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|Title: ||Design and synthesis of artificial porphyrin nanopores|
|Authors: ||Boccalon, Mariangela|
|Supervisor/Tutor: ||Tecilla, Paolo|
|Co-supervisor: ||Iengo, Elisabetta|
|Issue Date: ||17-Apr-2012|
|Publisher: ||Università degli studi di Trieste|
|Abstract: ||The regulation of transmembrane ion transport is a fundamental aspect of bioinspired chemistry which may find relevant applications in different fields ranging from pharmaceutics to sensing. In this contest the ability to form stable and well organized structures able to produce large and well defined pore in the membrane appears really promising. Several examples of such systems are present in the literature, usually formed in self-assembling processes mediated by hydrogen bonding, charge repulsion, and ion pairing. Coordination chemistry, however, has appeared only occasionally in design strategies for synthetic ion channels and pores. Recently Kobuke reported synthetic nanopores based on covalent adduct of porphyrins having six carboxylic acid groups directed up and down; the formation of hydrogen bonds between two monomers promotes their stacking and the formation of a nanopore able to span the lipid bilayer. The covalent approach for this type of macromolecules is synthetically laborious and the developments are therefore limited. In this context, the self-assembly approach, in which the macromolecules are generated by self-assembly of small and more synthetically accessible building blocks, is an attractive way to achieve the aim. In this field trans-porphyrin provides a linear substitution pattern that can be used for the construction of porphyrin-based architectures with a well-defined structure by metal mediated self-assembly.
We have started a research project aimed to design synthetic metal-organic nanopores derived from the self-assembling of porphyrin ligands with proper metal fragments. In our first approach we have used trans-dipyridylporphyrins (linear difunctional ligands) which, upon binding with metal fragments such as Re(I) or Pd(II) (cis-coordinant metal fragments) may form supramolecular boxes (4+4 type). Subsequently, the porphyrins have been functionalized with groups able to give hydrogen bonds after appropriate modification, such as esters.
A second part of the work was focused on the study of the ionophoric activity of the prepared compounds. Activity studies have been conducted on porphyrins and molecular squares using liposomes as models of biological membranes. Porphyrins and molecular squares without groups able to give hydrogen bonding do not show ionophoric activity. This behavior was expected because the dimension of these systems does not allow to span completely the lipid bilayer and there are not weak interactions that promote the self-assembly of the monomers. On the contrary, excellent ionophoric activity was observed with the molecular square bearing carboxylic acid. Thus, presence of hydrogen bonding groups that enable the formation of tubular, probably dimeric, structure are essential for forming the transmembrane nanopore. Ionophoric activity can be inhibited by using polyamino-dendrimers and this ability is function of their dimension.
Parallel to the development of supramolecular porphyrins based nanopores, in the course of my PhD period, I studied also the ionophoric activity of cyclic phosphate-linked oligosaccharide analogues (CyPLOS) and guanosine-based amphiphiles in collaboration with prof.ssa Daniela Montesarchio, Department of Organic Chemistry and Biochemistry, University “Federico II” of Napoli.|
|PhD cycle: ||XXIV Ciclo|
|PhD programme: ||SCUOLA DI DOTTORATO DI RICERCA IN SCIENZE E TECNOLOGIE CHIMICHE E FARMACEUTICHE|
|Main language of document: ||en|
|Type: ||Tesi di dottorato|
|Scientific-educational field: ||CHIM/06 CHIMICA ORGANICA|
|Appears in Collections:||Scienze chimiche|
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