Spectroscopic properties, chlorophylls

Structures and Chemical and Spectroscopic Properties of Major Chlorophylls and Bacteriochlorophylls... 

Other spectroscopic properties such as nuclear magnetic resonance (NMR), mass spectrometry (MS), infra-red (IR), and circular dichroism (CD) spectra of chlorophyll compounds and derivatives have been valuable tools for structural elucidation. - ... 

Nonomnra, Y. et al.. Spectroscopic properties of chlorophylls and their derivatives inflnence of molecnlar stmctnre on the electronic state, Chem. Phys., 220, 155, 1997. Blairkenship, R.E., Identification of key step in the biosynthetic pathway of hacteri-ochlorophyU c and its implications for other known and nirknown green sulfur bacteria, J. Bacterial., 186, 5187, 2004. 

Nonomura, Y. et al., Spectroscopic properties of chlorophylls and their derivatives. Influence of molecular structure on the electronic state, Chem. Phys., 220, 155, 1997. 

Since chlorophylls have distinct spectroscopic properties, absorption or fluorescence spectrophotometry can be employed for their identification and quantification (118). Usually wavelengths between 430 and 440 nm and 645 and 660 nm, respectively (93,115), are used for spec-trophotometric detection. With spectrophotometric detectors, detection limits of approximately 80 ng chlorophyll (119) and 1 ng chlorophyll (120), respectively, can be achieved. Fluorescence... 

Miscellaneous Physical Chemistry. Various aspects of the physical chemistry of /3-carotene and related carotenoids have been reported, including several theoretical calculations related to spectroscopic properties,investigations of carotenoid triplet states and triplet energies,studies of carotenoid radical ions, and examination of electron-transfer reactions between carotenoids and chlorophyll Two reviews offer brief surveys of the year s literature on the photochemistry of... 

Wiemken V and Bachofen R (1984) Probing the smallest functional unit of the reaction center of Rhodospirillum rubrum G-9 with proteinoses. FEBS Lett 166 155-159 Williams JC, Alden RG, Murchison HA, Peloquin JM, Woodbury NW and Allen IP (1992) Effects of mutations near the bacteriochlorophylls in reaction centers from Rhodobacter sphaeroides. Biochemistry 31 11029-11037 Yeates TO, Komiya H, Chirino A, Rees DC, Allen IP and Feher G (1988) Structure of the reaction center from Rhodobacter sphaeroides R-26 and 2.4.1 Protein-cofactor bacterio-chlorophyll bacteriopheophytin and carotenoid interactions. Proc Natl Acad Sci USA 85 7993-7997 Zinth W, Knapp EW, Fischer SF, Kaiser W, Deisenhofer J and Michel H (1985) Correlation of structural and spectroscopic properties of a photo synthetic reaction center. Chem Phys Lett 119 1 ... 

The chlorophyll-protein (CP) and polypeptide pattern of PSII complexes were determined by two dimensional gel electrophoresis. Prominent polypeptides could be attributed to the biliprotein subunits of AP (14> 16 kDa) and PC (15f 18 kDa) and at least four phycobilisome-linker polypeptides (29f 31, 34 and 120 kDa. The Chl-proteins were characterized by apoproteins of 47 (CPIIa,b) and 41 (CPIIc) kDa. CP Ila and b were similar in their spectroscopic properties and showed fluorescence maxima at 685 nm and shoulders at 693 nm, whilst CP lie exhibited only one peak at 686 nm, when excited at 445 nm. Thus the isolated Chl-proteins had similar emission properties as the in situ" PSII antennae. 

In contrast, de-esterification of phytol in the chlorophyll molecule does not affect the chromophore stmcture, so the electron adsorption spectmm is unaltered. Thus, chlorophyUides and pheophorbides have the same spectroscopic properties as then-respective precursors, chlorophylls and pheophytins. The same is tme of some of the reactions that affect the isocyclic ring, such as epimerization and decarbometh-oxylation on C-13. ... 

Primary allomerizalion reactions that give rise to hydroxy- or methoxy-chlorophylls also do not affect the spectroscopic properties. In contrast, other oxidative reactions involving opening of the isocyclic ring or the formation of a lactone ring do cause important changes in the electron absorption spectmm. 

Direct spectroscopic measurements of absorptions could provide substantial and much-needed complimentary information on the properties of BLMs. Difficulties of spectroscopic techniques lie in the extreme thinness of the BLM absorbances of relatively few molecules need to be determined. We have overcome this difficulty by Intracavity Laser Absorption Spectroscopic (ICLAS) measurements. Absorbances in ICLAS are determined as intracavity optical losses (2JI). Sensitivity enhancements originate in the multipass, threshold and mode competition effects. Enhancement factor as high as 106 has be en reported for species whose absorbances are narrow compared to spectral profile of the laser ( 10). The enhancement factor for broad-band absorbers, used in our work, is much smaller. Thus, for BLM-incorporated chlorophyll-a, we observed an enhancement factor of 10 and reported sensitivities for absorbances in the order of lO- (24). 

The chemical nature of P-700 is difficult to establish. The absorption bleachings correspond approximately to the peaks of Chi a. which appears to be virtually the only tetrapyrrolic pigment in purified PS I particles. It has thus been assumed that P-700 is Chi a bound to a protein. A few recent results, however, may require this hypothesis to be refined. An examination of the spectroscopic and redox properties of P-700 led Wasielewski et al. [13] to propose that P-700 could be the enol form of Chi a where enolization was of the keto ester on ring V. This has not been confirmed by chemical extraction. Extraction experiments, however, have evidenced two other chlorophyll derivatives. A species named Chl-RC I has been isolated from PS I, at a nearly 1/1 molar ratio with P-700 and its structure shown to be a chlorinated derivative. It is not yet clear whether Chl-RC I is a native constituent of PS I or an extraction artefact. Chl-RC I has not been obtained in a recent chemical analysis by HPLC, which instead revealed two Chi a per P-700 [14]. 

Covalently linked dimers of both chlorophyll a and pyrochlorophyll a have been prepared, which mimic the spectroscopic and redox properties of P700. The two chlorophylls are joined in each case at their propionic acid side chains via an ethylene glycol diester linkage. The orientation of the chlorophyll macrocycles with respect to one another (Figs. 11 and 12) and consequently their electronic properties depend strongly on the solvent. The structure of most interest is the folded one (Fig. 11) because of its similarity to the photoactive dimer in photosystem I. 

SPECTROSCOPIC AND ORIENTATIONAL PROPERTIES OF CHLOROPHYLLS a AND b IN LIPID MEMBRANES... 

Spectroscopic and Orientational Properties of Chlorophylls a and b in Lipid Membranes 337 M. van Gurp, G. van Ginkel, Y,K, Levine... 

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