Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Caltech chemists say antibody surrogates are just a 'click' away

14.07.2009
Chemists at the California Institute of Technology (Caltech) and the Scripps Research Institute have developed an innovative technique to create cheap but highly stable chemicals that have the potential to take the place of the antibodies used in many standard medical diagnostic tests.

James R. Heath, the Elizabeth W. Gilloon Professor and professor of chemistry, along with K. Barry Sharpless, the W. M. Keck Professor of Chemistry at the Scripps Research Institute and winner of the 2001 Nobel Prize in Chemistry, and their colleagues, describe the new technique in the latest issue of Angewandte Chemie, the leading European journal of chemistry.

Last year, Heath and his colleagues announced the development of the Integrated Blood-Barcode Chip, a diagnostic medical device, about the size of a microscope slide, which can separate and analyze dozens of proteins using just a pinprick of blood. The barcode chip employed antibodies, proteins utilized by the immune system to identify, bind to, and remove particular foreign compounds, such as bacteria and viruses—or other proteins.

"The thing that limits us in being able to go to, say, 200 proteins in the barcode chip is that the antibodies that you use to detect the proteins are unstable and expensive," says Heath. "We have been frustrated with antibodies for a long time, so what we wanted to be able to do was develop antibody equivalents—what we call 'protein capture agents'—that can bind to a particular protein with very high affinity and selectivity, and that pass the following test: you put a powder of them in your car trunk in August in Pasadena, and you come back a year later and they still work."

In the new work, Heath and his colleagues, including Caltech graduate student Heather D. Agnew, the first author on the Angewandte paper, have developed a protocol to quickly and cheaply make such highly stable compounds, which are composed of short chains of amino acids, or peptides. "I actually traveled to Chicago with a vial of my capture agents as airline carry-on luggage, and came back with it, and the reagent still worked," says Agnew.

The technique makes use of the "in situ click chemistry" method, introduced by Sharpless in 2001, in which chemicals are created by joining—or "clicking"—smaller subunits together.

To create a capture agent for a particular protein, the scientists devised a stepwise approach in which the first subunit of the capture agent is identified, and that unit, plus the protein, is used to identify the second subunit, and so on. For the first subunit, a fluorescent label is added to the protein, which is then incubated with a bead-based library of tens of millions of short-chain peptides, representing all the potential building blocks for the capture agent. When one of those peptides binds to the protein of interest, the fluorescent label is visualized on the bead (red, blue, or green, depending on the type of label), allowing the linked protein–peptide complex to be identified.

That first peptide—which is about a third of the length of the final capture agent the scientists are trying to make—is then isolated, purified, and modified on one end by the addition of a chemical group called an alkyne. This is the anchor peptide, which is then incubated, together with the same protein, with the bead-based library. The bead-based library now contains peptides that have been chemically modified to contain an azide group at one end. The alkyne group on the added peptide can potentially chemically react with the azide group of the library's peptides, to create a new peptide that is now two segments long.

However, the reaction can only occur when the second peptide comes into close contact with the first on the surface of the target protein, which means that both must have affinity for that protein; essentially, the protein itself builds an appropriate capture agent. The two-segment-long peptide is then isolated and purified, "and then we modify the end of THAT with an alkyne, and add it back to the library, to produce a three-segment peptide, which is long enough to be both selective for and specific to the target protein," Heath says.

"What Heath has shown now is that in several iterations, a high-affinity ligand for a protein can be created from blocks that do not bind to the protein all that well; the trick is to repeat the in situ screen several times, and the binding improves with every iteration," Sharpless says.

"This is about as simple a type of chemistry as you can imagine," says Heath. The process, he says, makes "trivial" the "Herculean task of finding molecules that bind selectively and with high affinity to particular proteins. I see no technical reason it couldn't replace any antibody."

The paper, "Iterative in situ Click Chemistry Creates Antibody-Like Protein Capture Agents," was published in the June 22 issue of Angewandte Chemie, and highlighted in an editorial in the June issue of Nature Chemistry. The other coauthors are, at Caltech, Rosemary D. Rohde, Steven W. Millward, Arundhati Nag, Woon-Seok Yeo, Abdul Ahad Tariq, Russell J. Krom, and Vanessa M. Burns; and, at the Scripps Research Institute, Jason E. Hein, Suresh M. Pitram, and Valery V. Fokin.

The work at Caltech was funded by the National Cancer Institute and by a subcontract from the MITRE Corporation.

Kathy Svitil | EurekAlert!
Further information:
http://www.caltech.edu

More articles from Life Sciences:

nachricht Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

Im Focus: Newly proposed reference datasets improve weather satellite data quality

UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration

"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...

Im Focus: Repairing defects in fiber-reinforced plastics more efficiently

Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.

Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Multiregional brain on a chip

16.01.2017 | Power and Electrical Engineering

New technology enables 5-D imaging in live animals, humans

16.01.2017 | Information Technology

Researchers develop environmentally friendly soy air filter

16.01.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>