Sample

CHEMICAL DETAILS SAMPLE ORIGIN SAMPLE PREP./SIZE PYROL. CONDITIONS TOTAL ION COUNTS

: DEOXYRIBONUCLEASE I (from bovine pancreas) for amino acid composition see Table 13 BDH Chemicals Ltd., Poole, UK suspension in methanol; 10 pg standard 1.7 X 105

remarks - In comparison with RNase (Spectrum B.5) the decrease in Cys and Met content as well as the appearance of Trp residues produce the expected changes at m/z 34, 48, 117 and 131. It should be noted, however, that the marked differences in the percentage contribution of some aliphatic amino acid residues, e.g. Leu, lie, Val and Ala produce far less clearly defined differences in the spectrum. The peak at m/z 64 (S02+- and/or CH3S0H+") may point to slight oxidation of sulphur-containing amino acid residues.

Hm z

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