5060 Nucleic Acids Research, 2008, Vol. 36, No. 15 26. Livnah,O., Bayer,E.A., Wilchek,M. and Sussman,J.L. (1993) Three- dimensional structures of avidin and the avidin–biotin complex. Proc Natl Acad. Sci. USA, 90, 5076–5080. 27. Wilchek,M., Bayer,E.A. and Livnah,O. (2006) Essentials of biorecognition: The (strept)avidin–biotin system as a model for protein–protein and protein–ligand interaction. Immunol. Lett., 103, 27–32. 28. Diamandis,E.P. and Christopoulos,T.K. (1991) The biotin-(strept)avidin system: principles and applications in biotech- nology. Clin. Chem., 37, 625–636. 29. Wilchek,M. (2004) My life with aﬃnity. Protein Sci., 13, 3066–3070. 30. Wilchek,M. and Bayer,E.A. (1999) Foreword and introduction to the book (strept)avidin–biotin system. Biomol. Eng., 16, 1–4. 31. Gonza´ lez,M., Argaran˜ a,C.E. and Fidelio,G.D. (1999) Extremely high thermal stability of streptavidin and avidin upon biotin bind- ing. Biomol. Eng., 16, 67–72. 32. Laitinen,O.H., Marttila,A.T., Airenne,K.J., Kulik,T., Livnah,O., Bayer,E.A., Wilchek,M. and Kulomaa,M.S. (2001) Biotin induces tetramerization of a recombinant monomeric avidin. J. Biol. Chem., 276, 8219–8224. 33. Wilchek,M., Rothenberg,J.M., Reisfeld,A. and Bayer,E.A. (1990) Direct incorporation of biotin into DNA. Method Enzymol., 184, 608–812. 34. Langer,P.R., Waldrop,A.A. and Ward,D.C. (1981) Enzymatic synthesis of biotin-labeled polynucleotides: novel nucleic acid aﬃnity probes. Proc. Natl Acad. Sci. USA, 78, 6633–6637. 35. Cantor,C.R., Warshaw,M.M. and Shapiro,H. (1970) Oligonucleotide interactions. III. Circular dichroism studies of the conformation of deoxyoligonucleotides. Biopolymers, 9, 1059–1077. 36. Inove,H., Sato,K. and Anzai,J. (2005) Disintegration of layer-by-layer assemblies composed of 2-iminobiotin-labled poly(ethyleneimine) and avidin. Biomacromolecules, 6, 27–29. 37. Horcas,I., Fernandez,R., Gomez-Rodriguez,J.M., Colchero,J., Gomez-Herrero,J. and Baro,A.M. (2007) WSXM: A software for scanning probe microscopy and a tool for nanotechnology. Review of Scientiﬁc Instruments, 78, 013705. 38. Medalsy,I., Dgany,O., Sowwan,M., Cohen,H., Yukashevska,A., Wolf,S.G., Wolf,A., Koster,A., Almog,O. et al. (2008) SP1 protein-based nanostructures and arrays. Nano Letters, 8, 473–477. 39. Kotlyar,A.B., Borovok,N., Molotsky,T., Fadeev,L. and Gozin,M. (2005) In vitro synthesis of uniform poly(dG)–poly(dC) by Klenow exo fragment of polymerase I. Nucleic Acids Res., 33, 525–535. 40. Borovok,N., Molotsky,T., Ghabboun,J., Cohen,H., Porath,D. and Kotlyar,A. (2007) Poly(dG)-poly(dC) DNA appears shorter than Poly(dA)-poly(dT) and possibly adopts an A-related conformation on a mica surface in ambient. FEBS Lett., 581, 5843–5846. 41. Saenger,W. (1984) Principles of Nucleic Acids Structure. Springer, New York. 42. Franklin,R.E. and Gosling,R.G. (1953) The structure of sodium thymonucleate ﬁbers. I. The inﬂuence of water content. Acta Crystallog., 6, 673–677. 43. Kang,C., Zhang,X., Ratliﬀ,R., Moyzis,R. and Rich,A. (1992) Crystal structure of four-stranded Oxytricha telomeric DNA. Nature, 356, 126–131. 44. Smith,F.W., Schultze,P. and Feigon,J. (1995) Solution structures of unimolecular quadruplexes formed by oligonucleotides containing Oxytricha telomere repeats. Structure, 3, 997–1008.