scholarly journals DETERMINATION OF THE POLARIZATION OPTICAL PROPERTIES OF THE AMYLOID-CONGO RED COMPLEX BY PHASE MODULATION MICROSPECTROPHOTOMETRY

1974 ◽  
Vol 22 (12) ◽  
pp. 1105-1112 ◽  
Author(s):  
DOUGLASS L. TAYLOR ◽  
ROBERT D. ALLEN ◽  
EARL P. BENDITT
Keyword(s):  
Circular Dichroism ◽  
Congo Red ◽  
Phase Modulation ◽  
Optical Rotation ◽  
Polarized Light ◽  
Visible Spectrum ◽  
Linear Dichroism ◽  
Cotton Effect ◽  
Optical Rotatory Dispersion ◽  
Circular Dichroïsm

The polarization properties responsible for the classical "green birefringence" of the amyloid-Congo red complex have been determined by a new optical method, phase modulation microspectrophotometry. This method now makes possible the measurement of one optical property at a time (birefringence, optical rotation, linear dichroism and circular dichroism throughout the visible spectrum) in complex specimens in which visible contrast in polarized light is the result of a mixture of polarization effects. The green birefringence is explained by a combination of optical effects, the strongest of which are dispersion of birefringence and linear dichroism superimposed on the smaller effects of circular dichroism and optical rotatory dispersion. The interaction of the planar dye molecules with the amyloid protein induces an extrinsic Cotton effect.

Origin of the optical activity of silver thiogallate

2000 ◽  
Vol 33 (1) ◽  
pp. 126-129 ◽  
Author(s):  
J. Etxebarria ◽  
C. L. Folcia ◽  
J. Ortega
Keyword(s):  
Circular Dichroism ◽  
Optical Activity ◽  
Room Temperature ◽  
Optical Rotation ◽  
Linear Dichroism ◽  
Optical Data ◽  
Point Dipole ◽  
Reliable Measurement ◽  
Photoelastic Modulator ◽  
Circular Dichroïsm

Using a high-accuracy universal polarimeter, the birefringence and optical activity of AgGaS2have been determined between 300 and 500 K. The optical rotation has been found to be 94° mm−1at room temperature for a wavelength of 632.8 nm. This value is unexpectedly small if compared with values close to 1000° mm−1at 485 nm reported previously. The present optical data are well explained using a point-dipole model for the calculation of the refractive indices and optical activity. The main contributors to the optical rotation are the S atoms. However, these atoms are not at positions especially suitable to promote extremely large gyrations. Consequently, the size of the optical rotation reported before in the blue part of the spectrum is presumably due to the existence of a circular dichroism band close to that region. Using an optical system based on a photoelastic modulator, a strong linear dichroism peak has been measured in the range 450–500 nm. This fact has prevented reliable measurement of the circular dichroism.

Theory of laser-induced optical activity

1979 ◽  
Vol 365 (1722) ◽  
pp. 327-343 ◽  
Keyword(s):  
Circular Dichroism ◽  
Probe Beam ◽  
Quantum Electrodynamics ◽  
Rayleigh Scattering ◽  
Optical Rotation ◽  
Polarized Light ◽  
Circularly Polarized Light ◽  
State Process ◽  
Intense Beam ◽  
Circular Dichroïsm

An achiral system bathed in an intense beam of circularly polarized light shows chiral behaviour which may be detected with an auxiliary beam of polarized light. In this paper, expressions are derived for differential absorption rates, optical rotation of a plane polarized probe beam and circular differential scattering intensities. The theory of these two, three and four photon processes is developed by using quantum electrodynamics in electric dipole approximation. Two types of circular dichroism are distinguished: ( a ) the transition exhibiting induced dichroism is one-photon allowed, with chirality induced by scattering of the laser beam, or ( b ) the transition is two-photon allowed with absorption of a photon from each beam. In both, the induced circular dichroism is linearly dependent on the intensity of the inducing beam. Circular dichroism of type ( a ) is also discussed from the dressed-molecule viewpoint, and it is shown how a canonical transformation may be used to recover the results more simply. The possibility of observing Doppler-free circular dichroism is indicated. The induced optical rotation is analysed as a two-state process with transitions involving change of polarization only. The angle of rotation is linearly dependent on the intensity of the intense beam; its sign depends on the helicity. It is shown that, for non-forward Rayleigh scattering of the probe beam in the presence of an intense beam of light, the scattering intensity depends on the relative helicities of the two beams, and the differential intensity is proportional to the incident intensities.

Optical rotatory dispersion and circular dichroism of diastereoisomers. I. The ephedrines and chloramphenicols

1969 ◽  
Vol 47 (11) ◽  
pp. 1957-1963 ◽  
Author(s):  
L. A. Mitscher ◽  
F. Kautz ◽  
J. LaPidus
Keyword(s):  
Circular Dichroism ◽  
Absorption Band ◽  
Absolute Configuration ◽  
Cotton Effect ◽  
Optical Rotatory Dispersion ◽  
Rotatory Dispersion ◽  
Optical Rotatory ◽  
Apparent Correlation ◽  
Circular Dichroïsm ◽  
Erroneous Assignment

Optical rotatory dispersion (o.r.d.) and circular dichroism measurements are reported for all four diastereoisomers in both the ephedrine and chloramphenicol series. The Cotton effect associated with the 1Lb absorption band is a reliable guide to absolute configuration in both series whereas the 1La band is not. Circular dichroism measurements are preferred as the 1La band dominates the o.r.d. curves to such an extent that erroneous assignment is quite possible. An attempt to relate the sign and intensity of the 1Lb Cotton effect with rotamer population failed due to lack of apparent correlation.

scholarly journals Mass-resolved electronic circular dichroism ion spectroscopy

Science ◽  
2020 ◽  
Vol 368 (6498) ◽  
pp. 1465-1468 ◽  
Author(s):  
Steven Daly ◽  
Frédéric Rosu ◽  
Valérie Gabelica
Keyword(s):  
Circular Dichroism ◽  
Three Dimensional ◽  
Polarized Light ◽  
Negative Ions ◽  
Data Interpretation ◽  
Electronic Circular Dichroism ◽  
Circularly Polarized Light ◽  
Chiral Compounds ◽  
Electron Photodetachment ◽  
Circular Dichroïsm

DNA and proteins are chiral: Their three-dimensional structures cannot be superimposed with their mirror images. Circular dichroism spectroscopy is widely used to characterize chiral compounds, but data interpretation is difficult in the case of mixtures. We recorded the electronic circular dichroism spectra of DNA helices separated in a mass spectrometer. We studied guanine-rich strands having various secondary structures, electrosprayed them as negative ions, irradiated them with an ultraviolet nanosecond optical parametric oscillator laser, and measured the difference in electron photodetachment efficiency between left and right circularly polarized light. The reconstructed circular dichroism ion spectra resembled those of their solution-phase counterparts, thereby allowing us to assign the DNA helical topology. The ability to measure circular dichroism directly on biomolecular ions expands the capabilities of mass spectrometry for structural analysis.

Sign in / Sign up

Export Citation Format

Share Document