Function transducer

The transducer function defines the efficiency of the system to translate receptor stimulus into response and defines the efficacy of the agonist. Specifically, it is the fitting parameter of the hyperbolic function linking receptor... 

In terms of classical receptor theory—where response is a hyperbolic function of stimulus (Response = Stimulus/ (Stimulus 4- [3), [3 is a transducer function reflecting the efficiency of the stimulus-response mechanism of the system), and stimulus is given by Stimulus = [A] e/([A] + KA) (e is the efficacy of the agonist)— Response is given by... 

X = transducer function for response to the full agonist and constitutive y active receptor state. 

For the rest of the control loop, Gc is obviously the controller transfer function. The measuring device (or transducer) function is Gm. While it is not shown in the block diagram, the steady state gain of Gm is Km. The key is that the summing point can only compare quantities with the same units. Hence we need to introduce Km on the reference signal, which should have the same units as C. The use of Km, in a way, performs unit conversion between what we dial in and what the controller actually uses in comparative tests. 2... 

Liu, L., Mohammadi, K., Aynafshar, B. et al. Role of caveolae in the signal transducing function of cardiac Na+/K+-ATPase. Am. J. Physiol. Cell Physiol. 284 C1550-C1560, 2003. 

One of the main limitations of the experimental methodology described above is related to the time constraint. It hinders the study of many interesting reactions that are too slow to ensure that the amplitude of the photoacoustic wave is independent of the kinetics of the process. This is the case, for instance, of transient lifetimes in the range of 100 ns to 0.1 ms for a 0.5 MHz transducer. Fortunately, there is an alternative procedure to deal with those cases where the condition r 1/v does not hold. The procedure, known as time-resolved PAC (TR-PAC), was developed by Peters and co-workers [282,284,299] and considers that the observed wave, Sexp(t), reflects the kinetics of the true heat deposition, S(t), as well as the detector response wave, T(t). In other words, SexP(t) is the convolution of S(t) with the transducer function, T(t)... 

To derive S(t), a deconvolution procedure is required. The transducer function is easily obtained by running an experiment where the photoactive species decays with x 1/v, which is the case of the photoacoustic calibrants mentioned. Recall... 

The mitogenic activated protein kinase (MAPK) downstream from the Ras protein is organized in modules containing three types of protein kinases, which are successively activated by sequential phosphorylation events. The cell contains different MAPK modules, which differ in the nature of the triggering stimuli and the nature and specificity of the protein kinase components. The signal transducing function of a MAPK pathway is thus determined by the nature of the MAPK module involved this, in turn, depends on the properties of the protein kinases it contains, which differ in regulation and substrate specificity. The exact composition of the MAPK module is not fixed rather, different subtypes of protein kinase may be recruited to a module in a variable... 

The ligand causes a stimulus by binding a receptor. That stimulus is then transformed by the cellular machinery into a response. Stephenson described the mathematical relationship between the stimulus and response as the transducer function (Equation 5.15). The response is some function, most likely nonlinear, of the stimulus. 

Figure 5.23 shows three lines for three different transducer functions. Sketch a graph of the log [L]-response curve for the E = S line. This should be fairly easy with no surprises. Now, on the same set of axes, sketch the log [L]-response curve for the E = 2 X S line. If you are uncertain, create an Excel graph to determine the shape of the curve. Discuss the differences. 

From a modeling point of view, the last equilibrium assumption that can be relaxed, for the processes depicted in Figure 10.1, is H4, between the activated receptors (v variable in the occupancy model) and the response E. Instead of the activated receptors directly producing the response, they interfere with some other process, which in turn produces the response E. This mechanism is usually described mathematically with a transducer function T which is no longer linear (cf. Section 10.4.1). This type of pharmacodynamic model is called indirect response and includes modeling of the response process usually through a linear differential equation of the form... 

First, mention can be made of cases in which the measured effect instead of being proportional to the activated receptors, follows a more general function E = T (v). This model is called receptor-transducer and was introduced by Black and Leff [409]. The function T is called a transducer function and its most common form is yet again the Emax function, which when replaced in (10.5) results in an Emax model but with different shape parameters called an operational model [441]. 

The isolated CFq-CFi has been incorporated into phospholipid liposomes and shown to carry in this form most of the energy-transducing functions which it catalyses within the thylakoid membranes. Thus, the reconstituted ATP synthase carries out ATP-dependent proton translocation resulting in both a 4pH and a developing across the reconstituted liposomes [72,73] an uncoupler-sensitive ATP-Pj exchange reaction [39] and ATP formation driven by artificially imposed 4pH and Ail/ [39,74,75], or by electric field pulses [56]. The ATP synthase proteolipo-somes provide the simplest system available today for the study of electrochemical-gradient-driven phosphorylation. 

EPMRs depend only on agonist affinity and T = transducer function of response to the... 

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