Lysozyme as a transferase

Our first investigations of the action of lysozyme on tetrasaccharides isolated from chitin showed that lysozyme, like many other known glycosides, is a transferase. Under certain conditions (oligosaccharide concentration 1 to 2%, the enzyme concentration 0.5%) the synthetic process may yield an insoluble chitin-like product. Judging by the increase of the Morgan-Elson reaction, lysozyme digests the tetrasaccharide intensively (figure 44). The trisaccharide reacts after a short induction period. Chitobiose reacts with more difficulty, and the induction period is several hours. Addition of the tetrasaccharide increases the reaction rate considerably, just as in the case of certain glycosidases, e. g. chitobiose is a much worse acceptor of transglycosidic residues than the tetrasaccharide (figure 45). For the present we have no data about the correlation between the rates of formation of low-and high molecular products, nor about the rate of direct hydrolysis. The transglucosilation by lysozyme implies at least three binding sites for the substrate.

KINETICS AND MECHANISMS OF THE PYROLYSIS OF n-BUTANE: PART II. THE REACTION INHIBITED BY NITRIC OXIDE

The kinetics of the pyrolysis of n-butane, when maximally inhibited by nitric oxide, were studied at temperatures from 540° to 610 °C, and at pressures from 30 to 550 mm Hg. The reaction has a short induction period and is accurately of the three-halves order; the activation energy was 65.9 kcal mole−1 and the frequency factor 5.3 × 1016 cc1/2 mole−1/2 sec−1. The reaction was somewhat less inhibited by surface than was the uninhibited reaction. Excess of carbon dioxide had no effect on the rate. The results are explained in terms of a free-radical mechanism for the maximally inhibited decomposition. It is proposed that the initiation step in the inhibited decomposition is mainly C4H10 + NO → C4H9 + HNO. This is followed by the ordinary chain-propagating reactions, and by processes such as C2H5 + NO → C2H5NO. The main chain-terminating step, of the type β + βNO, is concluded to be C2H5 + C2H5NO → C4H10 + NO or C2H6 + C2H4 + NO. This scheme leads to three-halves-order kinetics, and provides a satisfactory quantitative interpretation of the experimental behavior.

A NOTE ON THE USE OF INDIUM FOR REMOVAL OF MERCURY VAPOR IN VACUUM SYSTEMS

It is shown that metallic indium adsorbs mercury vapor quite rapidly after a short induction period. It is suggested that indium may be found useful in removing traces of mercury vapor from vacuum systems.

Oxidation of Compounds Structurally Related to GR-S

The rates of oxidation of 1-phenyl-3-pentene, 1-phenyl-4-hexene, and 1-phenyl-3-vinylbutane have been measured at 100° C and 1 atmosphere of oxygen pressure. 1-Phenyl-2-butene has also been included to complete the sequence 1–4, 1–3, and 1–2 with respect to the structural relationship between the phenyl radical and the point of unsaturation. Information concerning the course of the reaction was obtained both from the rate data and from chemical analysis of the oxidized products. Three stages of oxidation were noted: (1) a very short induction period; (2) an autocatalytic stage which is characterized by a rapidly increasing rate and in which the primary products appear to be peroxides; and (3) a period characterized by a constant rate of oxygen absorption with the formation of such products as acids, esters, carbon dioxide, and water.