Muscle contraction linear

FIGURE 5.19 Method of Barlow for measurement of affinity of a partial agonist, (a) Guinea pig ileal smooth muscle contraction to histamine (filled circles) and partial histamine receptor agonist E-2-P (N,N-diethyl-2-(l-pyridyl)ethylamine (open circles). Dotted lines show equiactive concentrations of each agonist used for the double reciprocal plot shown in panel b. (b) Double reciprocal plot of equiactive concentrations of histamine (ordinates) and E-2-P (abscissae). Linear plot has a slope of 55.47 and an intercept of 1.79 x 10s. This yields a KB (1 — tp/ta) = 30.9 pM. (c) Variant of double reciprocal plot according to Equation 5.8. (d) Variant of double reciprocal plot according to Equation 5.10. Data redrawn from [10],... 

Jimenez MC, Dietrich-Buchecker C, Sauvage JP (2000) Towards synthetic molecular muscles contraction and stretching of a linear rotaxane dimer. Angew Chem Int Ed 39 ... 

The two statements are in fact related. In our example, a perfect similarity of theoretical and experimental plots could only be expected if there were a linear relationship between receptor saturation with norepinephrine and muscle contraction. Considering that muscle contraction is triggered quite a bit downstream of receptor activation, there are numerous possible factors that will distort this linearity, and in reality no linear relationship will ever be observed if drug target and drug effect are separated by intervening biochemical cascades. It thus turns out that the shape of a dose-effect relationship will depend very much on the functional proximity of the drug receptor molecule and the observed parameter. 

The families of proteins that consume ATP while functioning as protein-based machines are called ATPases. Muscle contraction, just noted above, is a member of the family of linear (contractile) protein motors that also includes ATPases that walk along protein tubules and transport elements from one part of the cell to another. Another class of protein motors that uses ATP rotary and nonrotary ion pumps transports ions from one side to the other of the... 

The amplitude of the EMG as measured on the skin surface is related, although not linearly, to muscle contraction force. In general, an increasing frequency and complexity of the myogram biopotential follows increasing muscular contraction. This results from both the increased motor unit firing rate and the increased recruitment of muscle fibrils. 

Myoelectric control derives it name from the electromyogram (EMG), which it uses as a control input. When a muscle contracts, an electric potential (the EMG) is produced as a by-product of that contraction. If surface electrodes are placed on the skin near a muscle, they can detect this signal (Fig. 32.26). The signal can then be electronically amplified, processed, and used to control a prosthesis. While the intensity of the EMG increases as muscle tension increases, the relationship is a complex nonlinear process that depends on many variables, including the position and configuration of the electrodes (Heckathome and Childress, 1981). Although the EMG is nonlinear it is broadly monotonic, and the human operator perceives this response as more or less linear. 

Based on this analysis, a muscle-like linear actuator was conceptually constructed (see Fig. 2.47 (a)). The linear actuator is composed of rectangular-shaped elementary units along the axial direction, and each elementary unit expands or contracts under an applied voltage. The accumulated bending displacements result in a large actuation displacement... 

Fluorescence polarization (FP) measurements provide information on molecular orientation and mobility and processes that modulate them, including receptor-ligand interactions, protein-DNA interactions, proteolysis, membrane fluidity, and muscle contraction. The degree of polarization is determined from measurements of fluorescence intensities parallel and perpendicular with respect to the plane of linearly polarized excitation light, and is expressed in terms of fluorescence polarization (P) or anisotropy (r). Therefore, the FP experiment is less... 

The cellular unit that is active toward the contraction of skeletal muscles, known as the sarcomere, is comprised of alternatively stacked filaments of the proteins actin and myosin. During muscle contraction, the protein filaments slide past each other as a result of a rowing action of the surface myosin heads (Figure 6.92a). Hence, an effective biomimetic approach would entail the design of a linear architecture that features sliding components that will respond to a chemical stimulus. This approach has recently been demonstrated with the design of a rotaxane molecule that exhibits redox-controlled contraction and extension of the molecular architecture, in response to a chemical or electrochemical stimulus (Figure 6.92b). ... 

The quasi-linear variation of power with ATP hydrolysis is observed experimentally, as the contraction is being activated at the level of actinomyocin activity. The kinetic approach suggests that the muscle power output varies hyperbolically with the ADP concentration. Both the ADP control and the Gibbs energy of ATP hydrolysis control are similar, and when muscle power is varied voluntarily, muscle energetics may be represented by the linear flow-force relationships. 

Another area of NEMS that is receiving tremendous attention is the mimicry of biological systems, aptly referred to as biomimetics. For instance, in the development of linear molecular muscles that undergo contraction and extension movements. Initial work in this field utilized transition metal complexes containing rotaxanes and catenanes, due to the nondestructive redox processes occurring on the metal centers.Though these complexes were actuated by a chemical reaction, the movement was in a noncoherent manner. In order to better mimic skeletal muscle movement, one has to look at the mode of motion within the most efficient molecular machines - in our human bodies. 

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