Revolutionary Discovery: Molecular Machines Twist DNA While Looping Chromosomes

Groundbreaking Discovery by Researchers from TU Delft and IMP Vienna Biocenter

Illustration of SMC proteins twisting and looping DNA, revealing new molecular mechanisms critical for chromosome function.

Researchers from the Kavli Institute at Delft University of Technology and the IMP Vienna Biocenter have uncovered a novel characteristic of the molecular motors responsible for shaping chromosomes. Building on their discovery six years ago that SMC motor proteins create extended loops in DNA, they have now revealed that these motors also introduce substantial twists within the loops they form.

Understanding the Impact of DNA Twisting on Chromosome Structure and Function

This research enhances our understanding of chromosome structure and function, shedding light on how disruptions in twisted DNA looping may contribute to health conditions such as developmental disorders like cohesinopathies. The findings were published in Science Advances.

The Challenge of Packing DNA into the Nucleus

Consider the challenge of fitting two meters of rope into a space smaller than the tip of a needle-this is akin to the task every cell faces when organizing its DNA within the tiny nucleus. To manage this, nature uses remarkable methods, such as coiling the DNA into supercoils and wrapping it around specialized proteins for efficient storage.

Tiny DNA Loop Play a Critical Role in Regulating Chromosome Functions

The Role of SMC Proteins in DNA Looping and Chromosome Structure

Compaction alone is insufficient; cells must also regulate chromosome structure to facilitate its function. For instance, when genetic information is required, the DNA is read locally. Specifically, during cell division, the DNA must first unwind, replicate, and then ensure proper separation into two daughter cells.

The Discovery of SMC Complexes and Their Role in DNA Looping

SMC complexes (structural maintenance of chromosomes), specialized protein machines, are essential for these processes. Only a few years ago, researchers at Delft and elsewhere discovered that SMC proteins act as molecular motors, forming long loops in DNA, which are crucial for regulating chromosome function.

Pioneering Research Using Magnetic Tweezers to Observe SMC Protein Behavior

Observing DNA Looping and Twisting in Real Time

At Cees Dekkar's lab at TU Delft, postdocs Richard Janissen and Roman Bath have uncovered important insights to solve this puzzle. They pioneered a new method using "Magnetic Tweezers," enabling them to observe individual SMC proteins making looping movements in DNA.

A Key Breakthrough: SMC Proteins Twist DNA During Looping

An important breakthrough was their ability to observe whether the SMC protein modifies the twist in the DNA. Interestingly, the team found that it does: the human SMC protein cohesin not only loops the DNA but also twists it in a left-handed direction, adding 0.6 turns with each loop formed.

Understanding the Evolutionary Path of SMC Proteins

Evolutionary Consistency in DNA Looping and Twisting Mechanisms

In addition, the team found that this twisting action is not confined to humans. SMC proteins in yeast show identical behavior. Interestingly, all SMC proteins from both humans and yeast twist DNA by 0.6 turns with each extrusion step. This finding indicates that the DNA extrusion and twisting processes have remained consistent throughout evolution.

A Universal Mechanism for DNA Looping Across Species

Whether the DNA is looped in humans, yeast, or any other cell, nature follows the same approach.

Implications of DNA Looping for Gene Expression and Health

The Role of DNA Looping in Supercoiling and Gene Expression

These new discoveries offer crucial insights into deciphering the molecular mechanism behind this novel motor type. Furthermore, they reveal that DNA looping influences the supercoiling state of chromosomes, which in turn impacts key processes such as gene expression.

SMC Proteins and Their Link to Genetic Disorders

Understanding the Link Between SMC Proteins and Cornelia de Lange Syndrome

Finally, the SMC proteins are linked to a number of disorders, such as Cornelia de Lange Syndrome. Gaining insights into these processes is vital for pinpointing the molecular causes of these serious diseases.

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Labels: Biotechnology, Chromosome Structure, Cohesinopathies, DNA, DNA Research, Gene Expression, Genetic Disorders, Molecular Motors, Science Advances, SMC Proteins

Quantum Theory Meets Information Theory: Groundbreaking Experiment Confirms Link

Experimental setup showcasing quantum photons and beam-splitters validating complementarity and entropy relationship.

Introduction

A collaborative effort between researchers from Linköping University, Poland, and Chile has substantiated a theory connecting the complementarity principle with entropic uncertainty, as detailed in Science Advances.

Impact of the Findings

"At present, our findings lack immediate or direct applications, However, as fundamental research, they establish a groundwork for future advancements in quantum information and quantum computing. This field holds immense potential for groundbreaking discoveries across diverse research areas," states Guilherme B. Xavier, a quantum communication researcher at Linköping University, Sweden.

A Clear understanding of what the researchers have demonstrated necessitates starting from the beginning.

Understanding the Foundations of Quantum Mechanics

The Dual Nature of Light

The dual nature of light, behaving as both particles and waves, is one of quantum mechanics' most paradoxical yet foundational principles, known as wave-particle duality.

Historical Development of Wave-Particle Duality

The origins of this theory trace back to the 17th century when Isaac Newton proposed that light is made up of particles. Meanwhile, other scholars of the time argued that light consists of waves.

Newton ultimately speculated that light might embody both properties, though he was unable to substantiate it. It wasn't until the 19th century that experiments conducted by various physicists provided evidence confirming light's wave-like nature.

The Emergence of Photons

In the early 1900x, Max Planck and Albert Einstein began to challenge the notion that light behaves solely as waves. It was not until the 1920s, however, that physicist Arthur Compton demonstrated light's kinetic energy, a property characteristic of classical particles.

These particles were named photons, leading to the conclusion that light behaves both as particles and waves, aligning with Newton's earlier hypothesis. Electrons and other elementary particles share this wave-particle duality.

The Complementarity Principle

However, it is impossible to observe the same photon simultaneously as a wave and a particle. The nature of the photon revealed depends on the method of measurement, whether wave-like or particle-like. This phenomenon, known as the complementarity principle, was fromulated by Niels Bohr in the mid-1920s. It asserts that while the observed characteristic may vary, the interplay of wave and particle properties remains constant.

Connecting Complementarity and Entropic Uncertainty

A Mathematical Link Established in 2014

In 2014, a research team from Singapore mathematically established a direct link between the complementarity principle and the entropic uncertainty, representing the degree of unknown information in a quantum system.

The relationship implies that regardless of which combination of wave or particle properties is examined in a quantum system, at least one bit of information remains unknown, corresponding to the unobservable wave or particle.

Confirmation of the Theory Through Experimentation

In this new research, the theory established by Singaporean researchers has been confirmed in practice using a pioneering experimental design.

According to Guilherme B Xavier, "This is a remarkably straightforward demonstration of fundamental quantum mechanical behavior. It exemplifies quantum physics, where results are observable, yet the internal mechanics remain elusive. Despite this, it holds potential for practical applications, blending science with a touch of philosophy."

Experimental Setup and Observations

New Approach with Photons and Orbital Angular Momentum

The researchers at Linköping University designed a novel experimental setup utilizing photons with Orbital Angular Momentum, which travel in a circular motion rather than the traditional oscillating, up-and-down pattern. This approach not only introduces a new dynamic but also enables the experiment to hold greater potential for future practical applications by encoding more information.

Joakim Argillander and Daniel Spegel-Lexne, Ph.D. students of LiU.

The Use of Interferometers in Measurements

The measurements utilize a commonly used research instrument, the interferometer, where photons are directed at a beam-splitting crystal. This device divides their trajectory into two distinct paths, which subsequently intersect at a second beam splitter. The photons are then analyzed as either particles or waves, contingent upon the configuration of the second splitter.

Unique Feature of the Experimental Setup

A distinctive feature of this experimental setup is the ability to partially insert the second beam splitter into the light's path, enabling measurements of light as waves, particles, or a combination thereof.

Future Applications and Research

Quantum Communication, Metrology, and Cryptography

Researchers suggest that these findings hold promise for future applications in quantum communication, metrology, and cryptography, while also opening avenues for further fundamental exploration.

Upcoming Experiments and Future Directions

"Our next experiment aims to investigate photon behavior when the configuration of the second crystal is altered just before photon arrival. This could demonstrate the potential of our set-up for secure encryption key distribution, which is truly exciting," explains Daniel Spegel-Lexne, Ph.D. student in the Department of Electrical Engineering.