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Connecting neural circuit output to behaviour can be facilitated by the precise chemical manipulation of specific cell populations1,2. Engineered receptors exclusively activated by designer small molecules enable manipulation of specific neural pathways3,4. However, their application to studies of behaviour has thus far been hampered by a trade-off between the low temporal resolution of systemic injection versus the invasiveness of implanted cannulae or infusion pumps2. Here, we developed a remotely controlled chemomagnetic modulation-a nanomaterials-based technique that permits the pharmacological interrogation of targeted neural populations in freely moving subjects. The heat dissipated by magnetic nanoparticles (MNPs) in the presence of alternating magnetic fields (AMFs) triggers small-molecule release from thermally sensitive lipid vesicles with a 20 s latency. Coupled with the chemogenetic activation of engineered receptors, this technique permits the control of specific neurons with temporal and spatial precision. The delivery of chemomagnetic particles to the ventral tegmental area (VTA) allows the remote modulation of motivated behaviour in mice. Furthermore, this chemomagnetic approach activates endogenous circuits by enabling the regulated release of receptor ligands. Applied to an endogenous dopamine receptor D1 (DRD1) agonist in the nucleus accumbens (NAc), a brain area involved in mediating social interactions, chemomagnetic modulation increases sociability in mice. By offering a temporally precise control of specified ligand-receptor interactions in neurons, this approach may facilitate molecular neuroscience studies in behaving organisms.

Single domain magnetic nanoparticles are increasingly investigated as actuators of biological and chemical processes that respond to externally applied magnetic fields. Although their localized effects have often been attributed to nanoscale heating, recent experimental evidence suggests the need to consider alternative hypotheses. Here, using the stochastic Landau–Lifshitz–Gilbert equation and finite element modeling, we investigate and critically examine an alternative hypothesis that localized effects may instead involve the induced electric fields arising from the dynamical behavior of individual single domain magnetic particles. We model the magnetization dynamics and resulting induced electric fields for two relevant and distinct cases of magnetic nanoparticles in alternating magnetic fields: (1) magnetogenetic stimulation of channel proteins associated with ferritin and (2) catalytic enhancement of electrochemical hydrolysis. For the first case, while the local electric fields that ferritin generates are shown to be insufficient to perturb the transmembrane potential, fields on the surface of its mineral core on the order of 10 2 –10 3 V/m may play a more plausible role in mass transport of iron ions that indirectly lead to stimulation. For the second case, our model indicates that the highest interfacial electric field strengths, on the order of 10 2 V/m, are expected during reversal events. Thus, nanoparticles well suited for hysteresis heating can also act as intermittent sources of localized induced electric fields in response to an alternating applied field. Finally, we compare the magnitude and timescale of these electric fields to technologically relevant phenomena, showing that they are generally weaker and faster. [ABSTRACT FROM AUTHOR]

We recently shared our design of a two semester flipped organic chemistry course in which we gave students in-class quizzes to incentivize attendance and watching the lecture videos in advance. With a second iteration, we planned to make the video-watching experience more engaging. We accordingly hypothesized that if students completed short at-home quizzes while watching the videos, then attentiveness, engagement, and learning would increase. We tested this with a later section of the course, dividing the material into 13 units. For units 1-6, we gave in-class quizzes; for 7-13, quizzes were at home. Although units 1-6 and 7-13 covered different material, we were nonetheless surprised when students' average quiz scores decreased for the take-home quizzes because they did not have a time limit and were open-book, unlike the in-class quizzes. Anonymous survey feedback showed a strong preference for quizzes in class and indications that take-home quizzes demotivated attendance and preclass watching of the videos. Thus, for analogous flipped-course designs in chemistry, we recommend an in-class quizzing strategy over take-home quizzes to positively affect engagement, learning, and attendance. Of note, this course was synchronously delivered to two groups of students at geographically distinct satellite locations.

Abstract Background Increasing the nutrient concentration of wheat grains is important to ameliorate nutritional deficiencies in many parts of the world. Proteins and nutrients in the wheat grain are largely derived from the remobilization of degraded leaf molecules during monocarpic senescence. The down-regulation of the NAC transcription factor Grain Protein Content (GPC) in transgenic wheat plants delays senescence (>3 weeks) and reduces the concentration of protein, Zn and Fe in the grain (>30%), linking senescence and nutrient remobilization. Based on the early and rapid up-regulation of GPC in wheat flag leaves after anthesis, we hypothesized that this transcription factor is an early regulator of monocarpic senescence. To test this hypothesis, we used high-throughput mRNA-seq technologies to characterize the effect of the GPC down-regulation on the wheat flag-leaf transcriptome 12 days after anthesis. At this early stage of senescence GPC transcript levels are significantly lower in transgenic GPC-RNAi plants than in the wild type, but there are still no visible phenotypic differences between genotypes. Results We generated 1.4 million 454 reads from early senescing flag leaves (average ~350 nt) and assembled 1.2 million into 30,497 contigs that were used as a reference to map 145 million Illumina reads from three wild type and four GPC-RNAi plants. Following normalization and statistical testing, we identified a set of 691 genes differentially regulated by GPC (431 ≥ 2-fold change). Transcript level ratios between transgenic and wild type plants showed a high correlation (R = 0.83) between qRT-PCR and Illumina results, providing independent validation of the mRNA-seq approach. A set of differentially expressed genes were analyzed across an early senescence time-course. Conclusions Monocarpic senescence is an active process characterized by large-scale changes in gene expression which begins considerably before the appearance of visual symptoms of senescence. The mRNA-seq approach used here was able to detect small differences in transcript levels during the early stages of senescence. This resulted in an extensive list of GPC-regulated genes, which includes transporters, hormone regulated genes, and transcription factors. These GPC-regulated genes, particularly those up-regulated during senescence, provide valuable entry points to dissect the early stages of monocarpic senescence and nutrient remobilization in wheat.