Chlorophyll polarized light

The degree of polarization of fluorescence after the absorption of polarized light can tell us whether the excitation has been transferred from one molecule to another. If the same chlorophyll molecules that absorbed polarized light later emit photons when they go back to the ground state, the... 

In contrast to the chlorophylls, which absorb light in two regions of the visible spectrum, the carotenoids exhibit intense absorption in just one, 350-500 nm. Figure E8.4 compares the absorption spectra of four common carotenoids. As with the chlorophylls, the absorption maxima of the carotenoids vary with polarity of the solvent. /3-Carotene in diethyl ether has a kmax of449.8 nm, but in the more polar acetone, the A.max is 454 nm. 

Selection of a suitable extraction procedure can increase the concentration of phenolic diterpenes relative to the plant material. In addition, undesirable components can be removed prior to adding extracts to foods. For example, chlorophylls present in plant material may reduce the light stability of food during storage. Several extraction techniques have been patented (Nakatani et al., 1984 Aeschbach and Philippossian, 1989) using solvents with different polarity, such as petrol ether, hexane, toluene, acetone, methanol and ethanol. To obtain tailored extracts, the successive use of different solvents has been applied. 

In order to observe the important structure-dependent anisotropic spin-spin interactions, such as the dipolar interaction, D, within radical pairs and to prevent spin lattice relaxation from destroying the spin polarization, it is necessary to examine the radical pairs in the solid state at low temperatures. Photosynthetic model systems based on chlorophyll or porphyrin electron donors have the interesting, but unfortunate property that the efficiency of their light-initiated, singlet state electron transfer reactions is negligibly low whenever they are dissolved in solid solutions. Stated more precisely, the decay rates of chlorophyll and porphyrin excited singlet states are much faster than the rates of electron transfer from these donors to most electron acceptors in the solid state. 

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