preferred_name: cytosine(in) + H(+)(in) <=> cytosine(out) + H(+)(out)
preferred_name_lc: cytosine(in) + h(+)(in) <=> cytosine(out) + h(+)(out)
label: cytosine(in) + H(+)(in) <=> cytosine(out) + H(+)(out)
label_lc: cytosine(in) + h(+)(in) <=> cytosine(out) + h(+)(out)