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Methods to His Mass Spec

  • Title: Associate Professor, Department of Biochemistry and Molecular Biology, University of Southern Denmark
  • Education: PhD, Odense University, 2000; Postdoc, Australian Proteome Analysis Facility (2000-2002); Postdoc, University of Southern Denmark (2002-2003)
  • Recommended by: Ole Nørregaard Jensen

Martin Larsen says that his forte is mass spectrometry methods development, which is a brief explanation for a wide research mandate. His team of three graduate students and one technician at the University of Southern Denmark works on the development of techniques to characterize phosphoproteins and glycoproteins, as well as to elucidate the molecular mechanisms responsible for beta cell destruction in insulin-dependent diabetes mellitus.

One such technique that Larsen is putting the finishing touches on before submitting for publication is “basically a method to pull out sialic-acid containing peptides from very complex samples.” Sialic acid-bearing glycoproteins are implicated in many human diseases, such as metastatic cancer, so the approach itself “has nice potential for biomarker discovery,” he says.

Larsen was introduced to this corner of proteomics by Peter Roepstorff, who supervised Larsen's doctorate work at Odense University. Roepstorff remains an influence on Larsen's work, as does another collaborator based in Australia.

“I did a postdoc in the Australian Proteome Analysis Facility, and there I met this guy who had lots of ideas,” Larsen says. “It turned out that he's also very, very clever.” That clever collaborator and friend is Philip Robinson, head of the cell signaling unit at the Children's Medical Research Institute in Westmead. Robinson and Larsen have occasion to brainstorm in person at least once a year, as they both review for the Journal for Biological Chemistry, which brings them together for annual editorial board meetings. “I always come home with lots of ideas,” Larsen says.

Looking ahead

Larsen is hard-pressed to predict where proteomics may be headed in the years to come, only because the field is developing at such a fast pace. “I almost wish it would go slower so that we would have the time to actually find and read all of the nice articles that are coming out these days,” he says. Because of his group's wide remit, which includes projects on phosphorylation, glycosylation, biomarker discovery, and mass spec, he says that “there are simply too many things to keep track of.”

That said, Larsen does voice a request for the future of methods development. “If you want to do as much quantification as possible,” he says, “you need more than one quantification technique … so it would be really nice to have a robust method for quantification.”

Publications of note

Earlier this year, Larsen reported the identification of seven new phosphorylation sites in spinach stroma membrane via the use of illumination. To purify the light-derived phosphopeptides, Larsen's team developed a sensitive method using titanium dioxide microcolumns, which results in minimal non-specific binding and can contend with even complex mixtures. In most cases, Larsen says, this method returns “between 70 and 90 percent pure phosphopeptides.” Details of the method can be found in a paper appearing in the Journal of Proteome Research.

Last year, Larsen's work with Peter Roepstorff resulted in a paper describing a newer, faster, and more sensitive technique to characterize low amounts of glycoproteins. Published in Molecular and Cellular Proteomics, the paper calls for the use of sequential specific and non-specific enzymatic treatments to reduce the peptides, followed by microcolumns packed with graphite powder to isolate the small glycopeptides.

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