Jun.29,2006  15  US 2006/0141632 Al  -continued  What is claimed is:  with one or more acidic moieties having pKas of less  than about 2 when coupled with the polypeptide or  peptides, to provide one or more derivatized analytes;  2.  A method according to claim 1 wherein the fragmen› tation pattern is substantially free of a-ions and b-ions.  (a) converting the epsilon amino group of lysine on the  lysine containing peptides to a guanine or another very  basic group, a fixed cationic-charged group or an  isotopically labeled group;  (b) derivatizing the N-terminus of the polypeptide or the  N-termini of one or more peptides of the polypeptide  ( c) analyzing one or more derivatized analytes using a  mass spectrometric technique to provide a fragmenta› tion pattern; and  ( d) interpreting the fragmentation pattern.  1.  A method of determining the amino acid sequence of a  polypeptide wherein one or more peptides of the polypeptide  contain lysine, said method comprising:  <210> SEQ ID NO 6  <211> LENGTH: 16  <212> TYPE: PRT  <213> ORGANISM: rat  <400> SEQUENCE: 6  Ile Leu Ile Arg Pro Leu Tyr Ser Asn Pro Pro Leu Asn Gly Ala Arg  1  5  10  15  <210> SEQ ID NO 7  <2 11 > LENGTH : 7  <212> TYPE: PRT  <213> ORGANISM: rat  <400> SEQUENCE: 7  Val Val Leu His Pro Glu Arg  1  5  <210> SEQ ID NO 8  <211> LENGTH: 5  <212> TYPE: PRT  <213> ORGANISM: rat  <400> SEQUENCE: 8  Asn Val Asn Phe Arg  5  <210> SEQ ID NO 9  <211> LENGTH: 21  <212> TYPE: PRT  <213> ORGANISM: Artificial Sequence  <220> FEATURE:  <223> OTHER INFORMATION: OTHER INFORMATION:  Modified subtilisin from B.  lentus  <400> SEQUENCE: 9  Gly Val Leu Val Val Ala Ala Ser Gly Asn Ser Gly Ala Gly Ser Ile  1  5  10  15  Ser Tyr Pro Ala Arg  20  <210> SEQ ID NO 10  <2 11 > LENGTH : 9  <212> TYPE: PRT  <213> ORGANISM: Artificial Sequence  <220> FEATURE:  <223> OTHER INFORMATION: commercially available from Sigma Chemical Co.  <400> SEQUENCE: 10  Val Gly Gly Tyr Gly Tyr Gly Ala Lys  1  5 