Synthetic Modulation of an Unstable Dehydrosecodine-type Intermediate and Its Encapsulation into a Confined Cavity Enable Its X-ray Crystallographic Observation.

Numerous indole alkaloids such as the iboga- and aspidosperma-type are believed to be biosynthesized via a common hypothetical intermediate, dehydrosecodine. The highly reactive nature of dehydrosecodine-type compounds has hampered their isolation and structural elucidation. In this study, we achieved the first X-ray structural determination of a dehydrosecodine-type compound by integrating synthetic optimization of the reactivity and stabilizing the fragile molecule by encapsulation into a supramolecular host. Formation of a 1 : 1 complex of the dehydrosecodine-type labile guest bearing both vinyl indole and dihydropyridine units with the host was observed. This integrated approach not only provides insights into the biosynthetic conversions but also allows stabilization and storage of the reactive and otherwise short-lived intermediate within the confined hydrophobic cavity.

Integrative and comparative analysis of coiled-coil based marine snail egg cases - a model for biomimetic elastomers.

Integrative and comparative analyses of biomaterials systems offer the potential to reveal conserved elements that are essential for mechanical function. The approach also affords the opportunity to identify variation in designs at multiple length scales, enabling the delineation of a range of parameters for creating precisely tuned biomimetic materials. We investigated the molecular design and structural hierarchy of elastomeric egg capsules from the marine snail Pugilina cochlidium (family Melongenidae) and compared these data with all available published studies in order to infer the structure-property relationships of the egg case from the molecular to the macroscopic scale. While mechanical similarities had previously been observed for two other marine melongenid snails, Busycotypus canaliculatus and Busycon carica, B. canaliculatus was the only species for which detailed molecular and nanostructural data were available. Egg capsules from P. cochlidium were found to exhibit mechanical properties and shock absorbing potential that was similar to B. canaliculatus. The two species also displayed similarity in hierarchical fibril bundling and a sub-micron staggering of 100-105 nm within filaments, as shown by atomic force microscopy and small angle X-ray diffraction. In situ Raman micro spectroscopy indicated that P. cochlidium egg cases undergo a stress-induced coiled-coil to extended ß-strand structural transformation that is very similar to that of B. canaliculatus. These observations supported the view that these structural and hierarchical elements are essential for egg case function. Comparative analysis of the primary amino acid sequences and structural predictions for all known egg case proteins suggested that while the proteins all contain sequences prone to adopt α-helical structures, the predicted location of coiled-coil domains and stutter perturbations varied within and between species. Despite these differences, mixtures of denatured native egg case proteins readily re-folded in citrate-phosphate assembly buffer into α-helix rich, coiled-coil based oligomers, as determined by attenuated total reflection Fourier transform infrared spectroscopy, circular dichroism and MALDI-TOF. It is concluded that both conserved and divergent designs in marine snail egg cases offer inspiration for the engineering of biomimetic elastomeric materials with a unique capability for mechanical energy absorption.

Structural proteins from whelk egg capsule with long range elasticity associated with a solid-state phase transition.

The robust, proteinaceous egg capsules of marine prosobranch gastropods (genus Busycotypus ) exhibit unique biomechanical properties such as high elastic strain recovery and elastic energy dissipation capability. Capsule material possesses long-range extensibility that is fully recoverable and is the result of a secondary structure phase transition from α-helical coiled-coil to extended ß-sheet rather than of entropic (rubber) elasticity. We report here the characterization of the precursor proteins that make up this material. Three different proteins have been purified and analyzed, and complete protein sequences deduced from messenger ribonucleic acid (mRNA) transcripts. Circular dichroism (CD) and Fourier transform infrared (FTIR) spectroscopy indicate that the proteins are strongly α-helical in solution and primary sequence analysis suggests that these proteins have a propensity to form coiled-coils. This is in agreement with previous wide-angle X-ray scattering (WAXS) and solid-state Raman spectroscopic analysis of mature egg capsules.

Accelerating the design of biomimetic materials by integrating RNA-seq with proteomics and materials science.

Efforts to engineer new materials inspired by biological structures are hampered by the lack of genomic data from many model organisms studied in biomimetic research. Here we show that biomimetic engineering can be accelerated by integrating high-throughput RNA-seq with proteomics and advanced materials characterization. This approach can be applied to a broad range of systems, as we illustrate by investigating diverse high-performance biological materials involved in embryo protection, adhesion and predation. In one example, we rapidly engineer recombinant squid sucker ring teeth proteins into a range of structural and functional materials, including nanopatterned surfaces and photo-cross-linked films that exceed the mechanical properties of most natural and synthetic polymers. Integrating RNA-seq with proteomics and materials science facilitates the molecular characterization of natural materials and the effective translation of their molecular designs into a wide range of bio-inspired materials.