Examples of nPAA introduced into model peptides using engineered ribosomal translation systems. Incorporation of Sep and pTyr was improved by means of EF-Tu mutants. Incorporation of d-Ala, Aib, β-hPhg, β-hMet, (1S,2S)-2-ACHC, (1S,2S)-2-ACPC, (1R,2R)-2-ACPC, cis-3-ACBC, trans-3-ACBC, Abz, Apy, Atp, and Atz was improved by tRNA engineering.