biochemistry · lehninger principles of biochemistry, fifth edition 2008 w. h. freeman and company...
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Biochemistry
Lecture 4 Amino Acids & Proteins
Proteins
Lipids
Enzymes
Amino Acids
R Groups
Additional Amino Acids
4-hydroxyproline
5-hydroxylysine
Amino Acids Are Amphoteric
9
Concentrations of Charged Species as a Function of pH
12
Peptides
pI and pH Affect Overall Surface Charge
17
pKa Values Depend on Local Electrostatic Environment
18
pKa = 4.2
pKa > 4.2 pKa < 4.2
oxytocin
vasopressin
Cys
Tyr
Phe Gln
Asn
Cys
SS
H2NO
NH2CGlyArgPro
Cys
Tyr
Ile Gln
Asn
Cys
SS
H2NO
NH2CGlyLeuPro
CH C NH CCH OH
O O
CH 2
OO
HH
NHCCHNHCCHNH
O
HO
NH2
C
Tyr–Gly–Gly–Phe–Met Methionine enkephalin
CH2CHCH3
CH3Morphine
O
N
HO OH
CH3
H
H
Tyr–Gly–Gly–Phe–Leu Leucine enkephalin
Enkephalins
Bovine Insulin
Proteins
Proteins
Structure of Proteins
Sequence Varies: Ask 23andMe
Alpha Helices
Beta Strands
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