Ultrasensitive responses

Ultracentrifugation 108,109 Ultracentrifuge 100 analytical 108 optical system, figure 109 Ultrafiltration 100 Ultrasensitive responses 567 Ultrasonic sound 468 UMP (Uridine5-phosphate) 200, 200s,203 Unimolecular processes 457 Uniporters 414 Units, International System 2 Unsatisfied ends of hydrogen bonded chains 64... 

This is sketched in simplified form in Fig. 11-13. The many amplification steps provide for ultrasensitive responses. 

T.W. Hansch, A.L. Schawlow, P. Toschek, Ultrasensitive response of a CW dye laser to selective extinction. IEEE J. Quantum Electron. 8, 802 (1972)... 

Ultrasensitive assays for PSA contribute to the earlier detection of prostate cancer relapse and (or) residual disease in prostatectomized patients as well as the more timely evaluation of response to current therapies. PSA determinations can be useful in detecting metastatic or persistent disease in patients following surgical or medical treatment of prostate cancer. Persistent elevation of PSA following treatment, or an increase in the pretreatment PSA concentrations, is indicative of recurrent or residual disease. Hence, PSA is widely accepted as an aid in the management of prostate cancer patients, and serum levels are most useful when sequential values are obtained and monitored over time. After complete removal of the prostate gland (radical prostatectomy), PSA levels should become very low or undetectable. A rise of the serum PSA level in prostatectomy patients indicates residual prostate tissue, recurrence, or metastasis of the disease (13, 16, 24, 36). 

CNTs offer an exciting possibility for developing ultrasensitive electrochemical biosensors because of their unique electrical properties and biocompatible nanostructures. Luong et al. have fabricated a glucose biosensor based on the immobilization of GOx on CNTs solubilized in 3-aminopropyltriethoxysilane (APTES). The as-prepared CNT-based biosensor using a carbon fiber has achieved a picoamperometric response current with the response time of less than 5 s and a detection limit of 5-10 pM [109], When Nation is used to solubilize CNTs and combine with platinum nanoparticles, it displays strong interactions with Pt nanoparticles to form a network that connects Pt nanoparticles to the electrode surface. The Pt-CNT nanohybrid-based glucose biosensor... 

Xue C, Cai F, Liu H (2008) Ultrasensitive fluorescent responses of water-soluble, zwitter-ionic, boronic acid-bearing, regioregular head-to-tail polythiophene to biological species. ChemEur J 14 1648-1653... 

Figure 8. Two routes to ultrasensitivity. A, Cooperativity generates an ultrasensitive dose-response curve. Plots were generated for the Hill equation, y = x / ( C + x"), for C = 20 for n = 1, 2 and 3. B, An exponential function also generates an ultrasensitive dose-response curve. Plot was generated for the equation y = e / (e + e ) for C = 20.

An attempt was made recently to find out how sensitively the regulatory system that controls the cell cycle and cell proliferation responds to signal input. Ferrell et found that, in intact oocytes, the response is ultrasensitive , a kinetic characterization introduced by Daniel E. Koshland Jr.26 (Ultrasensitivity has been defined as the response of an enzyme that is more sensitive to changes in the concentration of the substrate than an enzyme with a normal hyperbolic response, according to the Michaelis-Menten equation. One can also use the Hill coefficient (wh) to indicate hyperbolic (Michaelis-Menten) sensitivity ( h = 1-0), ultrasensitivity ( h > l)j and subsensitivity ( h <... 

There have been many instances when biological agents have been ruled out and all volatile chemicals have been shown to be present in concentrations below those believed to induce symptoms. In all such instances that have been reported in the literature, the symptoms have either been ascribed to ultrasensitive individuals or psychological responses on the part of those reporting the symptoms. Recent research has established that mixtures of... 

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