A comparison of the naturally-occurring  L-Ala, D-Gln, L-Lys, D-Ala tetrapeptide of a peptidoglycan with an all L-form of the same amino acids.

All L-form tetrapeptide Ala-Gln-Lys-Ala	L-Ala, D-Gln, L-Lys, D-Ala

On the left, with all L-form amino acids, both the Gln and Lys side chains are on the right.

On the right, the Lys side chain is on the right, but the Gln is on the left.