!"#$$%&'%(

)*+,*,-".

/

#

0")

) -.

11

))2

#

#(3

""%

2222

3333

4444

5555

6666 1111

Proline, is a 5-membered secondary amine

)#

#

1

1!

1

%

!""

2##

2$#

4%%

&'(

''

))

**(

+*

,*

5--

'

4%%

0

$%"%-'.#%

#

%%

))

**(

63

1!

1

%

2$#

+*

,*

&'(

7

'8)

1 )#$$%

92""% )

-')

/.

#"" -$%%./

*&,

9:"

:"

#);

#$$%

-COOH group of alanine (pKa 2.35)-COOH group of aspartic acid (pKa 3.86)-COOH group of glutamic acid (pKa 4.07)

9"'

pKa ofpKa of

valine 2.29 9.72tryptophan 2.38 9.39

9.102.09threonineserine 2.21 9.15

10.602.00prolinephenylalanine 2.58 9.24

9.212.28methionine9.742.33leucine

isoleucine 2.32 9.76glycine 2.35 9.78

9.132.17glutamine8.802.02asparagine9.872.35alanine

Nonpolar &polar side chains NH3

+COOH

9"=9#

pKa ofpKa ofpKa of

10.079.112.20tyros ine

lys ine 2.18 8.95 10.536.109.181.77histid ine

glutamic acid 2.10 9.47 4.078.0010.252.05cysteine

aspartic acid 2.10 9.82 3.86

arginine 2.01 9.04 12.48

Side Chain

AcidicSide Chains NH3

+COOH

pKa ofpKa ofpKa of Side Chain

BasicSide Chains NH3

+COOH

carboxylcarboxylsufhydrylphenolic

guanidinoimidazole1 amino

SideChainGroup

SideChainGroup

11

&

)

CRNHNH2

+

NH2C

NH2+

NH2

RNH

CRNNH2

NH2

NH2CRNH

NH2

H3 O+

H2 O

+

:

: :

:

::

::

+

pKa = 12.48

!&1&

N

NH

H

COO-NH3

+ N

NH

H

COO-NH3

+

H2O

H3O+

HCOO-

NH3+N

NH3O+

Not a part of the aromatic sextet;the proton acceptor pKa 6.10+

+

+

'"7

-1"""5"2"!"4.

1

/

7

-"".

"/

= %

"7-""#""1.

= %>">&)

# >&)>

=1 )"%

)7-2"%".

% ;-.>-?(+"

8(+.

')7-"1.

1=-&.

#)-4"#"4"?

(@

!!"")

!"")

!

%)3

"!

+H3N CH C

H

OH

O

+H3N CH C

H

O-

O

H2N CH C

H

O-

O

pH increases

pKa2.35 9.78

pI[A+] = [C-]

A+ B C-

!

pI = 12 ( pKa COOH + pKa NH3+)

= 21 (2.35 + 9.78) = 6.06

'$%

9A

#$(%B:A#$(B

#$(%'%+

!?

9A

'%+B:A'%(B

#$( '%(

!-.

6.115.415.656.066.046.045.745.916.305.685.605.886.00

pKa ofpKa ofpKa ofpI

----

----

----

----

----

----

----

----

----

----

----

----

----

valine 2.29 9.72tryptophan 2.38 9.39

9.102.09threonineserine 2.21 9.15

10.602.00prolinephenylalanine 2.58 9.24

9.212.28methionine9.742.33leucine

isoleucine 2.32 9.76glycine 2.35 9.78

9.132.17glutamine8.802.02asparagine9.872.35alanine

Side Chain

Nonpolar &polar side chains NH3

+COOH

!%!

!)

(C

!

NH2

CH

C

H2C

O-

O

C-O

O

pKa 2.10 3.86 9.82A+ B C- D2-

" ./01203456

78.78

789 2

'9&

;6;(A+BA#BE

B+A2+ C D-

pI = (9.04+12.48)/2 =10.76[B+] = [D-]; [A2+] about 0

!-.

10.76

2.98

5.023.08

7.649.74

5.63

pKa ofpKa ofpKa ofpI

10.079.112.20tyrosine

lysine 2.18 8.95 10.536.109.181.77histidine

glutamic acid 2.10 9.47 4.078.0010.252.05cysteine

aspartic acid 2.10 9.82 3.86

argin ine 2.01 9.04 12.48

Side Chain

AcidicSide Chains NH3

+COOH

pKa ofpKa ofpKa ofpI

Side Chain

BasicSide Chains NH3

+COOH

F

))!

=

!

E

F

)

4)

4

"

)/)

G5

(H3

(H3

(D3

(63(6I

J

F(3

%&C(3

H

F

4

-/.

"))

NH3 +

COO-NH

H2N

O

NH3 +

COO-H3N

HO O CH2 CHCOO-

NH3 +

I I

I I

NH3 +-O

O

CitrullineOrnithine

Thyroxine, T 4 4-Aminobutanoic acid(-Aminobutyric acid, GABA)

+

Metabolite Metabolite

Hormoneneurotransmitter

G

(:

(:

/

K

L

K

I

7) ;

7/'%

II

#77"

#)

)/

I@

F& 7

F&)&2 .

ID

F&

IJ

F&

F&