1. ISOMATCH-web For automatic matching of isotope peak distributions ■ Automatic matching of a raw spectrum (ASCII format) to theoretical isotopic distributions ■ Output and visualization (with “ISOMATCH viewer”) of theoretical masses and isotopic distributions ■ Output of theoretical peptide mass fingerprints of proteins ■ Registration of isotope relative abundances and compounds (Starting menu)

2. Input 1. Protein A30 C12 D14 E22 F20 G6 H7 I3 K22 L26 M3 N7 P9 Q9 R16 S11 T10 V13 W2 Y8 2. Modification: M(O), Na 3.Charge state: +17 4.Resolution: 50,000 ↓ Result J. Fernández-de-Cossio et al. Nucleic Acids Res., 32, 674-678 (2004) Application 1. Calculation of a complex isotopic envelop of a mixture

3. Application 2. Monoisotopic mass of heme C-bound peptide Heme C

4. CSQCHTVEK →molecular formula ： C 40 H 67 N 13 O 15 S 2 Monoisotopic peak :1034.43 Application 3. Isotopic distribution of 13 C-enriched peptide enriched with 13 C (90, 94, 96 atom %) 90 atom% 94 atom% 96 atom%

5. Protein pool (light) Protein pool (heavy) Proteolytic digestion in H 2 O MS Mix Mixed peptide 16 O 18 O:19.87% 16 O 2 :50.0% 18 O 2 :30.13% Sequence: LVNEVTEFAK Resolution:17,000 Modifications: 18 O 1-2 Application 4. Quantitative analysis with stable-isotope ( 18 O) labeling Proteolytic digestion in H 2 18 O ISOMATCH-web J. Fernández-de-Cossio et al., RCM 18, 2465-2472 (2004).