Ian George Bridges

Intracellular compartmentation detected by 31P-NMR in intact photosynthetic wheat-leaf tissue

Abstract High-resolution 31P-NMR spectra of wheat-leaf tissue have been obtained. Local variations in bulk magnetic susceptibility in the tissue make direct observation of chemically shifted resonances difficult. Three methods were found of circumventing this problem: (1) magic-angle rotation; (2) saturation recovery experiments; and (3) infiltration of water into the tissue air spaces. In the dark, signals assigned to extravacuolar orthophosphate (Pi) at pH close to 7 and vacuolar Pi at pH below 6 were detected in the ratio 1:4. When the tissue was illuminated the extravacuolar Pi signal reported a more alkaline environment, consistent with expulsion of protons from the chloroplast stroma if this constitutes the principal extravacuolar Pi compartment. When tissue was incubated with mannose, mannose 6-phosphate was produced outside the vacuole. At the same time, the vacuolar Pi was depleted, while the extravacuolar Pi pool remained unchanged.

An affinity matrix for the isolation of L-phenylalanine ammonia-lyase

Abstract An affinity matrix for L -phenylalanine ammonia-lyase has been synthesized by coupling a protected 2-aminooxy-3-(4′-hydroxyphenyl)propionic acid derivative to epoxy-activated Sepharose 6B through the phenolic hydroxyl group. This avidly and specifically binds bean phenylalanine ammonia-lyase from partially purified preparations; active enzyme, albeit in relatively low yield, is released by incubation with 2-aminooxy-3-phenylpropionic acid. Alternatively, pure phenylalanine ammonia-lyase subunits may be released by elution with sodium dodecyl sulphate or urea.