Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 438

Introductory Biochemistry

Spring 2010

Lecture Notes: 12 February

© R. Paselk 2006


Peptide Titration-Review peptide structure and titration curves on your own. The simple titration curve below can serve as a model, but note that amino acids and peptides will have AT LEAST two titrations with two buffer regions et. Note also the differences in the amino- and carboxy- terminii pKas between free amino acids and terminal amino acid residues in peptides.

labeled titration

3-D Structure of Proteins 2

Review Structures from last time...

Last time looked at what is possible given the bond angles etc. between amino acid residues. Now can look at specific structures.

Tertiary structure (3°): the steric relations of residues distant in the primary sequence; the overall folding pattern of a single covalently linked molecule. (Characteristic bond type: hydrophobic; others: hydrogen, ion-pair, van der Waals, disulfide.)

Secondary and Super Secondary Examples

Alpha helix: (Figure 4.10, pg 90 of your text) [overhead 2.31 S, 5.15 P] The most frequent secondary structure is the right-handed alpha-helix.

Beta Strand: (Figure 4.15, pg 93 of your text) [overhead 5.19 P] The next secondary structural element is the beta-strand, which is seen in the supersecondary structures called parallel and anti-parallel beta sheets [overheads 7.16 & 17 V&V].

Aside: Fibrous proteins:

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Last modified 14 February 2010