Guanine with hydrogen bond directions indicated
<a href="//commons.wikimedia.org/wiki/User:GKFX" title="User:GKFX">GKFX</a>, Cburnett
2020-03-26
My work Own work based on: <a href="//commons.wikimedia.org/wiki/File:Guannum2.png" title="File:Guannum2.png">Guannum2.png</a>