Prof. Johan Hofkens Profile

Prof. Johan Hofkens

at KU Leuven

SPIE Involvement:

Conference Program Committee | Author

Proceedings Article | 22 May 2018 Paper

The power of single molecule microscopy: from nanoparticle investigations to microbiome analysis

Elke Debroye, Haifeng Yuan, Julian Steele, Maarten Roeffaers, Doortje Borrenberghs, Kris Janssen, Arno Bouwens, Johan Hofkens

Proceedings Volume 10712, 1071208 (2018) https://doi.org/10.1117/12.2316568

KEYWORDS: Microscopy, Luminescence, Molecules, Perovskite, Nanoparticles, Biological research, Microscopes, Optical microscopy, Diffraction, Super resolution

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Proceedings Article | 24 April 2018 Paper

Femtosecond laser trapping, assembling, and ejection dynamics of dielectric nanoparticles in solution

Hiroshi Masuhara, Jim Jui-Kai Chen, Wei-Yi Chiang, Anwar Usman, Teruki Sugiyama, Johan Hofkens

Proceedings Volume 10712, 1071202 (2018) https://doi.org/10.1117/12.2318416

KEYWORDS: Nanoparticles

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Proceedings Article | 6 January 2015 Paper

Luminescence of fixed site Ag nanoclusters in a simple oxyfluoride glass host and plasmon absorption of amorphous Ag nanoparticles in a complex oxyfluoride glass host

Mikhail Shestakov, Maria Meledina, Stuart Turner, Wouter Baekelant, Niels Verellen, Xianmei Chen, Johan Hofkens, Gustaaf Van Tendeloo, Victor Moshchalkov

Proceedings Volume 9450, 94501N (2015) https://doi.org/10.1117/12.2068198

KEYWORDS: Silver, Glasses, Nanoparticles, Luminescence, Absorption, Energy transfer, Ultraviolet radiation, Quantum efficiency, Absorbance, Plasmons

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Proceedings Article | 13 November 2014 Paper

Remote excitation fluorescence correlation spectroscopy using silver nanowires

Liang Su, Haifeng Yuan, Gang Lu, Johan Hofkens, Maarten Roeffaers, Hiroshi Uji-i

Proceedings Volume 9277, 92771A (2014) https://doi.org/10.1117/12.2071376

KEYWORDS: Fluorescence correlation spectroscopy, Molecules, Silver, Polarization, Nanoparticles, Diffusion, Luminescence, Metals, Signal to noise ratio, Nanowires

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Proceedings Article | 1 May 2014 Paper

Taking the spectral overlap between excitation and emission spectra of fluorescent materials into account with Monte Carlo simulations

Sven Leyre, Jana Ryckaert, Paula Acuna, Jan Audenaert, Youri Meuret, Johan Hofkens, Guy Durinck, Geert Deconinck, Peter Hanselaer

Proceedings Volume 9131, 913103 (2014) https://doi.org/10.1117/12.2051995

KEYWORDS: Ray tracing, Monte Carlo methods, Quantum dots, Fluorescent materials, Light emitting diodes, Absorption, Luminescence, Photons, Computer simulations, Modeling

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Proceedings Article | 27 September 2012 Paper

Charge transfer effects in graphene-CdSe/ZnS quantum dots composites

Alexander Klekachev, Inge Asselberghs, Sergey Kuznetsov, Mirco Cantoro, Jeong Hun Mun, Byung-Jin Cho, Jun-ichi Hotta, Johan Hofkens, Marleen van der Veen, André Stesmans, Marc Heyns, Stefan De Gendt

Proceedings Volume 8462, 84620L (2012) https://doi.org/10.1117/12.930082

KEYWORDS: Graphene, Quantum dots, Electroluminescence, Luminescence, Field effect transistors, Photodetectors, Transistors, Glasses, Phototransistors, Semiconductors

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SPIE Journal Paper | 1 May 2008 Open Access

Probing dimerization and intraprotein fluorescence resonance energy transfer in a far-red fluorescent protein from the sea anemone Heteractis crispa

Guillaume Lessard, Satoshi Habuchi, James Werner, Peter Goodwin, Frans De Schryver, Johan Hofkens, Mircea Cotlet

JBO, Vol. 13, Issue 03, 031212, (May 2008) https://doi.org/10.1117/12.10.1117/1.2937477

KEYWORDS: Chromophores, Luminescence, Green fluorescent protein, Fluorescence resonance energy transfer, Proteins, Fluorescence correlation spectroscopy, Fluorescent proteins, Fluorescence spectroscopy, Molecules, Diffusion

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Proceedings Article | 14 February 2007 Paper

Naphthalene diimides as tunable fluorophores suitable for single-molecule applications

Toby Bell, Sheryll Yap, Chintan Jani, Steven Langford, Johan Hofkens, Frans De Schryver, Kenneth Ghiggino

Proceedings Volume 6444, 644404 (2007) https://doi.org/10.1117/12.701443

KEYWORDS: Molecules, Luminescence, Absorption, Photons, Fluorescence resonance energy transfer, Bioalcohols, Nitrogen, Quantum efficiency, Visible radiation, Polymethylmethacrylate

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Proceedings Article | 30 August 2006 Paper

Inhomogeneity of electron injection rates in dye-sensitized TiO2: continuous mesoporous films and single particle behavior

Toby D. M. Bell, Cynthia Pagba, Mykhaylo Myahkostupov, Johan Hofkens, Piotr Piotrowiak

Proceedings Volume 6325, 63250X (2006) https://doi.org/10.1117/12.681448

KEYWORDS: Nanoparticles, Molecules, Atmospheric particles, Particles, Confocal microscopy, Luminescence, Picosecond phenomena, Absorption, Microscopy, Ultrafast phenomena

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Proceedings Article | 28 February 2006 Paper

Probing dynamics of individual bio molecules by single molecule spectroscopy

W. Verheijen, H. Uji-i, C. Flors, J. Hotta, J. Hofkens

Proceedings Volume 6092, 60920I (2006) https://doi.org/10.1117/12.668270

KEYWORDS: Molecules, Luminescence, Confocal microscopy, Absorption, Molecular spectroscopy, Single molecule spectroscopy, Photon counting, Glasses, Proteins, Data modeling

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Proceedings Article | 22 February 2006 Paper

Single molecule spectroscopic characterization of a far-red fluorescent protein (HcRed) from the Anthozoa coral Heteractis crispa

Mircea Cotlet, Satoshi Habuchi, Jennifer Whitier, James Werner, Frans De Schryver, Johan Hofkens, Peter Goodwin

Proceedings Volume 6098, 609804 (2006) https://doi.org/10.1117/12.646811

KEYWORDS: Luminescence, Chromophores, Proteins, Molecules, Molecular spectroscopy, Fluorescence spectroscopy, Green fluorescent protein, Absorption, Spectroscopy, Fluorescent proteins

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We report on the photophysical properties of a far-red intrinsic fluorescent protein by means of single molecule and ensemble spectroscopic methods. The green fluorescent protein (GFP) from Aequorea victoria is a popular fluorescent marker with genetically encoded fluorescence and which can be fused to any biological structure without affecting its function. GFP and its variants provide emission colors from blue to yellowish green. Red intrinsic fluorescent proteins from Anthozoa species represent a recent addition to the emission color palette provided by GFPs. Red intrinsic fluorescent markers are on high demand in protein-protein interaction studies based on fluorescence-resonance energy transfer or in multicolor tracking studies or in cellular investigations where autofluorescence possesses a problem. Here we address the photophysical properties of a far-red fluorescent protein (HcRed), a mutant engineered from a chromoprotein cloned from the sea anemone Heteractis crispa, by using a combination of ensemble and single molecule spectroscopic methods. We show evidence for the presence of HcRed protein as an oligomer and for incomplete maturation of its chromophore. Incomplete maturation results in the presence of an immature (yellow) species absorbing/fluorescing at 490/530-nm. This yellow chromophore is involved in a fast resonance-energy transfer with the mature (purple) chromophore. The mature chromophore of HcRed is found to adopt two conformations, a Transoriented form absorbing and 565-nm and non-fluorescent in solution and a Cis-oriented form absorbing at 590-nm and emitting at 645-nm. These two forms co-exist in solution in thermal equilibrium. Excitation-power dependence fluorescence correlation spectroscopy of HcRed shows evidence for singlet-triplet transitions in the microseconds time scale and for cis-trans isomerization occurring in a time scale of tens of microseconds. Single molecule fluorescence data recorded from immobilized HcRed proteins, all point to the presence of two classes of molecules: proteins with Cis and Trans-oriented chromophores. Immobilization of HcRed in water-filled pores of polyvinyl alcohol leads to a polymer matrix - protein barrel interaction which results in a 'freezing' of the chromophore in a stable conformation for which non-radiative deactivation pathways are either suppressed or reduced. As a result, proteins with both Cis- and Trans-oriented chromophores can be detected at the single molecule level. Polymer chain motion is suggested as a mediator for an eventual cis-trans isomerization of the chromophore in the case of single immobilized proteins.

Proceedings Article | 1 July 2004 Paper

Single-molecule spectroscopy to probe competitive fluorescence resonance energy transfer pathways in bichromophoric synthetic systems

Mircea Cotlet, Tom Vosch, Sadahiro Masuo, Marcus Sauer, Klaus Muellen, Johan Hofkens, Frans De Schryver

Proceedings Volume 5322, (2004) https://doi.org/10.1117/12.531322

KEYWORDS: Molecules, Chromophores, Luminescence, Energy transfer, Fluorescence resonance energy transfer, Polymers, Molecular energy transfer, Absorption, Pulsed laser operation, Single molecule spectroscopy

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Proceedings Article | 14 June 2004 Paper

Spectroscopy and microscopy of the autofluorescent protein DsRed from Discosoma genus coral

Mircea Cotlet, Satoshi Habuchi, Frans De Schryver, Johan Hofkens

Proceedings Volume 5329, (2004) https://doi.org/10.1117/12.531313

KEYWORDS: Chromophores, Luminescence, Molecules, Proteins, Fluorescence spectroscopy, Absorption, Green fluorescent protein, Polarization, Spectroscopy, Fluorescence resonance energy transfer

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Proceedings Article | 14 June 2004 Paper

Single molecule surface enhanced resonance Raman scattering (SERRS) of the enhanced green fluorescent protein (EGFP)

Johan Hofkens, Frans De Schryver, Mircea Cotlet, Satoshi Habuchi

Proceedings Volume 5329, (2004) https://doi.org/10.1117/12.531307

KEYWORDS: Molecules, Raman spectroscopy, Proteins, Silver, Luminescence, Chromophores, Resonance enhancement, Particles, Raman scattering, Green fluorescent protein

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Proceedings Article | 19 June 2003 Paper

Excited state processes in individual multichromophoric systems

Johan Hofkens, Tom Vosch, Mircea Cotlet, Satoshi Habuchi, Koen Van Der Biest, Klaus Mullen, Gunter Dirix, Jan Michiels, Jos Vanderleyden, Markus Sauer, Frans De Schryver

Proceedings Volume 4962, (2003) https://doi.org/10.1117/12.488209

KEYWORDS: Chromophores, Luminescence, Dendrimers, Molecules, Photons, Polarization, Polymers, Fluorescent proteins, Absorption, Proteins

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Showing 5 of 15 publications

Conference Committee Involvement (19)

Single Molecule Spectroscopy and Superresolution Imaging XVIII

25 January 2025 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging XVII

27 January 2024 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging XVI

28 January 2023 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging XV

22 January 2022 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging XIV

6 March 2021 | Online Only, California, United States

Single Molecule Spectroscopy and Superresolution Imaging XIII

1 February 2020 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging XII

2 February 2019 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging XI

27 January 2018 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging X

28 January 2017 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging IX

13 February 2016 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging VIII

7 February 2015 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging VII

1 February 2014 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging VI

2 February 2013 | San Francisco, California, United States

Single Molecule Spectroscopy and Superresolution Imaging V

21 January 2012 | San Francisco, California, United States

Single Molecule Spectroscopy and Imaging III

23 January 2010 | San Francisco, California, United States

Single Molecule Spectroscopy and Imaging II

24 January 2009 | San Jose, California, United States

Single Molecule Spectroscopy and Imaging

19 January 2008 | San Jose, California, United States

Ultrasensitive and Single-Molecule Detection Technologies II

20 January 2007 | San Jose, California, United States

Ultrasensitive and Single-Molecule Detection Technologies

21 January 2006 | San Jose, California, United States

Showing 5 of 19 Conference Committees

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