Molecular complexes macromolecules

Delaite, E., Point, J. J., Damman, P, Dosihre, M. Two allotropic forms for the poly (ethylene oxide)-resorcinol molecular complex. Macromolecules, 25, 4768-4778 (1992). 

From the atomic to the macroscopic level chirality is a characteristic feature of biological systems and plays an important role in the interplay of structure and function. Originating from small chiral precursors complex macromolecules such as proteins or DNA have developed during evolution. On a supramolecular level chirality is expressed in molecular organization, e.g. in the secondary and tertiary structure of proteins, in membranes, cells or tissues. On a macroscopic level, it appears in the chirality of our hands or in the asymmetric arrangement of our organs, or in the helicity of snail shells. Nature usually displays a preference for one sense of chirality over the other. This leads to specific interactions called chiral recognition. 

From a chemical point of view, the half-life of fluorine-18 allows multi-step synthetic approaches that can be extended over hours. Fluorine-18 has therefore, in spite of its somewhat limited chemical repertoire, been effectively used for the labelling of numerous both relatively simple and complex bioactive chemical structures [3,5-9], including high-molecular-weight macromolecules such as peptides, proteins [10-13] and oligonucleotides [14-18]. General considerations on radiochemistry involving short-lived positron emitters will be discussed in Section 2.3. 

Nagarajan R, Tripathy S, Kumar J, Bruno EE, Samuelson L (2000) An enzymatically synthesized conducting molecular complex of polyanUine and poly(vinyl phosphonic acid). Macromolecules 33(26) 9542-9547... 

Activation energies are energy barriers to chemical reactions. These barriers are crucial to life itself. The rate at which a molecule undergoes a particular reaction decreases as the activation barrier for that reaction increases. Without such energy barriers, complex macromolecules would revert spontaneously to much simpler molecular forms, and the complex and highly ordered structures and metabolic processes of cells could not exist. Over the course of evolution, enzymes have developed lower activation energies selectively for reactions that are needed for cell survival. 

Molecular Complexes. These species are formed by noncovalent interactions between the substrate and ligand. Among the kinds of complexspecies included in this class are small molecule-small molecule complexes, small molecule-macromolecule species, ion-pairs, dimers and other self-associated species, and inclusion complexes in which one ofthe molecules, the host, forms or possesses a cavity into which it can admit a guest molecule. 

Other peculiar conditions of the rhizosphere, such as ion concentration, can influence the molecular complexity of humic substances, due to the possibility of the formation of interchain bonds producing insoluble macromolecules (Sequi et al., 1975). This latter aspect underlines the need of a dynamic evaluation of the processes occurring in the rhizosphere in relation to the activity and the physiological status of the plant. 

Tsuchida, E., and Abe, K. "Interactions between macromolecules in solution and intermacro-molecular complexes". Adv. Polym. Sci. 45, 1-119 (1982). 

The repair and replication of cells involves metabolism - interconversions of hundreds of low molecular weight metabolites that ultimately yield the precursors for much larger, more complex macromolecules such as phospholipids (based on phosphatidic. acids or long chain fatty acid esters of glycerol phosphate), polynucleotides such as RNA and DNA (polymers of nucleotide monomers), proteins (polypeptides or amino acid monomers linked by peptide bonds) and polysaccharides (polymers of simple sugars or monosaccharides). 

Yasuda, H., Yamamoto, H., Yamashita, M. et al. (1993) Synthesis of high molecular weight poly(methyl methacrylate) with extremely low polydispersity by the unique function of organolanthanide(lll) complexes. Macromolecules, 26, 7134. 

Now, the word fragment is beginning to make a dominant appearance. In diverse instances, smaller molecular entities derived from an important and complex macromolecule are found to have similar biochemical functions as the prominent parent, sometimes displaying one of the parent s several (desirable and undesirable) functions. 

As a rule, the weak coupling case is observed in solution, the intermediate coupling case in crystalline solids and oriented membranes, and the strong coupling case within conjugated macromolecules. In order to quantify the energy transfer, we will consider a molecular complex composed of two molecules a and b. The Hamiltonian of this system is given by... 

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