ABSTRACT
Protein nanopores have been used as stochastic sensors for the detection of analytes that range from small molecules to proteins. In this approach, individual analyte molecules modulate the ionic current flowing through a single nanopore. Here, a new type of stochastic sensor based on an αHL pore modified with an aptamer is described. The aptamer is bound to the pore by hybridization to an oligonucleotide that is attached covalently through a disulfide bond to a single cysteine residue near a mouth of the pore. We show that the binding of thrombin to a 15-mer DNA aptamer, which forms a cation-stabilized quadruplex, alters the ionic current through the pore. The approach allows the quantification of nanomolar concentrations of thrombin, and provides association and dissociation rate constants and equilibrium dissociation constants for thrombin·aptamer interactions. Aptamer-based nanopores have the potential to be integrated into arrays for the parallel detection of multiple analytes.
Subject(s)
Aptamers, Nucleotide/chemistry , Biosensing Techniques , Nanopores , Nanotechnology/methods , Proteins/analysis , Models, Molecular , Stochastic Processes , Thrombin/chemistryABSTRACT
The synthesis of rhenium and 99m-technetium complexes of dipyrazolemethanecarboxylates directly from the tetroxometallates is reported together with a 'one pot' synthesis of mixed ligand M(V) complexes. The rhenium complexes in all three oxidation states show strong fluorescence when the pyrazole groups have aromatic substituents with emission around 330 nm with both one and two photon excitation. The emission lifetimes of the complexes and free ligands differ considerably.
Subject(s)
Coordination Complexes/chemistry , Fluorescent Dyes/chemistry , Photons , Rhenium/chemistry , Technetium/chemistry , Isotope Labeling , Ligands , Pyrazoles/chemistry , Radiopharmaceuticals/chemistryABSTRACT
Reaction of [ReOCl3(PPh3)(2)] with HCpz(3) (pz = pyrazole) in dichloromethane leads to the formation of a new Re(iv) complex [ReCl3(HCpz3)]X (X=Cl, [ReO4]) with loss of the rhenium-oxo group. We also report a convenient, high-yield synthetic route to complexes of the type [ReOXn(L)](3-n)+ (X=Cl, Br, n = 2, 3) by the reaction of bis(pyrazolylmethane) and bis(pyrazolylacetate) ligands with [ReOCl3(PPh3)2]. Dinuclear complexes containing the O=Re-O-Re=O group were also isolated and structurally characterised. We have also investigated the reactions of these ligands with diazenide precursors and isolated and characterised complexes of the type [ReClx(N2Ph) (L)(PPh3)] (x = 1,2). The potential applications of these complexes as radiopharmaeuticals is discussed.
