http://www.biology.arizona.edu/cell_bio/problem_sets/membranes/fluid_mosaic_model.html http://pubs.rsc.org/en/content/articlehtml/2009/an/b818484d

vesicle micelle bilayer
http://biowiki.ucdavis.edu/Biochemistry/Lipids/Dynamics_of_Membrane_Lipids/Lipid_Conformational_Transitions

http://www.cell.com/cms/attachment/581128/4373622/gr1b3.jpg

gel fluid 
http://journal.frontiersin.org/article/10.3389/fimmu.2013.00143/full

Gramicidin A from Bacillus brevis

• Antimicrobial peptide that forms dimeric pores and leaks ions

• Extremely hydrophobic, helical structure

• Around 2.2 nm long

DMPC 

• 14 C tail

• Transition temp: 24 ̊C

DSPC 

• 18 C tail

• Transition temp: 55  ̊C

DOI: 10.1098/rsif.2009.0443 Lundbaek et al. J. R. Soc. Interface, 2010
105

196

367

0

100

200

300

400

0 100 200 300 400 500

Measured Diameter (nm)

Filter Pore Size (nm)

Vesicle Size of DMPC
http://www.antonpaar.com/fileadmin/images/products/benchto

p/density_and_sound_velocity_meter_dsa_5000_m/dsa_5000_

m.jpg

Characteristic 

frequency of air

Characteristic 

frequency of water
1.001

1.002

1.003

1.004

1.005

0 10 20 30 40 50 60

Specific Gravity

Temperature ( ̊c) 

DMPC and Gramicidin Densities

DMPC

Shift: +0.003
5 10 15 20 25 30 35 40 45

-0.0004

-0.0003

-0.0002

-0.0001

0.0000

Derivative SG

Temperature (oC)

http://biowiki.ucdavis.edu/Biochemistry/Lipids/Dynamics_of_Membrane_Lipids/Li

pid_Conformational_Transitions

Melting transition: 

23.955 ̊C 

Width of melting 

transition: 

1.281 ̊C • Identify melting transition 

temperature with 1st

derivative

• Measure width of melting 

transition with full width half 

max

Determining Melting Temperature

gel fluid 
1.001

1.002

1.003

1.004

1.005

0 10 20 30 40 50 60

Specific Gravity

Temperature ( ̊c) 

DMPC and Gramicidin Densities

DMPC

Shift: +0.003

DMPC+0.1%Gramicidin 

Shift: +0.002

Width of melting 

transition: 

No peptide: 1.281 ̊C

0.1%Gramicidin: 1.453  ̊C
1.001

1.002

1.003

1.004

1.005

0 10 20 30 40 50 60

Specific Gravity

Temperature ( ̊c) 

DMPC and Gramicidin Densities

DMPC

Shift: +0.003

DMPC+0.1%Gramicidin 

Shift: +0.002

DMPC+1% Gramicidin 

Shift: +0.001

Width of melting 

transition: 

No peptide: 1.281 ̊C

0.1%Gramicidin: 1.453  ̊C

1%Gramicidin: 2.124  ̊C
1.001

1.002

1.003

1.004

1.005

0 10 20 30 40 50 60

Specific Gravity

Temperature ( ̊c) 

DMPC and Gramicidin Densities

DMPC

Shift: +0.003

DMPC+0.1%Gramicidin 

Shift: +0.002

DMPC+1% Gramicidin 

Shift: +0.001

DMPC+10% Gramicidin 
1

1.0005

1.001

1.0015

1.002

1.0025

1.003

1.0035

30 35 40 45 50 55 60 65 70

Specific Gravity

Temperature ( ̊C)

DSPC and Gramicidin Densities

DSPC+Water

Shift: + 0.002
1

1.0005

1.001

1.0015

1.002

1.0025

1.003

1.0035

30 35 40 45 50 55 60 65 70

Specific Gravity

Temperature ( ̊C)

DSPC and Gramicidin Densities

DSPC+Water

Shift: + 0.002

DSPC+1% Gramicidin 

Shift: +0.001
1

1.0005

1.001

1.0015

1.002

1.0025

1.003

1.0035

30 35 40 45 50 55 60 65 70

Specific Gravity

Temperature ( ̊C)

DSPC and Gramicidin Densities

DSPC+Water

Shift: + 0.002

DSPC+1% Gramicidin 

Shift: +0.001

DSPC+10% Gramicidin

Width: 0.672 ̊C

Width: 1.156 ̊C

Width: 3.736 ̊C
1.0002

1.0005

1.0008

1.0011

1.0014

0 10 20 30 40 50 60 70

Specific Gravity

Temperature ( ̊C)

Density of DMPC+DSPC Mixture

Gel phase 

Gel+fluid

phase 

Fluid phase 

http://dbpdra1nk4ncl.cloudfront.net/content/ppebio/57/1/F5.large.jpg
0.E+00

5.E-05

1.E-04

15 20 25 30 35 40 45 50 55 60

dV

/dT

T (°C)

Derivative of DMPC + DSPC

To fluid phase

To gel + fluid phase
1.0004

1.0006

1.0008

1.001

1.0012

1.0014

1.0016

1.0018

1.002

0 10 20 30 40 50 60 70

Specific Gravity

Temperature

Density of DMPC + DSPC + 1% Gramicidin

DMPC + DSPC + 1% Gramicidin: 7.799 ̊C

DMPC + DSPC: 11.001 ̊C

(°C)