The 2023 Emerging Leader in Molecular Spectroscopy Award

This year’s Emerging Leader in Molecular Spectroscopy Award recipient is Dmitry Kurouski, an assistant professor of chemistry at the Texas A&M University in College Station, Texas. From his early research days as a graduate student at State University of New York in Albany, Kurouski’s research has emphasized the development and application of innovative Raman spectroscopy methods for noninvasive, nondestructive analyses of biological materials.

Dmitry Kurouski is an assistant professor of chemistry at Texas A&M University who has made significant contributions to the field of molecular spectroscopy. His groundbreaking work has earned him the 2023 Emerging Leader in Molecular Spectroscopy Award.

Dmitry Kurouski

Kurouski’s research pioneered the development of innovative Raman spectroscopy–based sensing approaches that can be used for noninvasive, nondestructive analysis, including confirmatory diagnostics of biotic and abiotic stresses in plants. His findings demonstrate that Raman spectroscopy can be used for the identification of viral, fungal, and bacterial diseases in many plant species. He has also developed Raman methods for diagnostics of plant deficiencies in micro and macro element composition; his work has also demonstrated the potential for Raman spectroscopy–based phenotyping of plants.

This prestigious award, presented by Spectroscopy Magazine, recognizes the achievements and aspirations of a talented young molecular spectroscopist, with recipients being selected by an independent scientific committee. The award will be presented to Kurouski at the SciX 2023 conference held October 8–13 in Sparks, Nevada, where he will be honored in a symposium.

Using Raman Spectroscopy for Complex Applications

Kurouski received his PhD in 2013 from SUNY Albany, State University of New York, working with Professor Igor K. Lednev. While working on his PhD, Kurouski developed a deeper understanding of Raman spectroscopy for complex applications.

His early work has led to cutting-edge optical nanoscopic approaches that are based on tip-enhanced Raman spectroscopy (TERS) and atomic force microscopy (AFM) infrared (IR) imaging. His research group now utilizes this nano-Raman-nano-IR imaging approach to reveal the structural organization of amyloid oligomers and protein aggregates that are linked to many neurodegenerative diseases. He has also discovered that the structure and toxicity of amyloid oligomers can be uniquely altered by lipids. These findings suggest that irreversible changes in lipid profiles of organs may be the underlying biophysical cause that triggers formation of toxic protein species, which in turn are responsible for the onset and progression of amyloidogenic-type diseases. He was recently awarded a highly prestigious $1 million Maximizing Investigators’ Research Award (MIRA) from the National Institute of Health (NIH) to investigate the effect of lipids on the structure and toxicity of amyloid oligomers.

Kurouski and his research group have made significant progress in understanding the physics of hot carriers and plasmon-driven catalysis on mono- and bimetallic nanostructures. These findings discovered by his group have allowed for elucidation of the underlying physical cause of unique reactivity and selectivity in plasmon-driven catalysis, specifically on gold-platinum and gold-palladium bimetallic nanostructures.

The end of the year celebration party of the Kurouski group in College Station on May 2023. Left to right: Michael Lynn, 2nd year PhD student; Dr. Abid Ali, Postdoctoral Fellow; Aidan Holman, undergraduate student; Axell Rodriguez, undergraduate student; Tianyi Dou, 4th year PhD student, Isaac Juarez, 2nd year PhD student, Luke Osborne, undergraduate student; Professor Dmitry Kurouski; and Kiryl Zhaliazka, 1st year PhD student.

Kurouski’s group developed and deployed Raman spectroscopy for diagnostics of structural and metabolic changes in plants that can be used for confirmatory detection and identification of abiotic stress. The researchers developed spectroscopic libraries that, together with a hand-held Raman spectrometer, could be used to detect and identify nitrogen, phosphorus, and potassium deficiencies in rice. It was also demonstrated that Raman spectroscopy can be used for pre-symptomatic diagnostics of medium and high salinity stress in plants. Together, with more than 40 research reports on this topic, this work showed the emerging potential of Raman spectroscopy in agriculture. These findings are summarized in a review published by the Kurouski group last year.

Kurouski and his research team also have used nano-Raman-nano-IR imaging approaches to unravel the structural organization of viruses. Kurouski found that TERS was capable of resolving protein secondary structure, charge profile, and amino acid composition of the viral capsid with sub-nanometer spatial resolution, providing unprecedented insights into the organization and properties of viruses. At the same time, AFM-IR allowed for the elucidation of structural organization of the nucleic acids in viruses. This work demonstrated the complementary measurements of AFM-IR and TERS in probing depth and chemical information for challenging applications. With the development of confirmatory approaches for highly accurate identification of viruses, Kurouski’s research has significant implications for improving diagnostics and treatment of viral diseases. His groundbreaking work in the field of molecular spectroscopy has already made a significant impact on the scientific community and has the potential to revolutionize many aspects of modern medicine and agriculture.

Professor Kurouski (first on the left) discusses with Dr. Abid Ali (center) and two undergraduate students (Luke Osborne and Joseph Wilson), the strategies for the expression of alpha-synuclein, a protein that is linked to Parkinson disease.

Applying SERS and TERS for Characterization of Biological Systems

In his early work, Kurouski and coworkers used surface- and tip-enhanced Raman spectroscopy (SERS and TERS) as powerful tools for structural characterization of biological systems at the single-molecule scale (1).
However, enhanced Raman spectra of biological specimens often lack the amide I band, which is commonly used as a marker for the interpretation of secondary protein structures.

In this study, published in Analyst, the authors investigate the cause of this phenomenon for native insulin and insulin fibrils using both TERS and SERS, comparing these spectra to the spectra of well-defined homo-peptides. The results show that the appearance of the amide I Raman band is not determined by the protein aggregation state, but rather by the size of the amino acid side chain. Peptides with small side chain groups exhibit an intense amide I band in almost all acquired spectra, whereas those with bulky side chains, such as tyrosine and tryptophan, exhibit the amide I band in only a fraction of the acquired spectra.

This work provides new insights into the interpretation of Raman spectra of biological specimens and has important implications for the application of SERS and TERS in the study of protein structure and aggregation. The findings have the potential to improve our understanding of protein folding and aggregation mechanisms, as well as aid in the development of new diagnostic tools for protein misfolding diseases.

Professor Kurouski (standing on the right) discusses results of kinetics of protein aggregation with undergraduate fellow Luke Osborne.

Nanospectroscopy Studies With AFM-IR

The chemical composition of materials at the nanoscale can be challenging to analyze and understand using traditional analytical techniques. To address this issue, the integration of infrared (IR) and Raman spectroscopy with scanning probe methods has resulted in the development of new nanospectroscopy paradigms, such as photothermal induced resonance (PTIR), also known as AFM-IR, and tip-enhanced Raman spectroscopy (TERS). In an article published in Chemical Society Reviews, Kurouski and co-authors provide a detailed overview of the fundamentals and recent advances of AFM-IR and TERS, as well as complementary features (2).

The article highlights how the recent innovations in AFM-IR and TERS have expanded its applications in various fields, such as materials science, nanotechnology, biology, medicine, geology, optics, catalysis, and art conservation. Although AFM-IR and TERS were initially developed independently for different applications, the recent advancements have pushed its performance beyond initial expectations, making them spectroscopically complementary techniques. There are opportunities for these techniques to converge and complement each other, providing researchers with more insights into the chemical composition of materials at the nanoscale. AFM-IR and TERS have become crucial techniques for nanoscale chemical imaging and spectroscopy.

In another study by Lei Zhou and Kurouski, atomic force microscopy-infrared spectroscopy (AFM-IR) was used to examine the structure of individual α-synuclein oligomers at different stages of protein aggregation (3). The aggregation of α-synuclein protein is strongly linked to the development of Parkinson’s disease (PD). However, the structure and morphology of toxic intermediate oligomers formed during the aggregation process are not fully understood. The use of AFM-IR in this study allowed for the examination of individual oligomers at the nanoscale, which is critical for understanding the aggregation process and its relationship to protein structure.

Aberrant aggregation of α-synuclein protein is a hallmark of PD and other neurodegenerative disorders. The accumulation of α-synuclein in the form of intracellular inclusions, called Lewy bodies, is a pathological feature of PD. These inclusions are highly toxic to neurons, leading to neuronal dysfunction and degeneration. Additionally, soluble oligomeric forms of α-synuclein have been found to be highly neurotoxic and capable of inducing the formation of Lewy bodies. Therefore, understanding the structure and properties of α-synuclein oligomers and its role in the pathogenesis of PD is crucial for the development of effective diagnostic and therapeutic strategies.

The results of Zhou and Kurouski’s study showed that the morphology and structure of the oligomers changed with the progression of the aggregation process. The IR spectra of individual oligomers revealed structural rearrangements necessary for oligomers to propagate into fibrils with parallel-β-sheet secondary structure. This study provides insights into the structural organization of α-synuclein oligomers, which is essential to understand its toxicity. Moreover, the findings may contribute to the development of approaches for oligomer detection and pre-symptomatic diagnosis of PD.

Exploring Amyloid Fibrils Using TERS

Amyloid fibrils are associated with various neurodegenerative diseases and are of significant interest in structural biology. While conventional methods have provided insights into the morphology and core structure of fibrils, characterizing the surface has been challenging.

The formation of amyloid fibrils is a complex process that is associated with various neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and Huntington’s diseases, as well as prion diseases. The accumulation of amyloid fibrils is believed to contribute to the degeneration of neurons and cognitive decline in these diseases. Understanding the structure and formation mechanism of amyloid fibrils is therefore crucial for developing effective treatments for these diseases. Raman spectroscopy has been extensively used to investigate protein aggregation and amyloid fibril formation due to its ability to reveal changes in secondary and tertiary structures at all stages of fibrillation. When combined with atomic force and scanning electron microscopies, Raman spectroscopy becomes a powerful approach for investigating the structural organization of amyloid fibril polymorphs, which can provide valuable insights into its formation and potential therapeutic targets.

In a study published in the Journal of the American Chemical Society, Kurouski and colleagues used tip-enhanced Raman spectroscopy (TERS) to probe the surface structure of insulin fibrils (4). The study demonstrated that TERS can provide high-resolution insights into the secondary structure and amino acid residue composition of the fibril surface. The insulin fibril surface was found to be strongly heterogeneous, with clusters exhibiting different protein conformations. More than 30% of the surface was dominated by β-sheet secondary structure, supporting Dobson’s model of amyloid fibrils. The study also revealed the distribution of various amino acids on the fibril surface and specific surface secondary structure elements. Cysteine and aromatic amino acids such as phenylalanine and tyrosine were found to be enriched in β-sheet areas, whereas proline was only found in α-helical and unordered protein clusters. The study also showed that carboxyl, amino, and imino groups were nearly equally distributed over β-sheet and α-helix/unordered regions.

In a review published in Analyst, Kurouski and coauthors explore the applications of Raman spectroscopy in the structural characterization of amyloidogenic proteins, prefibrillar oligomers, and mature fibrils (5). The review summarizes various techniques that have been used in conjunction with Raman spectroscopy to provide a comprehensive understanding of the structure and formation mechanism of amyloid fibrils. The article highlights that Raman spectroscopy is a unique, label-free and nondestructive technique that can reveal the structural changes of amyloid fibrils during the fibrillation process. Amyloid fibrils are protein aggregates that form when proteins misfold and aggregate together in a β-sheet structure.

Understanding Plant Pathogens

Plant pathogens are microorganisms that can infect and cause diseases in plants, leading to significant yield losses and reduced crop quality. Maize kernels, which are important sources of food and feed, are particularly susceptible to various pathogens, such as fungi and bacteria. These pathogens can cause symptoms such as discoloration, mold growth, and reduced kernel size, which negatively impact both yield and quality. Early detection and identification of these pathogens are critical for effective disease management and prevention. In this context, nondestructive and noninvasive techniques such as Raman spectroscopy are promising tools for rapid and accurate diagnosis, as demonstrated in the study published in Analytical Chemistry by Charles Farber and Kurouski (6).

In this study, researchers aimed to develop a rapid and nondestructive method for detecting and identifying plant pathogens on maize kernels, which is crucial for improving crop yield. They used a hand-held Raman spectrometer along with chemometric analysis to distinguish between healthy and diseased maize kernels and different diseases with 100% accuracy. Raman spectroscopy is a noninvasive and nondestructive technique that provides information about the chemical structure of a specimen. The sample-agnostic and portable nature of the analysis suggests that it could be retooled for other crops and conducted autonomously. This approach offers advantages over traditional pathogen assaying methods such as polymerase chain reaction (PCR) or enzyme-linked immunosorbent assay (ELISA), which are time-consuming and destructive to the sample. The study demonstrated the feasibility of using Raman spectroscopy for pathogen detection and identification, which could potentially have a significant impact on crop management and food security. The use of handheld Raman spectrometers allows for the implementation of this technique in the field, enabling rapid and accurate diagnosis of plant diseases, and facilitating prompt management decisions that can help protect crops from further damage.

Looking to the Future

Kurouski’s contributions to the field of molecular spectroscopy have been both significant and varied. His work in the area of Raman spectroscopy has led to the development of new, noninvasive methods for analyzing plant health and has demonstrated the potential of this technique for use in agriculture. Additionally, his work in the area of nano-Raman-nano-IR imaging has shed new insights into the structure of amyloid oligomers and protein aggregates that are linked to neurodegenerative diseases. His work in the area of plasmon-driven catalysis has elucidated the underlying physical causes of unique reactivity and selectivity in bimetallic nanostructures.

Kurouski’s accomplishments have not gone unnoticed, as evidenced by his numerous awards and honors, including the 2023 Emerging Leader in Molecular Spectroscopy Award from Spectroscopy magazine. His publication record, which includes over 140 papers with more than 4,000 citations, and his extensive record of conference presentations demonstrate the impact of his research on the field of molecular spectroscopy.

Looking to the future, it seems likely that Kurouski will continue to make significant contributions to the field of molecular spectroscopy. His work has already demonstrated the potential of Raman spectroscopy for use in agriculture and for diagnostics of viral particles. As his research continues to progress, it seems likely that his work will continue to open new doors in this exciting and important field.

References

(1) Kurouski, D.; Postiglione, T.; Deckert-Gaudig, T.; Deckert, V.; Lednev, I. K. Amide I vibrational mode suppression in surface (SERS) and tip (TERS) enhanced Raman spectra of protein specimens. Analyst 2013, 138 (6), 1665–1673. DOI: 10.1039/C2AN36478F

(2) Kurouski, D.; Dazzi, A.; Zenobi, R.; Centrone, A. Infrared and Raman chemical imaging and spectroscopy at the nanoscale. Chem. Soc. Rev. 2020, 49 (11), 3315–3347. DOI: 10.1039/C8CS00916C

(3) Zhou, L.; Kurouski, D. Structural Characterization of Individual α-Synuclein Oligomers Formed at Different Stages of Protein Aggregation by Atomic Force Microscopy-Infrared Spectroscopy. Anal. Chem. 2020, 92 (10), 6806–6810. DOI: 10.1021/acs.analchem.0c00593

(4) Kurouski D.; Deckert-Gaudig T.; Deckert V.; Lednev I.K. Structure and Composition of Insulin Fibril Surfaces Probed by TERS. J. Am. Chem. Soc. 2012, 134 (32), 13323–13329. DOI: 10.1021/ja303263y

(5) Kurouski, D.; Van Duyne, R. P.; Lednev, I. K. Exploring the structure and formation mechanism of amyloid fibrils by Raman spectroscopy: a review. Analyst 2015, 140 (15), 4967–4980. DOI: 10.1039/C5AN00342C

(6) Farber, C.; Kurouski, D. Detection and Identification of Plant Pathogens on Maize Kernels with a Hand-Held Raman Spectrometer. Anal. Chem. 2018, 90 (5), 3009–3012. DOI: 10.1021/acs.analchem.8b00222

Jerome Workman, Jr. serves on the Editorial Advisory Board of Spectroscopy and is the Senior Technical Editor for LCGC and Spectroscopy. He is the co-host of the Analytically Speaking podcast and has published multiple reference text volumes, including the three-volume Academic Press Handbook of Organic Compounds, the five-volume The Concise Handbook of Analytical Spectroscopy, the 2nd edition of Practical Guide and Spectral Atlas for Interpretive Near-Infrared Spectroscopy, the 2nd edition of Chemometrics in Spectroscopy, and the 4th edition of The Handbook of Near-Infrared Analysis. ●