= Hill reaction
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The <Hill reaction> couples <light>-driven <Electron> transfer from <water> to an added <electron acceptor> with <molecular oxygen> release in an isolated photosynthetic preparation. The <chloroplast dye-reduction experiment> uses <DCPIP>.<Investigating the light dependent reaction in photosynthesis at Practical Biology>[Investigating the light dependent reaction in photosynthesis, introductory and Teaching notes: artificial acceptor assay]{ref}
In 1937, <Robin Hill>'s Oxygen Evolved by Isolated Chloroplasts described a spectroscopic <molecular oxygen> measurement in illuminated isolated <chloroplasts>: oxygenation of muscle <hemoglobin> provided the indicator. This was an oxygen-binding readout. The publicly accessible first paragraph establishes that method; it does not specify enough preparation or control details to reconstruct the entire historical experiment here.<Oxygen Evolved by Isolated Chloroplasts by Robin Hill>[Hill, Nature 139, 881–882 (22 May 1937), public first-paragraph preview: hemoglobin oxygenation and spectroscopic saturation measurement]{ref}
The experimental idea is powerful because isolation asks how much of <photosynthesis> remains functional outside an intact <biological cell>. Breaking a <chloroplast envelope> does not logically imply destroying every internal <thylakoid membrane>. Conversely, finding an active preparation cannot establish that its <chloroplast envelope> remains intact. Activity and structural integrity require different evidence.
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