Published Papers

Molecular Architecture and the Processes of Life. May 28, 1948.

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Title:	Molecular Architecture and the Processes of Life [11 of 15]
Creator:	Pauling, Linus, 1901-
Publisher:	Nature.
Date:	1948-05-28
Subject:	Molecular structure
Description:	Nature, vol. 248. Original typescript.
Type:	Text
Format:	text/plain
Language:	en
Identifier:	jessebootlecture-pg11.jpg
Source:	Master scanned with Epson GT-10000+ flatbed scanner at 600 dpi.
Rights:	http://osulibrary.orst.edu/specialcollections/coll/pauling/dna/copyright.html
Full Text:	All atoms attract all other atoms, with the general van der Waals electronic forces of attraction. These forces are weak in case that the atoms are far from one another, and strong only when they are essentially in contact. The forces between a few atoms in an antigen molecule and a few atoms in an antibody molecule would not be enough to produce a bond between the two molecules strong enough to resist the disrupting influence of thermal agitation of the molecules. If, however, the combining region of the antibody molecule is complementary in configuration to a portion of the surface of the antigen molecule, so that a large number of atoms of the antibody molecule are able to bring themselves into contact with corresponding atoms in the antigen molecule, then the integrated forces of attraction become large, enough to constitute a significant bond between the two molecules. Other types of intermolecular interaction-the formation of hydrogen bonds, and the forces of attraction between a positive charge and a complementary negative charge-may also contribute significantly, if the structures are complementary with respect to them also. It is clear that a good approx- imation of the combining region of the antibody to the surface of the antigen can be achieved only by having complementary structures, and if the surface of the antigen were changed by adding onto it a group of atoms even as much as one or two atomic diameters in size, this change might effectively prevent a large part of the combining region of the antibody from getting into satisfactory contact with the surface of the changed antigen, and thus prevent the formation of a significant bond. It is in fact found that even so small a change as the replacement of one of the hydrogen atoms of the benzearsonic acid group by a chlorine atom, which is roughly >0% larger in size (diameter 1.8 A for chlorine, 1.2 A for hydrogen), is enough to interfere with the combination of the molecules with the antibody- homologous to the un- substituted benzenearsonic acid. It is possible to propose a reasonable mechanism for the manufacture of antibody. This mechanism is based upon the concept that a protein molecule is a very long chain of atoms, perhaps a thousand times as great in length as in diameter, which may coil up into a well-defined configuration. The precursor of gamma-globulin, as it is formed in the cells of the body, may be such a long chain, of such a nature that its end portions may coil up into any one of a large number of alternative configurations. In general