Key_JJ Advance_NN1 In_II DNA_NN1 Sequencing_NN1 With_IW Nanopores_NP1 High-quality_JJ detection_NN1 takes_VVZ the_AT label-free_JJ ,_, single-molecule_JJ technique_NN1 closer_RRR to_II reality_NN1 TAKING_VVG DNA_NN1 APART_RL one_MC1 nucleotide_NN1 at_II a_AT1 time_NNT1 ,_, directing_VVG the_AT nucleotides_NN2 sequentially_RR into_II a_AT1 nanopore_NN1 ,_, and_CC detecting_VVG them_PPHO2 with_IW an_AT1 electrical_JJ current_JJ meter_NN1 may_VM seem_VVI an_AT1 unlikely_JJ DNA-sequencing_JJ concept_NN1 ,_, but_CCB it_PPH1 is_VBZ closer_JJR than_CSN ever_RR to_II being_VBG a_AT1 reality_NN1 ._. 
Chemical_JJ biology_NN1 professor_NN1 Hagan_NP1 Bayley_NP1 of_IO the_AT University_NN1 of_IO Oxford_NP1 and_CC coworkers_NN2 there_RL and_CC at_II Oxford_NP1 Nanopore_NP1 Technologies_NN2 ,_, a_AT1 company_NN1 Bayley_NP1 founded_VVD ,_, have_VH0 just_RR demonstrated_VVN that_CST the_AT four_MC standard_JJ DNA_NN1 nucleotides_NN2 --_JJ adenine_NN1 ,_, thymine_VV0 ,_, guanine_NN1 ,_, and_CC cytosine_VV0 --_NN1 can_VM be_VBI distinguished_VVN from_II one_PPX121 another_PPX122 reliably_RR by_II the_AT amount_NN1 of_IO current_JJ they_PPHS2 each_DD1 block_NN1 as_CSA they_PPHS2 flow_VV0 through_II a_AT1 nanopore_NN1 ._. 
And_CC for_IF good_JJ measure_NN1 ,_, they_PPHS2 've_VH0 shown_VVN that_CST the_AT method_NN1 can_VM also_RR identify_VVI 5-methylcytosine_NN1 ,_, a_AT1 biologically_RR important_JJ modified_JJ nucleotide_NN1 ._. 
DNA_NN1 sequencing_NN1 with_IW a_AT1 nanopore_NN1 (_( Nat_NP1 ._. 
Biotechnol._NP1 2008_MC ,_, 26_MC ,_, 1146_MC )_) is_VBZ one_MC1 of_IO several_DA2 technologies_NN2 being_VBG investigated_VVN as_CSA potential_JJ routes_NN2 to_II the_AT $1,000_NNU genome_NN1 --_NN1 the_AT ability_NN1 to_II sequence_NN1 a_AT1 human_JJ genome_NN1 for_IF about_RG $1,000_NNU ._. 
Currently_RR ,_, human_JJ genome_NN1 sequencing_NN1 costs_VVZ anywhere_RL from_II $100,000_NNU to_II $1_NNU million_NNO ._. 
The_AT $1,000_NNU genome_NN1 could_VM ease_VVI the_AT way_NN1 to_II personalizing_VVG drug_NN1 or_CC medical_JJ treatments_NN2 according_II21 to_II22 a_AT1 patient_NN1 's_GE genomic_JJ makeup_NN1 ._. 
A_AT1 key_JJ advantage_NN1 of_IO nanopore_NN1 sequencing_NN1 is_VBZ that_CST it_PPH1 detects_VVZ nucleotides_NN2 directly_RR ,_, without_IW reagents_NN2 or_CC labeling_VVG ,_, from_II a_AT1 single_JJ molecule_NN1 of_IO single-stranded_JJ DNA_NN1 ._. 
All_DB current_JJ DNA-sequencing_JJ techniques_NN2 require_VV0 fluorescent_JJ or_CC luminescent_JJ labeling_NN1 ,_, and_CC most_DAT use_NN1 polymerase_NN1 chain_NN1 reaction_NN1 for_IF DNA_NN1 amplification_NN1 ._. 
Nanopore_VV0 technology_NN1 is_VBZ also_RR potentially_RR capable_JJ of_IO sequencing_NN1 much_RR longer_JJR continuous_JJ strands_NN2 of_IO DNA_NN1 than_CSN other_JJ techniques_NN2 ._. 
This_DD1 capability_NN1 is_VBZ becoming_VVG increasingly_RR important_JJ for_IF studies_NN2 of_IO long-range_JJ genomic_JJ complexity_NN1 to_TO associate_VVI DNA_NN1 rearrangements_NN2 with_IW cancer_NN1 and_CC other_JJ diseases_NN2 ._. 
Three_MC years_NNT2 ago_RA ,_, Bayley_NP1 and_CC coworkers_NN2 detected_VVD DNA_NN1 nucleotides_NN2 in_II nanopores_NN2 formed_VVN by_II embedding_NN1 molecules_NN2 of_IO bacterial_JJ &alpha;_NULL -hemolysin_JJ protein_NN1 in_II a_AT1 biological_JJ membrane_NN1 (_( J._NP1 Am_RA ._. 
Chem_VV0 ._. 
Soc._NP1 2006_MC ,_, 128_MC ,_, 1705_MC )_) ._. 
Inside_II each_DD1 hemolysin_NN1 they_PPHS2 lodged_VVD cyclodextrin_NN1 ,_, which_DDQ acts_VVZ as_II an_AT1 "_" adapter_NN1 "_" molecule_NN1 that_CST interacts_VVZ with_IW the_AT nucleotides_NN2 transiently_RR as_CSA they_PPHS2 pass_VV0 one_MC1 by_II one_MC1 through_II the_AT pore_NN1 ._. 
When_RRQ nucleotides_NN2 interact_VV0 with_IW cyclodextrin_NN1 ,_, they_PPHS2 interrupt_VV0 a_AT1 current_JJ running_NN1 through_II it_PPH1 ,_, and_CC the_AT four_MC nucleotides_NN2 can_VM be_VBI distinguished_VVN by_II the_AT different_JJ amounts_NN2 of_IO current_JJ they_PPHS2 block_VV0 ._. 
But_CCB in_II that_DD1 study_NN1 the_AT electrical_JJ current_JJ signals_NN2 from_II the_AT different_JJ nucleotides_NN2 overlapped_VVD ,_, making_VVG identification_NN1 only_RR about_RG 90%_NNU reliable_JJ ._. 
Exonuclease_VV0 ,_, which_DDQ is_VBZ needed_VVN to_TO cleave_VVI nucleotides_NN2 from_II single-stranded_JJ DNA_NN1 and_CC feed_VVI them_PPHO2 into_II the_AT nanopore_NN1 ,_, was_VBDZ not_XX present_JJ in_II the_AT nanopore_NN1 experiments_NN2 ._. 
And_CC cyclodextrin_NN1 was_VBDZ not_XX covalently_RR attached_VVN to_II the_AT nanopore_NN1 and_CC thus_RR floated_VVN around_RP a_RR21 bit_RR22 during_II the_AT experiments_NN2 ,_, causing_VVG periodic_JJ signal_NN1 interruptions_NN2 ._. 
IN_II THE_AT NEW_JJ WORK_NN1 the_AT researchers_NN2 used_JJ exonuclease_NN1 in_II solution_NN1 to_TO cleave_VVI the_AT DNA_NN1 ,_, glued_VVD the_AT cyclodextrin_NN1 to_II the_AT nanopore_NN1 ,_, and_CC thus_RR greatly_RR improved_VVD the_AT ability_NN1 to_TO distinguish_VVI the_AT four_MC nucleotides_NN2 (_( to_II an_AT1 average_NN1 99.8%_FO accuracy_NN1 )_) ._. 
As_CSA their_APPGE coup_NN131 de_NN132 grace_NN133 ,_, they_PPHS2 also_RR distinguished_JJ 5-methylcytosine_NN1 from_II the_AT unmethylated_JJ nucleotides_NN2 ._. 
5-Methylcytosine_NP1 is_VBZ important_JJ for_IF studies_NN2 of_IO genomic_JJ methylation_NN1 patterns_NN2 and_CC epigenetics_NN2 ,_, the_AT inheritance_NN1 of_IO traits_NN2 by_II means_NN other_II21 than_II22 DNA_NN1 sequence_NN1 changes_NN2 ._. 
To_TO be_VBI a_AT1 viable_JJ route_NN1 to_II the_AT $1,000_NNU genome_NN1 ,_, nanopore_VV0 sequencing_NN1 still_RR must_VM overcome_VVI a_AT1 number_NN1 of_IO hurdles_NN2 ._. 
For_REX21 example_REX22 ,_, the_AT researchers_NN2 will_VM need_VVI to_TO demonstrate_VVI that_CST they_PPHS2 can_VM attach_VVI the_AT exonuclease_NN1 directly_RR to_II each_DD1 nanopore_NN1 and_CC that_CST the_AT enzyme_NN1 can_VM feed_VVI single_JJ nucleotides_NN2 into_II the_AT pore_NN1 after_II chopping_VVG them_PPHO2 off_II the_AT DNA_NN1 strand_NN1 being_VBG sequenced_VVN ._. 
They_PPHS2 will_VM also_RR need_VVI to_TO show_VVI that_CST all_DB the_AT nucleotides_NN2 in_II a_AT1 sequence_NN1 can_VM be_VBI directed_VVN through_II the_AT nanopore_NN1 in_II order_NN1 without_IW any_DD going_VVG astray_JJ or_CC clumping_VVG together_RL in_II the_AT pore_NN1 ._. 
In_II the_AT current_JJ study_NN1 exonuclease_NN1 was_VBDZ floating_VVG around_RP freely_RR in_II solution_NN1 ,_, and_CC the_AT nucleotides_NN2 detected_VVD floated_VVN into_II the_AT nanopore_NN1 by_II chance_NN1 ,_, not_XX in_II order_NN1 by_II sequence_NN1 ._. 
Jeffery_NP1 A._NP1 Schloss_NP1 ,_, director_NN1 of_IO the_AT $1,000_NNU genome_NN1 grant_NN1 program_NN1 at_II the_AT National_JJ Human_JJ Genome_NN1 Research_NN1 Institute_NN1 at_II the_AT National_JJ Institutes_NN2 of_IO Health_NN1 ,_, says_VVZ Bayley_NP1 and_CC coworkers_NN2 "_" showed_VVD that_CST one_PN1 can_VM operate_VVI the_AT system_NN1 under_II conditions_NN2 where_RRQ an_AT1 exonuclease_NN1 can_VM function_VVI and_CC still_RR get_VVI the_AT released_JJ nucleotides_NN2 to_TO pass_VVI through_II the_AT pore_NN1 and_CC distinguish_VVI them_PPHO2 ._. 
It_PPH1 's_VBZ a_AT1 significant_JJ engineering_NN1 achievement_NN1 toward_II the_AT next_MD step_NN1 ,_, which_DDQ would_VM be_VBI to_TO attach_VVI an_AT1 exonuclease_NN1 to_II the_AT nanopore_NN1 and_CC then_RT feed_VV0 the_AT DNA_NN1 strand_NN1 through_II that_DD1 ._. 
The_AT quality_NN1 of_IO their_APPGE ability_NN1 to_TO distinguish_VVI between_II the_AT nucleotides_NN2 is_VBZ pretty_RG high_JJ for_IF single-nucleotide_NN1 reads_VVZ by_II any_DD DNA-sequencing_JJ method_NN1 ._. 
This_DD1 increases_VVZ the_AT confidence_NN1 that_CST the_AT team_NN1 will_VM eventually_RR be_VBI able_JK to_TO develop_VVI a_AT1 true_JJ sequencing_NN1 system_NN1 from_II this_DD1 approach_NN1 ._. "_" 
"_" It_PPH1 's_VBZ very_RG pleasing_JJ to_TO see_VVI the_AT new_JJ results_NN2 ,_, "_" says_VVZ Daniel_NP1 Branton_NP1 of_IO Harvard_NP1 University_NN1 ,_, who_PNQS is_VBZ developing_JJ nanopore_NN1 DNA_NN1 sequencing_NN1 with_IW solid-state_JJ materials_NN2 ._. 
"_" This_DD1 is_VBZ the_AT first_MD time_NNT1 a_AT1 clear_JJ ,_, feasible_JJ pathway_NN1 to_TO nanopore_VVI sequencing_NN1 has_VHZ been_VBN shown_VVN ._. 
I_PPIS1 would_VM guess_VVI that_CST within_II a_AT1 year_NNT1 there_EX will_VM be_VBI a_AT1 clear_JJ demonstration_NN1 of_IO actual_JJ DNA_NN1 sequencing_NN1 with_IW a_AT1 nanopore_NN1 ._. "_" 
Stuart_NP1 Lindsay_NP1 of_IO Arizona_NP1 State_NN1 University_NN1 ,_, an_AT1 expert_NN1 in_II single-molecule_JJ DNA_NN1 sequencing_NN1 ,_, says_VVZ Bayley_NP1 and_CC coworkers_NN2 "_" certainly_RR have_VH0 a_AT1 wonderful_JJ single-nucleotide_JJ detector_NN1 technology_NN1 ,_, and_CC this_DD1 paper_NN1 has_VHZ raised_VVN it_PPH1 to_II new_JJ heights_NN2 by_II making_VVG it_PPH1 much_RR more_RGR reliable_JJ and_CC by_II showing_VVG that_DD1 nucleotide_NN1 methylation_NN1 can_VM be_VBI detected_VVN ,_, which_DDQ is_VBZ going_VVGK to_TO be_VBI of_IO incredible_JJ medical_JJ importance_NN1 ._. "_" 
