Takuya Fabian Segawa

Last Name

Segawa

First Name

Takuya Fabian

ORCID

0000-0001-5507-3360

Organisational unit

02543 - Inst. f. Molekulare Physikalische Wiss. / Institute of Molecular Physical Science

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Publications 1 - 9 of 9

Exchange rate constants of invisible protons in proteins determined by NMR spectroscopy
Segawa, Takuya Fabian; Kateb, Fatiha; Duma, Luminita; et al. (2008)
ChemBioChem
Fabrication of Detonation Nanodiamonds Containing Silicon‐Vacancy Color Centers by High Temperature Annealing
Shimazaki, Konosuke; Kawaguchi, Hiroki; Takashima, Hideaki; et al. (2021)
Physica Status Solidi A
Detonation nanodiamonds (DNDs) with sizes below 10 nm have attracted attention as single photon emitters with potential in many research fields from life sciences to quantum technologies. However, while nitrogen-vacancy (NV) color centers are found in nanodiamonds directly after the detonation synthesis without the need for irradiation or annealing, silicon-vacancy (SiV) color centers are not present in these pristine samples. Herein, SiV centers are created in DNDs by an annealing treatment up to 1100 °C in high vacuum. As silicon is not added, the precursor of the SiV centers must be pristine silicon impurities inside the nanodiamond lattice. A sharp emission line at the wavelength of 737 nm with a linewidth of 7.7 nm is observed in DNDs that are electron irradiated before annealing. This wavelength is consistent with the characteristic emission line of SiV centers and its linewidth is comparable with that in larger nanodiamonds created by chemical vapor deposition and subsequent milling. The average lifetime (0.4 ± 0.04 ns) of the fluorescence, which is in the range of reported lifetimes in nanodiamonds, also support that the observed emission peak are due to SiV centers in DNDs.
Nanoscale quantum sensing with nitrogen-vacancy centers in nanodiamonds – A magnetic resonance perspective
Segawa, Takuya Fabian; Igarashi, Ryuji (2022)
Progress in Nuclear Magnetic Resonance Spectroscopy
Nanodiamonds containing fluorescent Nitrogen-Vacancy (NV) centers are the smallest single particles, of which a magnetic resonance spectrum can be recorded at room temperature using optically-detected magnetic resonance (ODMR). By recording spectral shift or changes in relaxation rates, various physical and chemical quantities can be measured such as the magnetic field, orientation, temperature, radical concentration, pH or even NMR. This turns NV-nanodiamonds into nanoscale quantum sensors, which can be read out by a sensitive fluorescence microscope equipped with an additional magnetic resonance upgrade. In this review, we introduce the field of ODMR spectroscopy of NV-nanodiamonds and how it can be used to sense different quantities. Thereby we highlight both, the pioneering contributions and the latest results (covered until 2021) with a focus on biological applications.
Multidimensional Spectroscopy of Nuclear Spin Clusters in Diamond
Herb, Konstantin; Segawa, Takuya Fabian; Völker, Laura A.; et al. (2024)
Physical Review Letters
Optically active spin defects in solids offer promising platforms to investigate nuclear spin clusters with high sensitivity and atomic-site resolution. To leverage near-surface defects for molecular structure analysis in chemical and biological contexts using nuclear magnetic resonance (NMR), further advances in spectroscopic characterization of nuclear environments are essential. Here, we report Fourier spectroscopy techniques to improve localization and mapping of the test bed ¹³C nuclear spin environment of individual, shallow nitrogen-vacancy centers at room temperature. We use multidimensional spectroscopy, well-known from classical NMR, in combination with weak measurements of single-nuclear-spin precession. We demonstrate two examples of multidimensional NMR: (i) improved nuclear spin localization by separate encoding of the two hyperfine components along spectral dimensions and (ii) spectral editing of nuclear-spin pairs, including measurement of internuclear coupling constants. Our work adds important tools for the spectroscopic analysis of molecular structures by single-spin probes.
Copper ESEEM and HYSCORE through ultra-wideband chirp EPR spectroscopy
Segawa, Takuya Fabian; Doll, Andrin; Pribitzer, Stephan; et al. (2015)
The Journal of Chemical Physics
Distance measurements between 5 nanometer diamonds – single particle magnetic resonance or optical super-resolution imaging?
Pinotsi, Dorothea; Tian, Rui; Anand, Pratyush; et al. (2023)
Nanoscale Advances
5 nanometer sized detonation nanodiamonds (DNDs) are studied as potential single-particle labels for distance measurements in biomolecules. Nitrogen-vacancy (NV) defects in the crystal lattice can be addressed through their fluorescence and optically-detected magnetic resonance (ODMR) of a single particle can be recorded. To achieve single-particle distance measurements, we propose two complementary approaches based on spin–spin coupling or optical super-resolution imaging. As a first approach, we try to measure the mutual magnetic dipole–dipole coupling between two NV centers in close DNDs using a pulse ODMR sequence (DEER). The electron spin coherence time, a key parameter to reach long distance DEER measurements, was prolonged using dynamical decoupling reaching T2,DD ≈ 20 μs, extending the Hahn echo decay time T2 by one order of magnitude. Nevertheless, an inter-particle NV–NV dipole coupling could not be measured. As a second approach, we successfully localize the NV centers in DNDs using STORM super-resolution imaging, achieving a localization precision of down to 15 nm, enabling optical nanometer-scale single-particle distance measurements.
A simple and soft chemical deaggregation method producing single-digit detonation nanodiamonds
Terada, Daiki; So, Frederick Tze Kit; Hattendorf, Bodo; et al. (2022)
Nanoscale Advances
Detonation nanodiamonds (DNDs) are a class of very small and spherical diamond nanocrystals. They are used in polymer reinforcement materials or as drug delivery systems in the field of nanomedicine. Synthesized by detonation, only the final deaggregation step down to the single-digit nanometer size (<10 nm) unfolds their full potential. Existing deaggregation methods mainly rely on mechanical forces, such as high-power sonication or bead milling. These techniques entail drawbacks such as contamination of the sample and the need for a specialized apparatus. In this paper, we report a purely chemical deaggregation method by simply combining oxidation in air followed by a boiling acid treatment, to produce highly stable single-digit DNDs in a suspension. The resulting DNDs are surface functionalized with carboxyl groups, the final boiling acid treatment removes primary metal contaminants such as magnesium, iron or copper and the nanoparticles remain dispersed over a wide pH range. Our method can be easily carried out in a standard chemistry laboratory with commonly available laboratory apparatus. This is a key step for many DND-based applications, ranging from materials science to biological or medical applications.
Fragment Screening and Fast Micromolar Detection on a Benchtop NMR Spectrometer Boosted by Photoinduced Hyperpolarization
Stadler, Gabriela Ruth; Segawa, Takuya Fabian; Bütikofer, Matthias; et al. (2023)
Angewandte Chemie. International Edition
Fragment-based drug design is a well-established strategy for rational drug design, with nuclear magnetic resonance (NMR) on high-field spectrometers as the method of reference for screening and hit validation. However, high-field NMR spectrometers are not only expensive, but require specialized maintenance, dedicated space, and depend on liquid helium cooling which became critical over the recurring global helium shortages. We propose an alternative to high-field NMR screening by applying the recently developed approach of fragment screening by photoinduced hyperpolarized NMR on a cryogen-free 80 MHz benchtop NMR spectrometer yielding signal enhancements of up to three orders in magnitude. It is demonstrated that it is possible to discover new hits and kick-off drug design using a benchtop NMR spectrometer at low micromolar concentrations of both protein and ligand. The approach presented performs at higher speed than state-of-the-art high-field NMR approaches while exhibiting a limit of detection in the nanomolar range. Photoinduced hyperpolarization is known to be inexpensive and simple to be implemented, which aligns greatly with the philosophy of benchtop NMR spectrometers. These findings open the way for the use of benchtop NMR in near-physiological conditions for drug design and further life science applications.
Nanodiamonds for bioapplications–specific targeting strategies
Terada, Daiki; Genjo, Takuya; Segawa, Takuya Fabian; et al. (2020)
Biochimica et Biophysica Acta (BBA) - General Subjects
Background Nanodiamonds (NDs) provide a unique multitasking system for drug delivery and fluorescent imaging in biological environments. Owing to their quantum properties, NDs are expected to be employed as multifunctional probes in the future for the accurate visualization of biophysical parameters such as temperature and magnetic fields. However, the use of NDs for the selective targeting of the biomolecules of interest within a complicated biological system remains a challenge. One of the most promising solutions is the appropriate surface design of NDs based on organic chemistry and biochemistry. The engineered NDs have high biocompatibility and dispersibility in a biological environment and hence undergo cellular uptake through specific pathways. Scope of review This review focuses on the selective targeting of NDs for biomedical and biophysical applications from the viewpoint of ND surface functionalizations and modifications. These pretreatments make possible the specific targeting of biomolecules of interest on or in a cell by NDs via a designed biochemical route. Major conclusions The surface of NDs is covalently or noncovalently modified with silica, polymers, or biomolecules to reshape them, control their size, and enhance the colloidal stability and biomolecular selectivity toward the biomolecules of interest. Electroporation, chemical treatment, injection, or endocytosis are the methods generally adopted to introduce NDs into living cells. The pathway, efficiency, and the cell viability depend on the selected method. General significance In the biomedical field, the surface modification facilitates specific delivery of a drug, leading to a higher therapeutic efficacy. In biophysical applications, the surface modification paves the way for the accurate measurement of physical parameters to gain a better understanding of various cell functions.

Publications 1 - 9 of 9

Takuya Fabian Segawa

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