"Titration Solutions"

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Bromine number titration solvent ASTM 1159 & ASTM D 2710

Supplier: Aqua Solutions

Bromine number titration solvent ASTM 1159 & ASTM D 2710

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Phenol red sodium salt

Supplier: Adipogen

Water soluble pH indicator used in the 6.8 (yellow) to 8.2 (red) range and frequently used in cell biology laboratories. Widely used as cell tissue culture pH marker. A small amount of phenol red added to the growth medium will have a pink-red color under normal conditions. Typically, 15 mg/l are used for cell culture. In the event of problems, waste products produced by dying cells or overgrowth of contaminants will cause a change in pH, leading to a change in indicator color. For example, a culture of relatively slowly dividing mammalian cells can be quickly overgrown by bacterial contamination. This usually results in an acidification of the medium, turning it yellow. The waste products produced by the mammalian cells themselves will slowly decrease the pH, gradually turning the solution orange and then yellow. This color change is an indication that even in the absence of contamination, the medium needs to be replaced. Shown to be a weak estrogen mimic (possible through inpurities), which can enhance the growth of cells that express the estrogen receptor in cell cultures. Might be useful as a differentiation factor.

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5,5'-Dithiobis(2-nitrobenzoic acid) (Ellmans reagent, DTNB)

Supplier: Adipogen

A sensitive reagent for measuring the free sulfhydryl content in proteins, peptides, and tissues. Used to characterize reactive thiol groups and photometric determination of thiols and for measuring low-molecular mass thiols such as glutathione in both pure solutions and biological samples, such as blood. It can also measure the number of thiol groups on proteins. Through reaction with aliphatic thiol groups a mixed disulfide of protein thiol and one mole of 2-nitro-5-thiobenzoate per mole of protein sulfhydryl group is being formed. DTNB has little absorbance. Reaction with -SH groups on proteins (from any solvent accessible Cys) under mild alkaline conditions (pH 7-8) produces the 2-nitro-5-thiobenzoate anion, which gives an intense yellow color with an absorption maximum at 409.5nm (Extinction coefficient: 14150 M-1*cm-1). Sensitive to various buffer ions, therefore, the extinction coefficient used to calculate the number of sulfhydryl groups must be matched to the reaction conditions. In case the thiol groups are in disulfide bonds, they must be reduced under anaerobic conditions prior to reaction with DTNB.