Sound waves, originating from vibrations in mediums like gases and liquids, are omnipresent in our daily experiences. Notably, high-frequency ultrasound waves, imperceptible to the human ear, are utilized in medical ultrasound examinations for diagnosing tissues or organs within the body. Consequently, sound waves serve as a vital energy source not only in medicine but also in telecommunications, energy harvesting, imaging, and various other domains. Acoustic lenses are fundamental in all these applications as they are instrumental in accurately focusing sound waves.

Professor Junsuk Rho’s team, known for their work on metalens, is attracting acclaim for their advancements in optical metalens for light wave manipulation as well as acoustic metalens for sound control. Metalens, comprised of artificial structures usually smaller than the wavelength of the waves, enables unrestricted manipulation of waves while significantly reducing lens thickness. This research extends the concept of a “wide field-of-view,” currently trending in next-generation AR and VR devices and displays, into the realm of acoustics, opening avenues for novel applications of “wide field-of-hearing” technology.

Wide field-of-hearing measures the breadth of angles through which a lens can display a sound image. Traditional acoustic metalenses suffer from undesired sound distortion (aberration) when waves approach at non-perpendicular angles. The team devised a method to meticulously control the phase of the metalens, ensuring precise focusing of sound waves regardless of their angle of incidence. This marks the first successful achievement and demonstration of a wide field-of-hearing using ultra-thin metalenses, achieving up to 140 degrees of field-of-hearing without sound distortion.

Professor Junsuk Rho of POSTECH stated, “By first demonstrating the significance and necessity of field-of-hearing, we’ve established a new paradigm in the realm of acoustic metalenses.” He added, “We will continue our work to further explore its applications in acoustic imaging and high-sensitivity sensing along with explorations in energy harvesting and submarine monitoring within underwater environments.”

The research was conducted with support from POSCO N.EX.T IMPACT and an organization-specific task of the Korea Research Institute of Ships & Ocean Engineering.

Led by Wolynes, the D.R. Bullard-Welch Foundation Professor of Science, professor of chemistry, biosciences and physics and astronomy and co-director of the Center for Theoretical Biological Physics (CTBP), the team focused on deciphering the complex energy landscapes of de-evolved, putative protein sequences corresponding to pseudogenes.

Pseudogenes are segments of DNA that once encoded proteins but have since lost their ability to do so due to sequence degradation — a phenomenon referred to as devolution. Here, devolution represents an unconstrained evolutionary process that occurs without the usual evolutionary pressures that regulate functional protein-coding sequences.

Despite their inactive state, pseudogenes offer a window into the evolutionary journey of proteins.

“Our paper explains that proteins can de-evolve,” Wolynes said. “A DNA sequence can, by mutations or other means, lose the signal that tells it to code for a protein. The DNA continues to mutate but does not have to lead to a sequence that can fold.”

The researchers studied junk DNA in a genome that has de-evolved. Their research revealed that a mutation accumulation in pseudogene sequences typically disrupts the native network of stabilizing interactions, making it challenging for these sequences, if they were to be translated, to fold into functional proteins.

However, the researchers observed instances where certain mutations unexpectedly stabilized the folding of pseudogenes at the cost of altering their previous biological functions.

They identified specific pseudogenes, such as cyclophilin A, profilin-1 and small ubiquitin-like modifier 2 protein, where stabilizing mutations occurred in regions crucial for binding to other molecules and other functions, suggesting a complex balance between protein stability and biological activity.

Moreover, the study highlights the dynamic nature of protein evolution as some previously pseudogenized genes may regain their protein-coding function over time despite undergoing multiple mutations.

Using sophisticated computational models, the researchers interpreted the interplay between physical folding landscapes and the evolutionary landscapes of pseudogenes. Their findings provide evidence that the funnellike character of folding landscapes comes from evolution.

“Proteins can de-evolve and have their ability to fold compromised over time due to mutations or other means,” Wolynes said. “Our study offers the first direct evidence that evolution is shaping the folding of proteins.”

Along with Wolynes, the research team includes lead author and applied physics graduate student Hana Jaafari ; CTBP postdoctoral associate Carlos Bueno ; University of Texas at Dallas graduate student Jonathan Martin; Faruck Morcos, associate professor in the Department of Biological Sciences at UT-Dallas; and CTBP biophysics researcher Nicholas P. Schafer.

The implications of this research extend beyond theoretical biology with potential applications in protein engineering, Jaafari said.

“It would be interesting to see if someone at a lab could confirm our results to see what happens to the pseudogenes that were more physically stable,” Jaafari said. “We have an idea based on our analysis, but it’d be compelling to get some experimental validation.”