sodium-dodecyl-sulfate and alpha-cyclodextrin

An extensive dynamic and structural characterization of the supramolecular complexes that can be formed by mixing α-, β-, and γ-cyclodextrin (CD) with sodium dodecyl sulfate (SDS) in water at 283, 298, and 323 K was performed by means of computational molecular dynamics simulations. For each CD at the three temperatures, seven different initial conformations were used, generating a total of 63 trajectories. The observed stoichiometries, intermolecular distances, and relative orientation of the individual molecules in the complexes, as well as the most important interactions which contribute to their stability and the role of the solvent water molecules were studied in detail, revealing clear differences and similarities between the three CDs. Earlier reported findings in the inclusion complexes field are also discussed in the context of the present results. For any of the three native cyclodextrins, the CD(2)SDS(1) species in the head-to-head conformation appears to be a promising building block for nanotubular aggregates both in the bulk and at the solution/air interface, as earlier suggested for the case of α-CD. Moreover, the observed noninclusion arrangements involving β-CD are proposed as the seed for the premicellar (β-CD)-induced aggregation of SDS described in the literature.

Topics: alpha-Cyclodextrins; beta-Cyclodextrins; gamma-Cyclodextrins; Molecular Dynamics Simulation; Sodium; Sodium Dodecyl Sulfate; Temperature; Time Factors

Refolding of proteins is traditionally carried out either by diluting the denaturant-unfolded protein into buffer (GdmCl-jump) or by mixing the acid-denatured protein with strong buffer (pH-jump). The first method does not allow direct measurement of folding rates in water since the GdmCl cannot be infinitely diluted, and the second method suffers from the limitation that many proteins cannot be pH-denatured. Further, some proteins do not refold reversibly from low pH where they get trapped as aggregation prone intermediates. Here, we present an alternative approach for direct measurement of refolding rates in water, which does not rely on extrapolation. The protein is denatured in SDS, and is then mixed with alpha-cyclodextrin, which rapidly strips SDS molecules from the protein, leaving the naked unfolded protein to refold.

Topics: alpha-Cyclodextrins; Animals; Chickens; Cyclodextrins; Dose-Response Relationship, Drug; Female; Hydrogen-Ion Concentration; Isomerism; Kinetics; Muramidase; Proline; Protein Denaturation; Protein Folding; Proteins; Ribosomal Protein S6; Ribosomal Proteins; Sodium Dodecyl Sulfate; Thermodynamics; Water