bis102-10-5 - atom attached to the nitrogen of one peptide...

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10-5-2011 Secondary Structure of Proteins (2 degree structure) - refers to the conformation of the peptide backbone -has resonance-- confer stability to bond. - more rigid than normal covalent bond. cant rotate freely. -C - N has some double bond character X-ray crystallography - means of studying protein conformation by determining the position of atoms in space. the 4 atoms that comprise the peptide bond lie in a single plane. peptide backbone: The oxygen and the hydrogen are trans to each other. Models were made to determine the possible ways a peptide chain can twist or fold in view of the constraints simplest: alpha- helix. .. right hand fist. . grows upward and winds counterclockwise. 3.6 amino acids per turn of the helix. The R groups would extend outward from the backbone. alpha -helix permits the formation of intrachain hydrogen bonds between the hydrogen
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Unformatted text preview: atom attached to the nitrogen of one peptide linkage to the oxygen of the carbonyl group of the 4th amino acid behind it. -- max binding and stability. Energetically most feasible form. Each peptide bond in chain participates in hydrogen bonding. . chain is thus maximally hydrogen bonded.-correlates with alpha keratin-- known as fibrous proteins-- component of hair and nails. peptide chains are expected to form alpha helixes spontaneously because it form is the most stable and has the least free energy. exception: if proline is present it interrupts the alpha helix to create a bend. .. since its too rigid. an alpha helix cannot form if there are opposing interactions of the R groups or solvent. ex. polylysine cannot form an alpha helix at ph 7 because of its R group have a positive charge....
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This note was uploaded on 01/15/2012 for the course BIS 102 taught by Professor Hilt during the Fall '08 term at UC Davis.

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bis102-10-5 - atom attached to the nitrogen of one peptide...

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