code: public static void addLastP(PolymerNotation polymer)
  			throws RNAUtilsException, NotationException,  HELM2HandledException {
  		checkRNA(polymer);
  		/* Get last monomerNotation */
  		MonomerNotation lastObject = polymer.getPolymerElements().getListOfElements()
  				.get(polymer.getPolymerElements().getListOfElements().size() - 1);
  
  		/* What happens to HELM2 features */
  		if (lastObject instanceof MonomerNotationGroup || lastObject instanceof MonomerNotationList) {
  			throw new HELM2HandledException("HELM2 features are involved");
  		}
  
  		if (!(hasPhosphat((MonomerNotationUnitRNA) lastObject))) {
  			MonomerNotation lastObjectwithPhosphat = new MonomerNotationUnitRNA(lastObject.getUnit() + "P", "RNA");
  			ChangeObjects.changeMonomerNotation(polymer.getPolymerElements().getListOfElements().size() - 1, polymer,
  					lastObjectwithPhosphat);
  			LOG.info("Phosphate was added to the last nucleotide");
  		}
  
  	}
docs: method to add a phosphate to the last polymer's nucleotide
  
  @param polymer
  PolymerNotation
  @throws RNAUtilsException
  if the polymer is no rna or dna
  @throws NotationException
  if the changed notation object can not be generated
  @throws HELM2HandledException
  if HELM2 features are involved