Molecule, acetone proteins

Figure 47.4. Chemical modification of the protein with a water-insoluble reagent in the reverse micelles of Aerosol OT in octane. (1) Protein molecule incorporates into the inner water pool of the reverse micelle, acquiring a monolayer cover of the hydrated surfactant molecules. (2) The modifying reagent incorporates into the surfactant layer of the micelle coming into contact with the modified group of the protein. (3) Following the completion of the reaction the modified protein is precipitated and the surfactant and excess of the reagent are removed by adding cold acetone. Proteins modified with fatty acid residues with controlled and low degree of modification are obtained.

The spirit is to show some of the results, but also to guide users of the approach by pointing to the problems and limitations of the method. The review covers some of the newer applications in the spectroscopy of organic molecules acetone, methylenecyclopropene, biphenyl, bithiophene, the protein chromophores indole and imidazole, and a series of radical cations of conjugated polyenes and polyaromatic hydrocarbons. The applications in transition metal chemistry include carbonyl, nitrosyl, and cyanide complexes, some dihalogens, and the chromium dimer. 

The conceptual idea of a theoretical plate can be used in SEC to measure column efficiency and to compare the performance of packed coluians. For column comparisons it is usually measured with small molecules, such as toluene, acetone or benzyl alcohol, which can explore all of the pores of the packing (K jc - 1). Plate counts measured in this way produce HETP values lower than the actual values measured with monodisperse polymers and proteins. The plate count in this case can be expressed by equation (4.40)... 

Fluorescence quenching has proven to be a powerful means to determine location of tryptophans. Small organic molecules, such as acetone, acrylamide, and amino acids, have been used to quench fluorescence of tryptophans which are exposed to the solvent.(50 51) These molecules apparently quench by close interaction and so provide a tool to determine the surface accessibility7 of tryptophan in a protein. 

O Ketoacidosis is a dangerous condition that is characterized by the acidification of the blood and an acetone odour on the breath. The condition occurs when levels of oxaloacetic acid for the citric acid cycle are low. This leads to a buildup of acetyl CoA molecules, which the liver metabolizes to produce acidic ketone bodies. Since carbohydrates are the main source of oxaloacetic acid in the body, high-protein, low-carbohydrate diets have been linked to ketoacidosis. 

Organic solvents. Addition of organic solvents decreases the solubility of proteins by reducing the dielectric constant of the medium. For the precipitation of enzymes, methanol, ethanol or propanol are mostly used, but acetone and diethyl ether can also be employed. The principal disadvantage of organic solvents is their tendency to cause stmctural damage of enzyme molecule. 

Chlorophyll is a nonpolar molecule so it is soluble in most organic solvents. Acetone disrupts protein-pigment complexes (see Experiment 8). A more efficient extraction could be achieved if several extractions were carried out and the extracts pooled. 

Unfortunately, 2,2 -dipyridyl disulfide is relatively insoluble in aqueous buffers. The use of this compound to modify molecules usually involves prior dissolution in an organic solvent such as acetone and then performing the blocking reaction in an aqueous/organic mixture. Many proteins will not tolerate high concentrations of organic solvents without precipitation. 

This is a simple, direct procedure - that does not require the preparation and isolation of an active derivative. The coupling procedure is carried out directly with the hapten, and the product usually contains 1 -25 hapten groups per molecule of albumin. As an example of this method, the coupling of cortisone-21-hemisuccinate to protein is illustrated (Fig. 2). The haptenic group was converted in situ to an acid anhydride, which could then react in an aqueous-acetone solution with the amino groups of serum albumin. 

Another common chemical additive utilized to reduce protein solubility is small, polar organic molecules such as methanol, ethanol, and acetone. Such water-miscible solvents are often called anti-solvents. The most widely known separation utilizing such solvents is the Cohn method of blood fractionation, which utilizes ethanol for the recovery of a variety of proteins from blood (Cohn et al. 1940). Such separations are usually carried out near the isoelectric point in order to bring the protein to a point of minimal solubility and minimize the amount of anti-solvent required to achieve the precipitation or crystallization. 

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