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Yi G, Jeon S, Kwon YW, Park J, Nguyen DA, Suchand Sandeep CS, Hwang WS, Hong SW, Kim S, Kim YJ. Enhanced third harmonic generation in ultrathin free-standing β-Ga 2O 3 nanomembranes: study on surface and bulk contribution. NANOSCALE 2021; 14:175-186. [PMID: 34904989 DOI: 10.1039/d1nr06259j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Third harmonic generation (THG) has proven its value in surface and interface characterization, high-contrast bio-imaging, and sub-wavelength light manipulation. Although THG is observed widely in general solid and liquid substances, when laser pulses are focused at nanometer-level ultra-thin films, the bulk THG has been reported to play the dominant role. However, there are still third harmonics (TH) generated at the surface of the thin-films, not inside the bulk solid - so-called surface TH, whose relative contribution has not been quantitatively revealed to date. In this study, we quantitatively characterized the surface and bulk contributions of THG at ultra-thin β-Ga2O3 nanomembranes with control of both the laser and thin-nanomembranes parameters, including the laser peak power, polarization state, number of layers, and nanomembranes thicknesses. Their contributions were studied in detail by analyzing the TH from freestanding β-Ga2O3 nanomembranes compared with TH from β-Ga2O3 nanomembranes on glass substrates. The contribution of the TH field from the β-Ga2O3-air interface was found to be 5.12 times more efficient than that from the β-Ga2O3-glass interface, and also 1.09 times stronger than the TH excited at bulk 1-μm-thick β-Ga2O3. Besides, TH from the β-Ga2O3-air interface was found to be 20% more sensitive to the crystalline structure than that from the β-Ga2O3-glass interface. This research work deepens our understanding of surface and bulk THG from crystalline materials and provides new possibilities towards designing highly efficient nonlinear optical materials for bio-imaging, energy-harvesting, and ultrafast laser development.
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Affiliation(s)
- Gao Yi
- School of Mechanical and Aerospace Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue 639798, Singapore.
| | - Sangheon Jeon
- Department of Cogno-Mechatronics Engineering, Department of Optics and Mechatronics Engineering, Pusan National University (PNU), 30 Jangjeon-dong Geumjeong-gu, Busan 46241, Republic of Korea.
| | - Young Woo Kwon
- Department of Nano-Fusion Technology, College of Nanoscience and Nanotechnology, Pusan National University (PNU), 30 Jangjeon-dong Geumjeong-gu, Busan 46241, Republic of Korea
| | - Jongkyoon Park
- Department of Cogno-Mechatronics Engineering, Department of Optics and Mechatronics Engineering, Pusan National University (PNU), 30 Jangjeon-dong Geumjeong-gu, Busan 46241, Republic of Korea.
| | - Duy Anh Nguyen
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehark-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - C S Suchand Sandeep
- School of Mechanical and Aerospace Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue 639798, Singapore.
| | - Wan Sik Hwang
- Department of Materials Science and Engineering, Korea Aerospace University, 76 Hanggongdaehak-ro, Deogyang-gu, Goyang 10540, Republic of Korea
| | - Suck Won Hong
- Department of Cogno-Mechatronics Engineering, Department of Optics and Mechatronics Engineering, Pusan National University (PNU), 30 Jangjeon-dong Geumjeong-gu, Busan 46241, Republic of Korea.
| | - Seungchul Kim
- Department of Cogno-Mechatronics Engineering, Department of Optics and Mechatronics Engineering, Pusan National University (PNU), 30 Jangjeon-dong Geumjeong-gu, Busan 46241, Republic of Korea.
| | - Young-Jin Kim
- School of Mechanical and Aerospace Engineering, Nanyang Technological University (NTU), 50 Nanyang Avenue 639798, Singapore.
- Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehark-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
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Lundquist KP, Panchal V, Gotfredsen CH, Brenk R, Clausen MH. Fragment-Based Drug Discovery for RNA Targets. ChemMedChem 2021; 16:2588-2603. [PMID: 34101375 DOI: 10.1002/cmdc.202100324] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Indexed: 12/26/2022]
Abstract
Rapid development within the fields of both fragment-based drug discovery (FBDD) and medicinal targeting of RNA provides possibilities for combining technologies and methods in novel ways. This review provides an overview of fragment-based screening (FBS) against RNA targets, including a discussion of the most recently used screening and hit validation methods such as NMR spectroscopy, X-ray crystallography, and virtual screening methods. A discussion of fragment library design based on research from small-molecule RNA binders provides an overview on both the currently limited guidelines within RNA-targeting fragment library design, and future possibilities. Finally, future perspectives are provided on screening and hit validation methods not yet used in combination with both fragment screening and RNA targets.
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Affiliation(s)
- Kasper P Lundquist
- Center for Nanomedicine and Theranostics, Department of Chemistry, Technical University of Denmark, Kemitorvet 207, 2800, Kgs. Lyngby, Denmark
| | - Vipul Panchal
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5020, Bergen, Norway
| | - Charlotte H Gotfredsen
- NMR Center ⋅ DTU, Department of Chemistry, Technical University of Denmark, Kemitorvet 207, 2800, Kgs. Lyngby, Denmark
| | - Ruth Brenk
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5020, Bergen, Norway
| | - Mads H Clausen
- Center for Nanomedicine and Theranostics, Department of Chemistry, Technical University of Denmark, Kemitorvet 207, 2800, Kgs. Lyngby, Denmark
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FitzGerald EA, Butko MT, Boronat P, Cederfelt D, Abramsson M, Ludviksdottir H, van Muijlwijk-Koezen JE, de Esch IJP, Dobritzsch D, Young T, Danielson UH. Discovery of fragments inducing conformational effects in dynamic proteins using a second-harmonic generation biosensor. RSC Adv 2021; 11:7527-7537. [PMID: 35423271 PMCID: PMC8694943 DOI: 10.1039/d0ra09844b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Accepted: 01/28/2021] [Indexed: 01/13/2023] Open
Abstract
Biophysical screening of compound libraries for the identification of ligands that interact with a protein is efficient, but does typically not reveal if (or how) ligands may interfere with its functional properties. For this a biochemical/functional assay is required. But for proteins whose function is dependent on a conformational change, such assays are typically complex or have low throughput. Here we have explored a high-throughput second-harmonic generation (SHG) biosensor to detect fragments that induce conformational changes upon binding to a protein in real time and identify dynamic regions. Multiwell plate format SHG assays were developed for wild-type and six engineered single-cysteine mutants of acetyl choline binding protein (AChBP), a homologue to ligand gated ion channels (LGICs). They were conjugated with second harmonic-active labels via amine or maleimide coupling. To validate the assay, it was confirmed that the conformational changes induced in AChBP by nicotinic acetyl choline receptor (nAChR) agonists and antagonists were qualitatively different. A 1056 fragment library was subsequently screened against all variants and conformational modulators of AChBP were successfully identified, with hit rates from 9-22%, depending on the AChBP variant. A subset of four hits was selected for orthogonal validation and structural analysis. A time-resolved grating-coupled interferometry-based biosensor assay confirmed the interaction to be a reversible 1-step 1 : 1 interaction, and provided estimates of affinities and interaction kinetic rate constants (K D = 0.28-63 μM, k a = 0.1-6 μM-1 s-1, k d = 1 s-1). X-ray crystallography of two of the fragments confirmed their binding at a previously described conformationally dynamic site, corresponding to the regulatory site of LGICs. These results reveal that SHG has the sensitivity to identify fragments that induce conformational changes in a protein. A selection of fragment hits with a response profile different to known LGIC regulators was characterized and confirmed to bind to dynamic regions of the protein.
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Affiliation(s)
- Edward A FitzGerald
- Department of Chemistry - BMC, Uppsala University Uppsala 751 23 Sweden
- Beactica Therapeutics Virdings allé 2 Uppsala 754 40 Sweden
| | | | - Pierre Boronat
- Amsterdam Institute of Molecular and Life Sciences (AIMMS), Division of Medicinal Chemistry, Faculty of Science, Vrije Universiteit Amsterdam De Boelelaan 1108 1081 HZ Amsterdam The Netherlands
| | - Daniela Cederfelt
- Department of Chemistry - BMC, Uppsala University Uppsala 751 23 Sweden
| | - Mia Abramsson
- Department of Chemistry - BMC, Uppsala University Uppsala 751 23 Sweden
| | | | - Jacqueline E van Muijlwijk-Koezen
- Amsterdam Institute of Molecular and Life Sciences (AIMMS), Division of Medicinal Chemistry, Faculty of Science, Vrije Universiteit Amsterdam De Boelelaan 1108 1081 HZ Amsterdam The Netherlands
| | - Iwan J P de Esch
- Amsterdam Institute of Molecular and Life Sciences (AIMMS), Division of Medicinal Chemistry, Faculty of Science, Vrije Universiteit Amsterdam De Boelelaan 1108 1081 HZ Amsterdam The Netherlands
| | - Doreen Dobritzsch
- Department of Chemistry - BMC, Uppsala University Uppsala 751 23 Sweden
| | - Tracy Young
- Biodesy, Inc. 170 Harbor Way South San Francisco 94080 CA USA
| | - U Helena Danielson
- Department of Chemistry - BMC, Uppsala University Uppsala 751 23 Sweden
- Science for Life Laboratory, Uppsala University Sweden
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