Silk lipids

The composition of lipids from the silk and cuticule has been reviewed by Schulz (1997a, 1999). These lipids consist primarily of alkanes, as found in other arthropods, with 2-methylalkanes with an even number of carbon atoms in the chain being most abundant, with lesser amounts of alcohols, acids, aldehydes, and wax esters. Recently, a thorough analysis of the silk lipids of N. clavipes (Schulz, 2001) revealed a unique class of lipids from spider silk and cuticle, consisting of straight-chain and branched methyl ethers (1-methoxyalkanes, Fig. 4.4) with chain lengths between 25 and 45 carbon atoms. 

Table 4.2. Occurrence of alkanes and 1-methoxyalkanes on the silk lipids...

Presence of individual compounds , as major components in silk lipid extract o, as minor or trace components absence. 

It has been suggested that silk lipids may play a role in these interactions, but as yet there is no hard evidence. 

Composition of the silk lipids of the spider Nephila clavipes. Lipids 36 637-647. 

Only one species in this large family has been investigated. Female Clubiona cam-bridgei silk induces courtship by males. The silk is active even in the absence of the female, but loses its activity upon extraction with ether (Pollard et al, 1987), suggesting the presence of a lipid-soluble pheromone. 

As can be seen from the examples discussed so far, pheromones present on spider cuticle or silk frequently play an important role in spider communication, but limited information is available about their composition. Lipids, whose primary function is regulation of water content, also may have important roles in communication. 

A particularly thorny problem that remains to be resolved is the species-recognition process that is mediated by physical or tactile cues associated with silk or the cuticle, as well as pheromones on these two substrates. To date, the lipid mixtures associated with silk or cuticle seem to display the most variable structures and blends, making them good candidates for species recognition. In contrast, the more polar components appear to be less species specific and so are less likely to be the key factors in intraspecific recognition. 

Schulz, S. and Toft, S. (1993a). Branched long chain alkyl methyl ethers a new class of lipids from spider silk. Tetrahedron 49 6805-6820. 

Although much of the interest in biological nanostructures has focused on relatively complex functionality, cells and organisms themselves can be considered as a collection of self-assembled materials lipid bilayers, the extracellular matrix, tendon and connective tissue, skin, spider silk, cotton fiber, wood, and bone are all self-assembled biological materials, with an internal structure hierarchically ordered from the molecular to the macroscopic scale. 

The silk and cuticle of spiders are covered by a lipid layer. These lipid compounds protect from external damaging factors such as humidity, which modifies the cuticle s or silk s physical properties. The frequency of water exposure in natural circumstances suggests that wetting with water or similar solvents must have negligible or manageable effects on pheromone function. 

Quantitative changes in lipid compounds on the silk and cuticle of females correlate significantly with changes in female sexual receptivity in spiders. For example, female T. atrica attach a contact sex pheromone to their web (Trabalon et al., 1997,2005 Prouvost et al., 1999). This pheromone consists of a complex mixture of saturated hydrocarbons, methyl esters (methyl tetradecanoate, methyl pentadecanoate, methyl hexadecanoate, and methyl octadecanoate) and their fatty acids (tetradecanoic, pentadecanoic, hexadecanoic, and cis,cis-9,12-octadecadienoic acids). The female uses cuticular compounds, which are applied to the silk in substantial amounts during web construction. Modification of chemical profiles makes the female attractive to males (Trabalon et al., 2005). Receptive females are different to unreceptive ones with respect to three fatty acids (hexadecanoic, octadeca-dienoic and octadecenoic acids) and three methyl esters (linoleate, oleate, and stearate) present on both the web and the cuticle. Our combined results from chemical analyses and behavioral assays demonstrate clearly that these contact compounds are quantitatively correlated with the behavior of spiders. 

The key components in all sophisticated biological materials are the macromolecules that the cells produce and subsequently incorporate into the material. These include proteins, glycoproteins, proteoglycans, lipid assemblies and polysaccharides. Many biological materials are composed almost entirely of these assembled macromolecules. Common examples are the cuticles of many insects, the skin and tendons of vertebrates or the silk of spider webs. A very widespread adaptation is to stiffen the material by the introduction of a mineral phase. Common mineralized biological materials include the shells of mollusks, the carapaces of crustaceans, and the bones and teeth of vertebrates. Many of them are composite materials and are known to possess remarkable mechanical properties, especially when taking into account that they form at ambient temperatures and pressures, and that their mineral components are often commonplace materials with rather poor natural mechanical properties... 

The pigment mixture from turmeric is used to dye textiles (yellow to brown, cotton, wool, and silk) and to color certain foodstuffs. Curcumin is an important constituent of Indian curry spice. Curcumin inhibits lipid peroxidation and has antibacterial activity. It inhibits activation of transcription factor NFxB (relevant for signal transduction, septic shock, inflarrunatory diseases). ... 

Nature uses self-assembly to build highly structured systems for specific functions. Examples include the transfer and storage of genetic information in nucleic acids, the organization of lipids into protective cell membranes that serve as molecular receptors for the cell, and the hierarchical structure of spider silk, still one of the strongest known fibrous materials.yet flexible enough to absorb the impact energy of an unlucky fly. 

Biodegradable plastics can be based on natural or synthetic resins. Natural biodegradable plastics are based primarily on renewable resources (such as starch) and can be either naturally produced or synthesized from renewable resources. They are coming under polysaccharides (starch, cellulose, lignin, etc.), proteins (gelatine, wool, silk, etc.), lipid (fats and oil), polyesters produced by plant or microorganisms (PHA), polyesters derived... 

Polymeric miaospheres are candidates for use in dmg delivery because of their ease of delivery and the ability to regulate drug release kinetics. Many examples of silk fibroin-based microspheres have been demonstrated. The methods used to produce silk spheres include emulsification, spray drying laminar jet breakup, miaofluidics, lipid templating ... 

Akao et al. (1982) reported on a commercial steam-drying/deodorization plant to process soy sauce cakes as feedstock. An agitated trough steam dryer (1.5 tons/h dry product capacity) was used. Deodorization commenced at moisture levels below 4% db and a temperature of 135°C. The oils and fats distilling from the cake resulted in deodorization of the product. Indeed, the fats and oils were used as auxiliary fuels for the process. Concurrent steam drying and deodorization of rice bran, fish meal, and silk cocoons were also reported by Akao (1983). In these products, the odor is due to oxidation of lipids. He also showed that the quality of green tea and vegetables dried in steam (e.g., color, smell, etc.) was acceptable. 

Upon infection, insects can produce a wide range of antimicrobial peptides, which are synthe zed in the fax. body and/or haemocytes and secreted into the haemolymi. Such peptides include ceert ins (33), and defensin-like peptides such as sapecin and phormicin (34,35). Cecropins are highly amphipathic peptides containing 31-39 residues that form voltage-dependent channels in lipid membranes (36). They were initially isolated from the silk moth Hyolop/tora cecropia (37) and have subsequently been isolated from the flesh fly (sarcoroxin 1) and Drosophila (38,39). Cecropins are distinct from other insect cationic peptides in that they contain no cysteine residues and fail to lyse eukaryotic cells (33),... 

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