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  FTIR and UV spectroscopy of parallel-stranded DNAs with mixed A·T/G·C sequences and their inosine analogs.

Mohammadi, S., Klement, R., Shchyolkina, A. K., Liquier, J., Jovin, T. M., & Tallandier, E. (1998). FTIR and UV spectroscopy of parallel-stranded DNAs with mixed A·T/G·C sequences and their inosine analogs. Biochemistry, 37, 16529-16537.

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Mohammadi, S., Author
Klement, R.1, Author           
Shchyolkina, A. K., Author
Liquier, J., Author
Jovin, T. M.2, Author           
Tallandier, E., Author
Affiliations:
1Emeritus Group Laboratory of Cellular Dynamics, MPI for biophysical chemistry, Max Planck Society, ou_578629              
2Department of Molecular Biology, MPI for biophysical chemistry, Max Planck Society, ou_578628              

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 Abstract: The infrared spectra of parallel-stranded (ps) hairpin duplexes with mixed AT/GC composition and either isolated or sequential G·C pairs were studied in comparison with antiparallel-stranded (aps) duplexes and a corresponding set of with molecules with inosine as a G base analog lacking the exocyclic amino group. The ps duplexes showed the characteristic bands for the C2=O2 and C4=O4 stretching vibrations of thymine residues in trans-Watson-Crick A·T pairing at 1683 cm-1 and 1668 cm-1. The latter band was superimposed on the stretching vibration of the free C6=O6 group of guanine. Substitution of guanines by inosines inhibited the formation of ps hairpin duplexes whatever the sequence, demonstrating that in the H-bonding between G and C the 2-NH2 group is necessary for stabilizing all of the investigated ps duplexes with mixed AT/GC composition. This result is in agreement with a model of trans-Watson-Crick G·C base pairs with 2 H-bonds [N2H2(G)-N3(C)) and (N1H(G)-O2(C)]. However, trans-Watson-Crick A·T and G·C base pairs with two H-bonds are not isomorphous, which may explain the decreased stability of the ps, but not the aps, duplexes upon increasing the number of AT/GC junctions. Molecular modelling studies performed on two of the ps duplexes reveal the existence of propeller twist for avoiding a clash between the N2(G) and N4(C) amino groups, and favorable stacking of sequential G·C base pairs. The optimized hairpin ps duplexes invariably incorporated G·C base pairs with two H- bonds, regardless of the initial structures adopted for the force field calculations.

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Language(s): eng - English
 Dates: 2005-07-061998
 Publication Status: Issued
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 Identifiers: eDoc: 231762
Other: 635
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Title: Biochemistry
Source Genre: Journal
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Pages: - Volume / Issue: 37 Sequence Number: - Start / End Page: 16529 - 16537 Identifier: -