Nav: Home

Gold nanoparticle microsecond tracking with atomic-level localization precision achieved

November 28, 2018

Optical microscopy enables us to observe motions of protein molecular motors as they work in the biological systems. By labeling molecules of interest with appropriate probes, the motions of individual molecules can be tracked. Localization precision (how precisely we can determine the position) of moving molecule is primary determined by the photon numbers captured by a single image frame. One nanometer localization precision and millisecond time resolution can be achieved with fluorescent probes, by capturing ~10,000 photons. Although further improvement of the localization precision is crucial for deeper understanding of the operation mechanisms of molecular motors, limited number of photons obtained from the fluorescent probe have restricted the improvement. Recently, gold nanoparticles (AuNPs) which strongly scatter the incident light, have been used as an alternative of the fluorescent probes (Fig. 1). In previous studies, microsecond time resolution has been achieved with AuNPs. However, the fundamental limit of the localization precision has not been experimentally investigated in detail.

In this study, by using newly developed annular illumination total internal reflection dark-field microscopy, Ando and co-workers in Institute of Molecular Science, Japan, succeeded in achieving atomic-level, 1.3 angstrom (Å) localization precision with 40 nm AuNPs at 1 millisecond time resolution (Fig. 2). Furthermore, even at 33 microsecond time resolution, 5.4 Å localization precision has been successfully achieved.

The authors firstly investigated the fundamental law which limits the localization precision of AuNP, and confirmed that the localization precision is improved in proportion to the square root of the photon number, as previous theoretical considerations. Furthermore, the lower limit of the localization precision with a dark-field imaging system previously developed by the authors was around 3 Å, which was restricted by signal saturation of the detector. To improve the localization precision further, authors newly developed an annular illumination total internal reflection dark-field microscopy. In this system, by shaping the laser light into a ring, higher laser intensity than the previous system can be used without damaging the objective lens. Furthermore, smaller pixel size of the detector (larger number of pixels in an image) was applied to suppress the signal saturation. These improvements enable to achieve 1.3 Å localization precision at 1 millisecond time resolution.

Furthermore, the authors investigated relationship between localization precision and time resolution in detail. The developed system achieved 5.4 Å localization precision even at 33 microsecond time resolution. To minimize possible steric hindrances of AuNPs on the protein molecular motors, the authors also investigated size dependence on the localization precision, and achieved 1.9 Å localization precision at 1 millisecond time resolution with 30 nm AuNPs.

Then, by using the developed imaging system, the authors observed stepping motions of a dimeric linear molecular motor kinesin, moving along the microtubule in detail (Fig. 3). One motor domain (head) of the kinesin was labeled by 40 nm AuNP, and the motion was captured at 10 microsecond time resolution. In a previous study, unbound head showed diffusional motion only at right side of bound head on microtubule. This result implies unidirectional rotation of two heads of kinesin during linear motion. High-localization, high-speed single-particle tracking performed in this study successfully revealed details of the transition from bound to unbound states of the kinesin head. Because no apparent leftward trails were observed, the authors concluded that the kinesin actually rotates unidirectionally during the linear motion.

Not only kinesin, the technique developed in this study will capture dynamics of various protein molecular motors with atomic-level localization precision and microsecond time resolution. Indeed, the authors recently resolved the forward and backward 1-nm steps during fast unidirectional motion of a chitinase driven by processive catalysis, and revealed that processive chitinase operates as a "burnt-bridge" Brownian motor. Thus, the developed system will largely contribute to further understandings of the operation mechanisms of many protein molecular motors. Furthermore, the developed system can be also applied to visualize atomic-level motions of synthetic molecular motors, which are much smaller than the protein molecular motors.

National Institutes of Natural Sciences

Related Gold Nanoparticles Articles:

A potential breakthrough in obesity medicine with the help of gold nanoparticles
A team of researchers in Korea believes to have discovered a synthetic gold-based compound which may help patients with obesity.
Peppered with gold
Terahertz waves are becoming more important in science and technology.
Gold nanoparticles uncover amyloid fibrils
EPFL scientists have developed powerful tools to unmask the diversity of amyloid fibrils, which are associated with Alzheimer's disease and other neurodegenerative disorders.
Gold nanoparticles detect signals from cancer cells
A novel blood test that uses gold nanoparticles to detect cancer has also been shown to identify signals released by cancer cells.
What happens to gold nanoparticles in cells?
Gold nanoparticles, which are supposed to be stable in biological environments, can be degraded inside cells.
Gold nanoparticles shown to be safe and effective treatment for prostate cancer
Bio-compatible gold nanoparticles designed to convert near-infrared light to heat have been shown to safely and effectively ablate low- to intermediate-grade tumors within the prostate, according to a study conducted at the Icahn School of Medicine and published in the journal Proceedings of the National Academy of Sciences.
Actively swimming gold nanoparticles
Bacteria can actively move towards a nutrient source -- a phenomenon known as chemotaxis -- and they can move collectively in a process known as swarming.
Ultra-thin superlattices from gold nanoparticles for nanophotonics
The group of Prof. Dr. Matthias Karg at the Institute of Physical Chemistry at Heinrich Heine University Duesseldorf (HHU) in Germany is creating ultra-thin, highly ordered layers of spherical hydrogel beads that encapsulate gold or silver particles.
Gold recycling
'Urban mining', the recycling of precious metals from electronic gadgets, becomes ever more important, although processes that are both efficient and environmentally benign are still scarce.
All that is gold is not biochemically stable
Environmental nanoparticle researchers discover that gold isn't always the shining example of a biologically stable material that it's assumed to be.
More Gold Nanoparticles News and Gold Nanoparticles Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at