Engineering Ba2Bi2O6 Double Perovskite with La3+ for High Current Density Visible Light Photoelectrochemical Hydrogen Evolution.

A Lanthanum ion (La3+) incorporation strategy is implemented to modify Ba2Bi2O6-based double perovskite photoelectrodes. X-ray diffraction (XRD) characterization shows that highly crystalline Ba2La0.4Bi1.6O6 double perovskites with the space group I2/m are successfully prepared. UV-vis absorption spectra and the Tauc-plot reveal an optical band gap Eg ≈1.57 ± 0.01 eV. A thickness dependence of the photoelectrodes photoelectrochemical (PEC) performance shows that the submicron (≈1 µm) 4-times spin-coated thin film photoelectrode displays strong p-type conductivity, which delivers an encouraging photocurrent density of 0.88 mA cm-2 at 0.25 VRHE under AM 1.5G illumination. 10-times coated and 20-times coated medium thick (125.8-197 µm) photoelectrodes that exhibit moderate p-type conductivity, show further enhanced photocurrent densities of 1.5 mA cm-2 at 0 VRHE. In contrast, charge recombination centers existing in a standard thick pellet (≈500 µm) Ba2La0.4Bi1.6O6 photoelectrode can quench photo-generated charge carriers and greatly undermine PEC activities. The approach to doping at the Bi(III) sites contrasts with earlier efforts that focus on doping at the Bi(V) sites and thus paves the way for further tailoring a family of novel promising photocathode materials for efficient solar-water conversion devices.

Contrasting packing modes for tubular assemblies in chlorosomes.

The largest light-harvesting antenna in nature, the chlorosome, is a heterogeneous helical BChl self-assembly that has evolved in green bacteria to harvest light for performing photosynthesis in low-light environments. Guided by NMR chemical shifts and distance constraints for Chlorobaculum tepidum wild-type chlorosomes, the two contrasting packing modes for syn-anti parallel stacks of BChl c to form polar 2D arrays, with dipole moments adding up, are explored. Layered assemblies were optimized using local orbital density functional and plane wave pseudopotential methods. The packing mode with the lowest energy contains syn-anti and anti-syn H-bonding between stacks. It can accommodate R and S epimers, and side chain variability. For this packing, a match with the available EM data on the subunit axial repeat and optical data is obtained with multiple concentric cylinders for a rolling vector with the stacks running at an angle of 21° to the cylinder axis and with the BChl dipole moments running at an angle ߠ∼ 55° to the tube axis, in accordance with optical data. A packing mode involving alternating syn and anti parallel stacks that is at variance with EM appears higher in energy. A weak cross-peak at -6 ppm in the MAS NMR with 50 kHz spinning, assigned to C-181, matches the shift of antiparallel dimers, which possibly reflects a minor impurity-type fraction in the self-assembled BChl c.

Ultrahigh field diffusion magnetic resonance imaging uncovers intriguing microstructural changes in the adult zebrafish brain caused by Toll-like receptor 2 genomic deletion.

Toll-like receptor 2 (TLR2) belongs to the TLR protein family that plays an important role in the immune and inflammation response system. While TLR2 is predominantly expressed in immune cells, its expression has also been detected in the brain, specifically in microglia and astrocytes. Recent studies indicate that genomic deletion of TLR2 can result in impaired neurobehavioural function. It is currently not clear if the genomic deletion of TLR2 leads to any alterations in the microstructural features of the brain. In the current study, we noninvasively assess microstructural changes in the brain of TLR2-deficient (tlr2-/-) zebrafish using state-of-the art magnetic resonance imaging (MRI) methods at ultrahigh magnetic field strength (17.6 T). A significant increase in cortical thickness and an overall trend towards increased brain volumes were observed in young tlr2-/- zebrafish. An elevated T2 relaxation time and significantly reduced apparent diffusion coefficient (ADC) unveil brain-wide microstructural alterations, potentially indicative of cytotoxic oedema and astrogliosis in the tlr2-/- zebrafish. Multicomponent analysis of the ADC diffusivity signal by the phasor approach shows an increase in the slow ADC component associated with restricted diffusion. Diffusion tensor imaging and diffusion kurtosis imaging analysis revealed diminished diffusivity and enhanced kurtosis in various white matter tracks in tlr2-/- compared with control zebrafish, identifying the microstructural underpinnings associated with compromised white matter integrity and axonal degeneration. Taken together, our findings demonstrate that the genomic deletion of TLR2 results in severe alterations to the microstructural features of the zebrafish brain. This study also highlights the potential of ultrahigh field diffusion MRI techniques in discerning exceptionally fine microstructural details within the small zebrafish brain, offering potential for investigating microstructural changes in zebrafish models of various brain diseases.

An integrated approach towards extracting structural characteristics of chlorosomes from a bchQ mutant of Chlorobaculum tepidum.

Chlorosomes, the photosynthetic antenna complexes of green sulfur bacteria, are paradigms for light-harvesting elements in artificial designs, owing to their efficient energy transfer without protein participation. We combined magic angle spinning (MAS) NMR, optical spectroscopy and cryogenic electron microscopy (cryo-EM) to characterize the structure of chlorosomes from a bchQ mutant of Chlorobaculum tepidum. The chlorosomes of this mutant have a more uniform composition of bacteriochlorophyll (BChl) with a predominant homolog, [8Ethyl, 12Ethyl] BChl c, compared to the wild type (WT). Nearly complete 13C chemical shift assignments were obtained from well-resolved homonuclear 13C-13C RFDR data. For proton assignments heteronuclear 13C-1H (hCH) data sets were collected at 1.2 GHz spinning at 60 kHz. The CHHC experiments revealed intermolecular correlations between 132/31, 132/32, and 121/31, with distance constraints of less than 5 Å. These constraints indicate the syn-anti parallel stacking motif for the aggregates. Fourier transform cryo-EM data reveal an axial repeat of 1.49 nm for the helical tubular aggregates, perpendicular to the inter-tube separation of 2.1 nm. This axial repeat is different from WT and is in line with BChl syn-anti stacks running essentially parallel to the tube axis. Such a packing mode is in agreement with the signature of the Qy band in circular dichroism (CD). Combining the experimental data with computational insight suggests that the packing for the light-harvesting function is similar between WT and bchQ, while the chirality within the chlorosomes is modestly but detectably affected by the reduced compositional heterogeneity in bchQ.

Efficient workflow for the investigation of the catalytic cycle of water oxidation catalysts: Combining GFN-xTB and density functional theory.

Photocatalytic water oxidation remains the bottleneck in many artificial photosynthesis devices. The efficiency of this challenging process is inherently linked to the thermodynamic and electronic properties of the chromophore and the water oxidation catalyst (WOC). Computational investigations can facilitate the search for favorable chromophore-catalyst combinations. However, this remains a demanding task due to the requirements on the computational method that should be able to correctly describe different spin and oxidation states of the transition metal, the influence of solvation and the different rates of the charge transfer and water oxidation processes. To determine a suitable method with favorable cost/accuracy ratios, the full catalytic cycle of a molecular ruthenium based WOC is investigated using different computational methods, including density functional theory (DFT) with different functionals (GGA, Hybrid, Double Hybrid) as well as the semi-empirical tight binding approach GFN-xTB. A workflow with low computational cost is proposed that combines GFN-xTB and DFT and provides reliable results. GFN-xTB geometries and frequencies combined with single-point DFT energies give free energy changes along the catalytic cycle that closely follow the full DFT results and show satisfactory agreement with experiment, while significantly decreasing the computational cost. This workflow allows for cost efficient determination of energetic, thermodynamic and dynamic properties of WOCs.

The Resting Oxidized State of Small Laccase Analyzed with Paramagnetic NMR Spectroscopy.

The enzyme laccase catalyzes the reduction of dioxygen to water at the trinuclear copper center (TNC). The TNC comprises a type-3 (T3) and a type-2 (T2) copper site. The paramagnetic NMR spectrum of the small laccase from Streptomyces coelicolor (SLAC) without the substrate shows a mixture of two catalytic states, the resting oxidized (RO) state and the native intermediate (NI) state. An analysis of the resonances of the RO state is reported. In this state, hydrogen resonances only of the T3 copper ligands can be found, in the region of 12-22 ppm. Signals from all six histidine ligands are found and can be attributed to Hδ1, Hß or backbone amide HN nuclei. Two sequence-specific assignments are proposed on the basis of a second-coordination shell variant that also lacks the copper ion at the T1 site, SLAC-T1D/Q291E. This double mutant is found to be exclusively in the RO state, revealing a subtle balance between the RO and the NI states.

Dipolar dephasing for structure determination in a paramagnetic environment.

We demonstrate the efficacy of the REDOR-type sequences in determining dipolar coupling strength in a paramagnetic environment. Utilizing paramagnetic effects of enhanced relaxation rates and rapid electronic fluctuations in Cu(II)-(DL-Ala)2.H2O, the dipolar coupling for the methyl C-H that is 4.20 â€‹Å (methyl carbon) away from the Cu2+ ion, was estimated to be 8.8 â€‹± â€‹0.6 â€‹kHz. This coupling is scaled by a factor of ~0.3 in comparison to the rigid limit value of ~32 â€‹kHz, in line with partial averaging of the dipolar interaction by rotational motion of the methyl group. Limited variation in the scaling factor of the dipolar coupling strength at different temperatures is observed. The C-H internuclear distance derived from the size of the dipolar coupling is similar to that observed in the crystal structure. The errors in the dipolar coupling strength observed in the REDOR-type experiments are similar to those reported for diamagnetic systems. Increase in resolution due to the Fermi contact shifts, coupled with MAS frequencies of 30-35 â€‹kHz allowed to estimate the hyperfine coupling strengths for protons and carbons from the temperature dependence of the chemical shift and obtain a high resolution 1H-1H spin diffusion spectrum. This study shows the utility of REDOR-type sequences in obtaining reliable structural and dynamical information from a paramagnetic complex. We believe that this can help in studying the active site of paramagnetic metalloproteins at high resolution.

HR-MAS NMR Applications in Plant Metabolomics.

Metabolomics is used to reduce the complexity of plants and to understand the underlying pathways of the plant phenotype. The metabolic profile of plants can be obtained by mass spectrometry or liquid-state NMR. The extraction of metabolites from the sample is necessary for both techniques to obtain the metabolic profile. This extraction step can be eliminated by making use of high-resolution magic angle spinning (HR-MAS) NMR. In this review, an HR-MAS NMR-based workflow is described in more detail, including used pulse sequences in metabolomics. The pre-processing steps of one-dimensional HR-MAS NMR spectra are presented, including spectral alignment, baseline correction, bucketing, normalisation and scaling procedures. We also highlight some of the models which can be used to perform multivariate analysis on the HR-MAS NMR spectra. Finally, applications of HR-MAS NMR in plant metabolomics are described and show that HR-MAS NMR is a powerful tool for plant metabolomics studies.

Chemical Exchange at the Trinuclear Copper Center of Small Laccase from Streptomyces coelicolor.

The trinuclear copper center (TNC) of laccase reduces oxygen to water with very little overpotential. The arrangement of the coppers and ligands in the TNC is known to be from many crystal structures, yet information about possible dynamics of the ligands is absent. Here, we report dynamics at the TNC of small laccase from Streptomyces coelicolor using paramagnetic NMR and electron paramagnetic resonance spectroscopy. Fermi contact-shifted resonances tentatively assigned to histidine Hδ1 display a two-state chemical exchange with exchange rates in the order of 100 s-1. In the electron paramagnetic resonance spectra, at least two forms are observed with different gz-values. It is proposed that the exchange processes reflect the rotational motion of histidine imidazole rings that coordinate the coppers in the TNC.

A Molecular Level Approach To Elucidate the Supramolecular Packing of Light-Harvesting Antenna Systems.

The molecular geometry and supramolecular packing of two bichromophoric prototypic light harvesting compounds D1A2 and D2A2, consisting of two naphthylimide energy donors that were attached to the 1,7 bay positions of a perylene monoimide diester energy acceptor, have been determined by a hybrid approach using magic angle spinning NMR spectroscopy and electron nano-crystallography (ENC), followed by modelling. NMR shift constraints, combined with the P 1 ‾ space group obtained from ENC, were used to generate a centrosymmetric dimer of truncated perylene fragments. This racemic packing motif is used in a biased molecular replacement approach to generate a partial 3D electrostatic scattering potential map. Resolving the structure of the bay substituents is guided by the inversion symmetry, and the distance constraints obtained from heteronuclear correlation spectra. The antenna molecules form a pseudocrystalline lattice of antiparallel centrosymmetric dimers with pockets of partially disordered bay substituents. The two molecules in a unit cell form a butterfly-type arrangement. The hybrid methodology that has been developed is robust and widely applicable for critical structural underpinning of self-assembling structures of large organic molecules.

Retinal-Based Proton Pumping in the Near Infrared.

Proteorhodopsin (PR) and Gloeobacter rhodopsin (GR) are retinal-based light-driven proton pumps that absorb visible light (maxima at 520-540 nm). Shifting the action spectra of these proton pumps beyond 700 nm would generate new prospects in optogenetics, membrane sensor technology, and complementation of oxygenic phototrophy. We therefore investigated the effect of red-shifting analogues of retinal, combined with red-shifting mutations, on the spectral properties and pump activity of the resulting pigments. We investigated a variety of analogues, including many novel ones. One of the novel analogues we tested, 3-methylamino-16-nor-1,2,3,4-didehydroretinal (MMAR), produced exciting results. This analogue red-shifted all of the rhodopsin variants tested, accompanied by a strong broadening of the absorbance band, tailing out to 850-950 nm. In particular, MMAR showed a strong synergistic effect with the PR-D212N,F234S double mutant, inducing an astonishing 200 nm red shift in the absorbance maximum. To our knowledge, this is by far the largest red shift reported for any retinal protein. Very importantly, all MMAR-containing holoproteins are the first rhodopsins retaining significant pump activity under near-infrared illumination (730 nm light-emitting diode). Such MMAR-based rhodopsin variants present very promising opportunities for further synthetic biology modification and for a variety of biotechnological and biophysical applications.

Determination of Controlled Self-Assembly of a Paracrystalline Material by Homology Modelling with Hybrid NMR and TEM.

Controlling complexity, flexibility, and functionality of synthetic and biomimetic materials requires insight into how molecular functionalities can be exploited for steering their packing. A fused NDI-salphen (NDI=naphthalene diimide) prototypic artificial photosynthesis material, DATZnS, is shown to be comprised of a phenazine motif, in which the alignment of electric dipole moments in a P2/c supramolecular scaffold can be modulated with bulky substituents. They can also be switched between parallel stacks of dipoles running antiparallel in the DATZnS-H compared with parallel stacks of dipoles in polar layers running in opposite directions in the DATZnS(3'-NMe) parent compound. Spatial correlations obtained from HETCOR spectra, collected with a long cross polarization contact time of 2 ms, reveal an antiparallel stacking for the DATZnS-H homologue. These constraints and limited data from TEM are used to construct a structural model within the P2/c space group determined by the molecular C2 symmetry. By using homology modelling, a pseudo octahedral coordination of the Zn is shown to follow the packing-induced chirality with enantiomeric pairs of the Λ and Δ forms alternating along antiparallel stacks. The model helps to understand how the steric hindrance modulates the self-assembly in this novel class of fused materials by steric hindrance at the molecular level.

A Hybrid Solid-State NMR and Electron Microscopy Structure-Determination Protocol for Engineering Advanced para-Crystalline Optical Materials.

Hybrid magic-angle spinning (MAS) NMR spectroscopy and TEM were demonstrated for de novo structure determination of para-crystalline materials with a bioinspired fused naphthalene diimide (NDI)-salphen-phenazine prototype light-harvesting compound. Starting from chiral building blocks with C2 molecular symmetry, the asymmetric unit was determined by MAS NMR spectroscopy, index low-resolution TEM diffraction data, and resolve reflection conditions, and for the first time the ability to determine the space group from reciprocal space data using this hybrid approach was shown. Transfer of molecular C2 symmetry into P2/c packing symmetry provided a connection across length scales to overcome both lack of long-range order and missing diffraction-phase information. Refinement with heteronuclear distance constraints confirmed the racemic P2/c packing that was scaffolded by molecular recognition of salphen zinc in a pseudo-octahedral environment with bromide and with alkyl chains folding along the phenazine. The NDI light-harvesting stacks ran orthogonal to the intermolecular electric dipole moment present in the solid. Finally, the orientation of flexible lamellae on an electrode surface was determined.

Modulation of spectral properties and pump activity of proteorhodopsins by retinal analogues.

Proteorhodopsins are heptahelical membrane proteins which function as light-driven proton pumps. They use all-trans-retinal A1 as a ligand and chromophore and absorb visible light (520-540 nm). In the present paper, we describe modulation of the absorbance band of the proteorhodopsin from Monterey Bay SAR 86 gammaproteobacteria (PR), its red-shifted double mutant PR-D212N/F234S (PR-DNFS) and Gloeobacter rhodopsin (GR). This was approached using three analogues of all-trans-retinal A1, which differ in their electronic and conformational properties: all-trans-6,7-s-trans-locked retinal A1, all-trans-phenyl-retinal A1 and all-trans-retinal A2. We further probed the effect of these retinal analogues on the proton pump activity of the proteorhodopsins. Our results indicate that, whereas the constraints of the retinal-binding pocket differ for the proteorhodopsins, at least two of the retinal analogues are capable of shifting the absorbance bands of the pigments either bathochromically or hypsochromically, while maintaining their proton pump activity. Furthermore, the shifts implemented by the analogues add up to the shift induced by the double mutation in PR-DNFS. This type of chromophore substitution may present attractive applications in the field of optogenetics, towards increasing the flexibility of optogenetic tools or for membrane potential probes.

Insights into the photoprotective switch of the major light-harvesting complex II (LHCII): a preserved core of arginine-glutamate interlocked helices complemented by adjustable loops.

Light-harvesting antennae of the LHC family form transmembrane three-helix bundles of which two helices are interlocked by conserved arginine-glutamate (Arg-Glu) ion pairs that form ligation sites for chlorophylls. The antenna proteins of photosystem II have an intriguing dual function. In excess light, they can switch their conformation from a light-harvesting into a photoprotective state, in which the excess and harmful excitation energies are safely dissipated as heat. Here we applied magic angle spinning NMR and selective Arg isotope enrichment as a noninvasive method to analyze the Arg structures of the major light-harvesting complex II (LHCII). The conformations of the Arg residues that interlock helix A and B appear to be preserved in the light-harvesting and photoprotective state. Several Arg residues have very downfield-shifted proton NMR responses, indicating that they stabilize the complex by strong hydrogen bonds. For the Arg Cα chemical shifts, differences are observed between LHCII in the active, light-harvesting and in the photoprotective, quenched state. These differences are attributed to a conformational change of the Arg residue in the stromal loop region. We conclude that the interlocked helices of LHCII form a rigid core. Consequently, the LHCII conformational switch does not involve changes in A/B helix tilting but likely involves rearrangements of the loops and helical segments close to the stromal and lumenal ends.

An NMR comparison of the light-harvesting complex II (LHCII) in active and photoprotective states reveals subtle changes in the chlorophyll a ground-state electronic structures.

To protect the photosynthetic apparatus against photo-damage in high sunlight, the photosynthetic antenna of oxygenic organisms can switch from a light-harvesting to a photoprotective mode through the process of non-photochemical quenching (NPQ). There is growing evidence that light-harvesting proteins of photosystem II participate in photoprotection by a built-in capacity to switch their conformation between light-harvesting and energy-dissipating states. Here we applied high-resolution Magic-Angle Spinning Nuclear Magnetic Resonance on uniformly (13)C-enriched major light-harvesting complex II (LHCII) of Chlamydomonas reinhardtii in active or quenched states. Our results reveal that the switch into a dissipative state is accompanied by subtle changes in the chlorophyll (Chl) a ground-state electronic structures that affect their NMR responses, particularly for the macrocycle (13)C4, (13)C5 and (13)C6 carbon atoms. Inspection of the LHCII X-ray structures shows that of the Chl molecules in the terminal emitter domain, where excited-state energy accumulates prior to further transfer or dissipation, the C4, 5 and 6 atoms are in closest proximity to lutein; supporting quenching mechanisms that involve altered Chl-lutein interactions in the dissipative state. In addition the observed changes could represent altered interactions between Chla and neoxanthin, which alters its configuration under NPQ conditions. The Chls appear to have increased dynamics in unquenched, detergent-solubilized LHCII. Our work demonstrates that solid-state Nuclear Magnetic Resonance is applicable to investigate high-resolution structural details of light-harvesting proteins in varied functional conditions, and represents a valuable tool to address their molecular plasticity associated with photoprotection.

Covalent Benzenesulfonic Functionalization of a Graphene Nanopore for Enhanced and Selective Proton Transport.

A fundamental understanding of proton transport through graphene nanopores, defects, and vacancies is essential for advancing two-dimensional proton exchange membranes (PEMs). This study employs ReaxFF molecular dynamics, metadynamics, and density functional theory to investigate the enhanced proton transport through a graphene nanopore. Covalently functionalizing the nanopore with a benzenesulfonic group yields consistent improvements in proton permeability, with a lower activation barrier (≈0.15 eV) and increased proton selectivity over sodium cations. The benzenesulfonic functionality acts as a dynamic proton shuttle, establishing a favorable hydrogen-bonding network and an efficient proton transport channel. The model reveals an optimal balance between proton permeability and selectivity, which is essential for effective proton exchange membranes. Notably, the benzenesulfonic-functionalized graphene nanopore system achieves a theoretically estimated proton diffusion coefficient comparable to or higher than the current state-of-the-art PEM, Nafion. Ergo, the benzenesulfonic functionalization of graphene nanopores, firmly holds promise for future graphene-based membrane development in energy conversion devices.

Observation of Dark States in Two-Dimensional Electronic Spectra of Chlorosomes.

Observations of low-lying dark states in several photosynthetic complexes challenge our understanding of the mechanisms behind their efficient energy transfer processes. Computational models are necessary for providing novel insights into the nature and function of dark states, especially since these are not directly accessible in spectroscopy experiments. Here, we will focus on signatures of dark-type states in chlorosomes, a light-harvesting complex from green sulfur bacteria well-known for uniting a broad absorption band with very efficient energy transfer. In agreement with experiments, our simulations of two-dimensional electronic spectra capture the ultrafast exciton transfer occurring in 100s of femtoseconds within a single chlorosome cylinder. The sub-100 fs process corresponds to relaxation within the single-excitation manifold in a single chlorosome tube, where all initially created populations in the bright exciton states are quickly transferred to dark-type exciton states. Structural inhomogeneities on the local scale cause a redistribution of the oscillator strength, leading to the emergence of these dark-type exciton states, which dominate ultrafast energy transfer. The presence of the dark-type exciton states suppresses energy loss from an isolated chlorosome via fluorescence quenching, as observed experimentally. Our results further question whether relaxation to dark-exciton states is a leading process or merely competes with transfer to the baseplate within the photosynthetic apparatus of green sulfur bacteria.

Symmetry break of special pair: photochemically induced dynamic nuclear polarization NMR confirms control by nonaromatic substituents.

Despite the high structural symmetry of cofactor arrangement and protein environment, light-induced electron transfer in photosynthetic reaction centers (RCs) of the purple bacterium Rhodobacter sphaeroides runs selectively over one of the two branches of cofactors. The origin of this functional symmetry break has been debated for several decades. Recently, a crucial role of the substituents has been proposed by theoretical studies [Yamasaki, H.; Takano, Y.; Nakamura, H. J. Phys. Chem. B 2008, 112, 13923-13933]. Photo-CIDNP (photochemically induced dynamic nuclear polarization) MAS (magic angle spinning) NMR demonstrates that indeed the peripheral atoms show opposite electronic effects on both sides of the special pair. While the aromatic system of P(L) receives electron density from its periphery, the electron density of the aromatic ring of P(M) is decreased.

In vivo measurement of transverse relaxation time in the mouse brain at 17.6 T.

PURPOSE: To establish regional T1 and T2 values of the healthy mouse brain at ultra-high magnetic field strength of 17.6 T and to follow regional brain T1 and T2 changes with age. METHODS: In vivo T1 and T2 values in the C57BL/6J mouse brain were followed with age using multislice-multiecho sequence and multiple spin echo saturation recovery with variable repetition time sequence, respectively, at 9.4 and 17.6 T. Gadolinium-tetra-azacyclo-dodecane-tetra-acetic acid phantoms were used to validate in vivo T2 measurements. Student's t-test was used to compare mean relaxation values. RESULTS: A field-dependent decrease in T2 is shown and validated with phantom measurements. T2 values at 17.6 T typically increased with age in multiple brain regions except in the hypothalamus and the caudate-putamen, where a slight decrease was observed. Furthermore, T1 values in various brain regions of young and old mice are presented at 17.6 T. A large gain in signal-to-noise ratio was observed at 17.6 T. CONCLUSIONS: This study establishes for the first time the normative T1 and T2 values at 17.6 T over different mouse brain regions with age. The estimates of in vivo T1 and T2 will be useful to optimize pulse sequences for optimal image contrast at 17.6 T and will serve as baseline values against which disease-related relaxation changes can be assessed in mice.