472 29 APRIL 2022 • VOL 376 ISSUE 6592 science.org SCIENCE
PHOTO: MIRCEAX/ISTOCK.COMRESEARCH | IN SCIENCE JOURNALS
have a different mobility; thus,
when the material is squeezed,
it causes an ionic gradient
that generates voltage. The
authors demonstrate sev-
eral potential applications,
including a piezoionic skin and
peripheral nerve stimulation,
to demonstrate the possibil-
ity of self-powered piezoionic
neuromodulation. —MSL
Science, aaw1974, this issue p. 502
CANCER
Self-inflicted damage
protects tumors
Genotoxic treatments, such
as radiation and some chemo-
therapy drugs, are a mainstay of
cancer therapy, but they often
fail to fully destroy tumor cells.
Normal cells can protect them-
selves from genotoxic insults
by activating the G 1 cell cycle
checkpoint, but this checkpoint
is often dysfunctional in tumors.
By contrast, Larsen et al.
discovered that tumor cells can
activate a nuclease that causes
limited induction of DNA breaks
at specific sites, which is coordi-
nated with the process of DNA
break repair. These self-inflicted
DNA breaks trigger the G 2 cell
cycle checkpoint, preventing
tumor cells from cycling and
protecting them from death due
to treatment-induced DNA dam-
age. —YN
Science, abi6378, this issue p. 476
DYNAMIC GENOME
Fleeting chromatin loops
The genome is organized
into three-dimensional (3D)
domains that are widely
thought to be stable, fully
looped structures, although
this organization has not been
directly observed in living cells.
Gabriele et al. report the direct
visualization of chromatin
looping in living cells and used
Bayesian inference to quan-
tify looping dynamics. Loops
were found to be both rare and
short-lived, overturning static
models of looping. Instead of
being fully looped, 3D genome
domains existed overwhelm-
ingly in partially folded
SCIENCE EDUCATION
Loading the dice for
active learning
The benefits of active learning
have been well established, but
traditional lecture-orientated
approaches are still the norm
at many institutions. Yik et al.
implemented large-scale data
collection (from 2382 instructors)
to empirically test the relative
association of 17 malleable fac-
tors that influence the uptake of
active learning. Using regression
analysis and multilevel modeling,
the team found that contextual
factors (e.g., classroom setup)
and personal contexts (e.g.,
participation in scholarship of
teaching and learning activities)
were associated with a decrease
in the percentage of time spent
lecturing. Broad recommen-
dations for sustaining active
learning strategies are discussed,
including constructing classroom
spaces that support active learn-
ing, incentives for professionaldevelopment, and meaning-
ful recognition of scholarship
of teaching and learning work
accomplished by instructors.
—MMc
Int. J. STEM Educ. 9 , 15 (2022).NONCOVALENT POLYMERS
Photocontrol fluttering
controls polymerization
Most methods for pausing
and resuming polymerization
reactions act at the growing
chain. Aoki et al. show how light-
induced conformer changes of a
monomer switch the kinetics of a
supramolecular polymerization.
A cyclooctatetraene derivative,
formed from fused thiophene
molecules that bear hydrogen-
bonding side chains, has a chiral
nonplanar central ring that can
racemize through a fluttering
motion. This molecule polymer-
izes in the dark as alternating R
and S monomers but not during
prolonged ultraviolet irradiation.configurations. This more
dynamic view of 3D genome
domains may ultimately allow
a deeper understanding of why
the disruption of some domains
and loops causes dysregulation
of gene expression in disease.
—DJ
Science, abn6583, this issue p. 496GRAVITATIONAL WAVES
A gamma-ray pulsar
timing array
After galaxies merge, the super-
massive black holes (SMBHs)
at their centers are expected
to form binaries that emit
gravitational waves at nano-
hertz frequencies. Numerous
SMBH binaries throughout the
Universe should combine to
produce a gravitational wave
background. Existing searches
for this signal use radio obser-
vations of pulsars as sensitive
clocks and look for small shifts
in the pulse timings. The Fermi-
LAT Collaboration implemented
a pulsar timing array using
gamma rays and achieved a
sensitivity close to that of the
radio approaches. The results
set an independent upper
limit on the gravitational wave
background, which is subject to
different noise sources. —KTS
Science, abm3231, this issue p. 521ORGANIC CHEMISTRY
Carbon excision
Quinolines and indoles are both
very common core motifs in
drug molecules. Because they
differ by just a single carbon
in their ring frameworks, it
would be useful to interconvert
them during structure-activity
relationship studies. However,
aromatic stabilization in these
compounds makes that process
difficult. Woo et al. report that
narrow-wavelength irradia-
tion of quinoline N-oxides in
the near-ultraviolet range
followed by acid treatment
cleanly excises a ring carbon
to produce an indole, avoiding
secondary photoproducts that
were previously observed using
broadband light. —JSY
Science, abo4282, this issue p. 527IN OTHER JOURNALS Edited by^ Caroline Ash
and Jesse SmithURBAN ECOLOGYEmbracing the nightlife
S
ome animals expertly adapt to urban
environments, often by changing
their behavior. Gallo et al. investigated
whether mammals in cities change the
timing of their activities to earlier or
later in the day. Using images from camera
traps in 10 US cities, the authors analyzed
how mammal activity changed across
gradients in human population density,
impervious surface cover, temperature, and
vegetation. Coyotes were more nocturnal in
more populated areas. Common omnivore
and herbivore species changed their activity
with urbanization, although some became
more nocturnal and some less. Coyotes
and red foxes avoided hot temperatures by
increasing activity at dusk. Such temporal
shifts can allow animals to exploit resources,
avoid conflict, and navigate urban environ-
ments. —BEL eLife 11 , e74756 (2022).
Urbanized areas attract certain wild species,
many of which have changed their behavior
to exploit new opportunities, like this raccoon
foraging in a garbage bin at night.