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Article #35

Entering Crystal Structures using ReadPDB

#35
From: B.Cowie,E8,3589,060641500
Date: Wed, 05 Aug 1992 13:21
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I have a workaround for anyone who wants to enter crystal 
structures as Molecules with ReadPDB

First you need to get your crystal structure into atomic
coordinates ala the files nutrasweet.pdb given in the chemistry
module example.  The vital data is ATOM element number of atom
and its position in space.  Now if you use Readpdb it will take
the file in however it will also attempt to make bonds with 
the closest atoms.  You can fool the program into not making
bonds by taking a copy of the elements.h file and reducing the
first radius value of the element in question. 
This radius appears to define the bonding
the second radius value affects the size of the sphere displayed
in the render module.  By reducing the size you can globally
alter the bonding of all the atoms.  By playing around with the
size you can selectively suppress some longer bonds or turn them 
all off.  You can override the bond generation by putting the
line CONECT    2    5 in the pdb file on a seperate line
this forces the generation of a bond between the two numbered
atoms.  No matter how far apart they are.

You can then use Ball and Stick to change the atom sizes like
the chemistry example.  

This isn't the most elegant way of using Explorer.
the syntax for CONECT is :-
first Field CONECT,next 5 characters first atom number, next 5 characters
second atom number

Does anybody else look at crystal structures with explorer?

Bruce Cowie
  
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Message-ID: <1992Aug5.132136.322@gserv1.dl.ac.uk>
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From: bcc@gserv1.dl.ac.uk (B.Cowie,E8,3589,060641500)
Newsgroups: comp.graphics.explorer
Subject: Entering Crystal Structures using ReadPDB
Message-ID: <1992Aug5.132136.322@gserv1.dl.ac.uk>
Date: 5 Aug 92 13:21:36 GMT
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Organization: Daresbury Laboratory, UK
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