The clathrin triskelion, which is a three-legged pinwheel-shaped heteropolymer, 
is a major component in the protein coats of certain post-Golgi and endocytic 
vesicles. At low pH, or at physiological pH in the presence of assembly 
proteins, triskelia will self-assemble to form a closed clathrin cage, or 
"basket". Recent static light scattering and dynamic light scattering studies of 
triskelia in solution showed that an individual triskelion has an intrinsic 
pucker similar to, but differing from, that inferred from a high resolution 
cryoEM structure of a triskelion in a clathrin basket. We extend the earlier 
solution studies by performing small-angle neutron scattering (SANS) experiments 
on isolated triskelia, allowing us to examine a higher q range than that probed 
by static light scattering. Results of the SANS measurements are consistent with 
the light scattering measurements, but show a shoulder in the scattering 
function at intermediate q values (0.016 A(-1)), just beyond the Guinier regime. 
This feature can be accounted for by Brownian dynamics simulations based on 
flexible bead-spring models of a triskelion, which generate time-averaged 
scattering functions. Calculated scattering profiles are in good agreement with 
the experimental SANS profiles when the persistence length of the assumed 
semiflexible triskelion is close to that previously estimated from the analysis 
of electron micrographs.