Left-handed crossing

Connections between /3-strands are of two types—hairpins and cross-overs. Hairpins, as shown in Figure 6.27, connect adjacent antiparallel /3-strands. Cross-overs are necessary to connect adjacent (or nearly adjacent) parallel /3-strands. Nearly all cross-over structures are right-handed. Only in subtilisin and phosphoglucoisomerase have isolated left-handed cross-overs been identi-... 

For flavodoxin in Figure 6.32, identify the right-handed crossovers and the left-handed cross-overs in the parallel /3-sheet. 

The ways in which a-helices pack against one another were initially described by Crick (1953) as knobs into holes side chain packing which could work at either a shallow left-handed crossing angle or a... 

Consider now three knots, denoted by K, K , and K+. These three knots are identical under the cover Q, shown in Figure 3.6, and they differ only in their exposed parts, where they have a left-handed crossing, an avoided crossing, and a right-handed crossing, respectively. For any three such knots their Jones polynomials VK (t), VKo(t), and VK+(t) are interrelated by the equation... 

Figure 5.12 Examples of the characteristic graphs of the crossing patterns of three orthogonal views of the chain molecule backbone of the A.-Cro Repressor protein. The chain is oriented from the N-terminal to the C-terminal and the vertices of the graphs are labeled according to the handedness of the crossing - for left handed crossings, + for right handed crossings, 0 for the two terminals of the chain (no crossing).

The H-type cell devised by Lingane and Laitinen and shown in Fig. 16.9 will be found satisfactory for many purposes a particular feature is the built-in reference electrode. Usually a saturated calomel electrode is employed, but if the presence of chloride ion is harmful a mercury(I) sulphate electrode (Hg/Hg2 S04 in potassium sulphate solution potential ca + 0.40 volts vs S.C.E.) may be used. It is usually designed to contain 10-50 mL of the sample solution in the left-hand compartment, but it can be constructed to accommodate a smaller volume down to 1 -2 mL. To avoid polarisation of the reference electrode the latter should be made of tubing at least 20 mm in diameter, but the dimensions of the solution compartment can be varied over wide limits. The compartments are separated by a cross-member filled with a 4 per cent agar-saturated potassium chloride gel, which is held in position by a medium-porosity sintered Pyrex glass disc (diameter at least 10 mm) placed as near the solution compartment as possible in order to facilitate de-aeration of the test solution. By clamping the cell so that the cross-member is vertical, the molten... 

Figure 51-5. Formation of a fibrin clot. A Thrombin-induced cleavage of Arg-Gly bonds of the Aaand B(3 chains of fibrinogen to produce fi-brinopeptides (left-hand side) and the a and p chains of fibrin monomer (right-hand side). B Cross-linking of fibrin molecules by activated factor XIII (factor Xllla).

Figure 8.26. Equilibrium curve, optimal operation line, and optimal catalyst curves in an [ammonia] versus temperature plot for two different sets of conditions. Left-hand panel 420 °C, 80 bar, and 2 1 H2 N2 right-hand panel 450 °C, 200 bar, and 3 1 H2 N2. The crossing between the optimal catalyst curve for specific nitrogen bonding energy and the...

For axial capillary flow in the z direction the Reynolds number, Re = vzmaxI/v = inertial force/viscous force , characterizes the flow in terms of the kinematic viscosity v the average axial velocity, vzmax, and capillary cross sectional length scale l by indicating the magnitude of the inertial terms on the left-hand side of Eq. (5.1.5). In capillary systems for Re < 2000, flow is laminar, only the axial component of the velocity vector is present and the velocity is rectilinear, i.e., depends only on the cross sectional coordinates not the axial position, v= [0,0, vz(x,y). In turbulent flow with Re > 2000 or flows which exhibit hydrodynamic instabilities, the non-linear inertial term generates complexity in the flow such that in a steady state v= [vx(x,y,z), vy(x,y,z), vz(x,y,z). ... 

Fig. 10. Results of LES-based simulations of an agglomeration process in two vessels one agitated by a Rushton turbine (left) and one agitated by a Pitched Blade Turbine (right). The two plots show the agglomeration rate constant fl0 normalized by the maximum value, in a vertical cross-sectional plane midway between two baffles and through the center of the vessel. Each of the two plots consists of two parts the right-hand parts present instantaneous snapshots the left-hand parts present spatial distributions of time-averaged values after 50 impeller revolutions. Reproduced with permission from Hollander et al. (2003).

Bacterial, plant, and fungal enzymes for degradation/modification of polysaccharides left-hand-twisted /8-solenoid with L-type cross section... 

Viral enzyme for degradation of polysaccharides trimer of /3-solenoids with L-type cross section and a small left-handed twist... 

Bacterial virulence factor /8-solenoid with L-, T-type cross sections and left-handed twist... 

This model is a polar cross-/ structure with a left-handed twist that complies with the mass-per-unit-length data moreover, it readily accommodates sequence randomization because like residues are still stacked over like residues, regardless of their order, and sequence permutation does not increase the number of charged residues or prolines which would be most likely to destabilize structures of this kind (Fig. 10). The configuration of strands and turns allows some variation without putting charged residues inside the core structure. We envision that structural variations of this kind offer a plausible explanation for the phenomenon of prion variants, as discussed in Section VIII. 

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