Japanese lacquer

Natural resins Burgundy pitch Copal Dammar Japanese lacquer Pine rosin Wood rosin... 

Japanese lacquer, have also been employed. The partitioning of ions into this phase is selectively aided by either ion exchangers or neutral carriers. 

The blue copper protein stellacyanin, with a molecular weight of about 20,000, is obtained from the Japanese lacquer tree Rhus vemicifera. The EPR spectrum is described by roughly axial g and ACu hfs tensors and an unusually small a j value. As shown in Fig. 39 a, only the largest copper hf value A u can be directly determined from the EPR spectrum202. This coupling does not lie along the largest g-principal axis, in contrast to the usual behaviour of square planar copper complexes. 

Copper, like iron, is frequently encountered in reactions involving dioxygen. The copper enzyme laccase catalyses the oxidation of uroshiol (the same poisonous substance found in poison oak and ivy) in the production of Japanese lacquer. It is the products of uroshiol oxidation, which are responsible for the lacquer s remarkable material properties. 

Another interesting blue protein is stellacyanin (FW = 20 000) from the Japanese lacquer tree Rhus vernicifera, in which, with respect to the other cupredoxins, glutamine replaces the methionine ligand.64 Stellacyanin also bears an overall positive charge (p/=9.9). It, therefore, gives a reversible Cu(II)/Cu(I) response at a glassy carbon electrode in aqueous solution (pH 7.6).61 The formal electrode potential of the Cu(II)/Cu(I) reduction (E01 = + 0.18 V vs. NHE) is the lowest among cupredoxins. 

Japanese lacquer. These lacquers are a type of oleoresin that dry by oxidation in a damp atmosphere.14... 

The mechanism of dioxygen reduction at the trinuclear cluster in MCO catalysis has been a strong focus for research on this class of copper oxidases. Dioxygen reduction has been most thoroughly investigated in Rhus laccase (a plant laccase, from the Japanese lacquer tree). The primary reason for using Rhus Lac is the availability of a metal-substituted form the enzyme, a TlHg form, in which the... 

Laccase was discovered in 1883 by Yoshida (4), who found that the latex of the Chinese or Japanese lacquer tree rapidly hardened to a plastic in the presence of oxygen, and he attributed this to the presence of a diastase in the lacquer. A few years later Bertrand (5) further purified this enzyme and named it laccase. He suggested that laccase is a metalloprotein containing manganese and introduced the term oxidase. About 50 years later Keilin and Mann (6) demonstrated that laccase is a copper enzyme and showed that its blue color disappears reversibly upon addition of substrate. Laccase has been extensively reviewed by the researchers in this field over the last 20 years, and a representative selection is listed (3, 7-12). 

Laccase is widely distributed in plants and fungi. Laccase from higher plants, found in various species of the Chinese, Vietnamese, and Japanese lacquer trees, has been extensively investigated (9). The biological function of laccase in these trees is well understood. The laccase of the lacquer trees (Rhus sp.) is found in white latex, which contains phenols. After injury of the tree, these are oxidized by dioxygen to radicals, which spontaneously polymerize, building a protective structure that closes the wound. 

Erythema multiforme in a photodistribution has been attributed to Rhus vemiciflua, the Japanese lacquer tree (6). The rash was reproduced by challenge with the drug and sunlight. On contact with R. vemiciflua the patient had a flare of the eruption, which was limited to the areas... 

Raw lacquer is called urushi. For our knowledge of the composition of urushi and the complex hardening process of the thin film layers, we now rely primarily on the recent work of Kumanotani and his coworkers (1-7). The sap of the Japanese lacquer tree is a latex containing 20-25% water, 65-70% urushic acid (urushiol), approximately 10% gummy sub-... 

Faced with the problem of elucidating the individual roles of the diflFerent copper centers in the blue oxidases, the researcher has naturally focused in recent years on the laccases (9). Being easier to isolate, better characterized, and containing fewer copper atoms than cemloplasmin or ascorbate oxidase, the laccases from the Japanese lacquer tree Rhus vernicifera and the fungus Polyporus versicolor have been the subject of several transient kinetic studies in the millisecond range, that is, studies using stopped-flow spectrophotometry and rapid-freeze EPR spectroscopy (9,49,50). 

The phenolic lipids of Anacardieum occidentale have been commercially exploited (ref. 174) and those in Rhus vernicifera to a lesser extent. Most of the technical cashew nut shell liquid (CNSL) which results from industrial processing is and has been employed as a phenolic source for formaldehyde polymerisation the products from which in compounded form have been the basis for friction dusts widely used throughout the world in vehicle brake and clutch linings (ref.175). Urushiol has had use over many centuries in the art of Japanese lacquering (ref. 176) and in more recent years has been sometimes supplemented with CNSL. Chemical uses are referred to later. 

Japan lacquers (Japan varnishes). Genuine J. 1. are obtained from exudates (injury Juices) of Rhus verni-ciflua (Anacardiaceae), the Japanese lacquer tree (varnish tree), (Latin verniciflua=excreting varnish). J. 1. are soluble in 60-80% ethanol they are used traditionally in Japan and Asia as varnish. Since genuine J. 

Japanese lacquer n. A glossy coating obtained by tapping the sap from the Japanese varnish tree (Rhus vernicifera) or sumac. Langenheim JH (2003) Plant resins chemistry, evolution ecology and ethnobotany. Timber Press, Portland, OR. Weismantal GF (1981) Paint handbook. McGraw-Hill Corp. Inc., New York. 

Rhus vernicifera n. C22H31O3. Chinese tree which delivers a milky type of liquid. When the water is removed, a dark oily liquid is obtained, which yields a tough flexible film on atmospheric oxidation. The chief constituent of the film-forming material is an unsaturated phenol-acid-urushiol. The liquid is used for the preparation of Japanese lacquer. 

Urshiol n. Hydroxy acid of aromatic type present in Rhus vernicifera, the basis of Japanese lacquer. 

Naturally drying oils, including dammar, Japanese lacquer and shellac, are suitable for lacquers and varnishes because they dry quickly, although the film... 

Toxic Anacardiaceae in other countries include Comocladia and Metopium [34] in Central America and the Caribbean, Mauria [35], Lithraea [36, 37] and T. striata [38] in South America, Smodingium argutum [39, 40, 41] in Africa, the Japanese wax tree (T. Succe-daneum) [42] and T. vernicifluumy the source of Japanese lacquer [43]. 

Kawai K, Nakagawa M, Kawai K, Liew FM, Yasuno H (1991) Hyposensitization to urushiol among Japanese lacquer craftsmen results of patch tests on students learning the art of lacquerware. Contact Dermatitis 25 290-295... 

Main constituent of the allergenic oil of poison ivy Toxicodendron radicans)y poison oak (T. diversilobum) Asiatic lacquer tree (T. verniciferum D.C.) and other plants of the genera Toxicodendron and Anacardiaceae. A mixture of several compounds which are derivatives of catechol Uses in Japanese lacquer... 

Japanese Lacquer Films Lacquers are used ubiquitously as surface-coating materials for wood, porcelain, and metal. The main component of Japanese lacquer ( ura-shi in Japanese) is urashiol, a brown liquid (boiling point, 200-210 °C) consisting of a mixture of several catechols, each substituted with a satmated or unsaturated alkyl chain of 15 or 17 carbon atoms [55]. The liquid that causes an allergic skin reaction in most people, is obtained from the sap of the Japanese lacquer tree (Rhus vemicifera) and can be polymerized to form lacquer films. Lacquer films have been... 

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