Site of the day: http://forums.digitalpoint.com/
ScienceDaily (Apr. 21, 2010) — Understanding how mixtures of proteins assemble and how to manipulate them in the laboratory has many exciting biomedical applications, such as providing scaffolds for the engineering of tissues that can replace diseased or damaged human tissues. Now, research published by Cell Press in the April 20th issue of Biophysical Journal, reveals new information about the kinetics of protein assembly and demonstrates how to manipulate conditions in order to provide different distributions of protein fiber lengths.
"Developing a good understanding of the relationship between the sequence of a protein fiber and its structure, stability and how it folds up and assembles together with other proteins is key and underpins our ability to design new protein-based materials for bioengineering," explains senior study author, Professor Derek N. Woolfson from the School of Chemistry at the University of Bristol in the United Kingdom. "It is also critical to determine the timescale of protein assembly so that the process can be fully controlled and accurately manipulated."
In previous work, Prof. Woolfson and colleagues designed two short peptides that, when mixed together, assembled to form fibers. These peptides were engineered to have "sticky ends" that interacted to form long fibers which exhibited a natural protein structural motif called the "alpha-helical coiled-coil"; a structure where fibrous proteins coil up like the strands of a rope. In the current study, the researchers used multiple sophisticated and complementary biophysical tools along with peptide engineering to gain further insight into the molecular process and timing of going from the small nanoscale peptides to large micron-length fibers.
Using these techniques, the researchers were able to build a specific descriptive mathematical model for the self-assembly of the alpha-helical protein fibers. Prof. Woolfson's group was also able to demonstrate that they could intervene in the assembly process to manipulate the resulting fibrous structures with some precision. "This study and the resulting mechanism we propose present a potential route to temporal control of the assembly of fibers with future applications in biotechnology and nanoscale science and medicine," proposes Prof. Woolfson.
Researchers include Elizabeth H. C. Bromley, University of Bristol, Bristol, UK; Kevin J. Channon, University of Bristol, Bristol, UK; Patrick J. S. King, University of Bristol, Bristol, UK; Zahra N. Mahmoud, University of Bristol, Bristol, UK; Eleanor F. Banwell, University of Bristol, Bristol, UK; Michael F. Butler, Unilever Corporate Research, Colworth Science Park, Sharnbrook, Bedford, UK; Matthew P. Crump, University of Bristol, Bristol, UK; Timothy R. Dafforn, University of Birmingham, Birmingham, UK; Matthew R. Hicks, University of Warwick, Coventry, UK; Jonathan D. Hirst, University of Nottingham, Nottingham, UK; Alison Rodger, University of Warwick, Coventry, UK; and Derek N. Woolfson, University of Bristol, Bristol, UK.
Journal Reference:
Elizabeth H.C. Bromley, Kevin J. Channon, Patrick J.S. King, Zahra N. Mahmoud, Eleanor F. Banwell, Michael F. Butler, Matthew P. Crump, Timothy R. Dafforn, Matthew R. Hicks, Jonathan D. Hirst. Assembly Pathway of a Designed %u03B1-Helical Protein Fiber. Biophysical Journal, 2010; 98 (8): 1668 DOI: 10.1016/j.bpj.2009.12.4309
(http://www.sciencedaily.com/releases/2010/04/100420132833.htm)
Showing posts with label Tissue engineering. Show all posts
Showing posts with label Tissue engineering. Show all posts
Friday, April 23, 2010
Assembly of Protein Strands Into Fibrils
Site of the day: http://forums.digitalpoint.com/
ScienceDaily (Apr. 11, 2010) — Researchers have detailed a basic general mechanism describing how filamentous proteins assemble into ribbon like structures, the so-called amyloid fibrils. Combining experiments and theory, they can explain how denatured milk proteins assemble into ribbon like structures composed of up to five filaments. These findings are shining a surprisingly new light on the assembly of these proteins.
The atomic force microscope depicts on its screen the few nanometer thick and few micrometer long fibers as white flexible sticks, crisscrossing the surface on which they are deposited. The very peculiar property of these proteins lies in fact that they can self assemble into complex ribbon-like twisted fibers.
Researchers at ETH Zürich, EPF Lausanne and University of Fribourg have teamed up to take atomic force microscopy images of the fibers and to analyze them using concepts from polymer physics and theoretical modeling. This combination of expertise has lead them to propose a set of general rules governing the assembly of filaments into thicker and twisted ribbon like fibers. Their results are published in the current issue of the scientific journal Nature Nanotechnology. "The model that we propose is extremely precise in its predictions," says Raffaele Mezzenga, Professor of Food and Soft Materials Sciences at the ETH Zürich. "Up to now there was no such exact and general model for the formation of amyloid fibers," continues Giovanni Dietler, Professor of Physics of Living Matter, at the EPF Lausanne.
The structure of the amyloid fibers as it was unveiled by the experiments, surprised the researchers. Single proteins build the long filaments and subsequently the filaments assemble side by side to form the ribbon-like twisted fibers.
Mezzenga explains that the ribbon-like structure is the logic consequence of the strong charge carried by the building blocks of the fibers. In fact, the single proteins feel a strong mutual repulsion preventing them to pack and the ribbon structure is the only one that permits to limit this repulsion. Presently one missing information in the present model, is the exact nature of the short range attraction between the building blocks that drives in the first place the assembly among the protein filaments. Scientists agree that along the filaments there are charge-less domains of hydrophobic character (water repellent) that are the source of the short-range attraction. So there is a balance between attractive and repulsive interactions and the results is the ribbon like twisted conformation.
Self-organizing proteins are common in living matter and they are found in large aggregates for example in blood coagulation. Spherical like proteins are used in food industry as emulsifiers, gelling and foaming agents and in vitro they form amyloid like structures. These latter fibers have properties (elasticity, solubility, etc) favorable for food texturing or to produce special structures. The milk protein beta-lactoglubulin studied by Mezzenga and his colleagues is at the beginning spherical and by a heat treatment accompanied by acid environment it aggregates into the filamentous structures. Beta-lactoglobulin is an important component of the milk serum and therefore very relevant for food industry.
The knowledge gained by the scientists on this food protein can potentially benefit medical sciences. In fact amyloid-like fibers appear in humans affected by neurodegenerative diseases, like Alzheimer- or Creutzfeldt-Jakob disease. These human fibers, although made out of a very different proteins, are also ribbon-like and twisted and their assembly into long aggregates is presently under intense scrutiny. The model proposed by the team could also help to understand the genesis and development of theses diseases.
Journal Reference:
Adamcik J, Jung J-M, Flakowski J, De Los Rios P, Dietler G, Mezzenga R. Understanding amyloid aggregation by statistical analysis of atomic force microscopy images. Nature Nanotechnology, 2010; DOI: 10.1038/nnano.2010.59
(http://www.sciencedaily.com/releases/2010/04/100411143351.htm)
ScienceDaily (Apr. 11, 2010) — Researchers have detailed a basic general mechanism describing how filamentous proteins assemble into ribbon like structures, the so-called amyloid fibrils. Combining experiments and theory, they can explain how denatured milk proteins assemble into ribbon like structures composed of up to five filaments. These findings are shining a surprisingly new light on the assembly of these proteins.
The atomic force microscope depicts on its screen the few nanometer thick and few micrometer long fibers as white flexible sticks, crisscrossing the surface on which they are deposited. The very peculiar property of these proteins lies in fact that they can self assemble into complex ribbon-like twisted fibers.
Researchers at ETH Zürich, EPF Lausanne and University of Fribourg have teamed up to take atomic force microscopy images of the fibers and to analyze them using concepts from polymer physics and theoretical modeling. This combination of expertise has lead them to propose a set of general rules governing the assembly of filaments into thicker and twisted ribbon like fibers. Their results are published in the current issue of the scientific journal Nature Nanotechnology. "The model that we propose is extremely precise in its predictions," says Raffaele Mezzenga, Professor of Food and Soft Materials Sciences at the ETH Zürich. "Up to now there was no such exact and general model for the formation of amyloid fibers," continues Giovanni Dietler, Professor of Physics of Living Matter, at the EPF Lausanne.
The structure of the amyloid fibers as it was unveiled by the experiments, surprised the researchers. Single proteins build the long filaments and subsequently the filaments assemble side by side to form the ribbon-like twisted fibers.
Mezzenga explains that the ribbon-like structure is the logic consequence of the strong charge carried by the building blocks of the fibers. In fact, the single proteins feel a strong mutual repulsion preventing them to pack and the ribbon structure is the only one that permits to limit this repulsion. Presently one missing information in the present model, is the exact nature of the short range attraction between the building blocks that drives in the first place the assembly among the protein filaments. Scientists agree that along the filaments there are charge-less domains of hydrophobic character (water repellent) that are the source of the short-range attraction. So there is a balance between attractive and repulsive interactions and the results is the ribbon like twisted conformation.
Self-organizing proteins are common in living matter and they are found in large aggregates for example in blood coagulation. Spherical like proteins are used in food industry as emulsifiers, gelling and foaming agents and in vitro they form amyloid like structures. These latter fibers have properties (elasticity, solubility, etc) favorable for food texturing or to produce special structures. The milk protein beta-lactoglubulin studied by Mezzenga and his colleagues is at the beginning spherical and by a heat treatment accompanied by acid environment it aggregates into the filamentous structures. Beta-lactoglobulin is an important component of the milk serum and therefore very relevant for food industry.
The knowledge gained by the scientists on this food protein can potentially benefit medical sciences. In fact amyloid-like fibers appear in humans affected by neurodegenerative diseases, like Alzheimer- or Creutzfeldt-Jakob disease. These human fibers, although made out of a very different proteins, are also ribbon-like and twisted and their assembly into long aggregates is presently under intense scrutiny. The model proposed by the team could also help to understand the genesis and development of theses diseases.
Journal Reference:
Adamcik J, Jung J-M, Flakowski J, De Los Rios P, Dietler G, Mezzenga R. Understanding amyloid aggregation by statistical analysis of atomic force microscopy images. Nature Nanotechnology, 2010; DOI: 10.1038/nnano.2010.59
(http://www.sciencedaily.com/releases/2010/04/100411143351.htm)
Your Fat May Help You Heal: Researcher Extracts Natural Scaffold for Tissue Growth
Site of the day: http://forums.digitalpoint.com/
ScienceDaily (Mar. 26, 2010) — It frequently happens in science that what you throw away turns out to be most valuable. It happened to Deepak Nagrath, but not for long.
The Rice assistant professor in chemical and biomolecular engineering was looking for ways to grow cells in a scaffold, and he discarded the sticky substance secreted by the cells.
"I thought it was contamination, so I threw the plates away," said Nagrath, then a research associate at Harvard Medical School.
That substance, derived from adipose cells -- aka body fat -- turned out to be a natural extracellular matrix, the very thing he was looking for.
Nagrath, who joined Rice in 2009, and his co-authors have since built a biological scaffold that allows cells to grow and mature. He hopes the new material, when suffused with stem cells, will someday be injected into the human body, where it can repair tissues of many types without fear of rejection.
The research by Nagrath and his co-authors appeared last week in the Federation of American Societies for Experimental Biology (FASEB) Journal.
The basic idea is simple: Prompt fat cells to secrete what bioengineers call "basement membrane." This membrane mimics the architecture tissues naturally use in cell growth, literally a framework to which cells attach while they form a network. When the cells have matured into the desired tissue, they secrete another substance that breaks down and destroys the scaffold.
Structures that support the growth of living cells into tissues are highly valuable to pharmaceutical companies for testing drugs in vitro. Companies commonly use Matrigel, a protein mixture secreted by mouse cancer cells, but for that reason it can't be injected into patients.
"Fat is one thing that is in excess in the body. We can always lose it," Nagrath said. The substance derived from the secretions, called Adipogel, has proven effective for growing hepatocytes, the primary liver cells often used for pharmaceutical testing.
"My approach is to force the cells to secrete a natural matrix," he said. That matrix is a honey-like gel that retains the natural growth factors, cytokines (substances that carry signals between cells) and hormones in the original tissue.
Nagrath's strategy for growing cells isn't the only approach being pursued, even at Rice: Another method reported last week in Nature Nanotechnology uses magnetic levitation to grow three-dimensional cell cultures.
But Nagrath is convinced his strategy is ultimately the most practical for rebuilding tissue in vivo, and not only because it may cost significantly less than Matrigel. "The short-term goal is to use this as a feeder layer for human embryonic stem cells. It's very hard to maintain them in the pluripotent state, where they keep dividing and are self-renewing," he said.
Once that goal is achieved, Adipogel may be just the ticket for transplanting cells to repair organs. "You can use this matrix as an adipogenic scaffold for stem cells and transplant it into the body where an organ is damaged. Then, we hope, these cells and the Adipogel can take over and improve their functionality."
Nagrath's co-authors are Nripen S. Sharma, a research associate at Rutgers University, and Martin Yarmush, the Helen Andrus Benedict Professor of Surgery and Bioengineering at Harvard Medical School.
The National Institutes of Health and the Shriners Hospitals for Children supported their research.
Journal Reference:
Sharma et al. Adipocyte-derived basement membrane extract with biological activity: applications in hepatocyte functional augmentation in vitro. The FASEB Journal, 2010;
DOI: 10.1096/fj.09-135095
(http://www.sciencedaily.com/releases/2010/03/100325143059.htm)
ScienceDaily (Mar. 26, 2010) — It frequently happens in science that what you throw away turns out to be most valuable. It happened to Deepak Nagrath, but not for long.
The Rice assistant professor in chemical and biomolecular engineering was looking for ways to grow cells in a scaffold, and he discarded the sticky substance secreted by the cells.
"I thought it was contamination, so I threw the plates away," said Nagrath, then a research associate at Harvard Medical School.
That substance, derived from adipose cells -- aka body fat -- turned out to be a natural extracellular matrix, the very thing he was looking for.
Nagrath, who joined Rice in 2009, and his co-authors have since built a biological scaffold that allows cells to grow and mature. He hopes the new material, when suffused with stem cells, will someday be injected into the human body, where it can repair tissues of many types without fear of rejection.
The research by Nagrath and his co-authors appeared last week in the Federation of American Societies for Experimental Biology (FASEB) Journal.
The basic idea is simple: Prompt fat cells to secrete what bioengineers call "basement membrane." This membrane mimics the architecture tissues naturally use in cell growth, literally a framework to which cells attach while they form a network. When the cells have matured into the desired tissue, they secrete another substance that breaks down and destroys the scaffold.
Structures that support the growth of living cells into tissues are highly valuable to pharmaceutical companies for testing drugs in vitro. Companies commonly use Matrigel, a protein mixture secreted by mouse cancer cells, but for that reason it can't be injected into patients.
"Fat is one thing that is in excess in the body. We can always lose it," Nagrath said. The substance derived from the secretions, called Adipogel, has proven effective for growing hepatocytes, the primary liver cells often used for pharmaceutical testing.
"My approach is to force the cells to secrete a natural matrix," he said. That matrix is a honey-like gel that retains the natural growth factors, cytokines (substances that carry signals between cells) and hormones in the original tissue.
Nagrath's strategy for growing cells isn't the only approach being pursued, even at Rice: Another method reported last week in Nature Nanotechnology uses magnetic levitation to grow three-dimensional cell cultures.
But Nagrath is convinced his strategy is ultimately the most practical for rebuilding tissue in vivo, and not only because it may cost significantly less than Matrigel. "The short-term goal is to use this as a feeder layer for human embryonic stem cells. It's very hard to maintain them in the pluripotent state, where they keep dividing and are self-renewing," he said.
Once that goal is achieved, Adipogel may be just the ticket for transplanting cells to repair organs. "You can use this matrix as an adipogenic scaffold for stem cells and transplant it into the body where an organ is damaged. Then, we hope, these cells and the Adipogel can take over and improve their functionality."
Nagrath's co-authors are Nripen S. Sharma, a research associate at Rutgers University, and Martin Yarmush, the Helen Andrus Benedict Professor of Surgery and Bioengineering at Harvard Medical School.
The National Institutes of Health and the Shriners Hospitals for Children supported their research.
Journal Reference:
Sharma et al. Adipocyte-derived basement membrane extract with biological activity: applications in hepatocyte functional augmentation in vitro. The FASEB Journal, 2010;
DOI: 10.1096/fj.09-135095
(http://www.sciencedaily.com/releases/2010/03/100325143059.htm)
Subscribe to:
Posts (Atom)