\documentclass[12pt,border=3pt,tikz,class=scrartcl,multi=false]{standalone}
\usepackage{times}
\usepackage[T1]{fontenc}
\usepackage[latin1]{inputenc}
\usepackage{mathtools,amssymb,gensymb}
\usepackage{pgfplots}
\pgfplotsset{compat=1.12}
\usetikzlibrary{positioning,calc,arrows,fit,backgrounds,decorations.text,shapes}
 
\usepackage{chemfig,chemmacros}
\renewcommand*{\familydefault}{\sfdefault}
\renewcommand*\printatom[1]{\ensuremath{\mathsf{#1} } }
\setatomsep{2.5em}
\setdoublesep{.6ex}
\setarrowdefault{,1,ultra thick}
\setbondstyle{very thick,cap=round}
\definesubmol\nobond{-[0,.6,,,draw=none]}

\pgfdeclaredecoration{ddbond}{initial} {
	\state{initial}[width=4pt] {
		\pgfpathlineto{\pgfpoint{4pt}{0pt} }
		\pgfpathmoveto{\pgfpoint{2pt}{2pt} }
		\pgfpathlineto{\pgfpoint{4pt}{2pt} }
		\pgfpathmoveto{\pgfpoint{4pt}{0pt} }
	}
	\state{final} {
		\pgfpathlineto{\pgfpointdecoratedpathlast}
	}
}
\tikzset{lddbond/.style={decorate,decoration=ddbond} }
\tikzset{rddbond/.style={decorate,decoration={ddbond,mirror} } }
 
\pagestyle{empty}
\thispagestyle{empty}
\begin{document}
\renewcommand{\baselinestretch}{1}
\begin{tikzpicture}[thick, >=latex']
	\node (n1) {\chemname{\chemfig{
		H_2N-[::-30,,,,lddbond]\chemabove[0pt]{C}{\fpch}
		(-[::60,,,,lddbond]NH_2)
		-[::-60,,,2]HN-[::60]-[::-60]-[::60]-[::-60,,,,dashed]
	} }{arginine} };
	\node [right=5 of n1.south,anchor=south] (n2) {\chemname{\chemfig{
		H_2N-[::-30,,,,lddbond]\chemabove[0pt]{C}{\fpch}
		(-[::60,,,,lddbond]NH-[::60])
		-[::-60,,,2]HN-[::60]-[::-60]-[::60]-[::-60,,,,dashed]
	} }{methylarginine} };
	\node [right=5 of n2.south,anchor=south] (n3) {\chemname{\chemfig{
		H_2N-[::-30,,,,lddbond]\chemabove[0pt]{C}{\fpch}
		(-[::60,,,,lddbond]N(-[::-60])-[::60])
		-[::-60,,,2]HN-[::60]-[::-60]-[::60]-[::-60,,,,dashed]
	} }{\parbox{9em}{\centering asymmetric dimethylarginine} } };
	\node [right=5 of n3.south,anchor=south] (n4) {\chemname{\chemfig{
		HN(-[2,,2])-[::-30,,,,lddbond]\chemabove[0pt]{C}{\fpch}
		(-[::60,,,,lddbond]NH-[::60])
		-[::-60,,,2]HN-[::60]-[::-60]-[::60]-[::-60,,,,dashed]
	} }{\parbox{9em}{\centering symmetric dimethylarginine} } };
\end{tikzpicture}
\end{document}