コード例 #1
0
  /**
   * Fills the PSM specific map.
   *
   * @param inputMap The input map
   * @param waitingHandler the handler displaying feedback to the user
   * @param shotgunProtocol information about the protocol
   * @param identificationParameters the identification parameters
   * @throws java.sql.SQLException exception thrown whenever an error occurred while interacting
   *     with the back-end database
   * @throws java.io.IOException exception thrown whenever an error occurred while reading an
   *     external file
   * @throws java.lang.ClassNotFoundException exception thrown whenever an error occurred while
   *     deserializing an object
   * @throws java.lang.InterruptedException exception thrown whenever a threading error occurred
   * @throws uk.ac.ebi.jmzml.xml.io.MzMLUnmarshallerException exception thrown whenever an error
   *     occurred while reading an mzML file
   */
  public void selectBestHitAndFillPsmMap(
      InputMap inputMap,
      WaitingHandler waitingHandler,
      ShotgunProtocol shotgunProtocol,
      IdentificationParameters identificationParameters)
      throws SQLException, IOException, ClassNotFoundException, InterruptedException,
          MzMLUnmarshallerException {

    waitingHandler.setSecondaryProgressCounterIndeterminate(false);
    waitingHandler.setMaxSecondaryProgressCounter(identification.getSpectrumIdentificationSize());

    PeptideSpectrumAnnotator spectrumAnnotator = new PeptideSpectrumAnnotator();
    boolean multiSE = inputMap.isMultipleAlgorithms();

    SequenceMatchingPreferences sequenceMatchingPreferences =
        identificationParameters.getSequenceMatchingPreferences();
    AnnotationSettings annotationPreferences = identificationParameters.getAnnotationPreferences();

    PeptideAssumptionFilter idFilter = identificationParameters.getPeptideAssumptionFilter();

    // Keep a map of the spectrum keys grouped by peptide
    HashMap<String, ArrayList<String>> orderedPsmMap = null;
    if (MemoryConsumptionStatus.memoryUsed() < 0.8) {
      orderedPsmMap =
          new HashMap<String, ArrayList<String>>(
              identification.getSpectrumIdentificationMap().size());
    }

    PSParameter psParameter = new PSParameter();

    for (String spectrumFileName : identification.getSpectrumFiles()) {

      HashMap<String, ArrayList<String>> keysMap = null;
      if (orderedPsmMap != null) {
        keysMap = new HashMap<String, ArrayList<String>>();
      }

      PsmIterator psmIterator =
          identification.getPsmIterator(spectrumFileName, null, true, waitingHandler);

      while (psmIterator.hasNext()) {

        SpectrumMatch advocateMatch = psmIterator.next();
        String spectrumKey = advocateMatch.getKey();

        // map of the peptide first hits for this spectrum: score -> max protein count -> max search
        // engine votes -> amino acids annotated -> min mass deviation -> peptide sequence
        HashMap<
                Double,
                HashMap<
                    Integer,
                    HashMap<
                        Integer,
                        HashMap<Integer, HashMap<Double, HashMap<String, PeptideAssumption>>>>>>
            peptideAssumptions =
                new HashMap<
                    Double,
                    HashMap<
                        Integer,
                        HashMap<
                            Integer,
                            HashMap<
                                Integer, HashMap<Double, HashMap<String, PeptideAssumption>>>>>>();

        // map of the tag first hits: score -> assumptions
        HashMap<Double, ArrayList<TagAssumption>> tagAssumptions =
            new HashMap<Double, ArrayList<TagAssumption>>();

        ArrayList<String> identifications = new ArrayList<String>();

        HashMap<Integer, HashMap<Double, ArrayList<SpectrumIdentificationAssumption>>> assumptions =
            identification.getAssumptions(spectrumKey);

        for (int searchEngine1 : assumptions.keySet()) {

          HashMap<Double, ArrayList<SpectrumIdentificationAssumption>> advocate1Map =
              assumptions.get(searchEngine1);

          double bestEvalue = Collections.min(advocate1Map.keySet());

          for (SpectrumIdentificationAssumption assumption1 : advocate1Map.get(bestEvalue)) {

            if (assumption1 instanceof PeptideAssumption) {

              PeptideAssumption peptideAssumption1 = (PeptideAssumption) assumption1;
              String id = peptideAssumption1.getPeptide().getKey();

              if (!identifications.contains(id)) {

                psParameter = (PSParameter) peptideAssumption1.getUrParam(psParameter);
                double p;

                if (multiSE && sequenceFactory.concatenatedTargetDecoy()) {
                  p = psParameter.getSearchEngineProbability();
                } else {
                  p = peptideAssumption1.getScore();
                }

                int nSE = 1;
                int proteinMax = 1;
                for (String protein :
                    peptideAssumption1
                        .getPeptide()
                        .getParentProteins(sequenceMatchingPreferences)) {
                  Integer tempCount = proteinCount.get(protein);
                  if (tempCount != null && tempCount > proteinMax) {
                    proteinMax = tempCount;
                  }
                }

                for (int searchEngine2 : assumptions.keySet()) {

                  if (searchEngine1 != searchEngine2) {

                    HashMap<Double, ArrayList<SpectrumIdentificationAssumption>> advocate2Map =
                        assumptions.get(searchEngine2);

                    boolean found = false;
                    ArrayList<Double> eValues2 = new ArrayList<Double>(advocate2Map.keySet());
                    Collections.sort(eValues2);

                    for (double eValue2 : eValues2) {
                      for (SpectrumIdentificationAssumption assumption2 :
                          advocate2Map.get(eValue2)) {

                        if (assumption2 instanceof PeptideAssumption) {

                          PeptideAssumption peptideAssumption2 = (PeptideAssumption) assumption2;

                          if (peptideAssumption1
                              .getPeptide()
                              .isSameSequenceAndModificationStatus(
                                  peptideAssumption2.getPeptide(), sequenceMatchingPreferences)) {
                            PSParameter psParameter2 =
                                (PSParameter) peptideAssumption2.getUrParam(psParameter);
                            p = p * psParameter2.getSearchEngineProbability();
                            nSE++;
                            found = true;
                            break;
                          }
                        }
                      }
                      if (found) {
                        break;
                      }
                    }
                  }
                }

                identifications.add(id);

                HashMap<
                        Integer,
                        HashMap<
                            Integer,
                            HashMap<Integer, HashMap<Double, HashMap<String, PeptideAssumption>>>>>
                    pMap = peptideAssumptions.get(p);
                if (pMap == null) {
                  pMap =
                      new HashMap<
                          Integer,
                          HashMap<
                              Integer,
                              HashMap<
                                  Integer, HashMap<Double, HashMap<String, PeptideAssumption>>>>>(
                          advocate1Map.size());
                  peptideAssumptions.put(p, pMap);
                }

                HashMap<
                        Integer,
                        HashMap<Integer, HashMap<Double, HashMap<String, PeptideAssumption>>>>
                    proteinMaxMap = pMap.get(proteinMax);
                if (proteinMaxMap == null) {
                  proteinMaxMap =
                      new HashMap<
                          Integer,
                          HashMap<Integer, HashMap<Double, HashMap<String, PeptideAssumption>>>>(1);
                  pMap.put(proteinMax, proteinMaxMap);
                }

                HashMap<Integer, HashMap<Double, HashMap<String, PeptideAssumption>>> nSeMap =
                    proteinMaxMap.get(nSE);
                if (nSeMap == null) {
                  nSeMap =
                      new HashMap<Integer, HashMap<Double, HashMap<String, PeptideAssumption>>>(1);
                  proteinMaxMap.put(nSE, nSeMap);
                  HashMap<Double, HashMap<String, PeptideAssumption>> coverageMap =
                      new HashMap<Double, HashMap<String, PeptideAssumption>>(1);
                  nSeMap.put(-1, coverageMap);
                  HashMap<String, PeptideAssumption> assumptionMap =
                      new HashMap<String, PeptideAssumption>(1);
                  coverageMap.put(-1.0, assumptionMap);
                  assumptionMap.put(
                      peptideAssumption1.getPeptide().getSequenceWithLowerCasePtms(),
                      peptideAssumption1);
                } else {
                  MSnSpectrum spectrum = (MSnSpectrum) spectrumFactory.getSpectrum(spectrumKey);

                  HashMap<Double, HashMap<String, PeptideAssumption>> coverageMap = nSeMap.get(-1);
                  if (coverageMap != null) {
                    HashMap<String, PeptideAssumption> assumptionMap = coverageMap.get(-1.0);
                    for (PeptideAssumption tempAssumption :
                        assumptionMap.values()) { // There should be only one
                      Peptide peptide = tempAssumption.getPeptide();
                      SpecificAnnotationSettings specificAnnotationPreferences =
                          annotationPreferences.getSpecificAnnotationPreferences(
                              spectrum.getSpectrumKey(),
                              tempAssumption,
                              identificationParameters.getSequenceMatchingPreferences(),
                              identificationParameters
                                  .getPtmScoringPreferences()
                                  .getSequenceMatchingPreferences());
                      HashMap<Integer, ArrayList<IonMatch>> coveredAminoAcids =
                          spectrumAnnotator.getCoveredAminoAcids(
                              annotationPreferences,
                              specificAnnotationPreferences,
                              (MSnSpectrum) spectrum,
                              peptide);
                      int nIons = coveredAminoAcids.size();
                      nSeMap.put(nIons, coverageMap);
                    }
                    nSeMap.remove(-1);
                  }

                  Peptide peptide = peptideAssumption1.getPeptide();
                  SpecificAnnotationSettings specificAnnotationPreferences =
                      annotationPreferences.getSpecificAnnotationPreferences(
                          spectrum.getSpectrumKey(),
                          peptideAssumption1,
                          identificationParameters.getSequenceMatchingPreferences(),
                          identificationParameters
                              .getPtmScoringPreferences()
                              .getSequenceMatchingPreferences());
                  HashMap<Integer, ArrayList<IonMatch>> coveredAminoAcids =
                      spectrumAnnotator.getCoveredAminoAcids(
                          annotationPreferences,
                          specificAnnotationPreferences,
                          (MSnSpectrum) spectrum,
                          peptide);
                  int nIons = coveredAminoAcids.size();

                  coverageMap = nSeMap.get(nIons);
                  if (coverageMap == null) {
                    coverageMap = new HashMap<Double, HashMap<String, PeptideAssumption>>(1);
                    HashMap<String, PeptideAssumption> assumptionMap =
                        new HashMap<String, PeptideAssumption>(1);
                    assumptionMap.put(
                        peptideAssumption1.getPeptide().getSequenceWithLowerCasePtms(),
                        peptideAssumption1);
                    coverageMap.put(-1.0, assumptionMap);
                    nSeMap.put(nIons, coverageMap);
                  } else {
                    HashMap<String, PeptideAssumption> assumptionMap = coverageMap.get(-1.0);
                    if (assumptionMap != null) {
                      for (PeptideAssumption tempAssumption :
                          assumptionMap.values()) { // There should be only one
                        double massError =
                            Math.abs(
                                tempAssumption.getDeltaMass(
                                    spectrum.getPrecursor().getMz(),
                                    shotgunProtocol.isMs1ResolutionPpm()));
                        coverageMap.put(massError, assumptionMap);
                      }
                      coverageMap.remove(-1.0);
                    }

                    double massError =
                        Math.abs(
                            peptideAssumption1.getDeltaMass(
                                spectrum.getPrecursor().getMz(),
                                shotgunProtocol.isMs1ResolutionPpm()));
                    assumptionMap = coverageMap.get(massError);
                    if (assumptionMap == null) {
                      assumptionMap = new HashMap<String, PeptideAssumption>(1);
                      coverageMap.put(massError, assumptionMap);
                    }
                    assumptionMap.put(
                        peptideAssumption1.getPeptide().getSequenceWithLowerCasePtms(),
                        peptideAssumption1);
                  }
                }
              }
            } else if (assumption1 instanceof TagAssumption) {
              TagAssumption tagAssumption = (TagAssumption) assumption1;
              ArrayList<TagAssumption> assumptionList = tagAssumptions.get(bestEvalue);
              if (assumptionList == null) {
                assumptionList = new ArrayList<TagAssumption>();
                tagAssumptions.put(bestEvalue, assumptionList);
              }
              assumptionList.add(tagAssumption);
            }
          }
        }

        SpectrumMatch spectrumMatch = new SpectrumMatch(spectrumKey);
        if (!peptideAssumptions.isEmpty()) {

          PeptideAssumption bestPeptideAssumption = null;
          ArrayList<Double> ps = new ArrayList<Double>(peptideAssumptions.keySet());
          Collections.sort(ps);
          double retainedP = 0;

          for (double p : ps) {

            retainedP = p;
            HashMap<
                    Integer,
                    HashMap<
                        Integer,
                        HashMap<Integer, HashMap<Double, HashMap<String, PeptideAssumption>>>>>
                pMap = peptideAssumptions.get(p);
            ArrayList<Integer> proteinMaxs = new ArrayList<Integer>(pMap.keySet());
            Collections.sort(proteinMaxs, Collections.reverseOrder());

            for (int proteinMax : proteinMaxs) {

              HashMap<
                      Integer,
                      HashMap<Integer, HashMap<Double, HashMap<String, PeptideAssumption>>>>
                  proteinMaxMap = pMap.get(proteinMax);
              ArrayList<Integer> nSEs = new ArrayList<Integer>(proteinMaxMap.keySet());
              Collections.sort(nSEs, Collections.reverseOrder());

              for (int nSE : nSEs) {

                HashMap<Integer, HashMap<Double, HashMap<String, PeptideAssumption>>> nSeMap =
                    proteinMaxMap.get(nSE);
                ArrayList<Integer> coverages = new ArrayList<Integer>(nSeMap.keySet());
                Collections.sort(coverages, Collections.reverseOrder());

                for (Integer coverage : coverages) {

                  HashMap<Double, HashMap<String, PeptideAssumption>> coverageMap =
                      nSeMap.get(coverage);
                  ArrayList<Double> minErrors = new ArrayList<Double>(coverageMap.keySet());
                  Collections.sort(minErrors);

                  for (double minError : minErrors) {

                    HashMap<String, PeptideAssumption> bestPeptideAssumptions =
                        coverageMap.get(minError);
                    ArrayList<String> sequences =
                        new ArrayList<String>(bestPeptideAssumptions.keySet());
                    Collections.sort(sequences);

                    for (String sequence : sequences) {
                      PeptideAssumption peptideAssumption = bestPeptideAssumptions.get(sequence);
                      if (idFilter.validateProteins(
                          peptideAssumption.getPeptide(), sequenceMatchingPreferences)) {
                        bestPeptideAssumption = peptideAssumption;
                        break;
                      }
                    }
                    if (bestPeptideAssumption != null) {
                      break;
                    }
                  }
                  if (bestPeptideAssumption != null) {
                    break;
                  }
                }
                if (bestPeptideAssumption != null) {
                  break;
                }
              }
              if (bestPeptideAssumption != null) {
                break;
              }
            }
            if (bestPeptideAssumption != null) {
              break;
            }
          }
          if (bestPeptideAssumption != null) {

            if (multiSE) {

              // try to find the most likely modification localization based on the search engine
              // results
              HashMap<PeptideAssumption, ArrayList<Double>> assumptionPEPs =
                  new HashMap<PeptideAssumption, ArrayList<Double>>();
              String bestAssumptionKey =
                  bestPeptideAssumption.getPeptide().getMatchingKey(sequenceMatchingPreferences);

              for (int searchEngine : assumptions.keySet()) {

                boolean found = false;
                HashMap<Double, ArrayList<SpectrumIdentificationAssumption>> advocateMap =
                    assumptions.get(searchEngine);
                ArrayList<Double> eValues = new ArrayList<Double>(advocateMap.keySet());
                Collections.sort(eValues);

                for (double eValue : eValues) {
                  for (SpectrumIdentificationAssumption assumption : advocateMap.get(eValue)) {

                    if (assumption instanceof PeptideAssumption) {

                      PeptideAssumption peptideAssumption = (PeptideAssumption) assumption;

                      if (peptideAssumption
                          .getPeptide()
                          .getMatchingKey(sequenceMatchingPreferences)
                          .equals(bestAssumptionKey)) {

                        found = true;
                        boolean found2 = false;

                        for (PeptideAssumption assumption1 : assumptionPEPs.keySet()) {
                          if (assumption1
                              .getPeptide()
                              .sameModificationsAs(peptideAssumption.getPeptide())) {
                            found2 = true;
                            psParameter = (PSParameter) assumption.getUrParam(psParameter);
                            ArrayList<Double> peps = assumptionPEPs.get(assumption1);
                            peps.add(psParameter.getSearchEngineProbability());
                            break;
                          }
                        }

                        if (!found2) {
                          ArrayList<Double> peps = new ArrayList<Double>(1);
                          assumptionPEPs.put(peptideAssumption, peps);
                          psParameter = (PSParameter) assumption.getUrParam(psParameter);
                          peps.add(psParameter.getSearchEngineProbability());
                        }
                      }
                    }
                  }

                  if (found) {
                    break;
                  }
                }
              }

              Double bestSeP = null;
              int nSe = -1;

              for (PeptideAssumption peptideAssumption : assumptionPEPs.keySet()) {

                ArrayList<Double> peps = assumptionPEPs.get(peptideAssumption);
                Double sep = Collections.min(peps);

                if (bestSeP == null || bestSeP > sep) {
                  bestSeP = sep;
                  nSe = peps.size();
                  bestPeptideAssumption = peptideAssumption;
                } else if (peps.size() > nSe) {
                  if (sep != null && (Math.abs(sep - bestSeP) <= 1e-10)) {
                    nSe = peps.size();
                    bestPeptideAssumption = peptideAssumption;
                  }
                }
              }
            }

            // create a PeptideShaker match based on the best search engine match
            Peptide sePeptide = bestPeptideAssumption.getPeptide();
            ArrayList<String> psProteins =
                new ArrayList<String>(sePeptide.getParentProteins(sequenceMatchingPreferences));
            ArrayList<ModificationMatch> psModificationMatches = null;
            if (sePeptide.isModified()) {
              psModificationMatches =
                  new ArrayList<ModificationMatch>(sePeptide.getNModifications());
              for (ModificationMatch seModMatch : sePeptide.getModificationMatches()) {
                psModificationMatches.add(
                    new ModificationMatch(
                        seModMatch.getTheoreticPtm(),
                        seModMatch.isVariable(),
                        seModMatch.getModificationSite()));
              }
            }

            Peptide psPeptide = new Peptide(sePeptide.getSequence(), psModificationMatches);
            psPeptide.setParentProteins(psProteins);
            PeptideAssumption psAssumption =
                new PeptideAssumption(
                    psPeptide,
                    1,
                    Advocate.peptideShaker.getIndex(),
                    bestPeptideAssumption.getIdentificationCharge(),
                    retainedP);

            spectrumMatch.setBestPeptideAssumption(psAssumption);

            if (orderedPsmMap != null) {
              String peptideKey = psPeptide.getMatchingKey(sequenceMatchingPreferences);
              ArrayList<String> spectrumKeys = keysMap.get(peptideKey);
              if (spectrumKeys == null) {
                spectrumKeys = new ArrayList<String>();
                keysMap.put(peptideKey, spectrumKeys);
              }
              spectrumKeys.add(spectrumKey);
            }

            psParameter = new PSParameter();
            psParameter.setSpectrumProbabilityScore(retainedP);

            PSParameter matchParameter =
                (PSParameter) bestPeptideAssumption.getUrParam(psParameter);
            psParameter.setSearchEngineProbability(matchParameter.getSearchEngineProbability());
            psParameter.setAlgorithmDeltaPEP(matchParameter.getAlgorithmDeltaPEP());
            psParameter.setDeltaPEP(matchParameter.getDeltaPEP());

            matchesValidator
                .getPsmMap()
                .addPoint(
                    psParameter.getPsmProbabilityScore(),
                    spectrumMatch,
                    sequenceMatchingPreferences);
            psParameter.setSpecificMapKey(
                spectrumMatch.getBestPeptideAssumption().getIdentificationCharge().value + "");
            identification.addSpectrumMatchParameter(spectrumKey, psParameter);
            identification.updateSpectrumMatch(spectrumMatch);
          }
        }
        if (!tagAssumptions.isEmpty()) {
          ArrayList<Double> evalues = new ArrayList<Double>(tagAssumptions.keySet());
          Double bestEvalue = Collections.min(evalues);
          TagAssumption bestAssumption = tagAssumptions.get(bestEvalue).get(0);
          spectrumMatch.setBestTagAssumption(bestAssumption);
          identification.updateSpectrumMatch(spectrumMatch);
          if (spectrumMatch.getBestPeptideAssumption() == null) {
            psParameter = new PSParameter();
            if (!multiSE) {
              psParameter.setSpectrumProbabilityScore(bestEvalue);
            }
            PSParameter matchParameter = (PSParameter) bestAssumption.getUrParam(psParameter);
            psParameter.setSearchEngineProbability(matchParameter.getSearchEngineProbability());
            psParameter.setAlgorithmDeltaPEP(matchParameter.getAlgorithmDeltaPEP());
            psParameter.setDeltaPEP(matchParameter.getDeltaPEP());
            psParameter.setSpecificMapKey(
                spectrumMatch.getBestTagAssumption().getIdentificationCharge().value + "");
            identification.addSpectrumMatchParameter(spectrumKey, psParameter);
          }
        }
        waitingHandler.increaseSecondaryProgressCounter();
        if (waitingHandler.isRunCanceled()) {
          return;
        }
      }

      if (orderedPsmMap != null) {
        ArrayList<String> orderedKeys =
            new ArrayList<String>(
                identification.getSpectrumIdentification(spectrumFileName).size());
        for (ArrayList<String> keys : keysMap.values()) {
          orderedKeys.addAll(keys);
        }
        orderedPsmMap.put(spectrumFileName, orderedKeys);

        if (MemoryConsumptionStatus.memoryUsed() > 0.9) {
          orderedPsmMap = null;
        }
      }
    }

    if (orderedPsmMap != null) {
      metrics.setOrderedSpectrumKeys(orderedPsmMap);
    }

    // the protein count map is no longer needed
    proteinCount.clear();

    waitingHandler.setSecondaryProgressCounterIndeterminate(true);
  }
コード例 #2
0
  /**
   * Selects a first hit in a list of equally scoring peptide matches. The selection is made based
   * on: 1 - The occurrence of the protein detection as given in the proteinCount map 2 - The
   * sequence coverage by fragment ions 3 - The precursor mass error.
   *
   * <p>If no best hit is found, the first one sorted alphabetically is retained.
   *
   * @param spectrumKey the key of the spectrum
   * @param firstHits list of equally scoring peptide matches
   * @param proteinCount map of the number of peptides for every protein
   * @param sequenceMatchingPreferences the sequence matching preferences
   * @param shotgunProtocol the shotgun protocol
   * @param identificationParameters the identification parameters
   * @param spectrumAnnotator the spectrum annotator to use
   * @return a first hit from the list of equally scoring peptide matches
   * @throws IOException exception thrown whenever an IO exception occurred while remapping the
   *     proteins or getting the spectrum
   * @throws InterruptedException exception thrown whenever an interrupted exception occurred while
   *     remapping the proteins or getting the spectrum
   * @throws SQLException exception thrown whenever an SQL exception occurred while interacting with
   *     the protein tree
   * @throws ClassNotFoundException exception thrown whenever an exception occurred while
   *     deserializing an object
   * @throws MzMLUnmarshallerException exception thrown whenever an exception occurred while reading
   *     an mzML file
   */
  public static PeptideAssumption getBestHit(
      String spectrumKey,
      ArrayList<PeptideAssumption> firstHits,
      HashMap<String, Integer> proteinCount,
      SequenceMatchingPreferences sequenceMatchingPreferences,
      ShotgunProtocol shotgunProtocol,
      IdentificationParameters identificationParameters,
      PeptideSpectrumAnnotator spectrumAnnotator)
      throws IOException, InterruptedException, SQLException, ClassNotFoundException,
          MzMLUnmarshallerException {

    if (firstHits.size() == 1) {
      return firstHits.get(0);
    }

    Integer maxProteins = 0;
    ArrayList<PeptideAssumption> bestPeptideAssumptions =
        new ArrayList<PeptideAssumption>(firstHits.size());

    for (PeptideAssumption peptideAssumption : firstHits) {
      for (String accession :
          peptideAssumption.getPeptide().getParentProteins(sequenceMatchingPreferences)) {
        Integer count = proteinCount.get(accession);
        if (count != null) {
          if (count > maxProteins) {
            maxProteins = count;
            bestPeptideAssumptions.clear();
            bestPeptideAssumptions.add(peptideAssumption);
          } else if (count.equals(maxProteins)) {
            bestPeptideAssumptions.add(peptideAssumption);
          }
        }
      }
    }

    if (bestPeptideAssumptions.size() == 1) {
      return bestPeptideAssumptions.get(0);
    } else if (!bestPeptideAssumptions.isEmpty()) {
      firstHits = bestPeptideAssumptions;
      bestPeptideAssumptions = new ArrayList<PeptideAssumption>(firstHits.size());
    }

    MSnSpectrum spectrum = (MSnSpectrum) SpectrumFactory.getInstance().getSpectrum(spectrumKey);
    int maxCoveredAminoAcids = 0;
    AnnotationSettings annotationPreferences = identificationParameters.getAnnotationPreferences();

    for (PeptideAssumption peptideAssumption : firstHits) {
      Peptide peptide = peptideAssumption.getPeptide();
      SpecificAnnotationSettings specificAnnotationPreferences =
          annotationPreferences.getSpecificAnnotationPreferences(
              spectrum.getSpectrumKey(),
              peptideAssumption,
              identificationParameters.getSequenceMatchingPreferences(),
              identificationParameters.getPtmScoringPreferences().getSequenceMatchingPreferences());
      HashMap<Integer, ArrayList<IonMatch>> coveredAminoAcids =
          spectrumAnnotator.getCoveredAminoAcids(
              annotationPreferences,
              specificAnnotationPreferences,
              (MSnSpectrum) spectrum,
              peptide);
      int nAas = coveredAminoAcids.size();
      if (nAas > maxCoveredAminoAcids) {
        maxCoveredAminoAcids = nAas;
        bestPeptideAssumptions.clear();
        bestPeptideAssumptions.add(peptideAssumption);
      } else if (nAas == maxCoveredAminoAcids) {
        bestPeptideAssumptions.add(peptideAssumption);
      }
    }

    if (bestPeptideAssumptions.size() == 1) {
      return bestPeptideAssumptions.get(0);
    } else if (!bestPeptideAssumptions.isEmpty()) {
      firstHits = bestPeptideAssumptions;
      bestPeptideAssumptions = new ArrayList<PeptideAssumption>(firstHits.size());
    }

    double minMassError = identificationParameters.getPeptideAssumptionFilter().getMaxMzDeviation();
    if (minMassError == -1.0) {
      minMassError = identificationParameters.getSearchParameters().getPrecursorAccuracy();
    }

    for (PeptideAssumption peptideAssumption : firstHits) {
      double massError =
          Math.abs(
              peptideAssumption.getDeltaMass(
                  spectrum.getPrecursor().getMz(), shotgunProtocol.isMs1ResolutionPpm()));
      if (massError < minMassError) {
        minMassError = massError;
        bestPeptideAssumptions.clear();
        bestPeptideAssumptions.add(peptideAssumption);
      } else if (massError == minMassError) {
        bestPeptideAssumptions.add(peptideAssumption);
      }
    }

    if (bestPeptideAssumptions.size() == 1) {
      return bestPeptideAssumptions.get(0);
    } else if (bestPeptideAssumptions.isEmpty()) {
      bestPeptideAssumptions = firstHits;
    }

    HashMap<String, PeptideAssumption> sequenceToPeptideAssumptionsMap =
        new HashMap<String, PeptideAssumption>(bestPeptideAssumptions.size());
    for (PeptideAssumption peptideAssumption : bestPeptideAssumptions) {
      sequenceToPeptideAssumptionsMap.put(
          peptideAssumption.getPeptide().getSequence(), peptideAssumption);
    }

    ArrayList<String> sequences = new ArrayList<String>(sequenceToPeptideAssumptionsMap.keySet());
    Collections.sort(sequences);
    return sequenceToPeptideAssumptionsMap.get(sequences.get(0));
  }