Publications

2026

• On the origins and variation of nucleotide skews of archaeal genomes
  
  • Paravel Adrien
  • Mottez Clémence
  • Puech Romain
  • Flament Didier
  • Becker Hubert F
  • Myllykallio Hannu
  Frontiers in Microbiology, Frontiers Media, 2026, 17, pp.1727296. We have used nucleotide skews as the proxy to understand the evolution of archaeal genomes. Our genome-wide studies using substantial datasets suggest that translational selection and the nature of the genetic code are universally conserved determinants of asymmetric guanine and cytosine distributions. We propose that in the case of the majority of bacterial chromosomes, mutational processes and/or DNA repair also result in the strand-specific nucleotide skews. This is in stark contrast to what we observe for archaeal chromosomes and plasmids, and reveals that archaea have a greatly reduced ability to create mutations and/or repair DNA damage in a strand-specific manner. We suggest that in the future, the described computational and statistical approach will help to understand the evolutionary dynamics of the archaeal chromosomes through the tree of life. (10.3389/fmicb.2026.1727296)
  DOI : 10.3389/fmicb.2026.1727296
• On-axis and off-axis levitation by a rotating permanent magnet
  
  • Schreckenberg Hugo
  • El Omari El Alaoui Zayneb
  • Gallot Guilhem
  Physical Review E, American Physical Society (APS), 2026, 113 (5), pp.055503. A slightly tilted permanent magnet rotating at high speed can induce a magnetic field capable of trapping another permanent magnet in a gravity independent levitated bound state, bypassing Earnshaw's theorem. During levitation, the floater magnet is locked in a conical orbit at the same frequency as the rotor. This rotation allows the sides of the same polarity of each magnet to face each other, which is responsible for the dynamic equilibrium of the floater magnet. Here, we theoretically explain the motion of the floater in-axis and off-axis and highlight levitation stability conditions and their dependence on the size of the floater and the speed of the rotor. We also experimentally studied the levitation conditions with respect to the rotational speed of the rotor for various floater's sizes and shapes. We observed and analyzed the lower and upper limits of levitation. Finally, we explained the off-axis motion of the center of mass of the floater from its equilibrium position by an extension of the dipole moment model. (10.1103/5ysx-412r)
  DOI : 10.1103/5ysx-412r
• Resonant third harmonic generation in biological pigments
  
  • Dees Stella
  • Ferrer Ortas Júlia
  • Mahou Pierre
  • Supatto Willy
  • Olivier Nicolas
  • Beaurepaire Emmanuel
  APL Photonics, AIP Publishing LLC, 2026, 11 (8), pp.086116. Third harmonic generation (THG) microscopy provides label-free structural contrast of biological tissues. While the THG process can be enhanced by electronic transitions in absorbing molecules, knowledge of the third-order nonlinear properties of biological pigments is limited, and the potential of THG imaging for chemically selective imaging remains underutilized. In this study, we investigated resonant THG in pigments by performing nonlinear microspectroscopy in situ on three representative absorbers: hemoglobin in red blood cells, pteridines in xanthophores, and melanin in human hair. We measured THG spectra in the 1120–1300 nm excitation range. We observed a wavelength-dependent signal enhancement ranging from 10 to 100 times in these pigmented structures, depending on their respective absorption properties. We developed a numerical model of THG from interfaces, including resonant and non-resonant contributions, to interpret these observations. Our calculations reproduce key experimental trends, including resonance-induced enhancement factors and spectral properties. Finally, we demonstrate that third-order sum-frequency generation (TSFG) imaging provides spectroscopic contrast capable of distinguishing red blood cells from xanthophores in live zebrafish larvae. These results suggest that THG/TSFG is a promising approach to label-free, pigment-specific multiphoton imaging. (10.1063/5.0341777)
  DOI : 10.1063/5.0341777