Wednesday, November 4, 2009
Ballroom A+B (Camino Real Hotel)
One-bead, one-compound (OBOC) peptide libraries are often very large with possible combinations in the hundred-thousands, and because of this there is significant need for a quick, reliable screening method by which the peptide sequence can be extracted from the bead and analyzed so that the sequence of amino acids may be confirmed by the library. A novel approach is presented here for the use of a nanomanipulator-coupled with nanospray-mass spectrometry to complete the extraction and analysis. The small sample volumes and picomolar sensitivity achievable by nanospray mass spectrometry make it ideal for OBOC library analysis. Nanometer-scale translational resolution is achievable with the nanomanipulator, allowing for the discrete selection of a single bead ensuring that only the desired peptides are screened. Nanomanipulation greatly reduces the sample preparation when compared with conventional OBOC screening techniques such as liquid chromatography or matrix assisted laser desorption ionization techniques, resulting in improved efficiency and sample throughput. Initially, single bead analyses were compared to bulk sample analysis by electrospray ionization to demonstrate the ability of nanospray ionization to produce representative spectra. Once this was confirmed, library screening began by mass spectral detection of peptides ranging from 1 - 8 amino acids in length and tandem mass spectral sequencing of peptides 4 - 8 amino acids in length. Through this work, peptides as short as one amino acid were detected, and 13 members of an OBOC library containing 750 peptide combinations were successfully sequenced.