Journal: Nat Protoc / Year: 2016 Title: Preparing monodisperse macromolecular samples for successful biological small-angle X-ray and neutron-scattering experiments. Authors: Cy M Jeffries / Melissa A Graewert / Clément E Blanchet / David B Langley / Andrew E Whitten / Dmitri I Svergun / Abstract: Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) are techniques used to extract structural parameters and determine the overall structures and shapes of biological ...Small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) are techniques used to extract structural parameters and determine the overall structures and shapes of biological macromolecules, complexes and assemblies in solution. The scattering intensities measured from a sample contain contributions from all atoms within the illuminated sample volume, including the solvent and buffer components, as well as the macromolecules of interest. To obtain structural information, it is essential to prepare an exactly matched solvent blank so that background scattering contributions can be accurately subtracted from the sample scattering to obtain the net scattering from the macromolecules in the sample. In addition, sample heterogeneity caused by contaminants, aggregates, mismatched solvents, radiation damage or other factors can severely influence and complicate data analysis, so it is essential that the samples be pure and monodisperse for the duration of the experiment. This protocol outlines the basic physics of SAXS and SANS, and it reveals how the underlying conceptual principles of the techniques ultimately 'translate' into practical laboratory guidance for the production of samples of sufficiently high quality for scattering experiments. The procedure describes how to prepare and characterize protein and nucleic acid samples for both SAXS and SANS using gel electrophoresis, size-exclusion chromatography (SEC) and light scattering. Also included are procedures that are specific to X-rays (in-line SEC-SAXS) and neutrons, specifically preparing samples for contrast matching or variation experiments and deuterium labeling of proteins.
Instrument name: PETRA III EMBL P12 / City: Hamburg / 国: Germany / Type of source: X-ray synchrotronSynchrotron / Wavelength: 0.12 Å / Dist. spec. to detc.: 3.1 mm
Detector
Name: Pilatus 2M
Scan
Title: Bovine serum albumin, monomer / Measurement date: Jan 23, 2014 / Storage temperature: 20 °C / Exposure time: 1 sec. / Number of frames: 3500 / Unit: 1/nm /
Min
Max
Q
0.0858
4.2301
Distance distribution function P(R)
Sofotware P(R): GNOM 4.6 / Number of points: 395 /
Min
Max
Q
0.08448
4.233
P(R) point
24
418
R
0
8.23
Result
Type of curve: other /
Experimental
Porod
MW
66.7 kDa
62.6 kDa
Volume
-
100.2 nm3
P(R)
P(R) error
Guinier
Guinier error
Forward scattering, I0
559
0.9
555
1.26
Radius of gyration, Rg
2.8 nm
-
2.77 nm
-
Min
Max
D
-
8.23
Guinier point
1
146
+
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