. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. VOL. 12 (1953) CO COMPOUNDS OF RESPIRATORY ENZYMES 295 In order to demonstrate that our method for measuring the photodissociation spec- trum gives a result that agrees accurately with the actual absorption spectrum, we compare in Fig. 7 the spectrum obtained by subtracting the ferromyoglobin-CO spec- trum from that of ferromyoglobin (Beznak^^) with a photodissociation spectrum ob- tained with this apparatus. The agreement of the data shows that
. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. VOL. 12 (1953) CO COMPOUNDS OF RESPIRATORY ENZYMES 295 In order to demonstrate that our method for measuring the photodissociation spec- trum gives a result that agrees accurately with the actual absorption spectrum, we compare in Fig. 7 the spectrum obtained by subtracting the ferromyoglobin-CO spec- trum from that of ferromyoglobin (Beznak^^) with a photodissociation spectrum ob- tained with this apparatus. The agreement of the data shows that the photodissociation method gives nearly as accurate results as the direct measurement of the absorption spectra. It should be noted that exact coincidence of the peaks of the absorption photodisso- ciation difference spectra with those of the relative photochemical action spectra is not to be expected. Fig. 7 (Curve A) clearly shows that for protohemin pigments the peak of the difference spectrum lies rufx below that of the absolute spectrum and, in the case of the dichroic hemin enzyme lactoperoxidase, the displacement is m/i,^^. Thus the displacement is small, but significant. 240 n 180 1 160 c a> E <u g 120 a. O 80 40 Reduced + CO Oxidized. Reduced 400 420 440 A 460 - + 1 E J \ Reduced u c / y + J ^° 0) E c 0- / \ Reduced ^ â U u» c s \ â¢/ â 5 0 ^ \"j 420 440 460 B 480 Fig 7. (A), the oxidized, reduced, and reduced-CO spectra for myoglobin (from Beznak^^) and (B), (open circles), the difference spectrum of the CO compound. Solid circles of (B) show experimental data on the photodissociation spectrum of myoglobin-CO obtained by the method of Fig. 4. In order to facilitate the comparison, the ordinates of the photodissociation curve were multiplied by a constant factor to cause the two sets of data to match at the peak of the curve (i fiM Mgb, pH = , fiM CO) (Expt. 143a). Calculation of the molecular extinction coefficients
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