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A
total of 348 DNA sequences 16-30 mers long with experimental
Tm, salt and oligonucleotide concentrations available were
used in this benchmark: 37 sequences were obtained from the
work of Owczarzy et al., 1998; 11 sequences were
obtained from NTDB database (Chiu et al., 2003);
and the remaining 300 sequences were obtained from Owczarzy
et al., 2004. The full table containing all the experimental
values and the theoretical predictions by using the various
methods is available here. The melting temperatures were predicted
with the basic method (BAS),
the salt adjusted method (SAL),
and the NN model with the thermodynamic parameters of Breslauer
et al., 1986 (BRE),
SantaLucia et al., 1986 (SAN),
and Sugimoto et al., 1986 (SUG).
The melting temperature was also predicted using the consensus
method (CON)
proposed by us (Panjkovich and Melo), which is based
on the results obtained in the comparative study and shown
in the following Figure.
The consensus melting temperature corresponds to the average
melting temperature of those methods that exhibit similar
results at a given grid point of the oligonucleotide feature
space. In those cases where no similarities are observed among
methods (black regions of the Figure),
the average of all melting temperature values was used (top
values within each cell). The results of the benchmark using
the 281 sequences that map in zones 1, 2 and 3 (excluding
those sequences from the black regions in the Figure)
are shown between parentheses (bottom values within each cell).
Four different accuracy measures are reported in this table.
First, the percentage of cases where the method gives the
closest prediction to the experimental Tm (BEST);
then the percentage of cases where the method gives a prediction
within 5 and 3 Celcius degrees from the experimental Tm (ERROR);
and finally, the average of the absolute differences between
the method prediction and the experimental Tm for all the
cases considered (AVE.
ERROR).
|
Accuracy
Measure |
BAS |
SAL |
BRE |
SAN |
SUG |
CON |
BEST
(%) |
0.57
(0.00) |
5.17
(6.41) |
3.45
(2.14) |
40.80
(38.08) |
26.15
(27.05) |
23.85
(26.33) |
ERROR
< 5° C (%) |
11.21
(9.61) |
31.03
(35.23) |
26.15
(24.56) |
83.33
(83.99) |
83.62
(84.34) |
83.91
(86.12) |
ERROR
< 3° C (%) |
3.74
(2.85) |
14.94
(17.44) |
14.37
(12.46) |
60.92
(57.30) |
60.06
(62.63) |
61.49
(64.06) |
AVE.
ERROR (° C) |
12.28
(12.56) |
7.11
(6.69) |
8.45
(8.60) |
2.85
(2.98) |
2.86
(2.73) |
2.84
(2.65) |
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Breslauer,K.J.,
Frank,R., Blöcker,H. and Marky,L.A. (1986) Predicting
DNA duplex stability from the base sequence. Proc.
Natl. Acad. Sci. USA, 83, 3746-3750.
SantaLucia,J.,Jr,
Allawi,H.T. and Seneviratne,P.A. (1996) Improved nearest-neighbor
parameters for predicting DNA duplex stability. Biochemistry,
35, 3555-3562.
Sugimoto,N.,
Nakano,S., Yoneyama,M. and Honda,K. (1996) Improved thermodynamic
parameters and helix initiation factor to predict stability
of DNA duplexes. Nucleic Acids Res., 24, 4501-4505.
Owczarzy,R.,
Vallone,P.M., Gallo,F.J., Paner,T.M., Lane,M.J. and Benight,A.S.
(1998) Predicting sequence-dependent melting stability
of short duplex DNA oligomers. Biopolymers, 44, 217-239.
Chiu,W.L.,
Sze,C.N., Ma,N.T., Chiu,L.F., Leung,C.W. and Au-Yeung,S.C.
(2003) NTDB: Thermodynamic Database for Nucleic Acids,
Version 2.0. Nucleic Acids Res., 31, 483-485.
Owczarzy,R.,
You,Y., Moreira,B.G., Manthey,J.A., Huang,L., Behlke,M.A.
and Walder,J.A. (2004) Effects of sodium ions on DNA duplex
oligomers: improved predictions of melting temperatures. Biochemistry,
43, 3537-3554.
Panjkovich,
A. and Melo, F. (2004) Comparison of DNA melting temperature
calculation methods for short DNA sequences. Bioinformatics (in press).
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