RESEARCHSCIENCE sciencemag.org 3 JANUARY 2020 • VOL 367 ISSUE 6473 38-C
FLUORESCENT PROTEINS
Electrostatics guide
chromophore twist
Photoisomerization—the
twisting of bonds in a molecule
in response to absorption of
light—is exploited in biology to
sense light and can influence
the photophysical properties
of fluorescent proteins used in
imaging applications. Romei et
al. studied this behavior by intro-
ducing unnatural amino acids
into the photoswitchable green
fluorescent protein Dronpa2,
thus systematically altering the
electronic properties of the chro-
mophore (see the Perspective
by Hu et al.). Crystal structures
and spectroscopic analyses of a
series of these variants support a
model in which the electrostatic
interactions between the chro-
mophore and its environment
influence the barrier heights for
twisting around different bonds
during photoisomerization. These
insights may guide future design
of photoswitchable proteins with
desired properties. —MAF
Science, this issue p. 76;
see also p. 26
CANCER
A movement orchestrated
by DNA damage
Doxorubicin is a commonly used
therapeutic that kills cancer
cells by inducing genotoxic
stress. Harvey et al. found
that treatment of cancer cells
with clinically relevant doses
of doxorubicin promoted the
phosphorylation of the transla-
tion factor eIF2a, which, rather
than inhibiting protein syn-
thesis as might be expected,
led to increased migration.
Inhibiting eIF2a phosphoryla-
tion with a U.S. Food and Drug
Administration–approved drug
restricted doxorubicin-induced
cell migration. —WW
Sci. Signal. 12 , eaaw6763 (2019).
SUPERCONDUCTIVITY
Manipulating the gap
Cuprate superconductors
typically have a large amount
of spatial inhomogeneity, partly
stemming from the inhomoge-
neity of the chemical doping
process. In particular, the size of
the spectroscopic gap can vary
widely across a single sample.
Massee et al. used the tip of a
scanning tunneling microscope
to manipulate atoms on the
surface of a member of the
Bi 2 Sr 2 CaCu 2 O8+x cuprate family.
Moving bismuth atoms up or
down caused adjacent atoms to
shift laterally, leading to revers-
ible local changes in the size of
the gap. It is expected that the
technique can be used to probe
the influence of the local lattice
on the electronic states of other
correlated materials. —JS
Science, this issue p. 68Published by AAAS