Near-edge x-ray absorption fine structure spectra and specific dissociation of small peptoid molecules

In this study, the total ion yield near-edge x-ray absorption fine structure spectra of four similar peptoid molecules, which differ in the numbers and positions of methyl groups, were investigated experimentally and theoretically. At each excitation energy, the intensity and branching ratio of each ionic product were measured. At a few resonant excitation energies, a specific dissociation of the C-CO bond at the nitrogen and oxygen K-edges and of the N-CO bond at the carbon K-edge was dominant, which correlated well with the predicted destination antibonding orbitals of the core electron excitation. These specific dissociation mechanisms of small peptoid molecules could provide insights into similar phenomena that occur in peptide molecules.

Water Plays Multifunctional Roles in the Intervening Formation of Secondary Organic Aerosols in Ozonolysis of Limonene: A Valence Photoelectron Spectroscopy and Density Functional Theory Study

Although water may affect aqueous aerosol chemistry, how it intervenes in the formation of secondary organic aerosols (SOAs) at the molecular level remains elusive. Ozonolysis of limonene is one of the most important sources of indoor SOAs. Here, we report the valence electronic properties of limonene aerosols and SOAs derived from limonene ozonolysis (Lim-SOAs) via aerosol vacuum ultraviolet photoelectron spectroscopy, with a focus on the effects of water on Lim-SOAs. The first vertical ionization energy of limonene aerosols is measured to be 8.79 ± 0.07 eV. While water significantly increases the total photoelectron yield of Lim-SOAs, three photoelectron features attributable to Lim-SOAs each exhibit distinct dependence on the fraction of water in aerosols, implying that different formation pathways and molecular origins are involved in the formation of Lim-SOAs. Combined with density functional theory calculation and mass spectrometry measurements, this study reveals that water, particularly the water dimer, enhances the formation of Lim-SOAs by altering the ozonolysis energetics and pathways by intervening in its Criegee chemistry, acting as both a catalyst and a reactant. The atmospheric implication is discussed.

ROS induced the Rab26 promoter hypermethylation to promote cigarette smoking-induced airway epithelial inflammation of COPD through activation of MAPK signaling

Cigarette smoking (CS) exposure-induced airway inflammatory responses drive the occurrence and development of emphysema and chronic obstructive pulmonary disease (COPD). However, its precise mechanisms have not been fully elucidated. In this study, we explore the role of Rab26 in CS exposure modulating the inflammatory response of airway epithelium and the novel mechanism of CS exposure regulation Rab26. These data showed that CS exposure and H₂O₂ (a type of ROS) suppressed the expression of Rab26 and increased the expression of DNMT3b in vivo and in vitro. GEO data analysis found the level of Rab26 was decreased in the lung tissue of COPD patients. CSE-induced ROS promoted DNA methylation of the Rab26 promoter and inhibited its promoter activity by elevating the DNMT3b level. Antioxidants N-Acetyl-l-cysteine (NAC), 5-Aza-2'-deoxycytidine (5-AZA) (DNA methylation inhibitor) and DNMT3B siRNA alleviated CSE's inhibitory effect on Rab26 expression in vitro. Importantly, NAC alleviated the improved expression of Rab26 and reduced DNMT3B expression, in the airway of smoking exposure as well as attenuated the inflammatory response in vivo. Overexpression of Rab26 attenuated CSE-induced production of inflammatory mediators through part inactivation of p38 and JNK MAPK. On the contrary, silencing Rab26 enhanced p38 and JNK activation and aggravated inflammatory response. These findings suggest that ROS-mediated Rab26 promoter hypermethylation is a critical step in cigarette smoking-induced airway epithelial inflammatory response. Restoring Rab26 in the airway epithelium might be a potential strategy for treating airway inflammation and COPD.

[Establishment of contralateral arteriovenous fistula by using the waste vein on the side of central venous lesion: a case report]

Central venous lesion is a difficult problem in the vascular access complications of hemodialysis, which can cause serious clinical symptoms and affect the quality of hemodialysis and life of patients. We established arteriovenous fistula of the contralateral graft blood vessel with the used vein on the diseased side of the central vein of the patient. The arteriovenous fistula of the graft blood vessel was successfully punctured and hemodialysis was performed 2 weeks later. In this way, we not only solved the problem of venous hypertension and subsequent vascular access in the patient, but also reserved more vascular resources.

Vitrectomy with residual internal limiting membrane covering and autologous blood for a secondary macular hole: A case report

BACKGROUND

Myopic foveoschisis (MF) is a common complication of pathological myopia. A macular hole (MH) usually results from the natural progression of MF and is a common complication of vitrectomy. Vitrectomy combined with residual internal limiting membrane (ILM) covering and autologous blood was effective for closing a secondary MH.

CASE SUMMARY

A 52-year-old woman presented to our clinic with a complaint of blurred vision in the right eye for 7 years. Her best corrected visual acuity (BCVA) was 20/100, axial length was 25.79 mm and standard equivalent refractive error was -10.5 dioptres. Preoperative optical coherence tomography revealed foveoschisis in the right eye. Vitrectomy with fovea-sparing ILM peeling was performed. An MH developed and gradually expanded 5 mo after the initial vitrectomy. Vitrectomy with residual ILM covering and autologous blood was performed. The MH closed 3 wk after the second vitrectomy.

CONCLUSION

Fovea-sparing ILM peeling can provide residual ILM for the treatment of MH secondary to vitrectomy for MF. Vitrectomy combined with residual ILM covering and autologous blood is effective for closing secondary MH and improving BCVA.

Protective effects of progesterone on pulmonary artery smooth muscle cells stimulated with Interleukin 6 via blocking the shuttling and transcriptional function of STAT3

BACKGROUND

Sex hormone paradox is a crucial but unresolved issue in the field of pulmonary artery hypertension (PAH), and is thought to be related to different pathogenic factors. Inflammation is one of pathological mechanisms of PAH development. However, effects of sex hormones on the pulmonary vasculature under the condition of inflammation are still elusive.

METHODS

Interleukin-6 (IL-6) was used as a representative inflammatory stimulator. Effects of 17β-estradiol or progesterone on human pulmonary artery smooth muscle cells (PASMCs) were measured under the condition of IL-6. Cell functions of proliferation and migration were measured by Alarmar Blue, EdU assay, wound-healing assay and transwell chambers. We explored further mechanisms using western blot, immunofluorescence, co-immunoprecipitation, qPCR and chromatin immunoprecipitation.

RESULTS

Our results revealed that IL-6 promoted the proliferation of PASMCs, but progesterone could reverse the adverse effect of IL-6. The protective effect was dependent on progesterone receptor (PGR). By interacting with signal transducer and activator of transcription 3 (STAT3), activated PGR could reduce the IL-6-induced nuclear translocation of STAT3 and prevent STAT3-chromatin binding in PASMCs, leading to the decreased transcription of downstream CCND1 and BCL2. Alternatively, progesterone slightly decreased the phosphorylation of pro-proliferative Erk1/2 and Akt kinases and upregulated the anti-proliferative pSmad1-Id1/2 axis in IL-6-incubated PASMCs.

CONCLUSIONS

Progesterone played a protective role on PASMCs in the context of IL-6, by blocking the functions of STAT3. Our findings might assist in explaining the clinical phenomenon of better prognosis for women with PAH.

Comparative effectiveness and tolerability of targeted agents combined with chemotherapy in patients with HER2-positive gastroesophageal cancer: A network meta-analysis

BACKGROUND

Gastric cancer (GC) or gastroesophageal junction (GEJ) cancer with HER2 overexpression is highly invasive, with a poor prognosis. With the development of new targeted agents, which agents have ideal therapeutic effects must be determined. This network meta-analysis analyzed the effectiveness and tolerability of targeted agents combined with chemotherapy in HER2-positive GC/GEJ cancer.

METHODS

Public databases were searched from the date of inception to October 22, 2020. Randomized controlled trials (RCTs) on targeted agent-related regimens for HER2-positive advanced GC or GEJ cancer were included. Subgroup analyses based on publication language, first-line treatment, second/third-line treatment, and HER2 staining intensity were performed.

RESULTS

In total, 13 articles were included. The trastuzumabderuxtecan (TraD) and pertuzumab plus trastuzumab and chemotherapy (PerTraChemo) regimens were considered to have high effectiveness but low tolerability. In the subgroup analysis, PerTraChemo still had high effectiveness with low tolerability as the first-line therapy. As the second- or third-line therapy, TraD and lapatinib plus chemotherapy (LapChemo) had high effectiveness and moderate tolerability. In terms of overall survival (OS) time, PerTraChemo had a relative advantage in the immunohistochemistry (IHC) 2+/in situ hybridization (ISH)+ population, whereas TraD, PerTraChemo, and trastuzumab plus chemotherapy (TraChemo) had a relative advantage in the IHC3+ population.

CONCLUSION

TraD had relative advantages as the second- or third-line therapy and in the IHC3 + population. PerTraChemo is a potential first-line therapy, but it requires further confirmation because the JACOB phase III clinical trial failed to confirm the superiority of PerTraChemo over TraChemo with regard to OS.

Serum cartilage oligomeric matrix protein is decreased in patients with pulmonary hypertension: a potential protective factor

Cartilage oligomeric matrix protein (COMP) was a protective factor in the cardiovascular system. Previous studies showed that hypoxia led to decreased COMP in rat models of pulmonary hypertension. However, the expression pattern of COMP in the pulmonary hypertension population was unclear. A total of 35 patients newly diagnosed with pulmonary hypertension and 70 controls were enrolled in the study. Circulating COMP concentrations of serum samples were measured by enzyme-linked immunosorbent assay and were analyzed the association with multiple clinical variables. Serum COMP concentrations in the pulmonary hypertension group were significantly declined in comparison with age- and sex-matched normal controls, especially in the female subgroup. No significant difference of COMP concentrations was observed in the etiological classification, heart function classification, and risk stratification. Major hemodynamic parameters, six-minute walk distance, N-terminal pro brain natriuretic peptide, and short-term prognosis were not statistically associated with COMP. However, some echocardiography parameters, like tricuspid annular plane systolic excursion and mean right atrial pressure, were found the negative relation to COMP concentrations. In conclusion, serum COMP levels were decreased in the patients with pulmonary hypertension, which was in accordance with its known biological effects. Its association with long-term prognosis was worth further exploring.

Noble Gas in a Ring

We have designed a new type of molecule with a noble gas (Ng = Kr and Xe) atom in a six-membered ring. Their structures and stability have been studied by density functional theory and by correlated electronic structure calculations. The results showed that the six-membered ring is planar with very short Ng–O and Ng–N polar covalent bonds. The calculated energy barriers for all the unimolecular dissociation pathways are higher than 20 and 35 kcal/mol for Ng = Kr and Xe, respectively. The current study suggests that these molecules and their derivatives might be synthesized and observable at cryogenic conditions.

Respiratory Aspergillus Colonization Was Associated With Relapse of Acute Exacerbation in Patients With Chronic Obstructive Pulmonary Disease: Analysis of Data From A Retrospective Cohort Study

Background: Patients with chronic obstructive pulmonary disease (COPD) are more susceptible to Aspergillus colonization or infection. Several studies have demonstrated that invasive pulmonary Aspergillosis (IPA) and Aspergillus hypersensitivity (AH) have a detrimental effect on COPD. However, it remains to be clarified whether Aspergillus colonization is associated with acute exacerbation of COPD (AECOPD). This study aimed to explore the impact of Aspergillus colonization in the lower respiratory tract on AECOPD.

Method: Patients with Aspergillus colonization were identified from a retrospective cohort of hospitalized AECOPD from 2011 to 2016 in eight centers in Shanghai, China. The demographic information, conditions of the stable stage, clinical characteristics during hospitalization, and 1-year follow-up information after discharge were collected and compared to participants without fungi colonization.

Result: Twenty-six hospitalized AECOPD patients with Aspergillus colonization and 72 controls were included in the final analysis after excluding patients with other fungi isolation and matching. The rates of recurrence of acute exacerbation within 90 days and 180 days after discharge in the patients with Aspergillus colonization were both significantly higher than that in the fungi negative patients (90 days: 19.2 vs. 4.2%, p = 0.029; 180 days: 23.1 vs. 4.2%, p = 0.010), and the all-cause mortality within 1 year was also higher (11.5 vs. 0.0%, p = 0.017). Multivariate logistic regression analysis showed that Aspergillus colonization was an independent risk factor for the recurrence of acute exacerbation within 90 days and 180 days (90 days: OR = 8.661, 95% CI: 1.496-50.159, p = 0.016; 180 days: OR =10.723, 95% CI: 1.936-59.394, p = 0.007).

Conclusion:Aspergillus colonization may predict poor prognosis of AECOPD while leading to an increased risk of recurrent AECOPD in a short period.

[Distribution of Nitrogen and Phosphorus in Lake Chaohu Sediments and Pollution Evaluation]

We investigated the spatial distribution and storage of nitrogen and phosphorus in Lake Chaohu sediments and evaluated the sediment nitrogen and phosphorus pollution index. Results show that the average total nitrogen (TN) and total phosphorus (TP) content in the surface-layer sediments of Lake Chaohu were 1088 mg·kg^-1 and 585 mg·kg^-1, respectively, and 666 mg·kg^-1 and 509 mg·kg^-1 in the bottom-layer sediments, respectively. TN content in the surface layer was significantly higher than in the bottom layer (P<0.01). Spatially, TN, TP, and sediment thickness were ranked in the order western lake area > eastern lake area > middle lake area, and the TN and TP contents were significantly different in the surface sediments from the middle and eastern areas of the lake (P<0.05, P<0.01). TN and TP storage in the lake sediments was 1.58×10⁵ t and 0.98×10⁵ t, respectively. TN and TP were significantly correlated in both the western and middle parts of the lake (P<0.01). In addition, TN was significantly correlated with sediment thickness in middle area of the lake, which indicated that TN may have the same pollution sources as TP and both were affected by sediment thickness. TN pollution index (S_TN), TP pollution index (S_TP), and comprehensive pollution index (FF) values were 1.09, 1.39, and 1.32, respectively, indicating light-to-moderate levels of pollution. Specifically, the western lake surface sediments were heavily polluted with respect to TP, the eastern lake surface sediments were moderately polluted, and the middle lake surface sediments were slightly polluted. Nutrient pollution varied widely between different areas of the lake, with sediments in the western part of the lake presenting a higher safety risk. Overall, these observations indicate that Lake Chaohu is threatened by internal nutrient loading.

Theoretical Prediction on the New Types of Noble Gas Containing Anions OBONgO- and OCNNgO- (Ng = He, Ar, Kr and Xe)

The fluorine-less noble gas containing anions OBONgO⁻ and OCNNgO⁻ have been studied by correlated electronic structure calculation and density functional theory. The obtained energetics indicates that for Ng=Kr and Xe, these anions should be kinetically stable at low temperature. The molecular structures and electron density distribution suggests that these anions are stabilized by ion-induced dipole interactions with charges concentrated on the electronegative OBO and OCN groups. The current study shows that in addition to the fluoride ion, polyatomic groups with strong electronic affinities can also form stable noble gas containing anions of the type Y⁻…NgO.

Predictors of acute cardiovascular events following acute exacerbation period for patients with COPD: a nested case-control study

Background

It has been noted that there is an increase in the incidence of acute cardiovascular events (CVEs) in patients with chronic obstructive pulmonary disease (COPD) during an acute exacerbation (AE), thereby causing increased inpatient mortality. Thus, we have tried to identify predictors of acute CVEs in patients with AECOPD via a nested case–control study.

Methods

A total of 496 cases hospitalized for AECOPD were included in this study, and followed-up for up to 6 months after discharge. Acute CVEs in the AE period were defined as a new or worsening acute coronary syndrome (ACS), arrhythmia, or left ventricular disfunction (LVD). Predictors of CVEs were selected from several variables, including baseline characteristics and treatments in the stable period as well as symptoms, laboratory tests, complications and treatments in the AE period.

Results

Thirty cases (6.05%) had acute CVEs, namely 2 had ACS, 13 had LVD and 19 experienced some form of arrhythmia. Four deaths were observed in the CVE group, with significantly increased death risk compared with the non-CVE group (P = 0.001, OR = 5.81). Moreover, patients who had CVEs were more prone to have re-exacerbation within 3 months. Multivariate analysis showed that previous LVD history (P = 0.004, OR = 5.06), 20% increase in heart rate (HR) (P = 0.003, OR = 10.19), electrolyte disturbance (P = 0.01, OR = 4.24) and diuretics (P = 0.002, OR = 6.37) were independent predictors of CVEs. In addition, usage of theophylline, fluoroquinolone and inhaled beta agonists in the AE period were not statistically associated with acute CVEs.

Conclusions

Our preliminary study indicates that patients hospitalized for AECOPD with previous LVD history or increased HR need close observation and diuretics should be cautiously used with regular electrolyte monitoring. These findings need to be confirmed in a large cohort.

Prevention of Acute Exacerbation in Subjects with Moderate-to-very Severe COPD by Modulating Lower Respiratory Microbiome: Protocol of a Prospective, Multicenter, Randomized Controlled Trial

Background

COPD is a global respiratory disease that has produced a worldwide health care burden. Acute exacerbation of COPD (AECOPD) is the leading cause of death in patients with COPD and accounts for the majority of expenditure of COPD management. The colonization of potential pathogenic bacteria in the lower respiratory tract is an important cause of the acute exacerbation especially in patients with moderate and severe COPD. Some clinical studies have shown the potential of oral probiotics, aerosol-inhaled amikacin and combined vaccination to prevent AECOPD.

Methods and Analysis

We hypothesize that patients with stable COPD will benefit from aerosol-inhaled amikacin, oral probiotics or combined vaccination in terms of preventing acute exacerbation of COPD, slowing the progression of the disease and improving their quality of life. The trial aimsto investigate the efficacy and safety of the above interventions to decolonize bacteria in the lower respiratory tract and prevent acute exacerbation of COPD. In the study, 144 patients with stable phase of moderate-to-very severe COPD will be recruited and randomized into aerosol-inhaled amikacin group, oral probiotics group, combined vaccination group and the control group at a 1:1:1:1 ratio. The primary outcome is time to the first COPD exacerbation. Other endpoints include colonization of potential pathogenic bacteria in induced sputum, microbiome in induced sputum, pulmonary function and symptoms of patients, inflammation level and adverse events, serious adverse events, and death.

Preventive Effects of Qingfei Yihuo Capsules () on Air Pollution Associated Exacerbation of Chronic Obstructive Pulmonary Disease: A Single-blind, Randomized, Controlled Trial

OBJECTIVE

To investigate the efficacy of Qingfei Yihuo Capsules (, QYCs) in preventing the air pollution associated exacerbation of chronic obstructive pulmonary disease (COPD).

METHODS

This was a prospective, parallel, single-blind, randomized, placebo-controlled trial. Sixty patients with stable Group D COPD were randomly allocated to receive either oral QYCs (intervention group) or placebos (control group, 30 cases per group) for 15 days in the presumed high-incidence air pollution season and followed-up for 1 year. Both groups were given individualized Western medicine therapy according to the Global Initiative for Chronic Obstructive Lung Disease criteria as usual. Total and separate numbers of acute exacerbation (AE) associated with striking air pollution was the primary outcomes. Secondary outcomes included total numbers of deteriorating respiratory symptoms and separate numbers associated with striking air pollution, as well as scores of COPD Assessment Test (CAT) and modified Medical Research Council Scale (mMRC).

RESULTS

All the 60 patients completed the study. There was no statistical significance in total numbers of AE between the two groups (P>0.05). Compared with the control group, a significant reduction in air-pollution associated numbers of deteriorated respiratory symptoms was observed in the intervention group (1.9-1.2 vs. 3.6-2.4, P<0.01). At the end of follow-up, there was no significant difference in CAT and mMRC scores between the two groups (P>0.05). Only 2 patients in the intervention group reported diarrhea and recovered after drug discontinuance.

CONCLUSION

For patients with Group D COPD, oral QYCs in high-incidence season of air pollution can effectively mitigate respiratory symptoms associated with air pollution, although there was no evidence that it had a significant reductive effect on AEs. (Registered at Chinese Clinical Trial Registry, registration No. ChiCTR-IOR-17013827).

Mediated Drug Release from Nanovehicles by Black Phosphorus Quantum Dots for Efficient Therapy of Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is an intractable disease involving a sticky mucus layer and nanoagents with mucus-penetrating capability offer a new way to deliver drugs. However, drug release from nanovehicles requires optimization to enhance the therapeutic effects of COPD therapy. Herein, black phosphorus quantum dots (BPQDs) are combined with PEGylated chitosan nanospheres containing the antibiotic amikacin (termed PEG@CS/BPQDs-AM NPs). As a drug-delivery system, the hydrophilicity of PEG and positive charge of CS facilitate the penetration of nanovehicles through the mucus layer. The nanovehicles then adhere to the mucous membrane. Furthermore, the BPQDs degrade rapidly into nontoxic PO₄ ^3- and acidic H⁺ , thereby promoting the dissociation of PEGylated CS nanospheres, accelerating the release of AM, decreasing the vitality of biofilms for ease of eradication. Our results reveal that drug delivery mediated by BPQDs is a feasible and desirable strategy for precision medicine and promising for the clinical therapy of COPD.

Initial diagnosis and management of adult community-acquired pneumonia: a 5-day prospective study in Shanghai

Background

Despite the release of a national guideline in 2016, the actual practices with respect to adult community-acquired pneumonia (CAP) remain unknown in China. We aimed to investigate CAP patient management practices in Shanghai to identify potential problems and provide evidence for policy making.

Methods

A short-period, 5-day prospective cross-sectional study was performed with sampled pulmonologists from 36 hospitals, encompassing all the administrative districts of Shanghai, during January 8–12, 2018. The medical information was recorded and analyzed for the patients with the diagnosis of CAP who were cared for by 46 pulmonologists during the study period.

Results

Overall, 435 patients were included in the final analysis, and 94.3% had a low risk of death in terms of CRB-65 criteria (C: disturbance of consciousness, R: respiratory rate, B: blood pressure, 65: age). When diagnosed with CAP, 70.1% of patients were not evaluated using the CURB-65 score (CRB-65 + U: urea nitrogen), but most patients (95.4%) were evaluated using CRB-65. Time to achieve clinical stability was longer in patients with hypoxemia than in those without hypoxemia (8.42±6.36 vs. 5.53±4.12 days, P=0.004). Overall, 84.4% of patients with a CRB-65 score of 0 were administered antibiotics intravenously, and 19.4% were still hospitalized after excluding hypoxemia and comorbidities. The average duration of antibiotic treatment was 10.4±4.9 days. Overall, 72.6% of patients received antibiotics covering atypical pathogens whose time to clinical stability was significantly shortened compared with those without coverage, but the antibiotic duration was similar and not correspondingly shortened.

Conclusions

CRB-65 seems to be more practical than CURB-65 for the initial evaluation of CAP in the context of local practice, and oxygenation assessment should be included in the evaluation of severity. Overtreatment may be relatively common in patients at low risk of death, including unreasonable hospitalization, intravenous administration, and antibiotic duration.

Experimental and theoretical insight into hydroxyl and sulfate radicals-mediated degradation of carbamazepine

Carbamazepine (CBZ), a widely detected pharmaceutical in wastewaters, cannot currently be treated by conventional activated sludge technologies, as it is highly resistant to biodegradation. In this study, the degradation kinetics and reaction mechanisms of CBZ by hydroxyl radical (OH) and sulfate radical ()-based advanced oxidation processes (AOPs) were investigated with a combined experimental/theoretical approach. We first measured the UV absorption spectrum of CBZ and compared it to the theoretical spectrum. The agreement of two spectra reveals an extended π-conjugation system on CBZ molecular structure. The second-order rate constants of OH and with CBZ, measured by competition kinetics method, were (4.63 ± 0.01) × 10⁹ M^-1 s^-1 and (8.27 ± 0.01) × 10⁸ M^-1 s^-1, respectively at pH 3. The energetics of the initial steps of CBZ reaction with OH and were also calculated by density functional theory (DFT) at SMD/M05-2X/6-311++G**//M05-2X/6-31 + G**level. Our results reveal that radical addition is the dominant pathway for both OH and . Further, compared to the positive ΔG_R⁰ value for the single electron transfer (SET) reaction pathway between CBZ and OH, the ΔG_R⁰ value for SET reaction between CBZ and is negative, showing that this reaction route is thermodynamically favorable. Our results demonstrated the remarkable advantages of AOPs for the removal of refractory organic contaminants during wastewater treatment processes. The elucidation of the pathways for the reaction of OH and with CBZ are beneficial to predict byproducts formation and assess associated ecotoxicity, providing an evaluation mean for the feasibility of AOPs application.

Evidence and evolution of Criegee intermediates, hydroperoxides and secondary organic aerosols formedviaozonolysis of α-pinene

The first experimental evidence of Criegee intermediates formedviaα-pinene ozonolysis and the formation of secondary organic aerosols is reported using a rapid scan time-resolved FTIR spectrometer coupled with a long-path aerosol cooling chamber.

Elevated serum procalcitonin level in patients with chronic kidney disease without infection: A case-control study

Background

Inflammation is a necessary component of chronic kidney disease (CKD) that can be attributed to an accumulation of toxins and a reduced clearance of proinflammatory cytokines. Procalcitonin (PCT) is a widely applied biomarker in the diagnosis of infection, and considering the presence of pre‐existing inflammation in CKD patients, the PCT level could be high in such a population; however, no reference value for PCT in CKD patients has been available to date.

Methods

During the present study period, 361 CKD patients and 119 healthy controls were included. The PCT level and other biochemistry parameters were assayed by using a COBAS system. Statistical analysis was conducted to compare the differences in PCT levels and other biochemistry parameters between the two groups, and linear regression was used to assess the correlation between two variables. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the performance of PCT and the optimal cutoff value to differentiate between CKD patients and healthy controls.

Results

The PCT level in CKD patients was significantly higher than that in healthy controls, and among the CKD patients, the PCT level was increased with advanced clinical stage. Moreover, PCT was moderately correlated with CysC. The optimal off‐value was 0.075 with a sensitivity of 94.7% and specificity of 90.8%.

Conclusion

The PCT level was significantly higher in CKD patients than in healthy controls, and the reference value for CKD patients should be adjusted to avoid unnecessary antibiotic treatments which may pose a negative impact on residual renal function.

Anatomic extent of lymph node metastases as an independent prognosticator in node-positive major salivary gland carcinoma: A study of the US SEER database and a Chinese multicenter cohort

BACKGROUND

We aimed to explore whether the anatomic extent of lymph node metastases (AE-LNM) could independently predict prognosis of node-positive major salivary gland carcinoma (MaSGC).

METHODS

A total of 376 pathologically node-positive MaSGC patients were identified from the Surveillance, Epidemiology and End Results database and constituted the training cohort. Using the X-Tile program, these patients were divided into three groups based on AE-LNM degrees. Discrimination of overall survival (OS) and disease-specific survival (DSS) was evaluated and compared with the 8th American Joint Committee on Cancer (AJCC) pN classification. The results were externally validated by 220 patients in a Chinese multicenter cohort (Validation cohort).

RESULTS

Using the training cohort, AE-LNM was divided into Extent 1 (spread to parotid LNs or level I), Extent 2 (spread to level II-IV) and Extent 3 (spread to level V or bilateral LNs or rare LNs). Regarding both OS and DSS, the AE-LNM model revealed clear separation of survival curves, while the pN classification failed to discriminate the prognosis of pN1 and pN2 patients. When we incorporated both the AE-LNM model and AJCC pN classification into the same multivariate Cox analyses, AE-LNM was still an independent prognostic factor, while the AJCC pN classification lost its significance. These results were externally validated by the validation cohort.

CONCLUSION

AE-LNM is an independent nodal prognosticator for node-positive MaSGC and may have improved discriminative ability over the current AJCC pN classification. Integration of anatomic extent of LNM into the current AJCC N classification could be considered.

Development of a Nomogram to Predict the Risk of 30-Day Re-Exacerbation for Patients Hospitalized for Acute Exacerbation of Chronic Obstructive Pulmonary Disease

Acute exacerbation (AE) is the main cause of increased disability and mortality for patients with Chronic Obstructive Pulmonary Disease (COPD). Short-term re-exacerbation after discharge is common for in-hospital patients with AECOPD. Thus, we aimed to design a scoring system to effectively predict the 30-day re-exacerbation using simple and easily accessible variables. We retrospectively enrolled 686 cases hospitalized for AECOPD in two Chinese hospitals from 2005 to 2017. A variety of parameters were collected like demographics, clinical manifestations and treatments in stable and AE period. The optimal subset of covariates in the multivariate logistic analysis was identified by the smallest Akaike Information Criterion (AIC) and was further used to develop a practical and reliable nomogram to predict the 30-day re-exacerbation. The efficacy of the nomogram was internally validated by concordance index (C-index) and a calibration plot. The incidence of 30-day re-exacerbation was 15.8%. Based on the smallest AIC, eight easily-accessible parameters were included in the nomogram, including sex, COPD assessment test (CAT) scores, AE with respiratory failure in the previous year, new purulent sputum, new cardiovascular events, combined antibiotic therapy, theophylline therapy for AE and ICU admission. Our nomogram revealed good discriminative ability with the C-index of 0.702. The calibration curve showed good agreement between nomogram-predicted probability and actual observation. Incorporating eight common variables, a nomogram for 30-day re-exacerbation after discharge with high predictive performance was constructed for patients with AECOPD, which was helpful in predicting individualized risk of re-exacerbation and offering individualized post-discharge support.

Altered serum levels of type I collagen turnover indicators accompanied by IL-6 and IL-8 release in stable COPD

Background

COPD, characterized by chronic inflammation and airway remodeling, has significant pathological alterations in composition and deposition of the extracellular matrix. The expression of procollagen 1 C-terminal peptide (PICP) and collagen type 1 C-terminal telopeptide (ICTP), two major by-products in the synthesis and degradation of collagen, was shown to be positively correlated with inflammatory mediator levels in previous studies.

Purpose

In this study, we investigated whether the serum concentrations of PICP and ICTP were associated with the inflammation level for patients with stable COPD.

Patients and methods

We collected serum samples from 25 control subjects and 20 patients with stable COPD from December 2011 to October 2012 in Shanghai Zhongshan Hospital and Shanghai Dahua Hospital. We determined concentrations of PICP, ICTP, C-reactive protein (CRP), IL-6, IL-8, and tumor necrosis factor (TNF)-α by using enzyme-linked immunosorbent assay methods.

Results

Demographic characteristics were comparable between the two groups. In patients with stable COPD, serum levels of CRP, IL-6, IL-8, and TNF-α were all elevated compared to control subjects, but only changes of IL-6 achieved statistical significance. Serum concentration of PICP was significantly elevated in patients with COPD, and level of ICTP was slightly decreased. Moreover, serum concentrations of PICP were positively correlated with the levels of both IL-6 and IL-8.

Conclusion

The increased levels of serum PICP in COPD might indicate the condition of airway remodeling, and IL-6 and/or IL-8 might play an important role in stimulating collagen synthesis.

Treating Clinically Node-Negative Insular Thyroid Carcinoma without Prophylactic Central Compartment Neck Dissection Is Associated with Decreased Survival Regardless of T Staging and Administration of Radioactive Iodine Therapy: The First Evidence

For the rare but aggressive insular thyroid carcinoma (ITC), there's no clear evidence to determine whether prophylactic central compartment neck dissection (CCND) is necessary for cN0 disease. This study provides the first evidence that treating cN0 ITC without prophylactic CCND is associated with decreased survival regardless of T staging and administration of RAI therapy. Background. Regarding the rare but aggressive insular thyroid carcinoma (ITC), the value of prophylactic central compartment neck dissection (CCND) for clinically node-negative (cN0) disease is unclear. We aimed to provide the first evidence. Methods. N0 and pN1a ITC patients were identified from the Surveillance, Epidemiology, and End Results database. These patients were divided into thyroid-surgery + CCND group (pN0/pN1a patients confirmed by CCND) and thyroid-surgery group (cN0 patients without CCND). Differences in overall survival (OS) and disease-specific survival (DSS) between the two groups were evaluated. Subgroup analyses were also conducted. Results. Of the overall 112 patients, 44 (39.3%) received CCND. On multivariate analyses, the lobectomy ± isthmusectomy/total-thyroidectomy (Lob/TT) group demonstrated poorer OS and DSS than the Lob/TT + CCND group (P < 0.05). When we separately analyzed patients treated by TT, multivariate analyses showed the TT group still revealed compromised OS and DSS than the TT + CCND group (P < 0.05). Furthermore, absence of CCND independently predicted decreased OS no matter whether radioactive iodine (RAI) was administered. Similar results were obtained for T3/T4 patients. Moreover, for T1/T2 patients receiving CCND, 0/12 died during the study period, while for T1/T2 patients without CCND, 8/23 (34.8%) died, 5/23 (21.7%) due to ITC. Conclusion. Regardless of T staging and RAI treatment, cN0-ITC patients without CCND had decreased survival compared with pN0/pN1a patients receiving CCND. Therefore, if a cN0 patient is diagnosed with ITC, prophylactic CCND may be considered as a secondary procedure (postoperatively diagnosed) or a primary procedure (preoperatively/intraoperatively diagnosed). Prospective studies are expected to validate the conclusion.

Identification of novel candidate genes involved in the progression of emphysema by bioinformatic methods

Purpose

By reanalyzing the gene expression profile GSE76925 in the Gene Expression Omnibus database using bioinformatic methods, we attempted to identify novel candidate genes promoting the development of emphysema in patients with COPD.

Patients and methods

According to the Quantitative CT data in GSE76925, patients were divided into mild emphysema group (%LAA-950<20%, n=12) and severe emphysema group (%LAA-950>50%, n=11). Differentially expressed genes (DEGs) were identified using Agilent GeneSpring GX v11.5 (corrected P-value <0.05 and |Fold Change|>1.3). Known driver genes of COPD were acquired by mining literatures and retrieving databases. Direct protein–protein interaction network (PPi) of DEGs and known driver genes was constructed by STRING.org to screen the DEGs directly interacting with driver genes. In addition, we used STRING.org to obtain the first-layer proteins interacting with DEGs’ products and constructed the indirect PPi of these interaction proteins. By merging the indirect PPi with driver genes’ PPi using Cytoscape v3.6.1, we attempted to discover potential pathways promoting emphysema’s development.

Results

All the patients had COPD with severe airflow limitation (age=62±8, FEV₁%=28±12). A total of 57 DEGs (including 12 pseudogenes) and 135 known driving genes were identified. Direct PPi suggested that GPR65, GNB4, P2RY13, NPSR1, BCR, BAG4, and IMPDH2 were potential pathogenic genes. GPR65 could regulate the response of immune cells to the acidic microenvironment, and NPSR1’s expression on eosinophils was associated with asthma’s severity and IgE level. Indirect merging PPi demonstrated that the interacting network of TP53, IL8, CCR2, HSPA1A, ELANE, PIK3CA was associated with the development of emphysema. IL8, ELANE, and PIK3CA were molecules involved in the pathological mechanisms of emphysema, which also in return proved the role of TP53 in emphysema.

Conclusion

Candidate genes such as GPR65, NPSR1, and TP53 may be involved in the progression of emphysema.

Kinetic and mechanistic aspects of hydroxyl radical‒mediated degradation of naproxen and reaction intermediates

Hydroxyl radical (^•OH) based advanced oxidation technologies (AOTs) are effective for removing non‒steroidal anti-inflammatory drugs (NSAIDs) during water treatment. In this study, we systematically investigated the degradation kinetics of naproxen (NAP), a representative NSAID, with a combination of experimental and theoretical approaches. The second-order rate constant (k) of ^•OH oxidation of NAP was measured to be (4.32 ± 0.04) × 10⁹ M^-1 s^-1, which was in a reasonable agreement with transition state theory calculated k value (1.08 × 10⁹ M^-1 s^-1) at SMD/M05-2X/6-311++G**//M05-2X/6-31+G** level of theory. The calculated result revealed that the dominant reaction intermediate is 2‒(5‒hydroxy‒6‒methoxynaphthalen‒2‒yl)propanoic acid (HMNPA) formed via radical adduct formation pathway, in which ^•OH addition onto the ortho site of the methoxy-substituted benzene ring is the most favorable pathway for the NAP oxidation. We further investigated the subsequent ^•OH oxidation of HMNPA via a kinetic modelling technique. The k value of the reaction of HMNPA and ^•OH was determined to be 2.22 × 10⁹ M^-1 s^-1, exhibiting a similar reactivity to the parent NAP. This is the first study on the kinetic and mechanistic aspects of NAP and its reaction intermediates. The current results are valuable in future study evaluating and extending the application of ^•OH based AOTs to degrade NAP and other NSAIDs of concern in water treatment plants.

Central Lymph Node Status has Significant Prognostic Value in the Clinically Node-Negative Tall-Cell Variant of Papillary Thyroid Cancer Regardless of T-Staging and Radioactive Iodine Administration: First Evidence From a Population-Based Study

BACKGROUND

The prognostic value of central lymph node (CLN) status in papillary thyroid cancer (PTC) remains controversial. This study aimed to provide the first evidence on this issue for the aggressive tall-cell variant (TCV) subtype.

METHODS

The study identified TCV patients from the Surveillance, Epidemiology, and End Results database. The Kaplan-Meier method, log-rank test, and multivariate Cox regression models were used for analysis.

RESULTS

Of the 744 patients included, 404 were recorded as N0, which were pathologically or only clinically confirmed. Overall survival (OS) and cancer-specific survival (CSS) did not differ significantly between the N0 and pN1a patients (p > 0.05). To investigate the reason, the N0 patients were subdivided according to the number of examined lymph nodes (ELN). The patients with a N0 diagnosis confirmed by two or more ELNs (N0-e2+) showed significantly better outcomes than the pN1a patients and their N0 counterparts without ELN (N0-e0) (p < 0.05), whereas the N0-e0 and pN1a groups demonstrated comparable outcomes in both the log-rank and multivariate analyses (p > 0.05). Moreover, the subgroup analyses showed that even among the patients with early T-staging (T1-T2) or receipt of radioactive iodine (RAI) therapy, the N0-e0 patients still demonstrated compromised OS compared with the N0-e2+ group (p < 0.05).

CONCLUSION

The cN0 patients without ELN (N0-e0) had outcomes similar to those of the pN1a patients, but showed a poorer OS than the N0-e2+ group regardless of T-staging and RAI administration, suggesting that occult CLN metastases might act as a negative prognosticator in cN0 TCV. Therefore, prophylactic central neck dissection might be considered for biopsy-proven cN0 TCV patients. Prospective studies are expected to further validate our conclusions.

Development of comprehensive nomograms for evaluating overall and cancer-specific survival of laryngeal squamous cell carcinoma patients treated with neck dissection

Background

Neck dissection for laryngeal squamous cell carcinoma (LSCC) patients could provide complementary prognostic information for AJCC N staging, like lymph node ratio (LNR). The aim of this study was to develop effective nomograms to better predict survival for LSCC patients treated with neck dissection.

Results

2752 patients were identified and randomly divided into training (n = 2477) and validation (n = 275) cohorts. The 3- and 5-year probabilities of cancer-specific mortality (CSM) were 30.1% and 37.2% while 3- and 5-year death resulting from other causes (DROC) rate were 6.2% and 11.3%, respectively. 13 significant prognostic factors including LNR for overall (OS) and 12 (except race) for CSS were enrolled in the nomograms. Concordance index as a commonly used indicator of predictive performance, showed the nomograms had superiority over the no-LNR models and TNM classification (Training-cohort: OS: 0.713 vs 0.703 vs 0.667, CSS: 0.725 vs 0.713 vs 0.688; Validation-cohort: OS: 0.704 vs 0.690 vs 0.658, cancer-specific survival (CSS): 0.709 vs 0.693 vs 0.672). All calibration plots revealed good agreement between nomogram prediction and actual survival.

Materials and Methods

We identified LSCC patients undergoing neck dissection diagnosed between 1988 and 2008 from Surveillance, Epidemiology, and End Results (SEER) database. Optimal cutoff points were determined by X-tile program. Cumulative incidence function was used to analyze cancer-specific mortality (CSM) and death resulting from other causes (DROC). Significant predictive factors were used to establish nomograms estimating overall (OS) and cancer-specific survival (CSS). The nomograms were bootstrapped validated both internally and externally.

Conclusions

Comprehensive nomograms were constructed to predict OS and CSS for LSCC patients treated with neck dissection more accurately.

A study of the competitive multiple hydrogen bonding effect and its associated excited-state proton transfer tautomerism

1,8-Dihydroxynaphthalene-2,7-dicarbaldehyde (DHDA) has been strategically designed and synthesized with the aim to study the competitive multiple hydrogen bonding (H-bonding) effect and the associated excited-state intramolecular proton transfer reaction (ESIPT). In nonpolar solvents such as cyclohexane, equilibrium exists between the two H-bonding isomers DHDA-23_OO and DHDA-23_OI, both of which possess double intramolecular H-bonds. In polar, aprotic solvents such as CH₂Cl₂, DHDA-23_OO becomes the predominant species. Due to various degrees of H-bond induced changes of electronic configuration each isomer reveals a distinct absorption feature and excited-state behavior, in which DHDA-23_OI in cyclohexane undergoes double ESIPT in a stepwise manner, giving the first and second proton-transfer tautomer emissions maximized at ∼500 nm and 660 nm, respectively. As for DHDA-23_OO both single and double ESIPT are prohibited, resulting in an intense normal 450 nm emission band. In a single crystal DHDA-23_OI is the dominant species, which undergoes excited state double proton transfer, giving intense emission bands at 530 nm and 650 nm. The mechanism associated with competitive multiple H-bonding energetics and ESIPT was underpinned by detailed spectroscopy/dynamics and computational approaches.

Differentiation of human dental pulp stem cells into neuronal by resveratrol

Dental pulp stem cells (DPSCs) have been proposed as a promising source of stem cells in nerve regeneration due to their close embryonic origin and ease of harvest. Resveratrol (RSV) is a natural polyphenolic and possesses many biological functions such as anti-inflammatory activity and protection against atherosclerosis and neuroprotective activities. There is increasing evidence showing that RSV plays a pivotal role in neuron protection and neuronal differentiation. In this study, we isolated DPSCs from impacted third molars and investigated whether RSV induces neuronal differentiation of DPSCs. To avoid loss of DPSCs multipotency, all the experiments were conducted on cells at early passages. RT-PCR results showed that RSV-treated DPSCs (RSV-DPSCs) significantly increased the expression of the neuroprogenitor marker Nestin. When RSV-DPSCs were differentiated with neuronal induction media (RSV-dDPSCs), they showed a cell morphology similar to neurons. The expression of neuronal-specific marker genes Nestin, Musashi, and NF-M in RSV-dDPSCs was significantly increased. Immunocytochemical staining and Western blot analysis showed that the expression of neuronal marker proteins, Nestin, and NF-M, was significantly increased in RSV-dDPSCs. Therefore, we have shown that RSV treatment, along with the use of neuronal induction media, effectively promotes neuronal cell differentiation of DPSCs.

[Effects of Wnt3a on osteogenic differentiation of dental pulp stem cells]

Objective: To investigate the effect of Wnt3a on osteogenic differentiation of human dental pulp stem cells (DPSC). Methods: DPSCs were subjected to different concentrations of Wnt3a (0, 5, 20, 50 and 100 μg/L) and at seven days after culture the alkaline phosphatase (ALP) activity was tested. Mineralized nodule formation was examined by alizarin red staining. Osteogenic-related gene expression of bone sialoprotein (BSP), osteocalcin (OCN), collagen type Ⅰ (COL-Ⅰ), Runt-related transcription factor-2 (RUNX2) was examined by quantitative real-time PCR (qPCR). Results: After seven days of induction by DPSC, Wnt3a protein could inhibit the ALP activity (concentration 0: 1.076±0.203, 5 μg/L: 0.828±0.118, 20 μg/L: 0.505±0.044, 50 μg/L: 0.499±0.038, 100 μg/L: 0.483±0.060). The expression of OCN in 5 μg/L Wnt3a group (0.092±0.005) was lower than that in culture medium (0.858±0.190)(P<0.05). Alizarin red staining showed that 5 μg/L Wnt3a had no mineralization induction effect on DPSC. Conclusions: Wnt3a could inhibit osteogenic differentiation of dental pulp stem cells.

[The adhesion separation operation with CO₂ laser combined withtriamcinolone acetonide vocal cord submucosal injection for the treatment to vocal cord adhesion]

Objective:To investigate the effect of adhesion separation operation with CO₂ laser via prop-up laryngoscope combine with triamcinolone acetonide submucosal injection via electrolaryngoscope to vocal cords adhesion.Method:Sixteen cases of vocal cord adhesion patients(2 cases of children,14 cases of adult) were enrolled in the study. Fourteen patients had the history of surgery(Reinke edema,vocal polyp,pediatric laryngeal papilloma,laryngeal cancer),2 cases were diagnosed as laryngeal tuberculosis. Adhesion separation operation and triamcinolone acetonide submucosal injection(once a week,three weeks) were conducted. All patients were examined with electronic laryngoscope every month for six monthes.Result:Fourteen patients had good triangle shape of glottis vocalis and good sound voice. One cases of laryngeal cancer and 1 cases of laryngeal tuberculosis patients still had adhesion in the anterior commissure of the vocal cords,but with the improvement in breathing and pronunciation.Conclusion:Adhesion separation operation with CO₂ laser via prop-up laryngoscope combine with triamcinolone acetonide submucosal injection via electrolaryngoscope were effective for treatment to vocal cord adhesion,whichimprove the patient's breathing and voice with little trauma and few complications.

Collision-induced dissociation of sodiated glucose and identification of anomeric configuration

Difference in dehydration barrier heights results in different branching ratio, a simple and fast method for anomeric configuration identification.

[Responses of Physiological Indices of Typical Submerged Macrophytes to Water Quality in Taihu Lake]

It was well known that physiological indices of submerged macrophytes could reflect change of water quality. The correlation between physiological indices of submerged macrophytes and change of water quality was studied under the cooperation of in-situ monitoring and lab analysis, combined with measuring Chlorophyll and free proline (PRO) contents as well as peroxidase (POD) activities in the leaves of Potamogeton wrightii Morong and Potamogeton crispus L. under different water quality and nutrition status. The results showed: ①there were significant spatial differences among water factors and the comprehensive eutrophication index (TLI) of distribution areas of Potamogeton wrightii Morong and Potamogeton crispus L. Mesotrophic water was more suitable for the growth of Potamogeton wrightii Morong, while Potamogeton crispus L. grew well in eutrophic water. ②there were significant spatial differences among physiological indices of Potamogeton wrightii Morong and Potamogeton crispus L. in Taihu Lake. Besides, there were significant relationships between Chlorophyll contents, POD activities of two species and TLI. ③water transparency as well as nitrogen and phosphorus nutrition were important factors leading to changes in Chlorophyll contents and POD activities of Potamogeton wrightii Morong and Potamogeton crispus L.. The findings from this study indicate that physiological properties of Potamogeton wrightii Morong and Potamogeton crispus L. have a very close correlation with nutrition status and physiochemical properties of water.

Theoretical investigation of low detection sensitivity for underivatized carbohydrates in ESI and MALDI

Electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) mainly generate protonated ions from peptides and proteins but sodiated (or potassiated) ions from carbohydrates. The ion intensities of sodiated (or potassiated) carbohydrates generated by ESI and MALDI are generally lower than those of protonated peptides and proteins. Ab initio calculations and transition state theory were used to investigate the reasons for the low detection sensitivity for underivatized carbohydrates. We used glucose and cellobiose as examples and showed that the low detection sensitivity is partly attributable to the following factors. First, glucose exhibits a low proton affinity. Most protons generated by ESI or MALDI attach to water clusters and matrix molecules. Second, protonated glucose and cellobiose can easily undergo dehydration reactions. Third, the sodiation affinities of glucose and cellobiose are small. Some sodiated glucose and cellobiose dissociate into the sodium cations and neutral carbohydrates during ESI or MALDI process. The increase of detection sensitivity of carbohydrates in mass spectrometry by various methods can be rationalized according to these factors. Copyright © 2016 John Wiley & Sons, Ltd.

Theoretical Study on the Noble Gas Exchange Reactions of Ng + HNBNg'(+) → Ng' + HNBNg(+) (Ng, Ng' = He, Ne, Ar, Kr, and Xe)

High-level correlated electronic structure calculation and dual-level variational transition state theory with multidimensional tunneling calculation for rate constants have been performed on four noble gas exchange reactions [(1) He + HNBHe'(+) → He' + HNBHe(+), (2) He + HNBNe(+) → Ne + HNBHe(+), (3) Ne + HNBNe'(+) → Ne' + HNBNe(+), and (4) Ar + HNBAr'(+) → Ar' + HNBAr(+)] and on three (3)He isotopic analogues (He + HNB(3)He(+), (3)He + HNBHe(+), and (3)He + HNB(3)He(+)) of the first reaction. The classical barrier heights were predicted to be 8.9, 6.8, 5.7, and 5.5 kcal/mol for the four reactions, respectively. The tunneling effects were found to be important below 250 K for the He reactions and below 150 K for the Ne and Ar reactions. Kinetic helium isotope effects as large as 7.8 at 100 K were predicted for the (3)He + HNB(3)He(+) reaction. Additionally, the structures and energies of the Kr + HNBKr'(+) and Xe + HNBXe'(+) systems have also been studied.

Kinetics and Mechanism of the Oxidation of Cyclic Methylsiloxanes by Hydroxyl Radical in the Gas Phase: An Experimental and Theoretical Study

The ubiquitous presence of cyclic volatile methylsiloxanes (cVMS) in the global atmosphere has recently raised environmental concern. In order to assess the persistence and long-range transport potential of cVMS, their second-order rate constants (k) for reactions with hydroxyl radical ((•)OH) in the gas phase are needed. We experimentally and theoretically investigated the kinetics and mechanism of (•)OH oxidation of a series of cVMS, hexamethylcyclotrisiloxane (D3), octamethycyclotetrasiloxane (D4), and decamethycyclopentasiloxane (D5). Experimentally, we measured k values for D3, D4, and D5 with (•)OH in a gas-phase reaction chamber. The Arrhenius activation energies for these reactions in the temperature range from 313 to 353 K were small (-2.92 to 0.79 kcal·mol(-1)), indicating a weak temperature dependence. We also calculated the thermodynamic and kinetic behaviors for reactions at the M06-2X/6-311++G**//M06-2X/6-31+G** level of theory over a wider temperature range of 238-358 K that encompasses temperatures in the troposphere. The calculated Arrhenius activation energies range from -2.71 to -1.64 kcal·mol(-1), also exhibiting weak temperature dependence. The measured k values were approximately an order of magnitude higher than the theoretical values but have the same trend with increasing size of the siloxane ring. The calculated energy barriers for H-atom abstraction at different positions were similar, which provides theoretical support for extrapolating k for other cyclic siloxanes from the number of abstractable hydrogens.

Optically Triggered Stepwise Double-Proton Transfer in an Intramolecular Proton Relay: A Case Study of 1,8-Dihydroxy-2-naphthaldehyde

1,8-Dihydroxy-2-naphthaldehyde (DHNA), having doubly intramolecular hydrogen bonds, was strategically designed and synthesized in an aim to probe a long-standing fundamental issue regarding synchronous versus asynchronous double-proton transfer in the excited state. In cyclohexane, DHNA shows the lowest lying S0 →S1 (π-π*) absorption at ∼400 nm. Upon excitation, two large Stokes shifted emission bands maximized at 520 and 650 nm are resolved, which are ascribed to the tautomer emission resulting from the first and second proton-transfer products, denoted by TA* and TB*, respectively. The first proton transfer (DHNA* → TA*) is ultrafast (< system response of 150 fs), whereas the second proton transfer is reversible, for which the rates of forward (TA* → TB*) and backward (TA* ← TB*) proton transfer were determined to be (1.7 ps)(-1) and (3.6 ps)(-1), respectively. The fast equilibrium leads to identical population lifetimes of ∼54 ps for both TA* and TB* tautomers. Similar excited-state double-proton transfer takes place for DHNA in a single crystal, resulting in TA* (560 nm) and TB* (650 nm) dual-tautomer emission. A comprehensive 2D plot of reaction potential energy surface further proves that the sequential two-step proton motion is along the minimum energetic pathway firmly supporting the experimental results. Using DHNA as a paradigm, we thus demonstrate unambiguously a stepwise, proton-relay type of intramolecular double-proton transfer reaction in the excited state, which should gain fundamental understanding of the multiple proton transfer reactions.

Highly Selective Dissociation of a Peptide Bond Following Excitation of Core Electrons

The controlled breaking of a specific chemical bond with photons in complex molecules remains a major challenge in chemistry. In principle, using the K-edge absorption of a particular atomic element, one might excite selectively a specific atomic entity in a molecule. We report here highly selective dissociation of the peptide bonds in N-methylformamide and N-methylacetamide on tuning the X-ray wavelength to the K-edge absorption of the atoms connected to (or near) the peptide bond. The high selectivity (56-71%) of this cleavage arises from the large energy shift of X-ray absorption, a large overlap of the 1s orbital and the valence π* orbital that is highly localized on a peptide bond with antibonding character, and the relatively low bond energy of the peptide bonds. These characteristics indicate that the high selectivity on bond dissociation following core excitation could be a general feature for molecules containing peptide bonds.

Subtraction suppressive hybridisation analysis of differentially expressed genes associated with puberty in the goat hypothalamus

The cost of developing replacement nanny goats could be reduced by decreasing the age at puberty because this way nanny goats could be brought into production at an earlier age. The aim of the present study was to screen genes related to puberty to investigate the molecular mechanisms of puberty. Subtracted cDNA libraries were constructed for hypothalami from juvenile (Group A), pubertal (Group B) and age-matched control pubertal (Group E) Jining grey (JG) and Liaoning cashmere (LC) goats using suppression subtractive hybridisation (SSH). Differentially expressed genes were analysed by bioinformatics methods. There were 203 expressed sequence tags (ESTs) in the subtracted cDNA libraries that were differentially expressed between JG and LC goats at the juvenile stage, 226 that were differentially expressed at puberty and 183 that were differentially expressed in the age-matched control group. The differentially expressed ESTs in each subtracted cDNA library were classified as known gene, known EST and unknown EST according to sequence homology in the GenBank non-redundant (NR) and EST database. According to gene function analysis in the COG (Cluster of Orthologous Groups) database, the known genes were grouped into 10 subdivisions in Group A, into seven subdivisions in Group E and into nine subdivisions in Group B under three categories: cellular processes and signalling, information storage and processing, and metabolism. Pathway analysis in the KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway database of known genes revealed that the three pathways that most differentially expressed genes were involved in were metabolic pathways, Parkinson's disease and oxidative phosphorylation. Protein interaction analysis of the high homology genes revealed the most dominant network to be structure of ribosome/protein translation, oxidative phosphorylation and carbohydrate metabolism. The results reveal that the onset of puberty is a complex event involving multiple genes in multiple biological processes. The differentially expressed genes include genes related to both neuroendocrine and energy metabolism.

[Experiment and model simulation of self-purification capacity of nitrogen and phosphorus in Lake Taihu]

A field experiment was carried out in Zhushanhu in September, 2011. On the basis of mass balance, nutrients flow in and out of Zhushanhu and their Digestion-absorption law was illustrated through water quantity-water quality observation of bay heart, bay mouth and rivers around Zhushanhu, which provides basic data for the further research on the self-purification capacity of Lake Taihu. The EcoTaihu model was adopted to simulate the nutrients flow and their self-purification capacity of Lake Taihu. The simulated annual self-purification capacity of total nitrogen and total phosphorus of Zhushanhu was 1 911 t and 116 t, respectively, whereas the observed annual self-purification capacity of total nitrogen and total phosphorus of Zhushanhu was 1 979 t and 119 t, respectively. The model was validated by the observation data. The simulated result showed that the self-purification capacity of total nitrogen of Lake Taihu in year 2006, 2008 and 2010 was 4. 00 x 10(4) t, 4. 27 x 10(4) t and 4. 11 x 10(4) t, respectively, whereas the self-purification capacity of total phosphorus of Lake Taihu in year 2006, 2008 and 2010 was 1.56 x 10(3) t, 1.80 x 10(3) t and 1.71 x 10(3) t, respectively.

Theoretical prediction of new noble-gas molecules FNgBNR (Ng = Ar, Kr, and Xe; R = H, CH3, CCH, CHCH2, F, and OH)

We have computationally predicted a new class of stable noble-gas molecules FNgBNR (Ng = Ar, Kr, Xe; R = H, CH3, CCH, CHCH2, F, and OH). The FNgBNR were found to have compact structures with F-Ng bond lengths of 1.9-2.2 Å and Ng-B bond lengths of ~1.8 Å. The endoergic three-body dissociation energies of FNgBNH to F + Ng + BNH were calculated to be 12.8, 31.7, and 63.9 kcal mol(-1), for Ng = Ar, Kr, and Xe, respectively at the CCSD(T)/CBS level. The energy barriers of the exoergic two-body dissociation to Ng + FBNH were calculated to be 16.1, 24.0, and 33.2 kcal mol(-1) for Ng = Ar, Kr, and Xe, respectively. Our results showed that the dissociation energetics is relatively insensitive to the identities of the terminal R groups. The current study suggested that a wide variety of noble-gas containing molecules with different types of R groups can be thermally stable at low temperature, and the number of potentially stable noble-gas containing molecules would thus increase very significantly. It is expected some of the FNgBNR molecules could be identified in future experiments under cryogenic conditions in noble-gas matrices or in the gas phase.

Theoretical analysis on the kinetic isotope effects of bimolecular nucleophilic substitution (S(N)2) reactions and their temperature dependence

Factors affecting the kinetic isotope effects (KIEs) of the gas-phase S(N)2 reactions and their temperature dependence have been analyzed using the ion-molecule collision theory and the transition state theory (TST). The quantum-mechanical tunneling effects were also considered using the canonical variational theory with small curvature tunneling (CVT/SCT). We have benchmarked a few ab initio and density functional theory (DFT) methods for their performance in predicting the deuterium KIEs against eleven experimental values. The results showed that the MP2/aug-cc-pVDZ method gave the most accurate prediction overall. The slight inverse deuterium KIEs usually observed for the gas-phase S(N)2 reactions at room temperature were due to the balance of the normal rotational contribution and the significant inverse vibrational contribution. Since the vibrational contribution is a sensitive function of temperature while the rotation contribution is temperature independent, the KIEs are thus also temperature dependent. For S(N)2 reactions with appreciable barrier heights, the tunneling effects were predicted to contribute significantly both to the rate constants and to the carbon-13, and carbon-14 KIEs, which suggested important carbon atom tunneling at and below room temperature.

Theoretical prediction on the structures and stability of the noble-gas containing anions FNgCC- (Ng=He, Ar, Kr, and Xe)

We have made high-level theoretical study on a new type of noble-gas (Ng) containing anions FNgCC(-). The calculated short Ng-CC bond lengths of 1.13, 1.77, 1.89, and 2.04 Å for Ng=He, Ar, Kr, and Xe, respectively, and the electron density distributions indicated strong covalent interactions between the Ng and CC induced by the polarizing fluoride ion. Except for FHeCC(-), the structures of all other FNgCC(-) were predicted to be linear. The intrinsic stability of the FNgCC(-) was studied by calculating the energies of the three-body dissociation reaction: FNgCC(-) → F(-) + Ng + CC and by calculating the energy barriers of the two-body dissociation reaction: FNgCC(-) → Ng + FCC(-). The results showed that FNgCC(-) (Ng=Ar, Kr, Xe) could be kinetically stable in the gas phase with the three-body dissociation energies of 17, 37, and 64 kcal/mol and two body-dissociation barriers of 22, 31, and 42 kcal/mol, respectively, at the coupled-cluster single double (triple)/aug-cc-pVQZ level of theory. The structures and the stability were also confirmed using the multi-reference CASPT2 calculation. Future experimental identification of the FNgCC(-) anions is expected under cryogenic conditions.

Photodissociation dynamics of methoxybenzoic acid at 193 nm

The theoretical prediction and experimental confirmation of the 1πσ* repulsive excited state along O-H bond of phenol have large impact on the interpretation of phenol and tyrosine photochemistry. In this work, we investigated the photodissociation dynamics of 2-, 3-, and 4-methoxybenzoic acid (MOBA) in a molecular beam at 193 nm using multimass ion imaging techniques. In addition, the ground state and the excited state potential energy surfaces of MOBA were investigated using ab initio calculations, and branching ratios were predicted by Rice-Ramsperger-Kassel-Marcus theory. The results show that (1) the excited state potential of 1πσ* along O-CH(3) bond remains similar to that of phenol and anisole, (2) CH(3) elimination is the major channel for three MOBA isomers, and (3) photofragment translational energy distributions show bimodal distributions, representing the dissociation on the ground state and repulsive excited state, respectively. Comparison to the study of hydroxbenzoic acid [Y. L. Yang, Y. A. Dyakov, Y. T. Lee, C. K. Ni, Y. L. Sun, and W. P. Hu, J. Chem. Phys. 134, 034314 (2011)] shows that only the intramolecular hydrogen bonding has significant effects on the excited state dynamics of phenol chromophores.