628 SHORT COMMUNICATIONS

C. VAN DER HEIDEN J. DESPLANQUE

Wilhelm& Children’s Hospital Department of Pediatrics University of Utrecht Nieuwe Gracht 137 Utrecht, The Netherlands

Received December 4, 1970

Aid for Photographing Polyacrylamide Disc

Electrophkresis Gels

Analytical polyacrylamide disc electrophoresis is used in many areas of biochemistry and microbiology. One of the more desirable methods of permanently recording the profiles of stained zones is to photograph the gels. Generally, this technique involves placing the gels in glass vials containing aqueous liquid and placing them on top of a diffuse light source. With this as the only light source an overhead camera records the images of the gels. This procedure provides a partial magnification of the gels and the resultant photographs yield good representations of the band profiles. However, frequent problems are: (a) presence of air bubbles, (b) alignment of the gels, and (c) in particular, loss of resolu- tion caused by a reflection or scattering of light from the liquid or glass vial. In another procedure the gels are not placed in glass vials but are laid directly on the top of the diffuse light source. Photographing the gels in this manner results in limited reproduction of the band profiles, and the gels are difficult to handle. In this case decreased resolution results from the reflection of light off the glistening gel surfaces.

We have designed a device which enhances the photographic repro- duction of the band patterns (I). ‘This aid consists of semicircular troughs milled from a flat section of Plexiglas or other acrylic polymer using a 3/8 in. round cutter (Fig. 1). The circular wells or troughs are about 8 mm wide and 3 mm deep. The grooved surfaces are buffed to obtain maximum translucency. Most disc gels are formed in 5 mm tubes but after extrusion usually expand to at least 6 mm in the fixing and wash- ing process.

The gels are laid in the troughs of the supporting plate, after which

SHORT COMMUNICATIONS 629

r

FIG. 1. Diagram of Plexiglas support for holding and photographing disc electro- phoresis gels.

the plate is placed on a diffuse light source and photographed from above. The troughs provide for a solid Plexiglas to gel contact at the bottom and also approximately halfway up the sides of the gels. This design utilizes the “light piping effect” of acrylic polymers and provides for more parallel channeling of the light through the gel to the film. Maximum contact of the gel with the curved surface results in photo- graphs with sharper contrast and better resolutions of the bands. In ad- dition, the gels do not roll or slide and are easily aligned for viewing. Plexiglas holders with other than semicircular troughs do not provide satisfactory gel-to-plate contact and do not minimize reflections.

REFERENCES

1. PHILLIPS, M., J. R. THURSTON, AND A. C. PIER, Amer. Rev. Resp. Dis. 101, 545 (1970).

ROBERT PATTERSON MARSHALL PHILLIPS

630 SHORT COMMUNICATIONS

National Animal Disease Laboratory Veterinary Sciences Research Division Agricultural Research Service, USDA Ames, Iowa 60010

Received December SO, 1970

Microrespirometer Based on Oxyhemoglobin Utilization

as Oxygen Donor and Indicator

In previous papers a spectrophotometric method was described for assay of mitochondrial oxygen uptake using oxyhemoglobin as the oxygen donor and, at the same time, as an indicator (l-) . The maximal sensitivity is achieved at 430 nm, where a~,,,,~ = 81 (Aemeq = Emeq Hb -

emeqHbo2), In order to simplify and standardize the method for micro-

A

#

Q

e+

& *!

@

B

100 - 100 -

-i -i E E c c 10 - 10 -

‘; ‘; _E _E

4; 1 - 4; 1 - I I Cs-Sb pho toca thode Cs-Sb pho toca thode

0.p I # I I L 1 III

400 600 400 600 1000 1000 1400 1400

X (nm) X (nm)

FIG. 1. Schematic representation of microrespirometer based on HbO, utilization as oxygen donor and indicator: (1) Alternate current stabilizer; (2) Hg lamp (40 VA); (3) interference filter for 435.3 nm, with a strip for 10 nm; (4) spectro- photometric cell; (5) photodiode DF.2 (IPRS-I3 Bneasa) corresponding to PHG.2 Cosem-Silec photodiode; (6) 10 mV full-scale deflection recorder (input impedance 5 Kn). Mean values of differential spectral sensitivity (pA.lm-l.nm-‘) for a Ge photodiode (integral sensitivity of about 100 mA.lm-‘) and Cs-Sb photocathode (integral sensitivity of about 10 pA.lm-I) are shown in B.