Ascorbic absorption spectrum

Fig. 6.2.4 Change in the absorption spectrum of pholasin (14.5 p,M) caused by the luminescence reaction catalyzed by Pholas luciferase (1.1 p.M). The curve shown is the differential spectrum between a cell containing the mixture of pholasin and Pholas luciferase (0.9 ml in the sample light path) and two cells containing separate solutions of pholasin and the luciferase at the same concentrations (in the reference light path), all in 0.1 M Tris-HCl buffer, pH 8.5, containing 0.5 M NaCl. Four additions of ascorbate (3 iM) were made to the sample mixture to accelerate the reaction. The spectrum was recorded after 120 min with a correction for the base line. From Henry and Monny, 1977, with permission from the American Chemical Society.

Figure 4.6 Infrared absorption spectrum of phosphomolybdenum blue solution (a) reduced with ascorbic acid and antimony (giving maximum absorbance at 882 pm), (b) reduced with tin(II) chloride, (c) reduced with ascorbic acid. Reprinted from Analytica Chimica Acta 27, Murphy, J. and Riley,...

The redox activity of Cyt c bound to the galleries of a-ZrP was found to be similar to that of the native protein. Dithionite or ascorbate can reduce Fe(IIII)Cyt c to the ferrous form, which can be oxidized by ferricyanide to the Fe(III) form. Retention of this redox property of Cyt c-a-ZrP is indicated by the absorption spectrum of Cyt c-a-ZrP. Although ascorbate and a-ZrP surface are both negatively charged, the addition of ascorbate to Cyt c-a-ZrP rapidly yields the reduced form of Cyt c (Fig. 49A). The absorption at 550 nm, due to Fe(II) form, grows with time and reaches a maximum value after 20 min. The addition of ferricyanide to Fe(II)Cyt c oxidizes it back to the Fe(III) form and restores the original absorption spectrum. These observations highlight the accessibility of bound protein to external small molecules and these immobilized proteins... 

Fig. 5-14. The visible absorption spectrum of ascorbate oxidase (curve 1) and in the presence of a substrate AH2 (curve 2). Reproduced with permission from Dawson (1960).

B. The infrared absorption spectrum of a potassium bromide dispersion of the sample exhibits maxima at the same wavelengths as those of a similar preparation of USP Ascorbic Acid Reference Standard. 

Absorption Spectra of the Metabolic Acids of Penicillium charlesii and Their Relationship to the Absorption Spectrum of Ascorbic Acid, R. W. Herbert and E. L. Hirst, Biochem. /., 29, 1881 (1935). 

Early work (21,22) on the absorption spectrum of the ascorbate radical failed to take into account the complex nature of the reaction between ascorbate and the OH radical, which was later shown by ESR studies (18,19) and by optical pulse radiolysis using very short pulses (23). 

The current best resolved absorption spectrum of the ascorbate anion radical (Figure 1) was determined (26) in a study of ascorbate oxidation by halide anion radicals (particularly Br2") at pH 11. The spectrum shows a symmetrical Gaussian-type band with an absorption peak at 360 nm and a width at half-maximum of about 50 nm. The molar absorbance at 360 nm = 3300 M cm" is lower than earlier reported values 21,23). 

Figure 1. Absorption spectrum of the ascorbate radical anion at pH 11.0...

The ascorbate radical has been generated in aqueous solution in order to study its u.v. absorption spectrum using the technique of pulse... 

Fig. 2. The absorption spectrum of cytochrome br in pigeon heart mitochrondria at 77°K (IS). The mitochondria were suspended in a medium containing 0.225 M mannitol, 0.07 M sucrose, 0.2 rciM EDTA, and 60 mM Tris-HCl, pH 7.4, and supplemented with 2.5 tiM rotenone, 5 mM KCN, 5 mM ascorbate, 80 itM TMPD, and 5 mM succinate. The suspension was injected into the reference cuvette which had been precooled to 77°K. The suspension was similarly transferred into the measure cuvette after further addition of 1.2 mM ATP.

FIG 1. A) Absorption spectra of isolated RC complex at 4 K (solid line) and at 300 K (dot dash line). Inset is an expansion of the 790 nm peak (solid line) with its 4th derivative (dashed line). B) Absorption spectrum of the 16 kDa cytochrome. Solid line is with no additions and dot dash line is with added ascorbate. 

Fia. 5. Changes in the absorption spectrum of oxyhemoglobin brought about by ascorbic acid (Riedesel and Watts, 1952). All solutions except the original oxyhemoglobin were stored for 3 hours at 46° C. (113° F.) before reading. 

D. Oxyhemoglobin plus 0.02% nitrite and 0.1% ascorbic acid. Typical absorption spectrum of nitric oxide hemoglobin. Bright red. 

FIGURE 118.3 Absorption spectrum of a suspension of Rhodopseudomonas viridis reaction centers (plus 100 pM Na ascorbate) dispersed by a detergent (LDAO). The absorption band at 970 nm is due to the primary donor P, and the large massif around 820 nm is mainly due to the two bacteriochlorophylls other than P, and to the two bacteriopheophytins. (Reaction centers kindly provided by Dr. J. Breton.)... 

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