Porphyrin derivatives, functional

Guanidium-Based Anion Receptors, p. 615 Hydrogen Bonding, p. 658 Hydrophobic Effects, p. 673 Molecular Clefts and Tweezers, p. 887 Porphyrin Derivatives, Functional, p. 1139 Steroid-Based Anion Complexation Agents, p. 1365 Troeger s Base Derivatives, p. 15 6 Zwitterion Receptors, p. 1639... 

Molecular-Level Machines, p. 931 O2 Uptake and Transport, Models of, p. 1023 Porphyrin Derivatives, Functional, p. 1139 Protein Supramolecular Chemistry, p. 1161 Vitamin Bj2 and Heme Models, p. 1569... 

Porphyrin Derivatives, Functional, p. 1139 Protein Supramolecular Chemistry, p. 1161... 

Enzymes Characteristics and Mechanisms, p. 554 Hemoglobins O2 Uptake and Transport, p. 636 Hydrogen Bonding, p. 658 Phthnlocyanines, p. 1069 Porphyrin Derivatives, Functional, p. i i 3 9... 

Secondly, we describe the site-selective introduction of a functional molecule, tetrakis-5,10,15,20-(4-carboxyphenyl)porphyrin (TCPP), into the microphase separation structure of a diblock copolymer film of PS-fo-P4VP. Since porphyrin derivatives show various functionalities such as sensitization, redox activity, and nonlinear optical effect, a polymer nanodot array containing a porphyrin at a high concentration would be applicable to a light-harvesing and charge transporting nanochannel. 

Finally, we should note that a particularly important area of application where density functional techniques, in spite of the deficiencies noted above, are virtually without competition is provided by biochemically relevant molecules, such as enzymes or nucleic acids. The techniques discussed in this section are virtually the only quantum chemical methods which can be applied in this context due to their outstanding price/performance ratio. For example, the 13C and 15N chemical shifts in bacteriochlorophyll A have been studied by Facelli, 1998, and in another investigation the 57Fe, 13C and 170 shifts in iron porphyrin derivatives gave important clues as to the structural details of these species, as shown by McMahon et al 1998. 

While indirect selections work quite well for antibodies they have been less successful in the case of catalytic nucleic acids. There are only three examples which prove that it is possible in principle to obtain a ribo- or deoxyribozyme by selecting an aptamer that binds to a TSA A rotamase ribozyme [7], a ribozyme capable of catalyzing the metallation of a porphyrin derivative [92], and one catalytic DNA of the same function [93]. Another study reported the selection of a population of RNA-aptamers which bind to a TSA for a Diels-Alder reaction but the subsequent screen for catalytic activity was negative for all individual RNAs tested [94]. The attempt to isolate a transesterase ribozyme using the indirect approach also failed [95]. 

The most important porphyrin derivatives are characterized by a central metal atom hemin is the iron-containing porphyrin essential to mammalian blood, and chlorophyll is the magnesium-containing porphyrin that catalyzes photosynthesis. Other derivatives include rhe cytochromes, which function in cellular metabolism, and the phthalocyanme group of dyes, Porphyrins are described in considerable detail m a 20-volume set of books, The Porphyrin Handbook, Academic Press, New York, NY, 2003. 

Closely related to the ionic polymerization of heterocyclic monomers is, what we can call, pseudoionic polymerization (or sometimes, perhaps, cryptoionic). We use the preffix pseudo- in the same meaning as it was first used in the vinyl cationic polymerization. It means that propagation actually proceeds on the covalent species that could have been in equilibrium with their ionic counterparts. Several systems falling to this category have recently been described for both anionic and cationic polymerization of heterocyclics. In the anionic processes derivatives of Zn or A1 alkyls or alcoholates are believed to function this way. However, for none of these systems the absence of ionic contribution was shown. Two catalytic systems are of particular interest, namely the -Zn-O-AK systems (20) and>Al-alkyl modified by bulky porphyrin derivatives (21). Both are discussed in this volume and both have been clearly shown to produce living systems. The former with e-caprolactone and the latter... 

A nudeobase derivative, 9-ethyladenine-imprinted polymer capable of spectroscopic change based upon molecular recognition has also been prepared using the zinc(II) porphyrin-based functional monomer [25]. 

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