UMass Amherst chemists develop molecular switch for on-demand cargo release

May 10, 2018

AMHERST, Mass. - In an unexpected finding, chemist Sankaran "Thai" Thayumanavan and colleagues at the University of Massachusetts Amherst show for the first time how movement of a single chemical bond can compromise a membrane made up of more than 500 chemical bonds. Their system uses light as a switch to create a reversible, on-demand molecular control mechanism.

Thayumanavan explains, "There are many applications that one can imagine developing from these fundamental findings, especially ones that need controlled release. For example, we have shown that two compounds that would readily react with each other can be in the same solution but are separated by a very thin membrane made of a few nanometers and therefore do not react with each other."

"But upon exposure to light, the membrane gets compromised to allow the two components to react with each other," he adds. "The interesting thing is that the membrane is not permanently compromised upon exposure to light, but only when the light is on."

His postdoctoral associate Mijanur Rahaman Molla and doctoral student Poornima Rangadurai conducted most of the experimental work. The UMass Amherst group also collaborated with theoretical chemists Lucas Antony and Juan de Pablo at the University of Chicago, who modeled the system in order to more deeply understand it, Thayumanavan notes. Details are online now in Nature Chemistry.

Such reversible molecular controls that respond only when there is a source of energy are quite rare in artificial systems, he says. Usually in artificial, human-made systems, "materials are in an equilibrium state, so if you have a particle that responds to pH change and you put it into an environment that triggers a change, it stays changed. You can't put the genie back into the bottle."

By contrast, nature has engineered some "exquisitely responsive systems," the authors point out, where molecular-scale information is transferred across a membrane that can return to its original, resting state.

An example Thayumanavan likes to use refers to ATP, a cellular energy molecule that switches on and off on demand, like their new system. "I tell my students that they may have the impression that a professor never stops talking. But that is demonstrably false, if you just track ATP. When I'm talking, ATP is turned on and being used, but when the ATP is not being used, the professor goes to the resting state, i.e. shuts up. The genie does go back in the bottle."

Technically speaking, he and colleagues demonstrate that in their system, light induces actuation of a thin bi-layer of molecules made of a hydrophilic-azobenzene-hydrophobic diblock copolymer. When light is turned on, Thayumanavan says, "the azobenzene bond rotates, and this motion sends a frontal wave across about 500 bonds to compromise the membrane barrier. This allows the entire membrane to allow molecules to travel across. When we turn the light off, it closes again and no molecules can get across the membrane."

The researchers show that "the out-of-equilibrium actuation is caused by the photochemical trans-cis isomerization of the azo group, a single chemical functionality, in the middle of the interfacial layer."
This work was supported by a Department of Defense Multi-University Research Initiative (MURI) award to a group at UMass Amherst in 2016.

University of Massachusetts at Amherst

Related Molecules Articles from Brightsurf:

Finally, a way to see molecules 'wobble'
Researchers at the University of Rochester and the Fresnel Institute in France have found a way to visualize those molecules in even greater detail, showing their position and orientation in 3D, and even how they wobble and oscillate.

Water molecules are gold for nanocatalysis
Nanocatalysts made of gold nanoparticles dispersed on metal oxides are very promising for the industrial, selective oxidation of compounds, including alcohols, into valuable chemicals.

Water molecules dance in three
An international team of scientists has been able to shed new light on the properties of water at the molecular level.

How molecules self-assemble into superstructures
Most technical functional units are built bit by bit according to a well-designed construction plan.

Breaking down stubborn molecules
Seawater is more than just saltwater. The ocean is a veritable soup of chemicals.

Shaping the rings of molecules
Canadian chemists discover a natural process to control the shape of 'macrocycles,' molecules of large rings of atoms, for use in pharmaceuticals and electronics.

The mysterious movement of water molecules
Water is all around us and essential for life. Nevertheless, research into its behaviour at the atomic level -- above all how it interacts with surfaces -- is thin on the ground.

Spectroscopy: A fine sense for molecules
Scientists at the Laboratory for Attosecond Physics have developed a unique laser technology for the analysis of the molecular composition of biological samples.

Looking at the good vibes of molecules
Label-free dynamic detection of biomolecules is a major challenge in live-cell microscopy.

Colliding molecules and antiparticles
A study by Marcos Barp and Felipe Arretche from Brazil published in EPJ D shows a model of the interaction between positrons and simple molecules that is in good agreement with experimental results.

Read More: Molecules News and Molecules Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to