Controlled mechanochemical coupling of anti-junctions in DNA origami arrays.

Allostery is a hallmark of cellular function and important in every biological system. Still, we are only starting to mimic it in the laboratory. Here, we introduce an approach to study aspects of allostery in artificial systems. We use a DNA origami domino array structure which-upon binding of trigger DNA strands-undergoes a stepwise allosteric conformational change. Using two FRET probes placed at specific positions in the DNA origami, we zoom in into single steps of this reaction cascade. Most of the steps are strongly coupled temporally and occur simultaneously. Introduction of activation energy barriers between different intermediate states alters this coupling and induces a time delay. We then apply these approaches to release a cargo DNA strand at a predefined step in the reaction cascade to demonstrate the applicability of this concept in tunable cascades of mechanochemical coupling with both spatial and temporal control.

Single antibody detection in a DNA origami nanoantenna.

DNA nanotechnology offers new biosensing approaches by templating different sensor and transducer components. Here, we combine DNA origami nanoantennas with label-free antibody detection by incorporating a nanoswitch in the plasmonic hotspot of the nanoantenna. The nanoswitch contains two antigens that are displaced by antibody binding, thereby eliciting a fluorescent signal. Single-antibody detection is demonstrated with a DNA origami integrated anti-digoxigenin antibody nanoswitch. In combination with the nanoantenna, the signal generated by the antibody is additionally amplified. This allows the detection of single antibodies on a portable smartphone microscope. Overall, fluorescence-enhanced antibody detection in DNA origami nanoantennas shows that fluorescence-enhanced biosensing can be expanded beyond the scope of the nucleic acids realm.

Addressable nanoantennas with cleared hotspots for single-molecule detection on a portable smartphone microscope.

The advent of highly sensitive photodetectors and the development of photostabilization strategies made detecting the fluorescence of single molecules a routine task in many labs around the world. However, to this day, this process requires cost-intensive optical instruments due to the truly nanoscopic signal of a single emitter. Simplifying single-molecule detection would enable many exciting applications, e.g., in point-of-care diagnostic settings, where costly equipment would be prohibitive. Here, we introduce addressable NanoAntennas with Cleared HOtSpots (NACHOS) that are scaffolded by DNA origami nanostructures and can be specifically tailored for the incorporation of bioassays. Single emitters placed in NACHOS emit up to 461-fold (average of 89 ± 7-fold) brighter enabling their detection with a customary smartphone camera and an 8-US-dollar objective lens. To prove the applicability of our system, we built a portable, battery-powered smartphone microscope and successfully carried out an exemplary single-molecule detection assay for DNA specific to antibiotic-resistant Klebsiella pneumonia on the road.

The influence of 30 minutes of light to moderate intensity cycling on postprandial lipemia.

BACKGROUND: Elevated postprandial lipemia is an independent risk factor for coronary heart disease, and bouts of moderate intensity exercise of 60 min or more are often reported to lower postprandial lipemia. Information on moderate intensity exercise bouts of shorter duration corresponding to the current recommendations of health-maintaining exercise (i.e. 30 min or energy expenditure of approximately 630 kJ), however, is scarce. Therefore, we searched for the lowest exercise intensity during 30 min of light to moderate intensity cycling that still reduced postprandial lipemia. DESIGN: We employed a repeated measures cross-over design. METHODS: Twelve healthy, not endurance trained, young men performed three activity trials (30 min cycling with a target energy expenditure of 420, 630 and 840 kJ) before ingestion of two mixed meals with a macronutrient composition corresponding to current recommendations and a control trial (no physical activity before meal ingestion). Capillary triacylglycerol was measured in the fasting state and hourly for 6 h after the first meal. Respiratory gases were analyzed in the fasting state, and 3 and 6 h after the first meal. Triacylglycerol and respiratory responses between the trials were compared with analyses of variance. RESULTS: Postprandial lipemia and the incremental area under the triacylglycerol curve were not significantly different with the activity trials compared with the control trial. The postprandial respiratory exchange ratio was also not significantly affected by activity. CONCLUSIONS: Thirty minutes of light to moderate intensity cycling did not reduce postprandial lipemia after two mixed meals with a moderate fat content in healthy, not endurance trained, young men.

The influence of walking performed immediately before meals with moderate fat content on postprandial lipemia.

BACKGROUND: Postprandial lipemia is an independent risk factor for coronary heart disease. Single bouts of moderate exercise may lower this risk, but the minimum duration of moderate intensity exercise that still lowers postprandial lipemia is not known. We, therefore, performed a dose-response study with a normal, daily life setting, to identify the minimum duration of moderate intensity walking that lowers postprandial lipemia in sedentary, healthy young men. METHODS: Sixteen men performed three activity trials (30, 60, or 90 min of treadmill walking at 50% of their individual VO2max) and a control trial with no physical activity in a repeated measures crossover design. The subjects walked immediately before ingestion of the first of two mixed meals, which were served 3 h apart. The meals had a moderate fat content (0.5 g per kg body mass and 33% of total energy per meal) and a macronutrient composition corresponding to current recommendations. Each meal provided one third of the subject's estimated daily energy requirement. Venous blood samples were taken in the fasted state, and then hourly for 6 h after the first meal to assess the postprandial phase. Postprandial lipemia (the incremental area under the curve (dAUC) of triacylglycerol) was compared with a mixed model analysis and Tukey's adjustment. RESULTS: Postprandial lipemia (dAUC of triacylglycerol) was, compared to the control trial, +2% (P = 1.00), -14% (P = 0.24), and -15% (P = 0.23) in the 30, 60, and 90 min walking trials, respectively. CONCLUSION: Moderate intensity walking of 60 and 90 min duration slightly, but insignificantly, reduced postprandial lipemia after two mixed meals with moderate fat content in sedentary, healthy young men, compared to inactivity. Therefore, it should be reconsidered if the acute exercise-induced reduction in postprandial lipemia usually observed in studies using high fat meals is of importance in a real, daily life setting.