答案1
解决方案chemmove
\documentclass{article}
\usepackage{chemfig}
\usetikzlibrary{calc}
\begin{document}
\chemfig{NH(-[4]@{a})(-[:165,0.22,,,draw=none]^{+})
=[:60,,1]-[:120,,,1]NH-[4]@{b}-[2]CH_2
-[2]C(-[2]H)(-[4,0.9]H_3N^{+}|\vphantom{C})
-[0]C(=[1]O)
-[-1]O|^{-}}
\chemmove[-]{
\draw (a) -- (b);
\draw ($(a)+(2pt,2pt)$) -- ($(b)+(2pt,-2pt)$);
}
\end{document}