《生物化学 Biochemistry》课程教学资源（双语教程PPT）Chapter 2 Protein Section 3 Proteins - Secondary, Tertiary, and Quaternary Structure

Chapter 2 Protein Section 3 Proteins: Secondary, Tertiary, and Quaternary Structure

Chapter 2 Protein Section 3 Proteins: Secondary, Tertiary, and Quaternary Structure

Outline 6.1 Forces Influencing Protein Structure 6.2 Role of the Amino Acid sequence in Protein structure 6. 3 Secondary structure of Proteins 6.4 Protein Folding and Tertiary Structure 6.5 Subunit Interactions and Quaternary Structure

Outline 6.1 Forces Influencing Protein Structure 6.2 Role of the Amino Acid Sequence in Protein Structure 6.3 Secondary Structure of Proteins 6.4 Protein Folding and Tertiary Structure 6.5 Subunit Interactions and Quaternary Structure

6.1 The weak forces What are they What are the relevant numbers van der waals:0,4-4 kj/mol hydrogen bonds: 12-30 kJ/mol ionic bonds: 20 kJ/mol hydrophobic interactions: <40 kJ/mol

6.1 The Weak Forces What are they? What are the relevant numbers? • van der Waals: 0.4 - 4 kJ/mol • hydrogen bonds: 12-30 kJ/mol • ionic bonds: 20 kJ/mol • hydrophobic interactions: <40 kJ/mol

Com parison of bond energies covalent and non-covalent Non-covalent Inter actions 200 hydroph obic interaction: si-o order ing of water around nonpolar groups ts decreased as thes e 150 groups become buried within molecule C-F hydrogen bond: associations b etween E100 C-OH polar groups e containing O and N electrostatic bond: 50 C salt bridges between c- no positively and neg atively m charged groups van der waals bond: weak associations between nonpolar groups

van der waals(落德华力) 58 Covalent van der Waals radius radius 0062mm (0.14nm

van der Waals(范德华力）:

hydrogen bonds(氢键) Hydrogen Bonds in Biological Molecules Hydrogen donor. acceptor Comments m ajor factor in the 0-H:0 structural stability of water 0-H:·0 N-H.0 bonding of water SH to other molecules N-H…0=C 0-H:·0=C very important in structural stability of / H proteins and nucleic N-H。O acids R C.H:··0三C weaker bonds relatively rare

hydrogen bonds（氢键）:

ionic bonds(离子键) ain chain ain chain HO NH a HN o-C O C-O HCCH2CH2CH2CH2NHg………O-C-CH2CH2CH HN sine Glutamate NH C=0 CI O-C N HO

ionic bonds（离子键）

hydrophobic interactions (疏水相互作用) HYDROPHOBIC FORCES

hydrophobic interactions （疏水相互作用）

Protein Protein NH -CH2 -OH. 0=C-CH2 -CH,- Hydrogen CH2-CH2-NH3O C-CH2-CH lonic bond cH CH--CH3 CHa C CHa--CH-CHz Hydrophobic and van der Waals CH一CHcH3-CH Interactions CHa CHa CH2-C HaN-CH2-- lonic bond

What forces determine the structure? Primary structure determined by covalent bonds Secondary, tertiary, Quaternary structures all determined by weak forces Weak forces -hbonds. ionic interactions van der waals interactions, hydrophobic interactions

What forces determine the structure? • Primary structure - determined by covalent bonds • Secondary, Tertiary, Quaternary structures - all determined by weak forces • Weak forces - H-bonds, ionic interactions, van der Waals interactions, hydrophobic interactions