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