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Unformatted text preview: ill defeated by exponential explosion.
¶8. Lipton (1995) estimates that it is feasible for n 70, but this is also
within the range of conventional computer.
¶9. Massive parallelism: Nevertheless, Adleman’s algorithm illustrates
the massive parallelism of molecular computation.
Step 1 (generation of all possible paths) took about an hour for n = 7.
Adleman estimates that about 1014 ligation operations were performed,
and that it could be scaled up to 1020 operations.
Therefore, speeds of about 1015 to 1016 ops/sec (1–10 peta-operations/s)
should be achievable.
That is, digital supercomputer range. 236 CHAPTER IV. MOLECULAR COMPUTATION ¶10. Energy: Adlemen estimates that 2 ⇥ 1019 ligation operations were
performed per joule of energy.
Contemporary supercomputer perform only 109 operations per joule,
so MC is 1010 more energy e cient.
¶11. It is near the thermodynamic limit of 34 ⇥ 1019 operations per joule.
Recall (Ch. II, Sec. B.1) kT ln 2 ⇡ 3 ⇥ 10 9 pJ = 3 ⇥ 10 21 J, so there
can be about 3.3 ⇥ 1020 bit changes/J.
¶12. Space: One bit of information occupies about 1 cubic nm.
Contemporary disks store a bit in about 1010 cubic nm.
That is, a 1010 improvement in density.
¶13. Inherent error: A more pervasive problem is the inherent error in
the ﬁltering processes (due to incorrect hybridization).
Some strands we don’t want, get through; and some that we do want,
With many ﬁltering stages the errors accumulate to the extent that the
¶14. There are some approaches to error-resistant DNA computing....
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- Fall '13