On the Structure of Native, Denatured, and Coagulated Proteins

Abstract

In this paper a structural theory of protein denaturation and coagulation is presented. Since denaturation is a fundamental property of a large group of proteins, a theory of denaturation is essentially a general theory of the structure of native and denatured proteins. In its present form our theory is definite and detailed in some respects and vague in others; refinement in regard to the latter could be achieved on the basis of the results of experiments which the theory suggests. The theory (some features of which have been proposed by other investigators) provides a simple structural interpretation not only of the phenomena connected with denaturation and coagulation which are usually discussed (specificity, solubility, etc.) but also of others, such as the availability of groups, the entropy of denaturation, the effect of ultra-violet light, the heat of activation and its dependence on pH, coagulation through dehydration, etc.I. The experimental basis upon which the present theory rests will be briefly described.1. The most significant change that occurs in denaturation is the loss of certain highly specific properties by the native protein. Specific differences between members of a series of related native proteins and specific enzymatic activities of native proteins disappear on denaturation, as the following observations demonstrate:(a) Many native proteins can be crystallized and the crystal form is characteristic of each protein. No denatured protein has been crystallized.

On Rhodopsin in Solution

“…The term denaturation includes a number of diverse changes: primarily the loss of solubility at the isoelectric point; and associated with this in varying degree a loss of specificity, or of ability to crystallize or to spread on a surface, increase in the number of exposed reducing groups, and changes in acid-base properties (Neurath, 1936;Mirsky and Pauling, 1936;Bull and Neurath, 1937). None of these changes has yet been shown to accompany the bleaching of rhodopsin by light.…”

How protein chemists learned about the hydrophobic factor

“…A likely specific role for hydrogen bonds in the maintenance of native protein structure was first stressed with great confidence by Mirsky and Pauling (1936). in a paper that (like Wu's) addressed itself to "denaturation," and hydrogen bonds soon became part of the fashionable dogma.…”

“…But the question of the underlying stability of globular proteins was not one of the themes. There was no mention of hydrophobic forces and even intramolecular hydrogen bonds (Mirsky & Pauling, 1936) are mentioned only in one brief footnote.…”

Effect of Quality and Intensity of Solar Radiation on Injury of Lemon Fruit by Sulphur Treatment in the Field

“…For the sulphur-dusted fruit, analysis of variance indicated no significant differences in the percentages of sulphur-burned fruit when the comparisons were made between large green fruit and small green fruit or between large green fruit and large yellow fruit (table VIII). protein is heated is known to affect the temperature at which it is denatured (29). The sulphur burn noted above was caused by a temperature maintained at 111.7 to 113.8°F for one hour, but the rate of heating before these temperatures were reached is unknown.…”