Landscape of Infiltrating T Cells in Liver Cancer Revealed by Single-Cell Sequencing.

Systematic interrogation of tumor-infiltrating lymphocytes is key to the development of immunotherapies and the prediction of their clinical responses in cancers. Here, we perform deep single-cell RNA sequencing on 5,063 single T cells isolated from peripheral blood, tumor, and adjacent normal tissues from six hepatocellular carcinoma patients. The transcriptional profiles of these individual cells, coupled with assembled T cell receptor (TCR) sequences, enable us to identify 11 T cell subsets based on their molecular and functional properties and delineate their developmental trajectory. Specific subsets such as exhausted CD8+ T cells and Tregs are preferentially enriched and potentially clonally expanded in hepatocellular carcinoma (HCC), and we identified signature genes for each subset. One of the genes, layilin, is upregulated on activated CD8+ T cells and Tregs and represses the CD8+ T cell functions in vitro. This compendium of transcriptome data provides valuable insights and a rich resource for understanding the immune landscape in cancers.

BDE-47 Induces Immunotoxicity in RAW264.7 Macrophages through the Reactive Oxygen Species-Mediated Mitochondrial Apoptotic Pathway.

Polybrominated diphenyl ethers (PBDEs) are classic and emerging pollutants that are potentially harmful to the human immune system. Research on their immunotoxicity and mechanisms suggests that they play an important role in the resulting pernicious effects of PBDEs. 2,2',4,4'-Tetrabrominated biphenyl ether (BDE-47) is the most biotoxic PBDE congener, and, in this study, we evaluated its toxicity toward RAW264.7 cells of mouse macrophages. The results show that exposure to BDE-47 led to a significant decrease in cell viability and a prominent increase in apoptosis. A decrease in mitochondrial membrane potential (MMP) and an increase in cytochrome C release and caspase cascade activation thus demonstrate that cell apoptosis induced by BDE-47 occurs via the mitochondrial pathway. In addition, BDE-47 inhibits phagocytosis in RAW264.7 cells, changes the related immune factor index, and causes immune function damage. Furthermore, we discovered a significant increase in the level of cellular reactive oxygen species (ROS), and the regulation of genes linked to oxidative stress was also demonstrated using transcriptome sequencing. The degree of apoptosis and immune function impairment caused by BDE-47 could be reversed after treatment with the antioxidant NAC and, conversely, exacerbated by treatment with the ROS-inducer BSO. These findings indicate that oxidative damage caused by BDE-47 is a critical event that leads to mitochondrial apoptosis in RAW264.7 macrophages, ultimately resulting in the suppression of immune function.

Self-Assembly of Amphiphilic Copper Nanoclusters Driven by Cationic Surfactants.

Amphiphilicity is an excellent physicochemical property, which is yet to be explored from traditional surfactants to nanoparticles. This article shows that the amphiphilicity of copper nanoclusters (CuNCs) can be readily tuned by electrostatic interactions with cationic surfactants and cetyltrimethylammonium cations (CTA+) with counterions Br-, Cl-, and C7H8O3S-. Due to the role of surface ligands, the complexes of glutathione-capped CuNCs (GSH-CuNCs) and the surfactants exhibit good amphiphilicity, which enables them to self-assemble like a molecular amphiphile. This could significantly increase the utility of metal nanoclusters in basic and applied research. As the concentration of the surfactant changes, the aggregates change from nanoparticles to network-like structures. After the formation of supramolecular self-assemblies by hydrophobic interactions, the enhancement of fluorescence intensity was observed, which can be ascribed to the suppression of intramolecular vibrations based on aggregation-induced emission (AIE) and combined with the compactness of GSH-CuNCs in self-assemblies. Our study provides a facile way to generate solid fluorescent materials with excellent fluorescence performance, which may find applications in light-emitting diodes (LEDs).

Design, synthesis and antibreast cancer MCF-7 cells biological evaluation of heterocyclic analogs of resveratrol.

A new series of resveratrol heterocyclic analogs (4a-m) were designed and synthesized, and their inhibitiory effects on MCF-7 cells were evaluated to investigate structure-activity relationship. The effects of these analogs on human breast cancer MCF-7 cells were also determined. Results showed that MCF-7 cells could be inhibited more potently by these analogs than by resveratrol (IC50 = 80.0 µM). Among the analogs, compounds 4c, 4e, and 4k showed a significantly higher activity (IC50 = 42.7, 48.1, and 43.4 µM) than resveratrol. Furthermore, the derivatives without additional heterocyclic structure in the 4'-OH position exhibited a more potent activity than that with addition heterocyclic structure. In addition, docking simulation was performed to adequately position compound 4c in a human F1-ATPase active site to determine a probable binding model. These heterocyclic analogs could be effective candidates for the chemoprevention of human breast cancer.

Molecular design, synthesis and anticoagulant activity evaluation of fluorinated dabigatran analogues.

In the present study, a series of unreported fluorinated dabigatran analogues, which were based on the structural scaffold of dabigatran, were designed by computer-aided simulation. Fifteen fluorinated dabigatran analogues were screened and synthesized. All target compounds were characterized by (1)H NMR, (13)C NMR, (19)F NMR and HRMS. According to the preliminary screening results of inhibition ratio, eleven analogues (inhibition ratio >90%) were evaluated for antithrombin activity in vitro (IC50). The test results expressed that all the analogues showed effective inhibitory activities against thrombin. Especially, compounds 8f, 8k and 8o, with IC50 values of 1.81, 3.21 and 2.16nM, respectively, showed remarkable anticoagulant activities which were in the range of reference drug dabigatran (IC50=1.23nM). Moreover, compounds 8k and 8o were developed to investigate their anticoagulant activities in vivo. In those part, compound 8o exhibited a fairly strong inhibitory action for arteriovenous thrombosis with inhibition ratio of 84.66%, which was comparable with that of dabigatran (85.07%). Docking simulations demonstrated that these compounds could act as candidates for further development of novel anticoagulant drugs.

Molecular modeling studies, synthesis and biological evaluation of dabigatran analogues as thrombin inhibitors.

In this work, 48 thrombin inhibitors based on the structural scaffold of dabigatran were analyzed using a combination of molecular modeling techniques. We generated three-dimensional quantitative structure-activity relationship (3D-QSAR) models based on three alignments for both comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) to highlight the structural requirements for thrombin protein inhibition. In addition to the 3D-QSAR study, Topomer CoMFA model also was established with a higher leave-one-out cross-validation q(2) and a non-cross-validation r(2), which suggest that the three models have good predictive ability. The results indicated that the steric, hydrophobic and electrostatic fields play key roles in QSAR model. Furthermore, we employed molecular docking and re-docking simulation explored the binding relationship of the ligand and the receptor protein in detail. Molecular docking simulations identified several key interactions that were also indicated through 3D-QSAR analysis. On the basis of the obtained results, two compounds were designed and predicted by three models, the biological evaluation in vitro (IC50) demonstrated that these molecular models were effective for the development of novel potent thrombin inhibitors.

Identification of triazolo[4,5-b]pyrazine derivatives as hepatocyte growth factor receptor inhibitors through structure-activity relationships and molecular docking simulations.

c-MET is a receptor tyrosine kinase and potential oncological target for cancer therapy. The activities of 1,2,3-triazolo[4,5-b]pyrazine series of c-MET inhibitors were analyzed according to the three-dimensional quantitative structure-activity relationship and molecular docking methods. The results indicated that the hydrophobic and electrostatic fields play key roles in activity and QSAR model was reliable enough for activity prediction. Moreover, the docking results do validate the predicted 3D-QSAR scores, vital residues Asp1222, Asp1231, Met1160, Tyr1259 and Tyr1230 found in binding site. Four new c-MET inhibitor analogs designed in this Letter which are being currently synthesized by our laboratories.

Protective Effects of Isoliquiritigenin and Licochalcone B on the Immunotoxicity of BDE-47: Antioxidant Effects Based on the Activation of the Nrf2 Pathway and Inhibition of the NF-κB Pathway.

2,2',4,4'-Tetrabrominated biphenyl ether (BDE-47) is a polybrominated diphenyl ether (PBDE) homologue that is ubiquitous in biological samples and highly toxic to humans and other organisms. Prior research has confirmed that BDE-47 can induce oxidative damage in RAW264.7 cells, resulting in apoptosis and impaired immune function. The current study mainly focused on how Isoliquiritigenin (ISL) and Licochalcone B (LCB) might protect against BDE-47's immunotoxic effects on RAW264.7 cells. The results show that ISL and LCB could increase phagocytosis, increase the production of MHC-II, and decrease the production of inflammatory factors (TNF-α, IL-6, and IL-1ß) and co-stimulatory factors (CD40, CD80, and CD86), alleviating the immune function impairment caused by BDE-47. Secondly, both ISL and LCB could reduce the expressions of the proteins Bax and Caspase-3, promote the expression of the protein Bcl-2, and reduce the apoptotic rate, alleviating the apoptosis initiated by BDE-47. Additionally, ISL and LCB could increase the levels of antioxidant substances (SOD, CAT, and GSH) and decrease the production of reactive oxygen species (ROS), thereby counteracting the oxidative stress induced by BDE-47. Ultimately, ISL and LCB suppress the NF-κB pathway by down-regulating IKBKB and up-regulating IκB-Alpha in addition to activating the Nrf2 pathway and promoting the production of HO-1 and NQO1. To summarize, BDE-47 causes oxidative damage that can be mitigated by ISL and LCB through the activation of the Nrf2 pathway and inhibition of the NF-κB pathway, which in turn prevents immune function impairment and apoptosis. These findings enrich the current understanding of the toxicological molecular mechanism of BDE-47 and the detoxification mechanism of licorice.

Preparation and characterization of kelp polysaccharide and its research on anti-influenza a virus activity.

The beneficial effects of kelp polysaccharide (KPS) have recently attracted attention. In this study, KPS was extracted from kelp using the enzyme hydrolysis combined with freeze-drying, namely, KPS-EF. The structural characterization showed that KPS-EF was a highly sulfated macromolecule with the Mw of 764.2 kDa and the sulfate content of 23.49 %. The antiviral activity of KPS-EF in vitro was verified, and the IC50 value of KPS against the PR8 virus was 0.58 mg/mL. Intranasal administration of KPS-EF significantly inhibited death and weight loss in IAV-infected mice and alleviated virus-induced pneumonia symptoms, meanwhile, KPS-EF (10 mg/kg/day) significantly decreased the production levels of chemokines (CXCL1, RANTES) and inflammatory cytokines (IL-6, TNF-α) in lungs (p < 0.05). KPS-EF could downregulate the activity of viral neuraminidase (NA) primarily in the late stage of viral adsorption with an IC50 value of 0.29 mg/mL. This study provides a theoretical basis for the using KPS as a supplement to NA inhibitors or anti-influenza drugs.

A rapid evaluation method for the quality consistency assessment and spectrum-effect relationship study of Xiaohuoluo Pills developed based on combined spectral and chromatography technology.

To ensure the effectiveness of traditional Chinese medicine (TCM) and drive the advancement of high-quality Chinese medicine, the establishment of a scientifically sound quality evaluation system is particularly important. The objective of this study was to develop a straightforward and practical comprehensive evaluation method for quality control of Xiaohuoluo Pills (XHLP) by employing diverse fingerprint technologies. Firstly, Fourier transform infrared spectroscopy fingerprint (FT-IRFP), ultraviolet spectral fingerprint (UVFP) and fusion fingerprints based on five-wavelength matched average fusion fingerprint (FWFFP) were established for 21 samples. Secondly, the Comprehensive Quantified Ratio Fingerprinting Method (CQRFM) was used to conduct a comprehensive evaluation of the fingerprint profiles of 21 batches of samples and the results showed that all samples met the quality requirements. Then to further evaluate the samples, the External Standard Method (ESM) was employed to measure the content of three indicator components in XHLP, and this was done with the intention of enhancing the quality control system of the samples. Furthermore, antioxidant activity was also measured, and a model for analyzing the relationship between antioxidant data and fingerprint information from the three spectra was established using Orthogonal Projection to Latent Structures (OPLS), resulting in an accurate spectral efficacy relationship diagram. In conclusion, this study utilized spectral and chromatography techniques to comprehensively assess the quality of XHLP, incorporating qualitative and quantitative aspects. Additionally, a correlation between spectral profiles and efficacy was established by evaluating the antioxidant capacity of the samples. This method offers valuable insights for quality control not only of XHLP but also for other TCM.

Hidden features of NAD-RNA epitranscriptome in Drosophila life cycle.

Nicotinamide adenine dinucleotide (NAD), a nucleotide-containing metabolite, can be incorporated into the RNA 5'-terminus to result in NAD-capped RNA (NAD-RNA). Since NAD has been heightened as one of the most essential metabolites in cells, its linkage to RNA represents a critical but poorly studied modification at the epitranscriptomic level. Here, we design a highly sensitive method, DO-seq, to capture NAD-RNAs. Using Drosophila, we identify thousands of previously unexplored NAD-RNAs and their dynamics in the fly life cycle, from embryo to adult. We show the evidence that chromosomal clustering might be the structural basis by which co-expression can couple with NAD capping on physically and functionally linked genes. Furthermore, we note that NAD capping of cuticle genes inversely correlates with their gene expression. Combined, we propose NAD-RNA epitranscriptome as a hidden layer of regulation that underlies biological processes. DO-seq empowers the identification of NAD-capped RNAs, facilitating functional investigation into this modification.

Postoperative MRI Findings Following PELD and Their Correlations with Clinical Prognosis are Investigated by Injecting Contrast into Annulus Fibrosus Intraoperatively.

Objective: To validate whether a residual mass demonstrated on early postoperative MR after percutaneous endoscopic lumbar discectomy (PELD) is indeed an intraoperatively retained annulus fibrosus, and explore the correlation between imaging changes in the residual mass and clinical prognosis of patients. Methods: A prospective study of 118 patients were included. During surgery, a contrast medium, Gadopentetate Dimeglumine, was injected around the ruptured annulus fibrosus. The intensity of the T2 signal, the size of the remaining mass (SR), and the cross-sectional area of the spinal canal (SCSA), VAS, and ODI were assessed at preoperative, 1-h (7-day), 6-month, and 12-month postoperative intervals. Based on VAS at 7 days post-surgery, patients were classified into either a non-remission group (Group A, VAS > 3) or a remission group (Group B, VAS ≤ 3). Results: Six patients who developed recurrent LDH were excluded. A residual mass was detected on MRI 1 h after surgery in 94.6% (106/112). During one year of follow-up, 90.1% (101/112) of the patients displayed fibrous annulus remodeling, although 68.7% (77/112) still exhibited herniation. Significant differences were found in the ODI between Groups A and B one week after surgery (p < 0.001). However, no significant differences were observed in T2 signal intensity, SR, and SCSA at 1-h, 6-month and 12-month post-surgery (p > 0.05) between the two groups. In a multiple linear regression analysis, early postoperative ODI changes were associated with T2 signal (B = -10.22, sig < 0.05), long-term changes were associated with alterations in SR (B = 5.63, sig < 0.05) and SCSA (B = -0.13, sig < 0.05). Conclusion: The residual mass observed in early postoperative MR images after PELD was the retained annulus fibrosus intraoperatively. Short-term changes in clinical symptoms after PELD were linked to T2 signal intensity, while long-term changes were associated with changes in SR and SCSA.

A Multi-Element Identification System Based on Deep Learning for the Visual Field of Percutaneous Endoscopic Spine Surgery.

Background: Lumbar disc herniation is a common degenerative lumbar disease with an increasing incidence. Percutaneous endoscopic lumbar discectomy can treat lumbar disc herniation safely and effectively with a minimally invasive procedure. However, the learning curve of this technology is steep, which means that initial learners are often not sufficiently proficient in endoscopic operations, which can easily lead to iatrogenic damage. At present, the application of computer deep learning technology to clinical diagnosis, treatment, and surgical navigation has achieved satisfactory results. Purpose: The objective of our team is to develop a multi-element identification system for the visual field of endoscopic spine surgery using deep learning algorithms and to evaluate the feasibility of this system. Method: We established an image database by collecting surgical videos of 48 patients diagnosed with lumbar disc herniation, which was labeled by two spinal surgeons. We selected 6000 images of the visual field of percutaneous endoscopic spine surgery (including various tissue structures and surgical instruments), divided into the training data, validation data, and test data according to 2:1:2. We developed convolutional neural network models based on instance segmentation-Solov2, CondInst, Mask R-CNN and Yolact, and set the four network model backbone as ResNet101 and ResNet50 respectively. Mean average precision (mAP) and frames per second (FPS) were used to measure the performance of each model for classification, localization and recognition in real time, and AP (average) is used to evaluate how easily an element is detected by neural networks based on computer deep learning. Result: Comprehensively comparing mAP and FSP of each model for bounding box test and segmentation task for the test set of images, we found that Solov2 (ResNet101) (mAP = 73.5%, FPS = 28.9), Mask R-CNN (ResNet101) (mAP = 72.8%, FPS = 28.5) models are the most stable, with higher precision and faster image processing speed. Combining the average precision of the elements in the bounding box test and segmentation tasks in each network, the AP(average) was highest for tool 3 (bbox-0.85, segm-0.89) and lowest for tool 5 (bbox-0.63, segm-0.72) in the instrumentation, whereas in the anatomical tissue elements, the fibrosus annulus (bbox-0.68, segm-0.69) and ligamentum flavum (bbox-0.65, segm-0.62) had higher AP(average),while extra-dural fat (bbox-0.42, segm-0.44) was lowest. Conclusion: Our team has developed a multi-element identification system for the visual field of percutaneous endoscopic spine surgery adapted to the interlaminar and foraminal approaches, which can identify and track anatomical tissue (nerve, ligamentum flavum, nucleus pulposus, etc.) and surgical instruments (endoscopic forceps, an high-speed diamond burr, etc.), which can be used in the future as a virtual educational tool or applied to the intraoperative real-time assistance system for spinal endoscopic operation.

A Facile and Rapid Strategy for Quantifying PCBs in Cereals Based on Dispersive Solid-Phase Extraction and Gas Chromatography-Mass Spectrometry: A Reference for Safety Concerns in Sustainable Textiles.

Cereals and their derivative products such as starch and cyclodextrin are significant natural materials for sustainable textile processing (e.g., sizing, dispersing, etc.). However, the contamination of cereals with polychlorinated biphenyls (PCBs) is often neglected, which has led to increasing concerns due to the adverse effects on end users. Therefore, monitoring PCBs in cereals is of great importance in preventing health risks. However, high starch, protein, and fat contents make cereals a complicated matrix and can challenge the analysis of PCBs in cereals. This work describes a facile and rapid strategy for quantifying 18 PCBs in cereals that included corn, wheat, and rice through dispersive solid-phase extraction and gas chromatography with mass spectrometry. Importantly, this was the first time that carboxyl-modified, multi-walled carbon nanotubes were incorporated in the detection of PCBs in cereals. The influences of several parameters on the extraction and clean-up efficiency were investigated; these included the type and volume of extraction solvent, sonication time, and the type and dosage of the adsorbent. The matrix effects on quantification were also evaluated. This approach exhibited a better clean-up performance. All the analytes showed weak matrix effects, and thus a solvent standard plot could be prepared for their quantification. Spiking experiments in the selected matrices at three concentration levels from 0.5 to 10 µg/kg resulted in satisfactory recoveries that ranged from 79.2% to 110.5% with relative standard deviations (RSDs; n = 6) less than 10.3%. The limits of detection (LODs) and quantification (LOQs) ranged from 0.04 to 0.1 µg/kg and 0.1 to 0.4 µg/kg, respectively. The practical application of this method was investigated by analyzing actual cereal samples, which demonstrated that the proposed approach was a facile and efficient strategy for PCB determination and provided a reference for the safety evaluation of sustainable textiles. The method also could be generalized to other troublesome samples for testing of multiple PCBs.

Comprehensive Evaluation of Cancer Treatment-Related Cardiac Dysfunction by Ultrasound Myocardial Strain: A Network Meta-Analysis.

Anticancer treatment regimens are effective but may lead to cardiac dysfunction. The meaning of this statement is that myocardial strain can be a good indicator of cancer treatment-related cardiac dysfunction. We used Bayesian network meta-analysis to compare and rank these regimens to comprehensively evaluate their influence on the heart. We searched multiple databases to identify relevant studies. Global longitudinal strain (GLS), global radial strain, global circumferential strain, and other parameters were collected at baseline (T0), from baseline to 3 months of follow-up (T3), from 3 months to 6 months of follow-up (T6), and from 6 months to 12 months or longer of follow-up (T12). The weight mean differences (WMD) with 95% confidence intervals (CI) were used to express continuous variables. Direct and indirect comparison and ranking of different regimens based on the forest plots and the surface under the cumulative ranking area. A total of 4613 subjects were included in 33 studies. Anthracycline-based chemotherapy (ANT), trastuzumab, paclitaxel plus carboplatin or clofarabine, and radiotherapy (RT) were more likely to reduce GLS and global circumferential strain at T3 and T12. In particular, ANT+RT resulted in a more significant decrease in GLS than ANT alone at T12 (WMD 1.15; 95% CI, 0.05-2.26). Interestingly, cardioprotective treatment regimens, such as anthracycline plus bisoprolol plus angiotensin-converting enzyme inhibitors (ANT+BB+ACEIs) (WMD -2.79; 95% CI, -5.06 to -0.52), and ANT plus rosuvastatin (STATINs) (WMD -2.92; 95% CI, -5.54 to -0.29), were more likely to improve GLS than ANT at T12. The included anticancer regimens, especially ANT+RT, reduced GLS at T12, but their combination with cardioprotective drugs improved them. These results will help clinicians choose the best therapy regimens.

Challenges for Obstetricians and the Countermeasures of COVID-19 Epidemic.

Since the outbreak of the novel coronavirus in Wuhan, China, as obstetricians, we also face great challenges. We need to identify pregnant patients with 2019 coronavirus disease infection timely, and give them appropriate treatment in order to obtain a good maternal and infant prognosis. Here, we would like to share a case and provide some suggestions on how to screen, diagnose and treat pregnant women with 2019 coronavirus disease infection during the outbreak.

Dysregulation of the Urothelial Cancer Associated 1 Long Noncoding RNA Promotes Proliferation of Vascular Smooth Muscle Cells by Modulating Expression of P27KIP1/CDK2.

Background: Atherosclerosis is one of the leading causes of morbidity and mortality worldwide. A variety of long noncoding RNAs (lncRNAs) have been reported to be significantly involved in vascular smooth muscle cell (VSMC) proliferation, which is an essential process for atherosclerotic plaque formation. The aim of this study was to investigate the mechanism of lncRNA urothelial cancer associated 1 (UCA1) involvement in atherosclerosis. Method: The effects of oxidized low-density lipoprotein (oxLDL) and UCA1 on VSMC proliferation and colony-forming ability was measured by 3-(4,5-dimethylthiazol-2-yl) -2,5-diphenyl-2H-tetrazolium bromide (MTT) assays, real-time polymerase chain reaction (PCR), and western blots, as well as to determine the effect that oxLDL has on UCA1 expression, and the effect of oxLDL and UCA1 on the expression of cyclin-dependent kinase 2 (CDK2). Results: oxLDL treatment increased the proliferation rate of VSMCs in a concentration-dependent manner. Importantly, UCA1 apparently increased the viability of VSMCs as the VSMCs exhibited a significantly reduced growth rate when UCA1 expression was knocked down by specific small interfering RNAs (siRNAs). In conjunction with increasing cell viability, oxLDL also enhanced the colony-forming ability of VSMCs while UCA1 siRNA decreased the colony-forming ability of VSMCs. Furthermore, UCA1 significantly decreased the percentage of VSMCs in G1 phase, while increasing their percentage in S phase. In contract siRNA knockdown of UCA1 caused an increased percentage of cell in G1 phase, and a reduction in the percentage of cells in S phase. Using real-time PCR and western blot assays, we showed that oxLDL significantly increased the expression levels of UCA1 and CDK2. Furthermore, UCA1 siRNA and CDK2 siRNA almost abolished the positive effect of oxLDL on CDK2 expression. Finally, overexpression of UCA1 induced an increase in CDK2 levels, and knockdown of UCA1 caused inhibition of CDK2 expression. Conclusion: Upregulation of UCA1 enhances abnormal proliferation of VSMC by promoting G1/S transition through modulating the expression of CDK2.

The Science of Harmony: A Psychophysical Basis for Perceptual Tensions and Resolutions in Music.

This paper attempts to establish a psychophysical basis for both stationary (tension in chord sonorities) and transitional (resolution in chord progressions) harmony. Harmony studies the phenomenon of combining notes in music to produce a pleasing effect greater than the sum of its parts. Being both aesthetic and mathematical in nature, it has baffled some of the brightest minds in physics and mathematics for centuries. With stationary harmony acoustics, traditional theories explaining consonances and dissonances that have been widely accepted are centred around two schools: rational relationships (commonly credited to Pythagoras) and Helmholtz's beating frequencies. The first is more of an attribution than a psychoacoustic explanation while electrophysiological (amongst other) discrepancies with the second still remain disputed. Transitional harmony, on the other hand, is a more complex problem that has remained largely elusive to acoustic science even today. In order to address both stationary and transitional harmony, we first propose the notion of interharmonic and subharmonic modulations to address the summation of adjacent and distant sinusoids in a chord. Based on this, earlier parts of this paper then bridges the two schools and shows how they stem from a single equation. Later parts of the paper focuses on subharmonic modulations to explain aspects of harmony that interharmonic modulations cannot. Introducing the concept of stationary and transitional subharmonic tensions, we show how it can explain perceptual concepts such as tension in stationary harmony and resolution in transitional harmony, by which we also address the five fundamental questions of psychoacoustic harmony such as why the pleasing effect of harmony is greater than that of the sum of its parts. Finally, strong correlations with traditional music theory and perception statistics affirm our theory with stationary and transitional harmony.

Carboxylated Multiwalled Carbon Nanotubes as Dispersive Solid-Phase Extraction Sorbent to Determine Eighteen Polychlorinated Biphenyls in Vegetable Samples by Gas Chromatography-Mass Spectrometry.

A simple, rapid, and reliable method based on dispersive solid-phase extraction (d-SPE) and gas chromatography-mass spectrometry (GC-MS) was developed for quantitating polychlorinated biphenyls (PCBs) in vegetable samples. Parameters affecting both the extraction yields and cleanup efficiency, including the type and volume of extraction solvent, extraction time, type and volume of cleanup sorbent, and cleanup time, were optimized. Matrix effects were evaluated, and matrix-matched calibration was recommended. Under the optimized conditions, carboxylated multiwalled carbon nanotubes (MWCNTs-COOH), which exhibit excellent adsorption capabilities due to large surface area and unique structure, were employed as d-SPE sorbent to remove interfering substances, rather than the analytes, from vegetable samples. Satisfactory linear relationship was observed for all PCBs across a concentration range of 5-500 µg/kg with correlation coefficients no less than 0.9993. Four representative vegetables (cucumber, tomato, lettuce, and cabbage) were selected as matrices for method validation. Each matrix was spiked at concentrations of 5, 10, and 100 µg/kg to evaluate recoveries, which ranged from 84.5% to 116.5% with relative standard deviations (n=6) between 0.6% and 17.6%. The limits of detection and the limits of quantification ranged from 0.3 to 1.4 µg/kg and 0.8 to 4.5 µg/kg, respectively. Twelve real vegetable samples were analyzed using the proposed method. Three of the target PCBs were detected in one lettuce sample with the total concentration of 17.9 µg/kg.

Origins of the different metal preferences of Escherichia coli peptide deformylase and Bacillus thermoproteolyticus thermolysin: a comparative quantum mechanical/molecular mechanical study.

The Escherichia coli peptide deformylase (PDF) and Bacillus thermoproteolyticus thermolysin (TLN) are two representative metal-requiring peptidases having remarkably similar active centers but distinctively different metal preferences. Zinc is a competent catalytic cofactor for TLN but not for PDF. Reaction pathways and the associated energetics for both enzymes were determined using combined semiempirical and ab initio quantum mechanical/molecular mechanical modeling, without presuming reaction coordinates. The results confirmed that both enzymes catalyze via the same chemical steps, and reproduced their different preferences for zinc or iron as competent cofactors. Further analyses indicated that different feasibility of the nucleophilic attack step leads to different metal preferences of the two enzymes. In TLN, the substrate is strongly activated and can serve as the fifth coordination ligand of zinc prior to the chemical steps. In PDF, the substrate carbonyl is activated by the chemical step itself, and becomes the fifth coordination partner of zinc only in a later stage of the nucleophilic attack. These leads to a much more difficult nucleophilic attack in PDF than in TLN. Different from some earlier suggestions, zinc has no difficulty in accepting an activated substrate as the fifth ligand to switch from tetra- to penta-coordination in either PDF or TLN. When iron replaces zinc, its stronger interaction with the hydroxide ligand may lead to higher activation barrier in TLN. In PDF, the stronger interactions of iron with ligands allow iron-substrate coordination to take place either before or at a very early stage of the chemical step, leading to effective catalysis. Our calculations also show combined semiempirical and ab initio quantum mechanical modeling can be efficient approaches to explore complicated reaction pathways in enzyme systems.