Fluorescence emission spectra methanol with

The bioluminescence spectrum of P. stipticus and the fluorescence and chemiluminescence spectra of PM are shown in Fig. 9.7. The fluorescence emission maximum of PM-2 (525 nm) is very close to the bioluminescence emission maximum (530 nm), but the chemiluminescence emission maximum in the presence of a cationic surfactant CTAB (480 nm) differs significantly. However, upon replacing the CTAB with the zwitter-ionic surfactant SB3-12 (3-dodecyldimethylammonio-propanesulfonate), the chemiluminescence spectrum splits into two peaks, 493 nm and 530 nm, of which the latter peak coincides with the emission maximum of the bioluminescence. When PM-1 is heated at 90°C for 3 hr in water containing 10% methanol, about 50% of PM-1 is converted to a new compound that can be isolated by HPLC the chemiluminescence spectrum of this compound in the presence of SB3-12 (curve 5, Fig. 9.7) is practically identical with the bioluminescence spectrum. 

The synthetic alkaloid coralyne (Scheme 1) on the other hand is a planar molecule and is not readily soluble in aqueous buffers. It is highly soluble in ethanol and methanol. Coralyne is characterized by strong absorption maxima at 219, 300, 311, 326 and 424 nm with characteristic humps at 231, 360 and 405 nm in 30% (v/v) ethanol. It is highly fluorescent and gives an emission spectrum with a maximum at 460 nm when excitation was done either at 310 or 424 nm. It was observed that both absorbance and the fluorescence pattern of coralyne remained unaltered in buffer of various pH values ranging from 1.0 to 13.0 and also with salt concentration ranging from 4.0 to 500 mM. This implied that hydrophobic environment favoured the increment of their fluorescence properties [144]. 

With spectroscopic methods it is possible to obtain information about the conformation of hydrocarbon-DNA complexes. The fluorescence quantum yields of aromatic hydrocarbons are greatly reduced when they bind to DNA in intercalated conformations. Figure 3 shows how the intensity of the emission spectrum of DMA decreases with increasing concentrations of DNA in 15% methanol. (In Figure 3 and throughout this discussion DNA concentrations and association constants have been reported in terms of PO molarity unless otherwise indicated. The solution content of organic solvents is given in percent volume.)... 

In methanol/DMSO solvent mixtures the fluorescence spectrum of TIN (A.max = 400 nm) displays a normal Stokes shift indicating that this emission arises from a non proton-transferred, excited state of TIN. The fluorescence excitation spectrum for this emission coincides with the absorption spectrum of the resolved non-planar species suggesting that this conformer is the ground-state precursor responsible for the observed emission. As the amount of DMSO in the mixture increases the fluorescence maximum undergoes a bathochromic shift from 415 nm in pure methanol to 440 nm in pure DMSO. 

In addition to a fluorescence perturbation, the Cd(II)-5d combination also uniquely yields aperturbation in the ultraviolet (UV) spectrum. A difference spectrum obtained by subtracting a fractional amount of an uncomplexed 5d spectrum from the perturbed spectrum is the mirror image of a fluorescence difference spectrum obtained by similar means. Moreover, excitation at 400 nm (where 1-4 are weakly absorbing but where moderate absorption is seen in the difference spectrum) gives rise to an emission spectrum with identical shape and Amax (456 nm) to that of the fluorescence difference spectrum. Thus, evidence points to the existence of two equilibrating ground state species as the physical basis for the chelatoselective emission. Bouas-Laurent has reported a related observation in methanol where a red-shifted CHEF was observed for a T1(I) 7r-complex.(14)... 

A methanol solution containing poly(3) exhibits abroad absorption band with A,max at 422 nm. In aqueous solution, the absorption maximum red-shifts to 432 nm and the absorption coefficient also decreases. The emission properties are greatly dependent upon the nature of the solvent. In a methanol solution, poly(3) exhibits a narrow emission band with A.max = 475 nm and a vibronic band at A,max = 502 nm. In aqueous solution, the emission band becomes broader and the fluorescence quantum yield (Ofi =0.016) is lower than that in methanol ( fi = 0.045). Interestingly, the emission maximum is at the same position as in methanol (475 nm) with a shoulder at 502 nm. Such behaviour is different from other PPE-based CPE, which exhibit large red-shifts of emission band in a poor solvent. The lack of a spectral shift for poly(3) is likely to be due to the fact that the aggregated state of the polymer has a much lower quantum yield, and therefore its contribution to the total emission spectrum is small. 

Among the most commonly used fluorescent probes for biochemical and biological systems are l-dimethylamino-5-sulfonamidonaphthalenes (DNS derivatives) (SCHEME IV). The emission spectrum of the model compound l-dimethylamino-5-(S-isobutyroyl-aminoethyl)sulfonamidonaph-thalene (IB DNS) in absolute methanol is characterized by one band with an emission maximum at 538 nm which corresponds to the excited state of IB DNS, with a nonprotonized dimethylamino group. The emission spectrum was independent on the exciting radiation for wavelengths from 250 to 380 nm. 

The fluorescence spectrum of diloxanide furoate in aqueous methanol (concentration of 8 pg/mL) was recorded using a Perkin Elmer NPF-44B fluorimeter system. As shown in Figure 4, the excitation maximum was noted at 240 nm, which agrees well with the absorption maxima observed in the UVA IS studies. The emission maximum was found at 335 nm. 

The effects of the mixed supersonic expansion of CDMA with various solvent molecules (such as cyclohexane, carbon tetrachloride, acetone, acetonitrile, methanol, dichloromethane and chloroform) on the emission spectra have been investigated by Phillips and co-workers [82d[. The cluster size distribution was varied by changing the nozzle temperature and the partial pressure of the solvent. Two emission components were observed in each case. The long-wave emission was attributed to dimers (which can be isolated or solvated) and to monomer complexed with chloroform or dichloromethane (of unknown stoichiometry). On the other hand, it has been reported by Bernstein and co-workers [84] that CDMA forms with acetonitrile two kinds of 1 1 complexes of different geometry. The first cluster has a structured excitation spectrum, similar to that of the bare molecule, but blue shifted by about 252 cm . The second exhibits a broad excitation spectrum with some resolvable features between 31400 and 31 600 cm (Table 2). The complexes show different fluorescence spectra excitation into the broad absorption leads to the red-shifted emission with respect to that of the monomer (Figure 8) and of the blue ... 

Fluorescence spectra from a polystyrene film photolyzed in vacuum are shown in Figure 2. Similar but less intense spectra were observed in films irradiated in air. The Product I responsible for this spectrum was partially extractable from the film with methanol the fluorescence spectrum of the extract is shown also in Figure 2. Comparison of these spectra with those of a wide variety of reasonable model compounds suggests that Product I is related to 1,3-diphenyl-l,3-butadiene since the spectral match with 1,4-diphenyl-l,3-butadiene, shown in Figure 2, is quite close. Product I spectra were obtained also from the residual films after extraction, indicating that the diene moiety may form part of a photolyzed chain as well as exist as a short-chain fragment. Fluorescence spectra that could be related to higher polyenes were not detected in the vacuum exposures. In air exposures, however, the prompt emission spectra from films did exhibit a weak shoulder superimposed on the... 

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