Spatial Separation of Right- and Left-Handed Protein Molecules in
External Magnetic Fields – A Hypothesis
IWONA MROZ
Institute of Experimental Physics
University of Wroclaw
Plac Maxa Borna 9, 50-204 Wroclaw
POLAND
Abstract: One of the most promising approaches to the problem of chiral symmetry breaking in living
organisms is based on the concept of performing chemical reactions in external, collinear electric and magnetic
fields. The author of this idea, prof. Laurence Barron suggests that the function of the electric field is to align
the molecules and then the magnetic field may induce asymmetric synthesis. An important but unanswered
questions related to this idea is whether and under which conditions collinear magnetic and electric fields could
exist on the early Earth. Prof Barron indicates that there is no need to use electric field if the molecules are
prealigned, for example on crystal surfaces.
Basing on this, we present a hypothetical scenario that may lead to spatial separation of right- and left- handed
protein or protein-like molecules in an external magnetic field. The proposed approach stresses the role of
protein spatial structures in the separation process.
We use the experimental fact that helical protein structures can be aligned in external magnetic fields without
any additional factors. Then we consider adsorption of the aligned helical molecules on solid bodies (e.g. clay
minerals) that can interact with the same magnetic field, and investigate specific reactions - protein synthesis
and decay. We show that the presented hypothetical scenario leads to spatial separation of right- and lefthanded molecules. Since big molecules with long helices are better aligned in the magnetic field than small
molecules the process seems to be more effective for proteins than for small molecules. Helical molecules
could be created in the prebiotic environment. Therefore, we suppose that the structures of primitive proteinlike molecules might play some role in chiral symmetry breaking in living organisms.
Key-words: - Chiral symmetry breaking, Protein structures, Adsorption, Magnetic field
1 Introduction
Properties of biological systems in magnetic fields
have been discussed widely at different levels of
their organization [1,2]. It is expected that static
magnetic field might play an important role in the
origin of life, especially in the origin of
biomolecular homochirality. Since it was
discovered that natural proteins and nucleic acids
contain L-amino acids and D-sugars, respectively,
many experimental and theoretical investigations of
this phenomenon have been presented [1,3]. One of
the most promising approaches was proposed by
L.D. Barron [4,5]. According to his idea, collinear
electric and magnetic fields can affect chemical
reactions and cause asymmetric synthesis. In the
presence of the mentioned fields an achiral
molecule can produce chiral enantiomers but
potential energy profiles of the reactions leading to
the enantiomers are different. In fact, the role of the
electric field is to align polar molecules to allow
electric charges to move in a plane perpendicular to
the direction of the magnetic field during the
reaction. As Barron stated, “a magnetic field alone
might induce asymmetric synthesis if the prochiral
reactant molecules are prealigned, as in a crystal,
on a surface...” [5].
The presented above ideas provoke to ask two
questions: the first question is about the factors that
could align the molecules on the early Earth: there
is no evidence for permanent coexistence of
natural, collinear electric and magnetic fields.
Secondly, homochirality is observed in living
organisms, for highly composed molecules
(proteins and nucleic acids). Such molecules are
created by many chemical reactions during their
biosynthesis. Then, the next question refers to any
properties of biomolecules that might be especially
useful to follow Barron’s idea.
Recently, it was shown experimentally [6] that
proteins having tertiary structures composed of
parallel or antiparallel helices, like cytochrome b562,
can be oriented in high static magnetic fields with
helices parallel or antiparallel to the field. The
effect depends on the length of the helices and it is
stronger for longer helices. The most natural
chemical reactions that occur for proteins are their
synthesis and decay. Below we discuss, basing on a
simple, theoretical model, the hypothetical role of
static magnetic field in chiral symmetry breaking
processes that might occur at the level of composed
molecules (proteins).
2 The Model
Consider a primitive, right- or left-handed protein
molecule. In general, such a molecule, if primitive
and composed of random amino acids, could
contain right- and left-handed structural elements,
but some excess of one handedness over the other
one should be observed. Molecules that are purely
right-handed (or left-handed) can be composed of
both L-and D-amino acids, but the amino acids of
different chirality have to alternate in a peptide
chain [8,9]. Since the molecule is primitive it can
contain mainly alanine that was one of the most
prominent amino acids in the prebiotic environment
[1]. Poly-alanines easily form helical structures.
When the molecule is synthesized or destroyed
some net displacement of electric charge takes
place during the reaction. When the electric charge
is transported along the helical structures, a
transient magnetic dipole occurs. It is parallel or
antiparallel to the axis of the helix, depending on
the direction of the displacement of the electric
charge (during protein synthesis a negative electric
charge should be transported to the C-terminus of
the molecule since this terminus is negatively
charged). Then, at the endings of helical structures
transient magnetic poles are created.
Assume that the described above molecules (rightand left-handed, mainly helical) can adsorb on
surfaces of any material in the presence of external
magnetic field (Fig.1). The material interacts with
the field so the magnetic poles of the material
occur. The molecules adsorbed on the surfaces are
oriented along the field due to their helical
structures. Adsorption of single amino acids or
primitive peptides on various materials is
frequently considered as helpful for the prebiotic
evolution [7,1]. Generally, the molecules could
adsorb on the surface using their both termini, but it
may be assumed that one way (e.g.using the Ntermini of the molecules) is energetically more
favourable. When synthesis or decay of the
adsorbed molecules takes place the transient
magnetic dipoles of the molecules interact with the
external field and with the material.
3 Results and Discussion
An example of the model situation described in
section 2 is presented in Fig.1. Right- and lefthanded molecules are adsorbed on two surfaces of
the paramagnetic material. Both surfaces are
perpendicular to the external magnetic field. The
molecules are adsorbed using their N-termini.
When the molecules are synthesized, the negative
electric charges are transported to their C-termini
during the reactions. The transient magnetic dipoles
occur and interact with the external field and the
material.
1. The molecules of different handedness
adsorbed on the top surface have their magnetic
dipoles oriented in the opposite directions.
Moreover, for the presented example, the
transient north pole of the right-handed
molecule interacts with the north pole of the
material. For the left-handed molecule an
attractive interaction between the south pole of
the molecule and the north pole of the material
is observed. Such a situation seems to be
energetically advantageous. Notice that the
right-handed molecule should be destroyed to
observe an attractive interaction since in this
case the negative charge is transported to the
N-terminus of the molecule..
2. For the molecules adsorbed on the bottom
surface the situation is opposite – the righthanded molecule is attracted by the south pole
of the material while the interaction between
the left-handed molecule and the material is
repulsive. Therefore the left-handed molecule
should be destroyed to be attracted by the
material.
The following example shows that if helical
molecules of different handedness are adsorbed in
the same way (using the same termini) on any
material that interacts with external magnetic field,
synthesis of the molecules might lead to spatial
separation of the molecules of different
handedness. Synthesis of the molecules of one
handedness is favourable when the molecules are
adsorbed on one, given surface of the material.
Energetically advantageous synthesis of the
molecules of the other handedness requires the
molecules to be adsorbed on the other surface of
the material. If all the molecules are adsorbed on
the same surface of the material, the molecules of
one handedness should be synthesised while the
molecules of the other handedness should be
destroyed to observe energetically favourable
Fig.1 Right- and left-handed helical molecules are adsorbed at two surfaces of a material that interacts with an external magnetic field.
The N-termini of the molecules are close to the surfaces. When the molecules are synthesized a negative electric charge is transported to
the C-termini of the molecules and transient magnetic poles, N and S, are created at the endings of the molecules. The magnetic poles of
the material are also shown.
interactions between the molecules and the surface.
The orientation of the molecules in the external
magnetic field depends on the length of helices,
therefore, the presented scenario might be effective
for long peptide chains and synthesis seems to be
more advantageous.
4 Conclusions and Final Remarks
The presented above hypothetical scenario,
although does not lead to net excess of one
handedness of protein molecules over the other
one, can lead to spatial separation of the molecules
of different handedness. It should be noted that:
1. The effect of spatial separation of the
molecules does not depend on the type of
the material that adsorbs the molecules
provided that the material interacts with the
external magnetic field. The molecules
should moreover be adsorbed on the
surfaces using the same termini. Different
possibilities should be considered in details
in future.
2. The only factor required to allow the
molecules to be oriented along the
magnetic field are well-shaped protein
structures – helices that could be obtained
for the most primitive prebiotic peptides.
This conclusion indicates that the role of
external magnetic field in the origin of
biomolecular homochirality might be
particularly important at the stage of
prebiotic evolution in which primitive
proteins were formed.
3. The presented model emphasizes the role
of protein conformations in the process of
spatial separation of the molecules of
different handedness. Then it might be
useful, after future, detailed development,
for those who think particularly about the
role of life processes in chiral symmetry
breaking phenomena.
4. The presented above considerations are
preliminary and need wide discussion with
biologists and, hopefully, experimental
evaluation.
Acknowledgements:
This work was supported by University of
Wroclaw, Institute of Experimental Physics (grant
no.2016/W/IFD/03).
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