A rule of chemistry suppressed — promising new ways to look into cells, make LEDs
Glow-in-the-dark stickers, weird deep-sea fish, LED lightbulbs — all have forms of luminescence. In other words, instead of just reflecting light, they make their own.
Now a team of scientists from the University of Vermont and Dartmouth College have discovered a new way that some molecules can make a luminescent glow — a strange, bright green.
“It’s a new method to create light,” says Matthew Liptak, achemist at UVM who co-led the new research. The new light may have many promising applications including novel kinds of LED bulbs and medical dyes “that can sense viscosity within a cell,” he says.
The discovery was reported Sept. 26 in the journal Nature Chemistry.
To understand how this new light is formed, consider maple syrup. It’s a thick liquid. The scientists at Dartmouth, led by chemist Ivan Aprahamian, were exploring some strange molecules, called molecular rotors, shaped like kayak paddles where both blades rotate around a shaft. (Yes, a very small shaft, many thousands of times thinner than a hair). In a thin liquid, like water, clumps of these rotating molecules — a kind of dye containing boron — give off a weak, reddish luminescent glow.
But when the scientists put the molecules into thicker and thicker maple-syrup-like solvents — in this case, mixtures of glycerol and ethylene glycol — the fluorescent light from these molecular rotors didn’t get weaker as expected. Instead, they glow brightly, in a vivid green color nearer the blue end of the spectrum.
“That was very surprising,” says Liptak, an expert on computational chemistry. So the Dartmouth team turned to him and his students to explain why. As the UVM team investigated, making simulations on the Vermont Advanced Computing Core— and both teams further investigated the molecules using spectroscopy and other lab techniques — they came to an even-more-surprising discovery: the way this light was being emitted required breaking a long-standing law of chemistry called Kasha’s Rule.
“We found a new way that the universe works that we didn’t understand before,” Liptak says. “It’s an exception to the rule.”
The world has color because molecules absorb and give off light according to the “spooky” rules of quantum mechanics. In most cases, a molecule will absorb a specific wavelength of light and we will see its complement on the color wheel. In some cases, molecules “glow in the dark” by emitting a specific color of light a short time after absorbing light. This is luminescence.
In 1950, the famed chemist Michael Kasha observed that a luminescent molecule generally emits the same color light regardless of the color of light that it initially absorbed. This is because the first step following absorption of light is a molecular relaxation — a rapid vibration, stretching and release of heat — to get the molecule to its “lowest energy excited state,” Liptak explains. So when a typical luminescent molecule absorbs higher energy light, towards the blue end of the spectrum, it simply produces more heat, not brighter or different-colored luminescence. “This is Kasha’s rule,” Liptak says.
But the UVM/Dartmouth team, with support from the National Science Foundation, found that when their special rotor molecules are in a thick solution, their capacity to vibrate is limited and so they emit light before they are done vibrating. This is because the paddle-shaped part of the rotor must rotate freely in order to turn on the chemical pathway that allows it to give off heat energy — but this rotation is suppressed in a thick solution. The thicker the solution, the less the molecular paddles rotate, the more light can be emitted. Which is why the team is calling their discovery Suppression of Kasha’s Rule, or SOKR (pronounced “soccer”) for short.
“One way to understand SOKR is to think about a water slide with two outlets where one outlet is located far above the pool and the other is located at the level of the pool,” explains Liptak. “In low viscosity solutions like water, the paddles rush all the way to the bottom outlet and enter the pool without a splash. In high viscosity solutions like maple syrup, the paddles are slowed down, allowing some to spill out the top outlet creating a waterfall or, in the case of light-emitting molecular rotors, bright green light.”
This new pathway to creating light may prove useful. “The compound we found is very bright, and due to its viscosity sensitivity, may have a multitude of applications,” says Morgan Cousins, a UVM doctoral student and co-author on the new study. “We see uses for these kinds of molecules from industrial materials to new kinds of LEDs to biomedical imaging.”
Consider cells. The many parts within a cell — from the endoplasmic reticulum to mitochondria — have different functions, and, presumably, have different viscosities too. But not much is known about this — which is where these fluorescent rotor molecules might help. The newly discovered molecules are not safe for use in a human, but the team is currently hunting for similar “bio-compatible” compounds, Liptak says, that could be incorporated into a medical dye or other test where they would glow brightly in more-viscous parts of a cell and less in more-watery parts. The molecules could be applied as a sensitive diagnostic tool because they precisely change the amount of light they emit based on the thickness of the solution they are in.
“Viscosity is a fundamental property of biological systems that we’re currently mostly blind to,” Liptak says. But this new discovery may shine new light.
Learn more: Discovery: A New Form of Light
New analog compiler could help enable simulation of whole organs and even organisms.
A transistor, conceived of in digital terms, has two states: on and off, which can represent the 1s and 0s of binary arithmetic.
But in analog terms, the transistor has an infinite number of states, which could, in principle, represent an infinite range of mathematical values. Digital computing, for all its advantages, leaves most of transistors’ informational capacity on the table.
In recent years, analog computers have proven to be much more efficient at simulating biological systems than digital computers. But existing analog computers have to be programmed by hand, a complex process that would be prohibitively time consuming for large-scale simulations.
Last week, at the Association for Computing Machinery’s conference on Programming Language Design and Implementation, researchers at MIT’s Computer Science and Artificial Intelligence Laboratory and Dartmouth College presented a new compiler for analog computers, a program that translates between high-level instructions written in a language intelligible to humans and the low-level specifications of circuit connections in an analog computer.
The work could help pave the way to highly efficient, highly accurate analog simulations of entire organs, if not organisms.
Using the power of the light around us, Dartmouth College researchers have significantly improved their innovative light-sensing system that tracks a person’s behavior continuously and unobtrusively in real time.
The new StarLight system has a wide range of practical applications, including virtual reality without on-body controllers and non-invasive real-time health monitoring. The new system advances the researchers’ prior LiSense design by dramatically reducing the number of intrusive sensors, overcoming furniture blockage and supporting user mobility.
The results will be presented June 27 at the ACM MobiSys 2016, the 14th ACM International Conference on Mobile Systems, Applications, and Services. A PDF is available on request.
The researchers studied the use of purely ubiquitous light around us to track users’ behavior, without any cameras, on-body devices or electromagnetic interference. They were able to reconstruct a user 3D skeleton by leveraging the light emitted from LED panels on the ceiling and only 20 light sensors on the floor. The system can track the user’s skeleton as he or she moves around in a room with furniture and other objects.
Dartmouth College, commonly referred to as Dartmouth (/ˈdɑrtməθ/ dart-məth), is a private Ivy League research university located in Hanover, New Hampshire, United States.
The institution consists of a liberal arts college, the Geisel School of Medicine, the Thayer School of Engineering, and the Tuck School of Business, as well as 19 graduate programs in the arts and sciences. Incorporated as the “Trustees of Dartmouth College,” it is one of the nine Colonial Colleges founded before the American Revolution. With an undergraduate enrollment of 4,194 and a total student enrollment of 6,144, Dartmouth is the smallest university in the Ivy League.
Dartmouth College was established in 1769 by Eleazar Wheelock, a Congregational minister. After a long period of financial and political struggles, Dartmouth emerged in the early 20th century from relative obscurity. Dartmouth alumni, from Daniel Webster to the many donors in the 19th and 20th centuries, have been famously involved in their college.
Dartmouth is located on a rural 269 acres (1.09 km2) campus in the Upper Valley region of New Hampshire. The campus is isolated, and participation in athletics and the school’s Greek system is strong. Dartmouth’s 34 varsity sports teams compete in the Ivy League conference of the NCAA Division I. Students are well known for preserving a variety of strong campus traditions.
The Latest Updated Research News:
Dartmouth College research articles from Innovation Toronto
- Dartmouth Team Uses Smart Light to Track Human Behavior Continuously in Real Time – June 16, 2016
- Breakthrough towards sustainable, fish-free feeds for aquaculture – June 5, 2016
- Digital media may be changing how we think at the expense of abstract thought? – May 13, 2016
- Scientists invent robotic ‘artist’ that spray paints giant murals – April 8, 2016
- Simple shell of plant virus sparks immune response against cancer – December 23, 2015
- Smart light lets you control your environment – August 20, 2015
- Dartmouth team creates first hidden, real-time, screen-camera communication – May 19, 2015
- Researchers create first image-recognition software that greatly improves web searches – November 23, 2014
- Scientists test a Nanoparticle “Alarm Clock” to Awaken Immune Systems Put to Sleep by Cancer – July 27, 2014
- Does Cat Poop Parasite Play a Role in Curing Cancer – July 16, 2014?
- URI researchers release new biological agent to fight invasive weed
- NASA Rover Prototype Set To Explore Greenland Ice Sheet
- Shadows and light: Dartmouth researchers develop new software to detect forged photos
- Microwave imaging can see how well Breast Cancer treatment is progressing
- Diss Information: Is There a Way to Stop Popular Falsehoods from Morphing into “Facts”?
Dartmouth College scientists have discovered that marine microalgae can completely replace the wild fish oil currently used to feed tilapia, the second most farmed fish in the world and the most widely farmed in the United States.
The findings, which appear in the open-access journal PLOS ONE, are a major breakthrough in the quest to develop sustainable, fish-free feeds for aquaculture, the world’s fastest growing food sector. The Dartmouth study is the first report of a marine microalgae species being successfully used as a complete replacement of fish oil in feed for Nile tilapia, which thrived on the new diet and bulked up despite eating less.
Aquaculture currently uses more than 80 percent of the world’s fish oil and fishmeal, which are extracted from small ocean-caught fish, leading to over-fishing of these species. Pallab Sarker, the new study’s lead author, previously found that salmon aquaculture consumes more wild fish — in the form of protein and oil from open-ocean fishes like mackerel, herring, anchovies and menhaden — than it produces in the form of edible meat from farmed fish, resulting in a net removal of fish on a global basis.
Scientists have reported success in partially or totally replacing fish oil with vegetable oil in many farmed-fish species, but studies show that vegetable oil reduces the nutritional quality of the fish flesh. In contrast to vegetable oil, microalgae are much higher in essential omega-3 fatty acids, which are important for maintaining fish health and imparting neurological, cardiovascular and anti-cancer benefits to humans
A Dartmouth College scientist and his collaborators have created an artificial protein that organizes new materials at the nanoscale.
“This is a proof-of-principle study demonstrating that proteins can be used as effective vehicles for organizing nano-materials by design,” says senior author Gevorg Grigoryan, an assistant professor of computer science at Dartmouth. “If we learn to do this more generally – the programmable self-assembly of precisely organized molecular building blocks — this will lead to a range of new materials towards a host of applications, from medicine to energy.”
The study appears in the journal in Nature Communications. A PDF is available on request.
A “smart” paint spray can that robotically reproduces photographs as large-scale murals
Wojciech Jarosz, an assistant professor of computer science at Dartmouth College, and his collaborators invented a ‘smart’ paint spray can that robotically reproduces photographs as large-scale murals.
The computerized technique, which basically spray paints a photo, isn’t likely to spawn a wave of giant graffiti, but it can be used in digital fabrication, digital and visual arts, artistic stylization and other applications. The “smart” spray can system is a novel twist on computer-aided painting, which originated in the early 1960s and is a well-studied subject among scientists and artists.