Peptide MappingMass SpectrometryIsotope LabelingIsotopesPeptidesNitrogen IsotopesOxygen IsotopesCarbon IsotopesPeptide FragmentsPeptide LibraryAntimicrobial Cationic PeptidesPeptides, CyclicZinc IsotopesSulfur IsotopesDeuteriumAmino Acid SequenceTandem Mass SpectrometryOligopeptidesIron IsotopesSpectrometry, Mass, Electrospray IonizationMolecular Sequence DataKineticsSpectrometry, Mass, Matrix-Assisted Laser Desorption-IonizationNatriuretic Peptide, Brain