Iron general properties

FIGURE 16-10 Iron-sulfur center in aconitase. The iron-sulfur center is in red, the citrate molecule in blue. Three Cys residues of the enzyme bind three iron atoms the fourth iron is bound to one of the carboxyl groups of citrate and also interacts noncovalently with a hydroxyl group of citrate (dashed bond). A basic residue ( B) on the enzyme helps to position the citrate in the active site. The iron-sulfur center acts in both substrate binding and catalysis. The general properties of iron-sulfur proteins are discussed in Chapter 19 (see Fig. 19-5). 

The general properties of siderophores have been described extensively (2), and up-to-date lists of the individual compounds, their sources from aerobic and facultative aerobic species, and their properties have been published (3,4, 5). (Porphyrin Products, P. O. Box 31, Logan, UT 84321, sell a limited number of siderophores.) The earlier literature on iron assimilation by microbes, including enteric species, may be found elsewhere (6,7). For information on the chemical constitution and physiological role of the outer membrane of enteric bacteria, the reader is referred to Nakae and Nikaido (8). 

General Properties of Compounds of Nickel.—Nickel usually behaves as a divalent element. Its salts when anhydrous are yellow in colour. They can usually be obtained in various stages of hydration, in which condition they axe usually green, and frequently yield series of double salts, analogous in physical properties and in chemical constitution to many double salts obtainable with divalent iron. Like copper salts, those of nickel readily unite with ammonia. Like ferrous salts they absorb nitric oxide, but without change of colour.1... 

The Grouping of Elements into Triads—Atomic Weights of the Elements— General Properties of tho Elements—Comparative Study of Iron, Cobalt, and Nickel—Their Position in tho Periodic Table—Comparative Study of Iron, Ruthenium, and Osmium—Comparative Study of Cobalt, Rhodium, and Iridium—Comparative Study of Nickel, Palladium, and Platinum. 

There are numerous hypotheses-but few definitive results-as to what physicochemical characteristics of atmospheric particles are responsible for adverse health effects (Samet 2000 Schlesinger 2000). Hypotheses include general properties such as mass, surface area, or size, as well as more specific chemical properties such as acidity or elevated concentrations of transition metals (Dreher et al. 1997 Samet 2000). For example, it has been suggested that particulate iron is toxic due to its ability to generate the strongly oxidizing hydroxyl radical through the Fenton reaction (Ohio et al. 1996 Smith and Aust 1997 Donaldson et al. 1998 van Maanen et al. 1999) ... 

A wide variety of different cytochrome-linked electron-transfer systems is encountered in bacteria respiratory chains with oxygen, nitrate or sulphate as electron acceptors, fumarate reductase systems and light-driven cyclic electron-transfer systems (Fig. 3). All these systems are composed of several electron-transfer carriers, the nature of which varies considerably in different organisms. Electron carriers which are most common in bacterial electron-transfer systems are flavoproteins (dehydrogenases), quinones, non-heme iron centres, cytochromes and terminal oxidases and reductases. One common feature of all electron-transfer systems is that they are tightly incorporated in the cytoplasmic membrane. Another important general property of these systems is that electron transfer results in the translocation of protons from the cytoplasm into the external medium. Electron transfer therefore... 

Description and General Properties. Metal matrix composites (MMCs) consist of a metal or an alloy matrix with a reinforcement material (e.g., particulates, monofilaments, or whiskers). The matrix alloy, the reinforcement material, the volume and shape of the reinforcement, the location of the reinforcement, and the fabrication method can all be varied to achieve required properties. Most of the metal-matrix composites are made of an aluminum matrix. But aluminum-matrix composites must not be considered as a single material but as a family of materials whose stiffness, strength, density, and thermal and electrical properties can be tailored. Moreover a growing number of applications require improved matrix properties and therefore, metal matrices of magnesium, titanium, superalloys, copper, or even iron are now available commercially. Compared to bulk metals and their alloys, MMCs offer a number of advantages such as ... 

Phosphate s stickiness is a general property and will work with essential metals as well as toxic ones. One microbe keeps copper ions out of the way by packing them in subcellular compartments with sticky phosphates and calciums. Too much phosphate, on the other hand, depletes metals that the cell needs. Yeast with high phosphate levels suffer from iron depletion because the iron sticks to the phosphate. 

V. The Iron Branch of the Biosynthetic Chain and Some General Properties of Heme Compounds. 319... 

V. THE IRON BRANCH OF THE BIOSYNTHETIC CHAIN AND SOME GENERAL PROPERTIES OF HEME COMPOUNDS... 

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