Combinatorial libraries bead-based

W. J., Cavallaro, C. L., Roughton, A. L., Zhao, W., Reader, J. C., Orlowski, M., Jacob-Samuel, B., Dilanni Carroll, C. (2000) A statistical-based approach to assessing the fidelity of combinatorial libraries encoded with electrophone molecular tags. Development and application of tag decode-assisted single bead LC/MS analysis. J Comb Chem 2, 716-731. 

IR spectroscopy is a fast, simple, and cheap method for the qualitative detection of certain functional groups on insoluble supports [77-79]. Dried supports can be used directly to prepare KBr pellets for standard recording of IR spectra [54,80-82], Newer IR-based techniques, which require much less support material than required for a KBr pellet, include single-bead FT-IR spectroscopy [16,77,83-86], single-bead Raman spectroscopy [87], near-IR multispectral imaging [88], and the simultaneous analysis of several different beads by FT-IR microscopy for analysis of combinatorial libraries [89,90],... 

Recently we have employed the COPAS Biobead bead sorter (Union Biometrica, Somerville, MA) to isolate positive beads from combinatorial libraries. Combinatorial libraries are incubated as described above with a fluorescently tagged protein. The beads are washed to remove unbound proteins and then sorted based on the fluorescence intensity of the protein bound to individual beads. Combinatorial beads can be sorted at a rate of 50-100 thousand beads per hour and the positive beads dispensed into 96-well plates. If necessary, the combinatorial beads can be prescreened to remove beads with excessive fluorescence background. 

Fenniri H, Hedderich HG, Haber KS, Achkar J, Taylor B, Ben-Amotz D, Towards the DRED of resin-supported combinatorial libraries a noninvasive methodology based on bead self-encoding and multispectral imaging, Angew. Chem. Int. Ed., 39 4483-4485, 2000. 

The OBOC combinatorial library method is highly versatile and economical. It also is a form of chemical microarrays. Many investigators successfully have applied the on-bead screening methods in their research. The solution-phase and cell-based assays for OBOC libraries, however, are much less developed and have been applied successfully in only a few laboratories. A need exists to develop robust methods that allow investigators to screen routinely huge OBOC releasable peptide or chemical libraries (e.g., 200,000 compounds) with multiparametric... 

Liu R, Marik J, Lam KS. A novel peptide-based encoding system for one-bead one-compound peptidomimetic and small molecule combinatorial libraries. J. Am. Chem. Soc. 2002 124 7678-7680. 

A special case of parallel synthesis is the spatially addressable synthesis pioneered by Fodor et al. [17,18] in 1991. Here, each member of the library is synthesized at a specific location on a functionalized silica wafer rather than on resin beads in separate reaction vessels. This approach, based initially upon solid-phase peptide synthesis and semiconductor photolithographic techniques by using photolabile amino protecting groups, allows the synthesis of combinatorial libraries containing about 50000 compounds localized to a 50 pm square site on a silica wafer ( library on a chip ). 

If combinatorial libraries consist of compound mixtures (e.g., after cleavage from the resin beads), a reliable analytical characterization is difficult. In this case the utilization of mass spectrometry for analysis is based on the prediction of mass distribution of the library. Computer-generated distribution profiles can be compared with the actual profile obtained from the compound library [93,94]. Evaluation of mass distribution detects synthetic problems based on incomplete coupling (shift toward lower molecular masses), incomplete deprotection, or unwanted library modification, such as oxidation, acylation, or alkylation (shift toward higher molecular masses). However, for a larger library of compound mixtures many different compounds will have the same molecular mass. This greatly complicates structural determination and even makes it impossible at a certain mixture complexity. 

Since the introduction of solid-phase peptide synthesis by Merrifield (1) nearly forty years ago, solid-phase techniques have been applied to the construction of a variety of biopolymers and extended into the field of small molecule synthesis. The last decade has seen the emergenee of solid-phase synthesis as the leading technique in the development and production of combinatorial libraries of diverse compounds of varying sizes and properties. Combinatorial libraries can be classified as biopolymer based (e.g., peptides, peptidomimetics, polyureas, and others [2,3]) or small moleeule based (e.g., heterocycles [4], natural product derivatives [5], and inorganie eomplexes [6,7]). Libraries synthesized by solid-phase techniques mainly use polystyrene-divinylbenzene (PS) derived solid supports. Owing to physieal and ehemical limitations of PS-derived resins, other resins have been developed (8,9). Most of these resins are prepared from PS by functionalizing the resin beads with oligomers to improve solvent compatibility and physical stability (8,9). 

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