Fast SAXS Measurements of a Diluted Protein Solution
A 1% Lysozyme solution was measured with the SAXSpace system. Structural information can be obtained already after 1 minute due to the highly intense line-collimation mode and the compact design of the SAXSpace system.
Small-Angle X-ray Scattering (SAXS) is the perfect technique to investigate proteins in solution. SAXS allows to study the behavior of proteins and protein complexes in the native state and therefore contributes to a better understanding of their biological function.
Unfortunately, most proteins are weakly scattering materials, hence obtaining high-quality SAXS data in the laboratory can only be accomplished by
- a high incident X-ray flux at the sample,
- a large illuminated sample volume increasing the scattering signal intensity of the sample,
- and a short sample-to-detector distance.
Experimental and Results
A diluted Lysozyme solution (1% in Acetate buffer) was measured with different exposure times. The scattering curves after background subtraction are shown in Figure 1.
Fig. 1 Background-subtracted scattering curves.
It is obvious that the data statistics improve upon increasing the measurement time. However, already after 1 minute the data quality of the scattering curve is good enough to calculate the Pair-Distance Distribution Function (PDDF) correctly. This function allows to determine the maximum size and to estimate the approximate shape of the protein.
As shown in Figure 2 the results after different exposure times overlap nicely. The PDDF indicates particles with a maximum dimension of 4.5 nm.
Fig. 2 Pair distance distribution functions.
The SAXSpace with its highly intense line-collimation mode is the perfect laboratory SAXS system for fast measurements of weakly scattering samples in the lab. In combination with the high-throughput autosampler (with cooling option for sensitive samples) and its powerful software it is perfectly suited for the analysis of proteins in solution.