Theme and Variations

This theme can be varied in an infinite number of ways  

A geometric illustration of the possible variations of a synthetic theme is shown in Fig.1.4. The different axes of the reaction space and the experimental space can for the moment be regarded just as variations . In the chapters to follow, we shall see that these axes can be quantified to describe multidimensional variations. 

The trouble is that these possible variations of the reaction theme are not independent. 

To be able to discern all the important factors involved in determining the result of any reaction, it is necessary to use proper experimental designs. 

When a reaction mechanism is known, it is sometimes possible to deduce, by theoretical reasoning, how a good result could be achieved. However, with new reactions, mechanistic details are still obscured and it is not likely that such details will be revealed before the utility of the reaction has been demonstrated. This implies that the scope and lixnitations of the reaction and of the optimun experimental conditions must be determined before mechanistic details are known with certainty. Thus, the desired information must be obtained by inferences from experimental observations. It is therefore desirable that the required information on which factors are important can be adequately obtained, if possible with a minimum of effort. This implies requirements on the 

A very popular form of music at the end of the 18th and the beginning of the 19th century was the Theme and variation , and we use this as a metaphor to describe the problems encountered when a synthetic reaction is studied. The theme , which applies to any synthetic reaction, would be 

The situation is further complicated since in addition to the possible discrete changes, each reaction system can be subjected to innumerable variations of the 

The observed result of an experimental called the response. The yield of the desired product is often the most important response and is sometimes used as a single criterion of success. It is, however, common that several responses are of interest, e.g. yields of byproduct, selectivity, cost for producing a given quantify of product. When several responses are considered we will also have to consider variations in a multidimensional response space, see Fig. 1. 

This means that optimization in the general case will imply the exploration of the reaction space with a view to finding a suitable reaction system for carrying out the desired transformation followed by adjustment of the experimental conditions toward an optimum result with respect to the observed response(s). 

The interdependence of the possible variations makes it mandatory to use strategies which can take the joint influence of all factors simultaneously into account, i.e. to use multivariate methods. To be able to detect interaction effects it is necessary to design the experiments in such a way that the pertinent factors are varied simultaneously. 

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R Cammack. Eon-sulfur cluster in enzymes Themes and variations. Adv Inorg Chem 38 281-322, 1992. 

Dasso M (2002) The Ran GTPase theme and variations. Curr Biol 12 R502-R508... 

Jakupec, M. A., Galanski, M., Arion, V. B., Hartinger, C. G. Keppler, B. K. Antitumor metal compounds more than theme and variations. Dalton Trans., 183-194 (2008). 

Segal, R. A. Selectivity in neurotrophin signaling theme and variations. Annu. Rev. Neurosci. 26 299-330,2003. 

Rochet, J. C., and Lansbury, P. T., Jr. (2000). Amyloid fibrillogenesis Themes and variations. Curr. Opin. Struct. Biol. 10, 60-68. 

Weissman, A.M. (2001). Themes and variations on ubiquitylation. Nature Reviews Cell Mol. Biol. 2, 169-178. 

D. Thiramalai and C. Hyeon, RNA and protein folding common themes and variations. Biochemistry 44, 4957 970 (2005). 

Iron-Sulfur Clusters in Enzymes Themes and Variations Richard Cammack... 

A. Marra, J. Esnault, A. Veyrieres, and P. Sinay, Isopropenyl glycosides and congeners as novel classes of glycosyl donors Theme and variations, 7. Am. Chem. Soc. 774 6354 (1992). 

MacAdam. D.L. Color Measurement Theme and Variations. Springer-Verlag Inc.. New York, NY, 1985. 

Fig. 13.5. This figure is a summary of the various postulates of the genomic potential hypothesis. Coding sequences evolve from straight chemistry in innumerable pools on the earth s surface to provide a nearly unlimited reservoir of nucleic acid polymers which form themes and variations that are taken up by the various foci of cell formation. Once a cell has formed, it never loses its basic character, remaining either a micro-organism or developing a potential for a large animal during this 3.5 million years of the Archean period which would show up at varying times after the Cambrian period. Each new species eventually appears from its own pro- form and persists until the present or extinction.

The most common anesthetic gases are halogenated ethers. Notice the theme-and-variation relationship between these compounds. Researchers moved and exchanged halogen atoms around on the same basic skeleton in a systematic attempt to fine-tune the physiological properties of the substance. Figure 11.26 lists some common anesthetic ethers. 

Robert, F., Winum, J.-Y., Sakai, N., Gerard, D. and Matile, S. (2000) Synthesis of multiply substituted, ion channel forming octi(p-phenylene)s Theme and variations. Organic Letters,... 

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Wilkinson, S.G. Bacterial lipopolysaccharides—themes and variations. Prog Lipid Res 35 (1996) 283-343. 

J. Mulzer, Cram s Rule Theme and Variations, in Organic Synthesis Highlights (J. Mulzer, H.-J. Altenbach, M. Braun, K. Krohn, H.-U. ReiBig, Eds.), VCH, Weinheim, New York, 1991, 3-8. 

Hubbard, S. R. (2001). Theme and variations Juxtamembrane regulation of receptor protein kinases. Mol. Cell 8, 481-487. 

Cipolline R., Ascenzi, P. and Visca, P. (2007) Critical review common themes and variations in the rhodanese superfamily, lUBMB Life, 59(2), 51-9. 

Theme and variation. Propose a reaction mechanism for the condensation of acetyl CoA and glyoxylate in the glyoxylate cycle of plants and bacteria. 

Soto, G E, Hultgren, S J, Bacterial adhesins common themes and variations in architecture and assembly, J. Bacterial., 181, 1059-1071, 1999. 

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