Searching for the essence of life through physics

The ultimate goal of physics is to explain everything in nature by applying universal laws, even when it comes to explaining life.

Biology has been advancing at a remarkable pace since the late 20th century. This has been propelled by new techniques developed in the fields of molecular biology and biophysics, the most notable ones being genome analysis and measurement of cell function, respectively.

A number of complex biological phenomena are being elucidated at the molecular level. Nevertheless, humanity has yet to find a definitive answer to the fundamental question of “What is life?” because individual research findings exist separately from each other. Given this, Professor Higuchi is searching for the universality underlying a rich diversity of life phenomena, the key to which is physics.

“Biophysics is a discipline aimed at finding fundamental laws and principles in complex living systems,” he explained. “Advances in physics and chemistry have led to an enormous volume of quantitative data being accumulated in the life sciences. In order to gain a better understanding, this wealth of knowledge needs to be integrated into one theory by utilizing physics and mathematics. This is becoming feasible now that a mountain of data has been amassed.”

Professor Higuchi is working to identify a universal mechanism of molecular motors that power movements within cells. Muscle cells, immune cells, and cancer cells all move frequently. Cell division and intracellular vesicle transportation are also powered by molecular motors.

As such, molecules within cells are controlled by a motor mechanism that differs from the one that enables our daily lives.

“In the macro world, an object in motion stays in motion for a while even after the force that had set it in motion is removed because of the law of inertia,” said Professor Higuchi. “In contrast, nanoscale molecular motors move when energy is input, but stop immediately when energy ceases to be applied due to the viscosity of water providing massive resistance. I examined in detail the ways in which various kinds of molecular motors move forward by repeating this stop-and-restart cycle, resulting in the discovery of a universal principle of how they move.”

The Higuchi Laboratory utilizes a single-molecule technique, a tool that allows a single molecule’s movement to be visually monitored and its function to be quantified. While a group of molecules move intricately, a single molecule moves straightforwardly.

“Single is a notion we physicists prefer. A good example of this is our exploration of the nature of a single particle or electron,” he pointed out. “The single-molecule technique is the result of applying this notion to life phenomena.”

Elucidating a universal mechanism of intracellular molecular movement is expected to help uncover the essence of life or pave the way for new treatment for diseases.

Fascinated by muscle movement and structure, Professor Higuchi has long researched molecular motors, affiliated with a range of faculties over the years. After studying the fundamentals of physics and biophysics at a faculty of physics, he obtained a research position at a school of medicine, followed by working for a school of engineering and a medical research organization with the aim of applying findings from his single-molecule research to biomaterials and medicine.

“Knowledge has no boundaries,” he declared with a gentle smile. “All that matters is what you do, not which faculty or department you study at. Having said that, I strongly encourage those who wish to choose academia as a career to study at a school of science first. I have been able to continue my research beyond the boundaries of faculties and schools thanks to the principles of natural science that I learned. A correct understanding of these principles enables you to comprehend a variety of phenomena, providing the basis for application as well.”

Interview and text: Masatsugu Kayahara
Photography: Junichi Kaizuka

Originally published in The School of Science Brochure 2019

HIGUCHI Hideo

Professor, Biophysics, Department of Physics
Director, Universal Biology Institute, Graduate School of Science, The University of Tokyo

Completed a master’s degree in science and engineering at Waseda University and joined the Jikei University School of Medicine as a research assistant in 1983. From 1992, he worked for the Japan Science and Technology Agency (JST) as a group leader of Exploratory Research for Advanced Technology (ERATO). In 1997, he moved to Tohoku University, serving first as an associate professor at the Department of Metallurgy of the Graduate School of Engineering, then as a professor at Tohoku University Biomedical Engineering Research Organization (TUBERO) from 2004. He assumed his current position in 2008.