Optimizing the Diels–Alder (DA) reaction for aqueous
coupling
has resulted in practical methods to link molecules such as drugs
and diagnostic agents to proteins. Both normal electron demand (NED)
and inverse electron demand (IED) DA coupling schemes have been employed,
but neither mechanism entails a common multipurpose reactive group.
This report focuses on expanding the bioconjugation toolbox for cyclopentadiene
through the identification of reactive groups that couple through
NED or IED mechanisms in aqueous solution. Dienophiles and tetrazine
derivatives were screened for reactivity and selectivity toward antibodies
bearing cyclopentadiene amino acids to yield bioconjugates. Twelve
NED dienophiles and four tetrazine-based IED substrates were identified
as capable of practical biocoupling. Furthermore, tetrazine ligation
to cyclopentadiene occurred at a rate of 3.3 ± 0.5 M–1 s–1 and was capable of bioorthogonal transformations,
as evidenced by the selective protein labeling in serum. Finally,
an antibody–drug conjugate (ADC)-bearing monomethyl auristatin
E was prepared via tetrazine conjugation to cyclopentadiene. The resulting
ADC was stable and demonstrated potent activity in vitro. These findings expand the utility of cyclopentadiene as a tool
to couple entities to proteins via dual DA addition mechanisms.
Wildfires are a major source of greenhouse gases. Fires were responsible for as much as a fifth of the carbon released in 2019 from burning fossil fuels, down from about a quarter at the beginning of the century (Ciais et al., 2013;Le Quéré et al., 2018;Tian et al., 2016). While this long-term decrease in fire emissions was driven by a decline in savanna and grassland fires (Andela et al., 2017), a recent increase in forest fires has resulted in concerns about the future role of fire in the global carbon cycle. Total carbon emissions from forest fires in 2019 were 26% higher than in 2018, to 7.8 billion metric tons, the highest since 2002, according to the Global Fire Emissions Database (GFED; van der Werf et al., 2017). The unprecedented bushfires in Australia in 2019 emitted a combined 306 million metric tons of carbon dioxide (CO 2 ) in the August-December 2019 period, which is more than half of Australia's total carbon footprint in the year. Brazilian Amazon fires emitted 392 million metric tons of CO 2 in 2019 which was equivalent to more than 80% of Brazil's 2018 greenhouse gas emissions (Lombrana et al., 2020).During 2017, Canada had a record-breaking wildfire season in the province of British Columbia (BC). A total of 1.2 million hectares had burned by the end of the 2017 fire season, the largest ever in the province (Duran, 2017) and massive smoke plumes were lofted into the stratosphere in the mid-August (Torres et al., 2020).
Abstract. A series of attenuated atmospheric backscatter profiles were measured at 1572 nm by the CO2 Sounder lidar during the eight flights of the 2017 ASCENDS/ABoVE (Active Sensing of CO2 Emission over Nights, Days, & Seasons mission, Arctic Boreal Vulnerability Experiment) airborne campaign. In addition to measuring the column average CO2 mixing ratio from the signals reflected by the ground, the CO2 Sounder lidar also recorded the height-resolved attenuated atmospheric backscatter profiles beneath the aircraft. We have recently processed these vertical profiles with a 15-m vertical spacing and 1-s integration time along the flight path (~200 m) for all the 2017 flights and have posted the results at NASA Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC) for Biogeochemical Dynamics (Sun et al., 2022), https://doi.org/10.3334/ORNLDAAC/2051. This paper describes the principle of these lidar backscatter profile measurements, their data processing, and estimated signal to noise ratio.
Abstract. A series of attenuated atmospheric backscatter profiles
were measured at 1572 nm by the CO2 Sounder lidar during the eight
flights of the 2017 ASCENDS/ABoVE (Active Sensing of CO2 Emission over
Nights, Days, and Seasons, Arctic Boreal Vulnerability Experiment) airborne
campaign. In addition to measuring the column average CO2 mixing ratio
from the laser signals reflected by the ground, the CO2 Sounder lidar
also recorded the height-resolved attenuated atmospheric backscatter
profiles beneath the aircraft. We have recently processed these vertical
profiles with a 15 m vertical spacing and 1 s integration time along the
flight path (∼ 200 m) for all the 2017 flights and have posted
the results at NASA Distributed Active Archive Center (DAAC) for
Biogeochemical Dynamics https://doi.org/10.3334/ORNLDAAC/2051 (Sun et al., 2022). This paper describes the measurement principles, the
data processing technique, and the signal to noise ratios.
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