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ABI/Invitrogen, Bruker/Serva Launch Rival Quantitative Labeling Reagents

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SAN ANTONIO — Mass spec players Applied Biosystems and Bruker have each partnered with a consumables company to market new quantitative labeling technologies, the companies independently announced this week.

Applied Biosystems is partnering with Invitrogen to co-market its SILAC and its own well-known ICAT and iTRAQ labeling reagents, while Bruker will be sidling up with Heidelberg, Germany-based Serva Electrophoresis to market a new type of labeling reagent called ICPL. Both moves are designed to help all four companies gain broader markets.

On the ABI/Invitrogen front, the SILAC technology, which stands for Stable Isotopic Lableling using Amino Acids in Cell culture, has been exclusively licensed to Invitrogen. SILAC, originally developed in Brian Chait's laboratory at Rockefeller University, is different from ICAT and iTRAQ in that it labels proteins and peptides in cell culture by incorporating special amino acids, rather than labeling cell lysates.

"The customers that Invitrogen has traditionally had are biologists, and that's not really the market that ABI's had in the past," said Lori Murray, a spokeswoman for ABI. ABI has traditionally been geared towards mass spec users, she added.

Greg Geissman, an Invitrogen spokesperson, said his company's move into the mass spec market is a "natural progression" and added that the company is "looking to create a total system."

Cheri Walker, vice president of proteomics at Invitrogen added, "It totally makes sense to have the full portfolio of tagging technologies. The [ABI and Invitrogen] teams work really well together."

On the Bruker front, the company's newly launched ICPL, or Isotope Coded Protein Label, was originally developed and patented by Friedrich Lottspeich and Josef Kellerman at the Max-Planck Institute of Biochemistry. The technology was licensed exclusively to Serva, which decided that it would benefit in having a broader market by partnering with Bruker.

ICPL works by tagging all lysine side chains, introducing a mass difference of six Daltons per labeled site. According to Bruker CEO Frank Laukien, ICPL has advantages over ICAT in that it has very broad coverage by labeling lysines instead of cysteines. In addition, the labeling technology increases the sensitivity during mass spec analysis by as much as a factor of 10.

When compared with iTRAQ, ICPL has similar coverage, but it is more convenient in that it can be used with a single MS run, instead of having to be used with MS/MS, Laukien said.

Market Reaction Varies

However, several quantitative-proteomics researchers noted that ICPL has disadvantages over iTRAQ in that it is not isobaric — it can compare only two samples at once, whereas iTRAQ can compare as many as four.

"In terms of which is better, that's a matter of opinion," said Darryl Pappin, a principal scientist at ABI who gave a talk on quantitative mass spectrometry during the American Society for Mass Spectrometry conference, held here this week. "My test of a good product is anything that's been around for five years."

James Pesavento, a graduate student in Neil Kelleher's laboratory at the University of Illinois at Urbana-Champaign, who also gave a talk on protein quantitation, said that for the work he does, SILAC is most appropriate. However, he prefers to use homebrewed amino-acid labeling products because they are cheaper than the newly available commercial SILAC kits.

"The cheaper the better," said Pesavento. "We make all our own stuff. We have an in-house [employee] that produces all the reagents for a very low wage. It all comes down to price — if homebrew is cheaper, then it's better."

In terms of cost, SILAC is competitive with ICAT, said Geissman. It costs $1,195 per kit, with each kit containing enough reagents for four to 20 experiments, depending on the abundance of the proteins.

According to Victor Fursey, the director of sales and marketing at Bruker, ICPL is slightly cheaper than ICAT, which costs about $1,500 per 10-reaction kit. It is comparable to iTRAQ, which costs $995 for a kit containing enough reagents to last for 10 duplex experiments, six triplex experiments, or five quadruplex experiments.

Martin Ether, a postdoc at the University of Ottawa who is about to start doing quantitative proteomics experiments, said that he is glad that SILAC is now commercially available through Invitrogen and ABI.

"We'd rather spend money than waste our time trying to homebrew," he said. "We would rather go with a kit that we know will work."

Ether had not heard of ICPL, but said that since his lab is growing cells, SILAC would be the most suitable technology to use.

To complement its new labeling technology, Bruker updated its Proteineer-LC mass spectra analysis software to enable quantification analysis.

"Proteineer-LC 1 was mostly about identification," said Fursey. "Proteineer-LC 1.1 enables quantitative analysis to be done in either LC-MS or LC-MALDI mode."

Geissman said ABI and Invitrogen may collaborate in the future to co-develop quantification software that is compatible with SILAC. ABI currently markets ProICAT software for quantitative analysis of ICAT experiments, and ProQuant software for quantitative analysis of iTRAQ experiments.

— Tien Shun Lee ([email protected])