Roles in biological processes

The activity of Bik affects various biological functions, including inflammation, cell signaling, and apoptosis. 

These serine proteases are used to remove pathogens by their hydrolytic activity. They degrade cell membrane proteins and connective tissue matrices by hydrolysis of extracellular matrix proteins such as fibronectin, type IV collagen and laminin, or solubilizing fibrous elastins [55, 56]. Immune cell proteases also are capable of cleaving cytokines, growth hormone, neuropeptides, and procoagulant proteins such as Factors X and V. 

During inflammation, degranulation of immune cells releases serine proteases that pass through and bind to the capillary wall. Increased levels of Bik suppress these immune cell proteases and protect the extracellular matrix in arterial walls and connective tissue [4]. Bik inhibits phagocytic destruction of cells. Bik has been shown to inhibit elastases, granzymes A and K [4, 57], Mast cell tryptases (J3- and a-tetrameric forms with a molecular weight of 134 kDa) are resistant to aprotinin [58]. Lymphocytes serine esterase TL2 is not inhibited by Bik [59]. 

Trypsin is typically considered an enzyme found in the pancreas and small intestine. However, trypsin, thrombin, and plasmin are also widely expressed in endothelium, including epithelial immune cells as well as neurons. Upregulated expression and release occurs during both acute and chronic inflammation [60], Autocrine release of trypsin and thrombin causes activation of protease-activated receptors (PARs) reaction leading to cellular proliferation and inflammation [4], This response includes release of proteins by all cells during chronic inflammation. Bik prevents PAR activation on cell surfaces. 

Muscle cells release kallikrein during inflammation causing formation of active kinin peptides (bradykinin and kallidin) from kininogen [65, 66]. Kinins are peptide hormones that produce vasodilation, increase capillary permeability, and cause pain and infiltration of neutrophils. There is a direct correlation between the amount of kinin in plasma or tissues and the degree of inflammation. Vascular dilation causes increased blood flow to infection [67, 68], Bik inhibits formation of kinins and vascular dilation by kallikrein, thereby inhibiting smooth muscle contraction [69-71], 

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All the long-range forces discussed in this chapter play a role in biological processes. Interactions between membranes, proteins, ligands, antibodies... 

Some esters of inorganic acids, such as dimethyl sulfate, are used as reagents in synthetic organic chemistry. Certain naturally occuning alkyl phosphates play an important role in biological processes. 

Up to this point all our attention has been directed toward aldoses, carbohydrates having an aldehyde function in their open-chain form. Aldoses are more common than ketoses, and their- role in biological processes has been more thoroughly studied. Nevertheless, a large number of ketoses are known, and several of them are pivotal intermediates in carbohydrate biosynthesis and metabolism. Examples of some ketoses include D-ribulose, L-xylulose, and /-fructose ... 

Several metal ions play a crucial role in biological processes, whereas some others are toxic. Alteration of the metal concentration in the body can often be correlated to disease states. The necessity for in vivo determination of metal ion concentration and distribution has prompted research to develop appropriate metal-responsive MRI contrast agents. 

J. R. In Metal Ions in Biological Systems. Volume 37. Manganese and its Role in Biological Processes Eds. Sigel, A. Sigel, H. Marcel Dekker New York, 2000. 

Iron-sulfur proteins are non-heme electron carriers present in a wide range of living organisms and are known to cover different and important roles in biological processes. They will be treated here in order of their increasing iron content. 

Kroneck PMH, Aht DJ (2002) Molybdenum in nitrate reductase and nitrite oxidoreductase. In Molybdenum and Tungsten- Their Roles in Biological Processes. Sigel A, Sigel H (eds) Marcel Dekker, Inc., New York, 369-403... 

Calcium plays an essential role in biological processes (calcification of organisms, formation of bones etc.). Calcium has six stable isotopes in the mass range of 40 to 48 with the following abundances (Rosman and Taylor 1998)... 

The reaction of carbon-centered free radicals with O2 is one of the distinguishing features of these intermediates (equations 1, 34, 35). The formation of peroxyl radicals 43 in hydrocarbon oxidation (equation 68) has been of continued interest, " including the important role in biological processes. Peroxyl radicals may also be formed by H atom abstraction from hydroperoxides. 

In many cases, these polymer chains take on a rod-like (calamitic LCPs) or even disc-like (discotic LCPs) conformation, but this does not affect the overall structural classification scheme. There are many organic compounds, though not polymeric in nature, that exhibit liquid crystallinity and play important roles in biological processes. For example, arteriosclerosis is possibly caused by the formation of a cholesterol containing liquid crystal in the arteries of the heart. Similarly, cell wall membranes are generally considered to have liquid crystalline properties. As interesting as these examples of liquid crystallinity in small, organic compounds are, we must limit the current discussion to polymers only. 

Competition between mono- and di-valent cations has an important role in biological processes. Furthermore, the lipophilicity of a ligand and its complex plays an important role in deciding whether a species is soluble in organic media of low polarity. This has important consequences in areas such as phase-transfer catalysis, the use of crown ethers as anion activators, and in cation transport through lipid membranes. Many crown ethers have now been synthesized with incorporation of long alkyl side chains and enhanced lipophilicity and used successfully in the above areas. 

Among the metals which have achieved prominence only recently, molybdenum must certainly occupy first place. It has attracted interest chiefly because of its role in biological processes and also because it shows a great variety of oxidation states and coordination numbers. Steifel s extensive review of molybdenum complexes covers their chemistry up to 1977.3 Because of their use in nuclear medicine, the complexes of technetium have received recent interest.4... 

POTASSIUM AND SODIUM (In Biological Systems). Potassium and sodium play major roles in biological processes. Because of the numerous parallels between these two elements in metabolism, they are treated in a single entry, with appropriate distinctions made. 

Zinc is one of the more abundant trace elements (Table 1), and its essential role in biological processes is now well established. Over 100 enzymes require zinc for activity, even though only a relatively small number of these have been well studied. Examples are listed in Table 12. In this discussion most attention will be paid to the well-characterized zinc enzymes, but it must be stressed that there is increasing interest in other aspects of the biological chemistry of zinc, notably... 

The tidal flats of marine environments are areas of extreme complexity and biological activity. They serve as both sources and sinks of a wide variety of compounds and materials. They are in a constant state of mass, energy and momentum flux with the surrounding environment In these areas sulfur plays a major role in biological processes, principally because of the relatively nigh concentration of sulfate ion in marine waters. 

Food authentication, application of stable isotope tracers, characterization of complex metallobiomolecules, and investigation of their role in biological processes are all areas in which ICP-MS can play a more and more critical role. Speciation will continue to be a very dynamic field of investigation and the integration of speciation and metabolism studies with the use of stable isotopes as species-specific tracers is likely to become a research area of vital importance. On... 

A. Sigel and H. Sigel eds, Molybdenum and Tungsten Their Roles in Biological Processes , Marcel Dekker, New York, 2002, Vol. 39. 

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