Interaction small-molecule-macromolecular

The maximum value of ki is limited by the diffusion-controlled rate for collision between two molecules. For a small molecule binding to a macromolecular receptor, this rate is of the order of 10 to 10 M -s If the rates deviate from this markedly it suggests that the interaction of ligand with receptor is more complex. 

Supermolecules built from small molecules mainly involve intermolecular interactions. On the other hand, with macromolecules the supramolecular association may be either intermolecular, occurring between the large molecules, or intramolecular involving recognition sites located either in the main chain or in side-chain appendages, thus leading to chain folding and structuration of the macromolecular... 

Three different viewpoints on the humic substances structural conformation are actually reported in the literature. One suggests that HS are macromolecular and assume random coil conformations in solution (Swift, 1999) a second proposes that HS are molecular associations of relatively small molecules held together by weak interaction forces, thus forming a supramolecular structure (Piccolo and Conte, 1999) a third considers that HS are in solution as micelles or pseudomicellar structures (Wershaw, 1999). Viewpoints two and three could be broadly considered to be under the same umbrella (Clapp and Hayes, 1999). 

A similar chiral stimuli-responsive, macromolecular helicity inversion was also observed for (R)- or (S)-68 bearing an optically active (1-(1-naphthyl)ethyl)carbamoyl group by interacting with optically active small molecules, such as (R)- and (S)-39 (Fig. 15) [126]. The ICD of (R)-68 or (S)-68 in DMF changed to almost a mirror image in the presence of an excess of (R)-or (S)-39, respectively. Thus, optically active 39 can be used to regulate the helix-sense of 68. 

The object of this chapter is to provide the foundation necessary for understanding the interactions of small molecules (ligands, be they toxicants or drugs) with receptors, and also the fundamentals of the techniques commonly employed for such analysis. It should be noted that the same theory is also useful for understanding the interaction of two large molecules, and the application of similar theory to such problems has increased as the importance of macromolecular interactions has been realized in recent years. 

Dendritic architectures have attracted the interest of many scientists recently. The aesthetically pleasing tree-like moleeules combine advanced synthesis and unique properties with the prospects of supramolecular technologies. The guest-host properties of these well-defined macromolecules are of great interest, because they resemble the interactions of small molecules with biomacromolecules like proteins, and they are able to close the gap between the traditional supramolecular interactions of smaller molecules and the interactions in larger (phase-separated) macromolecular systems. In recent years a large number of interesting results have been reported, in which supramolecular interactions and dendritic architectures are combined. 

The hrst step toward this goal is to document the interactions. To this end, powerful tools have been developed to scan for macromolecular interactions. Arguably, the most significant and far-reaching of these methods is the yeast two-hybrid screen (1). Subsequent work has produced a host of thematic variations including the three-hybrid screen, a method first described explicitly in 1996 that employs small molecules or nucleic acids as baits (2). In this review, we discuss some strengths and... 

NMR screening. This involves the use of NMR to identify lead molecules that bind to a macromolecular target. These studies typically involve both small molecules and macromolecules and seek to detect the presence of binding interactions between them. 

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