Natural rubber clone

Sando, T., Takaoka, C., Mukai, Y., Yamashita, A., Hattori, M., Ogasawara, N., Fukusaki, E. and Kobayashi, A. (2008) Cloning and characterization of meval-onate pathway genes in a natural rubber producing plant, Hevea brasiliensis. Biosci. Biotechnol. Biochem., 71, 2049-60. 

Numerous Hevea varieties, referred to as clones in the professional jargon, can be found in estates. Sub-ramaniam [4] was the first to study natural rubber from various clones by size-exclusion chromatography (SEC), to study the native molar mass distribution. 

In the case of natural rubber from Hevea brasiliensis, which is almost entirely made of cis-isoprene units, it could be assumed that ci5-prenyltransferase is exclusively involved in phase 2. Unfortunately it is more complex. Authors agree on phase 1, which is traws -condensation catalyzed by a cytosolic soluble trans-prenyl transferase" Famesyl diphosphate synthase has been cloned from rubber latex.The most probable prenyldiphosphate used as a primer for phase 2 is famesyl-PP (15) or geranylgeranyl-PP (16)." " Phase 2 is catalyzed by a still not clearly identified rubber transferase system. Different proteins have been... 

Non-isoprene components of Hevea brasiliensis latex account for around 10% of its dry matter while they account for about 5% of the raw dry rubber derived from latex (Table 9.5.2). They comprise proteins, carbohydrates, hpids and inorganic constituents and represent the main composition dilference between natural rubber (NR) and its synthetic counterpart, namely poly(cis-1,4-isoprene) synthetic rubber (IR). They could therefore be involved in the irreplaceable specific qualities of NR. The nature and quantity of these non-isoprene components can vary greatly depending on the clones, the exploitation system and environmental conditions. Some of these components are either dissolved or suspended in the aqueous medium of the latex while the others are adsorbed on the surface of rubber particles. 

As mentioned before, lipids are the family of non-isoprenes that is the most retained with the rubber during processing. Their extraction for analytical purposes has been optimized recently by Liengprayoon. Depending on the clone, lipids amount to 2.5 to 3.8% versus rubber in latex, and 1.8 to 3.3% in dry natural rubber. Three families of lipids can be distinguished ... 

Rubber Chemistry and Technology 75, No.l, March-April 2002, p.171-7 EVALUATION OF NATURAL RUBBER FROM CLONES OF HEVEA BRASILIENSIS... 

Journal of Rubber Research 3, No.3,3rd Quarter 2000, p. 164-8 INHERENT MOLAR MASS DISTRIBUTION OF CLONES AND PROPERTIES OF CRUMB NATURAL RUBBER... 

Identification, cloning, and sequence of a major allergen (Hev b 5) from natural rubber latex (Hevea brasi-liensis). J Biol Chem 271 25394-25399... 

Fresh natural rubber latex contains about 30-40% of rubber hydrocarbon that is normally referred to as dry rubber content (DRC). However, the total solid content (TSC) is higher than the DRC due to the presence of non-rubbers in the latex, at around 5%. The DRC and non-rubber content may change due to many factors such as clone, soil and climate conditions, season, type of fertilizers used, and tapping frequency. Most of these non-rubbers are dissolved or suspended in the aqueous serum or adsorbed on the surface of rubber particles. They become trapped, tenaciously held, or co-precipitated during coagulation of the rubber probably due to their poor solubility in the aqueous medium or strong entanglement with the rubber molecule. The major non-rubbers are lipids, proteins and amino acids, minerals, inositols and carbohydrates, as shown in Table 3.1. 

Table 3.2 Lipid content of natural rubber from dilferent clones. ...

Table 3.3 Distribution of fatty clones. adds in natural rubber from different...

Like glycolipids, phospholipids are also a elass of polar lipids. Data in Table 3.2 show that phospholipids in natural rubber are normally below 0.6% w/w. A recent study showed that the major components were phosphatidyl choline (PC) and lysophosphatidyl choline (LPC), as shown in Table 3.5. Other minor components were phosphatidyl ethanolamine (PE), phosphatidyl inositol (PI), lysophosphatidyl inositol (LPI), and metal phosphatidates (MP) or phosphatidic acid (PA). Unlike neutral lipids and glycolipids, the acyl components of phospholipids normally contain very low levels of furanoic acid, except for certain rubber clones. The isolated fatty acids are mainly palmitic, stearic, oleic and linoleic acids. ... 

Fig. 2.3. Molecular weight distribution of natural rubber obtained by gel permeation chromatography. Results are plotted in terms of recorder response against elution volume for samples from different clones. (Reprinted with permission from Rubber Chem. Technoi, 45,346 (1972). Copyright by the American Chemical Society.)...

Bonfils, F. Char, C. Gamier, Y. Sanago, A. Sainte-Beuve, J. Inherent molar mass distribution of clones and properties of cmmb natural mbber. J. Rubber Res. 2000, 3, 164-168. 

Historically, enzyme catalysis has played a highly prominent role, with the first enzyme-catalyzed asymmetric addition of HCN to aldehydes dating back to 1908 [167]. A wide range of both aromatic and aliphatic ketones are suitable substrates and produce cyanohydrins of high optical purity. The most readily available and hence most commonly employed enzyme for asymmetric cyanohydrin formation is (R)-hydroxynitrile lyase isolated from almonds. Recent cloning and over-expression techniques have also made a number of (S)-hydroxynitrile lyases available for organic synthesis [164, 165]. This was utilized in Griengl s synthesis of coriolic acid (255), a natural product that displays calcium ionophoric activity and acts as a prostacyclin mimic (Scheme 2.32) [168]. Thus, an (S)-hydroxynitrile lyase was cloned from rubber trees (Hevea brasiliensis), overexpressed in Pichia pastoris, and used to provide cyanohydrin 254 in 99 % ee. 

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