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Water transport by the bacterial channel alpha-hemolysinThis study is an investigation of the ability of the bacterial channel alpha-hemolysin to facilitate water permeation across biological membranes. alpha-Hemolysin channels were incorporated into rabbit erythrocyte ghosts at varying concentrations, and water permeation was induced by mixing the ghosts with hypertonic sucrose solutions. The resulting volume decrease of the ghosts was followed by time-resolved optical absorption at pH 5, 6, and 7. The average single-channel permeability coefficient of alpha-hemolysin for water ranged between 1.3x10-12 cm/s and 1.5x10-12 cm/s, depending on pH. The slightly increased single-channel permeability coefficient at lower pH-values was attributed to an increase in the effective pore size. The activation energy of water transport through the channel was low (Ea=5.4 kcal/mol), suggesting that the properties of water inside the alpha-hemolysin channel resemble those of bulk water. This conclusion was supported by calculations based on macroscopic hydrodynamic laws of laminar water flow. Using the known three-dimensional structure of the channel, the calculations accurately predicted the rate of water flow through the channel. The latter finding also indicated that water permeation data can provide a good estimate of the pore size for large channels.
Document ID
Document Type
Reprint (Version printed in journal)
Paula, S. (University of California at Santa Cruz Santa Cruz, CA 95064, United States)
Akeson, M.
Deamer, D.
Date Acquired
August 22, 2013
Publication Date
April 14, 1999
Publication Information
Publication: Biochimica et biophysica acta
Volume: 1418
Issue: 1
ISSN: 0006-3002
Subject Category
Life Sciences (General)
Distribution Limits
Non-NASA Center
NASA Discipline Exobiology