The Diamagnetic Susceptibility of the Tubulin Dimer

[摘要] An approximate value of the diamagnetic anisotropy of the tubulin dimer,Δχdimer, has been determined assuming axial symmetry and that only theα-helices andβ-sheets contribute to the anisotropy. Two approaches have been utilized: (a) using the value for theΔχαfor anα-helical peptide bond given by Pauling (1979) and (b) using the previously determined anisotropy of fibrinogen as a calibration standard. TheΔχdimer≈4×10-27 JT−2obtained from these measurements are similar to within 20%. Although Cotton-Mouton measurements alone cannot be used to estimateΔχdirectly, the value we measured,CMdimer=1.41±0.03×10-8 T−2cm2mg−1, is consistent with the above estimate forΔχdimer. The method utilized for the determination of the tubulin dimer diamagnetic susceptibility is applicable to other proteins and macromolecular assemblies as well.

[学科分类] 生物化学/生物物理