The Porifera (sponges) are often regarded as the oldest, extant metazoan phylum, also bearing the ancestral stage for most features occurring in higher animals. The absence of chitin in sponges, except for the wall of peculiar resistance bodies produced by a highly derived fresh-water group, is puzzling, since it points out chitin to be an autapomorphy for a particular sponge family rather than the ancestral condition within the metazoan lineage. By investigating the internal proteinaceous (spongin) skeleton of two demosponges (Aplysina sp. and Verongula gigantea) using a wide array of techniques (Fourier transform infrared (FTIR), Raman, X-ray, Calcofluor White Staining, Immunolabeling, and chitinase test), we show that chitin is a component of the outermost layer (cuticle) of the skeletal fibers of these demosponges. FTIR and Raman spectra, as well as X-ray difractograms consistently revealed that sponge chitin is much closer to the alpha-chitin known from other animals than to beta-chitin. These findings support the view that the occurrence of a chitin-producing system is the ancestral condition in Metazoa, and that the alpha-chitin is the primitive form in animals.

A quench-precipitated sample of highly syndiotactic polypropylene (s-PP) (with 86% fully syndiotactic pentads), which shows an X-ray spectrum near that calculated for an "ideal" orthorhombic C-centered structural model of packing as proposed by Corradini et al. (with chains in a helical (TTGG), conformation), has been analyzed by high-resolution solid-state 13C-NMR spectroscopy. The 13C-NMR CP MAS spectra of this sample, in addition to the resonances already reported in the literature for s-PP (in the B-centered structure), exhibit additional peaks in the regions of the methyl (at 18.9 and 22.4 ppm) and methylene (at 44.9 ppm) groups. It is established that these additional resonances belong indeed to nuclei in well-defined conformational environments fixed in rigid structures placed at the interface of the crystallites and within the strained or disordered area of the crystallites themselves. In particular, the peak at 44.9 ppm in assigned to CH2 carbon atoms in a TX.YG conformational environment, whereas the resonance at 18.9 ppm is assigned to CH3 in trans-planar portions of the chain (y-gauche effect). This indicates local disorder in the C-centered crystalline s-PP sample, aue to the presence of conformationally disordered chains. Models of s-PP chains comprising defective but energetically feasible portions of chains in a trans-planar conformation (disturbing the ('M'GG)n dominating conformation) are imagined as packed according to a C-pseudocentered structure. In order to keep the methyl groups in a crystalline register and the chains well interdigitated, the defects should be clustered on planes which cross 3D ordered portions in the crystals. The chemical shiRs of the carbon atoms in the regions comprising the defect for model chains have been calculated on an ab initio level through the IGLO method, and the results are compared with the experiments. The calculations provide a good explanation of the peculiarities of the experimental 13C-NMR spectra of the s-PP sample under study. Thus, detailed information on chain defects can be obtained by combining X-ray scattering, solid-state NMR, and computer simulations.

The skeletons of demosponges, such as Ianthella basta, are known to be a composite material containing organic constituents. Here, we show that a filigree chitin-based scaffold is an integral component of the I. basta skeleton. These chitin-based scaffolds can be isolated from the sponge skeletons using an isolation and purification technique based on treatment with alkaline solutions. Solid-state 13 C NMR, Raman, and FT-IR spectroscopies, as well as chitinase digestion, reveal that the isolated material indeed consists of chitin. The morphology of the scaffolds has been determined by light and electron microscopy. It consists of cross-linked chitin fibers approximately 40-100 nm in diameter forming a micro-structured network. The overall shape of this network closely resembles the shape of the integer sponge skeleton. Solid-state 13 C NMR spectroscopy was used to characterize the sponge skeleton on a molecular level. The 13 C NMR signals of the chitin-based scaffolds are relatively broad, indicating a high amount of disordered chitin, possibly in the form of surfaceexposed molecules. X-ray diffraction confirms that the scaffolds isolated from I. basta consist of partially disordered and loosely packed chitin with large surfaces. The spectroscopic signature of these chitin-based scaffolds is closer to that of α-chitin than β-chitin.

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Sponges are probably the earliest branching animals, and their fossil record dates back to the Precambrian. Identifying their skeletal structure and composition is thus a crucial step in improving our understanding of the early evolution of metazoans. Here, we present the discovery of 505–million-year-old chitin, found in exceptionally well preserved Vauxia gracilenta sponges from the Middle Cambrian Burgess Shale. Our new findings indicate that, given the right fossilization conditions, chitin is stable for much longer than previously suspected. The preservation of chitin in these fossils opens new avenues for research into other ancient fossil groups.

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Biological materials are a rewarding area of modern materials science, yielding both evolutionary insights and inspiration for biomimetic research. In particular, biocomposite structures are valuable sources of novel structures with unusual chemical properties, and they are very informative for the mechanisms of biomineralization. Here we describe a unique biocomposite of amorphous silica, crystalline aragonite, and chitin from species of the order Verongida, a group of marine sponges. The structures have been analyzed with a diverse suite of techniques, revealing a chitinous template for siliceous overgrowth containing aragonite-based crystal aggregates. Sponge chitin is an example of a specific template where two minerals in amorphous and crystalline forms are formed together with an organic molecule.