def next_residue(residue) :
    """Expects an MMTK residue, returns the next residue in the chain, or None"""
    #Proteins go N terminal --> C terminal
    #The next reside is bonded to the C of this atom...
    for a in residue.peptide.C.bondedTo():
        if a.parent.parent != residue:
            return a.parent.parent
    return None