Light-scattering effects on the circular dichroism of chloroplasts

Philipson, Kenneth D.; Sauer, Kenneth

doi:10.1021/bi00742a015

Cited by 43 publications

(41 citation statements)

References 27 publications

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“…Although these thylakoids fragments are less highly organized than whole chloroplasts, they both have approximately the same degree of Chl aggregation (as seen from fluorescence emission spectra). In contrast to Philipson and Sauer (23), we feel that the C.D. bands in the red region of the spectrum are a true reflection of Chl organization and not due to intrinsic differences in lightscattering properties.…”

Section: And Conclusioncontrasting

confidence: 81%

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Partial Analysis of the Bands Seen in Circular Dichroism Spectra of Green and Blue-Green Algal Cells and Thylakoids

Nathanson¹,

White²

1977

Plant Physiol.

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A comparison was made of the circular dichroism (C.D.) spectra of Chlorella, Eugkna, and Anacystis cells and thylakoids. Analyses of the spectra reveal that these C.D. bands are similar to those observed previously in whole spinach choloroplasts and subchloroplast particles. C.D. spectra of Euglena chloroplasts show bands at longer wavelengths than previously reported. From comparisons of circular dichroism spectra and fine structure, it was concluded that: (a) bands seen in circular dichroism spectra were not ihe result of light scattering from thylakoid membranes; and (b) bands seen in the C.D. spectra of nonmembranous systems (previously reported) could account for circular dichroism of algae. We also concluded that comparisons would have to be made with model systems in order to correct for effects of absorption flattening, concentration obscuring, and differential light scattering of membranous systems.Studies have been reported using circular dichroism techniques to elucidate chloroplast structure by comparison of the C.D.' spectra of Chl a in solution and as organized into membranes (particulate Chl). Dratz et al. (10) linolenic acid to a suspension of intact spinach chloroplasts (1, 21) resulted in the disappearance of the 683 nm band and a shift in the negative band from 672 nm back to 679 nm. Brody and Nathanson (1) and Nathanson (21) concluded that the 683 and 672 nm bands could be correlated with one species of Chl a and the 679 nm and 665 bands with another.

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Section: And Conclusioncontrasting

confidence: 81%

“…While Philipson and Sauer (23) found that increasing the distance between the samples and the photomultiplier of their C.D. apparatus resulted in change in shape of moderately and heavily scattering samples (whole spinach chloroplasts and Chlorella cells), we, have not found this effect in our studies with Chlorella cells.…”

Section: And Conclusioncontrasting

confidence: 77%

Partial Analysis of the Bands Seen in Circular Dichroism Spectra of Green and Blue-Green Algal Cells and Thylakoids

Nathanson¹,

White²

1977

Plant Physiol.

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“…These results suggest that the effect of 3 mM MgCI2 on the CD spectrum of broken chloroplast suspensions may be a reflection of differential selective light-scattering changes induced by the addition of the salts. Our results do not imply that any of our spectra are free from scattering artifacts but they do underline the necessity of investigating the possibility of scattering artifacts when interpreting CD spectra of particulate material as suggested by Philipson and Sauer [4].…”

Section: Resultscontrasting

confidence: 48%

Cation‐induced changes in the circular dichroism spectrum of chloroplasts

Schooley

1976

FEBS Letters

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“…aL-aR k3 [10] This expression is valid for RII not larger than A. It explains why only large chiral objects with dimensions larger than 1/20 the wavelength of light show measurable differential scattering effects on the CD.…”

Section: Sl -Sr _=nmentioning

confidence: 90%

Circular differential scattering can be an important part of the circular dichroism of macromolecules.

Bustamante¹,

Tinoco²,

Maestre³

1983

Proc. Natl. Acad. Sci. U.S.A.

165

149

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Differential scattering of incident left and right circularly polarized light can be an important contribution to the circular dichroism of macromolecules. In principle both differential absorption and differential scattering of circularly polarized light contribute to circular dichroism, but differential scattering is increasingly important for particles whose dimensions are greater than 1/20th the wavelength of light. The scattering contribution is probably not important for unaggregated proteins and nucleic acids in solution. It can be very important for viruses, membranes, and other protein-nucleic acid complexes. Outside the absorption bands of the scattering, chiral particle, only differential scattering contributes to the circular dichroism. The sign and magnitude of the differential scattering is quantitatively related to the relative orientations and the distances between the scattering units of the particle. The interpretation of the circular differential scattering depends on a simple, classical method. Thus, in understanding a measured circular dichroism, it often will be easier to relate the differential scattering to the structure of a particle (such as a virus) than it is to relate the differential absorption to the structure. CD and optical rotatory dispersion (ORD) studies have been helpful in providing useful knowledge about the structure of biological macromolecules. These methods were limited originally to homogeneous solutions of macromolecules. More recently, they also have been applied to increasingly complex systems such as viruses (1, 2), erythrocytes (3, 4), nucleohistones (5, 6), DNA-polylysine complexes (7,8), DNA aggregates (9), chloroplasts (10), etc. (11). A remarkable common feature of many of these systems was the presence of anomalies in their CD and optical rotatory dispersion spectra. The CD spectra presented: (i) apparent differential absorption of circularly polarized light outside of the absorption bands (the CD signal at long wavelengths was slowly varying but non-zero; this longwavelength "tail" could be positive or negative); (ii) signals sensitive to the distance of the photomultiplier from the sample; and (iii) CD values 1 or 2 orders of magnitude larger than normal. Fig. 1 Recently, a new quantitative understanding of differential scattering of circularly polarized light has been obtained. We were able to relate the difference in scattering efficiency for incident left and right circularly polarized light to the detailed structure of the scattering particle (20-24). We have measured the angular dependence of this circular intensity differential scattering for a helix of known structure and obtained good agreement with theory (25). Thus, we now can explain the "anomalous" behavior of chiral macromolecules and aggregates. We find that the scattering "artifacts" can provide valuable information about the configuration (left-or right-handed) of the component particles.Here we will show how the differential scattering of left and right circularly polarized light ...

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Light-scattering effects on the circular dichroism of chloroplasts

Cited by 43 publications

References 27 publications

Partial Analysis of the Bands Seen in Circular Dichroism Spectra of Green and Blue-Green Algal Cells and Thylakoids

Partial Analysis of the Bands Seen in Circular Dichroism Spectra of Green and Blue-Green Algal Cells and Thylakoids

Cation‐induced changes in the circular dichroism spectrum of chloroplasts

Circular differential scattering can be an important part of the circular dichroism of macromolecules.

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