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Torsion Angles Dihedral Angles. Saenger, Wolfram. Principles of Nucleic Acid Structure . Springer-Verlag New York Inc., 1984, p. 15. Water hydrogen bonding. Voet, Donald and Judith G. Biochemistry . John Wiley & Sons, 1990, p. 30. Ice structure.
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Torsion Angles Dihedral Angles Saenger, Wolfram. Principles of Nucleic Acid Structure. Springer-Verlag New York Inc., 1984, p. 15.
Water hydrogen bonding Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 30.
Ice structure Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 31.
Clathrate hydrates Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 179.
Torsion Angles Dihedral Angles Saenger, Wolfram. Principles of Nucleic Acid Structure. Springer-Verlag New York Inc., 1984, p. 15.
Components: Sugar, Base, Phosphate • 5’ to 3’ direction • RNA - ribose • DNA- deoxyribose • Numbering Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 792.
Names Numbering Bonding character Position of hydrogen Tautomers Neidle, Stephen. Nucleic Acid Structure and Recognition. Oxford University Press, 2002, p. 18.
Geometry of Watson Crick base pairs A:T and G:C are similar Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 797.
Backbone conformation Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 807.
B DNA View down helix axis Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 799.
Space filling B DNA Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 796.
A DNA Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 800.
Z DNA Left handed Very deep minor groove Major groove on outside Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 802.
A form conformation Neidle, Stephen. Nucleic Acid Structure and Recognition. Oxford University Press, 2002, p. 141.
Conserved and semi conserved bases Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 905.
Four Levels of Protein Structure • Primary, 1o • the amino acid sequence • Secondary, 2o • Local conformation of main-chain atoms (FandYangles) • Tertiary, 3o • 3-D arrangement of all the atoms in space (main-chain and side-chain) • Quaternary, 4o • 3-D arrangement of subunit chains
Primary, alent bonds. Secondary, Tertiary, Quaternary - determined by weak forces (H-bonds, etc.)
Amino Acids • It is the amino acid sequence that “exclusively” determines the 3D structure of a protein • 20 amino acids – modifications do occur post protein synthesis
Amino Acids “corn crib” Voet, Donald and Judith G. Biochemistry. John Wiley & Sons, 1990, p. 68.
Peptide Bond Formation • Individual amino acids form a polypeptide chain • Such a chain is a component of a hierarchy for describing macromolecular structure • The chain has its own set of attributes
A dihedral angle is the angle between two planes defined by 4 atoms – 123 make one plane 234 the other • Omega is the rotation around the peptide bond Cn – Nn+1 – it is planar and is 180 under ideal conditions • Phi is the angle around N – Calpha • Psi is the angle around Calpha C’ • The values of phi and psi are constrained to certain values based on steric clashes of the R group. Thus these values show characteristic patterns as defined by the Ramachandran plot Geometry of the Chain From Brandon and Tooze
Shows allowed and disallowed regions Gly and Pro are acceptions: Gly has no limitation; Pro is constrained by the fact its side chain binds back to the main chain Gray = allowed conformations. bA, antiparallel b sheet; bP, parallel b sheet; bT, twisted b sheet (parallel or anti-parallel); a, right-handed a helix; L, left-handed helix; 3, 310 helix; p, p helix. Ramachandran Plot
If N-terminus is at bottom, then all peptide N-H bonds point “down” and all peptide C=O bonds point “up”. N-H of residue n is H-bonded to C=O of residue n+4. a-Helixhas: 3.6 residues per turn Rise/residue = 1.5 Å Rise/turn = 5.4Å aHelix
Polar Hydrophobic Amphipathic R-groups extend radially from the a-helix core, shown in helical wheel diagram. a-helicescan be:
Stabilized by interchain H-bonds between N-H & C=O Peptide chains are fully extended; pleated shape because adjacent peptides groups can’t be coplanar. b Sheet
bSheet - 2 Orientations Parallel Not optimum H-bonds; less stable Anti-parallel Optimum H-bonds; more stable
The Beta Turn – 2 Conformations Only Difference
Quaternary Structure: Ferritin The Body’s Iron Storage Protein
Super-secondary Structure b-turnsin a protein chain allow helices and sheets to align side-by-side bab aa bmeander