Molecular recognition Subject

The diacid dichlorides used so far in rotaxane synthesis all have arene building blocks in common. Nevertheless, the initial amide bond formed between the dichloride and one stopper molecule (cf. 54) is thought to be responsible for successful molecular recognition of the semi-axle and the macromonocycle. Consequently olefinic and aliphatic diacid dichlorides 59a-g were subjected to the threading procedure to test the need for arene units (Figure 25). 

Metal nanoparticles have extraordinary size-dependent optical properties, not present in the bulk metal and have, consequently, been the subject of intense research during the past decade or so.27 Attention has recently focused on functionalising colloidal nanoparticles with molecular recognition components for potential sensing applications.28,29,30 We have prepared a new amido-disulfide functionalised zinc metalloporphyrin (8) which was self-assembled on to gold nanoparticles to produce a novel anion-selective optical sensing system (9) (Scheme 3).4... 

A vast array of covalent molecules have been synthesised over the years in the search for LCs that show the useful cholesteric and ferroelectric smectic C phases, often on a trial and error basis ignoring the interactions between the molecules. The idea that one could think of the interactions between the molecules as a kind of molecular recognition came from the careful analysis of the conformations of molecules in the layers [77,78]. The arguments are based on the symmetry limitations of the angle formed by the alkyl chain and the phenyl benzoate moiety in the molecules that were the subject of this study. A molecular recognition site within the phase was used as the basis for these speculations , which have actually proved rather successful. The actual interactions between molecules are usually weak, but the formation of layers of aromatic and aliphatic units in these mesophases gives rise to their unique properties. 

We wished to develop a macroscopic model of the interactions between molecular ligands and receptors. Molecular recognition is a broad subject that describes selective assembly in chemistry and biology, with examples from DNA-protein complex formation to asymmetric catalysis. The principle behind molecular recognition dictates that the molecules that mate have complementary shapes and interfacial characteristics. Our extension of this principle to the mesoscale involved the self-assembly of objects that matched both... 

The efficiency of molecular recognition may be improved by creating additional hydrogen bonding sites in the Ti02-gel. As an example, a composite gel film was prepared from trimethoxysilane with a urea unit (TMS-PU) and Ti(0 BU)4. TMS-PU and Cbz-(3-Ala were mixed in organic solvent in the presence of water. After aging and addition of Ti(0 Bu)4, the stock solution was subjected to the surface sol gel process, and the template molecule was removed... 

In more recent years there is a development towards molecular recognition as a tool. Based on the increasing understanding of the weak forces between (macro) molecules we now see new concepts of material design. Chapters 1 to 3 cover three aspects of this development nanostructures that are formed by self-assembly of small molecules (chapter 1), dendritic structures (chapter 2) and polymers (chapter 3). A volume of a series like Perspectives in Supramolecular Chemistry can never claim to cover all aspects of a subject. All I can hope is that these chapters are representative of the filed of supramolecular technology. 

The reaction between the analjrte and the bioreceptor produces a physical or chemical output signal normally relayed to a transducer, which then generally converts it into an electrical signal, providing quantitative information of analytical interest. The transducers can be classified based on the technique utilized for measurement, being optical (absorption, luminescence, surface plasmon resonance), electrochemical, calorimetric, or mass sensitive measurements (microbalance, surface acoustic wave), etc. If the molecular recognition system and the physicochemical transducer are in direct spatial contact, the system can be defined as a biosensor [76]. A number of books have been published on this subject and they provide details concerning definitions, properties, and construction of these devices [77-82]. 

The author will be happy to share his collection of molecular-recognition-related references (titles, authors, journal details). This can be e-mailed in ASCII or WordPerfect 6.1 format. Please e-mail/fax your requests (e-mail, maitra orgchem.iisc.ernet.in fax, international code +91-80-334-1683). For a comprehensive treatment of this subject see Comprehensive Supramolecular Chemistry, J.-M. Lehn (Chairman, Editorial Board), 11 volume set, Elsevier Science, Oxford, 1996. 

---