Browsing by Autor "Aritz Leonardo"

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A Simple Solution for an Electromagnetic Wave in a Third-Order Nonlinear Anisotropic Medium
(2024) Choque Elias; Aritz Leonardo
This work examines how a transverse magnetic mode electromagnetic wave propagates in a medium with thirdorder nonlinear and anisotropic electric permittivity. The proposed model is solved using the homotopy analysis method. Two cases are considered: the first analyzes a wave traveling through an infinite medium, and the results show a transverse rotation of the electric field, indicating that the material induces a change in longitudinal polarization. In the second case, the wave passes through a waveguide with metallic boundaries. The eigenvalues were determined and compared with those of a linear and isotropic material. The results show that nonlinearity and anisotropy eliminate the first eigenvalues, while, for large eigenvalues, both materials exhibit the same values.
Analytical Framework for Tunable Spectral Permittivity in Polar Media under DC Bias
(2025) Aritz Leonardo; Choque Elias; Flores Susan; Calcina Marcelo
A theoretical model is presented to describe the nonlinear dielectric response of a polar medium simultaneously subjected to a DC bias field and a harmonic AC excitation. Starting from a second-order anharmonic differential equation, the Homotopy Analysis Method (HAM) is applied to obtain closed-form analytical solutions for both transient and steady-state behavior up to the sixth order in the homotopy series. The results reveal the generation of $2 \omega$ and $3 \omega$ harmonics, temporal modulation of the induced polarization, and a quadratic tuning of the effective permittivity with the DC field. The work combines a complete analytical formulation of HAM, numerical validation, and a detailed physical analysis of the steady-state regime, emphasizing spectral dispersion, stability, and total harmonic distortion.
Multivalent Interactions between Chaperone and Ribosome-Nascent Chain Complex Revealed by High-Speed AFM and MD Simulations
(American Chemical Society, 2025) Eider Núñez; Prithwidip Saha; Markel G. Ibarluzea; Arantza Muguruza‐Montero; Sara M‐Alicante; Rafael Ramis; Aritz Leonardo; Aitor Bergara; Álvaro Villarroel; Félix Rico
Trigger Factor (TF) is a primary ATP-independent molecular chaperone in bacteria that engages nascent polypeptide chains emerging from the ribosomal exit tunnel to assist their folding. However, the real-time behavior of TF during active translation under near-physiological conditions remains elusive. Here, we employ high-speed atomic force microscopy (HS-AFM) imaging to visualize TF dynamics on intact <i>Escherichia coli</i> ribosomes in real time. We observe that TF transitions between compact and extended conformations and forms stable and transient contacts near ribosomal proteins uL23 and bL17, respectively. Interestingly, TFs engage distinct regions of the same ribosome-nascent chain complex, with one TF binding near the nascent chain and another near bL17, revealing multivalent interactions on the ribosome surface. Complementary all-atom molecular dynamics simulations reproduced the observed TF conformations and interaction dynamics, validating the experimentally observed structural transitions and dual-site engagement. This integrative approach uncovers previously inaccessible dynamics of ribosome-associated chaperones and offers a broadly applicable platform to probe cotranslational folding under near-physiological conditions.