DNA Length Dependence on Laser Tube Separation

1
DNA Length Dependence on Laser Tube Separation
(GT)10-LaCNT
(GT)20-LaCNT
M11
S22
No metallic enrichment for (GT)20

• Shorter DNA sequence produces a much more
  effective metal/semiconductor separation.
• smaller helical pitch
• larger difference in net effective linear charge
  density

2
DNA Helical Wrap
Roll up
DNA wrapping helix
For a 1 nm SWNT, 20 mer is needed to wrap a
full turn. Total possible sequences 420 Full
of potential, but a search strategy is needed
3
Sequence Expansion
As a way to effectively cover the sequence
parameter space. It is also a natural extension
of our previous work. 1st order expansion
(mononucleotide repeat) M20 , where M G, or A,
or T, or C total sequences 4 2nd order
expansion (di-nucleotide repeat) (D1D2)10 ,
where Di G, or A, or T, or C total sequences
16 3rd order expansion (tri-nucleotide
repeat) (T1T2T3)7 , where Ti G, or A, or T, or
C total sequences 64 4th order expansion
(quadr-nucleotide repeat) (Q1Q2Q3Q4)5 , where Qi
G, or A, or T, or C total sequences
256 . . .
4
Tri-nucleotide repeat
Quadr--nucleotide repeat
For tri-nucleotide repeat sequences, a 30-mer is
used to disperse HiPco tubes.
5
Chirality Enrichment in HiPco
(8,6) tubes elute at early fractions along with
metallic tubes.
(8, 6)
6
Chirality Enrichment in HiPco
(9,1) Also found in (CCA)10 and (TGA)10 wrapped
HiPco fractions.
7
Chirality Enrichment from CoMoCAT
(9, 1) d 0.757 nm
(6, 5) d 0.757 nm
Chirality separation among nanotubes of very
similar diameter. The ability to extract a very
minor species from a mixture.
8
Metal Enrichment in HiPco

• T rich sequences can enrich metallic tubes, e.g.
  (TTA)10, (TTC)10
• Metallic tubes elute at early fractions.

9
Metal/Semiconductor Separation of Laser Tubes
M11
M22
S22
S33
10
Laser Tube Dispersion

• DNA Sequence dependence
• DNA Length dependence

11
Can DNA separate SWNTs of large diameters?
(TTA)10-LaCNT
(TTA)6-LaCNT
(15,0) d 1.19

• Tuning ssDNA sequence
• Reducing ssDNA Length

12
Summary

• Lots of interesting sequences from the
  tri-nucleotide repeat studies for
  metal/semiconductor separation and chirality
  enrichment.
• A few quadr-nucleotide repeat sequences (0,1 and
  2 purines) give some metal/semiconductor
  separation, but the overall performance is not as
  exciting.
• Unexpected DNA length dependence on the laser
  tube separation. Shorter is better.
• By tuning the DNA sequence and length,
  purification of nanotube with specific electronic
  type and chirality can be achieved.