choline(out) + n H(+)(in) => choline(in) + n H(+)(out)
choline(out) + n h(+)(in) => choline(in) + n h(+)(out)
choline(out) + n H(+)(in) => choline(in) + n H(+)(out)
choline(out) + n h(+)(in) => choline(in) + n h(+)(out)