Science Square

  • Issue 86 / March - April 2012

    Impressive Design and Strength of Spider Silk's Web

    The Fountain

    1- Impressive Design and Strength of Spider Silk's Web
    Original Article: Cranford, S.W. et al., Nature 482, 72 (2012).
    Spider silk has been a symbol of durability and strength, but the role the design of a web plays or contributes to the strength was unknown. Researchers from Massachusetts Institute of Technology discovered that the impressive design of web and the feature of silk allow spiders to build a super-strong web under different levels of stress. The response of spider silk subjected to load was studied. They studied webs of a variety of species, including European garden spiders and orb weavers, and combined their experiments with correlated web models. At low stress, silk threads soften and extend that result in retaining web structure. At high stress, the silk threads extend and the most stretched ones break. The strength of the silk and the geometry of the web allow only one or two threads being broken under strain. Therefore, the break in the web is minimized and prevents destruction of the whole web. The localized web damage can be repaired by the spider and therefore a requirement for rebuilding the web completely is eliminated. This study shows that spider silk web is very stable even under hurricane winds. This research gives an idea to engineers to build a system that will fail only at small parts of the system under certain stress. Therefore, the system will continue to work just after repairing the destroyed parts of the system. Otherwise, the whole system may be destroyed under potential load and will have to be rebuilt. For example, when a building is exposed to large mechanical stress such as an earthquake, it may be destroyed as a whole and become dysfunctional. Applications on such systems require further research in engineering to achieve structures as stable as a spider's web.

    2- Benefits of Exercise Through a Protein
    Original article: Bostrom, P. et al., Nature 481, 463 (2012).
    Exercise has a number of beneficial effects in human health such as increasing cardiovascular, respiratory and metabolic capacity. Scientists at Harvard Medical School have discovered a muscle hormone, Irisin, which may be responsible for the many beneficial effects of exercise. Irisin secreted from muscle after exercise and act on white adipose tissue that stores energy. Excessive amounts of white fat cells contribute to many pathologic effects of obesity and diabetes. Irisin, however, converts white fat into the more beneficial and metabolically active brown fat, which burns more calories and produce heat instead of energy. It helps to prevent excessive glucose and fatty acid accumulation in the body. The researchers demonstrated that mildly increased Irisin levels in the blood cause an increase in energy expenditure in mice with no changes in movement or food intake. It also reduces body weight and improves glucose tolerance and obesity induced insulin resistance. This research suggests that Irisin can be a new therapeutic target in human metabolic diseases treatment. Also it could help people lose weight and fight against obesity induced problems such as diabetes and hypertension.

    3- New Generation Vaccines with High Efficacy
    Original Article: Avci F.Y. et al., Nature Medicine 17, 1602 (December 2011).
    Most pathogenic bacteria contain complex carbohydrate structures on their surfaces. These carbohydrates are called capsular polysaccharides. “Glycoconjugate” vaccines are prepared by chemical conjugation of capsular polysaccharides with proteins. This method is the standard design for many vaccines that protect us against common diseases such as pneumonia and meningitis. One drawback with these vaccines is their limited efficacy in populations such as the elderly, children and patients with compromised immune systems. Researchers at Harvard Medical School and Rockefeller University have designed and synthesized a vaccine that is about 100 times more potent than traditional vaccines available today. Until now, the scientific community believed that the body's professional immune cells, called T-cells, were only able to recognize vaccine's protein molecules to generate an immune response. However, after studying how glycoconjugate vaccines stimulate immune response, the researchers found that T-cells are also able to recognize the carbohydrate molecules. In a series of elegant experiments, they demonstrated that there is a repertoire of T-cells that can recognize the carbohydrate portion of a glycoconjugate vaccine, and that these T-cells stimulate antibody producing B-cells to generate high affinity antibodies against the carbohydrates. Based on the knowledge obtained from this mechanistic study, researchers have designed a new-generation glycoconjugate vaccine and showed that this new vaccine was about 100 times more immunogenic than a vaccine made by traditional methods.

    4- Producing Fuel from Waste with Bacteria
    Original Article: Bokinsky, G. et al., PNAS 108, 19949 (December 2011).
    It turns out, the secret for alternative source for oil might be hidden in a very common bacterium and plant, E coli and switch grass. As the world's natural resources are quickly exhausted by humans, new energy sources or alternative energy production methods are needed. One popular way for addressing this question is promoting biofuels. Most of the biofuel source is in ethanol form, often produced from sugar that is extracted from sugarcane and corn. However the consuming of main food sources for energy sources begs a question: What if one day feeding the machines with our food sources makes food scarce? Another concern is that many countries are not using ethanol as an energy source. All these led researchers to pursue another idea: Instead of using food sources as precursor for ethanol, non-food biomass or bio-waste can be converted to precursors for biofuels by utilizing the cellulose or hemicellulose as a starting material. Human body cannot digest cellulose. Hence, cellulose is a bio-waste, which can be broken down into sugar using a mixture of enzymes and subsequently can be used for gasoline production. The enzymes for this procedure can be produced by bacteria in massive amounts. To this end, researchers genetically engineered Ecoli bacteria to consume large amount of cellulose from switch grass and convert it to sugar. Scientists achieved to produce different precursors for different fuels, including gasoline, diesel or jet fuel with bacteria. These are big steps in turning bio-waste into fuels. Imagine one day your plane will be powered with a hay of switch grass and a bottle of bacteria. Next time when you fly over a field of switch grass, you might actually be seeing the next oil well.


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