Concentration of isothiocyanates

This study focuses on the determination of the characteristic odorants of wasabi in comparison with those of horseradish by calculation of the logarithmic ratio between the concentration of isothiocyanate and its odor threshold value. The relationship between the yields of the isothiocyanates formed by the action of wasabi myrosinase and the conditions of hydrolysis are presented. 

After the use of a chemical becomes widespread, new deleterious effects on human health may be observed. In such situations, the occupational limit values will have to be modified. Usually the OELS tend to decrease when more information on the toxicity of a chemical is obtained. Knowledge of the specific features of various chemicals is thus extremely important for planning ventilation of industrial premises. It is important to be especially aware of those chemicals that may cause long-term effects without causing any acute effects. There are also compounds such as isocyanates that are extremely irritating at concentrations as low as 0.5 ppm. However, some workers may become sensitized to isothiocyanates at a concentration of 10 ppb, and therefore this has to be taken into consideration when planning the industrial ventilation. Thus, one has to plan against compounds that can cause serious health effects at concentrations at which their presence cannot be observed by the human senses, i.e., irritation or odor. 

The edible parts of parsnips contain a chemical of insecticidal and strong synergistic nature. This chemical, present in a concentration of about 200 p.p.m., was isolated and identified as 5-allyl-l-methoxy -2, 3-methylene-dioxybenzene or myristicin. Its toxicity to various insects (fruit flies, etc.) was established and compared with pyrethrum and aldrin. A second chemical, identified as 2-phenylethyl isothiocyanate, was found in the edible parts of turnips and rutabaga, which also have been consumed for centuries by humans without obvious harm. 

Chemical modification studies with fluorescein-5 -isothiocyanate support the proximity of Lys515 to the ATP binding site [98,113-117,212,339]. Fluorescein-5 -isothiocyanate stoichiometrically reacts with the Ca -ATPase in intact or solubilized sarcoplasmic reticulum at a mildly alkaline pH, causing inhibition of ATPase activity, ATP-dependent Ca transport, and the phosphorylation of the Ca " -ATPase by ATP the Ca uptake energized by acetylphosphate, carbamylphos-phate or j -nitrophenyl phosphate is only partially inhibited [113,114,212,339]. The reaction of -ATPase with FITC is competitively inhibited by ATP, AMPPNP, TNP-ATP, and less effectively by ADP or ITP the concentrations of the various nucleotides required for protection are consistent with their affinities for the ATP binding site of the Ca -ATPase [114,212,340]. 

In a darkened lab, dissolve FITC (Thermo Fisher) in dry DMSO at a concentration of 1 mg/ml. Do not use old FITC, as breakdown of the isothiocyanate group over time may decrease coupling efficiency. Protect from light by wrapping in aluminum foil or using amber vials. 

The reaction may be quenched by the addition of ammonium chloride to a final concentration of 50 mM. Some protocols also include at this point the addition of 0.1 percent xylene cylanol and 5 percent glycerol as a photon absorber and protein stabilizer, respectively. React for a further 2 hours to stop the reaction by blocking remaining isothiocyanate groups. 

Add 33 pi of fluorescein isothiocyanate (FITC tetramefliylrho-damine isothiocyanate, TRITC, or another fluorescent dye isothiocyanate derivative is used the same way), 50 mg/ml in DMF, to 1 ml of 5 mg/ml IgG in Soln. A. Shake at RT protected from light for 1 h. Remove surplus FITC and its hydrolysis products on a Sephadex G-25 column, equilibrated with PBS. The conjugate appears in the void volume and should be concentrated by ultrafiltration. Add sodium azide to a final concentration of 0.02% (w/v) and glycerol up to 10% (w/v) and store at 4 °C. 

In another investigation, linalool (Fig. 8.1) was detected in relatively low concentration in the solvent-extracted volatiles of fresh papaya pulp from Sri Lanka [41]. The authors attributed the characteristic sweaty note of this papaya fruit mainly to methyl butanoate. Phenylacetonitrile was also found in high amounts (17.7%), which, according to the authors, combined with lesser concentrations of benzyl isothiocyanate (1.5%) can play a role in the aroma of papaya. 

The concentrations of linalool and benzyl isothiocyanate in papaya are clearly affected by the addition of Hg +. It is suggested that the mercurous ion could... 

Fluorescein isothiocyanate or tetramethylrhodamine isothiocyanate (see Note 1) dissolved in dimethyl sulfoxide at a concentration of 1 mg/mL. 

SPITC-reagent Dissolve 2.55 mg 4-sulfophenyl isothiocyanate sodium salt monohydrate (SPITC, technical grade, Sigma Aldrich, St. Louis, MO store at 4°C) in Tris-buffer at a concentration of 2.55 mg/mL. Prepare always a fresh solution and use immediately. 

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