Carotenoid Molecules Research Articles

Orientation of chromophores in reaction centers of Rhodopseudomonas sphaeroides: A photoselection study

The relative orientation of the pigments of reaction centers from Rhodopseudomonas sphaeroides has been studied by the photoselection technique. A high value (+0.45) of p = (ΔA V − ΔA H ) (ΔA V + ΔA H ) is obtained when exciting and observing within the 870 nm band which is contradictory to the results of Mar and Gingras (Mar, T. and Gingras, G. (1976) Biochim. Biophys. Acta 440, 609–621) and Shuvalov et al. (Shuvalov, V.A., Asadov, A.A. and Krakhmaleva, I.N. (1977) FEBS Lett. 76, 240–245). It is shown that the low values of p obtained by both groups were erroneous due to excitation conditions. Analysis of the polarization of light-induced changes when exciting with polarized light in single transitions (spheroiden band and bacteriopheophytin Q x bands) enable us to propose a possible arrangement of the pigments within the reaction center. It is concluded that the 870 nm band corresponds to a single transition and is one of the two bands of the primary electron donor ( P-870). The second band of the bacteriochlorophyll dimer is centred at 805 nm. The Q y transitions of the molecules constituting the bacteriochlorophyll dimer are nearly parallel (angle less than 25°). The two bacteriopheophytin molecules present slightly different absorption spectra in the near infra-red. Both bacteriopheophytin absorption bands are subject to a small shift under illumination. The angle between the Q y bacteriopheophytin transitions is 55° or 125°. Both Q y transitions are nearly perpendicular to the 870 nm absorption band. Finally, the carotenoid molecules makes an angle greater than 70° with the 870 nm band and the other bacteriochlorophyll molecules.

Isolation and characterization of an organic solvent soluble polypeptide component from photoreceptor complexes of Rhodospirillum rubrum

An organic solvent soluble polypeptide has been isolated from photoreceptor complexes and chromatophores of Rhodospirillum rubrum. After extraction of the protein from lyophilized samples with 1:1 chloroform-methanol, it was purified by column chromatography. Its isoelectric point determined by isoelectric focusing was 7.10. When analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the purified polypeptide ran as a single band of an apparent molecular weight of 12 000. However, according to amino acid analysis, the minimal molecular weight based on one histidine residue per polypeptide is 19 000. The polypeptide contains no cysteine and no tyrosine. Amino acid analysis indicated that three methionines were present per histidine residue and cyanogen bromide cleavage gave four smaller peptides which were isolated by two-dimensional electrophoresis and chromatography. Spectroscopic analysis indicated the presence of three tryptophan residues per histidine and N-bromosuccinamide cleavage also gave four smaller peptides which could be isolated by two-dimensional electrophoresis and chromatography. The C-terminal amino acid was shown to be glycine by two methods, while the N-terminal amino acid appears to be blocked. The organic solvent soluble polypeptide accounts for approximately 50% of the chromatophore protein and seems to bind the antenna bacteriochlorophyll and carotenoid molecules. Using this procedure, organic solvent soluble polypeptides were isolated from several photosynthetic bacteria and were found to have substantially different amino acid contents.

The Light-harvesting Chlorophyll a/b-Protein Complex of Chlamydomonas reinhardii

The molecular organization of chlorophyll in Chlamydomonas reinhardii has been shown to be essentially similar to that in higher plants. Some 50% of the chlorophyll in Chlamydomonas reinhardii chloroplast membranes has been shown to be located in a chlorophyll a/b-protein complex. The complex was isolated in a homogeneous form by hydroxylapatite chromatography of sodium dodecyl sulfate extracts of the chloroplast membranes. Its absorption spectrum exhibits two maxima in the red region at 670 and 652 nm due to the presence of equimolar quantities of chlorophylls a and b in the complex. Preparations of the chlorophyll-protein also contain some of each of the carotenoids observed in the intact chloroplast membrane, but not in the same proportions. The native complex (S value = 2.3S) exhibits a molecular weight of 28,000 +/- 2,000 on calibrated sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, on the basis of its amino acid composition and other data a more probable molecular weight of about 35,000 was calculated. Each 35,000 dalton unit contains three chlorophyll a and three chlorophyll b molecules, and on the average one carotenoid molecule conjugated with probably a single polypeptide of 29,000 daltons. Comparison of spectral and biochemical characteristics demonstrates that this algal chlorophyll-protein is homologous to the previously described major light-harvesting chlorophyll a/b-protein of higher plants. It is anticipated that the Chlamydomonas complex functions solely in a light-harvesting capacity in analogy to the function determined for the higher plant component.

The state of chlorophyll and carotenoid in vivo II — A linear dichroism study of pigment orientation in photosynthetic bacteria

Summary Similar linear dichroism (LD) spectra have been obtained for oriented samples prepared from photosynthetic bacteria containing either parallel lamellae (Rhodopseudomonas palustris) or spherical chromatophores (Rhodopseudomonas spheroides) in the spectral region from 300 to 1,000 nm. Our data indicate that the far-red QY transition moment of the bacteriochlorophyll (BChl) molecules is oriented nearly parallel to the plane of the membrane, and that the QX transition moment (590 nm) is tilted out of the membrane alone at an angle greater than 45°. The transition moment of the carotenoid molecules is shown to point out of the membrane plane. The LD spectrum of the R-26 mutant of R. spheroides allows the assign ment of the polarization direction of the main BChl transitions in the Soret region.

Polarized light spectroscopy of photosynthetic membranes in magneto-oriented whole cells and chloroplasts. Fluorescence and dichroism

1. The wavelength dependence of the fluorescence polarization (FP) ratio and dichroism has been studied with magneto-oriented (10–13 kG) whole cells of Chlorella pyrenoidosa, Scenedesmus obliquus, Euglena gracilis and spinach chloroplasts suspended in their aqueous growth media (or Tris-buffered sucrose solution in the case of the chloroplasts) under physiological conditions. The FP ratio is defined as the fluorescence intensity polarized parallel divided by the intensity polarized perpendicular to the membrane planes. 2. The FP ratio is typically in the range of 1.2–1.9 in Chlorella, 1.20–1.25 in Scenedesmus and 1.4–1.5 in spinach chloroplasts at fluorescence wavelengths above 690 nm. Below 690 nm the FP ratio decreases steadily with decreasing wavelength and may be as low as approx. 1.05 at 660 nm. These results are interpreted in terms of the orientation of the Q y transition moment vectors of the different spectroscopic forms of chlorophyll. For the chlorophyll a 680 form these vectors are inclined at angles of 30° or less (in Chlorella) with respect to the membrane planes, while the shorter wavelength chlorophyll a 670 forms appear to be not nearly as well oriented. 3. The Euglena fluorescence peak is red shifted to 714 nm (in the other algae and chloroplasts it is situated at 685 nm) and the FP ratio is approx. 1.20 in the 720–730 nm region and decreases with decreasing wavelength below 720 nm and is only 1.05 at 690 nm. This wavelength dependence is in good qualitative agreement with the fluorescence microscope studies of single chloroplasts of Euglena by Olson, R. A., Butler, W. H. and Jennings, W. H. ((1961) Biochim. Biophys. Acta, 54, 615–617). 4. By means of a model calculation it is shown that the high FP ratios observed with Chlorella are entirely consistent with the low values of the degree of polarization (0.01–0.06) determined by previous workers with unoriented cell suspensions. 5. The influence of reabsorption and the resulting distortion in the wavelength dependence of the FP ratio are described. The possibility that the fluorescence is polarized by scattering artifacts, rather than being a result of the intrinsic orientation of chlorophyll, is considered. 6. Linear dichroism studies with Chlorella and spinach chloroplasts confirm the orientation of the Q y transition moment vectors deduced from the FP ratio. Furthermore, it appears that the porphyrin rings are tilted out of the membrane plane and that the carotenoid molecules tend to lie with their long axes in the lamellar plane. 7. In Euglena, dichroism studies indicate that chlorophyll a 680 is unoriented, while chlorophyll a 695 appears to be oriented similar to chlorophyll a 680 in Chlorella or spinach chloroplasts, a result which is also in accord with the measured FP ratio of Euglena. 8. The possibility that the magnetic field gives rise to the reorientation of individual chlorophyll molecules is shown to be highly unlikely.

Orientation of pigments and structural proteins in the photosynthetic membrane of spinach chloroplasts: A linear dichroism study

1. The rotation of the plane of polarization, when monochromatic light traverses an anisotropic sample, is proportional to the linear dichroism ( ΔA) of this sample. A sensitive technique of measurement of this rotation (sensitivity corresponding to 2·10 −5 absorbance unit for ΔA) has been applied to mechanically or magnetically oriented chloroplasts (800-185 nm). The contribution of artifacts encountered in linear dichroism measurements (textural dichroism, selective polarized scattering, selective polarized reflection) is discussed and is shown to be negligible. 2. A high degree of orientation of the pigments with respect to the normal to the plane of the lamellae has been detected. By comparing linear dichroism and absorption data, this orientation is analyzed in terms of the value of the angle ϕ between the normal and the directions of the transition dipole moments. 3. The directions of y polarized transitions of Ca-680 and longer wavelength forms of chlorophyll a lie close to, or in the lamellar plane ( ϕ>60–65°), Ca-670 is less oriented or oriented with ϕ slightly >55°. 4. The negative dichroism in the Soret band of chlorophyll a implies that the directions of x polarized transitions are tilted out of the membrane plane ( ϕ⋍48°) 5. Chlorophyll b molecules are oriented in a similar way. 6. Carotenoid molecules lie nearly parallel to the lamellar plane. 7. For structural proteins in intact thylakoid membranes an orientation of tryptophan residues is detected and the 220-185-nm signals are tentatively assigned to an orientation of α-helical regions parallel to the membrane plane.

Konzentration einiger Lipide in den Chloroplasten von Zea mays und Antirrhinum majus / Concentration of Some Lipids in the Chloroplasts of Zea mays and Antirrhinum ma jus

Stroma-containing chloroplasts from Zea mays and Antirrhinum majus were isolated in aqueous medium. The average dry weight of chloroplasts from Zea mays is 27·10-12 g, that of Antirrhinum majus 30·10-12 g. Water freed chloroplasts consist up to 49 or 45 percent respectively of lamellar system. The lipid content of the lamellar system of Zea mays is 49 percent, that of Antirrhinum majus 45 percent. A chloroplast of Zea mays contains on the average 920·106 chlorophyll molecules, 220·106 carotenoid molecules, 2000·106 molecules of galactolipids, 190·106 molecules of sulpholipid, 260·106 phosphatide molecules and 64·106 molecules of lipophilic quinones. In addition to phosphatidylglycerol also phosphatidylinositol and phosphatidylcholine were found. It is very probable that besides vitamin K1 the homologeous compound lacking one methylgroup is present in the chloroplasts. In contrast to the literature only 62 percent of the total leaf galactolipids are found in the chloroplasts.

Die Gr��e der photosynthetischen Einheit und ihre Variabilit�t

Even under unsaturated conditions of light a yellow green Chlorella mutant shows a higher photosynthetic efficiency than the normal form on the basis of chlorophyll. This difference in photosynthesis is not influenced by irradiation with red light although in the mutant the ratio carotenoids:chlorophyll is four times higher than in the normal green cells. Therefore we conclude that in the mutant the efficiency of excitation transfer from carotenoids to chlorophyll is reduced. As a result of the smaller photosynthetic units fewer carotenoid molecules are in the vicinity of the chlorophyll. The average increase in the distance between the molecules of the two pigment groups results in the reduction of the excitation transfer to chlorophyll.

Purification and properties of crustacyanin

Crustacyanin, the blue carapace pigment of the common lobster Homarus gammarus (L.), has been purified and crystallized. This chromoprotein has a minimum molecular weight of 36 000 based on the content of the carotenoid prosthetic group astaxanthin. The molecular weight in gel filtration measurements is about 650 000, corresponding to some 18 molecules of astaxanthin per molecule of protein. Crustacyanin, on dialysis against water, dissociates into particles of about 35 000 molecular weight, each apparently bearing one molecule of carotenoid. The dissociation is accompanied by a shift in the principal maximum of the absorption spectrum from 633 to 595 nm and is reversed upon addition of salt. Reversible dissociation also occurs in the presence of 3 M urea, 1 M potassium thiocyanate, 10% (v/v) dioxan or 10% (v/v) acetone. When the carotenoid is removed from crustacyanin with acetone, the resul­tant apoprotein has a mean molecular weight of about 20 000. It may be resolved by starch gel electrophoresis into several components of which two predominate. Crustacyanin, indistinguishable from the native material, can be reconstituted from apoprotein and carotenoid. Evidence from the behaviour of crustacyanin and its apoprotein at surfaces indicates that the tertiary and quaternary structures of the native protein are stabilized by the carotenoid. It is suggested that the quaternary structure of crustacyanin is induced by an interaction of the carotenoid molecules of the subunits, which in turn causes a change in configuration of the protein favourable to aggregation. The result is a micelle-like structure with a hydrophobic carotenoid core.

CHARACTERISTICS OF PIGMENT‐PROTEIN COMPLEXES IN NORMAL AND CHLOROPLAST MUTANT LEAVES*

Abstract— The structural stability of chloroplasts was characterized by the proportion of leaf pigments present in the lipoprotein complex.Free or loosely protein‐bound pigments were separated by means of petroleum ether extraction of leaves. In normal barley seedlings equilibrium constants of 0.66 were found for carotenoid and 005 for chlorophyll‐protein complexes.In the pigment‐protein complex two types of bonding were distinguished which are based most probably on different number and/or energy of hydrogen bonds. The weaker bonding could be disrupted by heat denaturation (50–70°C), the stronger one could by polar solvents. Heat denaturation affects about 40 per cent of the carotenoid, 52 per cent of the chlorophyll‐a and 34 per cent of the chlorophyll‐b complexes.Chloroplast mutant leaves with abnormal carotenoid synthesis show characteristic differences in the stability of their pigment‐protein complex.It is concluded that the chlorophyll and carotenoid molecules are present in the chloroplasts in different physical states which may represent different functional forms.

Lipidsof Arum maculatumspadices

Chloroplasts, concerned with photosynthesis, contain another quinone first discovered by Kofler (1946) (and often referred to as koflerquinone: see also Kofleret al. 1959a) and rediscovered by Crane (1959) and designated Q254or plastoquinone (II, figure 1). So far, only one plastoquinone has been fully characterized but there appear to be others in nature (Crane 1961; Kegel, Henninger & Crane 1962). Plastoquinone is 2,3-dimethyl-l,4-benzoquinone with a solanesyl side chain. Solanesol is a monohydric alcohol C45H73OH, discovered in tobacco by Rowland, Latimer & Giles (1956) and characterized (III, figure 1) later by Eriksonet al. (1959) and by Kofleret al. (1959b). Ubiquinones (Mortonet al. 1958, Wolfet al. 1958; Shunket al. 1958) are fully substituted 1,4-benzoquinones with two methoxyl substituents in positions 2 and 3, one methyl and one polyisoprenoid substituent. When the latter contains 30, 35, 40, 45 or 50 carbon atoms the compound is designated ubiquinone (30), ubiquinone (35), etc. (Morton et al. 1958; Gloor 1958). The group of workers led by D. E. Green at Madison refers to these compounds as coenzymesQand uses the notation coenzymeQ6if, for example, the polyisoprenoid side chain contains 6 five-carbon units or coenzymeQ10if there is a C50side chain made up of 10 five-carbon units (Lester, Crane & Hatefi 1958). According to the report of the International Commission on Enzymes (1961), ubiquinone (50) or coenzymeQ10should now be described as ubiquinone10orUQ10, the numerical suffix indicating the number of isoprene units. Two heterocyclic compounds, isomeric respectively with plastoquinone and ubiquinone, are also known. Solanachromene (IV, figure 1) (Rowland 1958) and ubichromenol (V, figure 1) have an ethylenic linkage in a heterocyclic ring and a phenolic hydroxyl group in addition to a polyisoprenoid chain. Ubichromenol (50), related to ubiquinone (50), was isolated from human kidney and fully characterized (Laidman, Morton, Paterson & Pennock 1959, 1960). In fractionating kidney unsaponifiable matter the first aim was to isolate and purify ubiquinone, a-toeopherol (VI, figure 1) and ubichromenol. Later, other fractions were studied, and from them a new polyisoprenoid alcohol with 100 carbon atoms was isolated and designated dolichol (Gr. dolichos) because of its very long aliphatic chain (Pennock, Hemming & Morton i960). Burgos, Hemming, Pennock & Morton (1962) have now shown that its formula is C100H163OH with 19 isoprene units. The hydrocarbon squalene, C30H50is now recognized to be an intermediate in the biosynthesis of sterols. The squalene molecule is symmetrical; two farnesyl (pyrophosphate) residues having been linked tail to tail. The carotenoid molecules (with 40 carbon atoms) are also capable of symmetry, thus both lycopene andβ-carotene are made up of identical halves. A 40-carbon analogue of squalene, namely, lycopersene (see table 1) has been synthesized but with one exception it has not been found to occur naturally (Davies 1962). Evidence of the presence of two related substances, phytoene C40H64and phytofluene C40H62, is however occasionally obtained. In all likelihood these compounds are biosynthetic precursors of carotenoids (Goodwin 1955).

Chloroplast development in Ochromonas danica.

When dark-grown cells of Ochromonas danica are placed in the light, the amount of chlorophyll a per cell increases 82-fold; the content of carotenoid pigment, 24-fold. Concomitantly with this increase in chlorophyll and carotenoid pigment, the small proplastid of dark-grown cells develops into a large lamellate chloroplast. During the first 12 hours in the light, vesicles appear within the loose clusters of dense chloroplast granules, enlarge, align themselves into rows (plates in three dimensions), and fuse into discs. Double discs may form from the more or less simultaneous fusion of two adjacent plates of vesicles or by the addition of vesicles to an already formed single disc. Three-disc bands arise by the addition of a disc to an already formed two-disc band through the approach and fusion of more vesicles. After 24 hours in the light, most of the chloroplast bands contain three discs, but the chloroplasts are still small. After 48 hours in the light, almost all the cells contain full-sized chloroplasts with a full complement of three-disc bands. However, at this time the amount of chlorophyll a and carotenoid pigment is only one-half of maximum. During the next 3 days in the light, as the number of chlorophyll and carotenoid molecules per chloroplast approximately doubles, there is a compression of the discs in each band (from 180 to 130 A) and a precise alignment of their membranes. Changes also occur in the nucleus when dark-grown cells are placed in the light. There is an increase in the number of small nucleolar bodies, many of which lie directly against the nuclear envelope, and in a few cells a dense mass of granules is seen between the two membranes of the nuclear envelope.

Molecular orientation in quantasomes: I. Electric dichroism and electric birefringence of quantasomes from spinach chloroplasts

Quantasomes (lamella subunits) isolated from spinach chloroplasts have been shown to exhibit both intrinsic electric birefringence (Kerr effect) and intrinsic electric dichroism. Measurements of Kerr constants and of rotational relaxation times suggest that the birefringence arises primarily from the proteins in the preparations. The smallest particles studied give rise to rotational relaxation times in the range 20 to 200 μsec. The shortest times may be associated with a particle having a permanent dipole moment. The spherical chromatophore subunits from Rhodospirillum rubrum do not exhibit detectable electric birefringence, as measured in the apparatus of this study. The dichroic ratio spectrum from 330 to 730 mμ of spinach quantasomes has been determined by electric dichroism measurements. The measured dichroic ratios of 1·03 to 1·10 throughout most of the spectrum suggest that the chlorophyll and carotenoid molecules in the quantasome are largely unoriented. A pronounced peak occurs in the dichroic ratio spectrum at 695 mμ, about 17 mμ to the long wavelength side of the strong chlorophyll a absorption maximum in this region. The dichroic ratio increment is at least five times greater at 695 than at 678 mμ. The dichroism anomaly is interpreted as resulting from a small fraction (∼5%) of the chlorophyll a which is strongly oriented at a particular site (the quantatrope) in the quantasome. It is suggested that an oriented cytochrome and one or more bound acceptor molecules are present at this site as well. A mechanism is postulated whereby electronic excitation energy resulting from the absorption of light by the pigments of the quantasome is converted at the quantatrope to chemical potential associated with electron transport processes.

THE INFILTRATION OF CAROTENOIDS INTO HUMAN ATHEROMAS AND XANTHOMAS

Excerpt Carotenoids are lipids which are usually colored either red or yellow. In figure 1, the distinguishing characteristics of the carotenoid molecule are illustrated by the specific carotenoid ...

Molecular Structure and Absorption Spectra of Carotenoids

An assemblage of π-electrons in the chain of carotenoid molecules is discussed, according to Tomonaga's method, on the basis of an assumption that the electrons are kept in a pipe whose length is equal to the chain length of conjugated double bonds. The spin degrees of freedom of electrons are taken into account though Tomonaga disregarded them. The one-dimensional potential of two-electron forces is assumed to be given by an average of the Coulomb repulsive potential over a section of the pipe. The calculated values of absorption maxima are in good agreement with experiment for carotenoids. The adequacy of the method is discussed.