http://www.mtdna.or.kr/neowiz/board/up_files/files_17/Chitin_Chitosan_polymers_chemistrySolubilityFiberFormation.pdf

Chitin and chitosan polymers: Chemistry, solubility and fiber formation

The molecular structure of collagen.

Native cellulose has been shown to consist of a crystalline array of parallel chains, based on the X-ray diffraction data for specimens from the sea alga Valonia ventricosa. The unit cell is monoclinic with dimensions a = 16.34 A, b = 15.72 A, c = 10.38 A (fiber axis), and β = 97.0°. The space group is P21 and the cell contains disaccharide segments of eight chains. Models containing chains with the same sense (parallel) or alternating sense (antiparallel) were refined against the intensity data using rigidbody least squares procedures. The results show a preference for a parallel chain structure with specific chain polarity with respect to the c axis. The refinement places the CH2OH side chains approximately 20′ from the so-called tg conformation, with a result that an 02′H…06 intramolecular bond is formed. The structure also contains an 03H…05′ intramolecular bond and an 06H…03 intermolecular bond along the a axis. All these bonds lie in the 020 planes, and the structure is an array of hydrogen-bonded sheets. A major consequence of this work is that regular chain folding can be ruled out and cellulose is seen as extended chain polymer single crystals.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/bip.1974.360131005

The structure of native cellulose

The structure of alpha-chitin.

The crustacean exoskeleton as an example of a structurally and mechanically graded biological nanocomposite material

A detailed model for the crystal structure of the fibrous polysaccharide chitin is proposed. The structure determination has been carried out by using an optical analogue instrument which proved to be an adequate and rapid tool for the derivation of Fourier transforms, signs of amplitudes and the production of optical Fourier syntheses. The new model of chitin accounts properly for known chemical and physical properties, including the infrared absorption as well as for x-ray data, but because of the limited resolution of the diffraction patterns it can only be regarded as a good approximation. The stereochemical configuration of the polysaccharide chains has certain implications for the structure of cellulose.

https://rupress.org/jcb/article-pdf/3/5/669/1068845/669.pdf

THE CRYSTAL STRUCTURE OF α-CHITIN (POLY-N-ACETYL-D-GLUCOSAMINE)

An instrument employing optical analogies to the diffraction of x-rays by macromolecular substances is described. Simple and readily obtainable components, materials and procedures are involved. Photographic methods are used to reduce the size of models for trial structures in forming masks whose optical diffraction is then compared with the x-ray diffraction of real structures. Conversely, the diffractometer can be employed to synthesize images of structures from masks simulating observed x-ray diffraction.Applications are described dealing with the investigation of helical chain molecules (polypeptide α helices, collagen and deoxyribonucleate molecules); with the study of larger sized structures exhibiting small-angle x-ray diffraction (e.g., collagen fibrils); and with image synthesis for centrosymmetric configurations (phthalocyanine).

Diego Carlstrom

Papers

THE CRYSTAL STRUCTURE OF α-CHITIN (POLY-N-ACETYL-D-GLUCOSAMINE)

Optical diffractometer for facilitation of x-ray diffraction studies of macromolecular structures.