04蛋白质结构allarea脯氨酸.pdf

Proteins • Proteins comprise the majority of the cells dry weight mass • Proteins perform many functions – Transporters – Enzymes – Structural – Machines (movement) – Regulatory Amino acids • Proteins are made up of 20 “standard” amino acids • All are a-amino acid cept proline脯氨酸 which has a secondary amine group R Side chain H N 2 C COOH -Carbon atom H Protein building blocks • Amino acid side chain properties – Acidic – basic – Sulphur containing – hydrophobic – hydrophilic – Side chain size (small or large) – Side chain polar or non-polar. Roles of amino acids in proteins • Hydrogen bonding • Formation of salt bridges盐桥 • Van der Waals in ctions 耳斯相互 作用 • Hydrophobic in ctions • Important roles in structure/ specificity and activity Protein Structure • Primary Structure • Amino acid Sequence • Secondary Structure • a-helix, b-sheet etc • Tertiary structure • Disulphide二硫化物 bond positi c • Spatial空间的 organisation of a -helical and b -sheet regions • Shape of molecule • Quaternary structure • Sub-unit composition The peptide bond • Amino acids in proteins linked via peptide bonds H R1 O R2 O H N H N 2 C C C C O-