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, 99 (2), 595-9

Electric Field-Driven Disruption of a Native Beta-Sheet Protein Conformation and Generation of a Helix-Structure

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Electric Field-Driven Disruption of a Native Beta-Sheet Protein Conformation and Generation of a Helix-Structure

Pedro Ojeda-May et al. Biophys J.

Abstract

We demonstrate that an external constant electric field is able to modify the secondary structure of a protein and induce a transition from a beta-sheet into a helix-like conformation. This dramatic change is driven by a global rearrangement of the dipole moments at the amide planes. We also predict electric-field-induced modifications of the intermediate states of the protein.

Figures

Figure 1
Figure 1
The dipoles of NH and OC in the amide plane give rise to a total dipole moment for each amino acid, which has the value 1.1 × 10−29 Cm.
Figure 2
Figure 2
(Color online) Free energy surface of the V3-loop as a function of the configurational energy E and the end-to-end distance Q for different strengths of the external electric field εE0: ε = 0.0, 0.4, 0.8, and 1.2. Local minima labeled as I1 and I2 correspond to intermediates. N1 refers to the native state in absence of field, which becomes metastable (I3) for ε = 0.8. Note the formation of a new global minimum N2 for the field strength ε = 1.2. U corresponds to the unfolded states. The temperature in all cases is T = Tf = 321 K.
Figure 3
Figure 3
(Color online) Coordinates in the (E, Q)-plane of the conformations yielding the maximal contribution to the partition function for ε = 0.0, 0.4, 0.8, and 1.2 and at different temperatures. The field strength is given by εE0 (see text). Note that for ε = 0.0 the observable structures lie around the point (E = − 135, Q = 5) (β-sheet) while for ε = 1.2 they are located near the point (E = –150, Q = 30) (helix). Dark (blue) and light (yellow) diamonds refer to low and high temperatures, respectively (see temperature scale).
Figure 4
Figure 4
(Color online) Ramachandran plot of the V3-loop for different strengths of the external electric field represented by the dimensionless factor ε (see text) at T = Tf = 321 K. The regions corresponding to helices and β-sheets are indicated.
Figure 5
Figure 5
The α-helix structure of the native state for a field strength of εE0 with εE0 = 5.16 × 108.

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