Near-infrared spectrometric determination of di- and tripeptides synthesized by a combinatorial solid-phase method

A new method based on near-infrared (NIR) spectrometry and partial least-sq uares analysis has been developed for the noninvasive and nondestructive de termination of the identity and sequences of amino acid residues in di- and tripeptides, The di- and tripeptides were synthesized from six amino acids with similar structures (Gly, Ala, Leu, Met, Phe, Val) on two different po lymer beads (bead with and without a linker) using the solid-phase peptide synthetic method. The developed NIR method is capable of determining the id entity of sequences of these di- and tripeptides (with and without the Fmoc protecting group) directly on the polymer beads. It can distinguish not on ly dipeptides from tripeptides but also peptides with very similar structur es (e.g., bead-Gly-Ala-Ala, bead-Gly-Ala-Phe, bead-Gly-Ala-Leu, bead-Gly-Al a-Val, and bead-Gly-Ala-Met). More importantly, the method is capable of di stinguishing di- and tripeptides with the same amino acid residues but diff erent sequences (e.g., bead-Gly-Leu-Val from bead-Gly-Val-Leu).