CHMI-2227EL Lecture Notes - Lecture 6: Dextran, Molecular Sieve, Sepharose
27 Jun 2018
School
Course
Professor
Biochemistry - Day 6 2018.01.31
Architecture of Proteins
-Shape can be globular or fibrous
-Globular proteins
-Compact: spherical molecules, usually water soluble (dissolved in biological fluid)
-Dynamic: flexible because they bind precisely to other molecules (ex. hemoglobin)
-Fibrous proteins
-Water insoluble proteins with high
strength (ex. collagen, keratin)
-Ex. Bighorm rams have horns made of
alpha-keratin
-Ex. Wave perm (alpha-keratin)
-The hair is treated with reducing agent to clear the disulphide bridges
-The treatment converts the -S-S- bonds into -SH HS- bonds
-This will impose new shape (curl) to the hair
-Then the shape will be set with an oxidizing agent that will convert the -SH HS-
bonds into -S-S- bonds (disulfide bridges) between cysteine residues in the
proteins of the hair
Levels of Protein Structure
-Primary
-Sequence of amino acid residues,
joined by peptide bonds
-This sequence is coded for by DNA
-Secondary
-Folding of polypeptide chain, which
will form arrangements of
neighbouring amino acid residues in
the linear sequence
-Caused by hydrogen bonds between
the peptide backbone carbonyl: N-H groups
-Tertiary
-Overall 3D shape, side chain (R) interactions
-Primary structure dictates tertiary structure as the sequence of the amino acids will
affect which amino acids interact with one another in the tertiary structure
-Quaternary
-Subunit interactions by different polypeptide chains, proteins containing 2+
polypeptide chains
-What forces determine the structure?
-Primary structure: covalent bonds
-Secondary, tertiary, quaternary structure: weak forces
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Document Summary
Compact: spherical molecules, usually water soluble (dissolved in biological uid) Dynamic: exible because they bind precisely to other molecules (ex. hemoglobin) Water insoluble proteins with high strength (ex. collagen, keratin) The hair is treated with reducing agent to clear the disulphide bridges. The treatment converts the -s-s- bonds into -sh hs- bonds. This will impose new shape (curl) to the hair. Then the shape will be set with an oxidizing agent that will convert the -sh hs- bonds into -s-s- bonds (disul de bridges) between cysteine residues in the proteins of the hair. Sequence of amino acid residues, joined by peptide bonds. This sequence is coded for by dna. Folding of polypeptide chain, which will form arrangements of neighbouring amino acid residues in the linear sequence. Caused by hydrogen bonds between the peptide backbone carbonyl: n-h groups. Overall 3d shape, side chain (r) interactions.
