Science - USA (2021-10-29)

PHOTO: KEITMA /ALAMY STOCK PHOTO

574 29 OCTOBER 2021 • VOL 374 ISSUE 6567 science.org SCIENCE

understand its nature. Whereas

the magnetism of monolayers

of chromium iodide (CrI 3 ) can

be understood in terms of out-

of-plane magnetic anisotropy,

the related material chromium

chloride (CrCl 3 ) has spins that lie

in the plane. Bedoya-Pinto et al.

used molecular beam epitaxy to

grow monolayers of CrCl 3 on gra-

phene and studied its magnetic

properties. Using x-ray magnetic

circular dichroism measure-

ments, the authors found that

monolayer CrCl 3 is a ferromag-

net, unlike bulk CrCl 3 , which is

antiferromagnetic. The scaling

of the signal in the critical region

indicated that the material

belongs to the 2D-XY universal-

ity class, distinct from the Ising

magnetism that some other 2D

magnets exhibit. —JS

Science, abd5146, this issue p. 616

LIPID TRANSPORT

Distinct mechanisms to

block transporters

Transmembrane ATP-binding
cassette (ABC) transporters
are crucial cellular machines
that move molecules small and
large across membranes. In
Gram-negative bacteria, outer
membrane biogenesis is aided by
an ABC transporter called MsbA,
which flips lipopolysaccharide
from the inner face of the cell
membrane to the periplasmic
face. Thélot et al. determined
structures of two first-generation
inhibitors bound to MsbA, TBT1
and G247, and found that they
have distinct binding modes.
Unlike most inhibitors, TBT1
triggers unproductive ATPase
activity and induces a conforma-
tion similar to substrate bound.

These structures will provide

valuable information for the

design of potential antimicrobial

drugs. The authors have already

identified a new lead compound

from virtual screening based on

the TBT1-induced conformation.

—MAF

Science, abi9009, this issue p. 580

NUCLEAR ARCHITECTURE

Nuclear organization

in the brain

The brain consists of different

cell types, neurons and glial

cells, that have different nuclear

architecture. Takei et al. used

multiplexed imaging tools to

examine the spatial arrange-

ment of more than 3000 DNA

loci, along with epigenetic marks

and gene expression patterns,

simultaneously in the same

single cells in mouse brain cor-

tex. They observed features that

are conserved across cell types,

as well as cell-type-dependent

spatial arrangements at the

megabase level. At the level of

tens of kilobases, they observed

similar single-cell chromosome

domain conformations in both

active and inactive X chromo-

somes that are averaged out

in population-based measure-

ments. —DJ

Science, abj1966, this issue p. 586

MAGNETISM

Taking the measure

of a magnet

The recent discovery of mag-

netism in two-dimensional (2D)

materials has inspired efforts to

Edited by Michael Funk

IN SCIENCE JOURNALS

RESEARCH

Rivers originating in High Mountain Asia, such as the Yangtze River, pictured here near Chongqing, China,

have experienced increased sediment loading in recent decades.

SEDIMENT TRANSPORT

Muddied waters

T

he climate of High Mountain Asia is becoming warmer and wetter. Li et al. present

data showing that rivers originating in this region have experienced large increases

in runoff and sediment fluxes over the past six decades, most dramatically since

the mid-1990s. The authors project that sediment flux from those rivers could more

than double by 2050 in the case of extreme climate change, with potentially serious

impacts on the region’s hydropower capacity, food security, and environment. —HJS

Science, abi9649, this issue p. 599