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A Re‐examination of the Penetration of Nitella Cells by Non‐electrolytes
Author(s) -
Milborrow B. V.,
Williams D. A.
Publication year - 1968
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1968.tb07316.x
Subject(s) - penetration (warfare) , nitella , partition coefficient , chemistry , aqueous solution , chromatography , thermodynamics , biophysics , organic chemistry , mathematics , biology , physics , operations research
The increase, followed by culmination and decrease, of biological activity often observed within a homologous series of toxic compounds has previously been explained by assuming that their rate of movement between the lipid cell membrane and the aqueous protoplasm passes through an optimum as the partition coefficients increase progressively. In contrast to this, it has been claimed that direct measurements of the penetration rate of compounds through individual Nitella cells show tbat penetration rates are proportional to partition coefficients. In this attempt to investigate these two opposed hypotheses an analysis of published penetration rate data, obtained with Nitella , showed that the direct penetration measurements were best described by an equation which included a quadratic function of partition coefficient. There is, therefore, no inconsistency between the measurements of penetration by biological activity and by direct measurement. The compounds used in the latter procedure were all relatively hydrophilic and although a maximum rate of penetration was observed tbere was no indication of a subsequent decrease as there were no compounds with high partition coefficients. The correlation of penetration with other physical properties of the compounds is discussed.