Interaction in Biological Systems

Most life processes involve chiral molecules and discrimination can be expected to be a common feature of the interactions. We refer here first to two special aspects, in the physiological responses of taste and odor. More than a century ago Pasteur noted that the (- -) and (—) forms of asparagine tasted differently — the former sweet, the latter insipid or almost tasteless. Since then, the often widely different physiological effects of (+) and (—) forms of various natural and synthetic compounds have been brought to light. 

Under the heading of taste two classes of compounds only will be discussed, namely amino acids and sugars. The difference between the taste of (-f-) and (—) forms of amino acids, first noted by Pasteur, has proved to be a general one. This is illustrated in Table 6 where taste is correlated with absolute configuration rather than the sign of the optical rotation of enantiomeric pairs. Amino adds 

1) Glycine, the first member of the a amino acid series, is achiral. 

Of related S3mthetic compounds, one of the most interesting is (+)-6-chloro-tryptophane, which according to Kornfeld [see Chedd, (1974)] is 1000 times sweeter than sucrose all the sweetness resides in the unnatural (+) isomer . 

Friedman and Miller also established that synthetic R-(+) and S-(— ) limo-nene have the odor of oranges and lemons respectively. They also demonstrated the differences between other enantiomeric pairs such atR-(-f-) andS-(—) amphetamine. There remains no doubt that some enantiomeric pairs do have different odors. Whatever the nature of the sensory detector involved, it must, in order to be able to discriminate between enantiomeric pairs, itself be locally chiral. Hence 

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Interactions between macromolecules (protems, lipids, DNA,.. . ) or biological structures (e.g. membranes) are considerably more complex than the interactions described m the two preceding paragraphs. The sum of all biological mteractions at the molecular level is the basis of the complex mechanisms of life. In addition to computer simulations, direct force measurements [98], especially the surface forces apparatus, represent an invaluable tool to help understand the molecular interactions in biological systems. 

Section 2 mainly focuses on the current efforts to improve the accuracy of quantum calculations using simplified empirical model forms. McNamara and Hillier, in Chapter 5, summary their work on improving the description of the interactions in biological systems via their optimized semiempirical molecular models. Piquemal and co-workers present recent advances in the classical molecular methods, aiming at better reproduction of high-level quantum descriptions of the electtostatic interactions in Chapter 6. In Chatper 7, Cui and Elstner describe a different semiempir-... 

In recent years, with increasing recognition of the roles played by specific noncovalent interactions in biological systems and chemical processes, the science of noncovalent assemblies- often called supramolecular science- has aroused considerable interest [76], The remaining part of this article reviews some important studies made on rotaxane and catenane, two classic types of supramolecular structure. 

M. Mammen, S.-K. Choi, and G. M. Whitesides, Polyvalent interactions in biological systems Implications for design and use of multivalent ligands and inhibitors, Angew. Chem. Int. Ed. Engl., 37 (1998) 2754—2794. 

A. Ben-Naim, Hydrophobic interactions in biological systems, Top. Mol. Pharmacol. 2 1... 

First model for oscillating system was proposed by Volterra for prey-predator interactions in biological systems and by Lotka for autocatalytic chemical reactions. Lotka s model can be represented as... 

Magnusson G (1986) Synthetic neo-glycoconjugaters. In Lark D (ed) Protein-carbohydrate interactions in biological systems. Academic Press, London, p 215 Schnaar RL (1984) Anal Biochem 143 1 Pazur J (1981) Adv Carbohydr Chem Biochem 39 405 Roy R (1996) Polymers News 21 226 Duncan R, Kopecek J (1984) Adv Polymer Sci 57 51... 

Opioids is the common name for all compounds which have the same mode of action as the constituents of opium, the dried milky liquid of the poppy seed, Papaver somniferum (Brownstein, 1993). All opioids interact in biological systems with the same type of receptor, the so-called opioid receptor. 

Magnusson G (1986) Synthetic neo-glycoconjugaters. In Lark D (ed) Protein-carbo-hydrate interactions in biological systems. Academic Press, London, p 215... 

Varying the side groups X in 27b affects both the stability and selectivity of the complexes (lateral discrimination), and allows the receptor-substrate interactions in biological systems to be modelled, for instance, the interaction between nicotinamide and tryptophan [2.109b]. One may attach to 27b amino acid residues (leading to parallel peptides [2.109] as in 27c), nucleic acid bases or nucleosides, saccharides, etc. The structural features of 27 and its remarkable binding properties make it an attractive unit for the construction of macropolycyclic multisite receptors, molecular catalysts, and carriers for membrane transport. Such extensions require sepa-... 

Morel I, Cillard P, Cillard J. 1998. Flavonoid-metal interactions in biological systems. In Rice-Evans CA, Packer L, Eds. Flavonoids in Health and Disease. New York Marcel Dekker, pp. 163-197. 

The importance of non - covalent interactions in biological systems has motivated much of the current interest in supramolecular assemblies [1]. A classical example of a supermolecule has been provided by the rotaxanes [2,3], in which a molecular rotor is threaded by a threaded by a linear axle . Another examples have been previously included as cyclic crown ethers threaded by polymers, paraquat -hydroquinone complexes [4] and cyclodextrin complexes [5,6],... 

Molecular recognition, defined as the favored binding of a molecule (i.e., a substrate) to a specific site in a receptor over other structurally and chemically related molecules, is at the forefront of science.1 s Long before man walked on this earth, nature had succeeded in the creation of a series of biologically based recognition elements with unmatched specificity antibodies, enzymes, and receptors. Perhaps the simplest well-known example of this concept is the lock and key hypothesis that has been used to describe protein-substrate interactions in biological systems.5-7... 

A. Warshel, S. T. Russell, Quart. Rev. Biophys. 17, 283 (1984). Calculations of Electrostatic Interactions in Biological Systems and in Solutions. 

SIGNIFICANCE OF MULTIVALENT BINDING INTERACTIONS IN BIOLOGICAL SYSTEMS... 

Zhao Y, Truhlar DG (2005b) How well can new-generation density functional methods describe stacking interactions in biological systems, Phys Chem Chem Phys, 7 2701-2705... 

Our approach to understanding the role of the hydrogen bond in determining the three-dimensional structure of molecular shapes and interactions in biological systems is analogous to the modern meaning of epidemiology. That is, the prediction of the most probable behavior by means of surveys of the behavior of similar species, or the same species in different habitats. 

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