count_atomコマンドで特定のアミノ酸の数を数える

Grüezi,

タンパクの結晶構造を見てる時に，ふと特定のアミノ酸が何処にあるかとか，それが全部で何個あるか気になることってありますよね．
例えばLysineが何個あるか数えたい時は，PyMOL上のコマンドラインで，こう唱えます．

count_atom resn lys and chain A and backbone and elem n

count_atom (selection)でselectionの原子数を数えられます．
これを利用して，LysineかつChain Aかつ主鎖かつN原子の数を数えればタンパクに含まれるLysineの数を数えられるはずです．
コマンドを打つのが面倒なので，見たくなりそうなアミノ酸だけalias化して.pymolrcに追加しておきましょう．

alias k, hide sticks, polymer.protein; show sticks, resn lys; count_atom resn lys and chain A and backbone and elem n
alias c, hide sticks, polymer.protein; show sticks, resn cys; count_atom resn cys and chain A and backbone and elem n
alias s, hide sticks, polymer.protein; show sticks, resn ser; count_atom resn ser and chain A and backbone and elem n
alias h, hide sticks, polymer.protein; show sticks, resn his; count_atom resn his and chain A and backbone and elem n
alias t, hide sticks, polymer.protein; show sticks, resn thr; count_atom resn thr and chain A and backbone and elem n
alias r, hide sticks, polymer.protein; show sticks, resn arg; count_atom resn arg and chain A and backbone and elem n
alias d, hide sticks, polymer.protein; show sticks, resn asp; count_atom resn asp and chain A and backbone and elem n
alias e, hide sticks, polymer.protein; show sticks, resn glu; count_atom resn glu and chain A and backbone and elem n
alias y, hide sticks, polymer.protein; show sticks, resn tyr; count_atom resn tyr and chain A and backbone and elem n