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Chitin, the most abundant aminopolysaccharide in nature, is an extracellular polymer consisting of N-acetylglucosamine (GlcNAc) units 1 . The key reactions of chitin biosynthesis are catalysed by chitin synthase 2-4 , a membrane-integrated glycosyltransferase that transfers GlcNAc from UDP-GlcNAc to a growing chitin chain. However, the precise mechanism of this process has yet to be elucidated. Here we report five cryo-electron microscopy structures of a chitin synthase from the devastating soybean root rot pathogenic oomycete Phytophthora sojae (PsChs1). They represent the apo, GlcNAc-bound, nascent chitin oligomer-bound, UDP-bound (post-synthesis) and chitin synthase inhibitor nikkomycin Z-bound states of the enzyme, providing detailed views into the multiple steps of chitin biosynthesis and its competitive inhibition. The structures reveal the chitin synthesis reaction chamber that has the substrate-binding site, the catalytic centre and the entrance to the polymer-translocating channel that allows the product polymer to be discharged. This arrangement reflects consecutive key events in chitin biosynthesis from UDP-GlcNAc binding and polymer elongation to the release of the product. We identified a swinging loop within the chitin-translocating channel, which acts as a 'gate lock' that prevents the substrate from leaving while directing the product polymer into the translocating channel for discharge to the extracellular side of the cell membrane. This work reveals the directional multistep mechanism of chitin biosynthesis and provides a structural basis for inhibition of chitin synthesis., (© 2022. The Author(s).)

In this paper, chitooligosaccharides in different salt forms, such as chitooligosaccharide lactate, citrate, adipate, etc., were prepared by the microwave method. They were characterized by SEM, FTIR, NMR, etc., and the nitric oxide (NO) expression was determined in RAW 264.7 cells. The results showed that pure chitooligosaccharide was an irregular spherical shape with rough surface, and its different salt type products are amorphous solid with different honeycomb sizes. In addition to the characteristic absorption peaks of chitooligosaccharides, in FTIR, the characteristic absorption of carboxyl group, methylene group, and aromatic group in corresponding acid appeared. The characteristic absorption peaks of carbon in carboxyl group, hydrogen and carbon in methyl, methylene group, and aromatic group in corresponding acid also appeared in NMR. Therefore, the sugar ring structure and linking mode of chitooligosaccharides did not change after salt formation of chitooligosaccharides. Different salt chitooligosaccharides are completely different in promoting NO secretion by macrophages, and pure chitooligosaccharides are the best.

Chitin is the second most abundant biopolymer and functions as the main structural component in a variety of living organisms. In nature, chitin rarely occurs in a pure form, but rather as nanoorganized chitin-proteins, chitin-pigments, or chitin-mineral composite biomaterials. Although chitin has a long history of scientific studies, it is still extensively investigated for practical applications in medicine, biotechnology, and biomimetics. The complexity of chitin has required the development of highly sensitive analytical methods for its identification. These methods are crucial for furthering disease diagnostics as well as advancing modern chitin-related technologies. Here we provide a summary of chitin identification by spectroscopic (NEXAFS, FTIR, Raman, NMR, colorimetry), chromatographic (TLC, GC, HPLC), electrophoretic (HPCE), and diffraction methods (XRD, WAXS, SAXS, HRTEM-SAED). Biochemical and immunochemical (ELISA, immunostaining) methods are described with respect to their medical application. This review outlines the history as well as the current progress in the analytical methods for chitin identification., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Benthic foraminifera, members of Rhizaria, inhabit a broad range of marine environments and are particularly common in hypoxic sediments. The biology of benthic foraminifera is key to understanding benthic ecosystems and relevant biogeochemical cycles, especially in hypoxic environments. Chilostomella is a foraminiferal genus commonly found in hypoxic deep-sea sediments and has poorly understood ecological characteristics. For example, the carbon isotopic compositions of their lipids are substantially different from other co-occurring genera, probably reflecting unique features of its metabolism. Here, we investigated the cytoplasmic and ultrastructural features of Chilostomella ovoidea from bathyal sediments of Sagami Bay, Japan, based on serial semi-thin sections examined using an optical microscope followed by a three-dimensional reconstruction, combined with TEM observations of ultra-thin sections. Observations by TEM revealed the presence of abundant electron-dense structures dividing the cytoplasm. Based on histochemical staining, these structures are shown to be composed of chitin. Our 3D reconstruction revealed chitinous structures in the final seven chambers. These exhibited a plate-like morphology in the final chambers but became rolled up in earlier chambers (toward the proloculus). These chitinous, plate-like structures may function to partition the cytoplasm in a chamber to increase the surface/volume ratio and/or act as a reactive site for some metabolic functions., (© 2020 The Authors. Journal of Eukaryotic Microbiology published by Wiley Periodicals LLC on behalf of International Society of Protistologists.)

Chitin was collected and extracted along different lifecycle stages of the Black Soldier Fly (BSF) (larvae, prepupae, pupae, flies, shedding & cocoons). The chitin content in the collected biomass ranged between 8% and 24%, with sheddings and cocoons being most rich in chitin. Purified chitin was subjected to a physicochemical evaluation based on FTIR, XRD, and TGA as well as a deacetylation step. The data indicated that BSF chitin was α-chitin with FTIR profiles matching closely to shrimp chitin and showing some differences compared to squid pen chitin (β-chitin). Small physicochemical differences were observed among the different BSF samples. Prepupae and cocoon chitin was more crystalline while chitin from larvae and sheddings had a lower thermal degradation temperature. In addition, sheddings were more difficult to purify. Further processing to chitosan showed that a deacetylation degree of 89% could be obtained for all samples after 3 h, although sheddings were found to be less reactive in the deacetylation process. Overall, the small differences in physicochemical properties that were detected between the BSF chitin samples did not prevent further processing of chitin to chitosan with the same degree of deacetylation via the same treatment., (Copyright © 2020 The Authors. Published by Elsevier B.V. All rights reserved.)

The random discharge of marine fish waste into the coast generates environmental pollution. However, a better valorization of these by-products leads to the extraction of sustainable biomolecules. Chitosan is a natural biopolymer that can be produced from various marine by-products, in particular the crustacean shells, crabs, and fish scales. The aim of this current study is the extraction of chitin and characterization of chitosan obtained after a deacetylation reaction from sardine scales ( S. pilchardus) as a new marine source. The β form of chitin extracted undergoes deacetylation in 40% NaOH at 121°C for 20 min. The chemical structure of obtained chitosan was characterized based on Fourier transforms infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), Scanning electron microscope (SEM), and Energy-dispersive X-ray spectroscopy (EDS). The physicochemical properties of obtained chitosan such as the ash, moisture, nitrogen, solubility, molecular weight, fat, and water-binding capacity were also determined. According to the results of FTIR and XRD analysis, the degree of deacetylation (DDA), and the crystalline index (CrI) value of obtained chitosan is respectively about 87% and 95%. The SEM and EDS analysis revealed respectively fibrillar and pleated morphology with the presence of three major elements characterizing the chitosan, which are C, O, and N. The physicochemical analysis showed that the rate of ash, moisture, and nitrogen in obtained chitosan were respectively about 0.10, 0.34, and 7%. The solubility, molecular weight, fat, and water-binding capacity of produced chitosan were found to be 93%, 5.86 kDa, 310, and 510% respectively. Sardina pilchardus scales could be considered a promising and alternative source of chitin and chitosan, which will be applicable in a large number of fields. Implications : Direct rejection of marine biowaste as fish scales in nature, port, or fish processing plants, is a dramatic problem that is growing day after day. These uncontrollable discharges cause marine pollution and promote bacterial growth, which leads to a degradation of the soil and air quality. Taking into account the objectives of sustainable development, better development of these by-products would make it possible to produce valuable biomaterials that will be applied in various fields and which have benefits for the environment and humans. The central objective of this research is accentuated on the enhancement of Sardina pilchardus scales; by the conversion of chitin into chitosan and the determination of its physicochemical characterization. The obtained chitosan from Sardina pilchardus scales could be applied in the agricultural and food industry.

Biomineralization by living organisms are common phenomena observed everywhere. Molluskan shells are representative biominerals that have fine microstructures with controlled morphology, polymorph, and orientation of CaCO 3 crystals. A few organic molecules involved in the biominerals play important roles in the formation of such microstructures. Analyses of structure-function relationships for matrix proteins in biominerals revealed that almost all matrix proteins have an acidic region for the binding of calcium ion in CaCO 3 crystals and interaction domains for other organic molecules. On the other hand, biomineralization of metal nanoparticles by microorganisms were also investigated. Gold nanoparticles and quantum dots containing cadmium were successfully synthesized by bacteria or a fungus. The analyses of components revealed that glycolipids, oligosaccharides, and lactic acids have key roles to synthesize the gold nanoparticle in Lactobacillus casei as reductants and dispersants. These researches about biomineralization will give new insights for material and environmental sciences in the human society.

The biopolymer α-chitin is a promising raw source that can be used as a low-cost material for environmental applications. Nevertheless, its low surface properties and high crystallinity limit its use. Recent developments include surface modification as one of the most promising strategies for the application of α-chitin. To this end, we used an acidic treatment, followed by ultrasonication, to modify the α-chitin surface and improve its sorption characteristics to achieve the above goal. Structural analysis and measurement of the physicochemical properties (chemical structure and thermal degradation) of α-chitin, before and after surface modification, indicated no significant changes. However, specific surface area, morphology, surface charge, crystallinity and study of the sorption of methylene blue (MB) from aqueous solution demonstrated surface modification. It was established that the S BET of modified α-chitin increased to 110.7 m 2 /g and the crystallinity index decreased to 48%. Interestingly, the modified α-chitin could easily adsorb organic dye from an aqueous solution. The experimental adsorption capacity of the resulting α-chitin after surface modification reached the value of about 95 mg/g., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Chitins were extracted from large insect species of order Coleoptera (Lucanus cervus (Linnaeus, 1758) (Lucanidae) and Polyphylla fullo (Linnaeus, 1758) (Scarabaeidae) and order Orthoptera (Bradyporus (Callimenus) sureyai Ünal, 2011) (Tettigonidae) and Gryllotalpa gryllotalpa (Linnaeus, 1758) (Gryllotalpidae)) for the first time. Fourier Transform Infrared Spectrometry (FT-IR) confirms that isolation of chitin is successful. Yields of chitins on dry basis from P. fullo, L. cervus, G. gryllotalpa and B. (C.) sureyai are 11.3%, 10.9%, 10.1% and 9.8% respectively. Thermogravimetric Analysis (TGA) showed a variety of thermal stability of chitin samples from 614 °C to 748 °C with a small percent of ash. X-ray diffraction (XRD) data showed a crystallinity index percent from 80.6% to 85.2%. Scanning Electron Microscope (SEM) was examined for surface characterization determining as fibrous and porous for all species and changes from nm scales to μm scales. Elemental analysis has been applied to determine the elemental composition of chitin and nitrogen percent was relatively low for all specimens than expected. It is detected that examined insects have α-chitin form from XRD and FT-IR data. If these species can be grown in the laboratory, adults of them could be accepted as promising alternative chitin sources without negative effects on biodiversity., Competing Interests: Declaration of competing interest The authors declare no competing financial interest., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Sapphirinid copepods, which are marine zooplankton, exhibit tunable structural colors originating from a layered structure of guanine crystal plates. In the present study, the coloring portion of adult male of a sapphirinid copepod, Sapphirina nigromaculata, under the dorsal body surface was characterized to clarify the regulation and actuation mechanism of the layered guanine crystals for spectral control. The coloring portions are separated into small domains 70-100 µm wide consisting of an ordered array of stacked hexagonal plates ~1.5 µm wide and ~80 nm thick. We found the presence of chitin-based honeycomb frameworks that are composed of flat compartments regulating the guanine crystal plates. The structural color is deduced to be tuned from blue to achromatic via yellow and purple by changing the interplate distance according to vital observation and optical simulation using a photonic array model. The framework structures are essential for the organization and actuation of the particular photonic arrays for the exhibition of the tunable structural color.

Helicoidal formations often appear in natural microstructures such as bones and arthropods exoskeletons. Named Bouligands after their discoverer, these structures are angle-ply laminates that assemble from laminae of chitin or collagen fibers embedded in a proteinaceous matrix. High resolution electron microscope images of cross-sections through scorpion claws are presented here, uncovering structural features that are different than so-far assumed. These include in-plane twisting of laminae around their corners rather than through their centers, and a second orthogonal rotation angle which gradually tilts the laminae out-of-plane. The resulting Bouligand laminate unit (BLU) is highly warped, such that neighboring BLUs are intricately intertwined, tightly nested and mechanically interlocked. Using classical laminate analysis extended to laminae tilting, it is shown that tilting significantly enhances the laminate flexural stiffness and strength, and may improve toughness by diverting crack propagation. These observations may be extended to diverse biological species and potentially applied to synthetic structures.

Vertebrates and insects are phylogenetically separated by millions of years but have commonly developed tympanal membranes for efficiently converting airborne sound to mechanical oscillation in hearing. The tympanal organ of the field cricket Gryllus bimaculatus, spanning 200 μm, is one of the smallest auditory organs among animals. It indirectly links to two tympana in the prothoracic tibia via tracheal vesicles. The anterior tympanal membrane is smaller and thicker than the posterior tympanal membrane and it is thought to have minor function as a sound receiver. Using differential labeling of sensory neurons/surrounding structures and three-dimensional reconstructions, we revealed that a shell-shaped chitin mass and associated tissues are hidden behind the anterior tympanal membrane. The mass, termed the epithelial core, is progressively enlarged by discharge of cylindrical chitin from epithelial cells that start to aggregate immediately after the final molt and it reaches a plateau in size after 6 days. The core, bridging between the anterior tracheal vesicle and the fluid-filled chamber containing sensory neurons, is supported by a taut membrane, suggesting the possibility that anterior displacements of the anterior tracheal vesicle are converted into fluid motion via a lever action of the core. The epithelial core did not exist in tympanal organ homologs of meso- and metathoracic legs or of nymphal legs. Taken together, the findings suggest that the epithelial core, a potential functional homolog to mammalian ossicles, underlies fine sound frequency discrimination required for adult-specific sound communications.

Although collagens from vertebrates are mainly used in regenerative medicine, the most elusive issue in the collagen-based biomedical scaffolds is its insufficient mechanical strength. To solve this problem, electrospun collagen composites with chitins were prepared and molecular interactions which are the cause of the mechanical improvement in the composites were investigated by two-dimensional correlation spectroscopy (2DCOS). The electrospun collagen is composed of two kinds of polymorphs, α- and β-chitin, showing different mechanical enhancement and molecular interactions due to different inherent configurations in the crystal structure, resulting in solvent and polymer susceptibility. The collagen/α-chitin has two distinctive phases in the composite, but β-chitin composite has a relatively homogeneous phase. The β-chitin composite showed better tensile strength with ~41% and ~14% higher strength compared to collagen and α-chitin composites, respectively, due to a favorable secondary interaction, i.e., inter- rather than intra-molecular hydrogen bonds. The revealed molecular interaction indicates that β-chitin prefers to form inter-molecular hydrogen bonds with collagen by rearranging their uncrumpled crystalline regions, unlike α-chitin.

The bioactive bromotyrosine-derived alkaloids and unique morphologically-defined fibrous skeleton of chitin origin have been found recently in marine demosponges of the order Verongiida. The sophisticated three-dimensional (3D) structure of skeletal chitinous scaffolds supported their use in biomedicine, tissue engineering as well as in diverse modern technologies. The goal of this study was the screening of new species of the order Verongiida to find another renewable source of naturally prefabricated 3D chitinous scaffolds. Special attention was paid to demosponge species, which could be farmed on large scale using marine aquaculture methods. In this study, the demosponge Pseudoceratina arabica collected in the coastal waters of the Egyptian Red Sea was examined as a potential source of chitin for the first time. Various bioanalytical tools including scanning electron microscopy (SEM), fluorescence microscopy, FTIR analysis, Calcofluor white staining, electrospray ionization mass spectrometry (ESI-MS), as well as a chitinase digestion assay were successfully used to confirm the discovery of α-chitin within the skeleton of P. arabica . The current finding should make an important contribution to the field of application of this verongiid sponge as a novel renewable source of biologically-active metabolites and chitin, which are important for development of the blue biotechnology especially in marine oriented biomedicine.

Bivalve shells are inorganic-organic nanocomposites whose material properties outperform their purely inorganic mineral counterparts. Most typically the inorganic phase is a polymorph of CaCO 3 , while the organic phase contains biopolymers which have been presumed to be chitin and/or proteins. Identifying the biopolymer phase is therefore a crucial step in improving our understanding of design principles relevant to biominerals. In this work we study seven shells; four are examples of nacroprismatic shells (Alathyria jacksoni, Pinctada maxima, Hyriopsis cumingii and Cucumerunio novaehollandiae), one homogeneous (Arctica islandica), and two are crossed lamellar (Callista kingii, Tridacna gigas). Both intact shells, their organic extracts as isolated after decalcification in acid, and the periostracum overlay have been studied by solid-state CP-MAS NMR, FTIR, SEM and chemical analysis. In none of the shells examined in this work do we find a significant contribution to the organic fraction from chitin or its derivatives despite popular models of bivalve biomineralization which assume abundant chitin in the organic fraction of mollusk bivalve shells. In each of the nacroprismatic extracts the 13 C NMR spectra represent similar proteinaceous material, Ala and Gly-rich and primarily organized as β-sheets. A different, yet highly conserved protein was found in the periostracum covering each of the three nacreous shells studied. The Arctica islandica shells with homogeneous microstructure contained proteins which do not appear to be silk-like, while in the crossed lamellar shells we extracted too little organic matter to characterize. STATEMENT OF SIGNIFICANCE: Hydrophobic macromolecules are structural components within the calcareous inorganic matrix of bivalve shells and are responsible for enhanced materials properties of the biominerals. Prevalent models suggest that chitin is such major hydrophobic component. Contrary to that we show that chitin is rare within the hydrophobic biopolymers which primarily consist of proteinaceous matter with structural motifs as silk-like β-sheets, or others yet to be determined. Recognizing that diverse proteinaceous motifs, devoid of abundant chitin, can yield the optimized mechanical properties of bivalve shells is critical both to understand the mechanistic pathways by which they regulate biomineralization and for the design of novel bioinspired materials., (Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

Among marine demosponges (Porifera: Demospongiae), only representatives of the order Verongiida have been recognized to synthetize both biologically active substances as well as scaffolds-like fibrous skeletons made of structural aminopolysaccharide chitin. The unique 3D architecture of such scaffolds open perspectives for their applications in waste treatment, biomimetics and tissue engineering. Here, we focus special attention to the demosponge Pseudoceratina purpurea collected in the coastal waters of Singapore. For the first time the detailed description of the isolation of chitin from the skeleton of this sponge and its identification using diverse bioanalytical tools were carried out. Calcofluor white staining, FTIR analysis, electrospray ionization mass spectrometry (ESI-MS), SEM, and fluorescence microscopy as well as a chitinase digestion assay were applied in order to confirm with strong evidence the finding of alpha-chitin in the skeleton of P. purpurea. We suggest that the discovery of chitin within representatives of Pseudoceratinidae family is a perspective step in evaluation of these verongiid sponges as novel renewable sources for both chitin and biologically active metabolites, which are of prospective use for marine oriented biomedicine and pharmacology, respectively., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Natural and synthetic chitin films, obtained from the same source were produced and their physicochemical properties were examined comparatively. Firstly, natural chitin film was obtained from elytra of an insect (Oryctes nasicornis L.) and purity of the obtained chitin film (degree of acetylation: 79±2%) was demonstrated by solid state 13 C nuclear magnetic resonance ( 13 C NMR). Then, the synthetic film was produced by dissolving of natural chitin film in LiCl-DMAc. The obtained natural and synthetic films were characterized by AFM, TGA, DSC, FTIR, mechanical properties, light transmission and contact angle. The analyses result demonstrated that natural chitin film lost very important properties such as high thermal stability, transparency, nanofibrous nature, tensile strength, Young's modulus and hydrophobicity after transforming the synthetic film., (Copyright © 2017 Elsevier B.V. All rights reserved.)

We determined the crystal structure of a LysM module from Pteris ryukyuensis chitinase-A (PrLysM2) at a resolution of 1.8 Å. Structural and binding analysis of PrLysM2 indicated that this module recognizes chitin oligosaccharides in a shallow groove comprised of five sugar-binding subsites on one side of the molecule. The free energy changes (ΔG r °) for binding of (GlcNAc) 6 , (GlcNAc) 5 , and (GlcNAc) 4 to PrLysM2 were determined to be -5.4, -5,4 and -4.6 kcal mol -1 , respectively, by ITC. Thermodynamic dissection of the binding energetics of (GlcNAc) 6 revealed that the driving force is the enthalpy change (ΔH r ° = -11.7 ± 0.2 kcal/mol) and the solvation entropy change (-TΔS solv ° = -5.9 ± 0.6 kcal/mol). This is the first description of thermodynamic signatures of a chitin oligosaccharide binding to a LysM module., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Biomineralization, in which organisms create biogenic hard tissues, with hardness or flexibility enhanced by organic-inorganic interaction is an interesting and attractive focus for application of biomimetic functional materials. Calcites in the prismatic layer of Pinctada fucata are tougher than abiotic calcites due to small crystal defects. However, the molecular mechanism of the defect formation remains unclear. Here, chitin and two chitinolytic enzymes, chitinase and chitobiase, were identified as organic matrices related to for the formation of small crystal defects in the prismatic layer. Experiments with a chitinase inhibitor in vivo showed chitinase is necessary to form the prismatic layer. Analysis of calcite crystals, which were synthesized in a chitin hydrogel treated with chitinolytic enzymes, by electron microscopy and X-ray diffraction showed that crystal defects became larger as chitin was more degraded. These results suggest that interactions between chitin and calcium carbonate increase as chitin is thinner., (Copyright © 2017. Published by Elsevier Inc.)

The nanostructures on the wings of Idea malabarica (Moore, 1877) were analysed using scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, Fourier transform-infrared spectroscopy, and reflectance measurements. The chemical and morphological analyses revealed the chitin-based intricate nanostructures. The influence of the nanostructures on the wetting characteristics of the wing was investigated using optical imaging. Applying the Maxwell-Garnet approximation to the porosities within the nanostructures, the refractive indices, which relate the reflectance response, were estimated. It was concluded that the colour seen on the wings of the Idea malabarica originate from the nanostructural configurations of the chitin-based structures and the embedded pigment.

This is the first report on the physicochemical properties of chitin obtained from larvae and imagoes of black soldier flies (Hermetia illucens). Scanning electron microscopy revealed differences in surface morphologies of the two types of chitin. The crystalline index values of chitins from adult flies and larvae were 24.9% and 35%, respectively. This is a trait that differentiates these biopolymers from chitins extracted from other sources described so far. X-ray diffraction patterns and IR spectroscopy revealed that both types of samples of chitin were in an α crystalline form. Also, the results of elemental analysis, thermal stabilities and FTIR spectroscopy of the chitins from larvae and adults of H. illucens were similar, which points to a general similarity in their physicochemical structure., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Chitin is a carbohydrate polymer with unique pharmacological and immunological properties, however, because of its unwieldy chemistry, the synthesis of discreet sized sub-micron particles has not been well reported. This work describes a facile and flexible method to fabricate biocompatible chitin and dibutyrylchitin sub-micron particles. This technique is based on an oil-in-water emulsification/evaporation method and involves the hydrophobization of chitin by the addition of labile butyryl groups onto chitin, disrupting intermolecular hydrogen bonds and enabling solubility in the organic solvent used as the oil phase during fabrication. The subsequent removal of butyryl groups post-fabrication through alkaline saponification regenerates native chitin while keeping particles morphology intact. Examples of encapsulation of hydrophobic dyes and nanocrystals are demonstrated, specifically using iron oxide nanocrystals and coumarin 6. The prepared particles had diameters between 300-400nm for dibutyrylchitin and 500-600nm for chitin and were highly cytocompatible. Moreover, they were able to encapsulate high amounts of iron oxide nanocrystals and were able to label mammalian cells., Statement of Significance: We describe a technique to prepare sub-micron particles of highly acetylated chitin (>90%) and dibutyrylchitin and demonstrate their utility as carriers for imaging. Chitin is a polysaccharide capable of stimulating the immune system, a property that depends on the acetamide groups, but its insolubility limits its use. No method for sub-micron particle preparation with highly acetylated chitins have been published. The only approach for the preparation of sub-micron particles uses low acetylation chitins. Dibutyrylchitin, a soluble chitin derivative, was used to prepare particles by oil in water emulsification. Butyryl groups were then removed, forming chitin particles. These particles could be suitable for encapsulation of hydrophobic payloads for drug delivery and cell imaging, as well as, adjuvants for vaccines., (Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.)

The relationship between purification methods of β-chitin from squid pen and the physicochemical properties of β-chitin nanofibers (NFs) were investigated. Two types of β-chitin were prepared, with β-chitin (a→b) subjected to acid treatment for decalcification and then base treatment for deproteinization, while β-chitin (b→a) was treated in the opposite order. These β-chitins were disintegrated into NFs using wet pulverization. The β-chitin (b→a) NF dispersion has higher transmittance and viscosity than the β-chitin (a→b) NF dispersion. For the first time, we succeeded in obtaining 3D images of the β-chitin NF dispersion in water by using quick-freeze deep-etch replication with high-angle annular dark field scanning transmission electron microscopy. The β-chitin (b→a) NF dispersion has a denser and more uniform 3D network structure than the β-chitin (a→b) NF dispersion. Widths of the β-chitin (a→b) and (b→a) NFs were approximately 8-25 and 3-10nm, respectively., (Copyright © 2016 Elsevier B.V. All rights reserved.)

This is the first study to explain the differences in the physicochemical properties of chitin and chitosan obtained from the nymphs and adults of Dociostaurus maroccanus using the same method. Fourier transform infrared spectroscopy, thermogravimetric analysis and x-ray diffraction analysis results demonstrated that the chitins from both the adults and nymphs were in the α-form. The chitin contents of the adults (14%) and nymphs (12%) were of the same order of magnitude. The crystalline index values of chitins from the adult and nymph grasshoppers were 71% and 74%, respectively. Thermal stabilities of the chitins and chitosans from adult and nymph grasshoppers were close to each other. Both the adult (7.2kDa) and nymph (5.6kDa) chitosans had low molar masses. Environmental scanning electron microscopy revealed that the surface morphologies of both chitins consisted of nanofibers and nanopores together, and they were very similar to each other. Consequently, it was determined that the physicochemical properties of the chitins and chitosans from adults and nymphs of D. maroccanus were not very different, so it can be hypothesized that the development of the chitin structure in the nymph has almost been completed and the nymph chitin has the same characteristics as the adult., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Curculio longinasus Chittenden, 1927 (Coleoptera: Curculionidae), is a weevil species common throughout the southwestern United States that uses its rostrum - a very slender, curved, beak-like projection of the head - to excavate tunnels in plant organs (such as acorns) for egg laying (oviposition). Once the apical portion of the rostrum has been inserted into the preferred substrate for oviposition, the female begins rotating around the perimeter of the hole, elevating her head by extending the fore-legs, and rotating the head in place in a drilling motion. This action causes significant elastic deformation of the rostrum, which will bend until it becomes completely straight. To better understand the mechanical behavior of the cuticle as it undergoes deformation during the preparation of oviposition sites, we develop a comprehensive micro/macro model of the micromechanical structure and properties of the cuticle, spanning across all cuticular regions, and reliably mirroring the resultant macroscale properties of the cuticle. Our modeling approach relies on the use of multi-scale, hierarchical biomaterial representation, and employs various micromechanical schemata - e.g., Mori-Tanaka, effective field, and Maxwell - to calculate the homogenized properties of representative volume elements at each level in the hierarchy. We describe the configuration and behavior of this model in detail, and discuss the theoretical implications and limitations of this approach with emphasis on future biomechanical and comparative evolutionary research. Our detailed account of this approach can thereby serve as a methodological template for exploring the biomechanical behavior of new insect structures., (Copyright © 2016. Published by Elsevier Inc.)

Chitin in the compound eyes of arthropods serves as a part of the visual system. The quality of chitin in such highly specialised body parts deserves more detailed examination. Chitin in the corneal (ommatidial) lenses of dragonfly (Sympetrum fonscolombii) compound eyes was isolated by using the classical chemical method. The chitin content of the corneal lenses was determined to be quite high (20.3±0.85%). The FT-IR analysis showed that corneal lens chitin was in the α-form as found in all arthropod species where mechanical strength is required. The surface morphology analysis by scanning electron microscopy revealed that the outer part of corneal lenses consisted of long chitin fibrils with regular arrays of papillary structures while the smoother inner part had concentric lamellated chitin formation with shorter chitin nanofibrils. Chitinase enzymatic digestion studies, elemental analysis results and the degree of acetylation value showed the purity of chitin samples from corneal lens. The maximum degradation temperature value of the corneal lens chitin was observed at 369.2°C. X-ray analysis revealed that corneal lens chitin has high crystallinity index; 96.4%. Identification of chitin found in ommaditia of insect compound eyes can provide insights into insect vision and chitin-based optical material design studies., (Copyright © 2016 Elsevier B.V. All rights reserved.)

It is already known that chitin in a single organism can exhibit huge differences depending on the functions it serves in different body parts, but the alterations in the characteristics of chitin in course of developmental stages of an organism still remain unknown. This study presents findings on how chitin matrix is changing physicochemically through discrete morphological stages - larva, pupa and adult - of an insect (Vespa crabro). Chitin content of the organisms were found to increase gradually as the organism grew; 2.1, 6.2 and 10.3%, with a dramatic increase in chitin deposition (nearly 3 folds) during the instar from larva to pupa. Enzymatic digestion test demonstrated that chitin isolates were close to pure. Chitin isolates were also subjected to thermal pyrolysis and no variations were observed in the thermal stability of the samples. However, it was observed that surface characteristics of chitin changed greatly as the insect grew., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The complex hierarchical structure in biological and synthetic fibrous nanocomposites entails considerable difficulties in the interpretation of the crystallographic texture from diffraction data. Here, we present a novel reconstruction method to obtain the 3D distribution of fibres in such systems. An analytical expression is derived for the diffraction intensity from fibres, explaining the azimuthal intensity distribution in terms of the angles of the three dimensional fibre orientation distributions. The telson of stomatopod (mantis shrimp) serves as an example of natural biological armour whose high impact resistance property is believed to arise from the hierarchical organization of alpha chitin nanofibrils into fibres and twisted plywood (Bouligand) structures at the sub-micron and micron scale. Synchrotron microfocus scanning X-ray diffraction data on stomatopod telson were used as a test case to map the 3D fibre orientation across the entire tissue section. The method is applicable to a range of biological and biomimetic structures with graded 3D fibre texture at the sub-micron and micron length scales.

A generic character of the genus Spiophanes (Annelida, Sedentaria: Spionidae) is the presence of parapodial glandular organs. Parapodial glandular organs in Spiophanes species include secretory cells with cup-shaped microvilli, similar to those present in deep-sea inhabiting vestimentiferans and frenulate Siboglinidae. These cells are supposed to secrete β-chitin for tube-building. In this study, transverse histological and/or ultrathin sections of parapodial glandular organs and tubes of Spiophanes spp. as well as of Glandulospio orestes (Spionidae) and Owenia fusiformis (Oweniidae) were examined. Fluorescent markers together with confocal laser scanning microscopy, and Raman spectroscopy were used to detect chitin in the parapodial glandular organs of Spiophanes and/or in the glands of Owenia and Glandulospio. Tubes of these taxa were tested for chitin to elucidate the use of it for tube-building. The examinations revealed a distinct labelling of the gland contents. Raman spectroscopy documented the presence of β-chitin in both gland types of Spiophanes. The tubes of Spiophanes were found to have a grid-like structure that seems to be built with this β-chitin. Tests of tubes of Dipolydora quadrilobata (Spionidae) for chitin were negative. However, the results of our study provide strong evidence that Spiophanes species, O. fusiformis and probably also G. orestes produce chitin and supposedly use it for tube-building. This implies that the production of chitin and its use as a constituent part of tube-building is more widespread among polychaetes as yet known. The histochemical data presented in this study support previous assumptions inferring homology of parapodial glandular organs of Spionidae and Siboglinidae based on ultrastructure. Furthermore, transmission electron microscopy-based evidence of secretory cells with nail-headed microvilli in O. fusiformis suggests homology of parapodial grandular organs across annelids including Sipuncula., (© 2015 Wiley Periodicals, Inc.)

It is well known that physicochemical properties of chitin are related with the extraction method. Recently, it was revealed that some physicochemical properties of chitin are also related with taxonomical relationship. For the first time in this study, it was tested how these properties of chitin are affected by different body parts of one organism. The chitins were extracted from five different body parts (head, thorax, abdomen, legs and wings) of honeybee. These chitins were physicochemically characterized and differences among these body parts were identified. Highest chitin content was observed in legs (13.25%) while the lowest from thorax (6.79%). The surface morphologies of the isolated chitin structures from five different body parts were analyzed with SEM, as a result, five different types of surface morphologies were recorded. However, three different types of surface morphologies were observed only in abdomen. Maximum degradation temperatures (DTG(max)) of thorax, abdomen, legs and wings were recorded between 359 and 367 °C while DTG(max) value of head chitin was found as 308 °C., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

This study was conducted to understand the differences in the physicochemical properties of chitin samples isolated from the wings and the other body parts except the wings (OBP) of a butterfly species (Argynnis pandora). The same isolation method was used for obtaining chitin specimens from both types of body parts. The chitin content of the wings (22%) was recorded as being much higher than the OBP (8%). The extracted chitin samples were characterized via FT-IR, TGA, XRD, SEM, and elemental analysis techniques. Results of these characterizations revealed that the chitins from both structures (wings and OBP) were very similar, except for their surface morphologies. SEM results demonstrated one type of surface morphology for the wings and four different surface morphologies for the OBP. Therefore, it can be hypothesized that the surface morphology of the chitin is highly related with the body part., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A large amount of granular protrusions overlie the outer cell wall surfaces in both elongating and non-elongating stipe regions but overlie the inner cell wall surfaces only in non-elongating stipe regions. Removal of granular protrusions using alkali, amorphous materials overlying on both the inner and outer cell wall surfaces were explored in the non-elongating stipe regions. β-1,3-Glucanase treatment not only removed above those granular protrusions and underlying amorphous materials on the wall surfaces but also removed wall matrices embedding chitin microfibrils on the cell walls of most stipe regions, except for the outer cell wall surfaces of the non-elongating stipe regions where most of the wall matrices remained. The chitin microfibrils were closely and transversely arranged on both the inner and outer cell wall surfaces in the elongating apical stipe region, whereas they were loosely and transversely arranged on the inner cell wall surfaces and further became sparser and even randomly arranged on the outer cell wall surface in the non-elongating stipe regions. We propose that the surface deposition of granular protrusions and amorphous materials and the change of microfibril architecture and wall matrices may cause loss of wall plasticity and cessation of stipe elongation., (Copyright © 2015 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.)

Ultrasound-assisted (UA) and supercritical CO2 technologies (SCO2) were used to modify the chitin surface and, improve its adsorption characteristics regarding to cobalt. Chitin, before and after the treatments, was characterized by N2 adsorption isotherms (BET), infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Unmodified and surface modified chitins were used as adsorbents to remove cobalt from aqueous solutions. The adsorption study was performed by equilibrium isotherms and kinetic curves. The chitin particle characteristics, such as, surface area, pore volume and porosity were improved by the UA and SCO2 treatments. The crystallinity index decreased after the UA and SCO2 treatments, and also, intense surface modifications were observed. Langmuir and Freundlich models were adequate to represent the adsorption equilibrium. The maximum adsorption capacities were 50.03, 83.94 and 63.08 mg g(-1) for unmodified chitin, UA surface modified chitin and SCO2 surface modified chitin. The adsorption kinetic curves were well represented by the pseudo-second order model. UA and SCO2 technologies are alternatives to modify the chitin surface and improve its adsorption characteristics., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Chitin and chitosan were obtained by chemical treatments of shrimp shells. Different particle sizes (50-1000 μm) of the raw material were used to study their effect on size distribution, demineralization, deproteinization and deacetylation of chitin and chitosan isolation process. The particle size in the range of 800-1000 μm was selected to isolate chitin, which was achieved by measuring nitrogen, protein, ash, and yield %. Hydrochloric acid (5%, v/v) was optimized in demineralization step to remove the minerals from the starting material. Aqueous solution of sodium hydroxide (5%, w/v) at 90 °C for (20 h) was used in deproteinization step to remove the protein. Pure chitin was consequently impregnated into high concentration of sodium hydroxide (50%) for 3.5 h at 90 °C to remove the acetyl groups in order to form high pure chitosan. The degree of deacetylation (DDA) of chitosan was controlled and evaluated by different analytical tools. The chemical structure of chitin and chitosan was confirmed by elemental analysis, ATR-FTIR, H/C NMR, XRD, SEM, UV-Vis spectroscopy, TGA, and acid-base titration. The isolated chitin and chitosan from shrimp shell showed excellent antibacterial activity against Gram (-ve) bacteria (Escherichia coli) comparing with commercial biopolymers., (Copyright © 2015 Elsevier B.V. All rights reserved.)

There has been no study on the chitin structure of wasp species. Here, we selected the three most common wasp species belonging to the family Vespidae for chitin extraction and characterization. Chitin was isolated from each wasp species and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffractometry (XRD), elemental analysis (EA), and scanning electron microscopy (SEM). The chitin contents of Vespa crabro, Vespa orientalis, and Vespula germanica were 8.3, 6.4, and 11.9%, respectively. The crystalline index (CrI) values for the chitin extracted from each species were 69.88, 53.92, and 50%, respectively. The most important finding of the study is that although the same method was used to extract chitin from each of the three wasp species, the degree of acetylation was different: for V. crabro and V. orientalis it was 96.85 and 99.82% (the chitin was extremely pure), respectively, whereas that for V. germanica the chitin was 79.83%., (© 2015 Wiley Periodicals, Inc.)

The beak of the jumbo squid Dosidicus gigas is a fascinating example of how seamlessly nature builds with mechanically mismatched materials. A 200-fold stiffness gradient begins in the hydrated chitin of the soft beak base and gradually increases to maximum stiffness in the dehydrated distal rostrum. Here, we combined RNA-Seq and proteomics to show that the beak contains two protein families. One family consists of chitin-binding proteins (DgCBPs) that physically join chitin chains, whereas the other family comprises highly modular histidine-rich proteins (DgHBPs). We propose that DgHBPs play multiple key roles during beak bioprocessing, first by forming concentrated coacervate solutions that diffuse into the DgCBP-chitin scaffold, and second by inducing crosslinking via an abundant GHG sequence motif. These processes generate spatially controlled desolvation, resulting in the impressive biomechanical gradient. Our findings provide novel molecular-scale strategies for designing functional gradient materials.

In this study a new morphology of chitin, which could find wide applications in the fields of medicine, pharmacy, agriculture, food and textiles, has been described. The chitin was isolated from the wings of Periplaneta americana employing a conventional method. Considering chitin isolation studies conducted previously, chitin has three surface morphologies, which are (1) hard and rough surface without pores or nanofibers, (2) surface solely composed of nanofibers and (3) surfaces with both pores and nanofibers. In this study, the surface of the chitin, examined with environmental scanning electron microscopy (ESEM), only has oval nanopores (230-510 nm) without nanofibers, and this is different from the above mentioned surface morphologies. The nanopores are not distributed on the chitin surface randomly. Typically, there is a pore in the center that is surrounded by six or seven other pores in an ordered manner. Structures similar to cell walls exist between the pores. Chitin with the new surface morphology was characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), X-ray diffraction (XRD) and elemental analysis., (Copyright © 2015 Elsevier B.V. All rights reserved.)

This study describes the preparation, characterization and performance of a novel excipient for use in oro-dispersible tablets (ODT). The excipient (Cop-CM) consists of chitin and mannitol. The excipient with optimal physicochemical properties was obtained at a chitin: mannitol ratio of 2:8 (w/w) and produced by roll compaction (RC). Differential scanning calorimetry (DSC), Fourier transform-Infrared (FT-IR), X-ray powder diffraction (XRPD) and scanning electron microscope (SEM) techniques were used to characterize Cop-CM, in addition to characterization of its powder and ODT dosage form. The effect of particle size distribution of Cop-CM was investigated and found to have no significant influence on the overall tablet physical properties. The compressibility parameter (a) for Cop-CM was calculated from a Kawakita plot and found to be higher (0.661) than that of mannitol (0.576) due to the presence of the highly compressible chitin (0.818). Montelukast sodium and domperidone ODTs produced, using Cop-CM, displayed excellent physicochemical properties. The exceptional binding, fast wetting and superdisintegration properties of Cop-CM, in comparison with commercially available co-processed ODT excipients, results in a unique multifunctional base which can successfully be used in the formulation of oro-dispersible and fast immediate release tablets.

Insect cuticle is composed mainly of structural proteins and the polysaccharide chitin. The CPR family is the largest family of cuticle proteins (CPs), which can be further divided into three subgroups based on the presence of one of the three presumptive chitin-binding sequence motifs denoted as Rebers-Riddiford (R&R) consensus sequence motifs RR-1, RR-2 and RR-3. The TcCPR27 protein containing the RR-2 motif is one of the most abundant CPs present both in the horizontal laminae and in vertical pore canals in the procuticle of rigid cuticle found in the elytron of the red flour beetle, Tribolium castaneum. Depletion of TcCPR27 by RNA interference (RNAi) causes both unorganized laminae and pore canals, resulting in malformation and weakening of the elytron. In this study, we investigated the function(s) of another CP, TcCPR4, which contains the RR-1 motif and is easily extractable from elytra after RNAi to deplete the level of TcCPR27. Transcript levels of the TcCPR4 gene are dramatically increased in 3 d-old pupae when adult cuticle synthesis begins. Immunohistochemical studies revealed that TcCPR4 protein is present in the rigid cuticles of the dorsal elytron, ventral abdomen and leg but not in the flexible cuticles of the hindwing and dorsal abdomen of adult T. castaneum. Immunogold labeling and transmission electron microscopic analyses revealed that TcCPR4 is predominantly localized in pore canals and regions around the apical plasma membrane protrusions into the procuticle of rigid adult cuticles. RNAi for TcCPR4 resulted in an abnormal shape of the pore canals with amorphous pore canal fibers (PCFs) in their lumen. These results support the hypothesis that TcCPR4 is required for achieving proper morphology of the vertical pore canals and PCFs that contribute to the assembly of a cuticle that is both lightweight and rigid.

Differences in the physichochemical properties of the chitin structure of the exoskeleton of seven species from four genera were investigated in this study. The same method was used to isolate the chitin structure of the seven species. The physicochemical properties of the isolated chitins were revealed by ESEM, FTIR, TGA and XRD analyses. The FTIR, TGA and XRD results from the chitin samples were similar. The surface morphologies of the chitins were investigated by ESEM and interesting results were noted. While the surface morphologies of the chitins isolated from two species within the same genus were quite different, the surface morphologies of chitins isolated from species belonging to different genera showed similarity. It was determined that the dry weight chitin contents of the grasshopper species varied between 5.3% and 8.9%. The results of molecular analysis showed that the chitins from seven Orthoptera species (between 5.2 and 6.8 kDa) have low molecular weights. Considering that these invasive and harmful species are killed with insecticides and go to waste in large amounts, this study suggests that they should be collected and evaluated as an alternative chitin source., (Copyright © 2014 Elsevier B.V. All rights reserved.)

High strength chitin/poly(vinyl alcohol) (PVA) composite hydrogels (RCP) were constructed by adding PVA into chitin dissolved in a NaOH/urea aqueous solution, and then by cross-linking with epichlorohydrin (ECH) and freezing-thawing process. The RCP hydrogels were characterized by field emission scanning electron microscopy, FTIR, differential scanning calorimetry, solid-state (13)C NMR, wide-angle X-ray diffraction, and compressive test. The results revealed that the repeated freezing/thawing cycles induced the bicrosslinked networks consisted of chitin and PVA crystals in the composite gels. Interestingly, a jellyfish gel-like structure occurred in the RCP75 gel with 25 wt % PVA content in which the amorphous and crystalline PVA were immobilized tightly in the chitin matrix through hydrogen bonding interaction. The freezing/thawing cycles played an important role in the formation of the layered porous PVA networks and the tight combining of PVA with the pore wall of chitin. The mechanical properties of RCP75 were much higher than the other RCP gels, and the compressive strength was 20× higher than that of pure chitin gels, as a result of broadly dispersing stress caused by the orderly multilayered networks. Furthermore, the cell culture tests indicated that the chitin/PVA composite hydrogels exhibited excellent biocompatibility and safety, showing potential applications in the field of tissue engineering.

Chitin nanofibers have been prepared from crab shell as a chitin source using ultrasound assisted fibrillation. Atomic force microscopy (AFM) study showed that the prepared nanofibers were having diameters and lengths primarily in the range of 2-20 nm and 0.3-4 μm respectively. These nanofibers were selectively grafted on one side of a 100% cotton fabric using a special apparatus. Prior to the grafting, cotton fabrics were modified with partial carboxymethylation to encourage cotton fiber nanofiber interactions. The surface modification was confirmed by Fourier transform infrared spectroscopy (FT-IR) peaks at 1,594 cm(-1) and 1,735 cm(-1) due to the presence of carboxylic acid functionality in modified cotton fabrics. Scanning electron microscope (SEM) study of the nanofiber grafted cotton fabrics showed that nanofibers were adhered to the cotton fabrics. Elemental analysis confirmed that side selective grafting of nanofiber has taken place due to the peak at 0.394 keV which attributes to the presence of nitrogen element in chitin nanofibers. This peak was absent in the other side of the fabric which was not coated with chitin nanofibers. Amount of adhered nanofibers was seen to increase with the increase of nanofiber concentration used in grafting as confirmed by Kjeldahl analysis. A possible mechanism of cotton fiber-nanofiber interactions is introduced., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The animal immune response to chitin is not well understood and needs to be investigated further. However, this is a challenging topic to study because of the technical difficulties in purifying chitin, and because this material usually comes associated with contaminating components that can activate the immune system. In this study, improvements to previously described purification protocols were investigated for chitin obtained from different sources, including commercial shellfish, Candida albicans yeast and hyphal cell walls, as well as cell walls of the filamentous fungi Aspergillus fumigatus and Mucor circinelloides. The immune response to these different chitin preparations was tested using human peripheral blood mononuclear cells. In agreement with previous literature, small chitin particles of an average size of 0.2 µm were not immunogenic. On the other hand, bigger chitin particles induced in some cases a pro-inflammatory response. The results of this work suggest that not only the purity and size of the chitin particles, but also their shape can influence immune recognition.

The direction of β-chitin deposition in the tube of tubeworm Lamellibrachia satsuma was investigated by texture analysis using X-ray diffraction. The β-chitin crystallite in the tube has planar orientation with the (110) plane perpendicular to the surface, and the c-axis is aligned parallel to the tube. The monoclinic unit cell of β-chitin allowed determination of the sense of c-axis from the orientation of (010) and (100) planes. This means that the reducing end of β-chitin is pointing up in the tube. This orientation can be ascribed to possible secretion mechanisms of the β-chitin microfibrils, i.e. the chitin-synthesizing enzyme complex travels unidirectionally from top to bottom when the worm body contracts in the tube., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Antarctic krill (Euphausia superba) has been widely studied and extensively recognized as a target for commercial fishing. In this study, Antarctic krill chitin was extracted from defatted Antarctic krill shell, and its crystalline structure and thermal properties were characterized by employing Fourier transform infrared spectroscopy, X-ray diffractometry, scanning electron microscopy, thermogravimetry, and differential scanning calorimetry. Results showed that Antarctic krill chitin corresponded to the α-polymorph, and was composed of small, stable, and uniform microcrystals. The degree of N-deacetylation was 11.28 ± 0.86%. The d-spacings of Antarctic krill chitin were 9.78 Å and 4.63 Å at (020) and (110) planes. The crystalline sizes were 6.07 nm and 5.16 nm at (020) and (110) planes, respectively. The activation energy of the polysaccharide chain decomposition was 123.35 kJ/mol and the glass transition (T(g)) of Antarctic krill chitin was 164.96 °C., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The brilliant structural body colours of many animals are created by three-dimensional biological photonic crystals that act as wavelength-specific reflectors. Here, we report a study on the vividly coloured scales of the diamond weevil, Entimus imperialis. Electron microscopy identified the chitin and air assemblies inside the scales as domains of a single-network diamond (Fd3m) photonic crystal. We visualized the topology of the first Brillouin zone (FBZ) by imaging scatterometry, and we reconstructed the complete photonic band structure diagram (PBSD) of the chitinous photonic crystal from reflectance spectra. Comparison with calculated PBSDs indeed showed a perfect overlap. The unique method of non-invasive hemispherical imaging of the FBZ provides key insights for the investigation of photonic crystals in the visible wavelength range. The characterized extremely large biophotonic nanostructures of E. imperialis are structurally optimized for high reflectance and may thus be well suited for use as a template for producing novel photonic devices, e.g. through biomimicry or direct infiltration from dielectric material.

Synthesis and spectroscopic characterization of α-chitins exhibiting degrees of acetylation (DA) between 0.5 and 1 were reported. Crab shell α-chitin consisting of microfibrils with a width of less than 1 μm was regenerated from or alkaline deacetylated in 30% aqueous NaOH solution. After the deacetylation in homogeneous solution, the DA of α-chitins decreased steadily with prolonged deacetylation times from 1 to 0.54. The native microfibrils of starting α-chitin were destroyed, while aggregates or sheets were formed depending on the DA of chitins. According to WAXD measurements, deacetylated chitins with DA lower than 0.76 have different crystalline structures than starting α-chitin. Furthermore, FT Raman spectroscopy demonstrated a novel rapid method to determine the DA of chitin with correlation coefficients greater than 0.99. On the basis of the FT Raman signals ascribed to the amide groups, the amount of hydrogen bonds linked to C═O groups decreased strongly with lower DA and the relationship between them was presented.

Insect chitin was isolated from adult Holotrichia parallela by treatment with 1 M HCl and 1 M NaOH, following by 1% potassium permanganate solution for decolorization. The yield of chitin from this species is 15%. This insect chitin was compared with the commercial a-chitin from shrimp, by infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and elemental analysis. Both chitins exhibited similar chemical structures and physicochemical properties. Adult H. parallela is thus a promising alternative source of chitin.

Using Jamin-Lebedeff interference microscopy, we measured the wavelength dependence of the refractive index of butterfly wing scales and bird feathers. The refractive index values of the glass scales of the butterfly Graphium sarpedon are, at wavelengths 400, 500 and 600 nm, 1.572, 1.552 and 1.541, and those of the feather barbules of the white goose Anas anas domestica are 1.569, 1.556 and 1.548, respectively. The dispersion spectra of the chitin in the butterfly scales and the keratin in the bird barbules are well described by the Cauchy equation n(λ) = A + B/λ(2), with A = 1.517 and B = 8.80·10(3) nm(2) for the butterfly chitin and A = 1.532 and B = 5.89·10(3) nm(2) for the bird keratin., (© 2011 Optical Society of America)