Visible-region spectra

Fig. 14. Effects of temperature on the absorbance of hemopexin and the N-domain of hemopexin. The unfolding of hemopexin and N-domain in 25 mM sodium phosphate, pH 7.4, was examined using absorbance spectroscopy (N. Shipulina et al., unpublished). The second derivative UV absorbance spectra of the protein moieties were used to follow protein unfolding and the Soret and visible region spectra to monitor the integrity of the heme complexes, as done with cytochrome 6502 (166). The ferri-heme complex is more stable than the apo-protein moiety, but the is slightly lower than that assessed by DSC, indicating that changes in conformation occur before thermodynamic unfolding. Reduction causes a large decrease in heme-complex stabihty, which is proposed to be a major factor in heme release from hemopexin by its cell membrane receptor, and addition of 150 mM sodium chloride enhanced the stabihty of ah forms of hemopexin.

Figure 5. Near ultraviolet to visible region spectra of kaolinite, pyrophyllite, and saponite showing an absorption band near 40,000 cm"1 due to 02"- Fe3+ charge transfer. (Data from reference 25).

Figure 5.22 Polarized absorption spectra of iron in plagioclase feldspar (from Hofmeister Rossman, 1983). (a) Visible region spectra with peaks originating from Fe3+ ions in tetrahedral coordination (b) near-infrared spectra attributed to Fe2+ ions in the Ca sites. The labradorite, from Rabbit Hills, Oregon, contains about 0.1 wt per cent Fe203 and 0.3 wt per cent FeO. (Crystal thickness 1.0 cm.)...

Visible-region spectra, which are the principal source of CFSE data for transition metal ions, also provide a measure of relative covalent bonding interactions of cations in host structures and enable estimates to be made of changes... 

Loeffler, B. M., Bums, R. G. Tossell, J. A. (1975) Metal-metal charge transfer transitions interpretation of visible-region spectra of the moon and lunar materials, Proc. 6th Lunar Sci. Confi, Geochim. Cosmochim. Acta, Suppl. 6. (Pergamon Press, New York), pp. 2663-76. 

Figure 12 The reaction between the cyanide complex of ferric myoglobin (horse heart) and sodium dithionite. A subset of the total number of spectra collected is shown. An initial increase in absorbance is seen at 435 nm and in the visible region, spectra displayed every 20 ms, followed by a slower decrease, only the final spectrum (thicker line) is shown for clarity.

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