Publications by Barak Gilboa

Confinement-free wide-field ratiometric tracking of single fluorescent molecules

Biophysical Journal Elsevier BV (2019)

B Gilboa, B Jing, TJ Cui, M Sow, A Plochowietz, A Mazumder, AN Kapanidis

Strong Electro-Optic effect and spontaneous domain formation in self-assembled peptide structures.

Advanced Science Wiley 4 (2017) 1700052

B Gilboa, C Lafargue, A Handelman, LJW Shimon, G Rosenman, J Zyss, T Ellenbogen

Short peptides made from repeating units of phenylalanine self-assemble into a remarkable variety of micro- and nanostructures including tubes, tapes, spheres, and fibrils. These bio-organic structures are found to possess striking mechanical, electrical, and optical properties, which are rarely seen in organic materials, and are therefore shown useful for diverse applications including regenerative medicine, targeted drug delivery, and biocompatible fluorescent probes. Consequently, finding new optical properties in these materials can significantly advance their practical use, for example, by allowing new ways to visualize, manipulate, and utilize them in new, in vivo, sensing applications. Here, by leveraging a unique electro-optic phase microscopy technique, combined with traditional structural analysis, it is measured in di- and triphenylalanine peptide structures a surprisingly large electro-optic response of the same order as the best performing inorganic crystals. In addition, spontaneous domain formation is observed in triphenylalanine tapes, and the origin of their electro-optic activity is unveiled to be related to a porous triclinic structure, with extensive antiparallel beta-sheet arrangement. The strong electro-optic response of these porous peptide structures with the capability of hosting guest molecules opens the door to create new biocompatible, environmental friendly functional materials for electro-optic applications, including biomedical imaging, sensing, and optical manipulation.

Strong Electro-Optic Effect in Self Assembled Peptide Nanofibers


B Gilboa, C Lafargue, A Handelman, LJW Shimon, G Rosenman, J Zyss, T Ellenbogen, IEEE

Tomographic phase microscopy using optical tweezers


M Habaza, B Gilboa, Y Roichman, NT Shaked

Tomographic phase microscopy with 180° rotation of live cells in suspension by holographic optical tweezers.

Optics letters 40 (2015) 1881-1884

M Habaza, B Gilboa, Y Roichman, NT Shaked

We present a new tomographic phase microscopy (TPM) approach that allows capturing the three-dimensional refractive index structure of single cells in suspension without labeling, using 180° rotation of the cells. This is obtained by integrating an external off-axis interferometer for wide-field wave front acquisition with holographic optical tweezers (HOTs) for trapping and micro-rotation of the suspended cells. In contrast to existing TPM approaches for cell imaging, our approach does not require anchoring the sample to a rotating stage, nor is it limited in angular range as is the illumination rotation approach. Thus, it allows noninvasive TPM of suspended live cells in a wide angular range. The proposed technique is experimentally demonstrated by capturing the three-dimensional refractive index map of yeast cells, while collecting interferometric projections at an angular range of 180° with 5° steps. The interferometric projections are processed by both the filtered back-projection method and the diffraction theory method. The experimental system is integrated with a spinning disk confocal fluorescent microscope for validation of the label-free TPM results.

Cellular reconstitution of actively self-organizing systems

in Cell and Matrix Mechanics, (2014) 63-100

O Sitxon-Mendelson, B Gilboa, Y Ideses, A Bernheim-Groswasser

© 2015 by Taylor & Francis Group, LLC. Living cells are extremely sophisticated devices that detect specific environmental signals, process this information, and generate specific mechanical responses, such as growth, shape change, or directed movement. The active part of the biodevice is the cell cytoskeleton, a spatially extended network (gel), self-organized, mechanochemical machine that forms via the nucleation and multiscale self-organization of biomolecules (e.g., biopolymers such as filamentous actin [F-actin], microtubules [MTs], accessory proteins, and molecular motors [1,2]), in both the temporal and spatial domains. The cytoskeleton determines the mechanical properties of a cell and plays important roles in many cellular processes, such as division [3-5], motility [6], adhesion [7], and tissue morphogenesis. The multiscale nature of the cytoskeleton enables response times ranging from fast dynamics for individual molecular-sized building blocks to the persistent motion or shape change of whole cells over minutes and hours, well beyond the time range of man-made analogues.

The fusion of actin bundles driven by interacting motor proteins.

Physical biology 6 (2009) 036003-

D Gillo, B Gilboa, R Gurka, A Bernheim-Groswasser

The cooperative action of many molecular motors is essential for dynamic processes such as cell motility and mitosis. This action can be studied by using motility assays which track the motion of cytoskeletal filaments over a surface coated with motor proteins. Here, we propose to use a motility assay consisting of a-polar actin bundles subjected to the action of myosin II motors where no external loading is applied. In this work we focus on those bundles undergoing fusion with other nearby bundles. Specifically, we investigate the role of the bundles' dimension on the transition from bidirectional to directional motion and on the properties of their motion during fusion. Our experimental data reveal that only small bundles exhibit dynamic transition to directional motion, implying that the forces acting on them exceed the threshold value necessary to induce the transition. Moreover, these bundles accelerate along their trajectory, suggesting that the forces acting on them increase while approaching each other. We show that these forces do not originate from external loading but rather arise from the action of the motors on the bundles. These forces are transmitted through the medium over micron-scale distances without being cut off. Moreover, we show that the forces propagate to distances that are proportional to the size of the bundles, or equivalently, to the number of motors, which they interact with.

Bidirectional cooperative motion of myosin-II motors on actin tracks with randomly alternating polarities

SOFT MATTER 5 (2009) 2223-2231

B Gilboa, D Gillo, O Farago, A Bernheim-Groswasser

Bidirectional Cooperative Motion Of Myosin-II Motors On Actin Tracks With Randomly Alternating Polarities


A Bernheim, B Gilboa, D Gillo, O Farago