Rather, these visible lines should represent variations of spatial density of the much more numerous microtubules under the limit of optical resolution.
Similar splitting to >200 nm was also seen for Z1Z2, normally at the limit of optical resolution with a separation of ∼100 nm (Young et al., 1998).
Conventional light microscopy has been widely used to determine the approximate localization of centrosomal proteins, but the dimensions of centrioles are close to the Abbe-Rayleigh diffraction limit of optical resolution, that is at best 200 nm in the lateral and 500 nm in the axial direction (Schermelleh et al., 2010).
FRET is a widely used technique in biology that allows the determination of interactions between two proteins of interest within the range of 3 10 nm, thus allowing discrimination between simple co-localisation within the limits of the optical resolution of light microscopes and genuine interaction.
Our failure to detect volume and compaction differences indicates that possible differences are below the limits of light optical resolution.
However, a critical factor that physically limits the optical resolution of microscopy in general is diffraction [ 2].
In part, this lack of structural knowledge has been a consequence of technical limitations, most prominently the diffraction limited optical resolution of conventional fluorescence microscopy and the inherent difficulties of electron microscopy (EM) to explore the 3D topography of multiple structural components.
Recent developments in superresolution, an area of optical physics and engineering with claims of transcending the stated resolution limits of optical instruments, are reviewed and their possible relevance to visual spatial processing and to the exploration of the eye's structure are assessed.
Importantly, unlike single-molecule FISH, digital, one-step RT-PCR is not limited by the optical resolution of mRNA transcripts that cluster in vivo.
We define the notion of standard quantum limit (SQL) in optical resolution, set by the quantum noise of usual coherent light, and show that it can be much lower than the diffraction limit.
