<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 

What is claimed is: 

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: 

(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 

-continued 

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; 

( c) analyzing one or more derivatized analytes using a mass spectrometric technique to provide a fragmenta› tion pattern; and 

( d) interpreting the fragmentation pattern. 

2. A method according to claim 1 wherein the fragmen› tation pattern is substantially free of a-ions and b-ions. 

