Circular Intensity Differential Scattering Research Articles

Circular intensity differential scattering of light by hierarchical molecular structures

We show that circular intensity differential scattering (CIDS) of light by macromolecules with different levels of chiral structure is the superposition of the CIDS from each individual level. As an example, we treat a model superhelix with anisotropic polarizability.

Circular Dichroism Studies on Single Chinese Hamster Cells

The circular dichroism (CD) and circular intensity differential scattering (CIDS) contributions to the CD of single Chinese hamster (CHO) cells have been measured as a function of the position in the cell cycle. The data are analyzed in three main spectral regions: (1) the region above 290 nm (scattering region), (2) the 250-290-nm regions (nucleic acid absorption region), and (3) the region below 240 nm (protein absorption region). The results show that CD/CIDS microspectrophotometry is a good indicator of the cell cycle phase. The results are consistent with the view that chromatin is organized in chiral superstructures which differentially scatter circularly polarized light. These structures appear highly specific and repeatable as the cell passes through its cycle.

Expressions for the interpretation of circular intensity differential scattering of chiral aggregates.

AbstractThe derivation of compact expressions of the circular intensity differential scattering (CIDS) of chiral molecules is presented in the first Born approximation of the fields. The expressions derived are valid for a suspension of scattering chiral particles free to adopt any orientation in solution. The connection is established between the preferential scattering cross section for right‐ vs left‐circularly polarized light for a given scattering angle and the geometrical parameters of the molecule. As observed experimentally, the equations predict that the circular differential scattering patterns must show as a function of the scattering angle a series of lobes of alternating sign. In between these lobes, zeros in the differential scattering cross section occur. For the case of two dipole moments arranged in chiral fashion, an expression is derived that shows how the relative arrangement of the dipoles and their separation relative to the wavelength of light control the number and the position of the zeros. A compact expression predicting the CIDS of a sample for very small angles of scattering is derived for a system of helices whose dimensions are small compared with the wavelength of light. Finally, the presence of CIDS in a sample is related to the appearance of anomalous signals in the CD spectrum of chiral systems. Expressions and computations of the magnitudes and sign of the anomalies are presented. The expressions obtained confirm the main features of the experimental CIDS patterns of chiral molecules previously published.

Quantum mechanical treatment of circular intensity differential scattering: The elastic process

A quantum mechanical derivation is presented for the circular intensity differential scattering (CIDS) of a molecule of arbitrary size. Expressions for the special case where the scattering system is composed of a collection of independent scatterers are derived and the relationship is shown between the quantum mechanical expressions and previous expressions obtained using classical electrodynamics. The differences between elastic and inelastic CIDS are then discussed, as well as the differences between the CIDS due to large and small scattering systems.

The Circular Intensity Differential Scattering (CIDS) of Cholesteric and Blue Mesophases

Abstract The circular intensity differential scattering of several cholesteric mixtures of CB-15 and ZLI 1612 has been measured as a function of the scattering angle and for different ratios of pitch/wavelength. These mesophases show large CIDS ratios varying with both composition and scattering angle. Difficulties encountered in performing these experiments are discussed. The comparison of the results with a theoretical model that uses the second Born approximation shows good agreement. Preliminary studies of the cholesteric-blue phase transition as monitored by changes in the CIDS signal are also presented. The possibility to obtain information about the structural organization of these chiral mesophases and their degree of crystallinity, order parameters, etc., from the CIDS measurements is discussed.

Use of circularly polarized light to study biological macromolecules

Abstract

Circular intensity differential scattering of light. IV. Randomly oriented species

The theory of circular intensity differential scattering (CIDS) of light by a solution of randomly oriented molecules of arbitrary geometry has been derived. The molecules are treated as a set of polarizability tensors. The CIDS as a function of scattering angle is obtained in closed form. The CIDS depends on the distances and angle between all the polarizabilities in the molecule. Numerical calculations of helices made up of uniaxial polarizabilities, directed along the tangent to the helix, are shown as a function of helix geometry. The calculated values of the CIDS indicate that they should provide a useful, new experimental technique to determine the structures of biomolecular aggregates.