Regulation of polymerase using cofactor oxidation states
Polynucleotide synthesis performed with a template independent polymerase such as terminal deoxynucleotidyl transferase (TdT) is regulated by controlling the oxidation state of a metal cofactor. The oxidation state of the metal cofactor is changed to +2, thus activating the polymerase, by applying a voltage with electrodes or by introducing a chemical redox reagent. Addressable polynucleotide synthesis creates polynucleotides with different arbitrary sequences through use of spatial control of cofactor oxidation states to add nucleotides only at selected locations on an array. Control of metal oxidation states is regulated by selective activation of a microelectrode array, controlled addition of redox reagents to specific locations on the array, or controlled activation of photocatalysts at specific locations on the array. Scavengers in solution prevent cofactors distant from the selected locations from catalyzing polymerase activity and thereby maintain the localized effect of polymerase activation.
1. An oligonucleotide synthesizer configured for polynucleotide synthesis using a template independent polymerase comprising:
an array covered with a plurality of initiators attached thereto each having a 3′ terminal nucleotide;
a solid metal source;
a metal cofactor oxidation state control mechanism that addressably oxidizes the solid metal source at a selected location on the array to release a metal cofactor in a +2 oxidation state;
control circuitry communicatively coupled to the metal cofactor oxidation state control mechanism and configured to selectively activate the metal cofactor oxidation state control mechanism at the selected location on the array; and
a reaction reagent solution in contact with the array and comprising the template independent polymerase and a selected nucleotide, wherein the reaction reagent solution further comprises a scavenger that is a redox reagent which oxidizes or reduces the metal cofactor to an oxidation state other than the +2 oxidation state or a chelator.
2. The oligonucleotide synthesizer of claim 1 , wherein the plurality of initiators may be the same or different from each other and individual ones of the plurality of initiators are polynucleotide sequences of 3-30 nucleotides.
3. The oligonucleotide synthesizer of claim 1 , wherein the solid metal source is a metallic deposit.
4. The oligonucleotide synthesizer of claim 1 , wherein the solid metal source is metallic cobalt or metallic magnesium.
5. The oligonucleotide synthesizer of claim 1 , wherein the solid metal source is an external electrode of the array and the external electrode is an on-array electrode.
6. The oligonucleotide synthesizer of claim 5 , wherein reduction of the metal cofactor in the +2 oxidation state back to metallic form causes electroplating of the external electrode.
7. The oligonucleotide synthesizer of claim 1 , further comprising an off-array electrode that is a counter electrode physically separate from the array as part of a three or four electrode system.
8. An oligonucleotide synthesizer configured for polynucleotide synthesis using a template independent polymerase comprising:
an array covered with a plurality of initiators attached thereto each having a 3′ terminal nucleotide;
a solid metal source;
a metal cofactor oxidation state control mechanism that oxidizes the solid metal source on the array to release a metal cofactor in a +2 oxidation state;
control circuitry communicatively coupled to the metal cofactor oxidation state control mechanism and configured to selectively activate the metal cofactor oxidation state control mechanism on the array; and
a reaction reagent solution in contact with the array and comprising the template independent polymerase, a selected nucleotide, and a chelator.
9. The oligonucleotide synthesizer of claim 8 , wherein the plurality of initiators may be the same or different from each other and individual ones of the plurality of initiators are polynucleotide sequences of 3-30 nucleotides.
10. The oligonucleotide synthesizer of claim 8 , wherein the solid metal source is a metallic deposit.
11. The oligonucleotide synthesizer of claim 8 , wherein the solid metal source is metallic cobalt or metallic magnesium.
12. The oligonucleotide synthesizer of claim 8 , wherein the solid metal source is an external electrode of the array and the external electrode is an on-array electrode.
13. The oligonucleotide synthesizer claim 12 , wherein reduction of the metal cofactor in the +2 oxidation state back to metallic form causes electroplating of the external electrode.
14. An oligonucleotide synthesizer configured for polynucleotide synthesis using a template independent polymerase comprising:
a microelectrode array including spatially addressable electrodes, the microelectrode array covered with a plurality of initiators attached thereto each having a 3′ terminal nucleotide;
a solid metal source;
control circuitry communicatively coupled to the microelectrode array and configured to oxidize the solid metal source to release a metal cofactor in a +2 oxidation state; and
a reaction reagent solution in contact with the microelectrode array and comprising the template independent polymerase, a selected nucleotide, and a scavenger that is a redox reagent which oxidizes or reduces the metal cofactor to an oxidation state other than the +2 oxidation state or a chelator.
15. The oligonucleotide synthesizer of claim 14 , wherein the solid metal source is an external electrode of the microelectrode array.
16. The oligonucleotide synthesizer of claim 15 , wherein reduction of the metal cofactor in the +2 oxidation state back to metallic form causes electroplating of the external electrode.
17. The oligonucleotide synthesizer of claim 14 , wherein the solid metal source is a metallic deposit.
18. The oligonucleotide synthesizer of claim 14 , wherein the plurality of initiators may be the same or different from each other and individual ones of the plurality of initiators are polynucleotide sequences of 3-30 nucleotides.
19. The oligonucleotide synthesizer of claim 14 , wherein the solid metal source is metallic cobalt or metallic magnesium.
20. The oligonucleotide synthesizer of claim 14 , further comprising an off-array electrode that is a counter electrode physically separate from the array as part of a three or four electrode system.