Combinatorial Chemistry Review

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A molecule having a molecular weight in the range of a few thousand to many millions: proteins, nucleic acids and polysaccharides.

Macroporous Resin
Polymer which contains a permanent network of pores independent of the state of swelling of the resin. This class of resin thus displays much better solvent tolerance than gel-type resins.

Mass Spectrometer
A spectroscopic device in which the masses of particles, ions, and isotopes are measured. It separates isotopes according to charge and mass.

Device which acts as a barrier to the passage of a reagent (often light). A pattern of holes in the mask allows selective passage of reagent and results in a corresponding pattern of reagent deposition or photodeprotection on a surface placed behind the mask. This allows the generation of spatially addressable libraries.

Medicinal Chemistry
A chemistry-based discipline, also involving aspects of biological, medical and pharmaceutical sciences. It is concerned with the invention, discovery, design, identification and preparation of biologically active compounds, the study of their metabolism, the interpretation of their mode of action at the molecular level and the construction of structure-activity relationships.

a) Specific compound which is included in a library;
b) the uncharacterized physical product of a library synthesis.

Member of a building block set which can be repeatedly incorporated into a library to give a set of compounds of repeating structure, e.g. amino acids in a peptide library.

Chemical compounds or functional groups or portions of those compounds.

Molecular Modeling
A technique for the investigation of molecular structures and properties using computational chemistry and graphical visualization techniques in order to provide a plausible three-dimensional representation under a given set of circumstances.

Nuclear Magnetic Resonance (NMR)
NMR spectroscopy makes it possible to discriminate nuclei, typically protons, in different chemical environments. The electron distribution gives rise to a chemical shift of the resonance frequency. The chemical shift of a nucleus is expressed in parts per million (ppm) by its frequency, n, relative to a standard, ref, and defined as = 106 (n - ref)/o, where o is the operating frequency of the spectrometer. It is an indication of the chemical state of the group containing the nucleus. More information is derived from the spin-spin couplings between nuclei, which give rise to multiplet patterns. Greater detail may be derived from two- or three- dimensional techniques. These use pulses of radiation at different nuclear frequencies, after which the response of the spin system is recorded as a free- induction decay (FID). Multidimensional techniques, such as COSY and NOESY, make it possible to deduce the structure of a relatively complex molecule such as a small protein (molecular weight up to 25,000).

Null Reagent
Concept whereby one of a set of pools is subjected to no reaction at a particular stage of a combinatorial synthesis. It is often necessary to record this as a null event to maintain congruence in computational records of the library.

Omission Library
Strategy for identifying active library members by the systematic omission of building blocks from mixtures. Observation of reduced activity in a certain pool suggests that the building block which was omitted in that pool contributes to activity.

a) Property of protecting groups or linkers allowing removal, modification or cleavage of one such without affecting others;
b) pooling strategy whereby library members are incorporated in more than one pool, and are mixed with a different set of other members in each pool. Thus a hit results in two or more active pools with only one member in common.

The process of synthesizing chemical variations, or analogs, of a lead compound, with the goal of creating those compounds with improved pharmacological properties.