The fluorescence in analysis of a micelle formation

Created by: Jiří Běťák

The aim of a lecture

- can we describe a process of micellization in the solution of a biopolymer ?

Explain: How …

- can we use a method of Fluorescence sprectroscopy ?

- can we define the Critical micelle concentration ?

Vocabulary lesson

Probe - sonda

highlight - zvýraznit

visualise- zviditelnit

increase - zvýšení

attache - navázat

radiation - záření

associate – sdružovat se

tend to – mít tendenci

influence - ovlivňovat

volume - objem

surface - povrch

decrease - snížení

The principle of fluorescence

Jablonski diagram

The fluorescent probes

Fluorescent probes are used to visualize investigated molecules that do not emit any visible radiation. The

fluorescent probe is attached on a molecules and highlight them.

Examples of probes:

Pyrene

Perylene

Antraquinone

Characteristics of Perylene

Absorption Emission

Excitation wavelength: 440 nm

Emission wavelength: 450 nm

Fluorescence intensity of perylen

The more polar system, the lower intenzity.

Dependence of the intensity on the polarity

1,62

1,64

1,66

1,68

1,7

1,72

0 5 10 15 20 25

Relatative permitivity of the solution

Inte

ns

ity

Increace of polarity = decrease of intenzity

Process of micellization

In the solution particles of a biopolymer consisting of polar and non-polar sides tend to associate influenced by electrostatics interactions.

At first they tend to create a monomolecular layer on a surface. When the surface is fully saturated the new particles

start to associate into a micelles.

The concentration of a biopolymer that fully saturates the surface is called Critical micelle concentration CMC

Micellization process of biopolymers

Polar

Non-polar

Particles of a bipolymer – lipides, fatty acids, etc.

Non-polar Polar

CMC

Probe

A micelle marking

Fluorescent probes that are added into the solution of agregating molecules are freely dispersed in the volume.

Their intensity of fluorescence is constant.

When the concentration of a biopolymer reaches the CMC, it starts to create a micelles. The probe is electrostatically

attracted to the non-polar center of a micelle.

The fluorescent probe looses its emitting intensity.

Fluorescence intensity change

0

5

10

15

20

25

30

0 50 100 150 200

concentration (mol.dm-3)

Inte

nsity

The final determination of CMC

CMC

Thank You kindly for your attention

That´s the end…