English for chemists

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In 1926, Sumner made a tremendous advance when he recognized that enzymes were, in fact, proteins. He came to this conclusion after he had successfully crystallized a protein that was associated with enzymatic activity (viz., urease) and noticcd that the degree of degradation of this highlypurificd protein could be correlated with the disappearance of the associated enzymatic activity. Before that time, it was thought that enzymes might be special nonprotcin substanccs that happened to be associated with proteins. In other words, it was thought that some proteins might simply serve as passive, structural supports for enzymes. On the other hand, Sumner’s discovery suggested that the enzymatic activity was related to the structure of the protein per sc. In the 1930s Northrop and Kunitz purified and crystallized many enzymatic proteins and, thus, confirmed Sumner as the father of modem cnzymatology.
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Characteristics of Mossbauer Spectra
To obtain a resonant gamma-ray absorption spcctrum it is ncccssary to relate the transmission intensity to the instantaneous sourcc-absorbcr velocity. In practicc there arc a number of methods which can be used to accomplish this, and these can be roughly divided into two groups: those which employ constant velocity drives and those which employ continuously reliable velocity drives. The characteristics and advantages of cach of these systems have been discusscd in detail by Wcrthcim and elsewhere. In the present discussion we shall not explore any of these methods in detail, but will conccm ourselves only with the details of the spcctra which arc obtained.

A typical Mossbauer spcctrum is a characteristic plot of the total number of events (counts) observed as a function of sourcc-absorbcr velocity (the standard convention is to represent motion of the source toward the absorber by positive velocities and motion of the source away from the absorber by negative velocities).

The profile of the rcsonancc maximum obeys (ideally) the Lorcntz

relationship:

constant