Plants, higher Membranes

Electron Transport Between Photosystem I and Photosystem II Inhibitors. The interaction between PSI and PSII reaction centers (Fig. 1) depends on the thermodynamically favored transfer of electrons from low redox potential carriers to carriers of higher redox potential. This process serves to communicate reducing equivalents between the two photosystem complexes. Photosynthetic and respiratory membranes of both eukaryotes and prokaryotes contain stmctures that serve to oxidize low potential quinols while reducing high potential metaHoproteins (40). In plant thylakoid membranes, this complex is usually referred to as the cytochrome b /f complex, or plastoquinolplastocyanin oxidoreductase, which oxidizes plastoquinol reduced in PSII and reduces plastocyanin oxidized in PSI (25,41). Some diphenyl ethers, eg, 2,4-dinitrophenyl 2 -iodo-3 -methyl-4 -nitro-6 -isopropylphenyl ether [69311-70-2] (DNP-INT), and the quinone analogues,... 

Kiss, A., Crouchman, S., Ruban, A.V., and Horton, P. 2008. The PsbS protein controls the organisation of the photosystem II antenna in higher plant thylakoid membranes. J. Biol. Chem., 283 3972-3978. 

Krupp Uhde (KU) know-how and technology is based on extensive experience in chlorine production and provides clients with short shutdown periods for the conversion of chlorine plants to membrane technology, low-energy consumption and includes special technologies for higher chlorine quality and hydrogen-free production. 

The performance and characteristics of new RO membranes operating at ultralow pressure (ULP) (7-10 bar) are presented [61]. The total cost comparison based on a 4 kmVday plant revealed that TFC ULP provides about 10% savings over the traditional TFC HR (traditional brackish water RO membrane). Generally, the use of TFC ULP contributes to energy saving, but the capital cost increases due to the higher membrane cost. 

A correlation between the freeze-fracture data, and biochemical characterisation of thylakoid membrane complexes, has been made to produce a hypothetical model of the higher plant photosynthetic membrane, shown in Figure 2. An attempt has been made to indicate whether a polypeptide is extrinsic or intrinsic, and if extrinsic, on which side of the thylakoid it is likely to be located. For intrinsic polypeptides, the number of times they span the membrane is reflected in their width, and the stoichiometry is also indicated, where known. The organisation of the cytochrome b6/f complex is based on the model of O Keefe (7), and of the FNRl on that of Pschorn et al. (8). 

Cobalt is one of twenty-seven known elements essential to humans (28) (see Mineral NUTRIENTS). It is an integral part of the cyanocobalamin [68-19-9] molecule, ie, vitamin B 2> only documented biochemically active cobalt component in humans (29,30) (see Vitamins, VITAMIN Vitamin B 2 is not synthesized by animals or higher plants, rather the primary source is bacterial flora in the digestive system of sheep and cattle (8). Except for humans, nonmminants do not appear to requite cobalt. Humans have between 2 and 5 mg of vitamin B22, and deficiency results in the development of pernicious anemia. The wasting disease in sheep and cattle is known as bush sickness in New Zealand, salt sickness in Florida, pine sickness in Scotland, and coast disease in AustraUa. These are essentially the same symptomatically, and are caused by cobalt deficiency. Symptoms include initial lack of appetite followed by scaliness of skin, lack of coordination, loss of flesh, pale mucous membranes, and retarded growth. The total laboratory synthesis of vitamin B 2 was completed in 65—70 steps over a period of eleven years (31). The complex stmcture was reported by Dorothy Crowfoot-Hodgkin in 1961 (32) for which she was awarded a Nobel prize in 1964. 

Cassettes Cassette is a term used to describe two different cross-flow membrane devices. The less-common design is a usually large stack of membrane separated by a spacer, with flow moving in parallel across the membrane sheets. This variant is sometimes referred to as a flat spiral, since there is some similarity in the way feed and permeate are handled. The more common cassette has long been popular in the pharmaceutical and biotechnical field. It too is a stack of flat-sheet membranes, but the membrane is usually connected so that the feed flows across the membrane elements in series to achieve higher conversion per pass. Their popularity stems from easy direct sc e-up from laboratoiy to plant-scale equipment. Their hmitation is that fluid management is inherently veiy hmited and inefficient. Both types of cassette are veiy compact and capable of automated manufacture. 

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