Gramicidin derivatives as membrane-based pH sensors.
Ion channels provide a means for sensitive pH measurement at membrane interfaces. Detailed knowledge of the structure and function of gramicidin channels permits the engineering of pH-sensitive derivatives. Two derivatives, gramicidin-ethylenediamine and gramicidin-histamine, are shown to exhibit pH-dependent single-channel behaviour over the pH ranges 9-11 and 6.5-8.5, respectively. Thermal isomerization of a carbamate group at the entrance of the channels leads to a pattern of steps in single-channel recordings. The size of the steps depends on the time-averaged degree of protonation of the appended group (ethylenediamine or histamine). Measurement of the size of the steps thus permits single-molecule pH sensing under symmetrical pH conditions or in the presence of a pH gradient.
Borisenko
Vitali
V
Department of Chemistry, 80 St George Street, University of Toronto, M5S 3H6, Toronto, ON, Canada.
Zhang
Zhihua
Z
Woolley
G Andrew
GA
D015374:Biosensing Techniques; D002462:Cell Membrane / Q000737:chemistry*; D005029:Ethylenediamines / Q000737:chemistry; D006096:Gramicidin / Q000737:chemistry*; D006632:Histamine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007473:Ion Channels / Q000737:chemistry; D015394:Molecular Structure
D005029:Ethylenediamines; D007473:Ion Channels; D006096:Gramicidin; C031234:ethylenediamine; D006632:Histamine