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Multinuclear NMR Study of the Interaction of DNA Liquid Crystalline Phases with Intercalators and Divalent Metal Ions

It is assessed that intercalators, such as antibiotics and dyes, and particular divalent metal ions are activators or inhibitors of important processes, such as the replication, the transcription and the translation of the genetic code. Therefore, it is of great interest to analyse in detail the structural variations induced on DNA liquid crystals by these agents and to reveal possible correlations between the DNA structure and its biological activity.
To get these objectives, methodologies of experimental investigation based on the use of the multinuclear NMR spectroscopy have been employed, allowing the acquisition of set of information on the structural and dynamic properties of DNA-exogenous agents systems. To this aim, DNA liquid crystalline samples, at different temperatures and concentrations, have been analysed by means of 31P, 23Na, 2H and 17O NMR Spectroscopy. In particular, various spectroscopies have contributed to monitor simultaneously DNA structure and physical state (31P NMR), interactions between DNA and sodium counterions (23Na NMR), and the degree of order of examined liquid crystals and of the water (2H and 17O NMR). Moreover, the employment of the Polarized Light Optical Microscopy has provided complementary information for the characterisation of the DNA liquid crystalline phases. In the present work the following exogenous agents have been analysed: the classical intercalator ethidium bromide (EB), divalent metal ions Mg2+, Mn2+, Ni2+ and Cd2+, and the intercalating platinum complex Chloro(2,2’:6’,2’’-Terpyridine)Platinum(II) Chloride [Pt(Terpy)Cl]Cl (PtTCC).

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9 General introduction The discovery of the DNA helical structure in 1953, thanks to the X rays study of Rosalind Franklin [1], led to the definition of the double helical model by Watson and Crick [2]. Since then the majority of the research on DNA has been addressed to the study of the biological activity of nucleic acids, which, once acquired the knowledge on genes sequence, has led to the post-genomic era. The availability of complete DNA sequences for different organisms has given impetus to the post-genomic studies, which have received the stimulating task of using dynamical and structural data of biomolecules codified by the genome for explaining more effectively their interactions and functions. In addition to the possibility of studying the function and the evolution of individual genes, there is also the opportunity of analyzing some important aspects of the genome organisation through the arranged employment of different techniques of structural analysis, as nuclear magnetic resonance (NMR), X rays crystallography, cryo-electron microscopy and the use of molecular modeling. Recently, thanks to the employment of the DNA in the materials science the interest for the life molecule has also increased remarkably for its potential technological applications, from biochips [3] to the nanorobotics [4]. In the area of studies on DNA structural and dynamical properties in isotropic aqueous solution, investigations addressed to the study of the interaction of DNA with exogenous agents, like intercalators [5], groove binders [6], divalent metal ions [90] and osmotic agents [7] were particularly interesting. After it was observed that

Tesi di Dottorato

Dipartimento: Scienze Chimiche

Autore: Andrea Catte Contatta »

Composta da 120 pagine.

 

Questa tesi ha raggiunto 354 click dal 09/02/2006.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.