13 January 1993 Measuring changes in the mass of single subcellular organelles using x-ray microscopy
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Using quantitative scanning transmission x-ray microscopy, zymogen granules isolated from pancreatic acinar cells were observed suspended in aqueous medium at 50 nm resolution. From 3.64 nm x-ray absorption data, the protein content and rate of protein efflux from individual granules were determined. This was accomplished with a specially designed silicon nitride based wet-cell that allowed continuous perfusion and monitoring of individual granules in a variety of different aqueous environments. Granules suspended in 300 mM sucrose, 5 mM phosphate buffer (pH 6.0) were observed to continuously decrease in size and protein content over a period of several hours. Sudden lysis of the granules was not observed. From the flux data, the apparent protein permeability coefficients for individual granules were determined to range from 1 - 10 X 10-10 cm/sec with an average of 4.78 +/- 3.0 X 10-10 cm/sec. We believe this is the first quantitative population profile determined for a subcellular organelle developed from measurements of individual members of the population.
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Kaarin K. Goncz, Kaarin K. Goncz, Mario M. Moronne, Mario M. Moronne, W. Lin, W. Lin, Stephen S. Rothman, Stephen S. Rothman, } "Measuring changes in the mass of single subcellular organelles using x-ray microscopy", Proc. SPIE 1741, Soft X-Ray Microscopy, (13 January 1993); doi: 10.1117/12.138750; https://doi.org/10.1117/12.138750


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