Calcium availability may explain early chriality

https://scitechdaily.com/calciums-cosmic-secret-how-a-common-mineral-may-have-sparked-life-on-earth/
Research suggests that calcium may have played
a key role in guiding the development of a
specific molecular handedness in primitive
polyesters and early biomolecules.
A new study from the Earth-Life Science
Institute (ELSI) at the Institute of Science
Tokyo has revealed an unexpected role for
calcium in the formation of life’s earliest
molecular structures. The researchers found
that calcium ions can influence the way
primitive polymers form, offering new
insight into a long-standing mystery: why
life’s molecules favor a single type of
“handedness,” or chirality.
Many molecules exist in two mirror-image
forms, like left and right hands. However,
life on Earth strongly favors one side: the
sugars in DNA are right-handed, while
proteins are made from left-handed amino
acids. This consistent preference, known as
homochirality, is critical for life but its
origin has remained unclear.
To explore how early Earth conditions might
have shaped this molecular preference, the
team studied tartaric acid (TA), a simple
molecule with two chiral centers. They found
that calcium has a major effect on how TA
molecules join to form polyesters. In the
absence of calcium, pure left- or
right-handed TA forms polymers easily, while
mixtures of both forms do not. When calcium
is present, this behavior
flips—polymerization of pure TA slows down,
but mixed solutions begin to form polymers.
“This suggests that calcium availability
could have created environments on early
Earth where homochiral polymers were favored
or disfavoured,” says Chen Chen, Special
Postdoctoral Researcher at RIKEN Center for
Sustainable Resource Science (CSRS), who
co-led the study.
...
What makes this study especially intriguing
is its suggestion that polyesters—simple
polymers formed from molecules like tartaric
acid—could have been among life’s earliest
homochiral molecules, even before RNA, DNA,
or proteins. “The origin of life is often
discussed in terms of biomolecules like
nucleic acids and amino acids,” ELSI’s
Specially Appointed Associate Professor
Tony Z. Jia, who co-led the study, explains.
“However, our work introduces an alternative
perspective: that ‘non-biomolecules’ like
polyesters may have played a critical role
in the earliest steps toward life.”
Calcium-poor settings, such as some lakes or
ponds, may have promoted homochiral polymers,
while calcium-rich environments might have
favored mixed-chirality polymers.