Levan, methylated

However, some carbohydrates with a terminal D-fructofuranose residue are not suitable substrates for levan formation, e. g., methyl /3-d-fructofuranoside and inulin,64 even in the presence of enzymes98 which hydrolyze these substrates. 

Two methylations of levan by means of dimethyl sulfate and potassium hydroxide (not sodium hydroxide) followed by one inethylation with methyl iodide and silver oxide yielded trimethyllevan in 88% yield. This was purified by solvent fractionation over-all yield 75%, m. p. 145-146°, OCHs 45.9%. Trimethyllevan, hydrolyzed by heating at 95° for twenty-four hours with a dilute solution of sulfuric acid gave a 98.5% yield of a crystalline trimethyl-D-fructose. The trimethyl-D-fructose was proved940 to be 1,3,4-trimethyl-D-fructofuranose since oxidation with nitric acid gave a 97% yield of a dimethyl-2-keto-D-gluco-saccharic acid which was identified as the crystalline diamide (95% yield). 

Challinor, Haworth and Hirst101 determined the chemical structure of the levan produced by the action of B. mesentericus on sucrose. Methylated levan appeared homogeneous when fractionally precipitated from mixed solvents. Fractional distillation of the hydrolytic products of methylated levan yielded tetramethyl-D-fructofuranose in an amount corresponding to a levan chain length of from ten to twelve fructofuranose units, joined as previously940 shown through the 2- and 6-positions. 

The specificity of levansucrase98 is dependent not only on the d-fructoside but also on the aldoside residue of the substrate. Neither inulin nor methyl D-fructofuranoside was hydrolyzed by levansucrase, and even when these two substrates were hydrolyzed by inulase (prepared from inulin-fermenting Torula yeast) or by yeast invertase respectively, no levan formation occurred with levansucrase. However, neither methyl D-fructofuranoside nor inulin inhibited levan formation from sucrose by levansucrase. No levan was formed from potassium D-glucose... 

Nan Qi, Douglas LeVan M (2005) Coadsorption of organic compounds and water vapor on BPL Activated carbon. 5. Methyl ethyl ketone, Methyl isobutyl ketone. Toluene, and Modeling. Ind Eng Chem Res 44 3733-3741... 

Four trimethyl-D-fructoses are known but only one of them is crystalline. Crystalline 1,3,4-trimethyl-D-fructose has been obtained from methylated levan,10 1,4,6-trimethyl-D-fructose from methylated melezi-tose and by synthesis, 3,4,6-trimethyl-D-fructose from methylated inulin and by synthesis, and 3,4,6-trimethyl-D-fructose has been synthesized. 

Similar results were obtained with the enantiomers of methyl mandelate separated on 4-methylcellulose tribenzoate immobilized on silica [30]. Figure 4.4a shows the experimental adsorption data for the two pure enantiomers (symbols), the best bi-Langmuir isotherms (solid lines) and the best LeVan-Vermeulen isotherms [33]. The data (symbols) were obtained by ECP. Figures 4.4b-d compare the competitive isotherm data measured with three mixtures of different composition and the isotherms calculated from the single component isotherms (Figure 4.4a) using the competitive bi-Langmuir model (Eq. 4.10). Results obtained... 

Figure 4.4 Competitive isotherms of the 0 and enantiomers of methyl mandelate on 4-methylcellulose tribenzoate, with hexane/2-propanol (90 10) as the mobile phase, (a) Single-component isotherms at 30°C solid lines, competitive Langmuir model dotted lines, LeVan-Vermeulen isotherm, (b) Experimental (symbols) and calculated (lines) competitive isotherms ratio C(+)/C(-) = 1.05. (c) Same as (b), but ratio C(+)/C(-) = 2.43. (d) Same as (b), but ratio C(+)/C(-) = 0.32. Reproduced from F. Charton and G. Guiochon, ]. Chro-matogr., 630 (1993) 21 (Figs. 2 and 3).

Metal ions and complexes may induce chromosome aberrations and Cu + and Pb + (Levan, 1945) or phenyl and methyl mercury (Ramel, 1969) very efficiently lead to disturbances of the nuclear spindle which are of a kind that could lead to aneuploidy. Diploids are less suited to detect the phenotypic effect in Xg of chromosome losses. However, a certain mutagenic effect in the pea caused by a number of metal ions was fpund by von Rosen (1964). Sterility at doses above LD50 of the mercury complexes has been recorded in barley (Ehrenberg et aLy unpublished). Scheibe (1959) found a mutagenic effect in barley and wheat of AICI3 when applied to the spike following the method of Oehlkers (1949). 

Andreassen, A., Vikse, R., Mikalsen, A., Adamovic, T., Steffensen, I.L., Hjerthohn, H., Levan, G., and Alexander, J. (2006) 2-Amino-l-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induces genetic changes in murine intestinal tumours and cells with ApcMin mutation. Mutat. Res. 604, 60-70. 

Laminarin Insoluble-/orm, L-20 Laminarin Soluble-/orm, L-20 Laminarin, L-20 Latosillan, L-26 Lentinan, L-29 Leucosin, L-32 Levan, L-34 Lichenan, L-39 Mannan, M-22 Melanocidin A, M-126 Melanocidin B, M-127 Methyl cellulose, C-48 Methylol cellulose, C-48 Mucoran, M-320 Nadroparin, N-1 Neoschizophyllan, N-26 Nitrocellulose, C-48 Nucleoticidin, N-85 Parnaparin sodium, P-11 Pectic acid, P-14 Pelvetian, P-15 Peptidoglycan, P-50 Pestalotan, P-51... 

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