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Magnetic resonance imaging (MRI) has become a popular modality in guiding minimally invasive thermal therapies, due to its advanced, nonionizing, imaging capabilities and its ability to record changes in temperature. A variety of MR thermometry techniques have been developed over the years, and proton resonance frequency (PRF) shift thermometry is the current clinical gold standard to treat a variety of cancers. It is used extensively to guide hyperthermic thermal ablation techniques such as high-intensity focused ultrasound (HIFU) and laser-induced thermal therapy (LITT). Essential attributes of PRF shift thermometry include excellent linearity with temperature, good sensitivity, and independence from tissue type. This noninvasive temperature mapping method gives accurate quantitative measures of the temperature evolution inside biological tissues. In this review, the current status and new developments in the fields of MR-guided HIFU and LITT are presented with an emphasis on breast, prostate, bone, uterine, and brain treatments.Level of Evidence 5Technical Efficacy Stage 3 The project was co-financed by the European Regional Development Fund (ERDF) under Ireland’s European Structural, Investment Funds Programme 2014–2020 and Enterprise Ireland; Grant agreement: CF-2017-0826-P, Irish Research Council postgraduate scholarship GOIPG/2018/82 and the NUI Galway College of Science. peer-reviewed 2021-11-20

Solid-state nuclear magnetic resonance (NMR) spectroscopy is an atomic-level method to determine the chemical structure, 3D structure and dynamics of solids and semi-solids. This Primer summarizes the basic principles of NMR spectroscopy as applied to the wide range of solid systems. The nuclear spin interactions and the effects of magnetic fields and radiofrequency pulses on nuclear spins in solid-state NMR are the same as in liquid-state NMR spectroscopy. However, because of the orientation dependence of the nuclear spin interactions in the solid state, the majority of high-resolution solid-state NMR spectra are measured under magic-angle spinning (MAS), which has profound effects on the types of radiofrequency pulse sequences required to extract structural and dynamical information. We describe the most common MAS NMR experiments and data analysis approaches for investigating biological macromolecules, organic materials and inorganic solids. Continuing development of sensitivity-enhancement NMR approaches, including H-1-detected fast MAS experiments, dynamic nuclear polarization and experiments in ultra-high magnetic fields, is described. We highlight recent applications of solid-state NMR spectroscopy to biological and materials chemistry. The Primer ends with a discussion of current limitations as well as areas of development of solid-state NMR spectroscopy and points to emerging areas of applications of this sophisticated spectroscopy., This Primer on solid-state nuclear magnetic resonance spectroscopy summarizes the most common experiments and data analysis approaches used to determine the structure and dynamics of solids and semi-solids as applied to biology, chemistry and materials sciences.

Amplification of chromosomal region 8p11–12 is a common genetic alteration that has been implicated in the aetiology of lung squamous cell carcinoma (LUSC)1–3. The FGFR1 gene is the main candidate driver of tumorigenesis within this region4. However, clinical trials evaluating FGFR1 inhibition as a targeted therapy have been unsuccessful5. Here we identify the histone H3 lysine 36 (H3K36) methyltransferase NSD3, the gene for which is located in the 8p11–12 amplicon, as a key regulator of LUSC tumorigenesis. In contrast to other 8p11–12 candidate LUSC drivers, increased expression of NSD3 correlated strongly with its gene amplification. Ablation of NSD3, but not of FGFR1, attenuated tumour growth and extended survival in a mouse model of LUSC. We identify an LUSC-associated variant NSD3(T1232A) that shows increased catalytic activity for dimethylation of H3K36 (H3K36me2) in vitro and in vivo. Structural dynamic analyses revealed that the T1232A substitution elicited localized mobility changes throughout the catalytic domain of NSD3 to relieve auto-inhibition and to increase accessibility of the H3 substrate. Expression of NSD3(T1232A) in vivo accelerated tumorigenesis and decreased overall survival in mouse models of LUSC. Pathological generation of H3K36me2 by NSD3(T1232A) reprograms the chromatin landscape to promote oncogenic gene expression signatures. Furthermore, NSD3, in a manner dependent on its catalytic activity, promoted transformation in human tracheobronchial cells and growth of xenografted human LUSC cell lines with amplification of 8p11–12. Depletion of NSD3 in patient-derived xenografts from primary LUSCs containing NSD3 amplification or the NSD3(T1232A)-encoding variant attenuated neoplastic growth in mice. Finally, NSD3-regulated LUSC-derived xenografts were hypersensitive to bromodomain inhibition. Thus, our work identifies NSD3 as a principal 8p11–12 amplicon-associated oncogenic driver in LUSC, and suggests that NSD3-dependency renders LUSC therapeutically vulnerable to bromodomain inhibition. The histone H3K36 methyltransferase NSD3, which is associated with the common 8p11–12 chromosomal amplification, is an oncogenic driver in lung squamous cell carcinoma.

With a 40‐year history of use for in vivo studies, the terminology used to describe the methodology and results of magnetic resonance spectroscopy (MRS) has grown substantially and is not consistent in many aspects. Given the platform offered by this special issue on advanced MRS methodology, the authors decided to describe many of the implicated terms, to pinpoint differences in their meanings and to suggest specific uses or definitions. This work covers terms used to describe all aspects of MRS, starting from the description of the MR signal and its theoretical basis to acquisition methods, processing and to quantification procedures, as well as terms involved in describing results, for example, those used with regard to aspects of quality, reproducibility or indications of error. The descriptions of the meanings of such terms emerge from the descriptions of the basic concepts involved in MRS methods and examinations. This paper also includes specific suggestions for future use of terms where multiple conventions have emerged or coexisted in the past., This work defines terms and explains concepts used to describe all aspects of MR spectroscopy, starting from the definition of the MR signal and its theoretical basis to acquisition methods, processing and quantification procedures, as well as terms involved in describing results, including quality aspects, reproducibility or indications of error. Also featured are specific suggestions for future use of terms where multiple conventions have emerged or previously coexisted.

PurposeA novel highly accurate method for MR thermometry, effective at high field, is introduced and validated, which corrects for slow and fast field fluctuations by means of reference images. MethodsAn asymmetric spin-echo echo planar imaging sequence was made frequency-selective to water or a reference substance by controlling the slice-select gradient polarity and the duration of the excitation and refocusing radiofrequency pulses. Images were acquired pairwise, and the temperature-sensitive water images were corrected for field fluctuations using the reference images. In a phantom radiofrequency heating experiment, dissolved dimethyl sulfoxide was used as a reference substance. Temperature stability was tested in vivo on the human brain, referenced using subcutaneous scalp fat. Water and fat phase images were acquired only 50 ms apart. Bloch simulations validated the frequency selection accuracy. ResultsAsymmetric spin-echo imaging using a simple frequency selection method provides highly accurate referenced MR thermometry in phantoms and in vivo at 7 T. Effects of field fluctuations caused by field drift, breathing, and heart beat were corrected. The technique is highly robust against B-1 inhomogeneities. ConclusionFrequency selection using gradient-reversal can enable fast accurate referenced in vivo MR thermometry, assisting thermal characterization of radiofrequency coils and possibly in vivo SAR monitoring. Magn Reson Med 71:524-533, 2014.

MRI was recognized for its potential use as a noninvasive in vivo thermometer 30 years ago. Today, the most popular application of MR thermometry is the guidance of thermal therapies for the treatment of cancer and other pathologies. These minimally invasive operations are routinely performed on patients who are not eligible for surgery in approximately 40 medical centers globally. The aim is to deliver or abduct thermal energy in order to cause local tissue necrosis or to sensitize a lesion to chemotherapy or radiotherapy without causing harm to the surrounding healthy tissue. Here we explain the principles of operation of MR thermometry and provide a critical review of the proposed methods, highlighting remaining fundamental and technical issues as well as recent progress. Emphasis is placed on hardware advances (RF receivers) for improved signal-to-noise ratio (SNR) which would lead to better accuracy, spatiotemporal resolution, and precise calibration. We conclude with a general outlook for the field.

Fatal neurodegenerative disorders termed transmissible spongiform encephalopathies (TSEs) are associated with the accumulation of fibrils of misfolded prion protein PrP. The noble gas xenon accommodates into four transiently enlarged hydrophobic cavities located in the well-folded core of human PrP(23-230) as detected by [(1)H, (15)N]-HSQC spectroscopy. In thermal equilibrium a fifth xenon binding site is formed transiently by amino acids A120 to L125 of the presumably disordered N-terminal domain and by amino acids K185 to T193 of the well-folded domain. Xenon bound PrP was modelled by restraint molecular dynamics. The individual microscopic and macroscopic dissociation constants could be derived by fitting the data to a model including a dynamic opening and closing of the cavities. As observed earlier by high pressure NMR spectroscopy xenon binding influences also other amino acids all over the N-terminal domain including residues of the AGAAAAGA motif indicating a structural coupling between the N-terminal domain and the core domain. This is in agreement with spin labelling experiments at positions 93 or 107 that show a transient interaction between the N-terminus and the start of helix 2 and the end of helix 3 of the core domain similar to that observed earlier by Zn(2+)-binding to the octarepeat motif.

As previously demonstrated by Thurber and Tycko, the peak position of Br-79 in potassium bromide (KBr) allows one to determine the temperature of a spinning sample. We propose to adapt the original design by using a compact KBr tablet placed at the bottom of the magic angle spinning rotor, separated from the sample under investigation by a thin disk made of polytetrafluoroethylene (or 'Teflon'(R)). This design allows spinning the sample up to at least 16 kHz. The KBr tablet can remain in the rotor when changing the sample under investigation. Calibration in the range of 98 < T < 320 K has been carried out in a static rotor by inserting a platinum thermometer. The accuracy is better than +/- 0.9 K, even in the presence of microwave irradiation. Irradiation with 5W microwaves at 263 GHz leads to a small temperature increase of 3.6 +/- 1.4 K in either static or spinning samples. The dynamic nuclear polarization enhancement decreases with increasing temperature, in particular when a frozen glassy sample undergoes a glass transition. Copyright (C) 2011 John Wiley & Sons, Ltd.

The zinc-finger protein is targeted for computational redesign as a hydrolase enzyme. Successful in having zinc activated for hydrolase function, the study validates the stepwise approach to having the protein tuned in main-chain structure stereochemically and over side chains chemically. A leucine homopolypeptide, harboring histidines to tri coordinate zinc and D-amino-acid-nucleated alpha-helix and beta-hairpin building blocks of an alpha beta beta protein, is taken up for modeling, first with CYANA, in a mixed-chirality linker between the building blocks, and then with IDeAS, in a sequence over side chains. The designed mixed-chirality polypeptide structure is proven to order as an intended alpha beta beta fold and capture zinc to activate its role as a hydrolase catalyst. The design approach to have protein folds defined stereochemically and receptor and catalysis functions defined chemically is presented, and illustrates L-and D-alpha-amino-acid structures as the alphabet integrating chemical-and stereochemical-structure variables as its letters.

International audience; The histone-like HU protein is the major nucleoid-associated protein involved in the dynamics and structure of the bacterial chromosome. Under physiological conditions, the three possible dimeric forms of the E. coli HU protein (EcHU alpha(2), EcHU beta(2), and EcHU alpha beta) are in thermal equilibrium between two dimeric conformations (N-2 a dagger" I-2) varying in their secondary structure content. High-temperature molecular dynamics simulations combined with NMR experiments provide information about structural and dynamics features at the atomic level for the N-2 to I-2 thermal transition of the EcHU beta(2) homodimer. On the basis of these data, a realistic 3D model is proposed for the major I-2 conformation of EcHU beta(2). This model is in agreement with previous experimental data.

Contains fulltext : 51201.pdf (Publisher’s version ) (Closed access) The yfhJ gene is part of the isc operon, which encodes the machinery devoted to assemble iron-sulfur clusters in prokaryotes. Its transcript is a small acidic protein that binds the desulfurase IscS, which is essential in iron-specific metabolic pathways. To understand its cellular role, we have characterized the structure of YfhJ in solution and its interactions with potential cellular partners. It contains a modified winged helix motif, usually present in DNA binding proteins, and is able to bind iron cations. The IscS interaction surface is the same as that involved in iron binding. This observation and the pattern of conservation through species strongly suggest that YfhJ is a molecular adaptor that is able to modulate the function of IscS in iron-sulfur cluster formation. The remarkable similarity between the in vitro behavior of YfhJ and that of the protein frataxin also suggests new hypotheses regarding the functional role of both proteins.

Seven prototypical microporous titanosilicates have been studied by multinuclear solid-state NMR (SSNMR) spectroscopy, representing four typical Ti environments: square-pyramidal TiO5 units (natisite, AM-1, ETS-4), edge-shared brookite-type TiO6 chains (AM-4), cubane-type Ti4O16 clusters (sitinakite, GTS-1), and corner-shared TiO6 chains (ETS-10, ETS-4). Ti-47/49 SSNMR spectra at 21.1 T are related to the coordination, crystal symmetry, and local environment of Ti. Distortions in TiO bond lengths and OTiO coordination angles are reflected via C-Q(Ti-47/49) values that range from 8 to 16 MHz. Several titanosilicates feature axially symmetric Ti-47/49 electric field gradient (EFG) tensors that permit facile spectral assignment and detection of deviations in local symmetry. This study uses Si-29 NMR experiments to assess phase purity and crystallinity. Na-23 NMR is used to probe the location and mobility of the sodium ions in the framework. The potential of K-39 SSNMR for investigation of extra-framework counter cations is demonstrated by ETS-10, with increased spectral resolution and enhanced sensitivity to changes in local environment versus Na-23 experiments. Plane-wave DFT calculations predicted Ti-47/49 NMR parameters assisting in spectral assignments and help correlate Na-23 and Si-29 NMR resonances to crystallographic sites. The approach described in this work should promote further SSNMR investigations of microporous solids, such as titanosilicates, with unknown or poorly defined structures.

The acid properties of a dehydrated borosilicate, HAMS-1B (H-[B]-ZSM-5), including the acid types, strengths, location, and quantities are investigated by means of trialkylphosphine oxides through multinuclear ID/2D MAS NMR experiments. B-11 DQF-STMAS combined with H-1 MAS NMR studies revealed B-OH and distinct Si-OH protons associated with trigonal boron. P-31 NMR spectra of TMPO-treated HAMS-1B reveal three Bronsted and three Lewis acid sites. We have found a number of limitations applying the TMPO/TBPO method to identify internal/external acidity. Therefore, we propose a new approach to unambiguously discriminate external/internal acid sites by treating a pore-free and pore-blocked HAMS-1B zeolite. This method provided unique structural insight regarding the identification of boron species/coordinations associated with Bronsted/Lewis acid sites. Additionally, ICP analysis in tandem with solid-state NMR enabled full assignment of the detected internal/external acid species and the study of their acid strength. Moreover, we identify the nature of TMPO complexes arising from Bronsted/Lewis interactions. (C) 2014 Elsevier Inc. All rights reserved.

A method for in vivo carbon-edited detection with proton echo-planar spectroscopic imaging (ICED PEPSI) is described. This method is composed of an echo-planar based acquisition implemented with C-13-H-1 J editing spectroscopy and is intended for high temporal and spatial resolution in vivo spectroscopic imaging of C-13 turnover, from D-[1,6-C-13]glucose to glutamate and glutamine, in the brain. At a static magnetic field strength of 7 T, both in vitro and in vivo chemical shift imaging data are presented with a spatial resolution of 8 mu L (i.e., 1.25 x 1.25 x 5.00 mm(3)) and a maximum spectral bandwidth of 5.2 ppm in H-1. Chemical shift imaging data acquired every 11 minutes allowed detection of regional [4-(CH2)-C-13]glutamate turnover in rat brain. The [4-(CH2)-C-13]glutamate turnover curves, which can be converted to tricarboxylic acid cycle fluxes, showed that the tricarboxylic acid cycle flux (V-TCA) in pure gray and white matter can range from 1.2 +/- 0.2 to 0.5 +/- 0.1 mu mol/g/min, respectively, for morphine-anesthetized rats. The mean cortical V-TCA from 32 voxels of 1.0 +/- 0.3 mu mol/g/min (N = 3) is in excellent agreement with previous localized measurements that have demonstrated that V-TCA can range from 0.9-1.1 mu mol/g/min under identical anesthetized conditions. (C) 1999 Wiley-Liss, Inc.

A method for heteronuclear decoupling in fast magic-angle spinning NMR measurements comprises application of a decoupling RF-pulse sequence with a decoupling-field amplitude ν 1 I on spins of a first nucleus and of an excitation pulse on spins of a second nucleus, the sequence comprising m blocks of pulses, with m≧4, each block comprising an N-fold repetition of a pair of pulses with pulse width τ p and phases whereby τ p is equal for all pulses, whereby the phase of the pulse pair of the (i+1)-th block is inverted with respect to the pulse pair of the i-th block, with i=1 . . . m−1 and i is an odd number, whereby the pulses within each pair are phase inverted, whereby a phase shift is carried out after each j-th block, with j is an even number. The efficiency of the inventive method compares favourably with CW, TPPM, SPINAL and XiX decoupling methods at medium and high RF amplitudes, particularly under rotary resonance conditions.

Two peptide fragments, corresponding to the amino acid residues 106–126 (PrP[Ac-106–126-NH 2]) and 106–114 (PrP[Ac-106–114-NH 2]) of the human prion protein have been synthesised in the acetylated and amide form at their N- and C-termini, respectively. The conformational preferences of PrP[Ac-106–126-NH 2] and PrP[Ac-106–114-NH 2] were investigated using CD and NMR spectroscopy. CD results showed that PrP[Ac-106–126-NH 2] mainly adopts an α-helical conformation in TFE–water mixture and in SDS micelles, while a predominantly random structure is observed in aqueous solution. The shorter PrP[Ac-106–114-NH 2] fragment showed similar propensities when investigated under the same experimental conditions as those employed for PrP[Ac-106–126-NH 2]. From CD experiments at different SDS concentrations, an α-helix/β-sheet conformational transition was only observed in the blocked PrP[Ac-106–126-NH 2] sequence. The NMR analysis confirmed the helical nature of PrP[Ac-106–126-NH 2] in the presence of SDS micelles. The shorter PrP[Ac-106–114-NH 2] manifested a similar behaviour. The results as a whole suggest that both hydrophobic effects and electrostatic interactions play a significant role in the formation and stabilisation of ordered secondary structures in PrP[Ac-106–126-NH 2].

Prolactin-releasing peptides (PrRPs) are two novel bioactive peptides of 20 and 31 residues, dubbed respectively PrRP20 and PrRP31, isolated from bovine hypothalamic tissues as ligands of the orphan seven-transmembrane domain receptor Hgr3. The first biological activity identified for these peptides was the release of prolactin. Recent data on biological activities of PrRPs as well as on the localization of their receptors in numerous central nervous system sites suggested new potential actions of PrRPs in the regulation of the central nervous system and the possibility of identifying an alternative central role for these peptides. We describe here the synthesis and the structural characterization of the peptide PrRP20 by CD and NMR spectroscopies. A 3D model was built on the basis of the NMR data collected in a water/sodium dodecyl sulfate mixture. This system provides an amphipatic medium able to mimic the cell membrane. The main structural feature of the PrRP20 is an alpha-helical secondary structure spanning the 10 C-terminal residues. The conformational properties of PrRP20 are discussed in considering the sequence similarity observed between the Hgr3 and the neuropeptide Y (NPY) receptors. This similarity, together with the data showing a number of biological activities common to PrRP and NPY peptides, leads us to formulate the hypothesis that similar structural elements could exist in the ligands as well. In fact, PrRP20 and NPY are well aligned in the C-terminal portion, where they share an amphipatic alpha-helical secondary structure. Interestingly, the homology between the two sequences involves residues crucial for NPY biological activity. The conformational characterization of PrRP20 and the comparison with NPY are a valuable starting point for the rational design of subsequent SAR studies aimed at identifying PrRP analogues acting as either agonists or antagonists at the Hgr3 receptor. Such PrRP analogues could be useful receptorial tools able to clarify the multiple biological functions hypothesized for the PrRP receptor in the central nervous system.

The results of extended MO calculations on formamide using the density functional theory (DFT) approximation are reported. The performance of four recent density functionals (BLYP, B3LYP, B3P86 and B3PW91) was compared with the ab initio Hartree-Fock (HF) and post-HF methods with inclusion of electron correlation at the MP2 level. With the basis sets of 6-31G*, or better quality, the B3P86 and B3PW91 DFT calculated C-N, C=O bond lengths and C=O harmonic stretching vibrations nu (C=O) were predicted to be in good agreement with available experimental and/or theoretical data. The agreement between the DFT predicted dipole moment and the experiment was significantly better than the corresponding MP2 results. The non-planar amide unit was predicted at the MP2 level for basis sets including only polarization, and both polarization and diffuse functions. The GIAO NMR shieldings were calculated for experimental and theoretical geometries of formamide. The sensitivity of Formamide nu (C=O) and GIAO NMR shieldings towards structural distortions of the C=O bond length and OCNH dihedral angle, method of calculation, basis set size and quality was studied, too. (C) 2000 Elsevier Science B.V. All rights reserved. Journal of Molecular Structure-Theochem

A method for in vivo carbon-edited detection with proton echo-planar spectroscopic imaging (ICED PEPSI) is described. This method is composed of an echo-planar based acquisition implemented with C-13-H-1 J editing spectroscopy and is intended for high temporal and spatial resolution in vivo spectroscopic imaging of C-13 turnover, from D-[1,6-C-13]glucose to glutamate and glutamine, in the brain. At a static magnetic field strength of 7 T, both in vitro and in vivo chemical shift imaging data are presented with a spatial resolution of 8 mu L (i.e., 1.25 x 1.25 x 5.00 mm(3)) and a maximum spectral bandwidth of 5.2 ppm in H-1. Chemical shift imaging data acquired every 11 minutes allowed detection of regional [4-(CH2)-C-13]glutamate turnover in rat brain. The [4-(CH2)-C-13]glutamate turnover curves, which can be converted to tricarboxylic acid cycle fluxes, showed that the tricarboxylic acid cycle flux (V-TCA) in pure gray and white matter can range from 1.2 +/- 0.2 to 0.5 +/- 0.1 mu mol/g/min, respectively, for morphine-anesthetized rats. The mean cortical V-TCA from 32 voxels of 1.0 +/- 0.3 mu mol/g/min (N = 3) is in excellent agreement with previous localized measurements that have demonstrated that V-TCA can range from 0.9-1.1 mu mol/g/min under identical anesthetized conditions. (C) 1999 Wiley-Liss, Inc.

PurposeA novel highly accurate method for MR thermometry, effective at high field, is introduced and validated, which corrects for slow and fast field fluctuations by means of reference images. MethodsAn asymmetric spin-echo echo planar imaging sequence was made frequency-selective to water or a reference substance by controlling the slice-select gradient polarity and the duration of the excitation and refocusing radiofrequency pulses. Images were acquired pairwise, and the temperature-sensitive water images were corrected for field fluctuations using the reference images. In a phantom radiofrequency heating experiment, dissolved dimethyl sulfoxide was used as a reference substance. Temperature stability was tested in vivo on the human brain, referenced using subcutaneous scalp fat. Water and fat phase images were acquired only 50 ms apart. Bloch simulations validated the frequency selection accuracy. ResultsAsymmetric spin-echo imaging using a simple frequency selection method provides highly accurate referenced MR thermometry in phantoms and in vivo at 7 T. Effects of field fluctuations caused by field drift, breathing, and heart beat were corrected. The technique is highly robust against B-1 inhomogeneities. ConclusionFrequency selection using gradient-reversal can enable fast accurate referenced in vivo MR thermometry, assisting thermal characterization of radiofrequency coils and possibly in vivo SAR monitoring. Magn Reson Med 71:524-533, 2014.

The resolving power of solid-state nuclear magnetic resonance (NMR) crystallography depends heavily on the accuracy of computational predictions of NMR chemical shieldings of candidate structures, which are usually taken to be local minima in the potential energy. To test the limits of this approximation, we systematically study the importance of finite-temperature and quantum nuclear fluctuations for $^1$H, $^{13}$C, and $^{15}$N shieldings in polymorphs of three paradigmatic molecular crystals -- benzene, glycine, and succinic acid. The effect of quantum fluctuations is comparable to the typical errors of shielding predictions for static nuclei with respect to experiments, and their inclusion to improve the agreement with measurements, translating to more reliable assignment of the NMR spectra to the correct candidate structure. The use of integrated machine-learning models, trained on first-principles energies and shieldings, renders rigorous sampling of nuclear fluctuations affordable, setting a new standard for the calculations underlying NMR structure determinations.

We report dynamic nuclear polarization (DNP)-enhanced magic-angle spinning (MAS) NMR spectroscopy in viral capsids from HIV-1 and bacteriophage AP205. Viruses regulate their life cycles and infectivity through modulation of their structures and dynamics. While static structures of capsids from several viruses are now accessible with near-atomic-level resolution, atomic-level understanding of functionally important motions in assembled capsids is lacking. We observed up to 64-fold signal enhancements by DNP, which permitted in-depth analysis of these assemblies. For the HIV-1 CA assemblies, a remarkably high spectral resolution in the 3D and 2D heteronuclear data sets permitted the assignment of a significant fraction of backbone and side-chain resonances. Using an integrated DNP MAS NMR and molecular dynamics (MD) simulation approach, the conformational space sampled by the assembled capsid at cryogenic temperatures was mapped. Qualitatively, a remarkable agreement was observed for the experimental C-13/N-15 chemical shift distributions and those calculated from substructures along the MD trajectory. Residues that are mobile at physiological temperatures are frozen out in multiple conformers at cryogenic conditions, resulting in broad experimental and calculated chemical shift distributions. Overall, our results suggest that DNP MAS NMR measurements in combination with MD simulations facilitate a thorough understanding of the dynamic signatures of viral capsids.