Thomas, thank you for so detailed explanation.

This way works good but I'd like to ask you about possibe Hbonds in the protein chain.

As I remember for protein physics courses the H atom is always donor for only ONE H-bond ( and O or N atoms could be akceptors for 1 or 2 Hbonds)

But In my case there are some cases where H atom ( white ) is donor for the 2 Hbonds.  By the way I found the same on the picture in WIKI too.

How it could be explaned ?

James