Humboldt State University ® Department of Chemistry

Richard A. Paselk

Chem 431


Fall 2008

Lecture Notes: 19 September

© R. Paselk 2008


3-D Structure of Proteins 2

Secondary Structure

Alpha helix: (text Figure 4-4a, Model) The most frequent secondary structure is the right-handed greek symbol lalpha-helix.

Beta Strand: The next secondary structural element is the greek symbol beta-strand, which is seen in the supersecondary structures called parallel (text Figure 4-6b) and anti-parallel (text Figure 4-6a) beta sheets.

Aside: Fibrous proteins 2: silk, antiparallel greek symbol beta-pleated sheet (text Figure 4-13 a & b) .

Non-repetitive secondary elements: Proteins can also have non-repetitive secondary structures which consist of a few residues in a turn or loop. Among these are:

Collagen strand: This is a specialized structure occurring in only a particular family of fibrous proteins. It does not occur in globular proteins that I am aware of.

Pathway Diagrams

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Last modified 19 September 2008