Right-handed propellers

FIGURE 9-12 Right- and Left-handed Propellers, (a) Left-handed propeller and helix traced by the tips of the blades, (b) Right-handed propeller and helix traced by the tips of the blades. 

FIGURE 1.5. A three-bladed right-handed propeller. 

Each sheet of neuraminidase has a W topology (+1,+1,+1) [56] with four strands connected by reverse turns (Figure 3). The first strand of each sheet enters from the top, approximately parallel to and near the propeller axis the fourth strand exits from the bottom, approximately perpendicular to the propeller axis. Top and bottom surfaces of the head refer to the faces of the tetramer away and towards the viral membrane respectively. Each sheet thus has a characteristic 90° right-hand twist between the inner- and outermost strand. The six sheets and their connections to each other are topologically identical. 

Now let us return to the general form of the Gurney Eqn, namely Eqn (1). The right-hand term of Eqn (1) combines three distinct factors y/2E, which depends on the characteristics of the driver expl the form of the function/is determined by the geometry of the system c/m is the ratio of expl mass to the mass of the material propelled. It is instructive and useful to relate y r2E to some more common property of driver expl and this is done below... 

Figure 23. Rocket, Lorrain, 1630. Substantially as rockets are made today. After the propelling charge has burned completely and the rocket has reached the height of its flight, the fire reaches the charge in the head which bursts and throws out large and small stars, serpents and grasshoppers, or English firecrackers. The container, which is loaded into the head of the rocket, is shown separately with several grasshoppers in the lower right-hand comer of the picture.

Figure 24. Details of Construction of Rocket and of Other Pieces, Audot, 1818. The rocket case, already crimped or constricted, is placed upon the spindle (broche) the first portion of the propelling charge is introduced and pounded firmly into place by means of a mallet and the longest of the drifts pictured in the upper right-hand corner another portion of the charge is introduced, a shorter drift is used for tamping it, and so on until the case is charged as shown at the extreme left. A tourbillion (table rocket or artichoke) and a mine charged with serpents of fire are also shown.

Sialidase is a homotetramer with C4 symmetry composed of identical disulfide-linked subunits (Fig. 17.6a [62]). Each monomer is a glycosylated polypeptide with six p-sheets assuming the appearance of six blades of a propeller [6, 64] with a right-handed twist. The catalytic site is observed to be at the center of the sixfold pseudosymmetry axis, which passes through the center of each monomer and relates the six p-sheets to each other (Fig. 17.6b [63]) [64, 65], The active site contains a large number of conserved amino acid residues, which are involved in binding to sialic acid in the substrate sialoglycoconjugate [64],... 

D3 symmetry (Figure 4-20). Mirror images of this molecule look much like left- and right-handed three-bladed propellers. Further examples will be discussed in Chapter 9. 

We speak of a screw or a propeller as being right-handed or left-handed. ... 

The PMR data can be interpreted as suggesting that the ligands have the left-handed propeller configuration shown in the model (Fig. 7), although a right-handed configuration cannot be ruled out. Molecular models do not show either configuration to be any more strained than the... 

The bacterial flagellum is a right-hand helical fiber, composed almost entirely of the fibrous protein flagellin. That is, the flagellum does not contain microtubules, actin, myosin (see here), or any contractile system. The flagellum itself rotates as a means of propelling the bacterium (Figure 8.29). 

Such behavior raised many questions. What causes reversal of direction of the propeller Why do the bacteria tumble How does a bacterium "decide" when to tumble How is the flagellum changed from a left-handed to a right-handed superhelix How does this behavior help the bacterium to find food Most intriguing of all, what kind of motor powers the... 

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