Biology subjects

Bertinetti, L.

Publications and source records attributed to Bertinetti, L..

3 recordsLinked to original sources

bioRxiv2019

Hierarchically-structured metalloprotein composite coatings biofabricated from co-existing condensed liquid phases

Complex hierarchical structure governs emergent properties in soft biopolymeric materials; yet, the material processing involved remains poorly understood. Here, we investigated the multiscale structure and composition of the mussel byssus cuticle before, during and after formation to gain further insight into the processing of this hard, yet extensible metal cross-linked protein composite. Our findings reveal that the granular substructure crucial to the cuticles function as a wear-resistant coating of an extensible polymer fiber is pre-organized in condensed liquid phase secretory vesicles. These are separated into catechol-rich proto-granules enveloped in a sulfur-rich proto-matrix which fuses during secretion, forming the sub-structure of the cuticle. Metal ions are added subsequently in a site-specific way, with Fe contained in the sulfur-rich matrix and V being relegated to the granules, coordinated by catechol. We posit that this hierarchical structure self-organizes via phase separation of specific amphiphilic protein components within secretory vesicles, resulting in a meso-scale structuring, critical to the cuticles advanced function.

biophysics↗

bioRxiv2019

Three-dimensional Structural Interrelations between Cells, Extracellular Matrix and Mineral in Vertebrate Mineralization

The spatial-temporal relationship between cells, extracellular matrices and mineral deposits is fundamental for an improved understanding mineralization mechanisms in vertebrate tissues. By utilizing focused ion beam-scanning electron microscopy with serial surface imaging, normally mineralizing avian tendons have been studied with nanometer resolution in three dimensions with volumes exceeding tens of microns in range. These parameters are necessary to yield fine ultrastructural details while encompassing tissue domains sufficient to provide a comprehensive overview of the interrelationships between the tissue structural constituents. Investigation reveals a novel complex cellular network in highly mineralized tendon aspects, where [~]100 nm diameter canaliculi emanating from cell (tenocyte) lacunae surround extracellular collagen fibril bundles. Canaliculi are linked to smaller channels of [~]40 nm diameter, occupying spaces between fibrils. Close to the tendon mineralization front, calcium-rich globules appear between the fibrils and, with time, mineral propagates along and within collagen. These close associations between tenocytes, canaliculi, small channels, collagen and mineral suggest a new concept for the mineralization process, where ions and/or mineral precursors may be transported through spaces between fibrils before they crystallize along the surface of and within the fibrils.\n\nSignificance StatementThe basic mechanism by which vertebrate collagenous tissues are mineralized is still not fully elucidated, despite the importance of this process for skeletal formation and regeneration. Through three-dimensional imaging of the cellular network together with the extracellular matrix and mineral deposits, the present work investigates normally mineralizing avian leg tendon as a model system for vertebrates in general. The data support a mechanism where mineral ions and possible mineral precursors are initially present in interfibrillar collagen spaces and are subsequently translocated to neighboring collagen fibrils. Mineral particles then nucleate in association with collagen to form the well known collagen-mineral composite material of the skeleton.

bioengineering↗

bioRxiv2019

Epidermal cell surface structure and chitin-protein co-assembly determine fiber architecture in the Locust cuticle

The geometrical similarity of helicoidal fiber arrangement in many biological fibrous extracellular matrices, such as bone, plant cell wall or arthropod cuticle, to that of cholesteric liquid mesophases has led to the hypothesis that they may form passively through a mesophase precursor rather than by direct cellular control. In search of direct evidence to support or refute this hypothesis, here, we studied the process of cuticle formation in the tibia of the migratory locust, Locusta migratoria, where daily growth layers arise by the deposition of fiber arrangements alternating between unidirectional and helicoidal structures. Using FIB/SEM volume imaging and scanning X-ray scattering, we show that the epidermal cells determine an initial fiber orientation from which the final architecture emerges by the self-organized co-assembly of chitin and proteins. Fiber orientation in the locust cuticle is therefore determined by both active and passive processes.

biophysics↗