Backbone structure overview

An overview of the synthesis and characterization of a unique class of polymers with a phosphorus-nitrogen backbone Is presented, with a focus on poly(dichloro-phosphazene) as a common Intermediate for a wide variety of poly(organophosphazenes). Melt and solution polymerization techniques are Illustrated, Including the role of catalysts. The elucidation of chain structure and molecular weight by various dilute solution techniques Is considered. Factors which determine the properties of polymers derived from poly(dichlorophos-phazene) are discussed, with an emphasis on the role that the organic substituent can play In determining the final properties. 

Abstract This review provides an overview of some of the more recent work directed to exploit radical-based chemistry for the modification of some of Natures most important biomolecules, such as amino acids, peptides, and carbohydrates. Radical reactions are particularly advantageous for carrying out a variety of structural modifications on biomolecules as the reaction conditions are typically compatible with a wide variety of functional groups and solvents. An array of effective synthetic transformations will he discussed including selective side chain and backbone modifications of amino acids and peptides, along with methods for the transformation of carbohydrate substituents, as well as fragmentation and cyclizations reactions for the preparation of either structurally modified carbohydrates or chiral building blocks. 

There is a natural hierarchy in proteins (see Figure 15.1) which allows the complex three-dimensional structure to be simplified and categorized as combinations of smaller motifs. At the atom level there are patterns of side-chain interactions at the backbone level we see formation of secondary structure (a helix, P sheet and yS turn) and loop families these combine to give supersecondary structures (e.g. P hairpins) and motifs (e.g. Greek key) and ultimately the whole tertiary and quaternary structure. In this chapter we present an overview of current patterns which are observed... 

Data were recorded at 297 K and various pressures, (a) Overview plot showing the backbone and side-chain amide cross-peaks at 3 MPa (30 bar, blue), 100 MPa (1000 bar, green), and 200 MPa (2000 bar, red), (b) and (c) Close up views of a selected region of the HSQC spectra recorded at 100MPa (1000 bar, b) and 200 MPa (2000 bar, c). The cross-peaks corresponding to the native structure are labelled by blue dots. (After ref 89.)... 

As organizers, however, we felt obliged to impose some structure on these interactions, so we had asked our invited lectures to give overviews of major areas, or presentations of their own work as case histories, or practical demonstrations of the critical stages of common laboratory techniques, or in some cases all three of the above These formed the essential backbone of the course (and of this book), but a still wider range of approaches was represented at the meeting because... 

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