Friday, August 27, 2010

Label-Free Nonlinear Microscopy reveals Zebrafish Cell Cycling

Together with more explorations of intrinsic nonlinear properties of the biological samples, the nonlinear microscopy has become an extensively used tool to demonstrate morphological visualization of biological structures.

A recent report in Science August(20) issue achieves 3 dimensional reconstruction of early Zebrafish Embryos. In this study, researchers designed a framework for imaging and reconstruction unstained whole zebrafish embryos for their 10 cell division cycles and also they reported the measurements along the cell lineage with micrometer spatial resolution and minute temporal accuracy.

Click here to read more about this report:
Cell Lineage Reconstruction of Early Zebrafish Embryos Using Label-Free Nonlinear Microscopy
Nicolas Olivier, Miguel A. Luengo-Oroz, Louise Duloquin, Emmanuel Faure, Thierry Savy, Israël Veilleux, Xavier Solinas, Delphine Débarre, Paul Bourgine, Andrés Santos, Nadine Peyriéras, and Emmanuel Beaurepaire (20 August 2010)
Science 329 (5994), 967.

Sunday, August 22, 2010

Second harmonic generating (SGH) nanoprobes

A new type of nanoprobe is introduced for in vivo imaging, circumventing many of the limitations of classical fluorescence probes. These second harmonic generating (SGH) probes are nanocrystals that converts two photons into one photon of half of the wavelength under intense illumination. Unlike fluorescent probes, they don't photobleach or saturate with increasing illumination intensity.

The report onf SGH nanoprobes is reported in July issue of PNAS. Click here to read more..

Getting around the diffraction limit

Optical microscopy has been extensively used to observe biological processes, where counting and identifying of molecular structures are achieved for accurate measurements. To date, several promising technologies have been introduced to break the resolution limits of conventional microscopes (i.e diffraction limit ~200nm), including PALM,STORM and STED. These methods are called super-resolution techniques,where resolution is defined as the minimum distance or volume that can be measured between two identical particles in a given period of time. Since biological molecules are <5-10nm,getting molecular details requires imaging at this scale, which can be achieved by super-resolution methods. Another important method to break the diffraction limit is localization accuracy, where it's defined as the minimum distance or volume that one can locate a particle's position within a certain time period.Localization have paved the way to understand how some biological molecules move or change its position, including the motor protein analysis.

Simply, one should not confuse localization super-accuracy with super-resolution as aforementioned. Recently, Toprak et al. reviewed some of the methods that were used for both localization and super-resolution in fluorescence microscopy. Here is the article for further details:

Erdal Toprak, Comert Kural, Paul R. Selvin, "Super-accuracy and super-resolution getting around the diffraction limit," Methods in Enzymology 475:1-26 (2010).