The molecular processes taking place during triplet‐triplet annihilation (TTA) in solvents at roo... more The molecular processes taking place during triplet‐triplet annihilation (TTA) in solvents at room temperature are examined in detail. Special attention is paid to modelling of the nonlinear kinetic reactions. Using time‐ and spectrally resolved spectroscopy of DPA and Pt/Pd‐OEP based sensitizer and annihilators, it is shown how the kinetic of parameters, such as the triplet energy transfer (TET) and TTA of the rate‐reactions, can be simulated, measured and fitted, without approximations, using a numerical scheme. Studies of DPA in the solvents DMSO, THF and toluene at room temperature revealed that viscosity/diffusion together with the excited triplet lifetime of the annihilator are the most crucial parameters for high TTA induced delayed fluorescence. From an analysis of the experimentally determined rates an efficiency of 16–40 % was determined for the combined TET and TTA processes using THF, DMSO and toluene as solvents. (DPA=9,10‐diphenylanthracene, OEP=2,3,7,8,12,13,17,18‐octaethyl‐21H,23H‐porphyrin)
Fluorescence studies were performed on the extrusions from pilosebaceous follicles. Pressure extr... more Fluorescence studies were performed on the extrusions from pilosebaceous follicles. Pressure extractions produced follicle samples which showed fluorescence under Wood's light. The samples were then analysed in a fluorometer giving corrected excitation spectra. The structured emission spectra achieved were interpreted as being due to porphyrins produced by Propionibacterium acnes (P. acnes). Details in the spectra showed close resemblance to spectra from cultured P. acnes cells. The emission spectra showed distinct features in all the four subjects investigated (who were different with respect to age, sex, follicle sampling area, and tendency to acne) and dominant peaks due to at least three porphyrins were found. The concentrations of these porphyrins vary from case to case. Excitation spectra were recorded and supported the assumption that the fluorescent emission was partly due to coproporphyrins and metalloporphyrins in the samples. Free protoporphyrins did not seem to be present in the extrusions. The excitation spectra, in particular, vary from person to person but seem to be constant over time in one and the same subject.
For investigations of ongoing processes in plants, such as photosynthesis in conifer leaves, nond... more For investigations of ongoing processes in plants, such as photosynthesis in conifer leaves, nondestructive and noninvasive measuring techniques are needed. In this paper, a novel approach has been developed for the measurement of chloroplasts’ numbers and pigment contents in conifer leaves based on the measurements of leaf absorption spectra using optical fibers and an array spectrophotometer. To eliminate the effect of scattering on the measured absorption spectra, a strategy has been applied taking advantage of the combined use of thin optical fibers normal to the needle's longitudinal axis and the phenomenon that scattering is largest in the forward direction. The optical path in the leaf is nearly the distance between the fiber tips; thus, we were able to obtain the absorption spectrum of the pigments in situ. A effect of the measured absorption spectra, occurring due to the organization of pigments in the leaf and interaction between light and leaf interior, can be accounted for by using the so-called Duysens transformation. Using this transformation, pigment contents and the relative number of chloroplasts can be obtained from the measured absorption spectra. We applied the method to observe pigment concentrations in different stages of the greening process in the leaves of two conifer species, Taxus baccata and Picea abies. The presented method may be used to estimate changes in chloroplast number and pigment content during various phases of greening of a species and to observe differences among various species.
The secondary processes, initiated by irradiation, taking place in a single crystal of pimelic ac... more The secondary processes, initiated by irradiation, taking place in a single crystal of pimelic acid have been investigated by an electron spin resonance technique. At 77 K only the ĊOOH and ĊH2(CH2)4COOH radicals remain. Upon increasing the temperature the latter radical dissociates into short-lived products, and one of these products immediately captures a hydrogen atom from a neighbouring undamaged molecule, leaving a radical HOOCĊH(CH2)4COOH. This radical then captures a hydrogen atom from another undamaged molecule, probably because it is brought somewhat out of its lattice equilibrium position.
Journal of Photochemistry and Photobiology B-biology, May 1, 1991
Suspensions of Propionibacterium acnes were UV irradiated and the induced radicals were measured ... more Suspensions of Propionibacterium acnes were UV irradiated and the induced radicals were measured at 77 K by electron spin resonance (ESR) spectrometry. Two types of radical were formed during irradiation and stabilized in the frozen suspensions. The relative yield of each radical was studied as a function of irradiation wavelength. The first radical, which was a singlet with a peak-to-peak width of 20 G, was insensitive to the deoxygenation of the samples and to the exchange of solvent water by heavy water. The action spectrum was similar to the absorption spectrum of NADPH. The second type of radical was not formed in deoxygenated samples and the shape of the ESR spectrum was characteristic of the superoxide radical. This radical was only formed at wavelengths below 340 nm.
The molecular processes taking place during triplet‐triplet annihilation (TTA) in solvents at roo... more The molecular processes taking place during triplet‐triplet annihilation (TTA) in solvents at room temperature are examined in detail. Special attention is paid to modelling of the nonlinear kinetic reactions. Using time‐ and spectrally resolved spectroscopy of DPA and Pt/Pd‐OEP based sensitizer and annihilators, it is shown how the kinetic of parameters, such as the triplet energy transfer (TET) and TTA of the rate‐reactions, can be simulated, measured and fitted, without approximations, using a numerical scheme. Studies of DPA in the solvents DMSO, THF and toluene at room temperature revealed that viscosity/diffusion together with the excited triplet lifetime of the annihilator are the most crucial parameters for high TTA induced delayed fluorescence. From an analysis of the experimentally determined rates an efficiency of 16–40 % was determined for the combined TET and TTA processes using THF, DMSO and toluene as solvents. (DPA=9,10‐diphenylanthracene, OEP=2,3,7,8,12,13,17,18‐octaethyl‐21H,23H‐porphyrin)
Fluorescence studies were performed on the extrusions from pilosebaceous follicles. Pressure extr... more Fluorescence studies were performed on the extrusions from pilosebaceous follicles. Pressure extractions produced follicle samples which showed fluorescence under Wood's light. The samples were then analysed in a fluorometer giving corrected excitation spectra. The structured emission spectra achieved were interpreted as being due to porphyrins produced by Propionibacterium acnes (P. acnes). Details in the spectra showed close resemblance to spectra from cultured P. acnes cells. The emission spectra showed distinct features in all the four subjects investigated (who were different with respect to age, sex, follicle sampling area, and tendency to acne) and dominant peaks due to at least three porphyrins were found. The concentrations of these porphyrins vary from case to case. Excitation spectra were recorded and supported the assumption that the fluorescent emission was partly due to coproporphyrins and metalloporphyrins in the samples. Free protoporphyrins did not seem to be present in the extrusions. The excitation spectra, in particular, vary from person to person but seem to be constant over time in one and the same subject.
For investigations of ongoing processes in plants, such as photosynthesis in conifer leaves, nond... more For investigations of ongoing processes in plants, such as photosynthesis in conifer leaves, nondestructive and noninvasive measuring techniques are needed. In this paper, a novel approach has been developed for the measurement of chloroplasts’ numbers and pigment contents in conifer leaves based on the measurements of leaf absorption spectra using optical fibers and an array spectrophotometer. To eliminate the effect of scattering on the measured absorption spectra, a strategy has been applied taking advantage of the combined use of thin optical fibers normal to the needle's longitudinal axis and the phenomenon that scattering is largest in the forward direction. The optical path in the leaf is nearly the distance between the fiber tips; thus, we were able to obtain the absorption spectrum of the pigments in situ. A effect of the measured absorption spectra, occurring due to the organization of pigments in the leaf and interaction between light and leaf interior, can be accounted for by using the so-called Duysens transformation. Using this transformation, pigment contents and the relative number of chloroplasts can be obtained from the measured absorption spectra. We applied the method to observe pigment concentrations in different stages of the greening process in the leaves of two conifer species, Taxus baccata and Picea abies. The presented method may be used to estimate changes in chloroplast number and pigment content during various phases of greening of a species and to observe differences among various species.
The secondary processes, initiated by irradiation, taking place in a single crystal of pimelic ac... more The secondary processes, initiated by irradiation, taking place in a single crystal of pimelic acid have been investigated by an electron spin resonance technique. At 77 K only the ĊOOH and ĊH2(CH2)4COOH radicals remain. Upon increasing the temperature the latter radical dissociates into short-lived products, and one of these products immediately captures a hydrogen atom from a neighbouring undamaged molecule, leaving a radical HOOCĊH(CH2)4COOH. This radical then captures a hydrogen atom from another undamaged molecule, probably because it is brought somewhat out of its lattice equilibrium position.
Journal of Photochemistry and Photobiology B-biology, May 1, 1991
Suspensions of Propionibacterium acnes were UV irradiated and the induced radicals were measured ... more Suspensions of Propionibacterium acnes were UV irradiated and the induced radicals were measured at 77 K by electron spin resonance (ESR) spectrometry. Two types of radical were formed during irradiation and stabilized in the frozen suspensions. The relative yield of each radical was studied as a function of irradiation wavelength. The first radical, which was a singlet with a peak-to-peak width of 20 G, was insensitive to the deoxygenation of the samples and to the exchange of solvent water by heavy water. The action spectrum was similar to the absorption spectrum of NADPH. The second type of radical was not formed in deoxygenated samples and the shape of the ESR spectrum was characteristic of the superoxide radical. This radical was only formed at wavelengths below 340 nm.
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