Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
Structure and ionization of the guanidinium group. Saxitoxin (STX) has two guanidinium moieties and therefore two dissociation constants: pKa 8.22 for the 7,8,9 guanidinium group and 11.28 for the 1,2,3 group [12]. Tetrodotoxin (TTX) has only one guanidinium moiety, with a pKa of 8.76. These groups are protonated under physiological conditions, with a +1 charge [13].
