Science - USA (2022-04-22)

STRUCTURAL BIOLOGY

The molecular

effects of oxytocin

Oxytocin is a signaling peptide

that binds to a G protein–

coupled receptor to regulate

diverse physiological processes

in humans. Oxytocin is per-

haps best known for its roles in

causing uterine contractions

during labor, initiating nurtur-

ing maternal behavior, and

affecting the mother’s ability to

nurse. Meyerowitz et al. report a

structural analysis of the native

state of the oxytocin receptor

bound to oxytocin and a model G

protein. The structure, together

with functional assays, shows

SCIENCE science.org 22 APRIL 2022 • VOL 376 ISSUE 6591 365

PHOTO: MAURUSONE/ISTOCK.COM

QUANTUM SENSING

Spatial sensing

with hydrogen

The coupling of coherent

quantum systems to the sur-

rounding environment can be

used to create highly sensitive

sensors, but many surface-

based implementations,

such as nitrogen vacancies in

diamond, have limited spatial

resolution. Wang et al. created

a quantum sensor with high

spatial sensitivity by using the

electric field from a scanning

tunneling microscope tip to

confine a hydrogen molecule

on copper nitride islands

grown on a copper surface.

Femtosecond-pulse terahertz

spectroscopy was used to

follow the coherence of the

two-level system created by dif-

ferent adsorption geometries.

The temporal oscillations and

decoherence in the superpo-

sition state showed spatial

variations at the sub-angstrom

scale. —PDS

Science, abn9220, this issue p. 401

BIOMATERIALS

Designing degradable

dressings

Synthetic scaffolds are an

attractive option for dressings

to treat skin wounds because

they are shelf-stable, have

tunable and defined chemical

compositions, and are more

affordable than naturally

derived scaffolds or cell-based

dermal substitutes. Patil et al.

investigated the role of scaffold

hydrophilicity in polythioketal-

based polyurethane (PTK-UR)

foam scaffold resorption and

promotion of tissue regen-

eration in wound healing. They

discovered that hydrophilic

scaffolds with seven ethyl-

ene glycol units between the

thioketal bonds in the polymer

backbone exhibited optimal

reactive oxygen species–

dependent degradation and

porcine skin wound healing,

including ischemic flap exci-

sional wounds. These results

support further investigation

of PTK-UR formulations as

that binding of oxytocin disrupts

the TM7 helix in the receptor,

and this effect is required for

full activation. The authors also

identified a cation-coordinating

residue that makes activation of

the oxytocin receptor dependent

on magnesium. —VV

Nat. Struct. Mol. Biol. 29 , 274 (2022).

CELESTIAL MECHANICS

How did Ceres get there?

The dwarf planet Ceres is the

largest object in the asteroid

main belt. It has an ice-rich

composition, which suggests

that it originally formed in the

outer Solar System. Ribeiro de

Sousa et al. performed orbital

Edited by Caroline Ash

and Jesse Smith

IN OTHER JOURNALS

MATERIALS SCIENCE

Scorpion-inspired strain sensors

M

ost strain sensors are designed to be highly sensitive to

movement in one direction by using long uniaxial sen-

sor elements while being insensitive to motion in other

directions. To compensate for their poor vision, scorpi-

ons have developed powerful vibration-sensing organs

called sensillum on their walking legs. Liu et al. drew on these as

inspiration for designing flexible, highly sensitive omnidirectional

strain sensors. A film with cut, curved grooves was placed on a

poly(dimethylsiloxane) layer and coated with silver nanoparticles

so that the grooves formed around a central ring. This ensures

that the stress concentration is not at the focus of the grooves

and that some of the segments will deform maximally to gener-

ate omnidirectional strain sensing. —MSL

Adv. Mat. 10.1002/adma.202200823 (2022).

Scorpions, like the forest scorpion (Heterometrus petersii) pictured,

have flexible strain-sensors that have inspired human-engineered versions.

alternatives to commercially

available wound matrices. —CC

Sci. Transl. Med. 14 , eabm6586

(2022).

OPTOELECTRONICS

Probing interlayer

excitons

Stacking of atomically thin

layers of van der Waal materials

gives rise to a wealth of exotic

transport properties. Controlling

the twist angle and stacking

sequence can yield heterostruc-

tures exhibiting magnetism,

superconductivity, and the

generation of interlayer excitons

(electron-hole pairs across the

layers). Barré et al. developed

an electromodulation spectro-

scopic technique with which

the detailed band structure

can be determined, providing a

key to understanding how the

exotic optoelectronic transport

properties develop in these het-

erostructure materials. —ISO

Science, abm8511, this issue p. 406

IMAGING TECHNOLOGY

Portable MRI

for ischemic stroke

Magnetic resonance imaging

(MRI) offers unparalleled soft

tissue contrast for diagnostic

imaging, but the instrumentation

is bulky and cannot be trans-

ported. Portable MRI systems

could be lower cost and useful

in trauma settings or at the

bedside, especially in situations

where time is of the essence.

Portability, however, comes at

the cost of lower magnetic field

strengths, motion artifacts,

and associated performance

loss. Successful deployment

of point-of-care MRI in such

environments represents a

formidable engineering chal-

lenge. Yuen et al. demonstrate

the feasibility of this technology

with sufficient image quality and

contrast for brain imaging (see

the Focus by Basser), providing

evidence for the usefulness of

this technology in the context of

assessing ischemic stroke. — LSB

Sci. Adv. 10.1126/sciadv.abm3952,

10.1126/sciadv.abp9307 (2022).