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Chapter Three-
8 Dimensional
Structures of
Proteins
1 Secondary Structure have rather similar characteristics, a kind of homogeneous
A. The Peptide Group “average” of their randomly dangling side chains. How-
B. Helical Structures ever, the three-dimensional structure of a native (physio-
C. Beta Structures logically folded) protein is specified by its primary struc-
D. Nonrepetitive Structures ture, so that it has a unique set of characteristics.
2 Fibrous Proteins In this chapter, we shall discuss the structural features
␣
A. Keratin—A Helix of Helices of proteins, the forces that hold them together, and their
B. Collagen—A Triple Helical Cable anization to plex structures. This
3 Globular Proteins will form the basis for understanding the structure–func-
A. Interpretation of Protein X-Ray and NMR tion relationships necessary prehend the biochemi-
Structures
cal roles of proteins. Detailed consideration of the dynamic
B. Tertiary Structure
behavior of proteins and how they fold to their native
C. Structural Bioinformatics
structures is deferred until Chapter 9.
4 Protein Stability
A. Electrostatic Forces
B. Hydrogen Bonding Forces
C. Hydrophobic Forces 1 SECONDARY STRUCTURE
D. Disulfide Bonds A polymer’s secondary structure (2؇ structure) is defined
E. Protein Denaturation as the local conformation of its backbone. For proteins,
F. Explaining the Stability of Themostable Proteins this e to mean the specification of regular polypep-
5 Quaternary Structure tide backbone folding patterns: helices, pleated sheets, and
A. Subunit Interactions turns. However, before we begin our discussion of these
B. Symmetry in Proteins basic structural motifs, let us consider the geometrical
C. Determination of position
properties of the peptide group because its understanding
Appendix: Viewing Stereo Pictures
is prerequisite to that of any s