Proteins give several colour reactions and are often useful in identifying the nature of amino acids.
All proteins rotate the plane-polarised light to the left; that is, these are laevorotatory. Example: Specific rotation [α]D for ovalbumin is near –30° over the pH range 3.5 × 11. However at lower or higher pH values the rotation becomes more negative eg at pH 13, the [α]D is about –60°.
The process of protein precipitation by the addition of neutral salts such as ammonium sulphate or sodium sulphate is known as salting out. This phenomenon is explained on the basis of dehydration of protein molecule by salts. This causes increased protein, protein interaction, resulting in molecular aggregation and precipitation.
The addition of small quantities of neutral salts increases the solubility of proteins. This process is called salting. Due to the diminished protein, protein interaction is at low salt concentration.
The solubility of proteins usually depends on the pH. It is lowest at the isoelectric point and increases with increasing alkalinity or acidity. The reason is that as protein molecules exist as either cations or anions, repulsive forces between the ions are high and hence the proteins possess excess charges of the same sign. Thus,…
Benzene may be oxidised to mono-, di-, and tri-hydroxy phenols as shown below. If the aromatic hydrocarbon contains alkyl group, it is oxidised to acid.
Aliphatic and aromatic alcohols undergo oxidation to form the corresponding acids. Methanol is a highly toxic substance that when it is consumed, it produces blindness.
A large number of foreign compounds, which include alcohols, aldehydes, amines, aromatic hydrocarbons, and sulphur compounds, are detoxified by the process by oxidation. In general, aliphatic compounds are more easily oxidised than aromatic.
The reaction of phase II is conjugation. Generally, detoxification of a compound involves phase I as well as phase II reactions. It is shown in Figure 12.1. Figure 12.1 Detoxification of a Compound
The reactions of phase I are oxidation, reduction, and hydrolysis.