The Week That Was:

When Engineers Tied The Tiniest Knot:

Scientists at the University of Manchester have tied the tightest knot ever. They say that the achievement could lead to a new generation of supermaterials. “Some polymers, such as spider silk, can be twice as strong as steel so braiding polymer strands may lead to new generations of light, super-strong and flexible materials for fabrication and construction,” according David Leigh, a professor at Manchester’s School of Chemistry. The knot has eight crossings on a loop made from 192 atoms and just 20 nanometers long.

“Tying knots is a similar process to weaving, so the techniques being developed to tie knots in molecules should also be applicable to the weaving of molecular strands,” Leigh said. “For example, bulletproof vests and body armor are made of Kevlar, a plastic that consists of rigid molecular rods aligned in a parallel structure — however, interweaving polymer strands have the potential to create much tougher, lighter and more flexible materials in the same way that weaving threads does in our everyday world.”

Meanwhile, Bioengineers at Duke University have tweaked the DNA of a salmonella bacteria strain that typically causes food poisoning and then used the modified bugs to attack glioblastoma, the deadliest form of brain cancer. The team engineered the bacteria to penetrate the protective blood-brain barrier and turned the bacteria “into a cancer-seeking missile that produces self-destruct orders deep within tumors.”

That’s because the genetic changes compelled the microbes to produce a pair of compounds called Azurin and p53 that tell cells to commit suicide. Duke reported that tests in rats with “extreme cases of the disease” extended the lives of 20 percent of the population by 100 days — roughly equivalent to 10 human years — and sent their tumors into complete remission. “A major challenge in treating gliomas is that the tumor is dispersed with no clear edge, making them difficult to completely surgically remove,” said Ravi Bellamkonda, dean of Duke’s Pratt School of Engineering and corresponding author of the paper.

“So designing bacteria to actively move and seek out these distributed tumors, and express their anti-tumor proteins only in hypoxic, purine-rich tumor regions is exciting.”