One hundred and ninety-two atoms have tied the knot.

Chains of carbon, hydrogen, oxygen and nitrogen atoms, woven together in a triple braid, form the most complex molecular knot ever described, chemists from the University of Manchester in England report in the Jan. 13 Science.

Learning how to tie such knots could one day help researchers weave molecular fabrics with all sorts of snazzy properties. “We might get the strength of Kevlar with a lighter and more flexible material,” says study coauthor David Leigh.
That’s still a long way away, but molecular knot tying has an appeal that’s purely intellectual, too, says University of Cambridge chemist Jeremy Sanders. “It’s like the answer to why you climb Everest,” he says. “It’s a challenge.”

Mathematicians know of more than six billion types of prime knots, which, like prime numbers, cannot be broken down into simpler components. “Prime knots can’t be built up by sticking other knots together,” Leigh explains. For years, chemists were able to synthesize just one type of prime knot out of small molecules. “We thought that was pretty ridiculous,” says Leigh.

That molecular knot was a trefoil, like a three-leaf clover. Jean-Pierre Sauvage and colleagues wove it from chemical strands in 1989. Sauvage won a Nobel Prize in 2016 for earlier work that used the same principles explored in his knots (SN: 10/29/16, p. 6).

In the decades since Sauvage’s trefoil, chemists have tried to synthesize other types of molecular knots, but “they’ve always found it incredibly difficult,” says chemist Sophie Jackson, also at the University of Cambridge.

Persuading nanoscale strands to interlock together in an orderly fashion isn’t simple. “You can’t just grab the ends and tie them like you would a shoelace,” Leigh says. Instead, scientists choose molecular ingredients that assemble themselves.
In 2012, Leigh and colleagues used the self-assembly technique to make a molecular pentafoil knot, a star-shaped structure made up of 160 atoms and with strands that cross five times (SN: 1/28/12, p. 12). This latest knot, with eight crossing points, is even more intricate.

Leigh’s team mixed together building blocks containing carbon, hydrogen, oxygen and nitrogen atoms with iron ions and chloride ions. “You dump them all in, heat them all up and they self-assemble,” he says. Sticky metal ions hold the building blocks in the correct position, and a single chloride ion sitting in the middle of the structure anchors it all together. Then, a chemical catalyst links the building blocks, forming the completed knot. The new knot is the tightest ever created, Leigh says, with just 24 atoms between each crossing point.

It’s beautiful, Sanders says. “It’s a string of atoms rolled up in a spherical shape, with an astonishing amount of symmetry.” Sanders is reluctant to speculate how such a knot might be used, but it’s round and very dense, he says. That could give it some interesting materials properties.

Leigh suspects that different molecular knots might behave differently, like the various knots used by fishermen and sailors. “We want to make specific knots, see what they do and then figure out how to best exploit that,” he says.

A big coconut crab snaps its outsized left claw as hard as a lion can bite, new measurements suggest. So what does a land crab the size of a small house cat do with all that pinch power?

For starters, it protests having its claw-force measured, says Shin-ichiro Oka of the Okinawa Churashima Foundation in Motobu, Japan. “The coconut crab is very shy,” he says. It doesn’t attack people unprovoked. But wrangling 29 wild Birgus latro crabs on Okinawa and getting them to grip a measurement probe inspired much snapping at scientists. Oka’s hand got pinched twice (no broken bones). “Although it was just a few minutes,” he says, “I felt eternal hell.”
The strongest claw grip the researchers measured squeezed with a force of about 1,765 newtons, worse than crushing a toe under the force of the full weight of a fridge. For comparison, a lion’s canines bite with 1,315 newtons and some of its molars can crunch with 2,024 newtons, a 2007 study calculated. Because grip strength increases with body size, crabs bigger than those measured in the study might surpass the bite force of most land predators, Oka and colleagues proposed last year in PLOS ONE.
Coconut crabs, however, start life about as scary as a soggy grain of rice. Fertilized eggs hatch in seawater and bob around planktonlike in the western Pacific and Indian oceans. The crabs eventually return to land, where they spend most of their long lives, up to 50 (or maybe 100) years, as landlubbers that will drown if forced back into water for too long. Yet females have to risk the ocean’s edge each time they lay the next generation of eggs.
Both moms and dads grow a powerful left claw, handy for dismembering whatever the omnivorous scavengers find: roadkill and other dead stuff, innards of palm trees and nuts. The crabs can break open coconuts, but the job “takes hours,” says Jakob Krieger of the University of Greifswald in Germany. Cracking open a red crab, however, takes seconds.

Coconut crabs not only scavenge red crabs but also hunt them on Christmas Island in the Indian Ocean, Krieger says. Only the strictest vegetarian would ignore the 44 million or so red crabs scuttling around, and even small coconut crabs get a taste. Krieger watched an underpowered coconut crab grab hold of and wrestle its prey. The red crab abandoned its trapped limb and fled. But the little coconut crab scored a crab-leg dinner.

A record-breaking quantum satellite has again blown away the competition, achieving two new milestones in long-distance quantum communications through space.

In June, Chinese researchers demonstrated that the satellite Micius could send entangled quantum particles to far-flung locations on Earth, their properties remaining intertwined despite being separated by more than 1,200 kilometers (SN Online: 6/15/17). Now researchers have used the satellite to teleport particles’ properties and transmit quantum encryption keys. The result, reported in two papers published online July 3 and July 4 at arXiv.org, marks the first time the two techniques have been demonstrated in space.
In quantum teleportation, the properties of one particle are transferred to another. The scientists first sent particles of light, or photons, from the ground to the satellite — a distance of up to 1,400 kilometers. When the researchers made particular measurements of other photons on the ground, the spacefaring particles took on the properties of the landlubbers, thanks to quantum entanglement between the earthbound and satellite-based particles. Although it’s a far cry from the Star Trek variety of teleportation, the process is an important ingredient of quantum communication.

Quantum key distribution is a method of creating a secret string of random numbers that can be used to encrypt communications. The researchers beamed photons from the satellite to Earth over distances of up to 1,200 kilometers, using the photons’ polarization, the orientation of their electromagnetic waves, to transmit a string of random numbers with utmost security.

Quantum communication via satellite can reach greater distances than land-based transmission, because in space, particles don’t get absorbed by the atmosphere. The new results pave the way for a global quantum internet that would provide for ultrasecure communications and allow quantum computers to work together.

Scientists have created the largest map of dark matter yet, part of a slew of new measurements that help pin down the universe’s dark contents. Covering about a thirtieth of the sky, the map (above) charts the density of both normal matter — the stuff that’s visible — and dark matter, an unidentified but far more abundant substance that pervades the cosmos.

Matter of both types is gravitationally attracted to other matter. That coupling organizes the universe into more empty regions of space (No. 1 below and blue in the map above) surrounded by dense cosmic neighborhoods (No. 2 below and red in the map above).
Researchers from the Dark Energy Survey used the Victor Blanco telescope in Chile to survey 26 million galaxies in a section of the southern sky for subtle distortions caused by the gravitational heft of both dark and normal matter. Scientists unveiled the new results August 3 at Fermilab in Batavia, Ill., during a meeting of the American Physical Society.

Dark matter is also accompanied by a stealthy companion, dark energy, an unseen force that is driving the universe to expand at an increasing clip. According to the new inventory, the universe is about 21 percent dark matter and 5 percent ordinary matter. The remainder, 74 percent, is dark energy.

The new measurements differ slightly from previous estimates based on the cosmic microwave background, light that dates back to 380,000 years after the Big Bang (SN: 3/21/15, p. 7). But the figures are consistent when measurement errors are taken into account, the researchers say.
“The fact that it’s really close, we think is pretty remarkable,” says cosmologist Josh Frieman of Fermilab, who directs the Dark Energy Survey. But if the estimates don’t continue to align as the survey collects more data, something might be missing in cosmologists’ theories of the universe.

A vaccine to fight Lyme disease, decades in the making, has received a temporary green light from the U.S. Department of Agriculture. But it’s not for people — it’s for mice.

The vaccine isn’t a rodent-sized injection, which wouldn’t work for targeting large populations quickly. Instead, it’s coated onto edible, nutrition-free pellets that mice gobble up.

The vaccine makes mice develop antibodies that neutralize Borrelia burgdorferi, the bacterium that causes most U.S. cases of Lyme disease. When ticks imbibe the blood of a vaccinated mouse, the idea goes, they won’t get an active infection and so can’t transmit the bacteria to people or other animals.
“Mice are probably one of the most important reservoir hosts for Lyme disease,” especially in the Eastern United States where Lyme disease is rampant, says Jean Tsao, a disease ecologist at Michigan State University in East Lansing who was not involved in developing the new vaccine. Reservoir hosts are animals with B. burgdorferi in their blood (SN: 2/5/21).

The vaccine has a conditional license, granted on May 9. That means it is available on request by groups such as federal and state health agencies under certain conditions for roughly one year, with the possibility of renewal.

The first well-documented case of Lyme disease in a person in the United States was in 1970. A vaccine for humans was available from 1998 to 2002, but it was taken off the market due to low consumer demand, likely related to fears over the vaccine’s safety. Some vaccinated people reported developing arthritis, but the U.S. Food and Drug Administration found no meaningful difference in joint problems in vaccinated versus control groups.

Both the mouse and human vaccines use a protein called OspA, found on the surface of B. burgdorferi, to spur antibody production and prevent infection.

Biologist Maria Gomes-Solecki co-led the early development of the new mouse vaccine. Her team distributed an early version of the vaccine to areas in upstate New York from 2007 to 2011. B. burgdorferi has a two-year life cycle in ticks. This and other factors mean it takes time to see meaningful reductions in infections, says Gomes-Solecki, of the University of Tennessee Health Science Center in Memphis. After two and five years of vaccination, the researchers found that tick infections were reduced by 23 and 76 percent, respectively, compared with control sites.

That early vaccine used live Escherichia coli bacteria to deliver the OspA protein. But the current, green-lighted version of the vaccine uses inactive E. coli. A 2020 study of the new vaccine found a 30 percent reduction in the proportion of infected ticks in residential areas after two years, compared with control sites. Several coauthors on that study work for US Biologic, the company Gomes-Solecki cofounded to develop the vaccine.
“The vaccine they have works, but it’s not spectacular” in terms of the rate of reducing B. burgdorferi–infected ticks, says Sam Telford III, an epidemiologist at Tufts University in Medford, Mass., who was involved in the development of the human vaccine and led research in the 1990s for vaccinating mice.

Edible vaccines targeted at hosts have worked well for other diseases and species. For instance, vaccinating prairie dogs against the plague has decreased levels of the disease. For now, it remains to be seen whether vaccinating mice will result in lower Lyme risks for humans. “With additional studies as the product rolls out … we’ll see more data on how well it does,” Telford says. “It’s certainly a step in the right direction.”

Researchers are studying many approaches to controlling Lyme disease, including genetically engineered mice that produce B. burgdorferi antibodies without the need for vaccination (SN: 8/9/17). Tsao and Telford are studying how to limit tick populations by controlling deer numbers. And a new vaccine for humans is in late-phase testing in several thousand people.

Vaccines that target wildlife hosts will remain one tool among many for managing exposure to Lyme disease, the researchers say. Showering after being in areas with ticks, wearing long sleeves and pants and doing tick checks will still be important.

“We have to continue to be vigilant,” Gomes-Solecki says.