*2.4. His6 VPg\* and His6 VPg\*-His6 eIF4E Binary Complex Shapes Differ from the Globular State*

The deduced experimental rotational correlation time, *θexp*, increased from 23.7 ns for His6 VPg\* to 49 ns for the His6 VPg\*-His6 eIF4E binary complex. The *θcalc* values for hydrated rigid spheres of 26 kDa and 54.7 kDa were 9.8 ns and 20.6 ns (His6 VPg\* and His6 VPg\*-His6 eIF4E respectively), indicating that His6 VPg\* and His6 VPg\*-His6 eIF4E shapes differ from the compact globular state. On an indicative basis, the compact EΔ(1–46) [26] displayed an *θexp* value (7.9 ns) which was close to the *θcalc* value (9.8 ns) calculated for a globular protein of comparable molecular weight. The *θexp*/*θcalc* ratio for the His6 VPg\*-His6 eIF4E complex and His6 VPg\* were close, suggesting that the complex formation has no effect on the probe segmental motion within the VPg [30].
