From: Bharat Sharma (
Date: Wed Feb 11 2015 - 12:14:21 CST

I am interested in getting index number from residue number. For example, I
have a water molecule with residue # 63 which has three atoms O H H with
indices 189 190 191. I am only interested to get O index, i.e. 189.

e.g. puts $res gives 63. I want to use something like $res get
(....???....) which gives index number. Since variable $res is a number, I
am not sure how to get index unless it has some connection with indices.

Is there any way to get first index? Actually I need this to get the bond
between O-O. If there is a way to get O-O bond from residue, it's fine too.
I do not want to select again atom and get indexes, because I have many
loops where I need residue numbers not index numbers.

Thank you.