FRACTO-SCANTM Ultraviolet Photometer for Monitoring Liquid Effluent
BUCHLER INSTRUMENTS
The highly stabilized deuterium light source provides a uniform energy band thus permitting the selection of any wave length in the UV range. Simplicity of operation, automatic base line compensation, four sensitivity ranges and an output linear in optical density are combined in the most stable and advanced UV monitor now available. The versatile Fracto-Scan can be used with any fraction collector. Write today for complete information.
BUCHLER INSTRUMENTS DIVISION NUCLEAR-CHICAGO CORP. ,
,
A SUBSIDIARY OF G. D. j S E A R L E | & CO
1327 SIXTEENTH STREET. FORT LEE, NEW JERSEY, 07024
Request Bulletin AC 3-5100A CIRCLE 17 ON READER SERVICE CARD
MPI
MODULAR SYSTEMS
FLEXIBLE ELECTROCHEMISTRY SYSTEM The MPI Building B l o c k c o n c e p t provides unusual versatility and perf o r m a n c e with solid state reliability. This modular electrochemistry system accepts inputs from virtually any detector you provide and has over 60 applications to serve your needs. MP-System 1000 applications i n c l u d e : pH, Specific Ion, Polarography, Coulometry, Conductimetry, Auto Titrations, Potentiostats, A m p e r o m e t r y . MP-1666 Console (Includes Plug-in Modules) $1,960. MP-1027 10" Strip Chart Recorder 542. MP-1026 Potentiostat/50w Operational Amplifier 445. MP-1776 Electrometric System (Including Above and Accessories) 3,320. Write for MPI Catalog—Electrochemistry Canada: APTEC Engineering Ltd. 415-937-3630 Netherlands: v. Oortmerssen, N.V. Phone. 4 i s a j ^ J W U M c K E E - P E D E R S E N I N S T R U M E N T S , Box 322, Danville, C a 94526 CIRCLE 11 8 O N READER SERVICE CARD
62 A
·
ANALYTICAL CHEMISTRY, VOL. 4 3 , NO. 10, AUGUST 1 9 7 1
Instrumentation
This should be done immediately after removing the gel from the tube. The gel is laid alongside a ruler and touched at 1-cm intervals with the electrode in such a way that both the glass membrane and the reference junction are in contact with the surface. These measurements take less than 5 min per gel. Comparison of Gel Electrofocusing and Gel Electrophoresis
As shown in Figure 2, gel electrofocusing revealed the presence of at least 18 protein components in crystalline L-amino acid oxidase, whereas only three zones could be separated by gel electrophoresis. It could be shown, by comparing the gels stained for protein with Coomassie blue with similar gels stained specifically for L-amino acid oxidase activity using a staining solution containing L-leucine, phenazine methosulfate, and nitroblue tetrazolium, that all of the protein bands possessed enzymatic activity. The possibility was considered that those results could represent an artifact arising from an interaction between the enzyme and the gel or from an alteration of the enzyme in the course of purification. However, such artifacts were ruled out by showing that a similar pattern of zones was obtained when electrofocusing was conducted in a sucrose density gradient or when untreated snake venom was electrofocused in gels and stained for enzymatic activity (10). It ma}" therefore be concluded that, there are at least 18 isozymes of Lamino acid oxidase, perhaps a larger number than has been found for any other enzyme. This raises many interesting questions concerning the nature of the chemical differences between the isozymes, their origin, and their physiological significance. It seems probable that when other enzymes are examined by this technique, there will be other cases where a greater multiplicity of forms will be found than were previously known to exist. Several examples of such heterogeneity have already been discovered bv usina: the sucrose gradient technique (16).
These results indicate that the resolution obtainable from gel electrofocusing is considerably greater than that of gel electrophoresis. There are several reasons for this. One is that, whereas in the course of electrophoresis protein bands become increasingly diffuse, in eleetrofusing they are sharpened and maintained sharp by the electric field. Another is that differences of a fractional charge, which may not contribute an appreciable difference in electrophoretic mobility, may result
