Silk workers

Religious strife in the seventeenth century had driven families of skilled Huguenot silk workers like the Sarasins to the haven of this quiet old river port and city-state. A century later their entrepreneurial energy and judicious intermarrying had transformed Bale into a thriving merchants and bankers oligarchy of some 15,000 inhabitants. The town s broad streets, town houses, and steepled churches reflected its reputation for prosperity, order, and restrained Protestant piety. 

Catalytic asymmetric hydrogenation is a relatively developed process compared to other asymmetric processes practised today. Efforts in this direction have already been made. The first report in this respect is the use of Pd on natural silk for hydrogenating oximes and oxazolones with optical yields of about 36%. Izumi and Sachtler have shown that a Ni catalyst modified with (i ,.R)-tartaric acid can be used for the hydrogenation of methylacetoacetate to methyl-3-hydroxybutyrate. The group of Orito in Japan (1979) and Blaser and co-workers at Ciba-Geigy (1988) have reported the use of a cinchona alkaloid modified Pt/AlaO.i catalyst for the enantioselective hydrogenation of a-keto-esters such as methylpyruvate and ethylpyruvate to optically active (/f)-methylacetate and (7 )-ethylacetate. 

Silk TJ, Phipps AW, Bailey MR. 1997. Effects on dose coefficients for workers of recent changes in internal dosimetry. Radiat Prot Dosim 71(1) 7-21. 

In Lyons, Arfwedson and Berzelius observed the manufacture of silk and velvet in the homes of the workers. In Geneva they visited Dr. and Mrs. Alexandre Marcet. While they were in Zurich, Professor M. A. Pictet of Geneva announced to them that they had both been elected to honorary membership in the Helvetian Scientific Society. 

Se NMR of 2-phenylselenopropionates was introduced by Michelsen, Annby and Gronowitz1 More recently, Silks and co-workers developed the cyclic 2-oxazolidineselone as a far reaching... 

Morrison and co-workers (33) measured the heat of wetting of silk fibroin and wool keratin in water as a function of their water content. Their data received proper thermodynamic treatment except that heats of solution are presumed absent. It is likely that solution effects are absent or small if zero heats are found for the immersion of samples equilibrated near the saturation pressure of water. 

Several workers subsequently confirmed these observations. Stein et al. (1944) examined the hydrolytic products with the manometric methods developed by Van Slyke and co-workers (1941) and demonstrated that dipeptides represented the overwhelming proportion of the products formed when silk fibroin was hydrolyzed for 96 hr at 40°C in concentrated HCl. After 40 hr, the hydrolyzate contained about 25% free amino acids with the remainder of the residues existing as di- and tripeptides. Bull and Hahn (1948), using a spread monolayer technique for estimating molecular weights, examined partial acid hydrolysis of egg albumin. By this method, immediate cleavage of about fifty bonds was observed when egg albumin was dissolved in 7.6 N HCl at 60°C. The remainder of the bonds were hydrolyzed at much slower rates. 

Recent physico-chemical investigations of such materials are somewhat contradictory. Japanese workers, with a strong tradition in such work, suggest that certain silkworm fibroins are branched, whereas different workers, stress the liquid-crystalline nature of other materials, such as spider silks, and the parallels vwth linear synthetic liquid-crystalline polymers. Perhaps it is fair to say, as in other areas discussed in this article, that there is still a severe shortage of basic information. 

Dragline spider silk has aroused considerable interest due to its excellent mechanical properties, for example stability, elasticity and low weight. A. Bram and co-workers (ESRF) have succeeded in recording X-ray diffraction patterns from a single spider dragline of less than 10 pm diameter(Figure 3(b)). These results allow the elastic properties of the fibres to be linked to the molecular architecture of the polymer chains. 

Another approach was recently developed by Smeenk et al. [90]. They used the combination of protein engineering and polymer modification for the creation of a series of silk-based block copolymers. Spider silk consists of two major domains, a j0-sheet crystalline domain, which gives strength to the protein, and a less well-defined amorphous domain, which introduces elasticity and toughness. Smeenk and co-workers produced a j0-sheet forming protein... 

The first report of enantioselective catalysis over metal catalysts was made in 1939 by Lipkin and Stewart who showed that hydrocinchonine / -methylcinnamate could be hydrogenated in ethanol over an Adams Pt catalyst to yield / -phenylbutyric acid which exhibited an optical rotation of 8%.89 Some 20 years later, Akabori and co-workers reported that Pd supported on silk-fibroin was enantioselective for compounds containing both C=N and C=C functionalities, yielding optical yields as high as 66%, although the origin of the enantioselectivity in these systems has never been clear.90 A further 20 years later, Orito and co-workers reported... 

Adverse ocular effects in workers of a viscose silk plant exposed 6 hours a day, 5 days a week, for 0.5-30 years to less than 3.2 ppm carbon disulfide were reported by Szymankova (1968). Disturbances were manifested as vascular or inflammatory degenerative changes in the retinas of 12 out of 75 (16%) of the exposed workers, which disappeared in 11 workers following cessation of carbon disulfide exposure. 

In 1908 Gelmo discovered sulfanilamide while working with azo dyes. Other workers subsequently found that related sulfa compounds combined tenaciously with the proteins of wool and silk. This suggested the possibility that they might also react with bacterial protoplasm. A quarter of a century after Gelmos synthesis, Domagk observed that mice with various bacterial infections could be protected by sulfonamides, an observation for which he was awarded a Nobel Prize in 1938. 

D. L. Kaplan and co-workers, eds., Silks Materials Science and biotechnology, American Chemical Society, Washington, D.C., 1994. 

The first kinetic study of free-radical formation in mechanically loaded polymers was by Zhurkov and co-workers who studied the stepwise loading of nylon 6 and silk fibers (26). The concentration of free radicals was monitored by ESR as a function of applied stress and time. They found that the rate of radical formation (R) is a function only of stress (a) ... 

The amazing Chardonnet silk was exhibited at the Paris Exhibition of 1889. Financial backers came calling, and the sUk — named rayon, because rays of fight enhanced its lustrous shine — was being produced commercially by 1891. The first rayons were highly flammable, and the factory workers who made the new material began to refer to it by a less endearing name mother-in-law silk. 

---