Problems of CD spectrometers (V): Can we measure CD and LD simultaneously? Comments on differential polarization microscopy (CD and linear dichroism)

Shindo, Yohji; Nishio, Motohide; Maeda, Shiro

doi:10.1002/bip.360300318

Cited by 72 publications

(71 citation statements)

References 16 publications

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“…Several articles have dealt with these aspects using Jones or Stokes-Mueller formalisms. [121][122][123][124] The observed CD signal depends not only on the real CD of the sample, but also on LD and LB, the latter components are often order of magnitudes larger than the true CD signal to be measured.…”

Section: Discussionmentioning

confidence: 99%

“…The measured CD signal can be expressed in a simplified form as Shindo 123 where, CD app is CD measured by the instrument, G 0 is an apparatus constant, CD true is the real CD of the sample, a is the residual static birefringence of modulator, y is the angular rotation of the sample, LD is linear dichroism and LD 0 is 458 linear dichroism, LB is linear birefringence and LB 0 is 458 linear birefringence. The attempt to collect several measurements by rotating the sample about the light propagation axis by an angle y is able to detect the presence rather than to compensate the linear anisotropies effects.…”

Section: Discussionmentioning

confidence: 99%

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Experimental aspects of solid state circular dichroism

2009

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Experimental aspects of solid state circular dichroism

2009

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“…CW stirring, which generates right-handed torsional flows, always resulted in larger spectral intensities in both CD and LD spectroscopy than CCW stirring. Because CD spectra, applied to anisotropic macromolecules, may be contaminated by LD as an intrinsic artifact, 18,33 quantitative treatments of the chiroptical features of aligned DNA will occasionally be misleading. Hence, the observed difference should be discussed using LD spectral studies.…”

Section: ¹1mentioning

confidence: 99%

Spectroscopic Visualization of Right- and Left-Handed Helical Alignments of DNA in Chiral Vortex Flows

Tsujimoto¹,

Ie²,

Ando³

et al. 2011

Bulletin of the Chemical Society of Japan

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In a vortex generated by mechanical rotary stirring in an optical cell, DNA molecules in pure water temporarily align helically to the spiral flow, and dynamically display strong induced circular dichroism (CD) and linear dichroism (LD) responses. Although a sample solution without stirring provided the characteristic CD spectral pattern of DNA, an entirely different macroscopic CD spectral pattern with a much larger intensity and LD spectrum appeared upon mechanical rotary stirring of the sample solution. Clockwise (CW) and counterclockwise (CCW) stirring resulted in mirror-image CD spectral profiles and virtually the same LD profiles with different intensities. The CW stirring of the sample solution in LD spectroscopy always resulted in larger spectral intensities than CCW stirring, but the differences became negligible upon addition of NaCl or ethidium bromide. The observed CD and LD responses of the stirred sample solution decreased simultaneously as the double-stranded structure denatures with increasing temperatures. The results obtained in this study indicate that DNA, when it forms a double-stranded structure, can effectively align in the vortex flows, and show hydrodynamic preference to a right-handed vortex than to a left-handed vortex.Chiral hydrodynamic interactions between DNA and macroscopic torsional fluids attract considerable interest because of the involvement of microscopic and macroscopic chirality in biomolecular systems. DNA can hydrodynamically align and stretch in certain linear fluid flows, 15 where a worm-like chain model can reasonably account for the elastic behaviors and hydrodynamic interactions of DNA. 6 Here, as an innovative subject related to those studies, we noticed for the torsional flow dynamics of DNA, having a right-handed helical doublestranded structure, in chiral fluids such as a vortex that is recognized as one possible origin of chiral symmetry breaking in nature.710 Strick et al. reported the first single-molecule measurements of DNA topology using magnetic tweezers; they measured the extension and force of individual -phage DNA molecules and found that positively supercoiled DNA was more difficult to stretch than negatively supercoiled DNA. 11Other studies have also demonstrated experimentally the intrinsic chiral twist elasticity of DNA.1215 These studies raise an important question: What happens to DNA in a chiral macroscopic vortex generated by clockwise (CW) or counterclockwise (CCW) stirring? The present study reports a successful spectroscopic visualization of macroscopic helical alignments of DNA in a vortex. DNA, when it forms a doublestranded structure, can effectively align in the vortex flows, and it shows hydrodynamic preference to a right-handed vortex than to a left-handed vortex.It is known that certain achiral molecules form optically active assemblies in torsional fluids generated upon rotary stirring.9,10 Kaizu and co-workers 10a and Ribó and co-workers 10b10d have reported pioneering examples in which electrostatic J-aggregates of (4-sulfophenyl)p...

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“…The detailed contents of each Mueller matrix are described in a previous paper. 25 Using general procedures of Mueller matrix calculation for polarization measurements, 25,27,32 …”

Section: Theoretical Background Based On Mueller Matrix Calculationsmentioning

confidence: 99%

“…27 Thus, CD measurements of anisotropic specimens, such as crystals, have been limited. Recently, some methods and apparatuses dedicated to CD and optical rotatory dispersion measurements of linear anisotropic samples have been developed.…”

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confidence: 99%

Development of vacuum‐ultraviolet circular dichroism measurement system using a polarizing undulator

et al. 2006

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We have developed an improved circular dichroism (CD) and linear dichroism (LD) simultaneous measurement system for the vacuum ultraviolet (VUV) region by polarization modulation techniques using a four-period Onuki-type crossed undulator as a polarized light source. The system has been constructed at the VUV beamline BL-5 in the electron storage ring TERAS, at AIST. Our improvements, in particular the adoption of an optical chopper as the detection method of incident light, have resulted in a flat baseline and a consequent simplification of the Mueller matrix calculation for our optical system. Based on the Mueller matrix calculation, we have successfully measured real VUV-CD and LD spectra of leucine films for wavelengths down to 160 nm with absolute optical constants. The obtained spectra show good consistency with spectra measured by conventional methods.

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Problems of CD spectrometers (V): Can we measure CD and LD simultaneously? Comments on differential polarization microscopy (CD and linear dichroism)

Cited by 72 publications

References 16 publications

Experimental aspects of solid state circular dichroism

Experimental aspects of solid state circular dichroism

Spectroscopic Visualization of Right- and Left-Handed Helical Alignments of DNA in Chiral Vortex Flows

Development of vacuum‐ultraviolet circular dichroism measurement system using a polarizing undulator

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