Fig. 4.

Isolation of muropeptides after separation by FACE. Individual bands were cut from a FACE gel, eluted into distilled water, concentrated by evaporation, resuspended in water, and applied to separate lanes of a second FACE gel. Lane 1 is a standardized ladder of fluorescent glucose oligomers, with the least abundant band (third from bottom) representing a polymer of four glucose residues. The muropeptides in lanes 3, 4, and 5 were eluted and identified by mass spectrometry as the monomer-tetrapeptide, monomer-pentapeptide, and dimer-tetrapeptide-tetrapeptide, respectively (Table 4).