General Information (more on wikipidia)

Species Molecular Weight (g/mol) Density (g/L) Radius (m) Reference
Molecular probes MW D R [1]

This article largely refers to microspheres or protein protocells as small spherical units postulated by some scientists as a key stage in the origin of life. The term microsphere is otherwise widely being used in various areas, such as, materials and pharmaceutical sciences, for spherical particles composed of various natural and synthetic materials with diameters in the micrometer range.
In 1953, Stanley Miller and Harold Urey demonstrated that many simple biomolecules could be formed spontaneously from inorganic precursor compounds under laboratory conditions designed to mimic those found on Earth before the evolution of life. Of particular interest was the substantial yield of amino acids obtained, since amino acids are the building blocks for proteins.
In 1957, Sidney Fox demonstrated that amino acids could be encouraged to polymerize upon exposure to moderate heat. These polypeptides formed spherical shells—microspheres. Under appropriate conditions, microspheres will bud new spheres at their surfaces.

The number of microspheres may be determined by the following equation:

\begin{align} nb\ spheres\ per\ ml = \frac{6C \ 10^{12}}{\rho \pi \Phi^{3}} \end{align}


  • C is the concentration of suspended beads in g/mL ((0.02 g/mL for a 2% suspension) )
  • $\Phi$ is the diameter of microspheres in μm
  • $\rho$ is the density of polymer in g/mL (1.05 for polystyrene)

In the case of micro and nano spheres, the stokes-einstein equation produces good approximation of the diffusion coeficients.

Diffusion of 20nm Beads:

  • In Water:
  • In PBS:

Diffusion of 40nm Beads:

  • In Water:
  • In PBS:

Diffusion of 100nm Beads:

  • In Water:
  • In PBS:
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