Papers
Topics
Authors
Recent
Search
2000 character limit reached

Determining Molecular Complexity using Assembly Theory and Spectroscopy

Published 24 Feb 2023 in q-bio.QM, physics.bio-ph, and physics.chem-ph | (2302.13753v2)

Abstract: Determining the complexity of molecules has important applications from molecular design to understanding the history of the process that led to the formation of the molecule. Currently, it is not possible to experimentally determine, without full structure elucidation, how complex a molecule is. Assembly Theory has been developed to quantify the complexity of a molecule by finding the shortest path to construct the molecule from building blocks, revealing its molecular assembly index (MA). In this study, we present an approach to rapidly and exhaustively calculate the MA of molecules from the spectroscopic measurements. We demonstrate that molecular complexity (MA) can be experimentally estimated using three independent techniques: nuclear magnetic resonance (NMR), tandem mass spectrometry (MS/MS), and infrared spectroscopy (IR), and these give consistent results with good correlations with the theoretically determined values from assembly theory. By identifying and analysing the number of absorbances in IR spectra, carbon resonances in NMR, or molecular fragments in tandem MS, the molecular assembly of an unknown molecule can be reliably estimated from experimental data. This represents the first experimentally quantifiable approach to defining molecular assembly, a reliable metric for complexity, as an intrinsic property of molecules and can also be performed on complex mixtures. This paves the way to use spectroscopic and spectrometric techniques to unambiguously detect alien life in the solar system, and beyond on exoplanets.

Summary

  • The paper introduces a novel spectroscopic method that infers the molecular assembly index (MA) from NMR, IR, and MS data.
  • The study employs a recursive algorithm to map assembly pathways, linking substructural motifs to distinctive spectroscopic signals.
  • This integrated approach enhances accuracy in assessing molecular complexity and aids biosignature detection in astrobiological research.

Introduction

In the pursuit to quantify molecular complexity, Assembly Theory has been at the forefront, offering a methodology to gauge the intricacies of a molecule's structure without fully delineating its layout. The molecular assembly index (MA) encapsulates this complexity by mapping the shortest pathway to synthesize a molecule from simpler building blocks. In the recent advancement of this field, researchers have innovatively leveraged spectroscopic techniques, namely Nuclear Magnetic Resonance (NMR), Infrared Spectroscopy (IR), and tandem Mass Spectrometry (MS/MS), to estimate the MA of molecules, facilitating rapid complexity quantification directly from experimental data. This approach holds profound implications, particularly in biosignature detection, offering a new lens to examine life’s chemical signatures within the cosmos.

Spectroscopic Techniques to Infer Molecular Complexity

The recent contributions in this domain present an experimental paradigm to estimate molecular complexity via independent spectroscopic methods. Through detailed correlation analysis, researchers have shown that molecular complexity can be deduced using peak counts from the aforementioned techniques. For instance, the number of absorbances within IR spectra's fingerprint region or carbon resonances in NMR spectra, along with molecular fragments in tandem MS, renders an estimable MA. The investigators have elucidated that unique substructural motifs, which are pivotal in computing MA, can be closely associated with spectroscopic signals corresponding to distinct bonding or elemental environments within a molecule.

Algorithmic Adaptation and Recursive Mass Spectrometry Analysis

Complementing the spectroscopy findings, the study has introduced a recursive algorithm which utilizes MS data to construct a hierarchical tree structure reflecting the molecular assembly pathway. Complex molecules, higher in MA, display associations with numerous distinguishable MS peaks. The recursive nature of the proposed algorithm mirrors the assembly pathways, where the construction of a molecule from its fragments informs the MA computation. Additionally, the study contemplates the interrelationship between molecular weight and MA, noting the practicality of employing this correlation for complexity inference.

Applications and Potential of Combined Methods

Beyond individual techniques, combining NMR, IR, and MS to infer molecular complexity manifests as a robust strategy, compensating for potential biases inherent to singular methods. The aggregate of these spectroscopic techniques enhances accuracy in predicting MA and is especially adept at handling mixtures, identifying the complexity of individual components. Such a multifaceted approach is not only conducive to swift assessments of molecular complex systems but also imperative for the exploration of potential biosignatures in astrobiological contexts.

In summation, the ability to define molecular complexity experimentally through spectroscopy and spectrometry marks a significant milestone. As the search for extraterrestrial life advances, these methodologies will augment tools that will interpret and quantify the complexity of unknown samples, both on Earth and distant worlds, fundamentally enriching our comprehension of life's molecular underpinnings.

Paper to Video (Beta)

No one has generated a video about this paper yet.

Whiteboard

No one has generated a whiteboard explanation for this paper yet.

Open Problems

We haven't generated a list of open problems mentioned in this paper yet.

Continue Learning

We haven't generated follow-up questions for this paper yet.

Collections

Sign up for free to add this paper to one or more collections.

Tweets

Sign up for free to view the 6 tweets with 270 likes about this paper.