Fig. 3: Temperature difference triggers cellular activity.

a, Schematic of a thermophoretic chamber subjected to a temperature difference (27–40 °C). After 16 h of incubation, the top (TOP), middle (MID) and bottom (BOT) fractions were freeze extracted and sampled for analysis. Chamber controls devoid of accumulation were incubated isothermally (ΔT = 0 °C) to switch off thermophoresis or rotated 90° into a horizontal orientation with (ΔT = 13 °C) to stop thermal convection. b, Ion concentration was probed by chromatography. Mg²⁺, K⁺ and \({{\rm{PO}}}_{4}^{3-}\) showed a strong thermophoretic response with 30-, 7- and 85-fold relative accumulation and 2.5-, 2- and 2.7-fold absolute up-concentration at the bottom of the chamber. The data are represented as the mean value of triplicate experiments ± standard deviation. c, Agarose gel shows a 2.7-fold absolute accumulation of the linear DNA template encoding sfGFP used for the experiments. DNA* is the linear DNA fragment as a migration reference. d, Merged image of a sodium dodecyl sulfate polyacrylamide gel. The black bands are PURExpress proteins visualized with stain-free technology (Bio-Rad). The relative and absolute accumulations of the total protein were, on average, 6.4- and 1.8-fold, respectively. The green bands correspond to the intrinsic fluorescence of sfGFP. e, sfGFP fluorescence kinetics measured at the bottom of the chambers (black squares) from 3-fold-diluted TX-TL reactions incubated with and without a temperature difference (green and grey, respectively). Gene expression was only observed when the temperature difference was applied. The data are represented as the mean value of triplicate experiments ± standard deviation. f, Transcription from DNA to RNA was separately visualized using a PCR fragment coding for F30 Broccoli aptamer, showing RNA concentration by fluorescence. The observed accumulation rose faster, probably due to faster transcription, but also from a superior thermal accumulation of RNA at the bottom of the chamber. No signal could be detected in isothermal conditions, suggesting no active transcription.