Students:

Carmen Breazu, Univ. of Craiova, Romania

Bogdan Guster, Univ. of Bucharest, Romania

Horia Pasca, Univ. Babes-Bolyai, Cluj-Napoca, Romania

Simina Rebegea, Univ. A.I.Cuza, Jassy, Romania

Sabina Simon, Univ. of Bucharest, Romania

Claudia Teodorescu-Soare, Univ. A.I. Cuza, Jassy, Romania

Project Coordinator: Dr. A.I. Kuklin

JINR Summer Student Practice, 13 – 29 July 2011, Dubna

Small Angle Neutron Scattering is a method used to investigate the properties of different materials by scattered neutrons at small angles.

Some methods of investigation, like Small Angle X-ray Scattering (SAXS) or Scanning Electron Microscopy, are limited in providing information about structure of matter.

The advantages that SANS presents, due to the neutrons’ properties are:◦ Contrast variation method◦ Interaction with nuclei◦ Deep penetration

In a SANS experiment, the differential scattering cross section (dΣ/dΩ) is measured as a function of the momentum transfer:

- λ is the neutron wavelength- θ is the scattering angle between the direction of the transmitted and scattered beams

The dimension of a probe is D = 2π/Q The range of Q (scattering vector) is 0.001÷1 Å-1

2/sin4Q

BIOLOGY:

- proteins

- viruses

- lipid aggregates

- emulsificators

CHEMISTRY:- polymers- precipitates- surfactants- colloids- gels

Materials science:- alloys- glasses- composites- porous systems- grained materials - ceramics- powders

Sizes, spatial correlations and shapes of particles, agglomerates, pores and fractals in crystalline and in amorphous states as well as in solution on a length scale ranging from 1 nm up to several hundred nanometers

Phase transitions

Degree of polydispersity

Aggregation numbers

Molecular weight

Geometric peculiarities

1. Two reflectors2. Zone of reactor with moderator3. Chopper4. First collimator5. Vacuum tube6. Second collimator7. Thermostat8. Samples table9. Goniometer10-11. Vn-standard12. Ring-wire detector13. Position-sensitive detector "Volga”14. Direct beam detector.

YuMO SANS InstrumentFrank Laboratory of Neutron Physics

Verifying the spherical shell-like structure of apoferritin with SANS method of investigation

Determine the parameters of the structure:◦ Radius of gyration◦ Inner and outer radii

Use of different programs (Fitter, “Primus” from ATSAS pocket of programs, Origin) in order to compare the results

ATSAS pocket of programs:◦ Primus: performs the manipulations with experimental small-angle scattering data

files such as: averaging, subtraction, merging, extrapolation to zero concentration and curve fitting and evaluates the integral parameters from Guinier and Porod plots such as radius of gyration (for globular, flat and rod-type particles), Porod's volume, zero intensity and molecular weight

◦ Gnom: is an indirect transform program for small-angle scattering data processing. It reads in one-dimensional scattering curves (possibly smeared with instrumental distortions) and evaluates the particle distance distribution function P(r) (for monodisperse systems) or the size distribution function D(R) (for polydisperse systems

FITTER 1.0.1

ORIGIN 8.0

Guinier approximation for a globular particle:

Distribution function obtainedwith GNOM

19.12.47 gR Å

63.51

83.683.543

62.10022

th

g

g

R

R

Rtg

tg

Å

Å

Model: SANS Spherical shellR1 =60.70± 0.78R2 =36.60 ±1.15

ÅÅ

22

321

31

232

31 )]()([)()( qRRqRRRRqI

2

3

cossin9)(

2

t

tttt

qRt

From the experimental data gathered from the YuMO SANS Instrument we obtained the experimental curves;

Using Primus and Origin we determined the radius of gyration from the apoferritin and compared them, obtaining similar results;

Successfully modeled the experimental plot with Fitter, thus obtaining the inner and outer radii for our sample;

The overlap between analytical function and experimental fit shows us that the values of radii determined are correct

Apoferritin has a spherical shell-like structure

L.A. Feigin, D I. Svergun, Structure Analysis by X-Ray and Neutron Scattering

Roger Pynn, Neutron Scattering: A Primer A.G. Soloviev, A.V. Stadnik, A.H. Islamov, A.I. Kuklin, Fitter. The package

for fitting a chosen theoretical multi-parameter function through a set of data points. application to experimental data of the YuMO spectrometer

M. Balasoiu, M.L. Craus, J. Plestil, V. Haramus, R. Erhan, M. Lozovan, A.I. Kuklin, I. Bica, Microstructure of magnetite doped elastomers investigated by SAXS and SANS

P.V. Konarev, V.V. Volkov, A.V. Sokolova, M.H.J. Koch and D. I. Svergun (2003). PRIMUS - a Windows-PC based system for small-angle scattering data analysis. J Appl Cryst. 36, 1277-1282

http://flnp.jinr.ru/135/ http://flnp.jinr.ru/476/

The group would like to thank the members of the Frank Laboratory of Nuclear Physics and the YuMO SANS team for all their support and especially our supervisor Dr. A.I.KUKLIN and PhD. students L. ANGHEL and R. ERHAN for their guidance and patience.

Thanks to Prof. Dr. Gh. ADAM and Dr. S. ADAM for their good advices during the Summer Practice.

We would also like to extend our regards to the organizer of the Summer Student Practice and all members of the JINR involved with this project.