Rigidity and Color

Carotenes are simple polyenes with conjugated double bonds as their only functional groups. Their chemistry is quickly summed up they absorb light, ds-trans isomerize, polymerize, and take up oxidants in allylic positions. Nevertheless, there are more open questions in carotene chemistry than anywhere else in bioor-ganic chemistry. Some examples of such questions are as follows  

Carotenes are water insoluble. Nevertheless 3-carotene, C Hg, occurs in large amounts in carrots, which consist almost exclusively of water (80%) and cellulose (20%). ji-Carotene is, therefore, not part of a functional membrane or enzyme system in these roots and occurs in the form of dead microcrystals. Also, carrots grow in the earth in total darkness. Why should there be a crystalline dye and how can it be formed Can crystals play a biological role that would justify the pain it takes to synthesize them  

a bolaamphiphile with one methylester and one carboxylate end group, appears in the waxy cover of seed granules of the South American and African tree Bixa orellana. This lively colored coating of the seed proteins may protect them against attack by microorganisms. Why is an unsymmetrical bolaamphiphile needed, if the protective role can presumably also be played by P-carotene Why is a cw-double bond introduced at one end  

P-Carotene is digested by humans and animals and degraded oxidatively to colorless retinal 320 nm). This white compound is then coupled with a white protein to allow color vision in the range of 400-700 nm. How did nature know that a colorless dye would eventually become useful in connection with a protein and sunlight  

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Polystyrene (PS), a highly rigid and surface-hardened thermoplastic, is glass clear and almost colorless. Its typical slight yellow tinge is easy to compensate for by adding transparent blue colorants to adjust the color. Polystyrene softens between 80 and 100°C. It is processed between about 170 and 280°C, up to a maximum of 300°C, without color change, by any of the methods which are recommended for thermoplastics. The list of products includes extrusion made sheets, profiles, and films, which are often foamed. 

HIPS is a thermoplastic that is widely used in packaging, toys, bottles, housewares, electronic appliances, and light-duty industrial components, because of its good rigidity and ease of coloring and processing. Flame retardant HIPS polymers find application in housings for business machines. Here we present recent issues and examples on applications of HIPS. 

Chemical Description Bromo-Chlor. Paraffin Low cost, highly efficient flame retardant with good color and color stability. Used to flame retard flexible and rigid polyurethane foam, textiles, carpet backing, PVC and adhesives. 

Compression-molded soy protein plastics are rigid and brittle without plasticizers present in the formulation (Paetau et al., 1994). Water absorption of early protein plastics could not be reduced to the very low levels that were obtained with synthetic, petroleum-derived resin products however, color, dyeing, and strength properties were good and production costs were relatively low (Johnson Myers, 1995). 

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