Pair distance distribution function of squid HMM derived from small angle x-ray solution scattering data.

<p>The pair distance distribution function (denoted P(r)) function may be interpreted as the r²-weighted distribution of all possible electron pair distances within the protein. <b>A</b>) In the absence of calcium (EGTA+AMP.PNP), the protein assumes a unimodal P(r) distribution characteristic of a simple compact globular shape (solid line). In the presence of calcium (Ca²⁺+AMP.PNP) the protein gives a more extended bimodal P(r) distribution indicating the presence of two separated domains (dashed line). <b>B</b>) Similar P(r) functions are observed when ADP is used instead of AMP.PNP. For comparison, curves are shown together with the same maximum diameter cutoff (Dmax) of 300 Å.