SECTIONAL TRANSACTIONS.—B. 361 
Prof. E. WaLpscumipT-LeE1Tz.—Some aspects of enzyme action (10.30). 
It has been shown for the first time that, in the case of protein-splitting 
enzymes, there are specific chemical groups both in substrate and enzyme, 
through which the specific reactions between enzyme and substrate take 
place. The various enzymes can be differentiated according to their 
different modes of reaction with both polypeptides and true proteins. 
Several examples are given. 
The activation of enzymes, and its mechanism, are of particular interest. 
It may be explained either by the development of a specific active group, 
through the activator, or by a surface action, e.g. supplying the enzymatically 
active group with a suitable colloidal bearer. It is suggested that enzyme 
action in general is a surface reaction between definite chemical groups. 
Dr. N. K. Apam, F.R.S.—Unimolecular films of fatty substances on water 
(11.10). 
Langmuir showed that insoluble substances such as long chain acids, 
alcohols, fats, sterols, which have one or two water-attracting groups in the 
molecule, form films only one molecule thick on a water surface, with the 
molecules oriented so that the water-soluble groups are next the water. 
These films are found in states corresponding to the solid, liquid, and 
gaseous states of matter in three dimensions, the state of the films being 
determined mainly by the amount of lateral adhesion between the molecules. 
Different films show different degrees of tilt of the molecules ; if there is only 
one water-attracting group, situated at the end of the molecules, they usually 
stand vertically; two widely separated water-attracting groups usually 
cause the molecules to lie flat ; in the interesting ‘ expanded’ state of the 
films the molecules probably have their hydrocarbon chains in violent 
whip-like agitation, yet the films are coherent. 
These films often give valuable information as to the size, shape, and 
constitution of the molecules. 
Dr. A. H. Hucues—Chemical reactions in unimolecular films (11.35). 
Whilst the familiar investigation of unimolecular films by the Langmuir- 
Adam trough has given much detailed knowledge of the physical properties 
of this state of matter, the more recently developed technique of ‘ surface 
potentials ’ has provided a means of measuring a chemical reaction occurring 
in the unimolecular film. The surface potential of a film is related to the 
dipole moment of the constituent molecules ; thus chemical change taking 
place therein is reflected in a change in the observed surface potential. 
Some simple types of chemical change have been examined in this manner : 
(1) Ionisation of a fatty acid, such as myristic or palmitic. 
(2) Oxidation of unsaturated molecules (oleic acid and its isomers and 
various sterols oxidised by acid KMnQ,). 
(3) Hydrolysis of lactones. 
(4) Complex formation, e.g. the reaction of concentrated HCl and a film 
of an alcohol or an acid to form an oxonium compound, and the effect 
of heavy metal ions in the solutions. 
In certain cases, notably the oxidation of oleic acid and the hydrolysis 
of y-stearolactone, the reaction velocity is affected markedly by the orienta- 
tion of the molecules. By suitable compression the molecules in the film 
can be so arranged that the reactive group is not accessible to the reagent 
in the underlying solution. ‘This accessibility factor has been studied in 
