2DIR imaging technique basis for future single-cell protein analysis tool

OCTOBER 6, 2008 -- Researchers at Imperial College London say they have discovered the first new method in more than 20 years for identifying proteins. Their technique, coherent two-dimensional infrared spectroscopy (2DIR), maps energy flow inside a protein. The scientists hope to develop a tool based on the technology to determine proteins and their concentrations within a human cell. Proteins are involved in every process in human cells, including cancer growth.

OCTOBER 6, 2008 -- Researchers at The Single Cell Proteomics group at Imperial College London say they have used an imaging technology known as coherent two-dimensional infrared spectroscopy, 2DIR, to successfully identify proteins in laboratory tests. The new technique enables scientists to identify proteins by making a map of the energy flow inside them. The scientists hope to develop a tool that can analyze individual human cells to determine which proteins are present and in what quantities. Being able to sensitively analyze the protein make-up of cells is important because proteins are involved in every process in human cells, including the development of cancer.

The 2DIR technique uses an ultra short pulse of infrared laser light to cause a vibration in one part of the protein molecule. The researchers then track the movement of energy from this vibration as it moves through the protein, building up an energy flow map of the protein -- which enables them to identify what kind of protein it is.

Professor David Klug, one of the authors of a paper describing the work, explains the significance of the study: "We have proved the principle that it is possible to use this type of spectroscopy to identify proteins and we are now looking to use this knowledge to develop a new tool that can be used to further a broad range of research including drug discovery, diagnostics, biomarker discovery and basic biology.

"This is the first time in over 20 years that a new method for identifying proteins has been discovered, and we're very excited about the possibilities that it will bring to our field."

Professor Keith Willison, Professor of Molecular Cell Biology at The Institute of Cancer Research and also an author on the paper, adds: "the development of new single cell, single molecule approaches is vital in the hunt for rare cancer cells."

The technologies under development in the Single Cell Proteomics Project are focused on improving the sensitivities of proteomic tools to allow single cells to be analyzed. Currently, scientists identify and count proteins either by using antibodies or mass spectrometry. The new third potential method, 2DIR, has advantages over the existing methods because it could be more sensitive and provide additional information on how protein activity and function is modulated within cells. "Counting the number of proteins is important, but not enough to understand the biology at work," says Professor Klug.

Potential applications of these methods include the possibility to analyze single cancer cells found circulating in the bloodstream of patients and in the discovery of new biomarkers that might ultimately be used in screening and diagnosis.

The study of proteins, known as proteomics, is the next step for scientists following the identification of all the genes in human DNA in the human genome project. All human cells contain the same 20,000 genes but in different cells different genes are 'switched on' to produce different proteins, and it is the differences between proteins which distinguishes one type of cell from another, and a healthy cell from a diseased cell.

The Single Cell Proteomics group at Imperial College London was established in 2006 with £5 million funding from the EPSRC and BBSRC and will run for five and a half years. Professor Keith Willison, Professor of Molecular Cell Biology at The Institute of Cancer Research, is a co-holder of the £5M grant and a collaborator on this research.

The paper is published in the Proceedings of the National Academy of Sciences (PNAS) journal

More information:
Paper in Proceedings of the National Academy of Sciences
Imperial College London's Single Cell Proteomics project

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