Photochemically Induced Dynamic Nuclear Polarization: Basic Principles and Applications

Cavagnero, Silvia

doi:10.1002/9780470034590.emrstm1499

Cited by 28 publications

(36 citation statements)

References 80 publications

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“…This sequence takes advantage of heteronuclear polarization transfer from carbon to proton, and it is generally more sensitive than the simple 13 C pulse-acquire experiment. Unlike most steady-state photo-CIDNP pulse sequences [4, 5], 2D 13 C PRINT yields data on both 13 C and 1 H chemical shifts and their covalent connectivities, thus providing important structural information useful for resonance assignments, especially in the context of complex molecules. In addition 13 C PRINT is very useful in the biological context, as it displays very good sensitivity for the side chain of aromatic amino acids as well as for their corresponding 1 H-C α pair.…”

Section: Resultsmentioning

confidence: 99%

Effect of heavy atoms on photochemically induced dynamic nuclear polarization in liquids

Cavagnero

2018

Journal of Magnetic Resonance

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Given its short hyperpolarization time (∼10 s) and mostly non-perturbative nature, photo-chemically induced dynamic nuclear polarization (photo-CIDNP) is a powerful tool for sensitivity enhancement in nuclear magnetic resonance. In this study, we explore the extent of H-detectedC nuclear hyperpolarization that can be gained via photo-CIDNP in the presence of small-molecule additives containing a heavy atom. The underlying rationale for this methodology is the well-known external-heavy-atom (EHA) effect, which leads to significant enhancements in the intersystem-crossing rate of selected photosensitizer dyes from photoexcited singlet to triplet. We exploited the EHA effect upon addition of moderate amounts of halogen-atom-containing cosolutes. The resulting increase in the transient triplet-state population of the photo-CIDNP sensitizer fluorescein resulted in a significant increase in the nuclear hyperpolarization achievable via photo-CIDNP in liquids. We also explored the internal-heavy-atom (IHA) effect, which is mediated by halogen atoms covalently incorporated into the photosensitizer dye. Widely different outcomes were achieved in the case of EHA and IHA, with EHA being largely preferable in terms of net hyperpolarization.

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Section: Resultsmentioning

confidence: 99%

Effect of heavy atoms on photochemically induced dynamic nuclear polarization in liquids

Cavagnero

2018

Journal of Magnetic Resonance

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“…too short lived for EPR (Closs and Trifunac, 1969;Morozova et al, 2008;Morozova et al, 2007;Morozova et al, 2005), to study protein folding (Kaptein et al, 1978), or to study electron-transfer mechanism (Morozova et al, 2018;Morozova et al, 2008;Morozova et al, 2005;Morozova et al, 2003). The radical pair mechanism is extensively described in different papers, that we recommend to the reader for a deeper understanding (Goez, 1995;Morozova and Ivanov, 2019;Okuno and Cavagnero, 2017). Robert Kaptein's key role in the development of the theory underlying the CIDNP mechanism is crystallized in the Kaptein rules which capture the theory of CIDNP into a simple equation in order to qualitatively analyze the sign of an anomalous CIDNP line (Kaptein, 1971).…”

Section: Discussion Open Accessmentioning

confidence: 99%

Exploration of the close chemical space of tryptophan and tyrosine reveals importance of hydrophobicity in photo-CIDNP performances

Torres¹,

Renn²,

Riek³

2021

Preprint

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Abstract. Sensitivity being one of the main hurdles of Nuclear Magnetic Resonance (NMR) can be gained by polarization techniques including Chemical Induced Dynamic Nuclear Polarization (CIDNP). Kaptein demonstrated that in CIDNP the polarization arises from the formation and the recombination of a radical pair in a magnetic field. In photo-CIDNP of interest here the radical pair is between a dye and the molecule to be polarized. The polarization obtained is thereby dependent on a complex interplay between the two molecules and their physico chemical properties. Here, we explore photo-CIDNP with a set of ten tryptophan and tyrosine analogs and observe not only signal enhancement of two orders of magnitude for 1H at 600 MHz (corresponding to 10'000 times in measurement time), but also reveal that the hydrophobicity of the molecule appears to be an important factor in the polarisation extend. Furthermore, the small chemical library established indicate the existence of many photo-CIDNP active molecules.

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“…This result can be rationalized upon considering the larger surface area and added geometrical constraints of proteins relative to free amino acids, leading to an expected decrease in collision efficiency. Alternative non-photo-CIDNP reaction pathways (e.g., reductive electron transfer) may also play a role in photo-CIDNP of proteins (38). Despite the above caveat, the ability to detect proteins at 500 nM concentration and site-specific resolution in solution under mild, physiologically relevant conditions is unprecedented and simple to achieve with our experimental setup.…”

Section: Combining Laser-enhanced Nmr With a Cryogenic Probe Leads Tomentioning

confidence: 99%

“…Low Sample Concentration. Earlier theoretical and experimental work (25,38) showed that at high and moderate sample concentration (i.e., >5 μM), photo-CIDNP enhancement is proportional to the steady-state concentration of triplet photoexcited dye [ T1 D SS ]. On the other hand, the scenario is significantly different at lower sample concentration (e.g., 500 nM).…”

Section: Lc-photo-cidnp Depends Only Weakly On Laser Power At Extremelymentioning

confidence: 99%

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Laser- and cryogenic probe-assisted NMR enables hypersensitive analysis of biomolecules at submicromolar concentration

Okuno

Mecha

Yang

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Solution-state NMR typically requires 100 μM to 1 mM samples. This limitation prevents applications to mass-limited and aggregationprone target molecules. Photochemically induced dynamic nuclear polarization was adapted to data collection on low-concentration samples by radiofrequency gating, enabling rapid 1D NMR spectral acquisition on aromatic amino acids and proteins bearing aromatic residues at nanomolar concentration, i.e., a full order of magnitude below other hyperpolarization techniques in liquids. Both backbone H 1 -C 13 and side-chain resonances were enhanced, enabling secondary and tertiary structure analysis of proteins with remarkable spectral editing, via the 13 C PREPRINT pulse sequence. Laser-enhanced 2D NMR spectra of 5 μM proteins at 600 MHz display 30-fold better S/N than conventional 2D data collected at 900 MHz. Sensitivity enhancements achieved with this technology, denoted as low-concentration photo-CIDNP (LC-photo-CIDNP), depend only weakly on laser intensity, highlighting the opportunity of safer and more cost-effective hypersensitive NMR applications employing low-power laser sources. hyperpolarization | photo-CIDNP | NMR | proteins | amino acids N MR is an atomic-resolution noninvasive method to probe molecular structure and dynamics. This technique is, however, inherently insensitive due to the unfavorable distribution of nuclear spin states at the near-ambient temperature used in most applications. Methods implemented over the years to overcome the low sensitivity of NMR in liquids include the use of high applied magnetic fields, data acquisition in the time domain followed by Fourier transform, fast data collection schemes, and cryogenic probes (1-3). More recently, nuclear-spin hyperpolarization including Overhauser dynamic nuclear polarization (4, 5), optical pumping (6-9), parahydrogen-induced polarization (10, 11), signal amplification by reversible exchange (12), and dissolution dynamic nuclear polarization (D-DNP) (13-17) have displayed significant potential (3).Despite the above technological advances, typical liquid-state NMR experiments employing hyperpolarization still require very expensive instrumentation; harsh hyperpolarization conditions; long polarization times; and last but not least, ≥50-100 μM sample concentration. In addition, NMR data collection of dilute biomolecules in physiologically relevant milieux is often unfeasible. While some of the above challenges may in principle be overcome by concentrating NMR samples and employing probes accommodating small sample volumes, this process is often unfeasible due to limited amounts of available material or to undesirable aggregation. In summary, there is a compelling need to further enhance the sensitivity of solution-state NMR spectroscopy.Photochemically induced dynamic nuclear polarization (photo-CIDNP) is a spin-selective technique involving the transient generation of radical pairs (Fig. 1A). This methodology has been traditionally employed to gauge macromolecular solventexposure (18)(19)(20). More recently, phot...

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Photochemically Induced Dynamic Nuclear Polarization: Basic Principles and Applications

Cited by 28 publications

References 80 publications

Effect of heavy atoms on photochemically induced dynamic nuclear polarization in liquids

Effect of heavy atoms on photochemically induced dynamic nuclear polarization in liquids

Exploration of the close chemical space of tryptophan and tyrosine reveals importance of hydrophobicity in photo-CIDNP performances

Laser- and cryogenic probe-assisted NMR enables hypersensitive analysis of biomolecules at submicromolar concentration

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