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Nucleic Acid Structure & Conformation - Intro

Nucleic Acid Structure & Conformation - Intro. M.Bansal. --Lehninger 5 th Ed. WC base-pairing. Hoogsteen base-pairing. The x-ray fibre diffraction pattern of sodium salt of DNA-B at 90% R.H.(Rosalind Franklin 1953). DNA facts: Deoxyribose - Nucleic Acid Base composition:

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Nucleic Acid Structure & Conformation - Intro

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  1. Nucleic Acid Structure & Conformation - Intro M.Bansal

  2. --Lehninger 5th Ed

  3. WC base-pairing Hoogsteen base-pairing

  4. The x-ray fibre diffraction pattern of sodium salt of DNA-B at 90% R.H.(Rosalind Franklin 1953)

  5. DNA facts: • Deoxyribose - Nucleic Acid • Base composition: • Erwin Chargaff • (A)=(T), (G)=(C) • X-ray pattern: • Rosalind Franklin • Structure: • James Watson & Francis Crick • - base pairing between • A-T and G-C • - double helical model with • 10 units per turn.

  6. aO3’-P-O5’-C5’ (g-) bP-O5’-C5’-C4’ (t) g O5’-C5’-C4’-C3’ (g+ ) d C5’-C4’-C3’-O3’ (2E) e C4’-C3’-O3’-P (t) z C3’-O3’-P-O5’ (g-) Backbone conformation

  7. The puckering of the ribose ring is described by the phase angle P, where (ν2+ν4)-(ν1+ν3) P = arctan -------------------------------- 2ν0[sin(π/5)+sin(2π/5)]

  8. 5’ 5’ 5’ B Z A

  9. Torsion Angles Corresponding to A, B, Z DNA Structures n 11 10 -6 h 2.56 3.3 7.2

  10. DNA structures from A to Z The various forms of DNA have been identified as A, B, C etc. In fact, a detailed inspection of the literature reveals that only the letters F, Q, U, V and Y are now available, to describe any new DNA structure that may appear in future.Itis also apparent that it may be more relevant to talk about the A, B or C type dinucleotide steps,since several recent structures show mixtures of various different geometries and a careful analysis is essential before identifying it as a ‘new structure’. A Glossary of DNA structures from A to Z A. Ghosh & M. Bansal , Acta Cryst D, vol 59 (Apr 2003)

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