Bicistronic Design for Precise and Reliable Gene Expression

Despite having progressed extensively in the field of synthetic biology in terms of DNA synthesis, analysis and transplanting, we still cannot reliably, quantitatively measure expression of new genetic constructs. We engineered a biobrick compatible expression cassette to control transcription and translation initiation which can be reused in new genetic contexts. Previous research has shown that the Bicistronic design have much lesser variations in expression with varying genes of interest as compared to the regular monocistronic design.(Mutalik, Endy, Guimaraes, Cambray, Lam, Juul, Tran & Paull, 2013) The Bicistronic design(BCD) consists of two Shine-Dalgarno sequences in its translation element which when combined with indiscriminate gene of interests are known to reliably express within twofold of the relative target expression window. The expression levels can be controlled with the sequence of the Shine Dalgarno and promoter sequences. The four original BCDs driving Red fluorescent protein were chosen from V.Mutalik’s and D.Endy’s designs and they have very low, low, medium and high expressions. The fluorescence expression was measured using flow cytometry. The parts were made biobrick compatible using the RFC25 assembly standard. Results from the biobrick BCDs were similar as the original BCDs, which implies that scars from the restriction sites did not affect the expression levels. These parts will be submitted to partsregistry and made available to the public to be reused by other research groups

Coronal Heating as Determined by the Solar Flare Frequency Distribution Obtained by Aggregating Case Studies

Flare frequency distributions represent a key approach to addressing one of the largest problems in solar and stellar physics: determining the mechanism that counter-intuitively heats coronae to temperatures that are orders of magnitude hotter than the corresponding photospheres. It is widely accepted that the magnetic field is responsible for the heating, but there are two competing mechanisms that could explain it: nanoflares or Alfv\'en waves. To date, neither can be directly observed. Nanoflares are, by definition, extremely small, but their aggregate energy release could represent a substantial heating mechanism, presuming they are sufficiently abundant. One way to test this presumption is via the flare frequency distribution, which describes how often flares of various energies occur. If the slope of the power law fitting the flare frequency distribution is above a critical threshold, $\alpha=2$ as established in prior literature, then there should be a sufficient abundance of nanoflares to explain coronal heating. We performed $>$600 case studies of solar flares, made possible by an unprecedented number of data analysts via three semesters of an undergraduate physics laboratory course. This allowed us to include two crucial, but nontrivial, analysis methods: pre-flare baseline subtraction and computation of the flare energy, which requires determining flare start and stop times. We aggregated the results of these analyses into a statistical study to determine that $\alpha = 1.63 \pm 0.03$. This is below the critical threshold, suggesting that Alfv\'en waves are an important driver of coronal heating.Comment: 1,002 authors, 14 pages, 4 figures, 3 tables, published by The Astrophysical Journal on 2023-05-09, volume 948, page 7