Guinier analysis

The most straightforward application of SAXS is in the determination of the radius of gyration, Rg, of the molecule of interest. This may be estimated from Guinier analysis of the low q data and is a model-free result obtained from the Guinier approximation, valid at low q ... 

Guinier analysis provides a straightforward way to measure the molecular weight of the molecule or molecular complex under study. 

Table I Comparison of Results Between the Guinier Analysis and the Polynomial Analysis... 

Such a plot has a slope of With determined by this Guinier analysis. Equation 14.47b implies that at large q, ideally s 5, the normalized scattered intensity will obey... 

FIGURE 14.16 Guinier analysis of structure factor data in Figure 14.15. By Equation 14.53 I vs. yields straight lines with slope... 

Sorensen, C.M. and Shi, D., Guinier analysis for homogeneous dielectric spheres of arbitrary size. Opt. Commun, 178, 31, 2000. 

Standard techniques have been used to analyze the SAXS profiles (16). A Guinier analysis of the low q portion of the curves could not be utilized since a plot of In I(q) against q2 was not linear over the q-range investigated. This would have given an estimate of the size of the entities giving rise to the zero-order scattering. 

The scattering curve of a sphere descends into a series of minima md maxima as Q increasp- i, with the first minimum at QR = 4.493. Thus the Aq of the sphere can be calculated from the minima as a verification of the Guinier analysis. The curves for full and hollow spheres are very similar at low Q. The intensities of the subsidiary... 

An alternative estimate for may be obtained via Guinier analysis if the voids are reasonably monodisperse, as indicated in Fig. 23.11. Assuming that the voids are spherical, the radius (R) may be obtained from the measured via R = (5/3) / g 348 A. The extrapolated cross section dS/d/2(0) 142cm is given by... 

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