SCIENCE sciencemag.org 21 AUGUST 2020 • VOL 369 ISSUE 6506 932-B
RESEARCHPHOTOSYNTHESIS
Architectures
for light harvesting
Conversion of light energy into
chemical energy ultimately drives
most biochemistry on earth.
Photosynthetic organisms use
diverse chemical and biologi-
cal structures to harvest light in
different environmental contexts.
Croce and van Amerongen
synthesized recent structural and
spectroscopic work on photosys-
tem complexes from oxygenic
photosynthetic organisms. To
best capture light, photosystems
contain accessory light-harvest-
ing complexes harboring complex
networks of pigments that shuttle
electronic excitations toward the
core complex, which contains the
reaction center. The arrangement
of pigments and their connectiv-
ity, as seen in high-resolution
x-ray and cryo–electron micros-
copy structures, inform our
understanding of energy transfer
rates derived from spectroscopic
measurements and vice versa.
The model that emerges is one of
many parallel and unconnected
pathways for energy transfer into
the reaction center from the exte-
rior light-harvesting complexes.
—MAF
Science, this issue p. 933
ARTIFICIAL INTELLIGENCE
Making robots useful
The goal of creating generally
intelligent robots that can carry
out diverse tasks is a huge chal-
lenge. In particular, programming
how robots learn and adapt to
their surroundings quickly and
nondestructively is proving espe-
cially difficult. In a Perspective,
Pack Kaelbling discusses
advances in machine learning
based on ideas from cognitive
neuroscience. In particular, the
applications of reinforcement
learning, where a valued outcome
is reinforced, and how robots
can be taught general lessons to
apply to numerous situations are
discussed. —GKA
Science, this issue p. 915
BIOMEDICINE
Remodeling senescent
blood vessels
The retina is a thin layer of
nervous tissue at the back of
the eye that transforms light
into neuronal signals. The retina
is essential for vision and is
supported by networks of blood
vessels. In diabetic retinopathy,
a common cause of vision loss,
these microvessels degener-
ate and regrow in an aberrant
manner. Such degeneration
and regrowth can compromise
the functioning of retinal nerve
cells. Binet et al. observed that,
after rapid proliferation, vascular
endothelial cells in diseased
blood vessels engaged molecu-
lar pathways linked to cellular
senescence (see the Perspective
by Podrez and Byzova).
Senescent vascular units
summoned an inflammatory
response in which neutrophils
extruded neutrophil extracellular
traps onto diseased vessels to
remodel them. This endogenous
repair mechanism promoted the
elimination of senescent blood
vessels and could lead to benefi-
cial vascular remodeling. —SMH
Science, this issue p. 934;
see also p. 919CANCER IMMUNOLOGY
BTN3A1 governs
antitumor responses
T lymphocytes are immune cells
that can be activated through
their gamma delta (gd) or alpha
beta (ab) receptors. Both T cell
types are found in human
cancers, but current immuno-
therapies do not harness their
coordinated antitumor activity.
Payne et al. found that BTN3A1
and BTN2A1, two members
of the butyrophilin family of
proteins, partner to activate
the most abundant subset of
gd T cells in peripheral blood.
Antibodies targeting BTN3A1
redirect gd T cells to attack
cancer cells while also increas-
ing the activity of tumor-specificab T cells. Thus, the killing of
established tumors by different
T cell subsets can be achieved
through BTN3A1 targeting and
may provide new strategies for
cancer immunotherapy. —PNK
Science, this issue p. 942CORONAVIRUS
Protective neutralizing
antibodies
Antibodies produced by survi-
vors of coronavirus disease 2019
(COVID-19) may be leveraged
to develop therapies. A first
step is identifying neutralizing
antibodies, which confer strong
protection against severe acute
respiratory syndrome corona-
virus 2 (SARS-CoV-2). Rogers
et al. used a high-throughput
pipeline to isolate and character-
ize monoclonal antibodies from
convalescent donors. Antibodies
were selected for binding to
the viral spike protein, which
facilitates entry into host cells
by binding to the angiotensin-
converting enzyme 2 (ACE2)
receptor. Most isolated antibod-
ies bound to regions of the spike
outside of the receptor binding
domain (RBD); however, a larger
proportion of the RBD-binding
antibodies were neutralizing,
with the most potent binding
at a site that overlaps the ACE2
binding site. Two of the neutral-
izing antibodies were tested in
Syrian hamsters and provided
protection against SARS-CoV-2
infection. —VV
Science, this issue p. 956ORGANIC CHEMISTRY
Targeting a distant
C–H bond
Enzymes often have intricate
active sites that bind one portion
of a molecule to orient a distant
portion for optimal reactivity.
This type of orienting effect has
proven a much greater challenge
for small-molecule catalysts.
Reyes et al. now report a simple
ligand that can simultaneouslybind to an iridium catalyst
through a pyridine substitu-
ent while positioning an amide
or ester reactant through a
hydrogen-bonding urea. As a
result, the catalyst exclusively
borylates the site three carbons
away from the carbonyl, with a
second chiral ligand inducing
high enantioselectivity. —JSY
Science, this issue p. 970SURFACE CHEMISTRY
Modifying MXene
surfaces
Unlike graphene and transi-
tion-metal dichalcogenides,
two-dimensional transition-
metal carbides (MXenes) have
many surface sites that can be
chemically modified. Etching of
the aluminum layer of a parent
MAX phase Ti 3 AlC 2 layered
material with hydrofluoric
acid leads to the MXene Ti 3 C 2
with various surface termina-
tions. Molten salts can achieve
uniform chloride terminations,
but these are difficult to further
modify. Kamysbayev et al. show
that etching of MAX phases in
molten cadmium bromide leads
to bromide-terminated MXenes
that can then be substituted
with oxygen, sulfur, selenium,
tellurium, and NH groups as well
as with vacancy sites. The sur-
face groups can alter electronic
transport. For example, the Nb 2 C
MXenes exhibit surface group–
dependent superconductivity.
—PDS
Science, this issue p. 979NEUROSCIENCE
A present-day atlas
of the human brain
Defining brain regions and
demarking their spatial extent
are important goals in neu-
roscience. A modern map of
the brain’s cellular structure,
a cytoarchitectonic atlas,
should provide maps of areas
in three dimensions, integrate
recent knowledge about brainEdited by Michael FunkALSO IN SCIENCE JOURNALS
Published by AAAS