code: public static final boolean isConnected(AminoAcid a, AminoAcid b) {
  		Atom C = null ;
  		Atom N = null;
  
  		C = a.getC();
  		N = b.getN();
  
  		if ( C == null || N == null)
  			return false;
  
  		// one could also check if the CA atoms are < 4 A...
  		double distance = getDistance(C,N);
  		return distance < 2.5;
  	}
docs: Test if two amino acids are connected, i.e. if the distance from C to N <
  2.5 Angstrom.
  
  If one of the AminoAcids has an atom missing, returns false.
  
  @param a
  an AminoAcid object
  @param b
  an AminoAcid object
  @return true if ...