**5. Conclusions**

Concluding, we can state that it was received the most complete up to now quantum map of the biologically-important conformationally-tautomeric transitions of the classical AT/AU nucleobase pair, which enable to classify it as a *quantum choreography with all further going consequences*. But it is not a pursuit of a new term, but rather an attempt to realize the molecular logic of the quantum evolution at its initial stages, when it was formed its behavior, which is evolutionary programmed in its electronic structure.

**References**

[1] Watson, J.D., Crick, F.H.C.

*Nature*, 1953, 171, 737–738.

Molecular structure of nucleic acids: A structure for deoxyribose nucleic acid.

*DOI: http://dx.doi.org/10.5772/intechopen.94565*

[11] Brovarets', O.O. Under what

[12] Brovarets', O.O. Structural and energetic properties of the four

[13] Abrescia, N.G., Thompson, A., Huynh-Dinh, T., & Subirana, J.A. Crystal structure of an antiparallel DNA fragment with Hoogsteen base pairing. *Proc. Natl. Acad. Sci. USA*, 2002, *99*,

[14] Abrescia, N.G., Gonzalez, C., Gouyette, C., & Subirana, J.A. X-ray and NMR studies of the DNA oligomer d (ATATAT): Hoogsteen base pairing in duplex DNA. *Biochemistry*, 2004, *43,*

[15] Pous, J., Urpi, L., Subirana, J.A., Gouyette, C., Navaza, J., & Campos, J.L. Stabilization by extra-helical thymines of a DNA duplex with Hoogsteen base pairs. *J. Am. Chem. Soc.,* 2008, *130*,

[16] Campos, L., Valls, N., Urpí, L., Gouyette, C., Sanmartín, T., Richter, M., Alechaga, E., Santaolalla, A., Baldini, R., Creixell, M., Ciurans, R., Skokan, P., Pous, J., & Subirana, J.A. Overview of the structure of all AT oligonucleotides: organization in helices and packing interactions. *Biophys. J.*, 2006, 91, 892–903.

[17] Nikolova, E.N., Zhou, H., Gottardo F. L., Alvey, H. S., Kimsey, I. J., & Al-Hashimi, H. M. A historical account of Hoogsteen base-pairs in duplex DNA. *Biopolymers,* 2014, 99, 955–968.

[18] Alvey, H.S., Gottardo, F.L., Nikolova, E.N., & Al-Hashimi, H.M.

configurations of the AT and GC DNA base pairs. *Ukr. Biochem. J.,* 2013, 85,

85, 98–103.

*Where Quantum Biochemistry Meets Structural Bioinformatics: Excited Conformationally…*

104–110.

2806–2811.

4092–4100.

6755–6760.

conditions does GC Watson-Crick DNA base pair acquire all four configurations characteristic for AT Watson-Crick DNA base pair? *Ukr. Biochem. J.,* 2013,

[2] Watson, J.D., Crick, F.H.C. The structure of DNA. *Cold Spring Harbor Symp. Quant. Biol.*, 1953, 18, 123–131.

[3] Saenger, W. *Principles of nucleic acid structure*. New York, NY: Springer, 1984.

[4] Wilkins, M. *The third man of the double helix: the autobiography of Maurice Wilkins*. Oxford University Press, 2003.

[5] Hoogsteen, K. The crystal and molecular structure of a hydrogen bonded complex between 1-

*Acta Cryst.,* 1963, 16, 907–916.

363–371.

methylthymine and 9-methyladenine.

[6] Donohue, J., & Trueblood K.N. Base pairing in DNA. *J. Mol. Biol.*, 1960, 2,

[7] Cubero, E., Luque, F.J., & Orozco, M. Theoretical studies of d(A:T)-based parallel-stranded DNA duplexes. *J. Am. Chem. Soc.*, 2001, 123, 12018–12025.

[8] Poltev, V. I., Anisimov, V. M., Sanchez, C., Deriabina, A., Gonzalez, E., Garcia, D., Rivas, N., & Polteva, N. A. Analysis of the conformational features of Watson–Crick duplex fragments by molecular mechanics

[9] Ye, M. Y., Zhu, R. T., Li, X., Zhou, X.

fluorescent DNA polarity analysis. *Anal.*

[10] Szabat, M., & Kierzek, R. Parallelstranded DNA and RNA duplexes: structural features and potential applications. *FEBS J.,* 2017, 284,

and quantum mechanics methods. *Biophysics*, 2016, 61, 217–226.

S., Yin, Z. Z., Li, Q., & Shao, Y. Adaptively recognizing parallelstranded duplex structure for

*Chem.,* 2017, 89, 8604–8608.

3986–3998.

**13**

For the first time, it was shown for the classical AT DNA base pair that prototropic tautomerism of the DNA bases is responsible both for the origin, as well as for the supporting of the unusual local structures in the constitution of DNA and in complexes with proteins and small biomolecules. Moreover, prototropic tautomerism of the classical AT DNA base pair significantly expands its conformational possibilities and its impact on the biological importance.

It is connected with the fact that presented mechanisms of the tautomerization are assisted by the significant changing of the geometry of the tautomerizing base pair. This means that they are conformationally-tautomeric transitions by their essence.

This conclusion is confirmed by the structural bioinformatics. Thus, it was identified hundredth of the structures containing tautomers of the DNA bases. This fact points that all described exited conformationally-tautomeric states of the AT and AU nucleobase pairs, corresponding to local minima, are real structures.
