Identification of amino acids metabolomic profiling in human plasma distinguishes lupus nephritis from systemic lupus erythematosus.

Lupus nephritis (LN) is an immunoinflammatory glomerulonephritis associated with renal involvement in systemic lupus erythematosus (SLE). Given the close relationship between plasma amino acids (AAs) and renal function, this study aimed to elucidate the plasma AA profiles in LN patients and identify key AAs and diagnostic patterns that distinguish LN patients from those with SLE and healthy controls. Participants were categorized into three groups: normal controls (NC), SLE, and LN. Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was employed to quantify AA levels in human plasma. Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were utilized to identify key AAs. The diagnostic capacity of the models was assessed using receiver operating characteristic (ROC) curve analysis and area under the ROC curve (AUC) values. Significant alterations in plasma AA profiles were observed in LN patients compared to the SLE and NC groups. The OPLS-DA model effectively separated LN patients from the SLE and NC groups. A joint model using histidine (His), lysine (Lys), and tryptophan (Trp) demonstrated exceptional diagnostic performance, achieving an AUC of 1.0 with 100% sensitivity, specificity, and accuracy in predicting LN. Another joint model comprising arginine (Arg), valine (Val), and Trp also exhibited robust predictive performance, with an AUC of 0.998, sensitivity of 93.80%, specificity of 100%, and accuracy of 95.78% in distinguishing between SLE and LN. The joint forecasting models showed excellent predictive capabilities in identifying LN and categorizing lupus disease status. This approach provides a novel perspective for the early identification, prevention, treatment, and management of LN based on variations in plasma AA levels.

Echo feedback mediates noise-induced vocal modifications in flying bats.

Diverse animal taxa are capable of rapidly modifying vocalizations to mitigate interference from environmental noise. Echolocating bats, for example, must frequently perform sonar tasks in the presence of interfering sounds. Numerous studies have documented sound production flexibility in echolocating bats; however, it remains unknown whether noise-induced vocal modifications (NIVMs) mitigate interference effects on echoes or calls. In this study, we leverage echo level compensation behavior of echolocating bats to answer this question. Using a microphone array, we recorded echolocation calls of Hipposideros pratti trained to approach and land on a perch in the laboratory under quiet and noise conditions. We found that H. pratti exhibited echo level compensation behavior during approaching flights, which depended critically on distance to the landing perch. Broadcast noise delayed and affected the rate of echo level compensation in H. pratti. Moreover, H. pratti increased vocalization amplitude, i.e., exhibited the Lombard effect, while also adjusting call duration and bandwidth with increasing noise levels. Quantitative analyses of the data show that H. pratti relies on echo feedback, not vocal feedback, to adjust signals in the presence of noise. These findings provide compelling evidence that NIVMs in echolocating animals and non-echolocating animals operate through different mechanisms.

Cu-MOF derived CuO@g-C3N4 nanozyme for cascade catalytic colorimetric sensing.

The use of peroxidase mimics has great potential for various real applications due to their strong catalytic activity. Herein, a facile strategy was proposed to directly prepare CuO@g-C3N4 by Cu-MOF derivatization and demonstrated its efficacy in constructing a multiple enzymatic cascade system by loading protein enzymes onto it. The resulting CuO@g-C3N4 possessed high peroxidase-like activity, with a Michaelis constant (Km) of 0.25 and 0.16 mM for H2O2 and 3,3',5,5'-tetramethylbenzidine (TMB), respectively. Additionally, the high surface area of CuO@g-C3N4 facilitated the loading of protein enzymes and maintained their activity over an extended period, expanding the potential applications of CuO@g-C3N4. To test its feasibility, CuO@g-C3N4/protein oxidase complex was prepared and used to sense the ripeness and freshness of fruits and meat, respectively. The mechanism relied on the fact that the ripeness of fruits increased and freshness of food decreased with the release of marked targets, such as glucose and xanthine, which could produce H2O2 when digested by the corresponding oxidase. The peroxidase mimics of CuO@g-C3N4 could then sensitively colorimetric detect H2O2 in present of TMB. The obtained CuO@g-C3N4/oxidase complex exhibited an excellent linear response to glucose or xanthine in the range of 1.0-120 µmol/L or 8.0-350 µmol/L, respectively. Furthermore, accurate quantification of glucose and xanthine in real samples is achieved with spiked recoveries ranging from 80.2% to 120.0% and from 94.2% to 112.0%, respectively. Overall, this work demonstrates the potential of CuO@g-C3N4 in various practical applications, such as food freshness detection.

The Magic of Linking Rings: Discovery of a Unique Photoinduced Fluorescent Protein Crosslink.

Fluorosubstituted tryptophans serve as valuable probes for fluorescence and nuclear magnetic resonance (NMR) studies of proteins. Here, we describe an unusual photoreactivity introduced by replacing the single tryptophan in cyclophilin A with 7-fluoro-tryptophan. UV exposure at 282 nm defluorinates 7-fluoro-tryptophan and crosslinks it to a nearby phenylalanine, generating a bright fluorophore. The crosslink-containing fluorescent protein possesses a large quantum yield of ∼0.40 with a fluorescence lifetime of 2.38 ns. The chemical nature of the crosslink and the three-dimensional protein structure were determined by mass spectrometry and NMR spectroscopy. To the best of our knowledge, this is the first report of a Phe-Trp crosslink in a protein. Our finding may break new ground for developing novel fluorescence probes and for devising new strategies to exploit aromatic crosslinks in proteins.

Atomic-Resolution Structure of SARS-CoV-2 Nucleocapsid Protein N-Terminal Domain.

The nucleocapsid (N) protein is one of the four structural proteins of the SARS-CoV-2 virus and plays a crucial role in viral genome organization and, hence, replication and pathogenicity. The N-terminal domain (NNTD) binds to the genomic RNA and thus comprises a potential target for inhibitor and vaccine development. We determined the atomic-resolution structure of crystalline NNTD by integrating solid-state magic angle spinning (MAS) NMR and X-ray diffraction. Our combined approach provides atomic details of protein packing interfaces as well as information about flexible regions as the N- and C-termini and the functionally important RNA binding, ß-hairpin loop. In addition, ultrafast (100 kHz) MAS 1H-detected experiments permitted the assignment of side-chain proton chemical shifts not available by other means. The present structure offers guidance for designing therapeutic interventions against the SARS-CoV-2 infection.

Non-diabetic urine glucose in idiopathic membranous nephropathy.

This study aims to analyze the characteristics of idiopathic membranous nephropathy (iMN) with nondiabetic urine glucose during the follow-up. We retrospectively analyzed the data of 1313 patients who were diagnosed iMN. The prevalence of nondiabetic urine glucose during follow-up was 10.89%. There were significant differences between the patients with nondiabetic urine glucose and those without urine glucose in gender, hypertension ratio, proteinuria, N-acetyl-ß-glucosaminidase, retinol binding protein, serum albumin, serum creatinine (Scr), cholesterol, triglyceride and positive anti-phospholipase A2 receptor antibody ratio, glomerular sclerosis ratio, acute and chronic tubular injury lesion at baseline. To exclude the influence of the baseline proteinuria and Scr, case control sampling of urine glucose negative patients was applied according to gender, baseline proteinuria and Scr. The proteinuria nonremission (NR) ratio was 45.83 versus 12.50% of the urine glucose positive group and case control group. Partial remission (PR) ratio of the two groups was 36.46 versus 23.96% and complete remission (CR) ratio was 19.79% versus 63.54%, respectively. Patients with urine glucose had higher risk of 50% estimated glomerular filtration rate (eGFR) reduction. Cox regression showed that urine glucose and baseline Scr were risk factors of 50% reduction of eGFR. Urine glucose remission ratio of the patients with proteinuria NR, PR, and CR was 13.33, 56.25, and 94.73% (p < 0.005). Patients who got urine glucose remission also had better renal survival. In conclusion, non-diabetic urine glucose was closely related to proteinuria. It could be applied as a tubular injury marker to predict renal function.

Visualizing Proteins in Mammalian Cells by 19 F NMR Spectroscopy.

In-cell NMR spectroscopy is a powerful tool to investigate protein behavior in physiologically relevant environments. Although proven valuable for disordered proteins, we show that in commonly used 1 H-15 N HSQC spectra of globular proteins, interactions with cellular components often broaden resonances beyond detection. This contrasts 19 F spectra in mammalian cells, in which signals are readily observed. Using several proteins, we demonstrate that surface charges and interaction with cellular binding partners modulate linewidths and resonance frequencies. Importantly, we establish that 19 F paramagnetic relaxation enhancements using stable, rigid Ln(III) chelate pendants, attached via non-reducible thioether bonds, provide an effective means to obtain accurate distances for assessing protein conformations in the cellular milieu.

Does public fear that bats spread COVID-19 jeopardize bat conservation?

With >1 400 species, bats comprise the second-largest order of mammals and provide critical ecological services as insect consumers, pollinators, and seed dispersers. Yet, bats are frequently associated with infectious human diseases such as SARS, MERS, and Ebola. As early as the end of January 2020, several virological studies have suggested bats as a probable origin for SARS-CoV-2, the causative agent of COVID-19. How does the public view the role of bats in COVID-19? Here we report pilot data collected shortly after the outbreak of COVID-19 using two online surveys, combined with a conservation intervention experiment, primarily on people who are receiving or have received higher education in China. We found that 84% of the participants of an online survey (n = 13 589) have misunderstood the relationship between bats and COVID-19, which strengthened negative attitudes towards bats. Knowledge of bats, gender, and education level of the participants affected their attitudes towards bats. Participants who indicated a better knowledge of bats had a more positive attitude towards bats. The proportion of female participants who had negative attitudes towards bats was higher than that of male participants. Participants with a higher education level indicated a more positive attitude towards bats after the outbreak of COVID-19. A specially prepared bat conservation lecture improved peoples' knowledge of bats and the positive attitudes, but failed to correct the misconception that bats transmit SARS-CoV-2 to humans directly. We suggest that the way virologists frame the association of bats with diseases, the countless frequently inaccurate media coverages, and the natural perceptual bias of bats carrying and transmitting diseases to humans contributed to the misunderstandings. This probably led to a rise in the events of evicting bats from dwellings and structures by humans and the legislative proposal for culling disease-relevant wildlife in China. A better understanding of the relationship between disease, wildlife and human health could help guide the public and policymakers in an improved program for bat conservation.

Accurate Backbone 13 C and 15 N Chemical Shift Tensors in Galectin-3 Determined by MAS NMR and QM/MM: Details of Structure and Environment Matter.

Chemical shift tensors obtained from solid-state NMR spectroscopy are very sensitive reporters of structure and dynamics in proteins. While accurate 13 C and 15 N chemical shift tensors are accessible by magic angle spinning (MAS) NMR, their quantum mechanical calculations remain challenging, particularly for 15 N atoms. Here we compare experimentally determined backbone 13 Cα and 15 NH chemical shift tensors by MAS NMR with hybrid quantum mechanics/molecular mechanics/molecular dynamics (MD-QM/MM) calculations for the carbohydrate-binding domain of galectin-3. Excellent agreement between experimental and computed 15 NH chemical shift anisotropy values was obtained using the Amber ff15ipq force field when solvent dynamics was taken into account in the calculation. Our results establish important benchmark conditions for improving the accuracy of chemical shift calculations in proteins and may aid in the validation of protein structure models derived by MAS NMR.

Echolocating bats exhibit differential amplitude compensation for noise interference at a sub-call level.

Flexible vocal production control enables sound communication in both favorable and unfavorable conditions. The Lombard effect, which describes a rise in call amplitude with increasing ambient noise, is a widely exploited strategy by vertebrates to cope with interfering noise. In humans, the Lombard effect influences the lexical stress through differential amplitude modulation at a sub-call syllable level, which so far has not been documented in animals. Here, we bridge this knowledge gap with two species of Hipposideros bats, which produce echolocation calls consisting of two functionally well-defined units: the constant-frequency (CF) and frequency-modulated (FM) components. We show that ambient noise induced a strong, but differential, Lombard effect in the CF and FM components of the echolocation calls. We further report that the differential amplitude compensation occurred only in the spectrally overlapping noise conditions, suggesting a functional role in releasing masking. Lastly, we show that both species of bats exhibited a robust Lombard effect in the spectrally non-overlapping noise conditions, which contrasts sharply with the existing evidence. Our data highlight echolocating bats as a potential mammalian model for understanding vocal production control.

Development of an indirect ELISA for detecting porcine deltacoronavirus IgA antibodies.

Porcine deltacoronavirus (PDCoV) is a novel coronavirus that can cause vomiting and watery diarrhea in pigs and death in piglets. Since PDCoV was first detected in 2009 in Hong Kong, the prevalence of PDCoV has increased in recent years, resulting in serious economic losses to the swine industry. The coronavirus spike (S) protein is an antigen that has been demonstrated to contain epitopes that induce neutralizing antibodies. The presence of serum and milk IgA antibodies against pathogens that replicate primarily on mucosal surfaces is important for mucosal immunity. Here, an indirect anti-PDCoV IgA antibody enzyme-linked immunosorbent assay (PDCoV S1 IgA ELISA) using the purified S1 portion of S protein as the coating antigen was developed to detect PDCoV IgA antibodies in serum and sow's milk. A receiver operating characteristic (ROC) curve analysis showed high specificity and sensitivity of the PDCoV-S1-IgA-ELISA based on samples confirmed by IFA. Anti-PDCoV IgA antibodies in 152 serum samples and 65 milk samples collected from six farms that had experienced diarrhea outbreaks within previous last two years were detected by this assay, and 62.5% of the serum samples and 100% of the milk samples were positive for PDCoV. The indirect ELISA method established in this study will provide a convenient tool for measurement of serum and milk IgA levels against PDCoV in pig herds, rapid detection of PDCoV infection in pigs, and evaluation of the immunogenicity of vaccines.

Patients without records and records without patients: review of patient records in primary care and implications for surveillance of antibiotic prescribing in rural China.

BACKGROUND: We need to monitor patterns of antibiotic prescribing in order to develop and evaluate antibiotic stewardship interventions in rural China. As part of a multidisciplinary study of antibiotic use in Anhui Province we assessed the validity of electronic records (e-records) as a source of surveillance data. METHODS: One township healthcare centre and one village clinic were selected in each of three different counties. Patients with symptoms of Upper Respiratory Tract Infection (URTI), exacerbation of Chronic Obstructive Pulmonary Disease (COPD) or Urinary Tract Infection (UTI) were recruited consecutively. Researchers observed and documented clinic consultations and interviewed each of the study participants. E-records were compared to clinic observations and patient interviews. RESULTS: A total of 1030 patients were observed in clinic. Antibiotics were prescribed in 917 (89%) of consultations. E-records were created only for individuals with health insurance, with considerable between-site variation in completeness (0 to 98.7% of clinic consultations) and in the timing of documentation (within-consultation up to weeks afterwards). E-record accuracy was better in relation to antibiotics (82.8% of e-records accurately recorded what was prescribed in clinic) than for diagnosis and symptoms (45.0 and 1.1% accuracy). Only 31 participants (3.0%) presented with UTI symptoms. CONCLUSIONS: We have confirmed very high rates of outpatient antibiotic prescribing in rural Anhui province. E-records could provide useful information to inform stewardship interventions, however they may be inaccurate and/or biased. Public Health authorities should focus on improving technical infrastructure and record-keeping culture in outpatient settings. Further research is needed into community treatment of UTIs.

19F Dynamic Nuclear Polarization at Fast Magic Angle Spinning for NMR of HIV-1 Capsid Protein Assemblies.

We report remarkably high, up to 100-fold, signal enhancements in 19F dynamic nuclear polarization (DNP) magic angle spinning (MAS) spectra at 14.1 T on HIV-1 capsid protein (CA) assemblies. These enhancements correspond to absolute sensitivity ratios of 12-29 and are of similar magnitude to those seen for 1H signals in the same samples. At MAS frequencies above 20 kHz, it was possible to record 2D 19F-13C HETCOR spectra, which contain long-range intra- and intermolecular correlations. Such correlations provide unique distance restraints, inaccessible in conventional experiments without DNP, for protein structure determination. Furthermore, systematic quantification of the DNP enhancements as a function of biradical concentration, MAS frequency, temperature, and microwave power is reported. Our work establishes the power of DNP-enhanced 19F MAS NMR spectroscopy for structural characterization of HIV-1 CA assemblies, and this approach is anticipated to be applicable to a wide range of large biomolecular systems.

19F NMR relaxation studies of fluorosubstituted tryptophans.

We present 19F longitudinal and transverse relaxation studies for four differently fluorosubstituted L-tryptophans, which carry single F atoms in the indole ring, both in the context of the free amino acid and when located in the cyclophilin A protein. For the free 4F-, 5F-, 6F-, 7F-L-Trp, satisfactory agreement between experimentally measured and calculated relaxation rates was obtained, suggesting that the parameters used for calculating the rates for the indole frame are sufficiently accurate. We also measured and calculated relaxation rates for four differently 19F-tryptophan labeled cyclophilin A proteins, transferring the parameters from the free amino acid to the protein-bound moiety. Our results suggest that 19F relaxation data of the large and rigid indole ring in Trp are only moderately affected by protein motions and provide critical reference points for evaluating fluorine NMR relaxation in the future, especially in fluorotryptophan labeled proteins.

Detection and complete genome characteristics of Posavirus 1 from pigs in China.

Porcine stool-associated RNA virus 1 (Posavirus 1) is a novel member of picornaviruses and first identified from fecal samples of 30-day-old pigs with diarrhea in USA in 2011. To evaluate the existence of Posavirus 1 in swine herds, 118 clinical samples from diarrheal pigs and 31 fecal swabs from healthy pigs were collected and detected by reverse transcription-polymerase chain reaction (RT-PCR) using Posavirus 1-specific primers. Only five fecal samples from diarrheal pigs on two swine farms were positive for Posavirus 1. The complete genome sequences [excluding poly (A) tail] of two representative isolates SDQD-25 and HBTS-11 are determined and consist of 9840 and 9819 nucleotides in length, and encode one putative polyprotein of 3070 and 2952 amino acids, respectively. They share 90.3% homology with each other and 81.3-95.4% homologies with American Posavirus 1 isolates or strains at the nucleotide sequence level. The phylogenetic analysis based on the entire genomes of reference picornavirus strains or isolates showed SDQD-25, HBTS-11 cluster together with American Posavirus 1 isolates or strains, yet are clearly distant from the other picornaviruses. The complete genome sequences of Chinese Posavirus 1 isolates will enrich the information of Posavirus 1 sequence database and further expedite posavirus research on the genetic diversity, epidemiology, and evolution in China.

Dynamic allostery governs cyclophilin A-HIV capsid interplay.

Host factor protein Cyclophilin A (CypA) regulates HIV-1 viral infectivity through direct interactions with the viral capsid, by an unknown mechanism. CypA can either promote or inhibit viral infection, depending on host cell type and HIV-1 capsid (CA) protein sequence. We have examined the role of conformational dynamics on the nanosecond to millisecond timescale in HIV-1 CA assemblies in the escape from CypA dependence, by magic-angle spinning (MAS) NMR and molecular dynamics (MD). Through the analysis of backbone (1)H-(15)N and (1)H-(13)C dipolar tensors and peak intensities from 3D MAS NMR spectra of wild-type and the A92E and G94D CypA escape mutants, we demonstrate that assembled CA is dynamic, particularly in loop regions. The CypA loop in assembled wild-type CA from two strains exhibits unprecedented mobility on the nanosecond to microsecond timescales, and the experimental NMR dipolar order parameters are in quantitative agreement with those calculated from MD trajectories. Remarkably, the CypA loop dynamics of wild-type CA HXB2 assembly is significantly attenuated upon CypA binding, and the dynamics profiles of the A92E and G94D CypA escape mutants closely resemble that of wild-type CA assembly in complex with CypA. These results suggest that CypA loop dynamics is a determining factor in HIV-1's escape from CypA dependence.

Web-Based Just-in-Time Information and Feedback on Antibiotic Use for Village Doctors in Rural Anhui, China: Randomized Controlled Trial.

BACKGROUND: Excessive use of antibiotics is very common worldwide, especially in rural China; various measures that have been used in curbing the problem have shown only marginal effects. OBJECTIVE: The objective of this study was to test an innovative intervention that provided just-in-time information and feedback (JITIF) to village doctors on care of common infectious diseases. METHODS: The information component of JITIF consisted of a set of theory or evidence-based ingredients, including operation guideline, public commitment, and takeaway information, whereas the feedback component tells each participating doctor about his or her performance scores and percentages of antibiotic prescriptions. These ingredients were incorporated together in a synergetic way via a Web-based aid. Evaluation of JITIF adopted a randomized controlled trial design involving 24 village clinics randomized into equal control and intervention arms. Measures used included changes between baseline and endpoint (1 year after baseline) in terms of: percentages of patients with symptomatic respiratory or gastrointestinal tract infections (RTIs or GTIs) being prescribed antibiotics, delivery of essential service procedures, and patients' beliefs and knowledge about antibiotics and infection prevention. Two researchers worked as a group in collecting the data at each site clinic. One performed nonparticipative observation of the service process, while the other performed structured exit interviews about patients' beliefs and knowledge. Data analysis comprised mainly of: (1) descriptive estimations of beliefs or knowledge, practice of indicative procedures, and use of antibiotics at baseline and endpoint for intervention and control groups and (2) chi-square tests for the differences between these groups. RESULTS: A total of 1048 patients completed the evaluation, including 532 at baseline (intervention=269, control=263) and 516 at endpoint (intervention=262, control=254). Patients diagnosed with RTIs and GTIs accounted for 76.5% (407/532) and 23.5% (125/352), respectively, at baseline and 80.8% (417/532) and 19.2% (99/532) at endpoint. JITIF resulted in substantial improvement in delivery of essential service procedures (2.6%-24.8% at baseline on both arms and at endpoint on the control arm vs 88.5%-95.0% at endpoint on the intervention arm, P<.001), beliefs favoring rational antibiotics use (11.5%-39.8% at baseline on both arms and at endpoint on the control arm vs 19.8%-62.6% at endpoint on the intervention arm, P<.001) and knowledge about side effects of antibiotics (35.7% on the control arm vs 73.7% on the intervention arm, P<.001), measures for managing or preventing RTIs (39.1% vs 66.7%, P=.02), and measures for managing or preventing GTIs (46.8% vs 69.2%, P<.001). It also reduced antibiotics prescription (from 88.8%-62.3%, P<.001), and this decrease was consistent for RTIs (87.1% vs 64.3%, P<.001) and GTIs (94.7% vs 52.4%, P<.001). CONCLUSIONS: JITIF is effective in controlling antibiotics prescription at least in the short term and may provide a low-cost and sustainable solution to the widespread excessive use of antibiotics in rural China.

The relationship between demands for lung cancer screening and the constructs of health belief model: a cross-sectional survey in Hefei, China.

The aim of investigation is to explore the relationship between demands for lung cancer screening (LCS) and the constructs derived from the health belief model (HBM) in Hefei. The study collected data about socio-demographics, health beliefs in and demands for LCS during early June to later July 2015. By constructing a LCS demands HBM constructs, it calculated indices of demands for LCS (DSI) and HBM constructs, which include perceived risk (PR) and seriousness (PS) of the cancers; and perceived effectiveness (PE), benefits (PB) and difficulties (PD) of the screening. It also performed descriptive and multivariate regression analysis of the demands and the HBM constructs. The amount of 823 respondents participated and completed the survey. 6.4% of them had ever undertaken LCS, whereas 60.1% of them expressed willingness to accept the service of LCS if it is free. In multiple regression analysis which used weights in calculating the HBM construct indices, education displayed significant positive associations with DSI (p = .044), and most of HBM constructs indices (PSI, PRI, PBI, and PDI) were statistically significant with DSI (p < .05). HBM-based constructs regarding LCS have important effects on demands for the service, and may provide effective paths to cancer screening promotion.

Fast Magic-Angle Spinning 19 F†NMR Spectroscopy of HIV-1 Capsid Protein Assemblies.

19 F NMR spectroscopy is an attractive and growing area of research with broad applications in biochemistry, chemical biology, medicinal chemistry, and materials science. We have explored fast magic angle spinning (MAS) 19 F solid-state NMR spectroscopy in assemblies of HIV-1 capsid protein. Tryptophan residues with fluorine substitution at the 5-position of the indole ring were used as the reporters. The 19 F chemical shifts for the five tryptophan residues are distinct, reflecting differences in their local environment. Spin-diffusion and radio-frequency-driven-recoupling experiments were performed at MAS frequencies of 35 kHz and 40-60 kHz, respectively. Fast MAS frequencies of 40-60 kHz are essential for consistently establishing 19 F-19 F correlations, yielding interatomic distances of the order of 20 Å. Our results demonstrate the potential of fast MAS 19 F NMR spectroscopy for structural analysis in large biological assemblies.