Photomechanical responses in Drosophila photoreceptors
Roger C. Hardie,
Kristian Franze
Science (New York, N.Y.)
338
(6104)
260-263
(2012)
| Journal
Phototransduction in Drosophila microvillar photoreceptor cells is mediated by a G protein-activated phospholipase C (PLC). PLC hydrolyzes the minor membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP(2)), leading by an unknown mechanism to activation of the prototypical transient receptor potential (TRP) and TRP-like (TRPL) channels. We found that light exposure evoked rapid PLC-mediated contractions of the photoreceptor cells and modulated the activity of mechanosensitive channels introduced into photoreceptor cells. Furthermore, photoreceptor light responses were facilitated by membrane stretch and were inhibited by amphipaths, which alter lipid bilayer properties. These results indicate that, by cleaving PIP(2), PLC generates rapid physical changes in the lipid bilayer that lead to contractions of the microvilli, and suggest that the resultant mechanical forces contribute to gating the light-sensitive channels.
Complex stiffness gradient substrates for studying mechanotactic cell migration
Cheng-Hwa R. Kuo,
Jian Xian,
James D. Brenton,
Kristian Franze,
Easan Sivaniah
Polyacrylamide gels are cast upon a stiff support with controlled topography, resulting in a thin gel layer of variable height. The topographical profiles project a stiffness map onto the gel, resulting in controlled linear and non-linear 2D stiffness gradients. Fibroblasts, which migrate towards stiffer substrates, accumulate in areas with a gel thickness below 15 μm.
Photonic Crystal Light Collectors in Fish Retina Improve Vision in Turbid Water
Moritz Kreysing,
Roland Pusch,
Dorothee Haverkate,
Meik Landsberger,
Jacob Engelmann,
Janina Ruiter,
Carlos Mora-Ferrer,
Elke Ulbricht,
Jens Grosche, et al.
Despite their diversity, vertebrate retinae are specialized to maximize either photon catch or visual acuity. Here, we describe a functional type that is optimized for neither purpose. In the retina of the elephantnose fish (Gnathonemus petersii), cone photoreceptors are grouped together within reflecting, photonic crystal-lined cups acting as macroreceptors, but rod photoreceptors are positioned behind these reflectors. This unusual arrangement matches rod and cone sensitivity for detecting color-mixed stimuli, whereas the photoreceptor grouping renders the fish insensitive to spatial noise; together, this enables more reliable flight reactions in the fish's dim and turbid habitat as compared with fish lacking this retinal specialization.
Reversible switching between superhydrophobic states on a hierarchically structured surface
Tuukka Verho,
Juuso T. Korhonen,
Lauri Sainiemi,
Ville Jokinen,
Chris Bower,
Kristian Franze,
Sami Franssila,
Piers Andrew,
Olli Ikkala, et al.
Proceedings of the National Academy of Sciences of the United States of America
109
(26)
10210-10213
(2012)
| Journal
| PDF
Nature offers exciting examples for functional wetting properties based on superhydrophobicity, such as the self-cleaning surfaces on plant leaves and trapped air on immersed insect surfaces allowing underwater breathing. They inspire biomimetic approaches in science and technology. Superhydrophobicity relies on the Cassie wetting state where air is trapped within the surface topography. Pressure can trigger an irreversible transition from the Cassie state to the Wenzel state with no trapped air--this transition is usually detrimental for nonwetting functionality and is to be avoided. Here we present a new type of reversible, localized and instantaneous transition between two Cassie wetting states, enabled by two-level (dual-scale) topography of a superhydrophobic surface, that allows writing, erasing, rewriting and storing of optically displayed information in plastrons related to different length scales.
Contact
Neuronal Mechanics Division Prof. Kristian Franze Principal Investigator
Max-Planck-Zentrum für Physik und Medizin Kussmaulallee 2 91054 Erlangen, Germany
