Piperazinomethyl polystyrene

An electrothermal vaporizer inductively coupled plasma mass spectrometer (ETV-ICPMS) was used to quantitatively screen metals bound to single polystyrene (TentaGel) beads with immobilized oligopeptides. Tests were performed using ETV-ICPMS to screen a series of identical beads as well as a series of combinatorial library beads exposed to a multimetal solution composed of Mg2+, Mn2+, Ni2+, Cu2+, Cd2+, Eu2+, and Pb2+. The residual metal content remaining bound to the beads after acid extractions was also analyzed by solid sampling of the entire bead using oxygen ashing in the ETV. Nine beads (80 mesh, 0.25 mmol g(-1) nominal capacity) containing covalently attached polyaspartic acid (PLAsp; n = 20) showed metal extract concentrations in the range of 4-130 ng mL(-1). After normalizing by bead volume, the precision of capacity measurements in a single bead (7-14%) was primarily dictated by analysis error and contributions from bead diameter measurement with negligible contributions, surprisingly, from variations in site density from bead to bead. A sample combinatorial library of the sequence GXXGXXGXXGXX (X = cysteine, aspartic acid, or glutamic acid and G = glycine) (60 mesh, 0.25 mmol g(-1) nominal capacity) was also used to demonstrate the utility of this method. Metal extract concentrations ranged from 1 to 1300 ng mL(-1) with significant concentration variation between beads, indicating the individual selectivity on each bead. For these larger beads, analysis precision (i.e., capacity precision) was further improved to 3-10% due to the overall increase in bead metal content. Through metal extract determinations, ETV-ICPMS was shown to be a viable nondestructive tool for full metal characterization of "hit" sequences belonging to a combinatorial library.

Natural polyamines are ubiquitous biomolecules present in all living cells. These cationic compounds play essential roles in both cell growth and differentiation and are known to interact in complex ways with polyanionic biomolecules. Consequently, there is significant interest in expanding nature's polyamine diversity using combinatorial synthesis and screening strategies. This article describes an efficient split-pool solid-phase synthetic strategy toward the generation of encoded libraries of polyamines via the exhaustive borane-promoted reduction of trityl-linked, resin-bound polyamides. Model structural libraries of tetra- and pentaamines were designed from a set of geometrically diverse amino acid building blocks. To encode the libraries, a partial termination synthesis approach was employed at the polyamide stage, allowing each library to be analyzed from single beads by HPLC/ESMS under two sets of conditions featuring both pH extremes. Determination of the sequence of polyamine residues was simply achieved by the mass differences observed between the full oligomers and the terminated ones. Both polystyrene- and TentaGel-supported libraries, including a library of 4913 pentaamines, were prepared and successfully decoded. For the TentaGel-supported libraries, suitable for on-bead aqueous screening of biomolecules, a novel trityl-derivatized resin was prepared in which the trityl group is anchored to the poly(ethylene glycol) chains via a methylene group. The resulting resin is much more resistant than other commercially available polystyrene-poly(ethylene glycol) trityl resins to the harsh borane reduction conditions required. Two workup conditions for the cleavage of the resultant borane-amine adducts were evaluated on the TentaGel bound polyamide 14. Although the two methods showed a comparable efficiency when using the polystyrene support, with 14 it was found that the piperidine-exchange method afforded polyamines of higher purity than the iodine-based oxidative method previously developed in our laboratory.

The synthesis and analysis of inorganic material combinatorial libraries by a directed-sorting, split-pool bead method was demonstrated. Directed-sorting, split-pool, metal-loaded libraries were synthesized by adsorbing metal salts (H2PtCl6, SnCl2, CuCl2, and NiCl2) and metal standards (Pt, Cu, Ni in HCl) onto 2-mg porous gamma-alumina beads in 96- or 384-well plates. A matrix algorithm for the synthesis of bead libraries treated each bead as a member of a row or column of a given matrix. Computer simulations and manual tracking of the sorting process were used to assess library diversity. The bead compositions were analyzed by energy-dispersive X-ray spectroscopy, X-ray fluorescence spectroscopy, electron probe microanalysis, inductively coupled plasma atomic emission spectroscopy, and inductively coupled plasma mass spectroscopy. The metal-loaded beads were analyzed by laser-activated membrane introduction mass spectroscopy (LAMIMS) for catalytic activity using methylcyclohexane dehydrogenation to toluene as a probe reaction. The catalytic activity of individual beads that showed minimal (approximately 20% of that of Pt on alumina) to high conversion could be determined semiquantitatively by LAMIMS. This method, therefore, provides an alternative to screening using microreactors for reactors that employ catalysts in the form of beads. The directed-sorting method offers the potential for synthesis of focused libraries of inorganic materials through relatively simple benchtop split-pool chemistry.