Key-lock interactions

Figure 23. Key-lock interactions assist the molecular recognition of wheel and axle in the threading approach.

The von Smoluchowski scheme based on Equations 5.326 and 5.327 has found numerous applications. An example for biochemical application is the study of the kinetics of flocculation of latex particles caused by human gamma globulin in the presence of specific key-lock interactions. The infinite set of von Smoluchowski equations (Equation 5.319) was solved by Bak and Heilmann in the particular case when the aggregates cannot grow larger than a given size an explicit analytical solution was obtained by these authors. 

Fig. 13.20. The key-lock interaction in two marginally different situations the molecules (in center) involved differ by replacing some of the hydrogens by the fluorine atoms in the substituent R. This picture shows how profound the consequences of this seemingly small detail are. In one case (left), we obtain a eonelike molecule and then a crystal of cubic symmetry in the other (right), the molecirle has a plateUke shape, and because of thaL we get finally a liquid crystal with the hexagonal packing of columns of these molecirlar plates [after Donald A.TomaUa, Nature Materials, 2,711(2003)].

Bioaffinity chromatography means that solute components which have a very specific and selective interaction with the adsorbent are separated into fractions with a high purity. Sometimes this selective bonding is based on a steric effect (key-lock-interaction) but also an equilibrium or kinetic effect can be applied for separation. As a mle also a specific eluent is necessary for regeneration. 

Jeziorski-Kolos perturbation theory (p. 796) key-lock interaction (p. 874) many-body expansion (p. 848) molecular surface (p. 860)... 

In the following, only chemical and biochemical sensors are considered They make use of specific "key-lock" interactions which convert chemical to electronic information Three different tasks are usually fulfilled by chemical sensors, i e the quantitative and selective determination of individual particles (such as molecules or ions in gases or liquids), the determination of gross parameters (such as toxicity), or the quantitative characterization of odors (such as smells monitored qualitatively by the human nose) These requirements can only be achieved with sensor systems which in the most general case contain ten components for analyzing gases or liquids [4]... 

This will be illustrated now briefly for typical sensor materials which show characteristic "key-lock" interactions to detect and identify particles Particular emphasis will be put on the discussion of ultimate limits in the miniaturization of sensor... 

This abstraction is based on the key-lock principle introduced by Emil Fischer in 1894. According to this principle, the interaction of a biological entity with a molecule is best when both species behave like a key and a lock. If we now extend this principle to pharmaceuticals, then the drug molecule is the key. Certain... 

More than 100 years ago (1894), Emil Fischer proposed a Key and Lock theory as to the specific substrate selectivity by the enzyme, which is presently understood as molecular recognition of the substrate by the enzyme through supramolecular interactions. If the enzymatic reaction takes place in vivo, it is always involved to recognize the substrate by the enzyme. This is also true for enzymatic reactions in vitro. However, readers will see in this article that the substrate—enzyme relationship is not as strict as the key—lock relationship, but enzymes are dynamic and sometimes very generous in recognizing even unnatural substrates in vitro. This situation allows enzymes to catalyze the synthesis of not... 

The underlying principle of the analytical methods described in this chapter is that of biomolecular recognition the ability of a biomolecule to interact with one other particular type of biomolecule, like a key fitting a lock. With this key-lock principle, it is possible to specifically detect the target molecule, which could be an antigen, an antibody, a hormone, a DNA fragment or a sugar, even in very complex sample mixtures like urine or untreated blood. 

If such rigid molecules A and B match perfectly each other, this corresponds to the key-lock type of molecular recognition. To match, the interacting molecules sometimes only need to orient properly in space when approaching one another and then dock (the AT or GC pairs may serve as an example). This key-lock concept of Fischer from 100 years ago (concerning enzyme-substrate interaction) is considered as the foundation of supramolecular chemistry -the chemistry that deals with the complementarity and matching of molecules. 

Some intermolecular interactions are specific i.e., a substrate A interacts with a particular molecule B from a set Bi, B2,... Bjv (Ai is large) mueh more strongly than with others. The reasons for this are their shape, the electric field fitness, a favorable hydrophobic interaction, etc., resulting either in the key-lock , template or hand-glove types of interaction (cf. Chapter 13). A molecule may provide a set of potential contacts localized in space (called a synthon), which may fit to another synthon of another molecule. 

KEY-LOCK , TEMPLATE AND HAND-GLOVE SYNTHON INTERACTIONS... 

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