Single-bead structure elucidation. Requirements for analysis of combinatorial solid-phase libraries by Nanoprobe MAS-NMR spectroscopy

A complete NMR structure analysis of an eight-residue peptide, covalently bound to a single-bead of a poly(ethylene glycol) based (POEPOP 1500) resin, is described. Well resolved 1D and 2D (1)H NMR spectra were obtained using magic angle spinning (MAS) Nanoprobe NMR spectroscopy at 500 MHz. The quantity of peptide on individual beads was determined after each NMR experiment by cleaving the peptide from the resin, and subsequent measurement of the fluorescence from the Abz-containing peptide in solution. It was found that about 1.6 nmol of peptide was the minimum amount needed to obtain a high resolution 1D (1)H NMR spectrum in less than 20 minutes. For a complete structure elucidation by 2D (1)H NMR a loading of about 6 nmol of peptide on a single-bead was required. It has been demonstrated that, with a sufficient loading on PEG-based resins, a complete structure elucidation of a resin bound octapeptide on a single bead can be achieved. This observation may be useful for screening and analysis of 'one-bead, one-compound' libraries.