interpretation of pdb files

Stephen Tate (sat@ribosome.bio.warwick.ac.uk)
Wed, 08 Mar 95 17:01:41 000

Sorry if this is not the place to post this but,
how do I interpret the pdb files? Assignement 4 asks
about helix info etc. My pdb file has such information
but does not make any sense, ie.

HELIX 1 H1 ASP A 81 ALA A 89 1

or
SHEET 1 SH110 ASN A 91 TYR A 94 0 1YTB 125
SHEET 2 SH110 VAL A 102 ILE A 106 -1 N ARG A 105 O ASN A 91 1YTB 12

Can somebody help me! I thought it weas logical and just a list of residues
associated with each of the helicies/sheets, but then numbers started to go backwards.

HELP.

Steve Tate Warwick University England