private String getSelectStr(int chainNumber, int start, int end) {
Chain chain = structure.getChain(chainNumber) ;
if ( chain == null) return "" ;
String chainid = chain.getName() ;
Group gs = getGroupNext( chain,(start-1), true);
//Group gs = chain.getGroup(start-1);
Group ge = getGroupNext( chain,(end-1), false);
String startpdb = gs.getPDBCode() ;
String endpdb = ge.getPDBCode() ;
String cmd = "select "+startpdb+"-"+endpdb;
if ( ! chainid.equals(" "))
cmd += ":" +chainid + "/1";
else