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Synthesis of Ester Analogs of Polyphosphates
thesisposted on 06.08.2019 by Chensong Jiao
In order to distinguish essays and pre-prints from academic theses, we have a separate category. These are often much longer text based documents than a paper.
This two-partite thesis explores a concept of substitution of a chemically and biologically unstable pyrophosphate residue with a more chemically stable, and enzyme-resistant analog that features an oxymethylenephosphonophosphate moiety. In the first part, I describe the synthesis of hydrolysis resistant biotinylated analogs of inositol polyphosphates as tools applicable to isolation and identification of proteins that bind inositol polyphosphates. Biotinylated analogs of IP6 and 5-IP7 are synthesized with the biotin linker phosphorylated to 2-OH of myo-inositol ring through aminohexyl linker. In contrast, the biotinylated analog of 1,5-IP8 has the biotin linker phosphorylated to 3-OH of myo-inositol ring. To increase their chemical and biological stability, pyrophosphate residues in IP7 and IP8 have oxymethylenephosphonophosphate installed in place of the natural pyrophosphate groups. Streptavidin affinity chromatography and non-homologous end-joining (NHEJ) DNA repair activity assay showed that IP6-biotin can replace the natural IP6 by binding to Ku protein of the NHEJ complex with only 2-fold reduction in potency. This project is significant in that: (i) this is the first report of the synthesis of biotinylated IP7 and IP8; and (ii) unlike the described non-hydrolysable IP7 immobilized on affinity gel, the identities and purities of these molecules are confirmed by spectroscopic methods. In the second part, synthesis of analogs of inorganic polyphosphates (polyP) is described, bearing a similar replacement of the pyrophosphate residue by oxymethylenephosphinophosphate moiety. Synthesis of a series of four different phosphitylating agents as building blocks for the generation of hydrolysis resistant inorganic polyphosphates analogs via solid phase synthesis using DNA synthesizer is described. Such synthetic design enables synthesis of long chain polyP analogs with exact length. Featuring oxymethylene phosphinate ester linkage, these polyP analogs are expected to be resistant to hydrolysis catalyzed by endo- and exo-polyphosphatases. These monomers enable us to generate a variety of polyP analogs that differ in their length, charge density and, with some monomers, the nature of side chains. We expect, these polyP analogs will serve as molecular probes for identification of proteins that bind natural polyP, and for studying the role of polyP in cell physiology.