Alpha complex

J.P. Noel, H E. Hamm, and P.B. Sigler. 1993. The 2.2 A crystal structure of transducin-alpha complexed with GTP... 

As the parameter a varies from —oo to 0 and on to oo, the corresponding alpha complex goes from the empty set to the dual complex of the ball collection, and on to the Delaunay triangulation associated to the set of the centers... 

The minimal nonsimplices in Rips complexes are pairs of vertices at a distance exceeding the parameter t, whereas the alpha complexes and the witness complexes do not seem to benefit from the dual presentation. 

D, J Sturzebecher and WBode 1991. Geometry of Binding of the N-Alpha-Tosylated Piperidides of weffl-Amidino-Phenylalanine, Para Amidino-Phenylalanine and para-Guanidino-Phenylalanine to Thrombin and Trypsin - X-ray Crystal Structures of Their Trypsin Complexes and Modeling of their Thrombin Complexes. FEBS Letters 287 133-138. 

Inclusion compounds of the Cg aromatic compounds with tris((9-phenylenedioxy)cyclotriphosphazene have been used to separate the individual isomers (43—47). The Schardinger dextrins, such as alpha-cyclodextrin, beta-dextrin, and gamma-dextrin are used for clathration alpha-dextrin is particularly useful for recovering PX from a Cg aromatic mixture (48,49). PyromeUitic dianhydride (50) and beryllium oxybenzoate (51) also form complexes, and procedures for separations were developed. 

Shell Higher Olefin Process) plant (16,17). C -C alcohols are also produced by this process. Ethylene is first oligomerized to linear, even carbon—number alpha olefins using a nickel complex catalyst. After separation of portions of the a-olefins for sale, others, particularly C g and higher, are catalyticaHy isomerized to internal olefins, which are then disproportionated over a catalyst to a broad mixture of linear internal olefins. The desired fraction is... 

Because of the complexity of the polyether antibiotics tittle progress has been made in stmcture determination by the chemical degradation route. X-ray methods were the techniques most successfully applied for the early stmcture elucidations. Monensin, X206, lasalocid, lysocellin, and salinomycin were included in nineteen distinct polyether x-ray analyses reported in 1983 (190). Use of mass spectrometry (191), and H (192) and nmr (141) are also reviewed. More recently, innovative developments in these latter techniques have resulted in increased applications for stmcture determinations. Eor example, heteronuclear multiple bond connectivity (hmbc) and homonuclear Hartmann-Hahn spectroscopy were used to solve the stmcture of portimicin (14) (193). East atom bombardment mass spectrometry was used in solving the stmctures of maduramicin alpha and co-factors (58). 

Alpha-helical domains are sometimes large and complex... 

Alpha helices D and E from the L and M subunits (Figure 12.14) form the core of the membrane-spanning part of the complex. These four helices are tightly packed against each other in a way quite similar to the four-helix bundle motif in water-soluble proteins. Each of these four helices provides a histidine side chain as ligand to the Ee atom, which is located between the helices close to the cytoplasm. The role of the Ee atom is probably to... 

Iodine isocyanate was used to synthesize the first steroidal aziridine, 2, 3 -iminocholestane (95). from 5a-cholest-2-ene (91). This reaction sequence which is believed to proceed through a three-membered ring iodonium ion (92) illustrates the limitation of pseudohalogen additions for the synthesis of -aziridines. The iodonium complex forms from the least hindered side (usually alpha) and is opened tmK5-diaxially to give a -oriented nitrogen function. The 3a-iodo-2 -isocyanate (93) is converted by treatment with... 

FIGURE 21.11 The structure of UQ-cyt c reductase, also known as the cytochrome hci complex. The alpha helices of cytochrome b (pale green) define the transmembrane domain of the protein. The bottom of the structure as shown extends approximately 75 A into the mitochondrial matrix, and die top of the structure as shown extends about 38 A into the intermembrane space. (Photograph kindly provided by Di Xia and Johann Deismhofer [From Xia, D., Yn, C.-A., Kim, H., Xia,J-Z., Kachnrin, A. M., Zhang, L., Yn,... 

Although estrone and estradiol (26) have both been isolated from human urine, it has recently been shown that it is the latter that is the active compound that binds to the so-called estrogen receptor protein. Reduction of estrone with any of a large number of reducing agents (for example, any of the complex metal hydrides) leads cleanly to estradiol. This high degree of stereoselectivity to afford the product of attack at the alpha side of the molecule is characteristic of many reactions of steroids. 

In addition to intracellular heme-containing proteins, big-conductance calcium-dependent K+ (BKCa) channels and calcium-spark activated transient Kca channels in plasma membrane are also tar geted by CO [3]. As well known, nitric oxide (NO) also activates BKca channels in vascular smooth muscle cells. While both NO and CO open BKCa channels, CO mainly acts on alpha subunit of BKCa channels and NO mainly acts on beta subunit of BKca channels in vascular smooth muscle cells. Rather than a redundant machinery, CO and NO provide a coordinated regulation of BKca channel function by acting on different subunits of the same protein complex. Furthermore, pretreatment of vascular smooth muscle... 

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