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NEWS

June 2024 ESRFnews

S h u t t e r s t o c k/K a t e r y n a K o nE S R F

How cacao absorbs cadmium

Researchers from the Université

Grenoble Alpes (UGA) and the

ESRF have discovered how cacao trees

protect themselves from the toxic

metal cadmium.

Cadmium often accumulates in

food, but it can be harmful in humans

if they are chronically exposed to it.

While there have been studies on how

it is transferred from soil to the edible

parts of crops, there has been little

research into its presence in cacao

cultivars.

The UGA scientists collected

samples from the International

Cocoa Genebank in Trinidad and

Tobago, which hosts a field collection

of some 2400 cacao genotypes, in

collaboration with the local Cocoa

Research Centre. Using nano X-ray

fluorescence on the ESRF’s ID16B

beamline and X-ray absorption on

the ID21 beamline, the team then

studied the micro- and nano-scale

compositions of different parts of

the plants, to understand why some

cultivars or varieties absorb more

cadmium than others.

They found that part of the

cadmium is stored in calcium oxalate

crystals in the roots and branches,

and it is these crystals that appeared

to be the plants’ detoxification agents

against the metal. The crystals were

also present in the leaves, although

here they did not seem to help in the

detoxification. Meanwhile, there was

a degree of cadmium combining with

sulphur in certain cells in the roots,

but not as much as in cereal crops

(Environ. Exp. Bot. 221 105713).

The EU has imposed limits to the

maximum cadmium concentration in

food, including chocolate. The latest

findings could help in the breeding

of cacao cultivars that accumulate less

of the metal.

ID14 welcomes f irst users

ID14, a brand new ESRF nuclear

resonance beamline, has welcomed

its first users in a study of osmium as a

potential anticancer compound.

Osmium compounds in different

oxidation states are currently

being explored for their potential as

anticancer agents due to their unique

chemical properties. Vladimir Arion

of the University of Vienna, together

with his colleague Gabriel Buechel,

came to the new ID14 to study osmium

in different oxidation states using a

technique known as nuclear forward

scattering (NFS). From the NFS

spectra they could extract so-called

Mössbauer parameters, which reveal

important electronic and magnetic

properties.

 “As users of the former ID18,

we are very excited about this new

beamline,” says Arion. “We’re trying

to benchmark osmium, by extracting

Mössbauer parameters and using

them for the speciation of osmium

complexes with anticancer potential in

biological tissues.”

Aleksandr Chumakov, scientist

in charge of the new ID14, says

that the aim of the upgrade and the

move from ID18 has been to pursue

spectroscopies with extreme spatial

resolutions of around 150 nm, and

perform studies of atomic dynamics

with extreme energy resolutions of

around 50 eV To achieve this the

beamline has two new instruments

a nanoscope and a spectrograph

he adds

Meanwhile ESRF scientist and

ERC grantee Ilya Kupenko will be

using ID14 beamline for research into

the lightest elements of the Earths

core employing extreme pressure

and temperature conditions as well

as a combination of stateoftheart

synchrotron Xray techniques that are

almost exclusive to the ESRF

X-ray studies help

identify which

cultivars

accumulate the

least toxic metals.

Structural data expose infertility problems

ESRF users from Sweden have

performed structural biology studies

to reveal how the coat around eggs

allows embryo development, and how

certain genetic mutations can cause

human infertility. The results could

have an impact on research into non-

hormonal contraception.

Infertility is believed to affect some

15% of couples worldwide. Some

cases are associated with mutations

in the genes that are responsible for

the formation of the egg coat, or zona

pellucida (ZP), an extracellular matrix

essential for the growth, fertilisation

and protection of the embryo until

it implants into the uterus. The

ZP consists of several proteins that

polymerise into long filaments to form

a mesh around the egg unless there are

mutations in which case the mesh may

have defects or not be there at all

Until today scientists knew that

after a sperm fuses with the egg the

egg releases an enzyme that specifically

cleaves a major ZP protein ZP2 It has

also been long known that the egg coat

becomes harder after fertilisation and

that sperm can no longer penetrate

it But the connection between these

processes has been unclear despite

their connection with the prevention

of polyspermy – a condition in which

multiple sperm fuse with an egg and

impede embryonic development.

In this work, researchers from

Karolinska Institutet in Sweden

determined different ZP2 and egg-

coat filament structures using X-ray

crystallography at the ESRF, Diamond

Light Source in the UK and BESSY II

in Germany, as well as cryo-electron

microscopy at SciLifeLab in Sweden.

They found that a cleavage of ZP2

protruding from the egg coat filament

allows it to form new interactions with

other ZP2 molecules, creating

an extensive network of cross-links

that bring filaments closer together

This stiffens the egg coat and tightens

its mesh physically preventing

additional sperm from penetrating

Cell 187 1440

For the first time we have a

molecular view of how the egg

coat changes its architecture after

fertilisation and how this affects

its function says Luca Jovine of

Karolinska Institutet This knowledge

allows us to interpret the growing

number of human ZP gene mutations

linked with female infertility

S H U T T E R S T O C K/ N A R O N G K H U E A N K A E W

Synchrotron X-rays

give the first

molecular view of

how the egg coat

changes its

architecture after

fertilisation