Nanopore based molecular detection and sequencing
This disclosure provides systems and methods for molecular identification and polymer (e.g., nucleic acid) sequencing using nanopores. The polymer may be passed through or in proximity to the nanopore and various subunits of the polymer may affect the current flowing through the nanopore. The various subunits may be identified by measuring the current at a plurality of voltages applied across the nanopore and/or membrane. In some cases, the polymerization of tagged nucleotides presents tag molecules to the nanopore that can be identified by measuring the current at a plurality of voltages applied across the nanopore and/or membrane. Also provided herein are systems and methods for sequencing both the sense and anti-sense strand of a double stranded nucleic acid molecule with a nanopore and methods for using ribonucleic acid (RNA) speed bump molecules to slow the passage of a nucleic acid molecule through or in proximity to a nanopore.
1. A system for identifying a nucleotide or nucleotide analog or portion thereof, the system comprising:
a chip comprising at least one cell, the cell comprising an electrode pair and a nanopore disposed in a membrane, wherein the electrode pair is associated with a variable voltage source and configured to apply a variable voltage across the nanopore of the membrane;
a memory device comprising code instructions, and
a processor communicatively coupled to the memory device, wherein the processor is configured to execute the code instructions that are stored in the memory device to cause the system to:
vary the voltage applied across the nanopore when a nucleotide or nucleotide analog or portion thereof is inserted into the nanopore, wherein the voltage is varied across a range of voltages from 120 mV to 150 mV;
measure an electrical signal at a plurality of applied voltages with at least one of the electrode pair while the nucleotide or nucleotide analog or portion thereof is inserted within the nanopore; and
identify the nucleotide or nucleotide analog or portion thereof that is inserted within the nanopore based on the measured electrical signal at the plurality of applied voltages.
2. The system of claim 1 , wherein varying the voltage across the range from 120 mV to 150 mV distinguishes one nucleotide from a different nucleotide.
3. The system of claim 1 , wherein the electrical signal is current.
4. The system of claim 1 , wherein the electrical signal is conductance.
5. The system of claim 1 , wherein the nucleotide or nucleotide analog is a tag molecule.
6. The system of claim 1 , wherein the voltage is varied according to a voltage waveform.
7. The system of claim 6 , wherein the voltage waveform is a square wave, a sinusoidal wave, a triangular wave, a saw-tooth wave, or an irregular wave.
8. The system of claim 1 , wherein the voltage is ramped from a first voltage to a second voltage.
9. The system of claim 1 , wherein varying the voltage comprises applying a first voltage for a first time period and a second voltage for a second time period.
10. The system of claim 9 , wherein the first voltage and the second voltage have a difference of at least 1 mV.
11. The system of claim 9 , wherein the first voltage and the second voltage have a difference of at least 10 mV.
12. The system of claim 9 , wherein the first time period and the second time period is at least 5 μs.