Structure of Peptides

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Structure of Peptides and their Assembly
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Protein Hierarchy
primary structure chemistry of backbone order
of amino acids
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secondary structure local 3 dimensional
structure / conformation
a-helix
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tertiary structure 3D structure of a folded
protein
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quarternary structure assembly of multiple
folded proteins into a multi-subunit complex
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Primary Structure Backbone
F
Y
trans is favored by about 10001 over cis
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Primary Structure Chirality
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Primary Structure Side Chains
20 natural side chains with a variety of
chemistries creates a huge diversity of
molecules by combining the side chains in any
order along the polymer backbone a peptide of
100 amino acids could be made in more
combinations (20100) than there are atoms in the
universe.
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Primary Structure Side Chains
WTrpTryptophan
FPhePhenylalanine
AAlaAlanine
VValValine
IIleIsoleucine
LLeuLeucine
MMetMethionine
hydrophobic
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Primary Structure Side Chains
QGlnGlutamine
TThrThreonine
SSerSerine
NAsnAsparagine
YTyrTyrosine
hydrophilic
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Primary Structure Side Chains
KLysLysine
DAspAspartic Acid
RArgArganine
EGluGlutamic Acid
charged
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Primary Structure pKas
Arg 12.0 Positive Below pH 12.0 Lys 10.4-11.1 P
ositive Below pH 10.4 N-term 6.8-8.0 Positive
Below pH 6.8 His 6.0-7.0 Positive Below pH
6.0 Tyr 10.0-10.3 Negative Above pH
10.3 Cys 9.0-9.5 Negative Above pH 9.5
Glu 4.3-4.5 Negative Above pH
4.5 C-term 3.5-4.3 Negative Above pH
4.3 Asp 3.9-4.0 Negative Above pH 4.0
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Primary Structure Special Side Chains
GGlyGlycine
PProProline
CCysCysteine
HHisHistidine
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