Single Biological Macromolecules

FIGURE 1.7 (a) Schematic diagram for the SECM setup with controlled humidity, where the electrochemical processes control the current. Constant-current image of (b) fragments of DNA specimen and (c) IgG molecules in humid air. The mica substrate was treated with a buffer solution. (Reprinted with permission from Fan, F.-R. F. and A. J. Bard, Proc. Natl. Acad. Sci. USA, Vol. 96, 1999 pp. 14222-14227.) 

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An experimental teclmique that is usefiil for structure studies of biological macromolecules and other crystals with large unit cells uses neither the broad, white , spectrum characteristic of Lane methods nor a sharp, monocliromatic spectrum, but rather a spectral band with AX/X 20%. Because of its relation to the Lane method, this teclmique is called quasi-Laue. It was believed for many years diat the Lane method was not usefiil for structure studies because reflections of different orders would be superposed on the same point of a film or an image plate. It was realized recently, however, that, if there is a definite minimum wavelengdi in the spectral band, more than 80% of all reflections would contain only a single order. Quasi-Laue methods are now used with both neutrons and x-rays, particularly x-rays from synclirotron sources, which give an intense, white spectrum. 

Fig. 1. Structure adapted hierarchical description of Coulomb interactions in biological macromolecules. Filled circles (level 0) represent atoms, structural units (li vel 1) are surrounded by a single-line border, and clusters (level 2) are surrounded by a double-line border.

The lysosome is an acidic organelle containing many hydrolases and can degrade most biological macromolecules (Kornfeld and Mellman, 1989). The vacuole in yeast and plants is thought to be its functional relative. Both of them are bounded by a single membrane and have... 

Then we address the dynamics of diblock copolymer melts. There we discuss the single chain dynamics, the collective dynamics as well as the dynamics of the interfaces in microphase separated systems. The next degree of complication is reached when we discuss the dynamic of gels (Chap. 6.3) and that of polymer aggregates like micelles or polymers with complex architecture such as stars and dendrimers. Chapter 6.5 addresses the first measurements on a rubbery electrolyte. Some new results on polymer solutions are discussed in Chap. 6.6 with particular emphasis on theta solvents and hydrodynamic screening. Chapter 6.7 finally addresses experiments that have been performed on biological macromolecules. 

Recently, in many demanding sample preparation situations, more selective sorbents have been used. Affinity type sorbents, particularly immunosorbents, have gained popularity in trace analysis, not only for biological macromolecules but also for small molecules, like aflatoxins. MIPs have properties resembling those of affinity phases and therefore they may find unique applications where other sample pretreatment methods are tedious. This relates both to the separation of a single analyte and to the separation of a group of related analytes from the sample matrix. 

The study of photoinduced ET in covalently linked donor-acceptor assemblies began with comparatively simple dyad systems which contain a transition metal center covalently linked to a single electron donor or acceptor unit [26]. However, work in this area has naturally progressed and in recent years complex supramolecular assemblies comprised of one or more metal complexes that are covalently linked to one or more organic electron donors or acceptors have been synthesized and studied [27-36]. Furthermore, several groups have utilized the useful photoredox properties of transition metal complexes to probe electron and energy transfer across spacers comprised of biological macromolecules such as peptides [37,38], proteins [39,40], and polynucleic acids [41]. 

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