We live in a world of contradictions, and the differentiation between quantum physics and classical physics, remains as one of the biggest examples of this. Now the term “quantum” may seem over-used at times, and quantum biology on first glance, may seem like something made up just with buzzwords.
But the reality is that quantum biology has been shown in both theory and experiments, to potentially hold the keys to various different biological phenomena we have recorded. This field is dealing with the smallest interactions within the building blocks and the instructions for life itself.
What is Quantum Physics, and how does it play into Biology?
In a nutshell, quantum physics deals with the sometimes logic-defying functions of the smallest particles that we know of. These functions are more often than not, based off of mathematical chance and probability, but nevertheless come up again and again in empirical evidence across fields. In quantum physics, the main quantity that we can use to determine all these probabilities is the wave function. Since quantum physics deals specifically with the micro-world, it only makes sense that biology, which is based off of chemical functions and thus, particle physics, is effected by quantum mechanics in some way or another.
Scientists are rapidly finding new cases of quantum phenomenon acting in many different biological processes. These include instances of: Quantum superposition in photons during photosynthesis, and quantum tunneling in electrons within enzymes acting as catalysts for reactions, between organic compounds.
With all these cases of quantum mechanics playing significant roles in biological functions, the question of how could this effect our own DNA now comes up, which is an emerging field that scientists all over the world are starting to pick apart.
This topic has fascinated me as a student who has a burning passion for genomics and DNA research, and I will be covering specific examples more in depth as I build my knowledge of these specific functions. In this article series, I will be focusing on one main quantum phenomena and their effects on DNA structure: Quantum Tunneling. Our focus in this article will be Quantum Tunneling in DNA Nitrogenous Bases.
Quantum Tunneling: DNA Rungs’ Hydrogen Bonds
A) What is Quantum Tunneling?
Quantum tunneling uses the principle of duality, which states that all matter also experiences its own unique wave, that also reveals information about the state of that matter. This matter wave is more significant for small matter such as electrons, as they experience larger matter waves, and is less significant for anything we know in the macroscale, with smaller matter wavelengths.
Before jumping into the awesome quantum tunneling phenomena, there’s a few ground rules to keep in mind:
- For any chemical reaction to occur, the reactants must possess a certain level of energy for anything to happen, dubbed the “Activation Barrier”
- An activation barrier also exists for electrons / protons when trying to jump between orbital shells or jumping the atom itself respectively.
- Classical Physics states that: it is impossible to lack the energy required to pass the activation barrier, and still have a reaction or be able to jump out of the orbital/atom
- One part of a Quantum Physics principle: the Heisenberg Uncertainty principle, states that you can never be sure of the probability a quantum phenomena, to equal 0
With that in mind, Quantum Tunneling uses the principle of matter waves to break rules 1–3. Basically, the matter wave of these particles will collide with the activation energy barrier, and for the most part, get absorbed if it lacks energy. However according to mathematical probability and the Heisenberg Uncertainty Principle, there’s a probability, although very small, that the matter wave will be able to pass through the energy barrier! This is more than just a theoretical probability, as we observe quantum tunneling happening all around us, and some startups are now using quantum tunneling in genome sequencing technology.
A good way to picture this is to imagine yourself, a ghost version of yourself, and a brick wall. In this situation, everybody rolls around with their own ghost body, along with their regular body. Here you represent a particle, and your ghost represents the particle’s matter wave.
You yourself would never be able to go through this brick wall on your own power, no matter how hard you tried.
Your ghost has a similar issue with the brick wall, and it would bounce back if it tried going through the wall, most of the time. Very rarely, it will be able to go through the brick by just probability. When this happens, you have effectively bypassed the brick wall, because of your ghost bypassing it.
B) Nitrogenous Bases and Quantum Tunneling’s Effect
DNA is made of numerous repeating substructures called Nucelotides. These nucleotides are built off of three main parts: Phosphate groups, Deoxyribose Sugars, and Nitrogenous Bases. For the purpose of this article, we will only be looking at the nitrogenous bases.
Nitrogenous bases make up the rungs of the DNA double helix, which are crucial to conjoining the opposite strands of the double helix together. Nitrogenous bases in DNA conjoin in 2 specific, and exclusive pairings, via hydrogen bonding. The two nitrogenous base pairings are: Adenine and Thymine / Cytosine and Guanine, which are are abbreviated as AT, and CG pairs.
At the core of the hydrogen bonds between AT or CG compounds, there lies two interesting probabilities involving quantum tunneling:
- The electrons/protons within one of the atoms can jump the activation energy barrier of its own respective molecule, and end up on the adjacent nitrogenous base.
- An entire atom within a nitrogenous pair, can bypass the activation energy barrier of the hydrogen bond, and thus release itself from the base pair entirely.
Both of these cases have been observed numerous times, and have huge implications for potential errors in DNA transcription. These instances are usually observed via classical physics, in which radiation energy spikes the particles and/or atoms with the energy needed to bypass these activation barriers. This is a reason why radiation energy is often correlated with harmful mutations.
However with quantum tunneling, just as with radiation energy exposure, altered base pairs can have misplaced electrons/protons which tunneled from one nitrogenous base to the other, or base pairs with straight up missing atoms due to tunneling. All of the instances can result in errors in DNA code when being transcribed, or leave unstable genomes with high potential for mutation.
Why, you ask?
DNA transcription involves the cutting of nitrogenous base pairs’ hydrogen bonds in half, and then installing new nucleotides with the corresponding nitrogenous bases, to the previously cut nitrogenous bases.
However, base pairs with effects of quantum tunneling (Ex: nitrogenous bases that have atoms with missing protons/electrons), can be translated along with these effects. This can lead to a transcription error in DNA, and potential for a mutation. This branch of discovery is extremely new and in the infancy stage, but we do know that this has potential to transcribe altered nitrogenous bases, and cause genome instability. Genome instability is the high frequency of which a genome lineage can get mutations.
What does this all mean?
The implications of how these quantum phenomena are huge, especially since have come to acceptance that mutations that spearhead evolution are random. The probability-based phenomena of quantum tunneling on DNA nucleotides can be one of the contributing factors to this randomness, as well as to some potential genetic diseases based off of the genome instability that tunneling can cause.
Quantum roles on DNA structure can play out in numerous ways, and imply numerous things. Very little right now in this field of research is known, but yet it is undoubtedly a major step in preventing certain genetic diseases from start, as we can slowly discover more ways that cause, and soon maybe can reduce, genome instability.
Big shoutout to my friend, a quantum mechanics/mathematics enthusiast, and fellow high school student: Jack Ceroni, for helping with the quantum explanation!
Quantum Tunnelling to the Origin and Evolution of Life: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3768233/
Did Enzymes Evolve to Capitalize on Quantum Tunneling?
FIGURE 1: The activation energy barrier separates reactants from products. The top of the barrier is the transition…
Quantum entanglement between the electron clouds of nucleic acids in DNA: https://arxiv.org/abs/1006.4053