linda Ferguson Richard J. Cogdell 《Photochemistry and photobiology》1991,54(3):353-360
Abstract–Solvent induced absorption spectral shifts of the electronic transition from ground 1 Ag state to the excited 1Bu state in carotenoids have been studied. It is shown that the shift depends only on dispersion interactions in non-polar solvents. In polar media there is just a small extra contribution to the red-shift, due to other forms of interactions. The spectral shifts are well described by the theory, which expresses the shift relative to the gas phase value, as a function of solvent polarizability. The main conclusion is that the dominating mechanism behind the large red-shifted absorbance of carotenoids in the proteinacous environment, in vivo, is the mutual polarizability interactions between the carotenoids and the surrounding medium. The solution-phase values of the dipole moments of the lAg to 1Bu transitions and the differences of isotropic polarizability between 1Bu and lAg states of carotenoids in non-polar solvents are calculated and found to be around 13 D and 360 Å3 respectively. From the great overlap of absorption spectra between carotenoids in quinoline and carotenoids in vivo in purple bacterial antenna complexes, it can be expected that the carotenoids are surrounded by several aromatic amino acids in vivo. Comparisons have been done between the exicted states in carotenoids and in linear conjugated polyenes. 相似文献
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