Kratky plot

A Kratky plot is obtained by plotting scattering intensity as $\scriptstyle I(q)\times q^{2}$ vs. $\scriptstyle q$ (instead of simply $\scriptstyle I(q)$ vs. $\scriptstyle q$). This representation divides-out the decay of the scattering, making certain other features more evident.

In particular, a Kratky analysis is often performed on polymer solutions. Here, the shape of the curve in the Kratky plot helps identify the conformation of the polymer chain: a rise to a plateau indicates an unfolded chain (random coil), whereas a distinct peak is indicative of a compact or folded conformation for the chain (in biological studies, this may be a protein in a well-defined/folded state). Other conformations can also potentially be distinguished (pseudo-linear rise for rod-like conformation, high-q upturn from the plateau indicates worm-like chain, etc.). In polymer gels, a peak may indicate the presence of inhomogeneities, such as clustering.

See Also

• Guinier plot
• Zimm plot
• Example:Polymer clustering
• Wikipedia:Kratky plot
• [http://www.bioisis.net/tutorial/6 bioisis.net:Kratky Analysis