© 1999 Robert A. Freitas Jr. All Rights Reserved.

Robert A. Freitas Jr., Nanomedicine, Volume I: Basic Capabilities, Landes Bioscience, Georgetown, TX, 1999

4.6.4 Mechanochemical Temperature Sensors

Since binding rates are temperature sensitive, a chemical concentration sensor using steric probes immersed in a sample containing a precisely known concentration of target ligands can be used as a temperature sensor. Similarly, enzyme reaction rates increase with a change in temperature according to

{Eqn. 4.39}

where DT = T₂ - T₁, k₁ and k₂ are the reaction rate constants at temperatures T₁ and T₂, and Q₁₀ is the well-known temperature coefficient -- the ratio of the rates of reaction measured at two temperatures 10°C apart. Q₁₀ ~ 2 for most enzymes, but may range up to 4 for some enzymes that catalyze reactions with unusually high activation energies. Assuming Q₁₀ ~ 4, the (112 nm)³ sensor with Dc / c = 0.01(1%) from Section 4.2.2 can distinguish temperatures 0.07 K apart; the huge (1.44 micron)³ sensor with Dc / c = 10^-5 (0.001%) resolves DT ~ 72 microkelvins. Because of their relative volumetric inefficiency, such sensors are best used in large DT applications. Similar considerations apply to thermal sensors based on the temperature sensitivity of protein folding (as in heat shock protein mediators of cellular responses to a 5 K change^465,466), protein thermal contraction,¹²⁶¹ and thermal conformation rate constants for protein a helices that typically coil in ~10^-6 sec.^467,2324 The quantum tunneling transmission coefficient for ion channels is also exquisitely temperature-sensitive⁶⁷⁹ and thus could serve as the basis of a nanoscale thermal sensor.

Last updated on 17 February 2003