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How Gel Documentation Systems Work

Scientific Imaging Systems in India This post is about a fascinating product - Gel Documentation System. This is an imaging system, that works it magic downstream of another fascinating lab technique called electrophoresis, which itself s nothing short of magic. Come to think of it - Kurt Vonnegut said “Science is magic that works”.


So in electrophoresis, under the influence of a DC electrical field, samples containing DNA or RNA or protein molecules move in a sponge like material called a gel. As these molecules travel from one electrode to the other, the smaller molecules move faster through the gel. With a sample containing different sizes of molecules, the smaller molecules move farther away from the sample holding well, leaving the larger molecules behind. So what happens is a separation of DNA (or RNA or protein) along its path.

Electrophoresis Gel Image stained with EtBr and UV excitation
Electrophoresis gel images captured captured in Gel.LUMINAX gel doc

So as you can see the lanes (12 in the above image), starting from each sample well (rectangular row at the top), create a pattern of bands. The bands are unique to the DNA and since DNA itself is unique to each individual (or organism), the pattern of bands is also unique. Hence, from these bands you can compare a known sample with an unknown sample and find out if it is the same DNA. Voila, DNA finger-printing! But why is the above image orange-y, fluorescence-y and a negative?! This is because of a gel documentation system. These bands of DNA are not observable to the human eye since they are colourless. So the gel is stained with certain chemicals that stick to just the DNA molecules. These chemicals again are not visible the naked eye as such… So why use them! Because this is where the magic comes in! These chemicals are not visible in well, visible light - that is, white light (sun-light or white LEDs or tube lights or incandescent bulbs). But they glow in ultra-violet. This is how the gel looks in visible spectrum - white light...

Gel image viewed in daylight (or white light)
Gel image when viewing in white light

This is how the gel looks when illuminated with ultraviolet light. The orange-y spread is the DNA stained with a chemical called Ethidium Bromide which glows orange in UV...

EtBr stained gel excited by 312nm UV light
UV illuminated Gel

So look at a gel in white light. Nothing! Look at the same gel when illuminated with UV, a glow - almost ethereal! But isn’t looking at UV light a bit risky? Yes, it is. So enter… Gel Documentation System or Gel Doc or Gel Imaging System or Gel Analysis System. Different names, same thing. Gel doc systems - as they are called in short - have a UV source (called the transilluminator), and a camera placed inside a dark-room cabinet. The dark room ensures that white light from outside doesn’t enter or UV light from inside the cabinet doesn’t leak outside. We design and develop these systems in India. Ours are affordable systems designed and produced here in India as an alternative to imported systems from US and EU manufacturers like Bio-Rad, Syngene and UVITEC. These gel documentation systems are one amongst a broad range of scientific imaging instruments.

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