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Exploring Amino Acids and Protein Structure: Fundamentals and Classification

Learn about amino acids, their structures, classifications, and protein hierarchy. Understand the properties and classifications of 20 amino acids, peptide bonds, and secondary protein structures.

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Exploring Amino Acids and Protein Structure: Fundamentals and Classification

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  1. 技术一班林祥庆20052503429 Unit1 protein

  2. Amino acid • The structure of amino acids • The abbreviation of 20 amino acids • The classification of amino acids • The amino acids’ pI • Peptide bone

  3. An amino acid is defined as the molecule containing an amino group (NH2), a carboxyl group (COOH) and an R group. It has the following general formula, • R-CH(NH2)-COOH • The R group differs among various amino acids. In a protein, the R group is also called asidechain. structure

  4. Different side-chain (R group) • Different chemical and physical properties Amino group Carboxylic acid group

  5. Two kinds of classification ways • R group’ structure • The polarity of the R group

  6. neutral amino acid : Gly Ala Val Leu Ile Ser Thr Cys • Met • acidic amino acid : Asp Glu Asn Gln • basic amino acid : Arg Lys

  7. negatively charged :Asp Glu • polar-amino acid positively charged :Lys Arg His • uncharged :Gly Ser Thr Cys Tyr Asn Gln • non-poalr amino acid : Ava Avl Leu Ile Pro Phe Trp Met

  8. How to judge the form of the amino acid in different PH? • pH=pI The amino acid is zwitterion. • pH<pI The amino acid is protonated. • pH>pI The amino acid is deprotonated

  9. Peptide bond

  10. Hierarchy of protein structure

  11. Regular, repeated coiling and folding of polypeptide backbone Due to hydrogen bonding Four patterns  (alpha) helix  (beta) sheet  turn Random coil Secondary structure

  12. The -helix • The formation of the a-helix is spontaneous and is stabilised by H-bonds in backbone NH…O=C spaced four residues apart. • Right-handed and Left-handed • Side-chains point out

  13. Top view

  14. excise • Which chemical bond keeps the protein’ secondary structure? ( D ) • A chemical bond B hydrophobic interaction C peptide bone D hydrogen bone E Disulfidbruecken

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