Y structures

Protein tertiar-y structure is also influenced by the environment. In water a globular- protein usually adopts a shape that places its hydrophobic groups toward the interior, with its polar- groups on the surface, where they are solvated by water molecules. About 65% of the mass of most cells is water, and the proteins present in cells are said to be in their native state—the tertiary structure in which they express their biological activity. When the tertiar-y structure of a protein is disrupted by adding substances that cause the protein chain to unfold, the protein becomes denatured and loses most, if not all, of its activity. Evidence that supports the view that the tertiary structure is dictated by the primary structure includes experiments in which proteins are denatured and allowed to stand, whereupon they are observed to spontaneously readopt then native-state conformation with full recovery of biological activity. 

Why is the structure square-pyramidal It has been shown that a diamagnetic d6 ML5 complex distorts away from the Jahn-Teller active trigonal bipyramidal structure.20 Two more stable structures are possible a square pyramid (T) and a distorted trigonal bipyramid (Y). Theoretical studies21 have shown that the T and Y structures are very close in energy and that the preference for one over the other comes from a subtle balance of a and it properties of the ligands. 

A T structure with the strongest ct-donor D trans to the empty site (I in Scheme 1) is preferred in the case of three pure cr-donor ligands. The presence of a ir-acceptor ligand also makes the T structure more stable. When one of the ligands is a tt-donor, X, a Y structure of type II (Scheme 1) is observed. This structure permits the formation of a w bond between the empty metal d orbital and the lone pair of X. No such tt bond is present in the T structure since all symmetry adapted d orbitals are filled. This partial M—X multiple bond stabilizes Y over T. 

There are two antigen binding sites on each of the basic Ig-type monomeric structures, formed by the heavy-light chain proximity in the N-terminal, hypervariable region at the tips of the y structure. The unique tertiary structure created by these subunit pairings produces... 

Toyoshima, C., Nomura, H. and Sugita, Y. Structural basis of ion pumping by Ca2+-ATPase of sarcoplasmic reticulum. FEBSLett. 555 106-110,2003. 

Pnotollthograpti Icall y structured platinum thin film... 

Silk type Function Proteins (ratio )a Predicted structure from sequence Amino acid (%Y Structure in solution Conformational change in solutione Fiber degree of crystallinity mf Fiber extensibility (%)e... 

X-ray fluorescence spectra of most elements consist largely of bands associated with the K, L, and M series. The XRF associated with the K series is dominated by the oq/a doublet, although some very weak [i XRF can often be observed at higher energies. The L-series XRF will consist of three main groups of lines, associated with the a, / , and y structure. Ordinarily, the a, line will be the strongest, and the /h line will be the next most intense. The peaks within the M series are observed only for the heavier elements, and consist of an unresolved oq/o doublet as the strongest feature, followed by a band of peaks associated with the /i XRF. 

The a- and y-structures differ from the /3-structure in that the former do not consist only of octahedra the ce-structure has two four-coordinate and the y-structure two five-coordinate molybdenums. The a-octamolybdate consists of a planar ring of six edge-shared Mo06... 

Termonia, Y Structure-property relationships in short-fiber-reinforced composites,./. Polym. Sci., Polym. Phys. Ed., 32, 969 (1994). 

Takahashi N, Hitotsuya H, Hanzawa H, Arata Y, Kurihara Y, Structural study of asparagine-linked oligosaccharide moiety of taste-modifying protein, miraculin,... 

Nirasawa S, Nishino T, Katahira M, Uesugi S, Hu Z, Kurihara Y, Structures of heat-stable and unstable homologues of the sweet protein mabinlin, Eur J Biochem 223 989—995, 1994. 

Chatani, Y., Structural Features of Solid-State Polymerization, in Progress in Polymer Science Japan, Vol. 7, p. 149, K. Imahori and T. Higashimura, eds., Halsted Press (Wiley), New York, 1974. 

The first two of these atomic-orbital-based Slater determinants ( sx a sx (3 and sy a sy (3 ) are denoted "ionic" because they describe atomic orbital occupancies, which are appropriate to the R —> °° region, that correspond to X S + Y and X + Y valence bond structures, while sx a sy (3 and sy a sx (3 are called "covalent" because they correspond to X + Y structures. 

The Y structure of Ba2Fei4022 contains a double BO3 layer, which forms a T block, interleaved with the same S blocks in the stacking sequence (TS)3, see Fig. 14. The T block contains only octahedral and tetrahedral iron. 

Mizuoka, K., Ikeda, Y., Structural study on uranyl ion in l-butyl-3-methylimid-azolium nonafluorobutanesulfonate ionic liquid. Prog. Nucl. Ener., 47, 426-433, 2005. 

Perhaps the first step in this direction consisted of the realization that the minimal models usually employed for mechanistic investigations (which fold into the Y-structure) are suboptimal These truncated motifs require high (millimolar) concentrations of Mg + ions for proper folding and subsequent catalytic activity (typical rates of ca 1 min ) °. In contrast to this, natural hammerhead ribozymes are active at submillimolar (physiological) concentrations and exhibit much higher cleavage rates ca 870 min in the case of HHRzs isolated from schistosomes) . ... 

Yang W, Hendrickson WA, Crouch RJ, Satow Y. Structure of ribonuclease H phased at 2 A resolution by MAD analysis of the selenomethionyl protein. Science 1990 249 1398-1405. 

The availability of a six-membered transition state, although necessary, is not always sufficient for an intramolecular hydrogen abstraction to take place. The distance X-Y (structure 95a) also must fall between certain critical limits, usually attainable in nonrigid aliphatic systems but often unsatisfied in rigid situations, i.e., steroids. 

Similar effects are observed in y-irradiated n-C H (530 kGy) in the molten state. Three new structures are identified as a) one-bond crosslinks (H-structure), b) trans-vinylene groups and c) long branches (T- or Y-structure)144). However, highly crystalline polyethylene y-irradiated in the solid state at low doses (up to 40 kGy) yields predominantly the branched Y-structure. A failure to detect the cross-linked H-structure could arise from a) insufficient abundance of crosslinks to give a detectable signal and b) insufficient mobility of crosslinked chains in the polyethylene gel which results in very broad resonance lines, not observable during normal data acquisition in the solution 13C NMR experiment145). 

HL ME-KOTHERY RULES. When alloy systems form distinct phases, it is found that the ratio or the number of valence electrons to the numher of atoms is characteristic of Lhe phase (e.g., /), y-. s- whatever the actual elements making up the alluy. Thus, both Na, Phs and NisZiii are y-structures, with the electron-atom ratio 21 13. The rules are explained by the tendency to form a structure in which all the Brillouin rones are nearly Tull, or else entirely empty. 

Name S 8 Reagent (X—Y) Structure Name Adduct Structure... 

The acylation is thought to occur as shown in Scheme 3. The ir-allyl intermediate (5) was isolated in 86% yield and characterized by X-ray analysis.13 The NMR spectrum and crystal structure of (5) indicate that only the anti-al y structure is formed no other positional isomers were detected. The iron atom in (5) obtains a closed-shell electron configuration by intramolecular o-donation of a lone pair of electrons from the acyl oxygen atom, which is confirmed by a lowering the acyl CO bond order (vco 1637 cm-1).12 There is no direct evidence for formation of (4) its intermediacy has been suggested primarily based on the endo stereochemistry of the acylation reaction (see below). 

Wuhrer, M., Dennis, R.D., Doenhoff, M.J., Lochnit, G. and Geyer, R. (2000c) Schistosoma mansoni cercarial glycolipids are dominated by Lewis X and pseudo-Lewis Y structures. Clycobiology 10, 89-101. 

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