Chirality switching in biomineral structures

August 01, 2018

Researchers at McGill University have discovered a mechanism by which helical biomineral structures can be synthesized to spiral clockwise or counterclockwise using only either the left-handed or right-handed version of a single acidic amino acid.

Marc McKee, a professor in McGill's Faculty of Dentistry and the Department of Anatomy and Cell Biology, and his team, along with collaborators from Johns Hopkins University, shed light on how certain biological structures - like terrestrial and marine snail shells - can have both clockwise and counterclockwise spirals, not only within the same species, but also within the shell of an individual organism.

In an article published online in Science Advances, Professor McKee and his team constructed chiral (see "What is chirality?" description box below) helicoidal structures of the biomineral calcium carbonate (a mineral typically found in shells) by the simple addition of specific amino acids.

What is chirality?

Have you ever heard of Jeremy the snail? He became famous in 2016 because unlike most of his fellow brown garden snails, his shell spirals counter-clockwise. This anomaly made it hard for British researchers studying Jeremy to find him a mate.

Why is the spiral of Jeremy's shell so important? Because it's one example of a widespread phenomenon found throughout nature: chirality. Objects that are mirror images of each other are considered to be chiral if it's impossible to superimpose them on each other. That is, whichever way you turn them, they will never be the same. Jeremy's shell, with its counterclockwise rotation, cannot be superimposed onto the clockwise-rotating shells of the vast majority of his fellow snails.

Much like our hands are non-superimposable images of themselves, many molecules are also chiral. Amino acids, the building blocks of protein, have chiral forms, that is, where one form is left-handed and the other form is right-handed.

Scientists originally hypothesized that biological helical structures - such as snail shells or the twisting tooth of the narwhal - could be explained by the actions of chiral molecules that caused them to spiral clockwise (left-handed) or counterclockwise (right-handed). In nature, however, where both rotations can sometimes be found, this can't be the case because only left-handed amino acids and biomolecules are generally involved in biological processes.

Remarkably, they could also make the helicoids turn clockwise or counterclockwise by simply using only either the left-handed or right-handed version of the amino acids aspartic acid and glutamic acid - these being abundant in proteins that guide biomineralization processes in many organisms.

"This work provides key information towards understanding how organisms can have biomineralized structures rotating in opposite directions," says McKee, senior author of the study. "Our findings also give insight into pathologic chiral malformations that might arise in human otoconia, structures in the inner ear whose normal functioning maintains balance by gravity sensing and by detecting linear acceleration. Our work predicts how pathologic chiral malformations might arise in human otoconia and could one day be used to develop therapies for vertigo (loss of balance) based on this understanding".
-end-


McGill University

Related Amino Acids Articles from Brightsurf:

Igniting the synthetic transport of amino acids in living cells
Researchers from ICIQ's Ballester group and IRBBarcelona's Palacín group have published a paper in Chem showing how a synthetic carrier calix[4]pyrrole cavitand can transport amino acids across liposome and cell membranes bringing future therapies a step closer.

Microwaves are useful to combine amino acids with hetero-steroids
Aza-steroids are important class of compounds because of their numerous biological activities.

New study finds two amino acids are the Marie Kondo of molecular liquid phase separation
a team of biologists at the Advanced Science Research Center at The Graduate Center, CUNY (CUNY ASRC) have identified unique roles for the amino acids arginine and lysine in contributing to molecule liquid phase properties and their regulation.

Prediction of protein disorder from amino acid sequence
Structural disorder is vital for proteins' function in diverse biological processes.

A natural amino acid could be a novel treatment for polyglutamine diseases
Researchers from Osaka University, National Center of Neurology and Psychiatry, and Niigata University identified the amino acid arginine as a potential disease-modifying drug for polyglutamine diseases, including familial spinocerebellar ataxia and Huntington disease.

Alzheimer's: Can an amino acid help to restore memories?
Scientists at the Laboratoire des Maladies Neurodégénératives (CNRS/CEA/Université Paris-Saclay) and the Neurocentre Magendie (INSERM/Université de Bordeaux) have just shown that a metabolic pathway plays a determining role in Alzheimer's disease's memory problems.

New study indicates amino acid may be useful in treating ALS
A naturally occurring amino acid is gaining attention as a possible treatment for ALS following a new study published in the Journal of Neuropathology & Experimental Neurology.

Breaking up amino acids with radiation
A new experimental and theoretical study published in EPJ D has shown how the ions formed when electrons collide with one amino acid, glutamine, differ according to the energy of the colliding electrons.

To make amino acids, just add electricity
By finding the right combination of abundantly available starting materials and catalyst, Kyushu University researchers were able to synthesize amino acids with high efficiency through a reaction driven by electricity.

Nanopores can identify the amino acids in proteins, the first step to sequencing
While DNA sequencing is a useful tool for determining what's going on in a cell or a person's body, it only tells part of the story.

Read More: Amino Acids News and Amino Acids Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.