What is SAXS method?
Small-angle X-ray scattering (SAXS) is an analytical technique that measures the intensities of X-rays scattered by a sample as a function of the scattering angle. Measurements are made at very small angles, typically in the range of 0.1 deg to 5 deg.
What information can be obtained from SAXS?
Abstract. Small-angle X-ray scattering (SAXS) is a biophysical method to study the overall shape and structural transitions of biological macromolecules in solution. SAXS provides low resolution information on the shape, conformation and assembly state of proteins, nucleic acids and various macromolecular complexes.
What is Q in Xray scattering?
The scattered intensity I(q) is the Fourier Transform of g(r), the correlation function of the electronic density r(r), which corresponds to the probability to find a scatterer at position r in the sample if another scatterer is located at position 0 : elastic x-ray scattering experiments reveal the spatial …
What is Q range in SAXS?
SAXS technique consist of measuring the scattered intensity of an X-ray beam as a function of the scattering vector q = (4π/λ sin θ), where λ is the wavelength of the radiation and θ is one half of the scattering angle. The scattered intensity in a nanocomposite can be expressed as: (17.2)
What is a Kratky plot?
A Kratky plot is a plot of q2I(q) vs. q. Kratky plots can qualitatively assess the flexibility and/or degree of unfolding in samples. Unfolded (highly flexible) proteins should have a plateau in the Kratky plot at high q, while compact, globular proteins will have a bell-shaped (Gaussian) peak.
What is the difference between WAXS and SAXS?
WAXS usually covers angular 5-60 degree. For SAXS, it covers much smaller angle, which is up to 1 degree. When X-rays are directed at the solids, they are scattered in some certain patterns depend on the internal structure of the material.
What is Guinier analysis?
Guinier analysis allows model-free determination of the radius of gyration (Rg) of a biomolecule from X-ray or neutron scattering data, in the limit of very small scattering angles.
What is porod volume?
The ratio of I(0) to Q determines the volume of the scattering particle sometimes known as the Porod volume, VP. Application of the Porod-Debye law determines the surface area, S, of the scattering particle that is scaled by concentration and Δρ that can be normalized using Q.
What does Q mean in SAXS?
SAXS technique consist of measuring the scattered intensity of an X-ray beam as a function of the scattering vector q = (4π/λ sin θ), where λ is the wavelength of the radiation and θ is one half of the scattering angle.
What is radius of gyration in SAXS?
The radius of gyration for a molecule, which is a measure of the spread of its mass, can be estimated from the lowest scattering angles of SAXS data. This estimation method requires specification of a window of scattering angles.
What is Guinier regime?
1 Guinier Regime. The Guinier approximation, applied to particles randomly oriented under the limit of QR ≪ 1, allows one to estimate the radius of gyration RG by means of the definition of the scattered intensity as follows: (61) with RG being. (62)
What is a porod plot?
Porod plots pull out high-Q features on a linear scale. Guinier plots can be used to extract the radiation of gyration. Kratke plots can help distinguish between extended and compact conformations of chains such as proteins.