Related Experiment Video
Updated: Sep 2, 2025

Probing RNA Structure with Dimethyl Sulfate Mutational Profiling with Sequencing In Vitro and in Cells
Published on: December 9, 2022
An Ansatz for Computational Undecidability in RNA Automata
Adam J Svahn1, Mikhail Prokopenko2
1University of Sydney, Faculty of Engineering, Centre for Complex Systems, Faculty of Medicine and Health, Westmead Clinical School. adam.svahn@sydney.edu.au.
This article explores how RNA molecules can be designed to function like computer programs. By using enzymes that cut or join RNA, the authors show that these biological structures can perform complex logical tasks, eventually reaching the power of universal computers. They demonstrate that these systems face inherent logical limits, similar to the famous Liar paradox, which prevents them from solving every possible problem. However, the authors suggest that these biological systems might overcome such limits through a hierarchical process, potentially explaining how new biological functions emerge.
Area of Science:
- Theoretical computer science and RNA automata research
- Computational biology and molecular informatics
Background:
No prior work had resolved how biological polymers might emulate complex computational architectures. It was already known that nucleic acids possess the capacity for structural folding and enzymatic activity. That uncertainty drove the exploration of mapping these physical properties onto formal logic models. Prior research has shown that molecular systems can execute simple state transitions. However, the theoretical limits of such biological computing remain poorly defined. This gap motivated the current investigation into the logical boundaries of RNA-based machines. Researchers have long sought to bridge the divide between abstract computation and molecular biology. The present study addresses this by formalizing the relationship between enzymatic reactions and machine states.
Purpose Of The Study:
The aim of this study is to formalize the theoretical construction of RNA polymers into functional automata. The authors seek to bridge the gap between molecular biology and formal computational theory. They investigate how enzymatic reactions can serve as the physical foundation for logical transitions. The researchers intend to demonstrate that these biological structures can reach the complexity of universal computers. A specific problem addressed is the emergence of computational undecidability within these self-referential systems. The study explores the implications of the Liar paradox for biological machine design. The authors also aim to propose a mechanism for how these systems might overcome logical limits. This work motivates a new perspective on the evolutionary potential of biological automata.
Main Methods:
The review approach involves mapping enzymatic activities to formal computational states. Researchers categorize these systems by their memory capacity and transition rules. The study utilizes a hierarchical classification of automata, starting from finite models. The authors integrate concepts from recursive logic to analyze the behavior of these polymers. They evaluate the program-data duality within the context of molecular folding. The analysis focuses on the logical equivalence between enzymatic ligation and machine instructions. The team constructs theoretical models to demonstrate the progression toward universal computation. This methodology relies on mathematical abstractions of biological processes to define the limits of molecular logic.
Main Results:
The researchers demonstrate that RNA-based machines can achieve the computational power of a Turing machine through a 2-stack Pushdown Automaton. They show that enzymatic cleavage and ligation effectively replicate logical state transitions. The study finds that self-referential configurations inevitably lead to computational undecidability. This outcome is illustrated by the Liar paradox, which defines a hard limit on the system's logical consistency. The authors report that these boundaries are inherent to any sufficiently complex RNA-based automaton. They identify that expanding the evolutionary space allows for a hierarchical resolution of these undecidable states. This meta-systemic approach functions similarly to an oracle in classical logic. The findings suggest that these biological machines operate through a process analogous to extensible recursively generated logics.
Conclusions:
The authors propose that RNA-based machines exhibit inherent logical constraints similar to the Liar paradox. This limitation suggests that certain configurations within these biological systems remain undecidable. The researchers suggest that expanding the evolutionary space of these machines allows for hierarchical resolution. This process mirrors the function of an oracle in classical computational theory. The study posits that such resolutions serve as a mechanism for generating biological novelty. These findings imply that RNA automata could provide a framework for understanding evolutionary complexity. The authors suggest that future work should focus on the experimental realization of these theoretical models. This synthesis highlights the potential for biological systems to transcend fixed logical boundaries through meta-systemic transitions.
Frequently Asked Questions
The researchers propose that RNA automata reach computational undecidability through self-referential configurations. This state mirrors the Liar paradox, where a system's internal logic creates a boundary that prevents the determination of a definitive truth value for specific operations.
The authors utilize RNA enzymes, specifically those capable of ligation and cleavage, to serve as the physical basis for state transitions. These enzymatic reactions are mapped directly to the logical operations required for finite automata and more complex Turing-equivalent machines.
A 2-stack Pushdown Automaton (PDA) is necessary to achieve the computational power of a Turing machine. This architecture allows the system to manage memory and data access in a way that supports universal computation, unlike simpler finite-state models.
The authors employ the program-data duality to explain how RNA configurations can act as both instructions and input. This dual role enables the self-reference that triggers undecidability, allowing the system to process its own structure as data.
The researchers measure the complexity of these systems by their ability to perform logical operations, ranging from Finite Automata to Universal Pushdown Automata. They observe that increasing the number of stacks or memory capacity directly correlates with the machine's computational reach.
The authors propose that the resolution of undecidable configurations represents a mechanism for generating biological novelty. They suggest this process allows RNA systems to evolve beyond their initial logical constraints, potentially driving the emergence of new functional traits.
Related Concept Videos
RNA Interference
This process occurs naturally in cells, often through the activity of genomically-encoded microRNAs. Researchers can take advantage of this mechanism by introducing synthetic RNAs to deactivate specific genes for research or therapeutic purposes. For example, RNAi could be used...
RNA Stability
Experimental RNAi
RNA Editing
Types of RNA
Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs perform diverse functions and can be broadly classified as protein-coding or non-coding RNA. Non-coding RNAs play important roles in the regulation of gene expression in response to developmental and environmental changes. Non-coding RNAs in prokaryotes can be manipulated to develop more effective antibacterial drugs for human or animal use.
RNA...
Transcriptional Regulation: Riboswitches

