Non-Covalent Intermolecular Interactions

This book, Highlights in Bioorganic Chemistry, describes exciting recent advances in all the aspects of the field. Part 1 deals with Biomolecules and their Conformations. Chapters on the natural chemistry of RNA, of / -amino acids, on binding to DNA, on nucleic acid polymerases, on ribozymes and proteases, are concerned with using chemistry tools to help us understand biological chemistry. Part 2 deals with Non-Covalent Intermolecular Interactions. Here there is work on... 

The issue of dimerization of type C (glutamate receptor class) is clearly set. Type C GPCRs form dimers by covalent linkage of disulfide bond at their extracellular N-terminal domains (e.g. metabotropic glutamate receptor) or by strong non-covalent, intermolecular interactions (e.g. two y-aminobutyric acid, GABA, receptor subtypes). But is dimerization state also required for their function ... 

Conventionally, MlPs are obtained by bulk co-polymerization from a mixture consisting of a functional monomer, cross-linker, chiral template, and a porogenic solvent mixture. Nowadays, imprinting via non-covalent template binding is preferred over the covalent mode and involves three major steps (see Fig. 9.9). (i) Functional monomers (e.g. methacrylic acid, MAA) and a cross-linker (e.g. ethyleneglycol dimethacrylate, EDMA) assemble around the enantiomeric print molecule, e.g. (S)-phenylalanine anilide (1), driven by non-covalent intermolecular interactions, e.g. ionic interactions, hydrogen bonding, dipole-dipole interaction. Tr-rt-interaction. (ii) By thermally or photochemi-... 

The use of intermolecular forces in concert with coordination interactions as discussed in Section V.B.7 has led to receptors with novel anion selectivities. In the next sections, we examine receptors that function primarily through non-covalent intermolecular interactions. 

There has been considerable interest in recent years in the formation of condensed films of purine and pyrimidine bases at the solid-liquid interface. It is well recognised that non-covalent affinities between base pairs play a prevalent role in determining nucleic acid conformation and functionality. Likewise, there has been interest in the role of substrate and non-covalent intermolecular interactions in the configuration of ordered monolayers of purine and pyrimidine bases. There is also more general interest in the interaction of bases with metal surfaces and metal complexes. In the latter case it is noted that the biological role of nucleic acids and certain nucleotides are dependent on metal ions, particularly Mg, Ca, Zn, Mn, Cu and Ni. " Also certain metal complexes, notably of platinum, have the anti-tumour activity, which is linked to their ability to bind to bases on DNA. On a different note, the possibility that purine-pyrimidine arrays assembled on naturally occurring mineral surfaces might act as possible templates for biomolecular assembly has been discussed by Sowerby et al. 

Such a description encompasses the whole field of liquid crystals, where it is non-covalent, intermolecular interactions which determine the molecular organization leading to the various liquid crystalline phases or, in the extreme, to a totally disordered isotropic phase [2], The science of liquid crystals is really the art of balancing the various intermolecular interactions to achieve a desired liquid crystal phase rather than an ordered crystalline phase. Nature demonstrates this art in its highest form in the self-organization of lipids to produce liposomes and cellular membranes. 

Owing to high theoretical plate numbers, CE makes it possible to observe even very weak (enantio) selective effects in intermolecular interactions that are not detectable using other techniques. This important advantage of CE is not yet effectively exploited for studies of non-covalent intermolecular interactions. 

It must be remembered that crystal structures afford experimental observations of non-covalent intermolecular interactions, through the operation of space-group symmetry on the atomic coordinates of the asymmetric unit. Thus, 3D searching in QUEST3D is available at both the molecular level, e.g., in conformational studies or in the location of pharma-cophoric patterns, and at the extended (crystal structure) level, e.g., to locate the hydrogen-bonded interactions of chemical functional groups. 

Furthermore, we succeeded in the tmiform alignment between the ITO electrodes and gold comb electrodes in this two-component system liquid crystal and found that the ion conductivity parallel to the smectic layer structure is about 3,000 times higher than in the perpendicular direction. We could also easily adjust the ionic conductivity and the phase transition temperature by changing the composition mixture [172]. It is a great advantage to use such mixtures that form assembled structures by non-covalent intermolecular interactions. 

Molecular chemistry has, thus, established its power over the covalent bond. The time has come to do the same for non-covalent intermolecular forces. Beyond molecular chemistry based on the covalent bond, lies the field of supramolecular chemistry, whose goal it is to gain control over the intermolecular bond [4-7]. It is concerned with the next step in increasing complexity beyond the molecule towards the supermolecule and large organized molecular systems, held together by non-covalent interactions. 

Two species combine to form a complex in water if the sum of the intermolecular forces between them more than olfsets the sum of the loss of favorable interactions with solvent and any unfavorable interactions that develop between solutes during complex formation. Collectively the interactions between non-bonded species are referred to as cohesive forces, defined as those forces lost when the species are transferred to infinite separation in the gas phase. While it is common to classify chemical forces as covalent or non-covalent, the interactions are fundamentally the same only the magnitude of the interactions varies. Cohesive, non-specific forces are weak compared to covalent interactions typically we consider cohesive forces as those forces with strengths less than 1% of covalent bond strengths. We will see, however, that this definition is somewhat arbitrary and in fact a continuum of interaction energies exists. 

---