Sulphur deficiencies

Methionine (Met) is one of the sensitive sulphur-containing amino-acids toward one-electron oxidation. However its ease of oxidation is also modulated by the structure. The one-electron oxidation of Met in peptides yields sulfide methionine radical cations (MetS +) which convert into intermediates that obtain catalytic support from neighbouring groups containing electron rich heteroatoms (S, N, O) and thus stabilize electron deficient sulphur centres in S.-.S, S.-.N, and S.-.O-three-electron bonded complexes (Fig. 5) [11]. 

The effect of sulphur from the gas phase is critically dependent on the effectiveness of fuel combustion. With good combustion to the limit of the available oxygen, and even down to 50% air deficiency, no serious effect was found from high-sulphur fuel in tests with 321S12 steel up to the usual limit of service temperature at 850°C, as shown in Table 7.9. With 310S24 steel at 1 100°C some effect from high sulphur content was found in 2 1 air gas with effective combustion, but none in 4 1 and 6 1 mixtures. 

In terms of amino acids bacterial protein is similar to fish protein. The yeast s protein is almost identical to soya protein fungal protein is lower than yeast protein. In addition, SCP is deficient in amino acids with a sulphur bridge, such as cystine, cysteine and methionine. SCP as a food may require supplements of cysteine and methionine whereas they have high levels of lysine vitamins and other amino acids. The vitamins of microorganisms are primarily of the B type. Vitamin B12 occurs mostly hi bacteria, whereas algae are usually rich in vitamin A. The most common vitamins in SCP are thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, choline, folic acid, inositol, biotin, B12 and P-aminobenzoic acid. Table 14.4 shows the essential amino acid analysis of SCP compared with several sources of protein. 

Other examples of linear correlations of log rate coefficients with — H0 have been reported though most of them are deficient in some respect. Satchell474 observed such a correlation in the dedeuteration of anisole and benzene in various aqueous or acetic acid solutions of sulphuric acid, and aqueous perchloric acid, media at 25 °C. First-order rate coefficients are given in Table 127 along with those for dedeuteration of [4,5-2H2]-l,3,5-trimethoxybenzene and -2-hy-droxy-l,3-dimethoxybenzene475. For the ortho- andpara-monodeuterated anisoles the slopes of the log rate versus — H0 plots were the same for aqueous sulphuric acid and for acetic acid-sulphuric acid so that it was concluded that the A-l mechanism therefore applied to non-aqueous media as well as to aqueous media. The fact that the slope of the log rate coefficient versus —H0 plot was less (1.12) for benzene in aqueous perchloric acid than that (1.36) previously found in aqueous... 

Alonso-Vante N, Chatzitheodorou G, Fiechter S, Mgoduka N, PouHos 1, Tributsch H (1988) Interfacial behavior of hydrogen-treated sulphur deficient pyrite (FeS2 x). Sol Energy Mater 18 9-21... 

A notable feature of the Western Canadian coals is their low sulphur content (usually <0.5%) which tends, however, to be partly offset by higher mineral matter contents than are associated with the Eastern coals. As well, bituminous coals in the mountain belts are typically deficient in vitrinite, which often represents less than 50% of the coal "substance" and only occasionally reaches 70-75%, but this is compensated by the fact that their micrinites and semifusinites tend to be "reactive" constituents when the coals are carbonized. Notwithstanding their low fluidity (rarely >1000 dd/min), Western mvb coals therefore make excellent metallurgical cokes when carbonized in suitably proportioned blends. 

Fuerstenau (1980) found that sulphide minerals are naturally floatable in the absence of oxygen. Yoon (1981) ever attributed the natural floatability of some sulphide minerals to their very low solubility. Finkelstein et al. (1975) considered that the natural floatability of sulphide minerals are due to the formation of elemental sulphur and related to the thickness of formation of elemental sulphur at the surface. Some authors reported that the hydrophobic entity in collectorless flotation of sulphide minerals were the metal-deficient poly sulphide (Buckley et al., 1985). No matter whichever mechanism, investigators increasingly concluded that most sulphide minerals are not naturally floatable and floated only under some suitable redox environment. Some authors considered that the natural floatability of sulphide minerals was restricted to some special sulphide minerals such as molybdenite, stibnite, orpiment etc. owing to the effects of crystal structure and the collectorless floatability of most sulphide minerals could be classified into self-induced and sulphur-induced floatability (Trahar, 1984 Heyes and Trahar, 1984 Hayes et al., 1987 Wang et al., 1991b, c Hu et al, 2000). 

Agricultural fertilization with sulphur is not a new concept - at the research level at least, sulphur has long been recognised as an essential plant nutrient. However because the complex role of sulphur - in soils, in plant material and in interaction with other essential element cycles - has never been fully understood, sulphur fertilizers have been used mainly on an empirical basis. As a result, sulphur fertilization has shown somewhat erratic performance Measured sulphur deficiency in soils has not always been correlated with poor crop yield and, as a corollary, sulphur fertilization of sulphur deficient soils has not always improved poor crop yields. Thus it has been difficult to routinely demonstrate an economic benefit to the farmer. 

As a group, the caseins are deficient in sulphur amino acids which limits their biological value (80 egg albumen = 100). asl- and -caseins contain no cysteine or cystine while aa2- and x-caseins have two cysteine residues per mole, which normally exist as intermolecular disulphides. 

A simpler example is the iron sulphide pyrrhotite, the composition of which is roughly FeS but which always contains rather too little iron. The X-ray pattern indicates the sodium chloride type of structure, and it appears that while the negative ion positions are fully occupied by sulphur, there is a deficiency of iron atoms in the positive ion sites. (Laves, 1930 Hagg and Sucksdorff, 1933.)... 

Stabilisation is conferred on a carbocation whenever the electron deficient centre is conjugated with aryl or olefinic groups, or with atoms possessing unshared electron pairs such as oxygen, nitrogen or sulphur. The most useful examples are the triphenylmethyl 1, cycloheptrienyl 2 (20), xanthylium 3 (74), pyrylium +... 

Sulphate is the form in which S is normally absorbed by plant roots and the reduction of sulphate for the synthesis of sulphur-containing compounds is universal for plants. Sulphur occurs in some amino acids, proteins and also in the oils of some plants such as cabbages and turnips. The S—H group is very important for the action of some enzymes and coenzymes. S is also a constituent of ferredoxins. A deficiency leads to stunting and yellowing but can be cured. A classical case of S deficiency known as tea yellows was identified in 1933 by Storey and Leach (reported in Hewitt and Smith, 1975). Sulphur deficiency leads to accumulation of amine and ammonia nitrogen, with little change in the total. 

This theory accounts for the dependence between the current efficiency and the concentration of HSO ions present in the solution. It cannot explain, however, why the yields at the electrolysis of solutions of sulphates, in which the concentration of HSO ions is very low, are even greater than when electrolysing solutions of sulphuric acid alone or its mixture with a sulphate. This deficiency is not found in the recent explanation of the reaction mechanism, according to which the sulphate ions SO - are primarily oxidized by hydrogen peroxide or by hydroxyl radicals formed, according to equations ... 

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