TABLE 3.

Structural data for muropeptidesa

PeakAmt (nmol)Predicted structureb(M-H)m/zc
GlucosamineMuramitolMuramic acidAlaGluDiaminopimelic acidCalculatedObserved
Y11 (1)0.89 (1)0000Disaccharide497.1983497.1976
Y21 (2)0.36 (1)0.60 (1)000TS (no lactam)975.3782975.3808d
Y31 (2)0.22 (1)0.40 (1)0.41 (1)00TS—alanine1,046.41531,046.4172
Y41 (2)0.28 (1)0.46 (1)0.80 (2)0.34 (1)0.32 (1)TS—tetrapeptide1,418.57981,418.3507
7Am1 (2)0.34 (1)0.55 (1)000TS with lactam915.3570915.3598
  • a Peaks are numbered as in Fig. 3. All values determined in amino acid and amino sugar analyses (14) were normalized to the value for glucosamine, which was taken as 1. NAM residues at the reducing ends of muropeptides are detected as muramitol. Both internal NAM and muramic δ-lactam residues were detected as muramic acid. Values in parentheses are predicted moles of the residues within the molecule.

  • b TS, tetrasaccharide.

  • c (M-H) is the deprotonated molecular ion observed in the negative-ion mode. Calculated m/z is the mass-to-charge ratio predicted from the amino acid/amino sugar analyses. Average mass values are given. Observed m/z is the value measured by electrospray ionization and a Micromass QTOF-Ultima quadrupole time-of-flight mass spectrometer.

  • d The expected sodiated ion was also observed for this muropeptide.