DNA molecules tell nanoparticles how to self-assemble

Nature uses self-assembly to make a diversity of complex structures, such as biomolecules, virus shells, and cytoskeletal filaments. Today a key challenge is to translate this assembly process to artificial systems. DNA-coated nanoparticles provide a particularly promising approach to realizing this vision, since the base sequences can be designed to encode the formation of a chosen structure.

A recent publication from the Rogers Lab shows that interactions between DNA-coated particles can be encoded using DNA oligomers dispersed in solution that bind the particles together.  By changing the linker sequences in solution, Ph.D. students Janna Lowensohn and Alex Hensley showed that the same set of components can be directed to form a variety of different crystal structures. Going forward, this approach may be used to create programmable materials that can sense and respond to their environment.


DNA instructions

Paper: Self-Assembly and Crystallization of DNA-Coated Colloids via Linker-Encoded Interactions. Lowensohn J, Hensley A, Perlow-Zelman M, Rogers WB. Langmuir. 2020 Feb 18. doi: 10.1021/acs.langmuir.9b03391. (PubMed abstract)

Gelation without Attraction

By Bulbul Chakraborty

Gels are one of the most puzzling of all solids. Originally coined as a short form of gelatin, gels can be jelly-like as in Jello, or quite hard as in silica gels. They appear in suspensions of particles at extremely low volume fractions, and yet they are rigid. The conventional wisdom is that gels are a consequence of arrested phase separation of the suspended particles from the fluid. A natural mechanism for the arrest is attraction between the particles, which leads to the formation of filamentous networks of particles weaving through the suspending fluid.

Attraction has been viewed as being essential to the formation of gels. However, a new study published in Physical Review Research led by Carl Merrigan from the Chakraborty group, shows that “active particles” can gel even in the absence of physical attraction. Active matter, composed of particles that convert ambient energy to directed motion, has emerged as an important model for the collective behavior of biological matter such as bacterial suspensions. Using a combination of theoretical analysis and numerical simulations, the collaboration between the groups of Chakraborty and Shokef (Tel Aviv University) showed that the directed motion acts like an effective attraction, leading to gelation of the active particles.

The figure below shows the structure of these gels. As the particles become more active, they jam into clusters of immobile particles (red) surrounded by fluid regions (blue), and often opening up voids. Intriguingly, these active particles, which repel each other also show a transition from a dense glassy solid to a gel as the speed of directed motion is increased. The remarkable similarity between the behavior of passive particles with attraction and active particles suggests that biological entities could form solid-like aggregates without any physical or chemical attraction, purely as a consequence of their dynamics.

Reasearch image from Gelation without Attraction post

SPROUT and I-Corps Applications are Open

Sprout logoThe Brandeis Innovation SPROUT and I-Corps programs offer support for bench and non-bench research. Both programs offer funding in different amounts, mentorship, training and help in further exploring the commercial potential of inventions. SPROUT supports bench research, while I-Corps emphasizes training for both bench and non-bench researchers in developing the commercial potential of discoveries, with small grants and extensive training programs. You can apply to one or both programs.

  • If you have a technology / solution that you have started developing and you would like to get funding for it via SPROUT and/or I-Corps, then please complete this form
  • If you do not already have a technology, then you can complete this form to qualify for the I-Corps training program and be matched with a team

Icorps logo

SPROUT teams will get the chance to qualify for up to $30,000 in funding. The I-Corps program provides entrepreneurial training and covers the core of commercializing a technology or building a startup. It comes with an NSF $750 travel and training stipend and an NSF I-Corps certificate/digital badge.

Apply by February 25, 2020 at 11:59PM

Goode, Gelles and Kondev labs synergize in discovery of a new synergistic actin depolymerization mechanism

Shashank Shekhar, Jane Kondev, Jeff Gelles and Bruce Goode

Shashank Shekhar, Jane Kondev, Jeff Gelles and Bruce Goode

All animal and plant cells contain a highly elaborate system of filamentous protein polymers called the actin cytoskeleton, a scaffold that can be rapidly transformed to alter a cell’s shape and function. A critical step in reconfiguring this scaffold is the rapid disassembly (or turnover) of the actin filaments. But how is this achieved? It has long been known that the protein Cofilin plays a central role in this process, but it has been unclear how Cofilin achieves this feat. Cofilin can sever actin filaments into smaller fragments to promote their disassembly, but whether it also catalyzes subunit dissociation from filament ends has remained uncertain and controversial. Until now, this problem has been difficult to address because of limitations in directly observing Cofilin’s biochemical effects at filament ends. However, a new study published in Nature Communications led by postdoctoral associate Dr. Shashank Shekhar, jointly mentored by Bruce Goode, Jeff Gelles and Jane Kondev, uses microfluidics-assisted single molecule TIRF imaging to tackle the problem.

The new study shows that Cofilin and one other protein (Srv2/CAP) intimately collaborate at one end of the actin filament to accelerate subunit dissociation by over 300-fold! These are the fastest rates of actin depolymerization ever observed. Further, these results establish a new paradigm in which a protein that decorates filament sides (Cofilin) works in concert with a protein that binds to filament ends (Srv2/CAP) to produce an activity that is orders of magnitude stronger than the that of either protein alone.

Video of cofilin and Srv2/CAP collaborating

The work was funded by National Institutes of Health, National Science Foundation MRSEC and Simons Foundation grant.

Alumni and Student Researchers Wow Crowd at 2019 SciFest

With a new alumni symposium in the morning and a poster session filling three floors of the Science Center atrium in the afternoon, this year’s SciFest IX set a new standard for Brandeis Science’s annual celebration of undergraduate research.

Photos: Heratch Ekmekjian

Since 2011, a poster session featuring the results from ongoing projects belonging to undergraduates doing science research has been the high point of summer in the Division of Science at Brandeis. This year, for the first time, we invited Brandeis alumni scientists to speak in a morning symposium entitled “A Celebration of Brandeis’ Undergraduate Science Education”, including:

Students and faculty in the audience were treated to a history of Brandeis and reflections on many of the Brandeis professors and courses that set them on their career path and whose influence persists to the present in how they approach their science, and on lessons they learned that continue to guide their work.

After lunch in the campus center, the crowd climbed up to the Shapiro Science Center for the poster session. 123 students presented 117 posters on topics from high-energy physics to biomaterials and from quantum chemistry to fruit fly behavior. As President Ron Liebowitz noted in an email to the Science community after the event:

The energy in Shapiro during the poster session was electric.  The students’ confidence and excitement over sharing their research can only give us great optimism about the future: they are “all in” when it comes to doing basic research, but also seeing how such research can be applied in the name of helping others.

Many of the posters can be found in the hallway in Gerstenzang – look for them when classes start again in a few weeks!

SciFest IX by the numbers

  • 117 posters
  • 123 student presenters (out of approx. 210 summer student researchers)
    • 105 Brandeis students
      • 99 presenting research done on campus
      • 6 presenting work done over the summer off-campus
    • 18 visiting students
  • 45 Brandeis faculty advisors from 7 departments
    • Biochemistry (7)
    • Biology (18)
    • Chemistry (8)
    • Computer Science (1)
    • Physics (6)
    • Psychology (5)
    • Sociology (1)

John Wardle part of team that produces first-ever black hole image

Credit: Event Horizon Telescope Collaboration

John Wardle, Professor of Astrophysics and the Head of the Division of Science, has been playing an integral role in bringing the first-ever image of a black hole to realization. Announced today, the image of the M87 black hole is being hailed as a major scientific breakthrough. Wardle serves on four of the Event Horizon Telescope’s 23 working groups, helps analyze the polarization of the M87 black hole’s radio emissions, and serves on the publication working group. This announcement was made in a series of six papers published in a special issue of The Astrophysical Journal Letters.

Read more: BrandeisNow, Event Horizon Telescope, NSF News Release

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