Bacteriochlorophyll synthesis

Fig. 11. Effect of glycerol on bacteriochlorophyll synthesis. A semianaerobically growing culture of R. capsulata glycerol auxotroph C2 was filtered, washed, and resuspended with (O) or without glycerol ( ). Samples were removed for bacteriochlorophyll determinations at various times. After 135 min, glycerol was added back to half of the deprived culture (A) (N. Klein, thesis).

Chlorophyll. The pathway of chlorophyll synthesis has been elucidated through biochemical genetic studies of Rhodobacter spheroides y]7 118a which produces bacteriochlorophyll, from studies of cyanobacteria,419 420 and from investigations of green algae and higher plants,421 which make chlorophyll a. The first step in the conversion of protoporphyrin IX into chlorophyll is the insertion of Mg2+ (Fig. 24-23, step a). 

Bacteriochlorophyll a is the dominant light-harvesting pigment in purple sulfur bacteria (e.g., Chromatiaceae) and where its synthesis is inhibited by the presence of O2. Similarly, bacteriochlorophyll e has been shown to be indicative of green sulfur bacteria (e.g., Chlorobium phaeovibroides and... 

Which came first—bacteriochlorophyll or chlorophyll Much of the debate centers on the long-held Granick hypothesis (Granick, 1965). The steps to the synthesis of chlorophyll being simpler, it would intuitively be expected to have come first. Recent work supports the notion that bacteriochlorophyll predates chlorophyll (Xiong et al., 2000), refuting the Granick hypothesis, so the IR thermotaxis hypothesis remains tenable. 

J Aagaard and W Sistrom (1972) Control of synthesis of reaction center bacteriochlorophyll in photosynhetic bacteria. Photochem Photobiol 15 209-225... 

Chlorophyll. The pathway of chlorophyll synthesis has been elucidated through biochemical genetic studies of Rhodobacter spheroidesd which produces bacteriochlorophyll, from studies of cyanobacte-... 

Progress in the synthesis of chlorophylls and bacteriochlorophylls (di- and tetra-hydro porphyrins) has been relatively slow, but the recent isolation of new reduced porphyrins, such as the physiologically active marine pigment bonellin" and sirohydrochlorin (an intermediate in vitamin B12 biosynthesis) is likely to stimulate attempts to synthesize these compounds directly from partially reduced open chain precursors rather than by reduction of preformed porphyrins (see Section 11). Considerable progress has already been made in the development of new methods for synthesizing the partially reduced bile pigments (Section 9). 

N. Risch and H. Reich, Partial synthesis of a stereochemically pure bacteriochlorophyll-d," Te-... 

Because of its long-wavelength absorption close to 800 nm, naturally occurring bacteriochlorophylls are ideal candidates for PDT. However, due to their unstable nature, synthesis of stable bacteriochlorins has been a challenge for porphyrin chemists worldwide. 

Most of the naturally occurring bacteriochlorins (e.g., 132) have absorptions between 760 and 780 nm and are extremely sensitive to oxidation, resulting in a rapid transformation into the chlorin state 133 which generally has an absorption maximum at or below 660 nm (Scheme 37). Furthermore, if a laser is used to excite the bacteriochlorin in vivo, oxidation may result in the formation of a new chromophore absorbing outside the laser window, reducing its photodynamic efficacy. Due to the desirable photophysical properties of bacteriochlorins, there has been increasing interest in the synthesis of stable bacteriochlorins from bacteriochlorophyll a or other similar tetrapyrrolic systems. 

The primary photochemistry in bacterial reaction centers (RCs) involves the light-induced electron transfer from a primary electron donor, D (a bacteriochlorophyll dimer), through a series of electron acceptors (a bacteriopheophytin, ( )a, and a primary quinone, Q ) to a secondary quinone acceptor, Qb (reviewed in ref. 1). The charge transfer is accompanied by protonation of the quinones which is the first step in proton translocation across the bacterial membrane. The electrochemical proton gradient formed across the membrane provides the driving force for ATP synthesis (reviewed in ref. 2). Thus, electron transfer can be viewed as a mechanism for setting up the system to carry out the physiologically important function of proton translocation (2). 

THE SYNTHESIS OF RADIOACTIVE PHOTOAFFINITY LABELS CONTAINING MAGNESIUM TETRAPYRROLE INTERMEDIATES OF CHLOROPHYLL AND BACTERIOCHLOROPHYLL BIOSYNTHESIS. 

A. Control of Heme and Bacteriochlorophyll (BCHL) Synthesis in Rhodopseudomonas spheroides... 

Aagard J and Sistrom WR. Control of synthesis of reaction centre bacteriochlorophyll in photosynthetic bacteria. Photochem. Photobiol. 1972 15 209-225. 

Kureishi Y, Tamiald H (1998) Synthesis and self-aggregation of zinc 20-halochlorins as a model for bacteriochlorophylls c/d. J Porphyrins Phthalocyanines 2(2) 159—169... 

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