Aptamer method
The invention relates to a new method of determining in a sample the presence or absence of one or more analyte members of a group of two or more analytes. The invention therefore relates to a multiplex assay for determining the presence or absence of each analyte in a group of multiple analytes. The assay uses aptamers and transmembrane pores.
1. A multiplex assay method for determining the presence of at least one aptamer in a solution, the method comprising:
(a) contacting a transmembrane pore with a solution comprising a plurality of aptamers, each aptamer being folded into a three-dimensional structure, wherein each aptamer in the plurality is conjugated to a linear, single-stranded polynucleotide tail, wherein each linear, single-stranded polynucleotide tail that is conjugated to an aptamer in the plurality is different than each other linear, single-stranded polynucleotide tail that is conjugated to an aptamer in the plurality, and wherein each linear, single-stranded polynucleotide tail enters the pore and affects current flow through the pore;
(b) applying an electrical potential across the pore, wherein the linear, single-stranded polynucleotide tail of at least two aptamers each enters the pore, in succession, and each affects current flow through the pore, wherein movement of each linear, single-stranded polynucleotide tail through the pore produces a distinct current flow that is different than current flow through the pore produced by the other linear, single-stranded polynucleotide tails, and each aptamer unfolds under the influence of the potential and then moves through the pore after its linear, single-stranded polynucleotide tail;
(c) successively measuring current flowing through the pore as each linear, single-stranded polynucleotide tail of each aptamer of step (b) enters the pore; and
(d) determining the presence of each aptamer conjugated to each linear, single-stranded polynucleotide tail based on the distinct current flow through the pore caused by the linear, single-stranded polynucleotide tail of step (b).
2. A method according to claim 1 , wherein at least one tail comprises residues 1 to 30 of any one of SEQ ID Nos: 7 to 23.
3. A method according to claim 1 , wherein each tail is a linear, single-stranded polynucleotide from 7 to 70 nucleotides in length.
4. A method according to claim 1 , wherein each aptamer is a peptide aptamer or an oligonucleotide aptamer.
5. A method according to claim 1 , wherein the transmembrane pore comprises a vestibule and a barrel, optionally wherein:
(a) the barrel is sufficiently narrow that a double-stranded polynucleotide cannot pass through the transmembrane pore; or
(b) the vestibule and barrel are each long enough to contain at least two nucleotides; or
(c) the pore is a transmembrane protein pore or a solid state pore.
6. A method according to claim 5 , wherein the transmembrane protein pore is α-hemolysin, leukocidin, Mycobacterium smegmatis porin A (MspA), outer membrane phospholipase A, Neisseria autotransporter lipoprotein (NalP) and is optionally
(a) formed of seven identical subunits, wherein each subunit comprises the sequence shown in SEQ ID NO: 2; or
(b) a variant thereof in which one or more of the seven subunits has at least 50% homology to SEQ ID NO: 2 based on amino acid identify over the entire sequence and which retains pore activity; or
(c) α-hemolysin formed of four identical subunits as shown in SEQ ID NO: 4 and four identical subunits as shown in SEQ ID NO: 6; or
(d) a variant thereof in which one or more of the subunits has at least 50% homology to SEQ ID NO: 4 based on amino acid identity over the entire sequence and/or one or more of the subunits has at least 50% homology to SEQ ID NO: 6 based on amino acid identity over the entire sequence and the pore retains pore activity.