L.V. Melo

Subunits of the chaperonin CCT are associated with Tetrahymena microtubule structures and are involved in cilia biogenesis.

The cytosolic chaperonin CCT is a heterooligomeric complex of about 900 kDa that mediates the folding of cytoskeletal proteins. We observed by indirect immunofluorescence that the Tetrahymena TpCCTalpha, TpCCTdelta, TpCCTepsilon, and TpCCTeta-subunits colocalize with tubulin in cilia, basal bodies, oral apparatus, and contractile vacuole pores. TpCCT-subunits localization was affected during reciliation. These findings combined with atomic force microscopy measurements in reciliating cells indicate that these proteins play a role during cilia biogenesis related to microtubule nucleation, tubulin transport, and/or axoneme assembly. The TpCCT-subunits were also found to be associated with cortex and cytoplasmic microtubules suggesting that they can act as microtubule-associated proteins. The TpCCTdelta being the only subunit found associated with the macronuclear envelope indicates that it has functions outside of the 900 kDa complex. Tetrahymena cytoplasm contains granular/globular-structures of TpCCT-subunits in close association with microtubule arrays. Studies of reciliation and with cycloheximide suggest that these structures may be sites of translation and folding. Combined biochemical techniques revealed that reciliation affects the oligomeric state of TpCCT-subunits being tubulin preferentially associated with smaller CCT oligomeric species in early stages of reciliation. Collectively, these findings indicate that the oligomeric state of CCT-subunits reflects the translation capacity of the cell and microtubules integrity.

Huygens synchronization of two clocks

The synchronization of two pendulum clocks hanging from a wall was first observed by Huygens during the XVII century. This type of synchronization is observed in other areas, and is fundamentally different from the problem of two clocks hanging from a moveable base. We present a model explaining the phase opposition synchronization of two pendulum clocks in those conditions. The predicted behaviour is observed experimentally, validating the model.

Towards conductive textiles: coating polymeric fibres with graphene

Conducting fibres are essential to the development of e-textiles. We demonstrate a method to make common insulating textile fibres conductive, by coating them with graphene. The resulting fibres display sheet resistance values as low as 600 Ωsq−1, demonstrating that the high conductivity of graphene is not lost when transferred to textile fibres. An extensive microscopic study of the surface of graphene-coated fibres is presented. We show that this method can be employed to textile fibres of different materials, sizes and shapes, and to different types of graphene. These graphene-based conductive fibres can be used as a platform to build integrated electronic devices directly in textiles.

Novel nanosized patterning technology based on electropulsed scanning probe microscopy

Abstract Scanning Probe Microscopes (SPM) have been used to change surfaces at nanometer scales. We report the deposition of user defined patterns in a controlled manner using an electropulsed SPM. The patterns were fabricated by applying −12 V electrical pulses in the 10–40-Hz range between a commercial CoCr conductive tip and a crystalline n-doped Si wafer. The tip damage during deposition is negligible as measurements on the same surface region before and after deposition show no detectable differences. Immediately after deposition, the same tip is used for measuring the fabricated patterns. Applying one isolated electrical pulse results in a pixel with a typical size of the order of 30 nm. By combining the scanning ability of the SPM with the atmospheric deposition induced by electrical pulses on the tip, patterns can be fabricated. For example, by applying electrical pulses during a 25×800-nm tip scan in AFM tapping mode, at 40 Hz, lines with 65-nm width by 828-nm length were obtained (in good agreement with the expected dimensions of 55×830 nm derived from the pixel size and the scan range). The height of the deposited patterns is of the order of 2 to 3 nm, and was found to increase with the density of scan lines. The RMS roughness of the deposited material is shown to be strongly dependent on the electrical pulse frequency. The smoother pattern surface results from the 40-Hz pulse frequency. No deposition was observed at higher frequencies.

Position-controlled nanodeposition of magnets using an electropulsed scanning probe microscope

Abstract Scanning probe microscopes (SPM) have been used to change surfaces at nanometer scales. We report the deposition of magnets in user defined patterns using an electropulsed atomic force microscope (AFM). The patterns were fabricated by applying −12 V electrical pulses in the 10–40 Hz range between a commercial CoCr-covered Si tip and a crystalline n-doped Si wafer. The tip damage during deposition is negligible. Immediately after deposition the same tip was used for performing AFM and magnetic force microscopy (MFM) measurements on the fabricated patterns. Applying one isolated electrical pulse results in a pixel with a typical size of the order of 28 nm as measured by AFM. By combining the scanning ability of the SPM with the atmospheric deposition induced by electrical pulses on the tip, user-defined patterns can be fabricated. The height of the deposited patterns is of the order of 2–3 nm. The MFM measurements performed in different scanning directions show a preferential magnetization direction as shown by the higher fringe fields from the rectangles shorter edges.

Tetrahymena Cilia Cap is Built in a Multi-step Process: A Study by Atomic Force Microscopy

Cilia are complex and dynamic organelles that have motility and sensory functions. Defects in cilia biogenesis and function are at the origin of human ciliopathies. In motile cilia, a basal body organizes the axoneme composed of nine microtubule doublets surrounding a central pair of singlet microtubules. The distal ends of axonemal microtubules are attached to the membrane by microtubule-capping structures. Little is known about the early steps of cilium assembly. Although cilia grow and resorb from their distal tips, it remains poorly understood where and when the components of the caps are first assembled. By using Atomic Force Microscopy in tapping mode, with resolution at the nanometer range and with minimum sample manipulation, we show that Tetrahymena cilia assembly requires transient assembly of structures, composed of three components that are placed asymmetrically on an early elongating axoneme. In small uncapped axonemes the microtubule central pair was never observed. Additionally, we show that cilia cap assembly is a multi-step process in which structures of different sizes and shapes are put together in close proximity before the axoneme appears capped. We propose that the cap modifies the axoneme microtubule rate of polymerization and present a model for Tetrahymena cilia cap assembly.