Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Array of light for early disease detection?

23.05.2012
A special feature in the May 11 issue of the journal Science highlights protein array technology, touching on research conducted by Joshua LaBaer, director of the Biodesign Institute’s Virginia G. Piper Center for Personalized Diagnostics.

With the successful completion of the Human Genome Project, research attention is increasingly focusing on proteins. Versatile products produced from genetic templates, proteins are principle actors in both the maintenance of health and the onset of illness. Protein microarrays are a means of bridging the gap between analysis of the nucleotide sequences that make up DNA and the proteome—the universe of proteins built from the amino acids coded for by genes.

Protein microarrays are helping researchers develop early detection methods, particularly for chronic diseases, which account for most of the country’s health care expenditures. Identifying telltale signs of diabetes, coronary artery disease, congestive heart failure and various cancers at an early, pre-symptomatic stage, offers the best prognosis for successful treatment, at dramatically reduced cost.

“Proteins are the machines of biology. Disease is nearly always a result of protein malfunction, and most drugs are designed to affect protein function. Protein microarrays enable us to test the biochemical properties of thousands of proteins simultaneously,” says LaBaer.

While the genome provides the instruction manual for building living systems, proteins are the real molecular workhorses, faithfully carrying out genomic instructions, while also modifying their behavior under myriad environmental influences. Proteins provide structure to cells and tissues, facilitate signaling within and between cells, act as receptors, catalyze enzymatic activity, execute immune functions, and perform countless other biological tasks.

A more thorough understanding of the proteome is therefore vital to diagnostic medicine, particularly for establishing biomarkers—pre-symptomatic indices of early disease states, detectable as protein components in blood. LaBaer’s group is working on discovering biomarkers for a range of deadly illnesses, including, breast, ovarian, lung and oropharyngeal cancers; type I diabetes and assorted infectious pathogens.

Until recently, studying the complexities of proteins, (as opposed to the sequence of four nucleotides making up DNA), has been daunting. A protein microarray usually consists of a library of proteins immobilized on a glass slide or chip in a 2D addressable grid format. Arrays of this sort are made by expressing and painstakingly purifying proteins, then imprinting them onto the slide’s surface. Once a library of proteins has been splayed out on an array, high-throughput methods can be used to investigate their behavior.

Similar arrays have long been used to study DNA, yielding a steady stream of insights into the genome and in some cases providing rapid and accurate diagnostic tools. Researchers would like to repeat the successes of DNA microarrays with protein microarray technology, though a number of hurdles exist. Compared with nucleic acids, proteins exhibit enormous structural diversity and complexity. The synthesis, stabilization and purification of proteins are often laborious undertakings. Adequately attaching proteins to the array surface is tricky and subsequent detection of these proteins through binding events is considerably more complex than in the case of nucleic acid arrays.

Protein microarrays can be broken down into two broad categories. With so-called forward phase arrays, one protein sample is screened against multiple reagents. The capture protein—usually an antibody— is first affixed to the slide surface. The immobilized antibody can then be used to capture antigens it recognizes when a test sample is spread over the array. The test sample could be blood, cells, cell lysates, or some other biological specimen. The captured analyte can then be detected directly, using a fluorescent dye. The technique offers high specificity, but is time consuming.

In reverse phase arrays, the test sample is printed directly on the slide and the array is then detected with a dye-conjugated protein, such as an antibody. One of the key advantages of the reverse phase microarray is a reduction in the number of antibody probes needed to detect a protein antigen. Examples of both forward and reverse arrays are presented in the current Science review.

LaBaer’s group works with a novel protein array, designed in their lab. Known as Nucleic Acid Programmable Protein Array or NAPPA, the technique is particularly powerful because it obviates the need to purify proteins prior to their use in a microarray. Instead of using the protein itself, the NAPPA technique spots protein-coding circular pieces of DNA known as plasmids —the blueprints for building proteins—onto slides, bringing the simplicity and low cost of DNA microarray technology into the world of proteomics.

Immediately prior to the use of the array, an in vitro transcription/translation system is applied as a coating on the slide, turning each array into a nanoscale factory for protein production. Issues of protein stability and purification are avoided, as proteins are synthesized immediately prior to use. (Figure 1 shows a schematic of how NAPPA works.)

“The central concept for NAPPA is to make the proteins ‘fresh’ only moments before testing them and to use the machinery most relevant to the proteins to make them. Currently we are using human ribosomal machinery to make human proteins,” LaBaer says.

LaBaer’s method currently allows some 2300 genes to be arrayed on a conventional microscope slide. Given the vastness of the human proteome, comprised of more than 30,000 distinct proteins, the technique requires around 10 array slides to fully sample the proteome. Spotting DNA plasmids at higher densities requires new imprinting techniques to avoid chemical cross talk between closely situated array spots. Using advanced piezoelectric-pipetting technology, the group anticipates next generation protein arrays that will improve protein densities per slide by roughly an order of magnitude.

Currently, at the Piper Center’s state of the art facility, some 14,000 human proteins are employed in an array in order to detect antibody targets of disease. The technique is being used to investigate posttranslational modifications to proteins and for the identification of novel autoantibodies.

Post-translational changes can occur during or after protein synthesis, resulting in modifications to protein residues. Such changes alter physical and chemical properties affecting protein shape and function. The presence of particular autoantibodies may signal presymptomatic recognition of disease antigens, for example those produced by cancerous tumors. One recent study identified a panel of 28 antigens that can pinpoint early onset breast cancer in blood sera with 80 to 100 percent specificity.

In addition, this research may help speed more effective vaccines to market by identifying immunogenic proteins associated with infectious diseases like cholera, anthrax and Pseudomonas aeruginosa.

“The key to this work,” according top LaBaer, “is to test many patients and many healthy indviduals to determine which responses are specifically found only in the patients. Most important is to confirm these findings in independent experiments. “

Written by: Richard Harth
Science Writer: Biodesign Institute
richard.harth@asu.edu

Joseph Caspermeyer | EurekAlert!
Further information:
http://www.asu.edu

More articles from Health and Medicine:

nachricht UIC researchers find unique organ-specific signature profiles for blood vessel cells
18.02.2020 | University of Illinois at Chicago

nachricht Remdesivir prevents MERS coronavirus disease in monkeys
14.02.2020 | NIH/National Institute of Allergy and Infectious Diseases

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: A step towards controlling spin-dependent petahertz electronics by material defects

The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.

Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...

Im Focus: Freiburg researcher investigate the origins of surface texture

Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.

Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...

Im Focus: Skyrmions like it hot: Spin structures are controllable even at high temperatures

Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices

The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...

Im Focus: Making the internet more energy efficient through systemic optimization

Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.

Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.

Im Focus: New synthesis methods enhance 3D chemical space for drug discovery

After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.

"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

70th Lindau Nobel Laureate Meeting: Around 70 Laureates set to meet with young scientists from approx. 100 countries

12.02.2020 | Event News

11th Advanced Battery Power Conference, March 24-25, 2020 in Münster/Germany

16.01.2020 | Event News

Laser Colloquium Hydrogen LKH2: fast and reliable fuel cell manufacturing

15.01.2020 | Event News

 
Latest News

Journey to the center of Mars

20.02.2020 | Physics and Astronomy

Laser writing enables practical flat optics and data storage in glass

20.02.2020 | Physics and Astronomy

New graphene-based metasurface capable of independent amplitude and phase control of light

20.02.2020 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>