In this case of membrane proteins the extraction process should be followed by a number of different steps:

  1. removal of unbroken cells from the cell lysate by low speed centrifugation (20 min at 10 000 g).
  2. isolation of the membrane particles from the supernatant by ultracentrifugation
    (60 min at >100 000 g).
  3. washing of the membrane particle to remove all soluble proteins.
  4. solubilization of protein from the membrane particles by a detergent.

The extent of the solubilization and the stability of the solubilized protein depend on the detergent type and concentration. It is not possible to give general rules for either of these variables and they have to be optimized experimentally. Important for the solubilization is the detergent-to-protein ratio. At low ratios (1:10) the membranes are lysed and large complexes of are formed containing protein, detergent, and membrane lipids. With progressively larger ratios smaller complexes are obtained. Finally, at ratios of 10:1 to 20:1 individual detergent-protein complexes are formed free of membrane lipids. To determine the optimal conditions it is important to vary both the detergent and the protein concentration.

Commonly used detergents and their critical micel concentrations (cmc) are listed in the table below.

Class of detergent examples cmc (mM) 
Non-ionic Triton X-100 0.30
  octylglucoside 25
Zwitterionic CHAPS 6.5
  Zwittergent 3-12 3.6
Ionic sodium deoxycholate 4 (at pH >8)

At the end of this page, you can find a list of detergents and their properties that can be used for membrane protein research (adapted/modified from "Detergents by Application - Membrane Protein Solubilization", http://www.sigmaaldrich.com/etc/controller/controller-page.html?TablePage=104861071) 

Remarks:

  • The solubility of membrane proteins is affected by the ionic strength of the solutions. Therefore, 150 mM NaCl is usually included in solubilization buffers.
  • Polyols stabilize solubilized membrane proteins. Typical glycerol concentrations range from 5-50% (v/v). High concentrations of glycerol will increase the viscosity of the preparations that can cause problems in the ultracentrifuge and on chromatographic columns.
  • The buffer concentration can affect the solubility and stability of proteins. Especially phosphate buffers are known for their solubilizing properties. Concentrations of 0.1-0.5 M phosphate buffer increase the solubility of membrane proteins. 
  • The presence of detergent will have a significant effect on subsequent chromatography steps.

For more information on membrane protein structure and function you can visit the Structural Biology Knowledge Base or directly to the list of membrane proteins with known 3D structure. where you can find links to the publications with more details on the procedures and detergents for membrane protein solubilization.

List of detergents used for membrane protein solubilization:

Name

CMC

Micellar Avg. MW

Cloud pt

Aggr. #

2-Cyclohexylethyl β-D-maltoside

120 mM

(20-25°C)

 

 

 

3-(1-Pyridinio)-1-propanesulfonate

 

 

 

 

3-(4-tert-Butyl-1-pyridinio)-1-propanesulfonate

 

 

 

 

3-(Benzyldimethylammonio)propanesulfonate

 

 

 

 

3-(Decyldimethylammonio)­propane­sulfonate inner salt zwitterionic detergent

25-40 mM

(20-25°C)

12,600

 

41

3-(N,N-Dimethylmyristylammonio)propanesulfonate

0.1-0.4 mM

(20-25°C)

30,200

 

83

3-(N,N-Dimethyloctylammonio)propanesulfonate inner salt

330 mM

(20-25°C)

 

 

 

3-(N,N-Dimethylpalmitylammonio)propanesulfonate

0.01-0.06 mM

(20-25°C)

60,700

 

155

3-[N,N-Dimethyl

(3-palmitoylaminopropyl)ammonio]-propanesulfonate

 

 

 

 

5-Cyclohexylpentyl β-D-maltoside

2.4-5 mM

(20-25°C)

32,600

 

66

6-Cyclohexylhexyl β-D-maltoside

0.56 mM

32,000

 

63

ASB-14

 

>10,000

 

≥23

ASB-C80

 

 

 

 

Brij® 58

0.08 mM

(20-25°C)

average Mn ~1124
79,000

 >100 °C

70

Brij® 35

0.09 mM

1225 (49K)

>100 °C

40

Brij® L23 main component: tricosaethylene glycol dodecyl ether

 91 μM

Est. mol wt 1198
48,000 

 >100 °C

20-40

C7BzO

 

mol wt 399.59 Da

(anhydrous)

 

≤25

Cetylpyridinium chloride

 

 

 

 

CHAPS

 

 

 

 

CHAPSO

8 mM

(20-25°C)

7000

 90 °C

11

Chenodeoxycholic acid

3

 

 

 

Cyclohexylmethyl β-D-maltoside

340

 

 

 

DDMAB

4.3

 

 

 

Decyl β-D-glucopyranoside

2.2

 

 

 

Decyl β-D-maltopyranoside

1.6 mM

(20-25°C)
1.6-1.8

 

 

 

Decyl-β-D-1-thiomaltopyranoside

0.9 mM

(20-25°C)

 

 

 

Deoxycholic acid

2-6

1200-5000

 

3-12

Digitonin

<0.5 mM

(20-25°C)

70,000

 

60

Dimethyldecylphosphine oxide

4.6 mM

(20-25°C)

28,597

 

131

Dimethylethylammoniumpropane sulfonate

 

 

 

 

Dodecyltrimethylammonium chloride

 

 

 

 

EMPIGEN® BB

1.6-2.1 mM

(20-25°C)

Mr ~279

 

 

Hexadecylpyridinium chloride monohydrate

 

 

 

 

Hexaethylene glycol monodecyl ether

 

 

 

 

IGEPAL® CA-630

0.08 mM

(20-25°C)

mol wt ~603

 63-69 °C 

 

Lutrol® OP 2000 non-ionic

 

Mw ~2000

 

 

MEGA-8

58

 

 

 

N,N-Bis[3-(D-gluconamido)propyl]deoxycholamide

1.1-1.4 mM

(20-25°C)

10,500

 

8-16

N-Decanoyl-N-methylglucamine

6-7 mM

(20-25°C)

 

 

 

n-Dodecyl β-D-glucopyranoside

0.13

 

 

 

n-Dodecyl β-D-maltoside

0.15 mM

(20-25°C)

50,000

 

98

n-Dodecyl β-D-maltoside

0.15 mM

(20-25°C)

50,000

 

98

N-Dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate

2-4 mM

(20-25°C)

18,500

 

55

n-Heptyl β-D-thioglucopyranoside

30

 

 

 

n-Hexadecyl β-D-maltoside

0.0006 mM

(20-25°C)

 

 

 

N-Lauroylsarcosine sodium salt

14.6 mM

(20-25°C)

600
600

 

2
2

N-Nonanoyl-N-methylglucamine

19-25 mM

(20-25°C)

 

 

 

N-Octanoyl-N-methylglucamine

58 mM

(20-25°C)

 

 

 

Nonaethylene glycol monododecyl ether nonionic surfactant

0.08

64,000

 

110

Octaethylene glycol monododecyl ether

0.11

66,000

 

123

Octyl β-D-1-thioglucopyranoside

9 mM

(20-25°C)

 

 

 

Octyl β-D-glucopyranoside ≥98%

(GC)

20-25 mM

(20-25°C)

25,000

 >100 °C

84

Octyl β-D-glucopyranoside solution

20-25

24500-25000

 ≥100

84

Pentaethylene glycol monododecyl ether

 

 

 

 

Sodium chenodeoxycholate ≥97%

 

 

 

 

Sodium cholate hydrate

9-15 mM

(20-25°C)

900-1300

 

2-3

Sodium deoxycholate monohydrate

2-6

1200-5000

 

3-12

Sodium dodecyl sulfate

7-10 mM

(20-25°C)

18,000

 >100 °C

62

Sodium glycodeoxycholate

 

 

 

 

Sodium taurocholate

 

 

 

 

Sodium taurodeoxycholate

1-4 mM

(20-25°C)

3100

 

6

Sucrose monodecanoate

2.5

 

 

 

Sucrose monolaurate

0.3

 

 

 

Taurocholic acid

3-11 mM

(20-25°C)

2100

 

4

Thesit® for membrane research

0.1 mM

(20-25°C)

583

 

 

Triton X-100

0.2-0.9 mM

(20-25°C)

625
80,000

 65 °C
pour point ~7 °C

100-155

TWEEN® 20

0.06 mM

(20-25°C)

mol wt ~1228

 76 °C

 

TWEEN® 40 viscous liquid

0.027

(20-25°C)

Est. mol wt 1277

 

 

TWEEN® 80

0.012 mM

(20-25°C)

1310
79,000

 65 °C

60

Undecyl β-D-maltoside

0.59 mM

(20-25°C)