Tag Archives: biophysics

Biophysics helps unravel protein–nanoparticle interactions

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A June 27, 2025 news item on Technology Networks announces health research from Japan,

Nanoparticles (NPs) are materials whose dimensions range from 1 to 1,000 nanometers (nm). Due to their nano-scale dimensions and tunable material properties, NPs have gained interest in the global scientific community in recent years. Applications of NPs in the field of human health include NP-based drug delivery systems and radioactive probe-linked NPs for medical diagnosis. While significant advancements have been achieved in the design and synthesis of NPs, studies investigating the interactions of NPs with important biological macromolecules like proteins remain limited.

To reveal the science behind the protein–nanoparticle interaction and its implications for human health, a team of researchers led by Associate Professor Masakazu Umezawa from the Department of Medical and Robotic Engineering Design, Faculty of Advanced Engineering, Tokyo University of Science, Japan, conducted a series of spectroscopy-based experiments. The research team comprised Mr. Naoya Sakaguchi, a second-year PhD student from the Department of Materials Science and Technology, Faculty of Advanced Engineering, Tokyo University of Science, and Junior Associate Professor Atsuto Onoda from Sanyo-Onoda City University. Their research findings were published online in Langmuir on June 3, 2025.

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A June 26, 2025 Tokyo University of Science press release (also on EurekAlert), which originated the news item on Technology Networks, describes the research in more detail,

In their study, the researchers employed bovine serum albumin (BSA) as the main protein of interest and silica NPs (SiNPs) with diameters ranging from 10 nm to 10 μm (10,000 nm). They analyzed the protein–nanoparticle interactions using thioflavin T (ThT) fluorescence, Fourier transform infrared spectroscopy (FT-IR), and circular dichroism (CD).  

Explaining the motivation behind the present study, Dr. Umezawa says, “When NPs are administered in vivo, interactions with proteins and other biomolecules may occur, leading to the modulation of their biological effects. Therefore, establishing the safety of NPs along with clarifying the effects of NPs on the secondary structure of proteins is highly important.” 

The scientists found that the ThT fluorescence intensity decreased with increasing SiNP size. Notably, a drastic increase in the ThT fluorescence intensity was observed when BSA was mixed with 10 nm-sized SiNPs at a stirring time of one hour. However, when BSA was mixed with the largest SiNPs (10 μm) for longer stirring times up to 48 hours, the ThT fluorescence intensity was markedly higher.  

“The increase in β-sheet formation in BSA, the most abundant protein in serum and cerebrospinal fluid, is remarkably high during interaction with 10 nm-sized SiNPs. This shows that ultra-small SiNPs can induce abnormal protein conformation and have the potential to cause pathological conditions like Alzheimer’s disease, which involves the formation of amyloid β-peptides,” states Dr. Umezawa.  

Further FT-IR experiments to study the secondary protein structure of BSA revealed varied results. The amount of β-sheet structures in BSA increased with longer stirring times in the presence of 10 μm SiNPs. To gain a better picture of the protein–nanoparticle interaction dynamics, Dr. Umezawa and team turned their attention to CD. Using the Beta Structure Selection (BeStSel) technique, which could specifically detect β-sheet-derived peaks, they found that the α-helical structure of BSA was disrupted by interaction with SiNPs. While the α-helix structure percentage in BSA decreased during interaction with SiNPs, parallel β-sheet protein confirmation was increasingly favored.  

In summary, this study reveals the impact of ultra-small NPs on biological macromolecules, like proteins. The insights gained from the protein–nanoparticle interaction can guide the development of safe and effective nanoparticle-based systems for applications in various fields of medical biology. 

Here’s a link to and a citation for the paper,

Changes in the Protein Secondary Structure on the Surface of Silica Nanoparticles with Different Sizes by Naoya Sakaguchi, Atsuto Onoda, Kyoko Omata, Masakazu Umezawa. Langmuir 2025, 41, 23, 15143–15148 DOI: https://doi.org/10.1021/acs.langmuir.5c01606 Published June 3, 2025 Copyright © 2025 The Authors. Published by American Chemical Society. This publication is licensed under CC-BY 4.0 .

This paper is open access.

The quantum mechanics of photosynthesis

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Thankfully, Jared Sagoff included a description of photosynthesis (I’ve long since forgotten the mechanics of the process) in his May 21, 2012 article, Scientists uncover a photosynthetic puzzle, on the US Dept. of Energy’s Argonne National Laboratory website. From Sagoff’s article, here’s the photosynthesis  description along with a description of the quantum effect the scientists observed,

While different species of plants, algae and bacteria have evolved a variety of different mechanisms to harvest light energy, they all share a feature known as a photosynthetic reaction center. Pigments and proteins found in the reaction center help organisms perform the initial stage of energy conversion.

These pigment molecules, or chromophores, are responsible for absorbing the energy carried by incoming light. After a photon hits the cell, it excites one of the electrons inside the chromophore. As they observed the initial step of the process, Argonne scientists saw something no one had observed before: a single photon appeared to excite different chromophores simultaneously.

Here’s a gorgeous image of a leaf provided with the article,

I was aware that scientists are working at hard at duplicating photosynthesis but until reading this upcoming excerpt from Sagoff’s article, I had not appreciated the dimensions of the problem,

The result of the study could significantly influence efforts by chemists and nanoscientists to create artificial materials and devices that can imitate natural photosynthetic systems. Researchers still have a long way to go before they will be able to create devices that match the light harvesting efficiency of a plant.

One reason for this shortcoming, Tiede [Argonne biochemist David Tiede] explained, is that artificial photosynthesis experiments have not been able to replicate the molecular matrix that contains the chromophores. “The level that we are at with artificial photosynthesis is that we can make the pigments and stick them together, but we cannot duplicate any of the external environment,” he said.  “The next step is to build in this framework, and then these kinds of quantum effects may become more apparent.”

Because the moment when the quantum effect occurs is so short-lived – less than a trillionth of a second – scientists will have a hard time ascertaining biological and physical rationales for their existence in the first place. [emphasis mine] “It makes us wonder if they are really just there by accident, or if they are telling us something subtle and unique about these materials,” Tiede said. “Whatever the case, we’re getting at the fundamentals of the first step of energy conversion in photosynthesis.”

Thanks to Nanowerk for the May 24, 2012 news item which drew this article to my attention.