Chain complex

In particular, Example 3.15(1) together with Theorem 3.26 shows that, independently of the triangulation, the homology groups of an n-dimensional sphere are given by Z) = 0 for i n, and Z) = Z. 

In this section we introduce a notion from homological algebra that is behind all our definitions of homology and cohomology. 

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Cations which are covalently attached to the allyl anion part by a cr-bond and have sufficient Lewis acid properties offer the broadest versatility and highest levels of stereocontrol, since the C—C bond-forming step can occur in a pericyclic process9 accompanied by allylic inversion. It is reasonable to assume the prior assembly of both reaction partners in an open-chain complex, in which usually the (F )-oxonium ion, avoiding allylic 1,3-strain10, is predominant. 

Complexes of the Mitochondrial Electron-Transport Chain Complex I (NADH Ubiquinone Oxidoreductase)... 

The BaBPOs compound was first prepared and structurally characterized by Bauer [12]. Figure 21.2 shows the crystal structure of BaBPOs. Its structure is similar to all stillwellite-like compounds with the space group P322. Its main structural elements are spiral tetrahedral chains [001] built of three-membered rings. The contact between the BO4 tetrahedra that form the central part of these chains are reinforced by PO4 tetrahedra and thus [BPO5] heterotetrahedral chain complexes are produced. 

Functionally and strucmrally, the components of the respiratory chain are present in the inner mitochondrial membrane as four protein-lipid respiratory chain complexes that span the membrane. Cytochrome c is the only soluble cytochrome and, together with Q, seems to be a more mobile component of the respiratory chain connecting the fixed complexes (Figures 12-7 and 12-8). 

Each of the respiratory chain complexes I, III, and IV (Figures 12-7 and 12-8) acts as a proton pump. The inner membrane is impermeable to ions in general but particularly to protons, which accumulate outside the membrane, creating an electrochemical potential difference across the membrane (A iH )-This consists of a chemical potential (difference in pH) and an electrical potential. 

Figure 12-8. Principles of the chemiosmotic theory of oxidative phosphorylation. The main proton circuit is created by the coupling of oxidation in the respiratory chain to proton translocation from the inside to the outside of the membrane, driven by the respiratory chain complexes I, III, and IV, each of which acts as a protonpump. Q, ubiquinone C, cytochrome c F Fq, protein subunits which utilize energy from the proton gradient to promote phosphorylation. Uncoupling agents such as dinitrophenol allow leakage of H" across the membrane, thus collapsing the electrochemical proton gradient. Oligomycin specifically blocks conduction of H" through Fq.

The redox carriers are grouped into respiratory chain complexes in the inner mitochondrial membrane. These use the energy released in the redox gradient to pump protons to the outside of the membrane, creating an electrochemical potential across the membrane. 

Fig. 20. The variation in strain energy, V, for various conformations of [M(18-crown-6)]n+ complex, as a function of strain-free M-0 bond length. The M—O bond lengths of various metal ions are indicated on the M-0 bond length axis. The curves are for the planar D3d (+-+-+-), half-buckled (+-+--), and buckled (++-+ +-) conformers shown in Fig. 21, and for the complex of the open chain complex of pentaethylene glycol. The calculations were carried as described in the text, and in Refs. (4 and 60). Redrawn after Ref. (60). 

Chain complexes with oligo(pyridylamido) ligands 461... 

The trinuclear complexes [Au3(/7-MeC6H4N = OEt)3] and [Au3(Bzim)3] (Bzim= 1-benzylimida-zolate), which are colorless, can produce brightly colored materials by sandwiching naked Ag+ or Tl+ ions form linear-chain complexes (Figure 27) with luminescence properties as luminescence thermochromism.3173,3174... 

The capacity of cyclic ligands to stabilize less-common oxidation states of a coordinated metal ion has been well-documented. For example, both the high-spin and low-spin Ni(n) complexes of cyclam are oxidized more readily to Ni(m) species than are corresponding open-chain complexes. Chemical, electrochemical, pulse radiolysis and flash photolysis techniques have all been used to effect redox changes in particular complexes (Haines McAuley, 1982) however the major emphasis has been given to electrochemical studies. 

X = S) and corresponding open-chain complexes, the selfexchange rate constants were found to be of similar magnitude (with an overall variation of less than seven-fold). This result is perhaps somewhat unexpected in view of the considerable differences in rearrangement (between the cyclic and open-chain species) which might be expected to accompany electron transfer in these systems. 

Amylose complexes (wet precipitates) were prepared with fluoro-benzene, 1,1,2,2-tetrachloroethane, 1,1,2,2-tetrabromoethane, bromo-form, and ferf-butyl alcohol. The conformation and packing of the amylose chains complexed with halogen-substituted hydrocarbons are the same as found in the complex with tert-butyl alcohol, namely,... 

Mitochondrial DNA is inherited maternally. What makes mitochondrial diseases particularly interesting from a genetic point of view is that the mitochondrion has its own DNA (mtDNA) and its own transcription and translation processes. The mtDNA encodes only 13 polypeptides nuclear DNA (nDNA) controls the synthesis of 90-95% of all mitochondrial proteins. All known mito-chondrially encoded polypeptides are located in the inner mitochondrial membrane as subunits of the respiratory chain complexes (Fig. 42-3), including seven subunits of complex I the apoprotein of cytochrome b the three larger subunits of cytochrome c oxidase, also termed complex IV and two subunits of ATPase, also termed complex V. 

Defects of nuclear DNA also cause mitochondrial diseases. As mentioned above, the vast majority of mitochondrial proteins are encoded by nDNA, synthesized in the cytoplasm and imported into the mitochondria through a complex series of steps. Diseases can be due to mutations in genes encoding respiratory chain subunits, ancillary proteins controlling the proper assembly of the respiratory chain complexes, proteins controlling the importation machinery, or proteins controlling the lipid composition of the inner membrane. All these disorders will be transmitted by mendelian inheritance. From a biochemical point of view, all areas of mitochondrial metabolism can be affected (see below). 

All disorders except those in group 5 are due to defects of nDNA and are transmitted by Mendelian inheritance. Disorders of the respiratory chain can be due to defects of nDNA or mtDNA. Usually, mutations of nDNA cause isolated, severe defects of individual respiratory complexes, whereas mutations in mtDNA or defects of intergenomic communication cause variably severe, multiple deficiencies of respiratory chain complexes. The description that follows is based on the biochemical classification. 

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