Lomonosov Moscow State UniversityPhysics Department

SPECIFIC INTERACTION OF ALBUMIN

MOLECULES IN WATER SOLUTION,

CONTAINING SILICON NANOPARTICLES

AT DIFFERENT NET CHARGE OF PROTEIN

Ksenia A. Anenkova, Galina P. Petrova,Lubov A. Osminkina, Konstantin P. Tamarov.

Bovine Serum Albumin (BSA) Mesoporous Silicon

nanoparticles (MP-Si nanoparticles)

Molecular weight – 65 kDa

Characteristic sizes – 4*4*14 nm

Isoelectric point pH 4.9

Albumin molecules realize transport

function and maintenance of colloid-

osmotic pressure in blood.

Owing to their biological compatibility

with living tissues and ability of fast

removal from the organism, the silicon

nanoparticles may be used as

photosensitisers in photodynamic therapy

of cancer and as drug delivery systems.

Experimental setup

Fig.1. Autocorrelation function of

scattered light

g(1)(t) is first order field correlation function, g(2)(t) is second order intensity auto-correlation function, accumulated by correlator during the experiment

Fundamental formula:

In case of a poly-dispersed solution :

Main parameters: laser’s wavelength 647nm, power P=25mW

Fig.2. pH dependence of the scattering centers translation

diffusion coefficient in BSA water solution

B=V 1M 22 ( Z 24m3

+β222

−β232 m3

4+ 2β33m3 ) D t=D0 {1+ (2BM− [η ] ) c }

According to Scatchar theory nonlinear character of dependence at fig.1 is described by next formula where B is the second virial coefficien in the expansion for free energy, known as coefficient of intermolecular interaction

Fig.3. pH dependence of the scattering centers translation

diffusion coefficient in mesoporous silicon nanoparticles water

solution

Mesoporous silicon nanoparticles are hydrophilic. Due to this property a

water shell is formed around them. This leads to a partial shielding of particles

net charge. Therefore, the shape of dependence at fig.3 is more smooth.

Fig.4. pH dependence of the scattering centers translation diffusion

coefficient in mesoporous silicon nanoparticles + BSA water solution

Images of MP-Si nanoparticles, obtained by TEM

In water solution MP-Si nanoparticles

exist as clusters with sizes ranging from

100 nm to 1 mm.

Ultrasonic treatment, followed by

filtration, allows us to select the desired

particles size.

136.42нм

tD

kTR

6

Comparison of the results obtained

by dynamic light scattering with TEM

136.42нм

1

2

3

IR spectrometer Bruker IFS 66v/S

IR spectroscopy is widely used to determine the composition of porous silicon layers.

Technical

characteristics:

Scanning range:

7500 – 370 сm-1

Resolution: 0.25 сm-1

Evacuating the

measuring chamber to 3

mbar

Fig.5. IR transmission spectrum for Mp-Si nanoparticles

in the range from 800 to 2500 сm-1

• SiH3 antisymmetric deformation vibrations 877сm-1

• SiO stretching vibrations in Si-O-Si 1064сm-1

• SiH stretching vibrations in O3-SiH 2266сm-1

•Amide-I (С=O stretching vibrations ) 1650 cm-1

•Amide-II (CN stretching vibrations and NH deformational vibrations) 1520 cm -1

•COO- 1390 cm-1

•Amide-III (CN stretching vibrations and NH rotating) 1220-1330 cm-1

Fig.6. IR transmission spectrum for BSA in the range from 800 to 2000 сm -1

What are we looking for in the IR-spectrum BSA+MP-Si nanoparticles?

Fig.7. IR transmission spectra for BSA and BSA+lead acetate in the range from 800 to 2000 сm-1

We are looking for amide-I and amide-II bands frequencies shifts. This shifts detect

secondary structural changes caused by interaction of nanoparticles and protein.

The examples of such shifts for system BSA+ lead acetate are shown at fig.7 For this

system is well known that there is an interaction between BSA macromolecules and

lead acetate.

Fig.8. IR transmission spectrum for BSA+Mp-Si nanoparticles in the range

from 800 to 1800 сm-1

There is no any shifts of amide-I or amide-II bands in BSA+MP-Si nanoparticles system

compared to pure protein. So it means that there is no interaction in this system.

Hydrophilic properties of MP-Si nanoparticles can explain the absence of interaction

between the nanoparticles’ surface OH groups and CO groups of BSA

The absence of OH- CO groups interaction also can be explained by unsufficient for stable

bond amount of H on the surface of particles

Conclusions:

• The investigation of molecular parameters of serum albumin in water

solution by DLS method has shown that the addition of nanoparticles

does not change the mobility of the scattering particles within the

experimental error.

• In the obtained IR spectra is not observed shift to short wave area,

characteristic for the formation of hydrogen bonds between the

carbonyl groups of the protein and the OH groups on the silicon

nanoparticles surface (shoulder 1650 for C = O stretching vibrations)

• Present results show that there is no interaction between albumin

molecules and silicon nanoparticles in the investigated systems.

Thank you for your attention!If you have any questions, I will gladly answer them by e-mail

ksensanna@gmail.com