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 b ound to a single-bead of a poly(ethylene glycol) based (POEPOP 1500) resin, is described. Well resolved 1D and 2D H-1 NMR spectra were obtained using magic angle spinning (MAS) Nanoprobe NMR spectroscopy at 500 MHz. The quant ity 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 r esolution 1D H-1 NMR spectrum in less than 20 minutes. For a complete struc ture elucidation by 2D H-1 NMR a loading of about 6 nmol of peptide on a si ngle-bead was required. It has been demonstrated that, with a sufficient lo ading on PEG-based resins, a complete structure elucidation of a resin boun d octapeptide on a single bead can be achieved. This observation may be use ful for screening and analysis of 'one-bead, one-compound' libraries.