Chemistry.2C physical properties and biological function Chitin

-


chemical configurations of different monosaccharides (glucose , n-acetylglucosamine) , polysaccharides (chitin , cellulose) presented in haworth projection


the structure of chitin determined albert hofmann in 1929.


chitin modified polysaccharide contains nitrogen; synthesized units of n-acetyl-d-glucosamine (to precise, 2-(acetylamino)-2-deoxy-d-glucose). these units form covalent β-(1→4)-linkages (similar linkages between glucose units forming cellulose). therefore, chitin may described cellulose 1 hydroxyl group on each monomer replaced acetyl amine group. allows increased hydrogen bonding between adjacent polymers, giving chitin-polymer matrix increased strength.



a cicada emerges chitinous larval exoskeleton.


in pure, unmodified form, chitin translucent, pliable, resilient, , quite tough. in arthropods, however, modified, occurring largely component of composite materials, such in sclerotin, tanned proteinaceous matrix, forms of exoskeleton of insects. combined calcium carbonate, in shells of crustaceans , molluscs, chitin produces stronger composite. composite material harder , stiffer pure chitin, , tougher , less brittle pure calcium carbonate. difference between pure , composite forms can seen comparing flexible body wall of caterpillar (mainly chitin) stiff, light elytron of beetle (containing large proportion of sclerotin).


in butterfly wing scales, chitin organized stacks of gyroids constructed of chitin photonic crystals produce various iridescent colors serving phenotypic signaling , communication mating , foraging. elaborate chitin gyroid construction in butterfly wings creates model of optical devices having potential innovations in biomimicry. scarab beetles in genus cyphochilus utilize chitin form extremely thin scales (five fifteen micrometres thick) diffusely reflect white light. these scales networks of randomly ordered filaments of chitin diameters on scale of hundreds of nanometres, serve scatter light. multiple scattering of light thought play role in unusual whiteness of scales. in addition, social wasps, such protopolybia chartergoides, orally secrete material containing predominantly chitin reinforce outer nest envelopes, composed of paper.


chitosan produced commercially deacetylation of chitin; chitosan soluble in water, while chitin not.








Comments

Post a Comment

Popular posts from this blog

File format Wavefront .obj file

-
1 file format 1.1 geometric vertex 1.2 parameter space vertices 1.3 face elements 1.3.1 vertex indices 1.3.2 vertex texture coordinate indices 1.3.3 vertex normal indices 1.3.4 vertex normal indices without texture coordinate indices 1.4 other geometry formats 1.5 referencing materials 1.6 relative , absolute indices file format lines beginning hash character (#) comments. # comment an obj file may contain vertex data, free-form curve/surface attributes, elements, free-form curve/surface body statements, connectivity between free-form surfaces, grouping , display/render attribute information. common elements geometric vertices, texture coordinates, vertex normals , polygonal faces: # list of geometric vertices, (x,y,z[,w]) coordinates, w optional , defaults 1.0. v 0.123 0.234 0.345 1.0 v ... ... # list of texture coordinates, in (u, v [,w]) coordinates, these vary between 0 , 1, w optional , defaults 0. vt 0.500 1 [0] vt ... ... # list of vertex normals in (x,y,z) for...
Read more

CEFR alignment Euroexam International

-
table 1 - euroexam cefr equivalence euroexam provides tests of communicative english language proficiency @ 5 of 6 levels of cefr, practical tool language professionals evaluate different linguistic competencies of ‘can do’ descriptors. euroexams written, marked, , results calibrated based on cefr levels. means euroexam c1 level pass equivalent other exam board’s c1 level pass, example ielts 6.5 no element less 5.5., or cambridge english language assessment s 180 or cae grade c. (see table 1) euroexams has been directly involved in number of cefr development projects, last of in 2016. euroexam employs combination of internal , independent research support claim of equivalence cefr , other major exams.
Read more

Books Soma Valliappan

-
1 books 1.1 hr, investment , management 1.2 columns 1.3 creative writing books hr, investment , management valliyappan’s first book, thittamiduvom vetriperuvom, dealt self-development, published in year 2002. first book did in market , continued authoring books such thottathellam ponnaagum, kaalam ungal kaladiyil etc. introduced many specialized subjects in management tamil readers. valliyappan’s alla alla panam, published in august 2004 kizhakku publishers (new horizon media), created new record of sorts in tamil publishing world. book sold ten thousand copies in first few months of launch, unheard of investment book in tamil. in 2010, book’s sale crossed 1 lakh mark. following phenomenal success of alla alla panam, (aap) introduced basics of stock market, went ahead , wrote 4 more books on different aspects of stock market , investment technical & fundamental analysis (aap-2), futures , options( aap-3), portfolio management (aap-4) , trading (aap-5). soon, valliyappan became name...
Read more