Difference absorption spectrum

Increasing the initial concentration of zeaxanthin to 10 4 M, Figure 8.6b, produces a different dependence on the ethanol/water ratio. Under these initial conditions, adding water to a final ethanol/water ratio of 3 2 leads to a distinctly different absorption spectrum than that observed at lower initial concentration. The vibrational structure of the S2 state is preserved and a new absorption band characteristic of J-aggregates appears at 530 nm. When the water content was increased... 

FIGURE 12.4 Lycopene photodegradation in 0.02 M Triton X-100 aqueous solutions illuminated with a 150 W (> 380 nm) filament lamp. Inset evolution of the difference absorption spectrum (AA). 

Figure 4b shows the measured transient difference absorption spectrum as a function of the x-ray probe energy E, recorded 50 ps after laser excitation (data points with error bars) for a sample containing 80 mmol/1 solution of [Ru"(bpy)3]2+ in H2O. This transient contains all the electronic changes from the reactant state absorption spectrum, R E), to the product state absorption spectrum, P(E,t), at the time t after photoexcitation. WithXO being the fraction of excited state species at time t, the transient absorption spectrum T(E,t) is given by... 

The absorption spectrum of nitrocellulose solutions has been examined (Rassow and Aehnelt [135]). It has been established that the capacity to absorb light differs with the origin of the nitrated cellulose. Thus nitrocellulose made from wood pulp gives a slightly different absorption spectrum from that of nitrocotton. 

From Rayleigh and schlieren optics, one could calculate cMwa, and hence one could calculate A (cMwa) at every r in the solution column of the ultracentrifuge cell and use the analysis used with the other methods (see Equation 76 and the discussion following it). This could also be done even if only one of the reactants had an absorption spectrum, since c = cA° + cB°. The other possibility is that the complex AnBm has a different absorption spectrum from the reactants, or that in the formation of AnBw some chromophoric groups are buried so that the absorbance of A and B represents a quantity proportional to cA and cB. In either case one could then calculate... 

Figure 2. The difference absorption spectrum of bleached TMP has maxima at 350 nm and 420 nm. The specific absorption at these wavelengths increases with increasing time of irradiation shown in brackets as the number of hours (Adapted from ref. 10).

The crystal structures of transition metal compounds and minerals have either cubic or lower symmetries. The cations may occur in regular octahedral (or tetrahedral) sites or be present in distorted coordination polyhedra in the crystal structures. When cations are located in low-symmetry coordination environments in non-cubic minerals, different absorption spectrum profiles may result when linearly polarized light is transmitted through single crystals of the anisotropic phases. Such polarization dependence of absorption bands is illustrated by the spectra ofFe2+ in gillespite (fig. 3.3) and of Fe3+in yellow sapphire (fig. 3.16). 

Figure 1. Reduced-minus-oxidized difference absorption spectrum of Ps. aeruginosa azurin. Sample and reference cell contained 6.8 X 10 5 M solutions of reduced and oxidized protein, respectively. Hydrogen, with platinum black as catalyst, was used as reductant (1). Medium ...

Fig. 4. (A) The absorption spectra (bottom) and circular-dichroism spectra (top) of the reaction center from Rb. sphaero/des with P870 reduoed (soiid curve) or oxidized (dashed curve), (B) shows the corresponding difference CD spectrum (top) and the difference absorption spectrum (bottom). Figure source Reed and Ke (1973) Spectral properties of reaction center preparations from Rhodopseudomonas sphaeroides. J Bioi Chem. 248 3042.

Fig. 4. Difference absorption spectrum of photoreduced bacleriopheophytin (B

Acridine has been studied by means of the echelon technique.(24,25) The changes in absorption (AA) were measured with a double beam picosecond spectrometer similar to the one shown in Figure 3. The difference absorption spectrum at one selected delay time after excitation was calculated according to... 

The resulting ferrous complex is characterized by a difference absorption spectrum with maxima at 427 and 455 nm, whereas the ferric complex exhibits a single absorption maximum at 437 nm ° - The ferrous peaks at 427 and 455 nm are due to distinct complexes, although their structural interrelationship is obscure . The ferrous complex can be isolated intact from animals treated with isosafrole, demonstrating its stability, but the less stable ferric complex can be disrupted by incubation with lipophilic compounds with concomitant regeneration of the catalytically active enzyme The ferrous complex is unaffected by incubation with lipophilic compounds but can be disrupted by irradiation at 400-500 nm o, 211 structure activity studies of 4-alkoxy-l,2-methylenedioxybenzene reveal that the size and lipophilicity of the alkoxy group is an important determinant of the complex... 

Cations with the xanthyl backbone have been the subject of considerable photochemical study and have been generated by each of the techniques described in the previous section. The xanthyl cations studied include those with 9-alkyl (R = Me, c-Pr, i-Pr, and r-Bu) and 9-aryl (aryl substituent = H, p-F, m-F, p-Me, m-Me, /n-OMe, and p-OMe) substituents, as well as the parent xanthyl cation. The xanthyl cation exhibits a characteristic absorption spectrum, with maxima at 260, 370, and 450 nm, invariant with the different alkyl or aryl substituents, and with the various techniques and media used for cation generation [6-8,10-15,24,28,32,33]. Only the p-OMe-substituted cation exhibits a different absorption spectrum, with the long-wavelength band less well resolved and shifted to 500 nm [13]. 

A tliird byproduct from citrus processing is citrus molasses (CM). CM is obtained from tlie spent citrus peel after the juice and peel oils are extracted The peels are furtlier processed to squeeze out residual juice sugars and peel oils. This mixture is concentrated by distillation wliich removes water and many of the volatile oil components present. A sample of 33 Brix orange molasses was analyzed for PMF content to compare with our other results. The HPLC spectrum (Figure 6) shows a very different absorption spectrum from the typical juice sample. A large (unidentified) peak is seen eluting before 2.5 minutes with the PMF peaks eluting later. The total PMF content in this... 

The observed absorbance (AA) after an electron pulse is given to the solution containing quinone and a suitable additive, will constitute a difference absorption spectrum given by ... 

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