β-(1-Azulenyl)-l-alanine – a functional probe for determination of pKa of histidine residues

Abstract

β-(1-Azulenyl)-L-alanine (AzAla) can be incorporated into the influenza A virus M2 proton channel. AzAla's sensitivity to the protonation state of the nearby histidines and the lack of environmental fluorescence dependence allow for direct and straightforward determination of histidine pK_a values in ion channels.