Biomolecular dynamics and stability are predominantly investigated in vitro and extrapolated to explain function in the living cell. We present fast relaxation imaging (FreI), which combines fluorescence microscopy and temperature jumps to probe biomolecular dynamics and stability inside a single living cell with high spatiotemporal resolution. We demonstrated the method by measuring the reversible fast folding kinetics as well as folding thermodynamics of a fluorescence resonance energy transfer (FRET) probe-labeled phosphoglycerate kinase construct in two human cell lines. Comparison with in vitro experiments at 23-49 degrees C showed that the cell environment influences protein stability and folding rate. FReI should also be applicable to the study of protein-protein interactions and heat-shock responses as well as to comparative studies of cell populations or whole organisms.

Two experiments investigated the effects of the number of health recommendations (e.g., quit smoking; relax for a day) contained in a health-promotion message on recommendation recall and intentions to enact the recommendations. We hypothesized that if recommendations are stored individually, a higher number of presented recommendations will increase the number of recalled recommendations. As the number of recommendations increases, however, recipients are likely to summarize more recommendations as part of a single, more general theme (or header), resulting in a decrease in the proportion of recalled recommendations. Two experiments (N = 193 and N = 266) found that the total number of recalled recommendations increased and the proportion of recalled recommendations decreased with the number of presented recommendations. Experiment 2 replicated the findings with the number and the proportion of intended behaviors. The implications of these findings for future behavioral health interventions are discussed.