Molecular recognition processes characteristics

In most cases, separation and purification via crystallization are highly selective due to the fact that molecular recognition process at the crystal-solution interface acts in such a way as to select the host molecules and reject impurities. However, sometimes the solute and impurity molecules are not discriminated at certain crystal faces, especially when the impurity has many of the structural and chemical characteristics of the primary solute but differs only in some specific way. A systematic approach toward understanding the effects of such impurities on crystal growth has been developed using the concept of tailor-made additives (Weissbuch et al. 2003). These additives are structurally similar to the solute molecules and are basically composed of two moieties. The first, known as the binder, has a similar structure (and stereochemistry) to that of the substrate molecule on the crystal surface where it adsorbs. The second, referred to as the perturber, is modified when compared with the substrate molecule and thus hinders the attachment of the oncoming solute molecules to the crystal surface. Several classic examples in the literature highlight this type of interaction mechanism in molecular crystals. 

Nucleic acids, proteins, some carbohydrates, and hormones are informational molecules. They carry directions for the control of biological processes. With the exception of hormones, these are macromolecules. In all these interactions, secondary forces such as hydrogen bonding and van der Waals forces, ionic bonds, and hydrophobic or hydrophilic characteristics play critical roles. Molecular recognition is the term used to describe the ability of molecules to recognize and interact bond—specifically with other molecules. This molecular recognition is based on a combination of the interactions just cited and on structure. 

The molecular recognition of anionic guest species by positively chaiged or neutral receptors is a relatively new area of research of growing interest in view of the key roles that these anions play in biochemical and chemical processes. For this reason, as part of the electrochemical studies, we decided to examine the use of the redox-active ferrocenyl dendrimers 3 and 4 that contain multiple N-H linkages capable of participating in H-bonding, as well as characteristic internal cavities,... 

The most characteristic properties of enzymes which distinguish them from other chemical catalysts are those associated with their specificity. It is well recognized that binding of a substrate to an enzyme takes place at an active site containing the catalytic function and that formation of an enzyme-substrate complex always precedes the catalytic process. Therefore, enzyme-substrate interaction is generally realized to be one of the most crucial processes in the sense that accurate molecular recognition is involved. 

Pseudorotaxanes may be involved in electron transfer processes from three different viewpoints (i) the recognition process between the thread and the macrocycle may result from a charge-transfer interaction, which implies the appearance of characteristic spectroscopic and electrochemical properties (ii) the pseudorotaxane structure can be dethreaded/rethreaded by chemically, electrochemically, and pho-tochemically induced electron transfer processes, which leads to the concept of molecular machines and (iii) dethreading/rethreading of pseudorotaxanes can control the occurrence of charge transfer and electron transfer processes, which offers a route to information processing at the molecular level. 

New and highly efficient synthetic routes have generated many porphyrinlike compounds with unique characteristics for their uses in several other applications like oxidative catalysis [ 19,20] and as biomimetic model systems of the primary processes of photosynthesis [21,22]. Presently, the interest includes also the supramolecular units, including molecular recognition in chemical receptors and sensors [23-25], use as light-harvesting devices [26-29], and as materials for advanced technologies, mainly in nanosciences [30, 31]. 

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