Circular Intensity Differential Scattering for Label-Free Chromatin Characterization: A Review for Optical Microscopy

Abstract

Circular Intensity Differential Scattering (CIDS) provides a differential measurement of the circular right and left polarized light and has been proven to be a gold standard label-free technique to study the molecular conformation of complex biopolymers, such as chromatin. In early works, it has been shown that the scattering component of the CIDS signal gives information from the long-range chiral organization on a scale down to 1/10th–1/20th of the excitation wavelength, leading to information related to the structure and orientation of biopolymers in situ at the nanoscale. In this paper, we review the typical methods and technologies employed for measuring this signal coming from complex macro-molecules ordering. Additionally, we include a general description of the experimental architectures employed for spectroscopic CIDS measurements, angular or spectral, and of the most recent advances in the field of optical imaging microscopy, allowing a visualization of the chromatin organization in situ.

Theory of Rayleigh–Brillouin optical activity light scattering applicable to chiral liquids

“…19,[76][77][78] Although our focus in this paper has been on small molecules, similar ideas can be developed for larger scatterers, including large biomolecules. [27][28][29][30][31] We will return to these and related tasks elsewhere.…”

Review on Complete Mueller Matrix Optical Scanning Microscopy Imaging

“…Due to the low technological requirement, the temporal control of the polarized light was the first approach for such instrumentation based on the use of rotating optical features or electro-optics modulators. In a single-point measurement, the technique was based on the differential polarized (linear or circular) intensity collection, leading to the determination of only few Mueller matrix elements [32][33][34][35][36][37]. Thus, the method has been deported into an SLM configuration for imaging high-ordered macromolecules and biopolymers, such as chromatin or blood cells [38][39][40][41][42][43].…”

Multiparametric Remote Investigation in the near-IR through Optical Fiber for In Situ Measurements

“…On the one hand, the distribution of the light scattering angle erases cumulative factors such as (1) the roughness of the sample surface and (2) the molecular species under illumination [ 22 ]. More particularly, the scattering light is overly sensitive to the difference in size or the ratio of the refractive index between scatters and the molecular content at the sub-micrometric scale [ 23 ]. On the other hand, the tissue orientation could drastically modify the reflectance spectrum by considering linear polarized light illumination.…”