Initial velocity patterns parallel

Initial velocity patterns obtained for the reduction of NAD by dihy-droplipoamide give a series of parallel lines (reciprocal plots). The K ... 

A third study of the kinetics of lipoamide dehydrogenase has utilized the enzyme isolated from rat liver (95). At 25°, the temperature of the two previous studies, when dihydrolipoamide was varied at fixed levels of NAD, the double reciprocal plots were concave down. At 37° this behavior was not observed. The detailed studies were carried out at the higher temperature. Rates were measured in both directions at pH 8.0, the pH optimum for the reduction of NAD. Under these conditions, initial velocity patterns for the forward and reverse reactions were a series of parallel lines. The Km for NAD was 0.52 mM, for dihydrolipoamide was 0.49 mAf, for NADH was 0.062 mM, and for lipoamide was... 

Figure 2 Reciprocal plots with A varied at different levels of B (parallel initial velocity pattern) or different levels of I (uncompetitive Inhibition pattern).

The constant term is missing, which leads to a parallel initial velocity pattern (Fig. 2) regardless of which substrate concentration is varied ... 

Thus, the initial velocity pattern will be intersecting regardless of whether A and B, A and C, or B and C are the variable and changing fixed substrates. In each case, the third substrate would be held at constant concentration for the entire pattern. If substrate B is truly saturating, however, the reversible sequence is broken and the A-C initial velocity pattern becomes a parallel one. In practice, the slope effect becomes smaller and smaller as fi is raised, but unless B is raised to over 100 times the Michaelis constant, a parallel pattern will not be seen. The A-B and B-C initial velocity patterns will always be intersecting, regardless of the level of the other substrate. Tfie same pattern seen for the ordered mechanism is seen for one where A and B have to be added in that order, but C can be added randomly. Such mechanisms are known (Viola Cleland, 1982). 

While an ordered trisubstrate mechanism shows a parallel initial velocity pattern when substrate B is saturating, a completely random mechanism shows intersecting patterns at all times. If one substrate must be added first, but the other two can be added randomly (Section 123), parallel initial velocity pattern wiU be obtained when either B or C is saturating. This is easily understood if one remembers that the saturation with B leads to addition in order A, B, and C, while saturation with C causes the order to be A, C, and B, that is, saturation at the branch point diverts aU reaction flux through one path or the other. 

In the absence of products, aU initial velocity patterns are parallel, in the same way as in the Ping Pong Bi Bi mechanism. However, the product inhibition patterns are different, and may serve to distinguish between the different systems (Table 6). 

In a sequential mechanism, an isotope effect equal to or close to one on one of the two substrate V/K values suggests a Steady-State Ordered mechanism. The V/K for the first substrate bound will have the isotope effect of unity. The isotope effect of one may also apply to the second substrate in a Ping Pong mechanism, but a distinctive, initial velocity pattern with parallel lines is obtained in this case. 

Liquids are able to flow. Complicated stream patterns arise, dependent on geometric shape of the surrounding of the liquid and of the initial conditions. Physicists tend to simplify things by considering well-defined situations. What could be the simplest configurations where flow occurs Suppose we had two parallel plates and a liquid drop squeezed in between. Let us keep the lower plate at rest and move the upper plate at constant velocity in a parallel direction, so that the plate separation distance keeps constant. Near each of the plates, the velocities of the liquid and the plate are equal due to the friction between plate and liquid. Hence a velocity field that describes the stream builds up, (Fig. 15). In the simplest case the velocity is linear in the spatial coordinate perpendicular to the plates. It is a shear flow, as different planes of liquid slide over each other. This is true for a simple as well as for a complex fluid. But what will happen to the mesoscopic structure of a complex fluid How is it affected Is it destroyed or can it even be built up For a review of theories and experiments, see Ref. 122. Let us look into some recent works. 

Fig. 13.16 Schematic representation of the flow pattern in the advancing front between two parallel cold walls. Black rectangles denote the stretching and orientation of a fluid particle approaching the central region of the front. The curved shape of the front causes fluid particles initially oriented in the y direction to end up on the wall, oriented in the x direction. The velocity profile upstream from the front is in the x direction and is viewed from a coordinate system located on the front. [Reprinted by permission from Z. Tadmor Molecular Orientation in Injection Molding, J. Appl. Polym. Sci., 18, 1753 (1974).]...

Figure 3 exhibits the director and charge distribution as well as the velocity field in the rr — z plane at onset of electroconvection, where the x direction is parallel to the initial (planar) director ahgnment and A is the pattern wavelength. 

A British engineer and scientist Osborne Reynolds demonstrated an experiment in 1883 in which water was introduced through a glass tube. The flow pattern was observed by injected dye at the inlet side of the tube and the flow rate was controlled at the outlet by a valve. Reynolds found out that the dye filament remained intact and parallel with the tube at low flow velocities. This flow is known as laminar flow. When the flow velocity was increased, the dye fllament initially began to oscillate up and down and finally broke up. The dye particles randomly mixed with water and occupied different positions of the tube. This flow is known as turbulent flow. 

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