Threshold Effects in Field-Induced Conformation Changes and Binding of Ions — Including Peptides — To Polynucleotides
In the past electric fields have been used for the characterisation of macromolecular systems mainly by the analysis of orientation effects. In recent years it has been demonstrated that electric fields can also be very useful for the characterisation of various types of binding reactions and conformation changes in macromolecules. The most important progress for this extended application of electric fields is the development of a reliable technique for the selective indication of reactions in systems with optical anisotropy due to orientation1–5. This technique is based upon the so-called “magic angle”: absorbance changes detected by plane polarised light oriented at an angle of 54.74° with respect to the electric field vector are not due to physical orientation but only due to “chemical” changes like binding reactions or conformation transitions. By this technique it is possible to characterise the binding reactions and conformation changes of polymers with a large optical anisotropy. Most of the systems of biological interest have such polymers as components. All the systems discussed in the present contribution are characterised by using the magic angle technique.
KeywordsField Strength Electric Field Pulse Absorbance Change Conformation Change Sphere Complex
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