code: public static String toPDB(Chain chain){
  		StringBuffer w = new StringBuffer();
  		int nrGroups = chain.getAtomLength();
  
  		for ( int h=0; h<nrGroups;h++){
  
  			Group g= chain.getAtomGroup(h);
  
  
  			toPDB(g,w);
  
  
  		}
  
  		return w.toString();
  	}
docs: Convert a Chain object to PDB representation
  
  @param chain
  @return