Spinach composition

More nsnal vegetables were stndied by Nnntila et al. [358] who characterized onions and spinach for the phenolic composition, with and without previous hydrolysis. The authors performed the simultaneous determination of phenolic acids, flavonols, flavones glycosides, and cathechins. Fignre 19.9 reprodnces the separation obtained for the standard mixture in this study. 

Eppendorfer, W. H., Bille, S. W. (1996). Free and total amino acid composition of edible parts of beans, kale, spinach, cauliflower and potatoes as influenced by nitrogen fertilisation and phosphorus and potassium deficiency. Journal ofthe Science of Food and Agriculture, 71,449M58. 

But my discussion of rat acrobatics isn t intended to turn people into blueberry-guzzling fiends. Eating blueberries won t save you dietary sinners. What matters most is the overall diet composition. In the rat study strawberry and spinach extract also produced improvements in memory, although those foods didn t have the same effect on balance and coordination as blueberries did. Still, the message is that fruits and vegetables have antiaging properties. As we are now learning, they harbor all kinds of useful chemicals. Like the B vitamin commonly known as folic acid. 

Spin-spin interaction. See NMR spectroscopy Spinach (Spinacia oleracea) composition of 31... 

Approximate Composition of Photosynthetic Units in a Spinach Chloroplast3... 

The values for the molecular weight of plant ferredoxins reported by different investigators are not in agreement. Appella and San Pietro 4) reported a molecular weight of 17,000 for spinach ferredoxin, based on an S2o,w of 1.36 and a diffusion coefficient of 6.6 X 10 7 cm2/sec. The partial specific volume was assumed to be 0.71. A calculation by the writer for the minimal molecular weight of spinach ferredoxin from available amino acid composition data Fry and San Pietro (47)) and the assumption of six cysteine residues per mole gave a value of 13,000. Arnon (5)... 

Table 6 shows that spinach ferredoxin contains all the amino acids in bacterial ferredoxin plus one residue each of methionine, histidine, and tryptophan. Like bacterial ferredoxin, spinach ferredoxin has an abundance of acidic and a paucity of basic amino acids. Hill and San Pietro (53) found that parsley ferredoxin is similar to the one from spinach in composition and spectra, but differs in lacking tryptophan. Little is known of the structure of plant ferredoxin. It is known that spinach ferredoxin is a single peptide chain with alanine at both ends (Tsugita et al. (103)). 

Table 6. Amino acid composition of some bacterial and plant ferredoxins C. pasteurianum C. acidi-urici C. tetanomorphum C. butyric-urn C. cylindrospontm M. omelianskii Spinach... 

DEAE-cellulose. A paucity of tyrosine residue may reflect the unusual low absorbance of adrenodoxin in the region of 280 mp. In general, the amino acid composition of adrenodoxin is similar to that of spinach ferredoxin as compared in Table 3, but it considerably differs from that of Cl. pasteurianum ferredoxin which lacks amino acid residues of methionine, tryptophan, histidine, arginine, and leucine. 

Lambeth, V.N., et al. 1969. Detinning by canned spinach as related to oxalic acid, nitrates and mineral composition. Food Technol. 23, no. 6 132-134. 

The N-terminal amino acid sequence of both of these polypeptides has been determined [11,12]. Polypeptides of 7, 6.5, 5.5 and 5 kDa have been shown to be associated with a spinach PS II preparation [13]. The three larger polypeptides are hydrophobic, as shown by partitioning in Triton X-114, and are presumed to be intrinsic membrane proteins. The 5 kDa polypeptide is hydrophilic and therefore presumably peripheral to the core complex. This polypeptide has been purified and its amino acid composition determined [13]. 

DSC has been used to study the individual protein components of biological membranes of relatively simply protein composition and the interaction of several of these components with lipids and with other proteins. The red blood cell membrane, which has been most intensively studied, exhibits five discrete protein transitions, each of which has been assigned to a specific membrane protein. The response of each of these thermal transitions to variations in temperature and pH as well as to treatment with proteases, phospholipases, specific labelling reagents, and modifiers and inhibitors of selected membrane activities, has provided much useful information on the interactions and functions of these components in the intact erythrocyte membrane (46-49). Similar approaches have been applied to the bovine rod outer segment membrane (50) and to the spinach chloroplast thylakoid membrane (51). 

Larrson UK, Sundby C and Andersson B. (1987). Characterization of two different subpopulations of spinach light-harvesting chlorophyll a-i-protein complex (LHC-II) polypeptide composition, phosphorylation pattern and association with photosystem-II. 

Melis A. and Anderson J.M. (1983). Structural and functional organization of the photosystems in spinach chloroplasts antenna size, relative electron transport capacity, and chlorophyll composition. Biochim. Biophys. Acta 724, 473-484. 

As seen in Fig. 3 (A), the 77-K absorption spectra ofLHC 1 -680 and LHC 1-730 differ noticeably from each other. LHC 1-730 has ared absorption band at 677 nm and a distinct shoulder at 710 nm. LHC 1-680 shows a major red band at 674 nm and lacks the long-wavelength shoulder, but shows a relatively higher Chi b absorption at 645 nm. Some of the differences in the blue region may reflect differences in the carotenoid composition in the two complexes. As with the spinach LHC-I fractions, the low-temperature fluorescence spectra ofLHC 1-680 and LHC 1-730 are dramatically different, with the former emitting predominantly at 675 nm and the latter at 730 nm [see Fig. 3 (B)]. 

Fig. 8. (A) A composite model constructed for the native photosystem I composed of the CCI with the new model for a PS-1 reaction-center monomer containing both the subunit polypeptides and the core-antenna Chl-a molecules plus the peripheral LHC I proteins. (B) The Jansson model. (C) The Fromme model. (A) adapted from Boekema, Wynn and Malkin (1990) The structure of spinach photosystem I studied by electron microscopy. Biochim Biophys Acta 1017 55 and Schubert, Klukas, Kraud, Saenger, Fromme and Witt (1997) Photosystem I of Synechococcus elongates at 4 A resolution Comprehensive structure analysis. J Mol Biol 272 756 (B) from Jansson (1994) The light-harvesting chtorophyll alb-binding proteins. Biochim Biophys Acta 1184 15. (C) from Fromme (1996) Structure and function of photosystem I. Current Opinion in Structural Biology 6 474.

Fig. 6. (A) Effect of composition of a binary soivent mixture on the apparent Chi a Aotal chlorophyli moiar ratio in extracts of spinach leaf tissue (0) and chloroplasts ( ). (B) relationship between the Chi a/Chl a molar ratio and the Chi a/P700 molar ratio for a number of P700-enriched subchloroplast particles by chloroform extraction (o) and by acetone extraction ( ). The solid line ciosest to the open circles is for Chi aVP700=1 and that nearest the filled circles for Chi aVP700= 2. See text for details. Figure source (A) Watanabe, Kobayashi, Maeda, Oba, Yoshida, Van de Meent and Amesz (1992) Function of the C13 -epimer chlorophylls in type I photosystem reaction centers. In N Murata (ed) Research In Photosynthesis, Vol III 4. Kluwer Acad PubI (B) Maeda, Watanabe, Kobayashi and Ikegami (1992) Presence of two chlorophyll a molecules at the core of photosystem I. Biochim Biophys Acta 1099 78.

Fig. 2. (A) A model for b/in chloroplast thylakoid membrane (B) Topological arrangement of the four subunits of the purified Cyt b/complex (C) A densitometric scan of an SDS-PAGE gel for b/ (B) from Hauska, Schiitz and Biittner (1996) The cytochrome b/ complex - composition, structure and function. In DR Ort and CF Yocum (eds) Oxygenic Photosynthesis - The Light Reactions, p 384. Kluwer (C) from Black, Widger and Cramer (1987) Large-scale purification of active cytochrome b f complex from spinach chloroplasts. Arch Biochem Biophys 252 657.

Factors such as light, pH, relative humidity, gas composition and enzymatic systems are involved in the colour deterioration of fruits and vegetables. As an example, it has been found that ethylene produced during cutting in minimally fresh processed spinach notably accelerates the loss of chlorophylls, and damage is proportional to the ethylene level reached (Abe and Watada 1991). 

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