chapter05

chapter05 - BCH 4053Summer 2001Chapter 5 Lecture Notes...

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Chapter 5, page 1 BCH 4053—Summer 2001—Chapter 5 Lecture Notes Slide 1 Chapter 5 Proteins: Biological Function And Primary Structure Slide 2 Polypeptides • Proteins are linear polymers of Amino Acids (See Figure 5.1) • Each amino acid is a “residue” • 2 residues = dipeptide • 3 residues = tripeptide 12-20 residues = oligopeptide • Many residues = polypeptide • Each polypeptide has an amino terminal and a carboxy terminal amino acid (though it may be chemically “blocked”) Insulin, with 51 amino acids, and a MW of 5,733 represents about the lower limit of what we would call a “protein” as compared with a “polypeptide”. Glutamine Synthetase, at 600,000 MW is a relatively large protein, but still not one of the largest. Slide 3 Geometry of Peptide Bond • Trans configuration (Figure 5.2) • Length = 0.133 nm, between double and single bond • Double bond “character” (Figure 5.3) • Six atoms of the peptide bond are coplanar
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Chapter 5, page 2 Slide 4 Size of Proteins • Proteins may consist of one or more polypeptide chains • Multimeric • Homomultimer • Heteromultimer (Cf Hemoglobin) • Size range is enormous (Table 5.1) • 51 residues (5733 MW) for insulin • 468 residues (600,00 MW) for glutamine synthetase Multimeric proteins have more than one polypeptide chain. If the chains are identical, it would be homomultimer . If the chains were different, it would be a heteromultimer . Hemoglobin is an example of a heteromultimer having two alpha and two beta chains making up a tetrameric structure. Slide 5 Levels of protein structure • Primary structure (sequence) • Secondary structure (ordered regular structures along peptide bond—Figure 5.8) • Difference between conformation and configuration (Figure5.11) • Tertiary structure (overall 3 dimensional structure) • Quaternary structure (subunit organization) • See Figure 5.10—Hemoglobin—for example Slide 6 Amino Acid Analysis of Proteins • Hydrolysis in 6 N HCl at 110 o C • Correct for destruction of serine, threonine • Correct for slow hydrolysis of hydrophobic amino acids • Asn and Gln are hydrolyzed, therefore compositon reported as Asx and Glx • Chromatographic analysis of amino acids (ion exchange or HPLC—See Fig. 4.21 and 4.22)
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Chapter 5, page 3 Slide 7 Primary Structure—Sequence • Unique to each protein (Figure 5.6) • Determines overall structure and function • Encoded by nucleotide sequence in DNA • Possible variations are essentially infinite Slide 8 Illustration of infinite number of sequence variations • Small polypeptide, 100 residues • Possible sequences = 20 100 = 10 130 One molecule of each possible sequence would occupy a volume of 13 04 23 11 0 107 1 mol e gram s 1 mL 1 0 molecules x x 1 0 x 6 x 1 0 molecule s mol e 1.2 grams 1.4 x 1 0 mL or 1.4 x 1 0 L, which is much larger than volume of the known universe = Slide 9 Shape of Proteins • Three general types of shapes (Figure 5.7) • Fibrous proteins • Globular proteins
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This note was uploaded on 05/22/2011 for the course BCH 4053 taught by Professor Logan during the Fall '06 term at FSU.

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chapter05 - BCH 4053Summer 2001Chapter 5 Lecture Notes...

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