. Biological structure and function; proceedings. Biochemistry; Cytology. 98 F. A. HOLTON AND D. D. TYLER incubation with phosphate and succinate (Fig. i). Addition of magnesium chloride does not alter this configuration (Fig. 2), but it activates a power- ful ATPase [5] which can hydrolyze newly synthesized ATP at least as ⺠002 + 001. 50 100 150 External ADP concentration /i. Molar Fig. 3. Relationship between the concentration of externally added ADP and the resultant extinction changes measured simultaneously at three separate wave- lengths in a suspension of heart mitochondria in the pre
. Biological structure and function; proceedings. Biochemistry; Cytology. 98 F. A. HOLTON AND D. D. TYLER incubation with phosphate and succinate (Fig. i). Addition of magnesium chloride does not alter this configuration (Fig. 2), but it activates a power- ful ATPase [5] which can hydrolyze newly synthesized ATP at least as ⺠002 + 001. 50 100 150 External ADP concentration /i. Molar Fig. 3. Relationship between the concentration of externally added ADP and the resultant extinction changes measured simultaneously at three separate wave- lengths in a suspension of heart mitochondria in the presence of magnesium ions. Data of Fig. 2 graphed, with addition of results relating to later additions of ADP and also from simultaneous observations at 434 m/x. The changes of extinction caused by ADP clearly did not obey Rayleigh's law, since for any given concentration of ADP they did not decrease regularly with increasing wavelength of observation. The data suggests that a minor part of the extinction changes observed was due to an alteration in the extinction due to pig- ments as ADP was added. They are consistent with the hypothesis that the states of oxidation of both cytochrome b and flavoprotein were moved in the direction of oxidation by addition of ADP, an eifect to be expected from the work of Chance and Baltscheffsky [12]. If it is assumed that there was no contribution of pigments to the extinction changes recorded at 450 m/x, it is possible to calculate for the other two wavelengths of observation values of the ratio extinction change due to light scattering extinction change due to pigment For observations at both 434 m^i and 477 â 5 m/Lt the above data give a value of 3 -4 for the above ratio. This value may be compared with that from the work of Chance and Packer [13], who added ADP to a suspension of rat heart sarcosomes and deduced a value of about 4 for the same ratio. (In their work the extinction change due to scattering was equated to that observed at
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