Hydroxyl emission spectrum

The function of the spectrometer is to accept as much light from the source as possible and to isolate the required spectral lines. This may be impossible where there is a continuous spectrum in the same region as the analytical line for example, the magnesium line of 286.2 nm coincides with a hydroxyl band. In direct reading instruments, electronic devices may be used to supplement the resolution of the spectrometer by modulating the intensity of the analytical signal. In absorption and fluorescence the light source is modulated in emission the spectral line is scanned (816) or the sample flow modulated (M23). 

UV at 248 and 278 nm, and sets of narrow bands centered at about 488 and 615 nm (Mitchell et al. 1997) yielding a brick-red emission color. Natural samples of hydroxyl-apatite and fluorapatite show similar CL bands (Gaft et al. 1999). Time-resolved emission spectra (Fig. 19) show well defined Pr emission in natural magmatic apatite at 485 and 607 nm (Gaft et al. 1999). Studies using polarized emission measurements on this sample were interpreted as representative of only Cal site occupation by Pr (Reisfeld et al. 1996). In contrast, a sedimentary apatite annealed in air showed a different Pr spectrum, with a set of bands centered at about 630 nm (Fig. 19). This spectrum was interpreted to be due to Pr in Ca2 (Reisfeld et al. 1996). Pr appears to be an efficient sensitizer for Sm, as many of its transition energies are almost identical to Sm, and in general Pr probably is more important as a sensitizer of other REE than for its own emission (Mitchell et al. 1997). 

The existence of the hydroxyl radical as a separate. If transient, entity was first recognized in 1924 by Watson (19), who proposed that the water vapor bands emitted by flames and electric discharges In moist air were due to the OH radical, and not to excited H2O. In 1928 Bonhoeffer and Relchardt (20) obtained the absorption spectrum of the OH radical in partially dissociated water vapor at v>1873°K, and In 1935 Oldenberg (21) was able to follow the decay of the radical In the products flowing from an electric discharge through water vapor. This latter work was of Importance since the OH radical could then be monitored In a system applicable to kinetic studies. Early combustion studies showed that the hydroxyl radical Is also an Important constituent of flames, the most prominent feature of flame spectra (22) being emission from the (a2i + - X Il) band system of the OH radical. 

DNA fragment an excess of tetranucleotlde was present In solution (0.30 mM protein versus 0.46 mM d(pC-G-C-G). To exclude the possibility that the flavin dye Is rendered Inactive by the presence of the tetranucleotlde extra N-ace-tyl tyrosine (0.28 mM) was added to the solution. Under these conditions the emission signal of a free tyrosine appears In the CIDNP difference spectrum (Fig. 6D). This observation makes an Inactivation of the flavin dye by the presence of the tetranucleotlde very unlikely. In a separate experiment it was shown that the tetranucleotlde does not show any CIDNP effects. Thus the experiments presented in Fig. 6 demonstrate that upon binding of the tetranucleotlde the hydroxyl groups of the tyrosines 26, 41 and 56 are no longer available for reaction with the flavin dye. This we interprets to mean that these tyrosines are Involved in the protein-DNA interaction. The present re-... 

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