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Angelika Görg Talks about Perfecting the Art of 2-Dimensional Gels

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At A Glance

Name: Angelika Görg

Position: Professor and head of proteomics group, Life Science Center, Technical University Munich

President, German Electrophoresis Society, since 1992

Background: PhD, Technical University Munich, 1973

Habilitation/Professorship, Technical University Munich, 1989

 

How did you get into proteomics?

In 1969, when I was working on my PhD thesis at the Technical University in Munich, I was studying proteins by isoelectric focusing [which later became the first dimension of two-dimensional gel electrophoresis] using carrier ampholytes in tube gels.

The goal of my project was to differentiate varieties of plants and fruits, and to study the influence of environmental conditions. For example, I had to compare varieties of strawberries grown under different conditions. Nobody was around to teach me, so I just learned by trial and error, and I got deep into the technology. It was quite frustrating, because these tube gels varied a lot. In fact, once I wanted to repeat experiments from the previous year with a new harvest of strawberries and I used a new batch of carrier ampholytes. I obtained different protein patterns, because it turned out the carrier ampholyte pH gradients are batch-dependent. At that point, I almost quit my PhD project.

But this missing reproducibility also motivated me to develop an alternative to tube gels, so I went on to develop thin gels on plastic backings. That was my first method development; I mainly wanted to save on carrier ampholytes because they were so expensive at that time. I always got into trouble with my boss about the bills! So I decided to reduce the gel thickness, and that was only possible when you cast the gel on a plastic backing. I first used this technique to cast gradient SDS gels, but later this became the technique for casting immobilized pH gradient gels for 2D gels.

How did you develop 2D electrophoresis with immobilized pH-gradients?

In 1981, I gave a talk in Charleston about ultra-thin gradient gels on plastic backings. Ben Bengt Bjellqvist from LKB, a Swedish company that was bought by Pharmacia in the 1980s, approached me afterwards and asked me if I wanted to be involved in a project to develop immobilized pH-gradients on plastic backings — this was nicknamed the “Smear project.” Working in Munich, I helped them get it running and continuously refined the technique. In 1989, these pH-gradients were mature enough for commercialization, and were introduced by Pharmacia Amersham as IPG strips.

The main advantage of IPG strips, where the gradient is fixed in the gel, is that you can focus for hours and hours, even days, and the gradient will not move. This makes the method extremely reproducible. Also, you can apply much more protein, up to 15 mg.

What did you do after your PhD?

I stayed at the Technical University in Munich, where I did a lot of teaching of undergraduates and also developed protein separation and electrophoresis techniques. In my lab there are a lot of chemistry and engineering students — which has always been a creative combination. Then, in 1986, Sam Hanash invited me to the University of Michigan to introduce immobilized pH gradients in his lab, after he had heard me talk about it at a meeting. He was one of the first people [studying proteins by 2D gel electrophoresis] to pick up this new technique.

When did 2D gels experience their proteomics boom?

In the 1980s, everybody cared only about genomics, and nobody about proteins. There were only a few of us studying proteins by 2D gels back then, which was basically comparing two-dimensional maps of spots, [without being able to identify the proteins.] For a long time, I have been president of the German Electrophoresis Society, and we have had these meetings, including the international biannual Siena meetings. Proteomics started around the time of the 1996 Siena meeting — all of a sudden, everybody was doing 2D electrophoresis. Today, most high-throughput proteomics labs use 2D electrophoresis, in combination with mass spectrometry. This is now called “classical proteomics.”

How long do you think are 2D gels here to stay?

Certainly other techniques are being developed that are complementary. But I think for the moment, there is no replacement for 2D gels. It’s still the only method which can separate thousands of proteins at a time, which is not feasible with other techniques. Things will of course always move, but at the moment, 2D gel electrophoresis is the proteomics workhorse.

Where do you see room for improvement for 2D gels?

It would be best to have a robot that does everything, but I think that’s not realistic: It’s too expensive for most labs. However, there is potential for automation of certain steps such as spot picking, in-gel digestion, and transfer of samples to the mass spectrometer.

Another area for improvement is protein detection. [Amersham’s] DIGE is one of these technologies, where you label two samples with two different dyes, then run them on the same gel. Using two different wavelengths, you can create two images and overlay these spot maps. This technique has recently become available to academic laboratories. Another challenge is sample preparation. My lab, for example, has recently developed a pre-fractionation method that separates proteins by pI using Sephadex isoelectric focusing. This way you can prepare a sample for a narrow pH range on a 2D gel and look for low-abundance proteins. The pre-separated proteins are electrophoretically transferred to the IPG strip.

Will this be commercialized at all?

I have gotten offers to commercialize it, but it’s not [certain] yet when it will be available.

What is the focus of your current research?

I apply 2D gels in many different areas; I collaborate with a lot of different groups that work with organisms like Arabidopsis, yeast, Lactobacillus, and Corynebacterium. We look, for example, for proteins related to stress, or related to certain diseases. It’s not easy to detect these proteins: It’s much easier to see the proverbial needle in the haystack. Since 1992, I have also run about 30 one-week courses, teaching people how to run 2D gels with IPGs. I run about four every year, and they are always fully booked, and people from all over the world attend. Participants bring their own samples which they run during the week in our laboratory. I think this is the best way to learn the technique: It’s really hands-on.

Where do you see proteomics going?

We are all waiting for the first results in drug development, of course. I think everybody now is expecting a lot from proteomics, so we are all under a lot of pressure.

In terms of the science, I see a lot of techniques joining together. For example, there is a revival of classical biochemistry that’s now used in proteomics. It is not anymore just 2D gels coupled to mass spectrometry; we have more and more of these satellite fields arising that deal with protein characterization.

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