Design and analysis of a complementary structure-based high selectivity tri-band frequency selective surface.

This work presents a novel tri-band bandpass frequency selective surface (FSS) that achieves high-order filtering responses in different frequency bands by means of a complementary structure. The proposed FSS is composed of three metal periodic arrays, which are separated by multilayer dielectric substrates. The gridded-double convoluted loop (G-DCL) structure, which is the middle layer structure, is a hybrid resonator that generates different resonant frequencies. The top and bottom layer structures are designed as complementary structures to the middle layer. To accurately describe the frequency responses, an equivalent circuit model (ECM) has been constructed over the entire band from 0 to 16 GHz. The results of the simulation indicate that the developed FSS can generate three pass-bands operating at 3.79 GHz, 8.34 GHz, and 12.52 GHz, respectively, and - 3 dB fractional bandwidths are 52.8%, 13.7%, and 19.7%. The transmission responses at the edges of each passband show a quick roll-off from the passband to the stopband, and there is significant out-of-band suppression between adjacent passbands. Moreover, the FSS maintains excellent angular and polarization stability within a 50° range. For verification, the tri-band FSS has been fabricated and tested. The experimental results match the simulation results, validating the accuracy of the FSS design.

Integrated optical frequency division for microwave and mmWave generation.

The generation of ultra-low-noise microwave and mmWave in miniaturized, chip-based platforms can transform communication, radar and sensing systems1-3. Optical frequency division that leverages optical references and optical frequency combs has emerged as a powerful technique to generate microwaves with superior spectral purity than any other approaches4-7. Here we demonstrate a miniaturized optical frequency division system that can potentially transfer the approach to a complementary metal-oxide-semiconductor-compatible integrated photonic platform. Phase stability is provided by a large mode volume, planar-waveguide-based optical reference coil cavity8,9 and is divided down from optical to mmWave frequency by using soliton microcombs generated in a waveguide-coupled microresonator10-12. Besides achieving record-low phase noise for integrated photonic mmWave oscillators, these devices can be heterogeneously integrated with semiconductor lasers, amplifiers and photodiodes, holding the potential of large-volume, low-cost manufacturing for fundamental and mass-market applications13.

Contribution of protein conformational heterogeneity to NMR lineshapes at cryogenic temperatures.

While low-temperature Nuclear Magnetic Resonance (NMR) holds great promise for the analysis of unstable samples and for sensitizing NMR detection, spectral broadening in frozen protein samples is a common experimental challenge. One hypothesis explaining the additional linewidth is that a variety of conformations are in rapid equilibrium at room temperature and become frozen, creating an inhomogeneous distribution at cryogenic temperatures. Here, we investigate conformational heterogeneity by measuring the backbone torsion angle (Ψ) in Escherichia coli Dihydrofolate Reductase (DHFR) at 105 K. Motivated by the particularly broad N chemical shift distribution in this and other examples, we modified an established NCCN Ψ experiment to correlate the chemical shift of Ni+1 to Ψi. With selective 15N and 13C enrichment of Ile, only the unique I60-I61 pair was expected to be detected in 13C'-15N correlation spectrum. For this unique amide, we detected three different conformation basins based on dispersed chemical shifts. Backbone torsion angles Ψ were determined for each basin: 114 ± 7° for the major peak and 150 ± 8° and 164 ± 16° for the minor peaks as contrasted with 118° for the X-ray crystal structure (and 118° to 130° for various previously reported structures). These studies support the hypothesis that inhomogeneous distributions of protein backbone torsion angles contribute to the lineshape broadening in low-temperature NMR spectra.

Predicted and Experimental NMR Chemical Shifts at Variable Temperatures: The Effect of Protein Conformational Dynamics.

NMR chemical shifts provide a sensitive probe of protein structure and dynamics but remain challenging to predict and interpret. We examine the effect of protein conformational distributions on 15N chemical shifts for dihydrofolate reductase (DHFR), comparing QM/MM predicted shifts with experimental shifts in solution as well as frozen distributions. Representative snapshots from MD trajectories exhibit variation in predicted 15N chemical shifts of up to 25 ppm. The average over the fluctuations is in significantly better agreement with room temperature solution experimental values than the prediction for any single optimal conformations. Meanwhile, solid-state NMR (SSNMR) measurements of frozen solutions at 105 K exhibit broad lines whose widths agree well with the widths of distributions of predicted shifts for samples from the trajectory. The backbone torsion angle ψi-1 varies over 60° on the picosecond time scale, compensated by φi. These fluctuations can explain much of the shift variation.

Hemodynamic characteristics and mechanism for intracranial aneurysms initiation with the circle of Willis anomaly.

Clinically, circle of Willis (CoW) is prone to anomaly and is also the predominant incidence site of intracranial aneurysms (IAs). This study aims to investigate the hemodynamic characteristics of CoW anomaly, and ascertain the mechanism of IAs initiation from the perspective of hemodynamics. Thus, the flow of IAs and pre-IAs were analyzed for one type of cerebral artery anomaly, that is, anterior cerebral artery A1 segment (ACA-A1) unilateral absence. Three patient geometrical models with IAs were selected from Emory University Open Source Data Center. IAs were virtually removed from the geometrical models to simulate the pre-IAs geometry. For calculation methods, a one-dimensional (1-D) solver and a three-dimensional (3-D) solver were combined to obtain the hemodynamic characteristics. The numerical simulation revealed that the average flow of Anterior Communicating Artery (ACoA) is almost zero when CoW is complete. In contrast, ACoA flow increases significantly in the case of ACA-A1 unilateral absence. For per-IAs geometry, the jet flow is found at the bifurcation between contralateral ACA-A1 and ACoA, which exhibits characteristics of high Wall Shear Stress (WSS) and high wall pressure in the impact region. It triggers the initiation of IAs from the perspective of hemodynamics. The vascular anomaly that leads to jet flow should be considered as a risk factor for IAs initiation.

Quantitative Evaluation of Hemodynamic Changes After Multiple Intracranial Aneurysms Occlusion Using Computational Fluid Dynamics.

OBJECTIVE: Multiple intracranial aneurysms (MIA) are prevalent. This study conducted hemodynamic calculations on MIA to analyze the effects of occlusion of the internal carotid artery (ICA) and middle cerebral artery (MCA) aneurysms on the hemodynamics of other arteries, as well as the issue of the treatment order for these aneurysms. METHODS: The models of 9 patients with MIA were selected for the study. A computational fluid dynamics model combining 1-dimension and 3-dimension was used to obtain the vascular flow pattern and wall pressure. RESULTS: There was increased pressure at the MCA and anterior cerebral artery (ACA) after occlusion of the aneurysm at the ICA. However, the pressure at the ICA has hardly changed after the aneurysm occlusion at the MCA. Occlusion of the aneurysm of different sizes at the MCA had almost no impact on the pressure at the ICA and ACA. For small aneurysm, the pressure of the ACA and MCA increases with decreasing size of the aneurysm at the ICA. After occlusion of a large aneurysm at the ICA, the impact on the pressure of the ACA and MCA is almost the same as after occlusion of a medium-sized aneurysm. CONCLUSIONS: If the treatment order of ICA and MCA aneurysms cannot be determined based on patient factors and aneurysm characteristics, the MCA aneurysm should be treated as a priority.

Ferritinophagy induced ferroptosis in the management of cancer.

BACKGROUND: Ferroptosis, a newly form of regulated cell death (RCD), is characterized by iron dyshomeostasis and unrestricted lipid peroxidation. Emerging evidence depicts a pivotal role for ferroptosis in driving some pathological processes, especially in cancer. Triggering ferroptosis can suppress tumor growth and induce an anti-tumor immune response, denoting the therapeutic promises for targeting ferroptosis in the management of cancer. As an autophagic phenomenon, ferritinophagy is critical to induce ferroptosis by degradation of ferritin to release intracellular free iron. Recently, a great deal of effort has gone into designing and developing anti-cancer strategies based on targeting ferritinophagy to induce ferroptosis. CONCLUSION: This review delineates the regulatory mechanism of ferritinophagy firstly and summarizes the role of ferritinophagy-induced ferroptosis in cancer. Moreover, the strategies targeting ferritinophagy to induce ferroptosis are highlighted to unveil the therapeutic value of ferritinophagy as a target to manage cancer. Finally, the future research directions on how to cope with the challenges in developing ferritinophagy promoters into clinical therapeutics are discussed.

Trends in prevalence and disability-adjusted life years of cataract in China from 1990 to 2019 / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To assess the evolving burden of cataracts in China from 1990 to 2019.METHODS: Data on disease burden related to cataracts in China were retrieved from the Global Burden of Disease(GBD)2019 study based on large public databases. Utilizing data from the GBD 2019 study, we extracted information on cataract-related disease burden in China from extensive public databases. Analysis of prevalence and disability-adjusted life years(DALYs)associated with cataracts in China was conducted based on GBD 2019 findings. The variable characteristics of age-standardized prevalence rates(ASPR)and age-standardized DALYs rates(ASDR)in China and its neighboring countries were also explored.RESULTS: Between 1990 and 2019, the number of prevalent cases of blindness and vision loss caused by cataracts in China increased by 223.54%, and the corresponding DALYs raised by 142.14%. Over the past 30 years, females exhibited higher age-standardized prevalence and DALYs rates compared to males. Meanwhile, individuals aged 65 to 84 years were found to be more susceptible to cataracts than other age groups. Compared with neighboring countries, China ranked from the 9th position in 1990(867.09, 95%UI: 761.36 to 975.42, per 100 000 population)to the 11th in 2019(991.56, 95%UI: 861.52 to 1131.04, per 100 000 population)in ASPR, while from the 9th in 1990(65.85, 95%UI: 46.39 to 89.41, per 100 000 population)to the 10th position in 2019(59.16, 95%UI: 41.70 to 80.15, per 100 000 population)in ASDR. However, on a global scale, China maintained relatively low ASDR and ASPR for cataracts in 2019.CONCLUSION: The study highlights a substantial rise in the prevalence and DALYs associated with blindness and vision loss due to cataracts from 1990 to 2019 in China, and underscores the urgent need for increased early screening of cataracts, particularly among the elderly and females.

Exploring the hypoglycemic mechanism of chlorogenic acids from Pyrrosia petiolosa (Christ) Ching on type 2 diabetes mellitus based on network pharmacology and transcriptomics strategy.

ETHNOPHARMACOLOGICAL RELEVANCE: Pyrrosia petiolosa (Christ) Ching (YBSW) is a Traditional Chinese medicine rich in chlorogenic acids. It is an important component in many Traditional Chinese medicinal hypoglycemic formulas and is commonly used by the Miao people to treat diabetes with good efficacy. Our previous research has suggested that chlorogenic acids may be the active ingredients in YBSW. AIM OF THE STUDY: To explore the mechanisms underlying the anti-type 2 diabetes mellitus (T2DM) hypoglycemic effects of chlorogenic acids contained in YBSW. MATERIALS AND METHODS: In vivo experiments, hematoxylin-eosin staining (HE) staining, and immunohistochemistry (IHC) were used to determine the effects of chlorogenic acids contained in YBSW in rats. mRNA expression profiling, microarray analysis, and network pharmacology were used to analyze the underlying mechanisms of the effects. Finally, apoptosis and changes in the related pathways were evaluated in vitro using a 3-(4,5-dimethyl-2-thia-zolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay, quantitative real-time polymerase chain reaction, immunofluorescence (IF) assessment, and flow cytometry. RESULTS: After the administration of isochlorogenic acid B, the levels of triglycerides, serum total cholesterol, and fasting blood glucose significantly decreased. HE and IHC staining revealed that isochlorogenic acid B significantly increased insulin expression in islet cells. Using network pharmacology and RNA-seq Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis, we screened the advanced glycation end products-receptor for advanced glycation end products (AGE-RAGE) signaling pathway. We also verified that YBSW and its chlorogenic acid can inhibit apoptosis and downregulate the expression of related mRNA in the AGE-RAGE pathway in RIN-m5f cells. CONCLUSIONS: YBSW exhibits a significant hypoglycemic effect, with chlorogenic acid being an effective component. The therapeutic effect of chlorogenic acids contained in YBSW is mainly realized by promoting insulin secretion and pancreatic tissue repair. Moreover, YBSW substantially mitigates apoptosis via the AGE-RAGE pathway in T2DM.

Efficacy and safety of tenofovir alafenamide in patients with chronic hepatitis B exhibiting suboptimal response to entecavir.

BACKGROUND: Entecavir (ETV) is a potent and safe antiviral agent for patients with chronic hepatitis B (CHB); however, some patients may exhibit suboptimal response or resistance to ETV. Tenofovir alafenamide (TAF) is a novel tenofovir prodrug with improved pharmacokinetics and reduced renal and bone toxicity compared with tenofovir disoproxil fumarate. AIM: To evaluate the efficacy and safety of switching from ETV to TAF in patients with CHB exhibiting suboptimal response to ETV. METHODS: A total of 60 patients with CHB who had been treated with ETV for at least 12 mo and had persistent or recurrent viremia [Hepatitis B virus (HBV) DNA ≥ 20 IU/mL] or partial virologic response (HBV DNA < 20 IU/mL, but detectable) were enrolled in the study. The patients were randomly assigned to either continue ETV (0.5 mg) daily or switch to TAF (25 mg) daily for 48 wk. The primary endpoint was the proportion of patients who achieved a virologic response (HBV DNA level < 20 IU/mL) at week 48. Secondary endpoints included changes in serum alanine aminotransferase (ALT), hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), and anti-HBe levels, and renal and bone safety parameters. RESULTS: At week 48, the proportion of patients who achieved a virologic response was significantly higher in the TAF group than in the ETV group (93.3% vs 66.7%, P = 0.012). The mean reduction in HBV DNA from baseline was also significantly greater in the TAF group than in the ETV group (-3.8 vs -2.4 Log10 IU/mL, P < 0.001). The rates of ALT normalization, HBeAg loss, HBeAg seroconversion, and HBsAg loss were not found to significantly differ between the two groups. None of the patients developed genotypic resistance to ETV or TAF. Both drugs were well tolerated, with no serious adverse events or discontinuations caused by adverse events. No significant changes were observed in the estimated glomerular filtration rate, serum creatinine level, or urine protein-to-creatinine ratio in either group. The TAF group had a significantly lower decrease in bone mineral density at the lumbar spine and hip than the ETV group (-0.8% vs -2.1%, P = 0.004; -0.6% vs -1.8%, P = 0.007, respectively). CONCLUSION: Switching from ETV to TAF is effective and safe for patients with CHB exhibiting a suboptimal response to ETV and may prevent further viral resistance and reduce renal and bone toxicity.

Neutrophils as potential therapeutic targets for breast cancer.

Breast cancer (BC) remains the foremost cause of cancer mortality globally, with neutrophils playing a critical role in its pathogenesis. As an essential tumor microenvironment (TME) component, neutrophils are emerging as pivotal factors in BC progression. Growing evidence has proved that neutrophils play a Janus- role in BC by polarizing into the anti-tumor (N1) or pro-tumor (N2) phenotype. Clinical trials are evaluating neutrophil-targeted therapies, including Reparixin (NCT02370238) and Tigatuzumab (NCT01307891); however, their clinical efficacy remains suboptimal. This review summarizes the evidence regarding the close relationship between neutrophils and BC, emphasizing the critical roles of neutrophils in regulating metabolic and immune pathways. Additionally, we summarize the existing therapeutic approaches that target neutrophils, highlighting the challenges, and affirming the rationale for continuing to explore neutrophils as a viable therapeutic target in BC management.

A modified multiple cross displacement amplification linked with a gold nanoparticle biosensor for the detection of Epstein-Barr virus in clinical applications.

Epstein-Barr virus (EBV), a double-stranded DNA virus belonging to the family Herpesviridae, infects more than 95% of healthy adults by attacking the host immune system. Here, a novel detection protocol, utilizing the modified multiple cross displacement amplification (MCDA) technique combined with a gold nanoparticles-based lateral flow biosensors (AuNPs-LFB), was devised and developed to detect EBV infection (termed EBV-MCDA-LFB assay). Ten MCDA primers targeting the EBNA-LP gene were designed, including CP1* primers modified with 6-carboxyfluorescein (FAM) and D1* primers modified with biotin. Then, nucleic acid templates extracted from various pathogens and whole blood samples were used to optimize and evaluate the EBV-MCDA-LFB assay. As a result, the lowest concentration of EBNA-plasmids, which can be detected by MCDA-LFB assay with an optimal reaction condition of 67°C for 30 min, was 10 copies/reaction. Here, the MCDA-LFB assay can detect all EBV pathogens used in the study, and no cross-reactions with non-EBV organisms were observed. Meanwhile, the entire detection workflow of the EBV-MCDA-LFB assay for whole blood samples, including DNA template preparation (25 min), EBV-MCDA amplification (30 min), and AuNPs-LFB-mediated validation (2-5 min), can be completed within 1 h. Taken together, the EBV-MCDA-LFB assay established in the current study is a rapid, simplified, sensitive, specific, and easy-to-obtain technique that can be used as a screening or diagnostic tool for EBV infection in clinical applications, especially in resource-poor regions.

Association of Adipokines with Alzheimer's Disease in a Chinese Cohort.

BACKGROUND: The correlation between plasma adipose factor levels and Alzheimer's patients is not entirely clear. OBJECTIVE: We aimed to investigate associations between AD and plasma levels of three adipokines including plasma adiponectin, leptin, and resistin. METHODS: A single-center, cross-sectional study recruited AD patients (n = 148) and cognitively normal (CN) controls (n = 110). The multivariate logistic regression analysis was applied to determine associations of adiponectin, leptin, and resistin with the presence of AD. The receiver operating characteristic (ROC) analysis was employed to determine the diagnostic power of adiponectin, leptin and resistin for AD. RESULTS: After adjusted for the conventional risk factors, plasma levels of leptin (OR = 0.417, 95% CI: 0.272-0.638, p < 0.0001) and adiponectin (OR = 1.249, 95% CI: 1.151-1.354, p < 0.0001) were associated with the presence of AD. In total participants, the plasma adiponectin level was negatively correlated with MMSE scores (p < 0.0001) and was positively with CDR scores (p < 0.0001) and age (p < 0.0001). The plasma level of leptin was negatively correlated with CDR scores (p < 0.0001) and positively correlated with MMSE scores (p < 0.0001). Both adiponectin (p < 0. 0001) and leptin (p < 0. 0001) featured higher AUC than the random chance. CONCLUSIONS: Plasma adiponectin and leptin were associated with the presence, symptomatic severity, and diagnostic power of AD, suggesting a potential role of adipokines in the pathogenesis of AD.

Acute stress reaction, depression anxiety stress, and job withdrawal behavior in non-frontline pediatric nurses during the pandemic: a cross-sectional study.

Backgrounds: The COVID-19 pandemic has brought an unprecedented healthy crisis to people worldwide. It is crucial to assess the psychological status of non-frontline nurses. More attention to the mental and physical health of non-frontline nurses during a public health emergency is necessary for a full understanding of the implications. Therefore, this study aims to investigate the factors that influence the acute stress reaction of non-frontline pediatric nurses during the COVID-19 pandemic. Methods: This study aimed to explore factors associated with acute stress reactions of non-frontline pediatric nurses in Hunan province during the COVID-19 pandemic. This was a cross-sectional design. Five hundred eighteen pediatric nurses from Hunan province, China, completed the Stanford Acute Stress Reaction Questionnaire (SASRQ), Depression Anxiety Stress Scales-21 (DASS-21), and Job Withdrawal Behavior Scales (JWB). Multiple linear regression analyses and Pearson's correlation were used to analyze the results. Results: The mean scores of DASS-21, JWB, SASRQ were 1.443 ± 0.500, 1.601 ± 0.544, and 1.858 ± 0.805, respectively. Stress, anxiety, depression (three sub-dimensions of DASS-21), JWB, monthly income and department were the major predictive factors for SASRQ (Adjusted R2 = 0.579, p < 0.001). Pearson's correlation showed that the mean score of SASRQ was positively correlated with JWB, DASS-21, and all its dimensions (p < 0.01). Conclusion: The study indicated that the SASRQ was greater with higher levels of DASS-21 and JWB. It revealed an acute stress reaction in non-frontline pediatric nurses and recommends more focus on the factors influencing the SASRQ.

Deep learning enables automatic adult age estimation based on CT reconstruction images of the costal cartilage.

OBJECTIVE: Adult age estimation (AAE) is a challenging task. Deep learning (DL) could be a supportive tool. This study aimed to develop DL models for AAE based on CT images and compare their performance to the manual visual scoring method. METHODS: Chest CT were reconstructed using volume rendering (VR) and maximum intensity projection (MIP) separately. Retrospective data of 2500 patients aged 20.00-69.99 years were obtained. The cohort was split into training (80%) and validation (20%) sets. Additional independent data from 200 patients were used as the test set and external validation set. Different modality DL models were developed accordingly. Comparisons were hierarchically performed by VR versus MIP, single-modality versus multi-modality, and DL versus manual method. Mean absolute error (MAE) was the primary parameter of comparison. RESULTS: A total of 2700 patients (mean age = 45.24 years ± 14.03 [SD]) were evaluated. Of single-modality models, MAEs yielded by VR were lower than MIP. Multi-modality models generally yielded lower MAEs than the optimal single-modality model. The best-performing multi-modality model obtained the lowest MAEs of 3.78 in males and 3.40 in females. On the test set, DL achieved MAEs of 3.78 in males and 3.92 in females, which were far better than the MAEs of 8.90 and 6.42 respectively, for the manual method. For the external validation, MAEs were 6.05 in males and 6.68 in females for DL, and 6.93 and 8.28 for the manual method. CONCLUSIONS: DL demonstrated better performance than the manual method in AAE based on CT reconstruction of the costal cartilage. CLINICAL RELEVANCE STATEMENT: Aging leads to diseases, functional performance deterioration, and both physical and physiological damage over time. Accurate AAE may aid in diagnosing the personalization of aging processes. KEY POINTS: • VR-based DL models outperformed MIP-based models with lower MAEs and higher R2 values. • All multi-modality DL models showed better performance than single-modality models in adult age estimation. • DL models achieved a better performance than expert assessments.

Associations Between Plasma Klotho with Renal Function and Cerebrospinal Fluid Amyloid-ß Levels in Alzheimer's Disease: The Chongqing Ageing & Dementia Study.

BACKGROUND: The kidney-brain crosstalk has been involved in Alzheimer's disease (AD) with the mechanism remaining unclear. The anti-aging factor Klotho was reported to attenuate both kidney injury and AD pathologies. OBJECTIVE: To investigate whether plasma Klotho participated in kidney-brain crosstalk in AD. METHODS: We enrolled 33 PiB-PET-positive AD patients and 33 amyloid-ß (Aß)-negative age- and sex-matched cognitively normal (CN) controls from the Chongqing Ageing & Dementia Study (CADS). The levels of plasma Klotho, Aß, and tau in the cerebrospinal fluid (CSF) were measured by enzyme-linked immunosorbent assay. RESULTS: We found higher plasma Klotho and lower estimated glomerular filtration rate (eGFR) levels in AD patients compared with CN. The eGFR was positively associated with Aß42, Aß40 levels in CSF and negatively associated with CSF T-tau levels. Plasma Klotho levels were both negatively correlated with CSF Aß42 and eGFR. Mediation analysis showed that plasma Klotho mediated 24.96% of the association between eGFR and CSF Aß42. CONCLUSION: Renal function impacts brain Aß metabolism via the kidney-brain crosstalk, in which the plasma Klotho may be involved as a mediator. Targeting Klotho to regulate the kidney-brain crosstalk provides potential therapeutic approaches for AD.

Multi-component immune knockout: A strategy for studying the effective components of traditional Chinese medicine.

Periploca forrestii Schltr., a traditional Chinese medicine (TCM), is commonly used to treat autoimmune diseases such as rheumatoid arthritis (RA). However, its mechanism, involving a variety of cardiac glycosides, remains largely unknown. The immune knockout strategy can highly selectively deplete target components by immunoaffinity chromatography (IAC). We aimed to identify the common structural features of cardiac glycosides in P. forrestii and design IAC to specifically recognize these features to achieve the multi-component knockout of potential active substances from the extracts of P. forrestii. A content detection experiment confirmed that the content of a compound with periplogenin structure (CPS) in the extract of P. forrestii was reduced by 45% by IAC of periplogenin. The immunosuppressive ability of the extract on H9 human T lymphocytic cells was weakened after CPS knockout from P. forrestii extract. Molecular biology experiments showed that mRNA expression of interferon-γ (IFN-γ), interleukin-2 (IL-2), and interleukin-6 (IL-6) in H9 cells was up-regulated after CPS knockout, while no significant changes in the expression of interleukin-4 (IL-4) were found. CPS knockout from P. forrestii extract did not cause significant changes in the proliferation of lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells incubated with this extract. These results indicate that CPS exhibited immunosuppressive effects via inhibiting the T helper 1 (Th1) cell immune response and not via the anti-inflammatory components in P. forrestii. This is the first use of IAC to achieve multi-component knockout in TCM extracts for identifying effective compounds. This method is effective and reliable and warrants further exploration.

Predicted and Experimental NMR Chemical Shifts at Variable Temperatures: The Effect of Protein Conformational Dynamics.

NMR chemical shifts provide a sensitive probe of protein structure and dynamics. Prediction of shifts, and therefore interpretation of shifts, particularly for the frequently measured amidic 15 N sites, remains a tall challenge. We demonstrate that protein 15 N chemical shift prediction from QM/MM predictions can be improved if conformational variation is included via MD sampling, focusing on the antibiotic target, E. coli Dihydrofolate reductase (DHFR). Variations of up to 25 ppm in predicted 15 N chemical shifts are observed over the trajectory. For solution shifts the average of fluctuations on the low picosecond timescale results in a superior prediction to a single optimal conformation. For low temperature solid state measurements, the histogram of predicted shifts for locally minimized snapshots with specific solvent arrangements sampled from the trajectory explains the heterogeneous linewidths; in other words, the conformations and associated solvent are 'frozen out' at low temperatures and result in inhomogeneously broadened NMR peaks. We identified conformational degrees of freedom that contribute to chemical shift variation. Backbone torsion angles show high amplitude fluctuations during the trajectory on the low picosecond timescale. For a number of residues, including I60, ψ varies by up to 60º within a conformational basin during the MD simulations, despite the fact that I60 (and other sites studied) are in a secondary structure element and remain well folded during the trajectory. Fluctuations in ψ appear to be compensated by other degrees of freedom in the protein, including φ of the succeeding residue, resulting in "rocking" of the amide plane with changes in hydrogen bonding interactions. Good agreement for both room temperature and low temperature NMR spectra provides strong support for the specific approach to conformational averaging of computed chemical shifts.

Contribution of protein conformational heterogeneity to NMR lineshapes at cryogenic temperatures.

While low temperature NMR holds great promise for the analysis of unstable samples and for sensitizing NMR detection, spectral broadening in frozen protein samples is a common experimental challenge. One hypothesis explaining the additional linewidth is that a variety of conformations are in rapid equilibrium at room temperature and become frozen, creating an inhomogeneous distribution at cryogenic temperatures. Here we investigate conformational heterogeneity by measuring the backbone torsion angle (Ψ) in E. coli DHFR at 105K. Motivated by the particularly broad N chemical shift distribution in this and other examples, we modified an established NCCN Ψ experiment to correlate the chemical shift of N i+1 to Ψ i . With selective 15 N and 13 C enrichment of Ile, only the unique I60-I61 pair was expected to be detected in 13 C'- 15 N correlation spectrum. For this unique amide we detected three different conformation basins based on dispersed chemical shifts. Backbone torsion angles Ψ were determined for each basin 114 ± 7 for the major peak, and 150 ± 8 and 164 ± 16° for the minor peak as contrasted with 118 for the X-ray crystal structure (and 118-130 for various previously reported structures). These studies support the hypothesis that inhomogeneous distributions of protein backbone torsion angles contribute to the lineshape broadening in low temperature NMR spectra. Significance Statement: Understanding protein conformational flexibility is essential for insights into the molecular basis of protein function and the thermodynamics of proteins. Here we investigate the ensemble of protein backbone conformations in a frozen protein freezing, which is likely a close representation for the ensemble in rapid equilibrium at room temperature. Various conformers are spectrally resolved due to the exquisite sensitivity of NMR shifts to local conformations, and NMR methods allow us to directly probe the torsion angles corresponding to each band of chemical shifts.