Color reaction

About: Color reaction is a(n) research topic. Over the lifetime, 1194 publication(s) have been published within this topic receiving 19579 citation(s).

[105] Determination of DNA concentration with diphenylamine

Abstract: Publisher Summary This chapter discusses the determination of DNA concentration with diphenylaraine and describes several other color reactions for DNA. The reaction between deoxyribose and diphenylamine is probably the most frequently used color reaction for the determination of DNA. The chapter focuses on the later modifications for the determination of DNA especially in microorganisms and animal tissues and presents the modifications described by Burton, Croft and Lubran, and Giles and Myers. Croft and Lubran were measuring the DNA in saline washes of human stomachs. The material has a high content of sialic acid, which seriously interferes in several color reactions for DNA, including Button's modified diphenylamine reaction. Sialic acid reacts in this method to give a color with a maximum absorption at 550 mμ. Giles and Myers found that the blank readings could be reduced by omitting the sulfuric acid and adding the acetaldehyde to the individual tubes. They also obtained a worthwhile increase of sensitivity by increasing the concentration of diphenylamine and altering the relative volumes of sample and reagent. Giles and Myers encountered turbidities in their reaction mixtures due to impurities in DNA extracts from plant tissues.

A new color reaction for the quantitation of serum cholesterol.

Abstract: A new color has been formed by mixing cholesterol with FeSO4, glacial acetic acid and H2SO4. This reaction provides a sensitive method for the quantitation of total and free cholesterol using 0.1 ml or less of serum. Proteins may be removed from serum by extraction with acetone-ethanol. These extracts may then be treated directly with the color reagents thereby eliminating time-consuming evaporation procedures. The cholesterol color is stable and can be produced rapidly with small quantities of H2SO4. Color formation occurs at a relatively low temperature which need not be rigidly controlled. The use of low concentrations of H2SO4 and the production of minimal amounts of heat make the serum extracts less susceptible to charring. The accuracy and precision obtained with the proposed procedure validates its use for either clinical or research purposes. The serum total and free cholesterol levels of 200 blood donors measured with the new color reaction were found to agree well with normal values reported by others.

Revised assay for serum phenyl phosphatase activity using 4-amino-antipyrine.

Abstract: A modified method for the assay of serum phosphatase activity utilising disodium phenyl phosphate as substrate is described. This is based upon the reaction of free phenol with 4-amino-antipyrine and alkaline potassium ferricyanide. Study of the kinetics of the colour reaction has led to an alteration in the concentration of the reagents used; the colour is formed instantaneously and shows a very slow rate of decay. Sodium arsenate incorporated with the amino-antipyrine reagent effectively abolishes further enzyme activity and prevents the dilution of the colour inherent in earlier methods.