Patent Publication Number: US-11396675-B2

Title: Method to amplify transverse tunneling current discrimination of DNA nucleotides via nucleotide site specific attachment of dye-peptide

Description:
RELATED APPLICATIONS 
     This application claims the benefit of the filing date of U.S. Non-Provisional application Ser. No. 15/886,736 filed on Feb. 1, 2018 and entitled METHOD TO AMPLIFY TRANSVERSE TUNNELING CURRENT DISCRIMINATION OF DNA NUCLEOTIDES VIA NUCLEOTIDE SITE SPECIFIC ATTACHMENT OF DYE-PEPTIDE and U.S. Provisional Application No. 62/469,393, filed on 9 Mar. 2017, and entitled METHOD TO AMPLIFY TRANSVERSE TUNNELING CURRENT DISCRIMINATION OF DNA NUCLEOTIDES VIA NUCLEOTIDE SITE SPECIFIC ATTACHMENT OF DYE-PEPTIDE, the disclosure of all of which are incorporated in its entirety by this reference. 
    
    
     SUMMARY 
     One aspect of the present disclosure relates to a method of identifying nucleotides of a DNA strand. The method includes exposing the DNA strand to a first dye or peptide, attaching the first dye or peptide to a first type of nucleotide (A,T,C,G) of the DNA strand, the first dye or peptide changing a conductance of the first type of nucleotide to which the first dye or peptide is attached, and measuring a tunneling current signal for all nucleotides of the DNA strand, the changed conductance of the first type of nucleotide providing amplified tunneling current discrimination of the nucleotides of the DNA strand. 
     The first type of nucleotide may be an A (Adenine) nucleotide or a C (Cytosine) nucleotide. The method may further include exposing the DNA strand to a second dye or peptide, and attaching the second dye or peptide to a second type of nucleotide (A,T,C,G) of the DNA strand, the second dye or peptide changing a conductance of the second type of nucleotide to which the second dye or peptide is attached. The changed conductance of the second type of nucleotide may provide amplified tunneling current discrimination of the nucleotides of the DNA strand when measuring the tunneling current signal for all nucleotides of the DNA strand. The change in conductance may be a reduction in conductance. The reduction in conductance may result in an increased tunneling current signal for the first type of nucleotide. The reduction in conductance may be to a conductance level that is less than a conductance for all other types of nucleotides of the DNA strand. 
     Another aspect of the present disclosure relates to a method of DNA sequencing. The method includes providing a plurality of channels, each channel comprising at least one tunneling electrode, exposing a first DNA strand to a first dye or peptide, and attaching the first dye or peptide to a first type of nucleotide (A,T,C,G) of the first DNA strand, the attached first dye or peptide changing a conductance of the first type of nucleotide, exposing a second DNA strand to a second dye or peptide, and attaching the second dye or peptide to a second type of nucleotide (A,T,C,G) of the second DNA strand, the attached second dye or peptide changing a conductance of the second type of nucleotide, and exposing a third DNA strand to a third dye or peptide, and attaching the third dye or peptide to a third type of nucleotide (A,T,C,G) of the third DNA strand, the attached third dye or peptide changing a conductance of the third type of nucleotide. The method also includes passing the first, second and third DNA strands through separate ones of the plurality of DNA sequencing channels, measuring a tunneling current for the nucleotides with attached dyes or peptides in each of the channels, the measured tunneling currents being used to identify a location of the nucleotides with attached dyes or peptides on each DNA strand, and determining a sequence for the nucleotides of the DNA strands using the identified locations for the nucleotides with attached dyes or peptides. 
     The plurality of channels may include four channels, and the method further includes exposing a fourth DNA strand to a fourth dye or peptide, and attaching the fourth dye or peptide to a fourth type of nucleotide (A,T,C,G) of the fourth DNA strand, the attached fourth dye or peptide changing a conductance of the fourth type of nucleotide, and passing the fourth DNA strand through one of the plurality of DNA sequencing channels. The plurality of DNA sequencing channels may include three DNA sequencing channels, and the plurality of DNA strands may include three DNA strands. The locations for the first, second and third types of nucleotides may be used to construct a partial DNA sequence, and locations for a fourth nucleotide may be determined by process of elimination. Changing the conductance of the first, second and third types of nucleotides may include reducing the conductance. The reduction in conductance may result in an increased tunneling current signal. The DNA strands may each have identical DNA sequencing. 
     Another aspect of the present disclosure relates to a DNA sequencing method that includes amplifying tunneling current discrimination of nucleotides of a DNA strand using attachment of dyes or peptides to at least one specific type of nucleotide (A,T,C,G) of the DNA strand. The dyes or peptides may change a conductance value for the nucleotide to which the dyes or peptides are attached, and the changed conductance may result in a changed tunneling current value for the nucleotides to which the dyes or peptides are attached. The type of nucleotide may be one of an A (Adenine) nucleotide or a C (Cytosine) nucleotide. The method may include determining at least a portion of a DNA sequence using the amplified transverse tunneling current discrimination. The method may include exposing the DNA strand to a first dye or peptide, attaching the first dye or peptide to a first type of nucleotide (A,T,C,G) of the DNA strand, the first dye or peptide changing the conductance of the first type of nucleotide to which the first dye or peptide is attached, and measuring a tunneling current signal for all nucleotides of the DNA strand, the changed conductance of the first type of nucleotide providing amplified tunneling current discrimination of the nucleotides of the DNA strand. 
     The method may include exposing the DNA strand to a second dye or peptide, and attaching the second dye or peptide to a second type of nucleotide (A,T,C,G) of the DNA strand, the second dye or peptide changing the conductance of the second type of nucleotide to which the second dye or peptide is attached. The change in conductance may be a reduction in conductance, the reduction in conductance providing an increased tunneling current signal for the first type of nucleotide. 
     The foregoing has outlined rather broadly the features and technical advantages of examples according to this disclosure so that the following detailed description may be better understood. Additional features and advantages will be described below. The conception and specific examples disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. Such equivalent constructions do not depart from the scope of the appended claims. Characteristics of the concepts disclosed herein, including their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purpose of illustration and description only, and not as a definition of the limits of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A further understanding of the nature and advantages of the present disclosure may be realized by reference to the following drawings. In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following a first reference label with a dash and a second label that may distinguish among the similar components. However, features discussed for various components—including those having a dash and a second reference label—apply to other similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label. 
         FIG. 1A  schematically illustrates a DNA sequencing device in accordance with the present disclosure. 
         FIG. 1B  is a graph showing conductance for nucleotides of a DNA strand passing through the DNA sequencing device shown in  FIG. 1A . 
         FIG. 2A  schematically illustrates the DNA sequencing device of  FIG. 1A  with a dye/peptide reservoir and dye/peptide attached to specific nucleotides of a DNA strand. 
         FIG. 2B  is a graph showing measured tunneling current for the nucleotides of the DNA strand passing through the DNA sequencing device shown in  FIG. 2A . 
         FIG. 3A  is a graph showing example conductance values for nucleotides of a DNA strand. 
         FIG. 3B  shows shifting of a conductance value for one of the nucleotides shown in  FIG. 3A  as a result of attachment to a dye/peptide. 
         FIG. 4A  schematically illustrates a three (3) channel DNA sequencing device in accordance with the present disclosure, each channel being associated with a different dye/peptide, and a partial sequence for each channel. 
         FIG. 4B  illustrates a reconstruction of a DNA sequence based on the partial sequences from the channels of  FIG. 4A . 
         FIG. 5A  schematically illustrates a four (4) channel DNA sequencing device in accordance with the present disclosure, each channel being associated with a different dye/peptide. 
         FIG. 5B  illustrates a reconstruction of a DNA sequence based on the partial sequences from the channels of  FIG. 5A . 
         FIG. 6  is a flow diagram related to an example method in accordance with the present disclosure. 
         FIG. 7  is a flow diagram related to an example method in accordance with the present disclosure. 
         FIG. 8  is a flow diagram related to an example method in accordance with the present disclosure. 
         FIG. 9  shows a diagram of a system in accordance with various aspects of this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Despite considerable efforts, DNA sequencing today still suffers from high costs and low speeds. To address all these issues, various methods have been proposed over the past decade that would allow individual DNA strands to be read directly. Among these, nanopore and nanochannel based approaches have emerged as the most promising. However, many challenges exist related to fabricating a channel and/or pore opening that is sufficiently small to limit passage to a single DNA strand, and there is no such report of a relatively mature method that address this unmet need. 
     Direct DNA sequencing has drawn attention due to its advantages on long read length, high throughput and low cost. Direct DNA sequencing methods using transverse tunneling current measurement have been studied extensively in literature. However, a manufacturably viable direct DNA sequencing device with required dimensions for the gap between the nanoelectrodes, nor methods for creating such a device, have not been discovered. Conventional MEMS and nanofabrication methods are inadequate for creating the required structure. 
     The present disclosure generally relates to DNA sequencing, and more particularly relates to DNA sequencing devices having nanochannels and nanoelectrodes, and related methods of fabricating such devices. The present disclosure may also relate to DNA sequencing using such devices. The device may include a nanofluidic channel through which DNA strands can be guided through a subnanometer electrode gap. Also disclosed here are DNA sequencing devices that are configured to read DNA using tunneling current and based on ionic current measurement through a subnanometer orifice, which is expected to be faster and more accurate than existing products and methods. 
     The general approach to DNA sequencing using tunneling electrodes involves electrically driving DNA and RNA strands through a nanopore or narrow channel via ionic flow or driven by a pressure gradient. As the strand pass a high resolution sensor (e.g., electrode) embedded inside the channel, the high spatial resolution sensor measures the unique properties of the individual bases (A,T,C,G). One type of sensor would consist of a conductive electrode that measures the unique tunneling currents (e.g., based on conductance of the nucleotides) associated with the nucleotide, thereby identifying and resolving the four unique nucleotide types. 
       FIG. 1  schematically illustrates an example DNA sequencing device  10  used to measure a transverse tunneling signal as a DNA strand  4  translates through a nanochannel  16  of the device  10 . The measured tunneling current signals for some of the nucleotides  6  of the DNA strand  4  may overlap (e.g., see the current signals for nucleotides A and C in the graph of  FIG. 1B ), thus making discrimination of the nucleotides  6  difficult since the tunneling current associated with each nucleotide is not entirely unique. The tunneling current may be represented as a conductance measurement (pS), which is an inverse of the tunneling current, as shown in the graph of  FIG. 1B .  FIG. 1B  shows that the peaks of the conductance measured for some of the nucleotides A,T,C,G may be positioned close enough to each other that it is difficult to distinguish between them. 
     Some types of dyes and peptides, which attach to the nucleotides  6  of a DNA strand  4 , may change the conductance of the particular nucleotides  6  to which the dye/peptide is attached. Exposing a single strand DNA  4  to a site specific dye or peptide may result in attachment of the dye/peptide to a specific nucleotides  6 , and the conductance of that nucleotide is changed. In some cases, the conductance of that nucleotides  6  is changed (e.g., reduced) dramatically, thus leading to a more easily identified difference in the tunneling current signal for that specific nucleotides  6 . 
     Referring again to  FIG. 1A , the DNA sequencing device  10  includes a substrate  12 , an upper layer  14 , a nanochannel  16 , first and second electrode members  18 ,  20 , and a controller or pre-amp  22  connected to the electrode members  18 ,  20 . The nanochannel  16  has a height H typically in the range of about 5 nm to about 50 nm, and more particularly in the range of about 3 nm to about 20 nm. A gap G between the first and second electrode members  18 ,  20  typically is in the range of about 0.3 nm to about 5 nm, more particularly about 0.3 nm to about 2 nm, and typically about 1 nm. In some embodiments, the gap G may be variable by moving one or more of the first and second electrodes  18 ,  20  relative to the other. 
     During use, a DNA strand  4  is drawn into the nanochannel by electrophoresis forces. The DNA strand  4  may have a negative charge (e.g., a backbone  8  and/or the nucleotides  6  may carry a negative charge), and a positive energy source  24  is positioned downstream of the first and second electrodes  18 ,  20 , such as outside of the nanochannel  16 , to draw the DNA strand  4  through the gap G where the tunneling current is measured using the electrode members  18 ,  20  and the controller/pre-amp  22 . The output from the pre-amp  22  may be plotted on a graph such as the graph shown in  FIG. 1B . A range of conductance values for each type of nucleotide  6  may be generally known. However, in some cases, the average conductance for at least some of the nucleotides (e.g., types A and C as shown in  FIG. 1B ) may be close enough together that it is difficult to distinguish between the tunneling current measurements for those two types of nucleotides. By attaching a dye or peptide to one of the nucleotide types (e.g., type A or C), the conductance of the nucleotide carrying the attached dye/peptide may be significantly different from the closest nucleotide type and may be spaced from all other nucleotide types, thereby making it easier to identify and distinguish the nucleotide carrying the dye/peptide from the other nucleotides. 
     Referring to  FIGS. 2A and 2B , the nanochannel  16  of the DNA sequencing device  10  is arranged in flow communication with a reservoir  26  that holds at least one DNA strand  4  and a plurality of dye/peptide molecules  28 . The dyes/peptides  28  attaches only to an “A” nucleotide on the DNA strand  4 . The tunneling current signal measured for each site A on the DNA strand typically will be measurably, and sometimes significantly, different from the tunneling current signals for the remaining nucleotides  6  (e.g., C,T,G). This may result in an enhanced tunneling current contrast between the modified nucleotides A as compared to the remaining nucleotides C,T,G. 
       FIG. 2B  is a graph showing tunneling current signals for the nucleotides  6  of the DNA strand  4  shown in  FIG. 2A . The graph of  FIG. 2B  shows the increase in tunneling current for the A nucleotide due to the modification (e.g., attachment of the dye/peptide  28 ) at the nucleotides A, which increases conductance (and reduces the tunneling current) for the A nucleotides. The location of nucleotide A on DNA strand can be easily detected as a result of the modification using the dye/peptide  28 . 
       FIG. 3A  is a graph showing a median conductance and how it influences a measured value of the tunneling current for each nucleotide type (A,T,C,G). The C and A nucleotides  6  have the smallest conductance separation S 1 , which results in the most difficult two nucleotides to distinguish from each other. The C and T nucleotides are separated a distance S 2 . The A and G nucleotides are separated a distance S 3 . The A and T nucleotides are separated a distance S 4 . In one embodiment, a nucleotide specific dye/peptide may be attached to either the C or A nucleotide to reduce the conductance of that nucleotide and increase the tunneling current for that nucleotide (e.g., site on the DNA strand), as discussed above. Using the dye/peptide in this way may provide a more distinctive separation of conductance levels between the four nucleotide types and may provide a greater increase in tunneling current separation signal-to-noise ratio (SNR). 
       FIG. 3B  illustrates the effective of site-specific dye/peptides being attached to only the A nucleotide. The conductance of the A nucleotide is reduced to a point that there is separation between the C and A nucleotides to include the distance S 1 , and also separation between the A nucleotide and all other nucleotides (T,C,G). In some embodiments, the use of a dye/peptide changes the conductance of a particular nucleotide to a level that is either above or below the conductance level of all of the remaining nucleotides. In some embodiments, the distance S 1  has substantially increased, and the distances S 2 -S 4  are substantially equal to each other. In the example of  FIGS. 3A and 3B , attaching the dye/peptide to the C nucleotide may effectively generate similar results as attaching the dye/peptide to the A nucleotide. 
     Other embodiments may provide for DNA sequencing devices having multiple channel configurations that provide increased accuracy of the DNA sequencing process. In one example, a DNA sequencing device  100  includes three (3) channels to read back the modified DNA strand and reconstruct the original DNA sequence.  FIG. 4A  illustrates a three-channel configuration in which each channel measures a single type of nucleotide location and gathers enough signals to reconstruct a four-letter sequence in the DNA strand. 
     The DNA sequencing device  100  includes substrates  12 A- 12 C, upper layers  114 A- 114 C, nanochannels  116 A- 116 C, and pairs of first and second electrodes  118 A- 118 C and  120 A- 120 C. A separate controller or pre-amp  122 A- 122 C is associated with each of the nanochannels  116 A- 116 C, respectively. An energy source  124 A- 124 C drives a DNA strand  4 A- 4 C through the nanochannels  116 A- 116 C, respectively. A separate reservoir  126 A- 126 C is associated with each of the nanochannels  116 A- 116 C, respectively. The reservoirs  126 A- 126 C retain separate dyes/peptides  128 A- 128 C, respectively, which attach to different nucleotide  6 A- 6 C, of respective DNA strands  4 A- 4 C. 
     As further shown in  FIG. 4A , the tunneling current is determined for the nucleotide type to which the dye/peptide is attached for each respective nanochannel  116 A- 116 C and provided as a partial sequence  130 A- 130 C in association with each of the channels CH 1 -CH 3 , respectively. The partial sequences  130 A- 130 C may be combined as a final reconstruction as shown in  FIG. 4B . The final reconstruction provides the combination of partial sequences  130 A- 130 C received at each of the channels CH 1 -CH 3 . By determining the sequence of three of the four nucleotide types of a given DNA strand, any remaining gaps in the DNA sequence are known to be filled by the nucleotide type that has not been targeted with a dye/peptide from the reservoirs  126 A- 126 C. In the case of the final reconstruction shown in  FIG. 4B , the gaps in the sequence are known to be filled by the nucleotide type G. 
     Multiple channel configurations may make it possible to increase the accuracy of the DNA sequencing process by using this basic approach. This approach may significantly increase the signal-to-noise ratio (SNR) of a single type of nucleotide in each channel. The entire DNA sequence may be reconstructed using the combined measure values for each channel output in a post-processing step. 
     A DNA sequencing device may contain more than three channels for a four-letter sequence in the DNA strand. A DNA sequencing device having more than three channels may add signal redundancy to further improve the reconstruction accuracy.  FIG. 5A  illustrates a four-channel DNA sequencing device  200  that provides such signal redundancy. The DNA sequencing device  200  includes substrates  212 A- 212 D, upper layers  214 A- 214 D, separate nanochannels  216 A- 216 D, first and second electrode pairs  218 A- 218 D and  220 A- 220 D, and a controller or pre-amp  222 A- 222 D associated with each pair of electrodes  218 ,  220 . An energy source  224 A- 224 D is used to draw a DNA strand through each of the respective nanochannels  216 A- 216 D using electrophoresis. A reservoir  226 A- 226 D is associated with each of the nanochannels  216 A- 216 D, respectively. The reservoirs  226 A- 226 D carry separate dyes/peptides  228 A- 228 D, which are intended to attach to separate nucleotides A,T,C,G for the DNA strands  4 A- 4 D, respectively. 
     In operation, the DNA sequencing device  200  determines a tunneling current for each of the nucleotides  6 A- 6 D to which the dyes/peptides  228 A- 228 D are attached to provide a plurality of partial sequences  230 A- 230 D via channels CH 1 -CH 4 , respectively. The partial sequences  230 A- 230 D may be combined as shown in  FIG. 5  to create a final reconstruction. The final reconstruction may be carried out in a post-processing restructuring step that may result in a more accurate sequencing output as compared to the outputs available via DNA sequencing devices  10  and  100  described herein, and other known types of DNA sequencing devices and methods. 
     In other embodiments, a single one of the reservoirs associated with a DNA sequencing device may retain more than one type of dye/peptide, wherein each separate dye/peptide may be configured to attach to a single type of nucleotide of the DNA strands. The nucleotides with the attached dye/peptide may have a specific tunneling current that is unique as compared to the tunneling currents of all other nucleotides. The use of multiple dyes/peptides may provide a way to customize the tunneling current associated with each nucleotide in such a way to provide improved discrimination between the tunneling currents for each type of nucleotide, and may result in a more accurate sequencing output as compared to using a single type of dye/peptide. 
     In at least some embodiments, a separate dye/peptide for attachment to each of the four nucleotide types A,T,C,G may be included in a single reservoir. In still further embodiments, some reservoirs may carry a single or multiple dyes/peptides, whereas other reservoirs may include one or more other types of dyes/peptides for a different nanochannel in a given DNA sequencing device. Later reconstruction of a plurality of partial sequences may result in a final reconstruction with improved accuracy and/or redundancy. 
     In one example, a DNA sequencing device includes two nanochannels with a separate reservoir carrying one or two different types of peptides in each reservoir. All of the dyes/peptides used in both reservoirs may attach to different nucleotide types A,T,C,G. Each nanochannel may be associated with electrodes that measure the tunneling electrode and determine a sequence of one or two nucleotides as part of a partial sequence. The partial sequences may be combined to create a final reconstruction of a completed DNA sequence. 
     Various dyes and peptides may be used for the DNA sequencing devices and methods disclosed herein. Some example dyes and peptides include, for example, a peptide nucleic acid (PNA). Other examples may exist. PNAs may have relatively strong affinity, stability, and specificity to bonding to single strand DNA as compared to natural DNA nucleotides. 
     Various methods and processes are possible in accordance with the principles of the present disclosure.  FIG. 6  illustrates method steps of an example method  300  for identifying nucleotides of a DNA strand. The method  300  includes, at block  305 , exposing a DNA strand to a first dye or peptide. Block  310  includes attaching the first dye or peptide to a first type of nucleotide (A,T,C,G) of a DNA strand, wherein the first dye or peptide changes a conductance of the first type of nucleotide to which it is attached. Block  315  includes measuring a tunneling current signal for all nucleotides of the DNA strand, wherein the change in conductance of the first type of nucleotide provides amplified tunneling current discrimination of a nucleotide of the DNA strand. 
     The method  300  may also include providing the first type of nucleotide as an A (Adenine) nucleotide or a C (Cytosine) nucleotide. Method  300  may further include exposing the DNA strand to a second dye or peptide, attaching the second dye or peptide to a second type of nucleotide of a DNA strand, the second dye or peptide changing the conductance of the second type of nucleotide, wherein the changed conductance of a second type of nucleotide provides amplified tunneling current discrimination of the nucleotides of the DNA strand when measuring the tunneling current signal for all nucleotides of the DNA strand. The change in conductance may be a reduction in conductance. The reduction in conductance may result in an increased tunneling current signal for the first type of nucleotide. A reduction in conductance may be to a conductance level that is less than a conductance for all other types of nucleotides of the DNA strand. 
       FIG. 7  is directed to a method  400  of DNA sequencing. The method  400  includes, at block  405 , providing a plurality of channels, wherein each channel comprises at least one tunneling electrodes. Block  410  includes exposing a first DNA strand through a first dye or peptide, and attaching the first dye or peptide to a first type of nucleotide (A,T,C,G) of the first DNA strand, the attached first dye or peptide changing a conductance of the first type of nucleotide. Block  415  includes exposing a second DNA strand to a second dye or peptide, and attaching the second dye or peptide to a second type of nucleotide (A,T,C,G) of the second DNA strand, the attached second dye or peptide changing a conductance of the second type of nucleotide. Block  420  includes exposing a third DNA strand through a third dye or peptide, and attaching the third dye or peptide to a third type of nucleotide (A,T,C,G) of the third DNA strand, the attached third dye or peptide changing a conductance of the third type of nucleotide. Block  425  includes passing the first, second, and third DNA strands through separate ones of the plurality of DNA sequencing channels. Block  430  includes measuring a tunneling current for the nucleotides with attached dyes or peptides in each of the channels, the measured tunneling currents being used to identify location of the nucleotides with attached dyes or peptides on each of the DNA strands. Block  435  includes determining a sequence for the nucleotides of the DNA strands using the identified locations for the nucleotides with attached dyes or peptides. 
     The method  400  may also include providing the plurality of channels with four channels, and exposing a fourth DNA strand to a fourth dye or peptide, attaching the fourth dye or peptide to a fourth type of nucleotide (A,T,C,G) of the fourth DNA strand, the attached fourth dye or peptide changing a conductance of the fourth type of nucleotide, and passing the fourth DNA strand through one of the plurality of DNA sequencing channels. The method  400  may provide that the plurality of DNA sequencing channels includes three DNA sequencing channels, and the plurality of DNA strands including three DNA strands. The determined locations of the first, second, and third types of nucleotides may be used to construct a partial DNA sequence, and locations for the fourth nucleotide are determined by process of elimination. Changing the conductance of the first, second, and third types of nucleotides may include reducing the conductance. The reduction in conductance may result in an increased tunneling current signal. The DNA strands may each have identical DNA sequencing. 
       FIG. 8  illustrates steps of a method  500  for DNA sequencing. Block  505  includes attaching a dye or peptide to at least one specific type of nucleotide (A,T,C,G) of a DNA strand. Block  510  includes amplifying tunneling current discrimination of the at least one specific type of nucleotide using the attached dye or peptide. Block  515  includes determining a sequence of nucleotides using the amplified tunneling current discrimination. 
     The method  500  may provide that the dyes or peptides change a conductance value of the nucleotide to which the dyes or peptides are attached, and the changed conductance results in a changed tunneling current value for the nucleotides to which the dyes or peptides are attached. Method  400  may also provide that the type of nucleotide is one of an A (Adenine) nucleotide or a C (Cytosine) nucleotide. The method  500  may include determining at least a portion of a DNA sequence using an amplified transverse tunneling current discrimination. The method  500  may include exposing the DNA strand to a first dye or peptide, attaching the first dye or peptide to a first type of nucleotide of the DNA strand, the first dye or peptide changing the conductance of the first type of nucleotide to which the first dye or peptide is attached, and measuring a tunneling current signal for all nucleotides of the DNA strand, the changed conductance of the first type of nucleotide providing amplified tunneling current discrimination of the nucleotides of the DNA strand. 
     The method  500  may include exposing the DNA strand to a second dye or peptide, attaching the second dye or peptide to a second type of nucleotide of the DNA strand, the second dye or peptide changing the conductance of the second type of nucleotide to which the second dye or peptide is attached. The change in conductance may be a reduction in conductance, and the reduction in conductance provides an increased tunneling current signal for the first or second type of nucleotide. 
       FIG. 9  shows a system  600  for use with the DNA sequencing devices and systems shown in  FIGS. 1-5 . System  600  may include a control panel  665 . Control panel  665  may be equivalent at least in part to a controller, control unit, processor or the like for use with the devices described above with reference to  FIGS. 1-5 . Control panel  665  may include sequencing module  645 . The sequencing module  645  may provide communications with one or more electrodes  660  (also referred to as sensors or devices) directly or via other communication components, such as a transceiver  630  and/or antenna  635 . The electrodes  660  may represent one or more of the electrodes  126 ,  206 , or pairs of such electrodes in any of the embodiments described above. The sequencing module  645  may perform or control various operations associated with, for example, the electrodes  126 ,  206 , actuator  208 , controller, or other components of the DNA sequencing devices and related systems as described above with reference to  FIGS. 1-7 . 
     Control panel  665  may also include a processor module  605 , and memory  610  (including software/firmware code (SW)  615 ), an input/output controller module  620 , a user interface module  625 , a transceiver module  630 , and one or more antennas  635  each of which may communicate, directly or indirectly, with one another (e.g., via one or more buses  640 ). The transceiver module  630  may communicate bi-directionally, via the one or more antennas  635 , wired links, and/or wireless links, with one or more networks or remote devices. For example, the transceiver module  630  may communicate bi-directionally with one or more of device  650  and/or electrodes  660 - a ,  660 - c . The device  650  may be components of the DNA sequencing devices and related systems and devices described with reference to  FIGS. 1-7 , or other devices in communication with such systems and devices. The transceiver  630  may include a modem to modulate the packets and provide the modulated packets to the one or more antennas  635  for transmission, and to demodulate packets received from the one or more antennas  635 . In some embodiments (not shown) the transceiver may be communicate bi-directionally with one or more of device  650 , remote control device  655 , and/or electrodes  660 - a ,  660 - c  through a hardwired connection without necessarily using antenna  635 . While a control panel or a control device (e.g.,  605 ) may include a single antenna  635 , the control panel or the control device may also have multiple antennas  635  capable of concurrently transmitting or receiving multiple wired and/or wireless transmissions. In some embodiments, one element of control panel  665  (e.g., one or more antennas  635 , transceiver module  630 , etc.) may provide a connection using wireless techniques, including digital cellular telephone connection, Cellular Digital Packet Data (CDPD) connection, digital satellite data connection, and/or another connection. 
     The signals associated with system  600  may include wireless communication signals such as radio frequency, electromagnetics, local area network (LAN), wide area network (WAN), virtual private network (VPN), wireless network (using 302.11, for example), 345 MHz, Z-WAVE®, cellular network (using 3G and/or LTE, for example), and/or other signals. The one or more antennas  635  and/or transceiver module  630  may include or be related to, but are not limited to, WWAN (GSM, CDMA, and WCDMA), WLAN (including BLUETOOTH® and Wi-Fi), WMAN (WiMAX), antennas for mobile communications, antennas for Wireless Personal Area Network (WPAN) applications (including RFID and UWB). In some embodiments, each antenna  635  may receive signals or information specific and/or exclusive to itself. In other embodiments, each antenna  635  may receive signals or information not specific or exclusive to itself. 
     In some embodiments, one or more electrodes  660  (e.g., voltage, inductance, resistance, current, force, temperature, etc.) or devices  650  may connect to some element of system  600  via a network using one or more wired and/or wireless connections. In some embodiments, the user interface module  625  may include an audio device, such as an external speaker system, an external display device such as a display screen, and/or an input device (e.g., remote control device interfaced with the user interface module  625  directly and/or through I/O controller module  620 ). 
     One or more buses  640  may allow data communication between one or more elements of control panel  665  (e.g., processor module  605 , memory  610 , I/O controller module  620 , user interface module  625 , etc.). 
     The memory  610  may include random access memory (RAM), read only memory (ROM), flash RAM, and/or other types. The memory  610  may store computer-readable, computer-executable software/firmware code  615  including instructions that, when executed, cause the processor module  605  to perform various functions described in this disclosure (e.g., initiating an adjustment of a lighting system, etc.). Alternatively, the software/firmware code  615  may not be directly executable by the processor module  605  but may cause a computer (e.g., when compiled and executed) to perform functions described herein. Alternatively, the computer-readable, computer-executable software/firmware code  615  may not be directly executable by the processor module  605  but may be configured to cause a computer (e.g., when compiled and executed) to perform functions described herein. The processor module  605  may include an intelligent hardware device, e.g., a central processing unit (CPU), a microcontroller, an application-specific integrated circuit (ASIC), etc. 
     In some embodiments, the memory  610  can contain, among other things, the Basic Input-Output system (BIOS) which may control basic hardware and/or software operation such as the interaction with peripheral components or devices. For example, the sequencing module  645 , and other modules and operational components of the control panel  665  used to implement the present systems and methods may be stored within the system memory  610 . Applications resident with system  600  are generally stored on and accessed via a non-transitory computer readable medium, such as a hard disk drive or other storage medium. Additionally, applications can be in the form of electronic signals modulated in accordance with the application and data communication technology when accessed via a network interface (e.g., transceiver module  630 , one or more antennas  635 , etc.). 
     Many other devices and/or subsystems may be connected to one or may be included as one or more elements of system  600 . In some embodiments, all of the elements shown in  FIG. 8  need not be present to practice the present systems and methods. The devices and subsystems can be interconnected in different ways from that shown in  FIG. 8 . In some embodiments, an aspect of some operation of a system, such as that shown in  FIG. 8 , may be readily known in the art and are not discussed in detail in this application. Code to implement the present disclosure can be stored in a non-transitory computer-readable medium such as one or more of system memory  610  or other memory. The operating system provided on I/O controller module  620  may be iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. 
     The transceiver module  630  may include a modem configured to modulate the packets and provide the modulated packets to the antennas  635  for transmission and/or to demodulate packets received from the antennas  635 . While the control panel or control device (e.g.,  605 ) may include a single antenna  635 , the control panel or control device (e.g.,  605 ) may have multiple antennas  635  capable of concurrently transmitting and/or receiving multiple wireless transmissions. 
     In some embodiments, the DNA sequencing device and systems described herein may be used to collect electronic signals associated with the nucleotides of a DNA strand passing through the gap between electrode pairs, and the collected electronic signals are processed at a different location. The processing may include electronically comparing the collected electronic signals to ranges of electronic signals associated with specific nucleotide types which have been previously determined and stored. In other embodiments, the DNA sequencing device includes capability of processing the collected electronic signals, conducting such comparison evaluations, and even formulating an order or sequence for the nucleotides of the DNA strand being evaluated. 
     While the examples disclosed herein are related to a four-letter DNA sequence, the principles disclosed herein may be applicable to other types of DNA strands with other numbers of nucleotides and/or types of nucleotides. The use of dyes and/or peptides to attach at specific sites/nucleotides of a given DNA strand may generally provide enhanced discrimination and/or identification of that particular type of nucleotide on any DNA or RNA strand. 
     INCORPORATION BY REFERENCE 
     The entire content of each of the previously filed provisional patent applications listed below are incorporated by reference in their entireties into this document, as are the related non-provisional patent applications of the same title filed concurrently with the present application. If the same term is used in both this document and one or more of the incorporated documents, then it should be interpreted to have the broadest meaning imparted by any one or combination of these sources unless the term has been explicitly defined to have a different meaning in this document. If there is an inconsistency between any of the following documents and this document, then this document shall govern. The incorporated subject matter should not be used to limit or narrow the scope of the explicitly recited or depicted subject matter.
     U.S. Prov. App. No. 62/453,270, titled “SINGLE-MOLECULE DNA SEQUENCING METHOD USING CONFINED NANO-FLUIDIC CHANNEL AND SUB-NANOMETER ELECTRODE GAP,” filed on 1 Feb. 2017, and U.S. patent application Ser. No. 15/886,442, titled “SINGLE-MOLECULE DNA SEQUENCING METHOD USING CONFINED NANO-FLUIDIC CHANNEL AND SUB-NANOMETER ELECTRODE GAP,” filed on 1 Feb. 2018.   U.S. Prov. App. No. 62/453,398, titled “NANOFLUIDIC CHANNEL OPENING SIZE CONTROL USING ACTUATION,” filed on 1 Feb. 2017, and U.S. patent application Ser. No. 15/886,483, titled “NANOFLUIDIC CHANNEL OPENING SIZE CONTROL USING ACTUATION,” filed on 1 Feb. 2018.   U.S. Prov. App. No. 62/453,298, titled “FABRICATION OF NANOCHANNEL WITH INTEGRATED ELECTRODES FOR DNA SEQUENCING USING TUNNELING CURRENT,” filed on 1 Feb. 2017, and U.S. patent application Ser. No. 15/886,511, titled “FABRICATION OF NANOCHANNEL WITH INTEGRATED ELECTRODES FOR DNA SEQUENCING USING TUNNELING CURRENT,” filed on 1 Feb. 2018.   U.S. Prov. App. No. 62/453,307, titled “METHOD TO FABRICATE A NANOCHANNEL FOR DNA SEQUENCING BASED ON NARROW TRENCH PATTERNING PROCESS,” filed on 1 Feb. 2017, and U.S. patent application Ser. No. 15/886,533, titled “METHOD TO FABRICATE A NANOCHANNEL FOR DNA SEQUENCING BASED ON NARROW TRENCH PATTERNING PROCESS,” filed on 1 Feb. 2018.   U.S. Prov. App. No. 62/453,323, titled “FABRICATION OF A DEVICE FOR SINGLE-MOLECULE DNA SEQUENCING USING SIDEWALL LITHOGRAPHY,” filed on 1 Feb. 2017, and U.S. patent application Ser. No. 15/886,560, titled “FABRICATION OF A DEVICE FOR SINGLE-MOLECULE DNA SEQUENCING USING SIDEWALL LITHOGRAPHY,” filed on 1 Feb. 2018.   U.S. Prov. App. No. 62/453,339, titled “FABRICATION OF A NANOCHANNEL FOR DNA SEQUENCING USING ELECTRICAL PLATING TO ACHIEVE TUNNELING ELECTRODE GAP,” filed on 1 Feb. 2017, and U.S. patent application Ser. No. 15/886,581, titled “FABRICATION OF A NANOCHANNEL FOR DNA SEQUENCING USING ELECTRICAL PLATING TO ACHIEVE TUNNELING ELECTRODE GAP,” filed on 1 Feb. 2018.   U.S. Prov. App. No. 62/453,346, titled “NANOSTRUCTURES TO CONTROL DNA STRAND ORIENTATION AND POSITION LOCATION FOR TRANSVERSE DNA SEQUENCING,” filed on 1 Feb. 2017, and U.S. patent application Ser. No. 15/886,608, titled “NANOSTRUCTURES TO CONTROL DNA STRAND ORIENTATION AND POSITION LOCATION FOR TRANSVERSE DNA SEQUENCING,” filed on 1 Feb. 2018.   U.S. Prov. App. No. 62/453,365, titled “FABRICATION OF WEDGE SHAPED ELECTRODE FOR ENHANCED DNA SEQUENCING USING TUNNELING CURRENT,” filed on 1 Feb. 2017, and U.S. patent application Ser. No. 15/886,661, titled “FABRICATION OF WEDGE SHAPED ELECTRODE FOR ENHANCED DNA SEQUENCING USING TUNNELING CURRENT,” filed on 1 Feb. 2018.   U.S. Prov. App. No. 62/453,329, titled “DIRECT SEQUENCING DEVICE WITH A TOP-BOTTOM ELECTRODE PAIR,” filed on 1 Feb. 2017, and U.S. patent application Ser. No. 15/886,685, titled “DIRECT SEQUENCING DEVICE WITH A TOP-BOTTOM ELECTRODE PAIR,” filed on 1 Feb. 2018.   U.S. Prov. App. No. 62/453,376, titled “MICRO AND NANOFLUIDIC CHANNEL CONTROLLED ACTUATION TO OPEN CHANNEL GAP,” filed on 1 Feb. 2017.   U.S. Prov. App. No. 62/469,409, titled “VERTICAL NANOPORE COUPLED WITH A PAIR OF TRANSVERSE ELECTRODES HAVING A UNIFORM ULTRASMALL NANOGAP FOR DNA SEQUENCING,” filed on 9 Mar. 2017, and U.S. patent application Ser. No. 15/886,723, titled “VERTICAL NANOPORE COUPLED WITH A PAIR OF TRANSVERSE ELECTRODES HAVING A UNIFORM ULTRASMALL NANOGAP FOR DNA SEQUENCING,” filed on 9 Mar. 2018.   

     The detailed description set forth above in connection with the appended drawings describes examples and does not represent the only instances that may be implemented or that are within the scope of the claims. The terms “example” and “exemplary,” when used in this description, mean “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, known structures and apparatuses are shown in block diagram form in order to avoid obscuring the concepts of the described examples. 
     As used herein, including in the claims, the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed. For example, if a composition is described as containing components A, B, and/or C, the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination. Also, as used herein, including in the claims, “or” as used in a list of items (for example, a list of items prefaced by a phrase such as “at least one of” or “one or more of”) indicates a disjunctive list such that, for example, a list of “at least one of A, B, or C” means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). 
     In addition, any disclosure of components contained within other components or separate from other components should be considered exemplary because multiple other architectures may potentially be implemented to achieve the same functionality, including incorporating all, most, and/or some elements as part of one or more unitary structures and/or separate structures. 
     The previous description of the disclosure is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not to be limited to the examples and designs described herein but is to be accorded the broadest scope consistent with the principles and novel features disclosed. 
     The process parameters, actions, and steps described and/or illustrated in this disclosure are given by way of example only and can be varied as desired. For example, while the steps illustrated and/or described may be shown or discussed in a particular order, these steps do not necessarily need to be performed in the order illustrated or discussed. The various exemplary methods described and/or illustrated here may also omit one or more of the steps described or illustrated here or include additional steps in addition to those disclosed. 
     This description, for purposes of explanation, has been described with reference to specific embodiments. The illustrative discussions above, however, are not intended to be exhaustive or limit the present systems and methods to the precise forms discussed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to explain the principles of the present systems and methods and their practical applications, to enable others skilled in the art to utilize the present systems, apparatus, and methods and various embodiments with various modifications as may be suited to the particular use contemplated.