قالب وردپرس درنا توس
Home / Science / Engineers accurately position thousands of nanoscale molecular devices

Engineers accurately position thousands of nanoscale molecular devices



Flowers made from molecular devices

The researchers put more than 3,000 luminous moon-shaped nano-scale molecular devices into a flower-shaped instrument to indicate the polarization of light. The “moon” in each of the 12 petals points in different directions, and only emits light when illuminated by polarized light that matches its direction. The end result is a flower, and as the polarization of the light shining on it rotates, the petals glow sequentially. The distance of this flower is smaller than the width of a human hair, proving that thousands of molecules can be reliably oriented on the chip surface. Credit: Ashwin Gopinath / Caltech

The proof-of-concept project paved the way for the integration of molecules and computer chips.

Engineers have developed a technique that allows them to accurately place the microscopic devices formed after folding DNA The molecule is not only in a specific location but also in a specific direction.

As a proof of concept, they arranged more than 3,000 luminous moon-shaped nano-scale molecular devices into a flower-shaped instrument to indicate the polarization of light. Each of the 1

2 petals points in different directions around the center of the flower, and in each petal, there are approximately 250 satellites aligned with the direction of the petals. Because each moon emits light only when it is illuminated by polarized light that matches its direction, the end result is a flower whose petals illuminate in turn when the polarization of the light shining on it rotates. The distance of this flower is smaller than the width of a human hair, proving that thousands of molecules can be reliably oriented on the chip surface.

This method for precise placement and orientation of DNA-based molecular devices may enable the use of these molecular devices to power new types of chips that integrate molecular biosensors with optical and electronic devices that can be used for DNA sequencing or measurement of thousands The concentration of this protein at a time.

The research was published by the journal on February 19, 2021 science, Is based on the work of Paul Rothemund (BS ’94) of Caltech, Professor of Bioengineering, Computation and Mathematical Sciences, Computation and Nervous System Research, and his colleagues for more than 15 years. In 2006, Rothemund showed that DNA can be folded into precise shapes using a technique called DNA origami. In 2009, Rothemund and colleagues of IBM Research Almaden described a technique for positioning DNA origami in precise locations on a surface. To do this, they used an electron beam-based printing process and created a “sticky” patch with the same size and shape as origami. In particular, they showed that the origami triangles are bound at the position of the triangular adhesive patch.

Next are Rothemund and Ashwin Gopinath. She was a senior postdoctoral scholar at the California Institute of Technology and is now with, Perfected and expanded the technology to prove that molecular devices constructed from DNA origami can be reliably integrated into larger optical devices. Rothemund said: “The technical obstacle is how to reproducibly organize a large number of molecular devices into the correct pattern on the various materials used in the chip.”

Starry night

The illuminated copy of “Starry Sky” contains 65,536 pixels, the width of a dime. Credit: Ashwin Gopinath / Caltech

In 2016, Rothhemund and Gopinath showed that triangular origami with fluorescent molecules can be used to replicate Vincent Van Gogh’s 65,000 pixels starry night. In this work, triangular DNA origami was used to locate fluorescent molecules in a bacterial-sized optical cavity. The precise placement of fluorescent molecules is critical, because moving 100 nanometers to the left or right will darken or brighten the pixel more than five times.

But the Achilles heel of this technology is: “Because the triangles are equilateral and can be freely rotated and flipped up and down, they can be laid flat on the triangular adhesive patch on the surface in six different ways. This means we cannot use Any device that needs a specific direction to run. We are stuck on a device that faces up, down, or in any direction that works fine.” Gopinath said. Molecular equipment used for DNA sequencing or protein measurement must absolutely face up, so the team’s earlier technology would destroy 50% of the equipment. For devices that also require a unique direction of rotation (such as transistors), only 16% will work.

Therefore, the first problem to be solved is to make DNA origami land reliably with the correct side up. Rotmund said: “It’s like ensuring that the toast always magically makes the butter face up when it is poured on the floor.” To the researchers’ surprise, a flexible DNA strand carpet was applied to one side of the origami. Land on 95% of them face up. But the problem of controlling rotation still exists. The researchers’ attempt at right-angled triangles with three different side lengths was an attempt to land in the preferred rotation method.

However, after trying to make 40% of the right triangles point in the right direction, Gopinath recruited computer scientist Chris Thachuk, Washington University,Yes” science Thesis, a former postdoctoral fellow at California Institute of Technology; David Kirkpatrick of the University of British Columbia, also ” science paper. Their job is to find a shape, no matter in which direction it falls, it will only get stuck in the expected direction. The computer scientist’s solution is a disk with an eccentric hole, which the researchers call a “small satellite.” “Mathematical proof shows that, unlike right triangles, small satellites can rotate smoothly to find the best alignment with their sticky patches without getting stuck. Laboratory experiments have proved that more than 98% of small satellites are found on their sticky patches. In the right direction.

Then, the research team added special fluorescent molecules that stuck themselves tightly in the DNA helix of the small satellite, perpendicular to the axis of the helix. This ensures that the fluorescent molecules in the moon all face the same direction and will emit the brightest light when stimulated by a specific polarized light. Gopinath said: “It seems that every molecule has a small antenna. Only when the polarization of light matches the direction of the antenna can it receive light energy most effectively.” This simple effect makes it possible to construct polarization-sensitive flowers.

Utilizing reliable methods for controlling the up and down and rotation directions of DNA origami, various molecular devices can now be integrated into computer chips inexpensively with high yields for various potential applications. For example, Rothhemund and Gopinath established a company called Palamedrix to commercialize a technology for manufacturing semiconductor chips that can simultaneously study all proteins related to human health. California Institute of Technology has applied for a patent for this work.

Reference: Ashwin Gopinath, Chris Thachuk, Anya Mitskovets, Harry A. Atwater, David Kirkpatrick and Paul WK Rothemund, “Absolute and Arbitrary Orientation of Single Molecule Shapes”, February 19, 2021, science.
DOI: 10.1126/science.abd6179
California Institute of Technology Author: 20181029-101527551

The title of the paper is “Absolute and Arbitrary Direction of Single Molecule Shape”. California Institute of Technology’s co-authors include Harry Atwater, Howard Hughes Professor of Applied Physics and Materials Science, and former graduate student Anna Mitskovets (PhD ’20 ). This work was supported by the Office of Naval Research, Office of Air Force Scientific Research, National Science Foundation, Orr Family Foundation, Abedin Institute and Banting Postdoctoral Fellowship.




Source link