The mixture sequenced contained at least two or three different light chains. Peptides containing the following substitutions were also isolated: Val-3, Ile-10, and Leu-12; Leu-22; Phe-36, Glu-42, and Ala-43; Thr-63 and Arg-68; Ser-76, Ser-77, Val-78, Ala-80, and Asp-85; and Gln-100 and Arg-107.