10-Methylstearate

Ionization in Cl is the result of one or several competing chemical reactions. Therefore, the sensitivity in Cl strongly depends on the conditions of the experiment. In addition to primary electron energy and electron current, the reagent gas, the reagent gas pressure, and the ion source temperature have to be stated with the sensitivity data to make a comparison. Modem magnetic sector instmments are specified to have a sensitivity of about 4 x 10" C pg for the [Mh-H] quasi-molecular ion of methylstearate, m/z 299, at / = 1000 in positive-ion Cl mode. This is approximately one order of magnitude less than for El. 

OPCW GC/MS TEST MIXTURE containing in dichloromethane 10 rg/mL of n-Alkanes Cs-C24 even numbers Trimethylphosphate 2,6-Dimethylphenol 5-Chloro-2-methylaniline Tri-n-butylphosphate Dibenzo thiophene Malathion Methylstearate... 

Branching. For example, stearic acid (18 carbons) and arachidic acid (20 carbons) are both saturated and linear. They melt at 70°C and 75°C, respectively, whereas 10-methylstearic acid melts at 10°C. However, branched fatty acids are rare in living systems and the evolution of synthetic pathways for them has not occurred as a major device for keeping lipids fluid. 

Hydrocarbon Analysis. Sediment samples were thawed and mixed to provide a homogeneous sample. Approximately 150 g wet weight was placed in a Soxhlet extraction apparatus and saponified-extracted with benzene /0.5 N KOH-methanol (50/50) (ca. 250 ml total) for 24 hours, or until the extraction solution was clear (6,11,12). An internal standard consisting of ca. 50 ug each of 5,a-androstane and o-terphenyl was added prior to extraction to provide assurance of extraction efficiency, separation of saturated and unsaturated fractions and to provide a standard reference for the gas chromatographic data system. Methylstearate (the methyl ester of stearic acid) was added to select samples to verify saponification efficiency. 

A mid-chain branch occurs in tuberculostearic acid (lOo-methylstearic) present in the lipids of the human tubercle bacillus and in other bacterial lipids. 

For its own purposes, the tuberculosis-causing organism Mycobacterium tuberculosis needs a molecule called 10-methylstearate. It makes this compound from a modified amino acid, 5 -adenosylmethionine, and oleate, a salt of oleic acid (Fig. 3.82). 

FIGURE 9.70 The final product of the methylation of oleate is 10-methylstearate. 

Methylstearic acid 2 C-10 of 9,10-oleic acid M. smegmatis cultures Jaureguiberry et of, 1965... 

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