Particle Density
Particle Density - Related Videos
06:41
Enhancing Density Maps by Removing the Majority of Particles in Single Particle Cryogenic Electron Microscopy Final Stacks
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Cited by 1 •
2024
An advanced particle selection method for cryo-EM, namely CryoSieve, improves density map resolution by removing a majority of particles in final stacks, as demonstrated through its application on a real-world dataset.
08:42
Density Gradient Ultracentrifugation
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2023
Density gradient ultracentrifugation is a common technique used to isolate and purify biomolecules and cell structures. This technique exploits the fact that, in suspension, particles that are more dense than the solvent will sediment, while those that are less dense will float. A high-speed ultracentrifuge is used to accelerate this process in order to separate biomolecules within a density gradient, which can be established by layering liquids of decreasing density in a centrifuge tube. The...
03:37
Subatomic Particles
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2020
Dalton was only partially correct about the particles that make up matter. All matter is composed of atoms, and atoms are composed of three smaller subatomic particles: protons, neutrons, and electrons. These three particles account for the mass and the charge of an atom. The Discovery of the Electron The first clue about the subatomic structure came at the end of the 19th century when J.J. Thomson discovered the electron using a cathode ray tube. This apparatus consisted of a sealed glass...
11:15
Nanosponge Tunability in Size and Crosslinking Density
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Cited by 1 •
2017
This article describes a process for tuning the size and crosslinking density of covalently crosslinked nanoparticles from linear polyesters containing pendant functionality. By tailoring synthesis parameters (polymer molecular weight, pendant functionality incorporation, and crosslinker equivalents), a desired nanoparticle size and crosslinking density can be achieved for drug delivery applications.
03:03
Generating an Ultra-Low-Density Neuronal Culture Using a High-Density Neuronal Feeder Layer
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2025
This video demonstrates the method for culturing ultra-low-density neurons in the presence of a high-density neuronal feeder layer. It establishes a co-culture of varying-density neurons, ensuring close physical proximity. The growth factors secreted by high-density neurons help neuronal survival and growth, maintaining ultra-low-density neurons for a longer time period.
FAQs
During centrifugation, density differences alter how particles move through the surrounding fluid. Molecules, organelles, viruses, and lipoproteins can therefore migrate at different rates when subjected to a centrifugal field. This differential movement creates a basis for separating components within a complex biological sample, allowing researchers to examine or purify selected material rather than treating the sample as uniform.
A particle can reach a position in the medium where its buoyant density matches that of the surrounding medium. At that point, the density relationship no longer drives continued movement to another position, so the particle becomes spatially distinguishable from components with different density characteristics. This principle helps resolve biological materials according to physical properties linked to their composition.
Measuring particle density provides a physical characterization that can help distinguish biological materials before or alongside separation. Because density expresses how mass is distributed within a particle’s volume, differences can indicate that two materials are not physically equivalent. In biochemistry, that information supports interpretation of migration behavior and helps connect a separated fraction with its likely material class.
An analytical workflow can exploit density by placing a biological sample in a fluid and applying a centrifugal field. Components then move through the medium at different rates or occupy positions determined by their buoyant-density relationship. The resulting distribution provides separated fractions or locations for subsequent isolation and analysis, linking a physical separation step to biochemical characterization.
Density-based analysis is relevant across several biological scales. It can be applied to molecules and protein complexes, larger cellular organelles, viruses, lipoproteins, nucleic acids, and other biomolecules. The value of examining these different targets lies in using their density behavior to support purification or to distinguish components that coexist in the same sample.
In biochemistry, particle density supports three complementary goals: sample purification, structural characterization, and investigation of molecular composition. Separation can help obtain a less mixed material, while the observed density behavior contributes information about how a component is characterized. Together, these uses make density relevant both to preparing biochemical samples and to interpreting their physical properties.