Tag Archives: Alexandria N. Marchi

World’s largest DNA origami: 200nm x 300nm

If the 200nm x 300nm size is the world’s largest DNA origami, what is the standard size?  Before you get the answer to that question, here’s more about the world’s largest from a Sept. 11, 2014 news item on Nanowerk,

Researchers from North Carolina State University, Duke University and the University of Copenhagen have created the world’s largest DNA origami, which are nanoscale constructions with applications ranging from biomedical research to nanoelectronics.

“These origami can be customized for use in everything from studying cell behavior to creating templates for the nanofabrication of electronic components,” says Dr. Thom LaBean, an associate professor of materials science and engineering at NC State and senior author of a paper describing the work …

A Sept. ?, 2014 North Carolina State University (NCSU) news release, which originated the news item, describes DNA origami and the process for creating it,

DNA origami are self-assembling biochemical structures that are made up of two types of DNA. To make DNA origami, researchers begin with a biologically derived strand of DNA called the scaffold strand. The researchers then design customized synthetic strands of DNA, called staple strands. Each staple strand is made up of a specific sequence of bases (adenine, cytosine, thaline and guanine – the building blocks of DNA), which is designed to pair with specific subsequences on the scaffold strand.

The staple strands are introduced into a solution containing the scaffold strand, and the solution is then heated and cooled. During this process, each staple strand attaches to specific sections of the scaffold strand, pulling those sections together and folding the scaffold strand into a specific shape.

Here’s the answer to the question I asked earlier about the standard size for DNA origami and a description for how the researchers approached the problem of making a bigger piece (from the news release,

The standard for DNA origami has long been limited to a scaffold strand that is made up of 7,249 bases, creating structures that measure roughly 70 nanometers (nm) by 90 nm, though the shapes may vary.

However, the research team led by LaBean has now created DNA origami consisting of 51,466 bases, measuring approximately 200 nm by 300 nm.

“We had to do two things to make this viable,” says Dr. Alexandria Marchi, lead author of the paper and a postdoctoral researcher at Duke. “First we had to develop a custom scaffold strand that contained 51 kilobases. We did that with the help of molecular biologist Stanley Brown at the University of Copenhagen.

“Second, in order to make this economically feasible, we had to find a cost-effective way of synthesizing staple strands – because we went from needing 220 staple strands to needing more than 1,600,” Marchi says.

The researchers did this by using what is essentially a converted inkjet printer to synthesize DNA directly onto a plastic chip.

“The technique we used not only creates large DNA origami, but has a fairly uniform output,” LaBean says. “More than 90 percent of the origami are self-assembling properly.”

For the curious, a link to and a citation for the paper,

Toward Larger DNA Origami by Alexandria N. Marchi, *Ishtiaq Saaem*, Briana N. Vogen, Stanley Brown, and Thomas H. LaBean. Nano Lett., Article ASAP DOI: 10.1021/nl502626s Publication Date (Web): September 1, 2014
Copyright © 2014 American Chemical Society

This paper is behind a paywall.

*May 10, 2021 According to a comment on my ‘About’ page, Dr. Saaem has pled guilty to obstruction of justice in a case concerning ricin (a deadly toxin). You can read a full account of Saaem’s pleading in an April 13, 2021 US Attorney’s Office, District of Massachusetts release,

According to court records, Saaem held a Ph.D. in biomedical engineering, resided in Massachusetts and worked as the director of advanced research at a biotechnology firm based in Massachusetts. Saaem became interested in acquiring ricin from castor beans as well as convallatoxin, a poison found in lily of the valley plants, after watching “Breaking Bad,” a popular television show. Saaem ordered online 100 packets of castor beans, each containing eight seeds. Saaem falsely told law enforcement agents that he purchased castor beans for planting at his apartment for decoration and that he had accidentally purchased 100 packets instead of one. After he spoke to agents, Saaem researched tasteless poisons that could be made at home.

The charge of obstruction of justice provides for a sentence of up to 20 years in prison, three years of supervised release and a fine of up to $250,000. Sentences are imposed by a federal district court judge based upon the Sentencing Guidelines and other statutory factors.

 

According to news reports, Dr. Saaem will be sentenced in August 2021.