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Permeability of methylamine across the membrane of a cyanobacterial cell
Author(s) -
Ritchie Raymond J.,
Islam Nazrul
Publication year - 2001
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/1468-0068.00434
Subject(s) - methylamine , chemistry , ammonia , synechococcus , cyanobacteria , membrane , amine gas treating , permeability (electromagnetism) , nitrogen , weak base , inorganic chemistry , biophysics , biochemistry , organic chemistry , biology , bacteria , genetics
Summary• Ammonia (NH 3 ) is the preferred nitrogen source for many eukaryotic algae and the cyanobacteria, Synechococcus R‐2 (PCC 7942) and Synechocystis (PCC 6803).• Ammonia in solution is a weak base with a pKa of 9.25; hence, under environmental conditions it is present in solution as NH 3 and NH 4 + . The uncharged form is a readily diffusible small molecule but NH 4 + has an ionic radius similar to K + and behaves like an alkali metal cation. Accumulation and retention of NH 3 + NH 4 + is therefore a complicated function of the permeabilities of two very different chemical species.• NH 3 is usually thought to be highly permeable across cell membranes although it is difficult to find actual measurements primarily because there is no convenient radioactive tracer for N. Many studies have therefore used 14 C‐methylamine ( 14 CH3‐NH 2 ) as a convenient analogue tracer.• Permeability of 14 CH3‐NH 2 was measured in Synechocystis over a range of pH values; permeability of uncharged amines was shown to be governed by pH. The permeability of CH 3 NH 2 is c . 50 µm s −1 at pH o 10 but increases very rapidly to c . 300 µm s −1 at pH o 7. This finding has serious implications for attempts to develop stochastic models of amine uptake and retention by cells.