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\PYG{g+gp}{\PYGZgt{}\PYGZgt{}\PYGZgt{} }\PYG{k+kn}{from} \PYG{n+nn}{Bio.PDB.PDBParser} \PYG{k+kn}{import} \PYG{n}{PDBParser}
\PYG{g+gp}{\PYGZgt{}\PYGZgt{}\PYGZgt{} }\PYG{n}{parser} \PYG{o}{=} \PYG{n}{PDBParser}\PYG{p}{()}
\PYG{g+gp}{\PYGZgt{}\PYGZgt{}\PYGZgt{} }\PYG{n}{structure} \PYG{o}{=} \PYG{n}{parser}\PYG{o}{.}\PYG{n}{get\PYGZus{}structure}\PYG{p}{(}\PYG{l+s+s2}{\PYGZdq{}test\PYGZdq{}}\PYG{p}{,} \PYG{l+s+s2}{\PYGZdq{}1fat.pdb\PYGZdq{}}\PYG{p}{)}
\PYG{g+gp}{\PYGZgt{}\PYGZgt{}\PYGZgt{} }\PYG{n}{model} \PYG{o}{=} \PYG{n}{structure}\PYG{p}{[}\PYG{l+m+mi}{0}\PYG{p}{]}
\PYG{g+gp}{\PYGZgt{}\PYGZgt{}\PYGZgt{} }\PYG{n}{chain} \PYG{o}{=} \PYG{n}{model}\PYG{p}{[}\PYG{l+s+s2}{\PYGZdq{}A\PYGZdq{}}\PYG{p}{]}
\PYG{g+gp}{\PYGZgt{}\PYGZgt{}\PYGZgt{} }\PYG{n}{residue} \PYG{o}{=} \PYG{n}{chain}\PYG{p}{[}\PYG{l+m+mi}{1}\PYG{p}{]}
\PYG{g+gp}{\PYGZgt{}\PYGZgt{}\PYGZgt{} }\PYG{n}{atom} \PYG{o}{=} \PYG{n}{residue}\PYG{p}{[}\PYG{l+s+s2}{\PYGZdq{}CA\PYGZdq{}}\PYG{p}{]}
\end{Verbatim}
