Textbook Notes (290,000)
CA (170,000)
UTSG (10,000)
BIO (600)
BIO130H1 (100)
Chapter 2

BIO130H1 Chapter Notes - Chapter 2: Robert Corey, Linus Pauling, Turnstile


Department
Biology
Course Code
BIO130H1
Professor
Kenneth Yip
Chapter
2

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Amino Acid Basic Structure
SECONDARY STRUCTURE
HELIX
Proteins are formed by linkages among vast numbers of atoms;
consequently, their shape is complex
The term Conformation refers to the
three‐dimensional
arrangement of the atoms of a molecule
, that is, to their spatial
organization
Secondary structure describes the
conformation of portions of the
polypeptide chain
o Early studies on secondary structure were carried out by
Linus Pauling and Robert Corey of the California Institute
of Technology
By studying the structure of simple peptides consisting of a few
amino acids linked together, Pauling and Corey concluded that
polypeptide chains exist in
preferred conformations
that provide
the
maximum possible number of hydrogen bonds between
neighboring amino acids
Two conformations were proposed
In one conformation, the backbone of the polypeptide assumed
the form of a cylindrical, twisting spiral called the Alpha  Helix
o The
backbone
lies on the
inside
of the
helix
, and the side
chains project outward
The helical structure is
stabilized by hydrogen
bonds between the
atoms of one
peptide bond
and those situated
just above
and
below
it along the spiral
The X‐ray diffraction patterns of actual proteins produced during
the 1950s bore out the
existence of the  helix
, first in the protein
keratin found in hair and later in various oxygen‐binding
proteins, such as myoglobin and hemoglobin
Surfaces on opposite sides of an helix may have contrasting
properties
o In water‐soluble proteins, the outer surface of an helix
often contains polar residues in contact with the solvent,
whereas the surface facing inward typically contains
nonpolar side chains
ß SHEET
The second conformation proposed by Pauling and Corey was the
Beta ) Sheet , which consists of several segments of a
polypeptide lying side by side
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