UHPLC-MS/MS Method Development and Validation for the Genotoxic Impurities Trimethyl Phosphate and Triisopropyl Phosphate of Elagolix Sodium.

Elagolix sodium is a gonadotropin-releasing hormone (GnRH) receptor antagonist that inhibits endogenous GnRH signaling by competitively binding to GnRH receptors in the pituitary gland to treat moderate to severe pain associated with endometriosis. To keep the safety and quality of the drug, a fast quantitative method by reversed-phase ultrahigh-performance liquid chromatography coupled with tandem mass spectrometry has been developed and validated for the identification, assay and estimation of potential genotoxic impurities trimethyl phosphate and triisopropyl phosphate in commercial batches of this active pharmaceutical ingredient in accordance with International Conference on Harmonization guidelines Q2 and M7. The method was validated by assessing specificity, sensitivity, linearity, the limit of quantification and detection, accuracy, precision and robustness for above analytes at a very low concentration, whose quantification and detection limits reached to 24 and 4.8 pg/ml, respectively, and the total run time for a single injection was 6 min.

Comparison of the efficacy and comfort of high-flow nasal cannula with different initial flow settings in patients with acute hypoxemic respiratory failure: a systematic review and network meta-analysis.

BACKGROUND: High-flow nasal cannula (HFNC) has been proven effective in improving patients with acute hypoxemic respiratory failure (AHRF), but a discussion of its use for initial flow settings still need to be provided. We aimed to compare the effectiveness and comfort evaluation of HFNC with different initial flow settings in patients with AHRF. METHODS: Studies published by October 10, 2022, were searched exhaustively in PubMed, Embase, Web of Science, Cochrane Library (CENTRAL), and the China National Knowledge Infrastructure (CNKI) database. Network meta-analysis (NMA) was performed with STATA 17.0 and R software (version 4.2.1). A Bayesian framework was applied for this NMA. Comparisons of competing models based on the deviance information criterion (DIC) were used to select the best model for NMA. The primary outcome is the intubation at day 28. Secondary outcomes included short-term and long-term mortality, comfort score, length of ICU or hospital stay, and 24-h PaO2/FiO2. RESULTS: This NMA included 23 randomized controlled trials (RCTs) with 5774 patients. With NIV as the control, the HFNC_high group was significantly associated with lower intubation rates (odds ratio [OR] 0.72 95% credible interval [CrI] 0.56 to 0.93; moderate quality evidence) and short-term mortality (OR 0.81 95% CrI 0.69 to 0.96; moderate quality evidence). Using HFNC_Moderate (Mod) group (mean difference [MD] - 1.98 95% CrI -3.98 to 0.01; very low quality evidence) as a comparator, the HFNC_Low group had a slight advantage in comfort scores but no statistically significant difference. Of all possible interventions, the HFNC_High group had the highest probability of being the best in reducing intubation rates (73.04%), short-term (82.74%) and long-term mortality (67.08%). While surface under the cumulative ranking curve value (SUCRA) indicated that the HFNC_Low group had the highest probability of being the best in terms of comfort scores. CONCLUSIONS: The high initial flow settings (50-60 L/min) performed better in decreasing the occurrence of intubation and mortality, albeit with poor comfort scores. Treatment of HFNC for AHRF patients ought to be initiated from moderate flow rates (30-40 L/min), and individualized flow settings can make HFNC more sensible in clinical practice.

The effects of anesthesia methods and anesthetics on postoperative delirium in the elderly patients: A systematic review and network meta-analysis.

Study objective: Postoperative delirium (POD) is one of the serious postoperative complications in elderly patients, which is always related to long-term mortality. Anesthesia is often considered a risk factor for POD. This systematic review and network meta-analysis (NMA) aimed to assess the impact of different anesthesia methods and anesthetics on POD. Measurements: We searched for studies published in PubMed, Embase, Web of Science, Scopus, and Cochrane Library (CENTRAL) from inception to 18 March 2022. RevMan 5.3 and CINeMA 2.0.0 were used to assess the risk of bias and confidence. Data analysis using STATA 17.0 and R 4.1.2. STATA 17.0 was used to calculate the surface under the cumulative ranking curve (SUCRA) and provide network plots with CINeMA 2.0.0. NMA was performed with R 4.1.2 software gemtc packages in RStudio. Main results: This NMA included 19 RCTs with 5,406 patients. In the pairwise meta-analysis results, only regional anesthesia (RA) with general anesthesia (GA) vs. GA (Log OR: -1.08; 95% CI: -1.54, -0.63) were statistically different in POD incidence. In the NMA results, there was no statistical difference between anesthesia methods, and psoas compartment block (PCB) with bupivacaine was superior to the desflurane, propofol, sevoflurane, and spinal anesthesia with bupivacaine of POD occurrence. Conclusion: Our study indicated that RA and GA had no significant effect on POD, and there was no difference between anesthesia methods. Pairwise meta-analysis showed that, except for RA with GA vs. GA, the rest of the results were not statistically different. Besides, PCB with bupivacaine may benefit to reduce POD incidence. Systematic review registration: https://www.crd.york.ac.uk/prospero/dis play_record.php?ID=CRD42022319499, identifier PROSPERO 2022 CRD42022319499.

A necroptosis-related prognostic model for predicting prognosis, immune landscape, and drug sensitivity in hepatocellular carcinoma based on single-cell sequencing analysis and weighted co-expression network.

Background: Hepatocellular carcinoma (HCC) is a highly lethal cancer and is the second leading cause of cancer-related deaths worldwide. Unlike apoptosis, necroptosis (NCPS) triggers an immune response by releasing damage-related molecular factors. However, the clinical prognostic features of necroptosis-associated genes in HCC are still not fully explored. Methods: We analyzed the single-cell datasets GSE125449 and GSE151530 from the GEO database and performed weighted co-expression network analysis on the TCGA data to identify the necroptosis genes. A prognostic model was built using COX and Lasso regression. In addition, we performed an analysis of survival, immunity microenvironment, and mutation. Furthermore, the hub genes and pathways associated with HCC were localized within the single-cell atlas. Results: Patients with HCC in the TCGA and ICGC cohorts were classified using a necroptosis-related model with significant differences in survival times between high- and low-NCPS groups (p < 0.05). High-NCPS patients expressed more immune checkpoint-related genes, suggesting immunotherapy and some chemotherapies might prove beneficial to them. In addition, a single-cell sequencing approach was conducted to investigate the expression of hub genes and associated signaling pathways in different cell types. Conclusion: Through the analysis of single-cell and bulk multi-omics sequencing data, we constructed a prognostic model related to necroptosis and explored the relationship between high- and low-NCPS groups and immune cell infiltration in HCC. This provides a new reference for further understanding the role of necroptosis in HCC.

High-flow nasal cannula versus noninvasive ventilation in patients with COVID-19: a systematic review and meta-analysis.

BACKGROUND: During the novel coronavirus disease 2019 (COVID-19) pandemic raging around the world, the effectiveness of respiratory support treatment has dominated people's field of vision. This study aimed to compare the effectiveness and value of high-flow nasal cannula (HFNC) with noninvasive ventilation (NIV) for COVID-19 patients. METHODS: A comprehensive systematic review via PubMed, Web of Science, Cochrane, Scopus, WHO database, China Biology Medicine Disc (SINOMED), and China National Knowledge Infrastructure (CNKI) databases was conducted, followed by meta-analysis. RevMan 5.4 was used to analyze the results and risk of bias. The primary outcome is the number of deaths at day 28. The secondary outcomes are the occurrence of invasive mechanical ventilation (IMV), the number of deaths (no time-limited), length of intensive care unit (ICU) and hospital stay, ventilator-free days, and oxygenation index [partial pressure of arterial oxygen (PaO2)/fraction of inhaled oxygen (FiO2)] at 24 h. RESULTS: In total, nine studies [one randomized controlled trial (RCT), seven retrospective studies, and one prospective study] totaling 1582 patients were enrolled in the meta-analysis. The results showed that the incidence of IMV, number of deaths (no time-limited), and length of ICU stay were not statistically significant in the HFNC group compared with the NIV group (ps = 0.71, 0.31, and 0.33, respectively). Whereas the HFNC group performed significant advantages in terms of the number of deaths at day 28, length of hospital stay and oxygenation index (p < 0.05). Only in the ventilator-free days did NIV show advantages over the HFNC group (p < 0.0001). CONCLUSION: For COVID-19 patients, the use of HFNC therapy is associated with the reduction of the number of deaths at day 28 and length of hospital stay, and can significantly improve oxygenation index (PaO2/FiO2) at 24 h. However, there was no favorable between the HFNC and NIV groups in the occurrence of IMV. NIV group was superior only in terms of ventilator-free days.

Prophylactic hyperthermic intraperitoneal chemotherapy may benefit the long-term survival of patients after radical gastric cancer surgery.

Hyperthermic intraperitoneal chemotherapy (HIPEC) has been proven to improve the survival rate of gastric cancer and reduce peritoneal recurrence. We aimed to evaluate the effectiveness and safety of prophylactic HIPEC after radical gastric cancer surgery in this study. Researchers searched for studies published in PubMed, Embase, Web of science, Scopus, Cochrane, Clinical key databases and Microsoft Academic databases to identify studies that examine the impact of prophylactic HIPEC on the survival, recurrence and adverse events of patients undergoing radical gastric cancer surgery. RevMan 5.3 was used to analyze the results and risk of bias. The PROSERO registration number is CRD42021262016. This meta-analysis included 22 studies with a total of 2097 patients, 12 of which are RCTs. The results showed that the 1-, 3- and 5-year overall survival rate was significantly favorable to HIPEC (OR 5.10, 2.07, 1.96 respectively). Compared with the control group, the overall recurrence rate and peritoneal recurrence rate of the HIPEC group were significantly lower (OR 0.41, 0.24 respectively). Significantly favorable to the control group in terms of renal dysfunction and pulmonary dysfunction complications (OR 2.44, 6.03 respectively). Regarding the causes of death due to postoperative recurrence: liver recurrence, lymph node and local recurrence and peritoneal recurrence, the overall effect is not significantly different (OR 0.81, 1.19, 0.37 respectively). 1-, 3- and 5-year overall survival follow-up may be incremented by the prophylactic HIPEC, and which reduce the overall recurrence rate and peritoneal recurrence rate. HIPEC may have high-risk of pulmonary dysfunction and renal dysfunction complications. No difference has been found in the deaths due to recurrence after surgery.

Is gabapentin effective and safe in the treatment of chronic pelvic pain in women: a systematic review and meta-analysis.

INTRODUCTION AND HYPOTHESIS: Chronic pelvic pain (CPP) affects 2.1-24% of women, causing physical and psychological damage to women around the world. Based on the efficacy of gabapentin in the treatment of chronic pain, we conducted this study to evaluate the efficacy and safety of gabapentin in reducing pain in women with CPP. METHODS: Systematic searches were performed in the electronic databases of PubMed, Embase, Web of Science, Scopus, Cochrane, and Clinicalkey databases. Studies focused on comparing the efficacy of gabapentin and placebo in the treatment of female CPP patients were included. RevMan 5.4 was used to analyze the results and risk of bias. Two investigators independently selected eligible studies and extracted related pain scores and side effects for meta-analysis. RESULTS: In total, 4 RCTs were enrolled in the meta-analysis, totaling 425 patients. Among patients receiving gabapentin, the average pain scores in 3 and 6 months were significantly lower than those in the placebo group(p < 0.00001). The results showed that there was no statistical difference between gabapentin and placebo in the reduction of pain scores from baseline(p = 0.41). The incidence of side effects in the gabapentin group was significantly higher than that in the placebo group (p < 0.00001). CONCLUSION: This systematic review and meta-analysis demonstrated that for women with CPP, gabapentin was significantly different from placebo in average pain scores at 3 and 6 months. However, the two drugs did not differ in the reduction in pain scores from baseline. Gabapentin can bring more significant side effects, whether they are common side effects or serious side effects.

Polysaccharides from Ganoderma Sinense - rice bran fermentation products and their anti-tumor activities on non-small-cell lung cancer.

BACKGROUND: Non-small-cell lung cancer (NSCLC) accounts more than 80% of the lung cancer cases. Polysaccharides in rice bran and its fermentation products have been proven to suppress many cancers. However, the report on inhibiting NSCLC is few. In this paper, the polysaccharides with suppression activity to H1299 NSCLC in the fermentation products of full-fat rice bran and defatted rice bran were studied in vitro and in vivo. METHOD: Polysaccharides (GSRBPs) were extracted from Ganoderma sinense - full-fat rice bran (GS-FRB) and Ganoderma sinense - defatted rice bran (GS-DRB) fermentation products. The structure information of the GSRBPs was studied using HPLC analysis. The anti-tumor activities on H1299 NSCLC of GSRBPs in vitro study was performed using MTT method. The in vivo studies use BALB/c-nu nude mice as H1299 NSCLC bearing mice. RESULT: All the polysaccharides contained two fractions, GSFPS-1 and GSFPS-2. The molecular weight and the ratio of GSFPS-1 and GSFPS-2 were different in GS-FRB and GS-DRB. At the earlier state of fermentation, all polysaccharides were composed of D-glu, D-man, D-xyl and L-ara with certain molar ratios. But at the latter stage, polysaccharides in GS-FRB were composed of D-glu, D-man, D-xyl, L-ara and D-fru, while these in GS-DRB only composed of D-glu and D-man. In the in vitro study, the IC50 of RBS and GSRBPs was as GS-DRB-11 (40.62 µg/mL), GS-FRB-9 (43.82 µg/mL), GS-DRB-7 (48.08 µg/mL), RBS (49.56 µg/mL), GS-DRB-9 (49.91 µg/mL), GS-DRB-13 (51.89 µg/mL), GS-FRB-11 (53.75 µg/mL), GS-FRB-7 (56.84 µg/mL), GS-DRB-13 (60.63 µg/mL) from small to large. In the in vivo study, the H1299 NSCLC inhibition rate (InRa) of RBS and GSRBPs were GS-DRB-11 (86.81%) > GS-DRB-9 (86.01%) > GS-FRB-9 (84.88%) > GS-DRB-7 (82.21%) > GS-DRB-13 (78.04%) > RBS (76.06%) > GS-FRB-13 (65.44%) > GS-FRB-11 (64.70%) > GS-FRB-7 (27.87%). The GSFPS-2 area percent was negatively correlated to the IC50 and was positively correlated to the InRa. This means the GSFPS-2 had much higher anti-tumor activity than GSFPS-1. CONCLUSION: GSFPS-2 had higher anti-tumor activities, and the lipid in the rice bran has a decisive effect on the structures of polysaccharides produced by fermentation. Therefore, GSRBPs could be considered as potential novel agents to suppress H1299 non-small-cell lung cancer.

Pharmacokinetics of S-EPA, and its inhibition on indoleamine 2,3-dioxgenase: a case of sulfur-substitution affecting distributions in blood cells.

1. S-EPA is a sulfur-substitution analog of epacadostat (EPA), an effective small molecule indoleamine 2,3-dioxgenase1 (IDO) inhibitor. By in vitro and in vivo experiments, pharmacokinetic differences of two closely related analogs, S-EPA and EPA was investigated in this study. 2. Liver microsomes clearance experiments showed S-EPA had comparable metabolic stability with EPA in rat and human liver microsomes. The whole blood distribution experiments showed the distribution ratio of S-EPA in blood cells to plasma in mice, rats, dogs and monkey was 1.2, 4.8, 2.2 and 40.6, respectively. While the distribution ratio of EPA ranged from 0.94 to 1.30 in mice, rats, dogs and was 3.1 in monkeys. 3. The pharmacokinetic study in rats showed the exposure (AUClast) of S-EPA in plasma and blood cells was 1.7-fold and 3.9-fold higher than that of EPA, respectively. Moreover, the exposure ratio of S-EPA in blood cells to plasma was 3.7, while the ratio of EPA was 1.6. 4. In CT26 tumor bearing mice, the IDO inhibition of S-EPA and EPA on plasma or tumor kynurenine was generally consistent. And the inhibition ratio could reach at more than 50% at 3 h after single dose, at least lasting up to 8 h.

Determination of kynurnine and tryptophan, biomarkers of indoleamine 2,3-dioxygenase by LC-MS/MS in plasma and tumor.

AIM: Tryptophan (Trp) and kynurnine (Kyn) are a pair of biomarkers for indoleamine 2,3-dioxygenase which closely related to the tumor immune escape. To evaluate the effect of drugs on the indoleamine 2,3-dioxygenase activity, the specific and accurate LC-MS/MS methods were developed and validated for simultaneous determination Kyn and Trp in mouse plasma and tumor tissues using surrogate analytes Kyn-d4 and Trp-d5 calibrators. RESULTS: Plasma and tumor homogenates samples were pretreated with the solid phase extraction which assured the method having high recovery (>90% in plasma and >80% in tumor) and no matrix effect. The methods were validated for specificity, linearity, accuracy and precision, recovery, matrix effect and stability using surrogate analytes Kyn-d4 and Trp-d5 in authentic matrices. CONCLUSION: The validated methods have been successfully applied to the pharmacodynamic study of INCB024360 in CT26 tumor bearing mice after single dose and multiple dosing.

Enzymatic Modification of Rice Bran Polysaccharides by Enzymes from Grifola Frondosa: Natural Killer Cell Cytotoxicity and Antioxidant Activity.

Rice bran polysaccharides (RBPSs) are the major active constituents of rice bran (RB). In this study, we utilized intracellular enzymes from Grifola frondosa to modify RBPSs, which were extracted from RB using ultrasound. To enhance the effect on natural killer (NK) cell cytotoxicity of modified polysaccharides (mRBPSs) generated from RBPSs, an orthogonal test (L9 [3]4 ) was employed to optimize the modification conditions. Based on the results of a single-factor test, the enzyme to polysaccharide ratio, reaction temperature, reaction pH, and reaction time were the main factors affecting mRBPSs-enhanced NK-cell cytotoxicity. The best conditions were determined to be an enzyme to polysaccharide ratio of 1:5, a reaction temperature of 40 °C, a reaction pH of 4, and a reaction time of 4 hr. By optimizing the conditions, the NK-cell cytotoxicity induced by mRBPSs6 was the highest, increasing by 12.01% ± 0.08%. Gas chromatographic analysis revealed that mRBPSs6 consists of rhamnose, arabinose, xylose, mannose, glucose, and galactose at a molar ratio of 7:21:6:5:53:48, which was 8:13:8:5:44:44 before modification. High-performance liquid chromatography results indicated molecular weights for the RBPSs of approximately 106 Da, which decreased to 104 to 105 Da after modification. Antioxidant activity tests revealed high capacity of mRBPSs6 for scavenging 1,1-diphenyl-2-picrylhydrazyl radicals and hydroxyl free radicals at 1.0 mg/mL. PRACTICAL APPLICATION: Rice bran polysaccharides (RBPSs) contain compounds with many biological activities. However, these polysaccharides difficult to absorb due to high molecular weights and unexposed active sites, which are the main factors that limit their use in functional foods. The results of this study demonstrate that modification of RBPSs using intracellular enzymes from an edible fungus alters the molecular weights and monosaccharide composition of RBPSs. In addition, immune and antioxidant activities of RBPSs were increased. The findings provide a new and beneficial application for rice bran.

Improvement of Spinosad Production upon Utilization of Oils and Manipulation of ß-Oxidation in a High-Producing Saccharopolyspora spinosa Strain.

Spinosad, a member of polyketide-derived macrolides produced in the actinomycete Saccharopolyspora spinosa, has been developed as a broad-spectrum and effective insecticide. The ß-oxidation pathway could be an important source of building blocks for the biosynthesis of spinosad, thus the effect of vegetable oils on the production of spinosad in a high-yield strain was investigated. The spinosad production increased significantly with the addition of strawberry seed oil (511.64 mg/L) and camellia oil (520.07 mg/L) compared to the control group without oil (285.76 mg/L) and soybean oil group (398.11 mg/L). It also revealed that the addition of oils would affect the expression of genes involved in fatty acid metabolism, precursor supply, and oxidative stress. The genetically engineered strain, in which fadD1 and fadE genes of Streptomyces coelicolor were inserted, produced spinosad up to 784.72 mg/L in the medium containing camellia oil, while a higher spinosad production level (843.40 mg/L) was detected with the addition of 0.01 mM of thiourea.

Rice bran polysaccharides and oligosaccharides modified by Grifola frondosa fermentation: Antioxidant activities and effects on the production of NO.

Rice bran polysaccharides (RBPSs) are valuable compounds with many biological activities. In this work, a fungus called Grifola frondosa, was selected to ferment defatted rice bran water extracts and modify the RBPSs, which were then isolated by ethanol precipitation and deproteinization. GC analysis of fermented products suggested they are composed of glucose, arabinose, galactose, mannose, and xylose at a molar ratio of 9:5:8:2:5, which was 32:4:6:2:5 before fermentation. HPLC analysis revealed that the molecular weight of unfermented RBPS was distributed mainly from 103 to 104Da, and it changed to 102 to 103Da after fermentation. Antioxidant activities and effects on the production of NO were analyzed and it indicated that the scavenging ratios of hydroxyl and DPPH radicals by the fermented products were significantly enhanced compared to the unfermented ones, and also the products fermented for 9days exhibited two-way adjusting effects on the production of NO in macrophages.

Antiaromatic characteristic analysis of 1,4-diazapentalene derivatives: a theoretical study.

1,4-Diazapentalene heteroacenes are potential n-type semiconductors that could be used as a new type of material for organic field-effect transistors (OFETs), but their synthesis is still challenging due to their antiaromaticity. The study on their structure-stability relationship should provide useful guidance to the design of stable diazapentalenes. We examined the stability of several types of heteroacenes bearing the 1,4-diazapentalene core using NICS(1)zz calculations. The influence of the fusion pattern, the introduction of substituents, and the incorporation of other heterocycles on the antiaromaticity of the central 1,4-diazapentalene core was systematically studied. It was found that the linear fusion of aromatic rings to the antiaromatic core increases the stability of the heteroacene. The fusion of electron-poor heterocyclic rings also enhances the stability effectively, whereas the fusion of electron-rich heterocyclic rings destabilizes the system. In addition, the combination of the linear fusion pattern or introduction of electron-poor heterocyclic rings to the antiaromatic core reduces the reorganization energy for electron transport, suggesting a way to achieve better n-type semiconductors.

Reductive ring closure methodology toward heteroacenes bearing a dihydropyrrolo[3,2-b]pyrrole core: scope and limitation.

A newly developed reductive ring closure methodology to heteroacenes bearing a dihydropyrrolo[3,2-b]pyrrole core was systematically studied for its scope and limitation. The methodology involves (i) the cyclization of an o-aminobenzoic acid ester derivative to give an eight-membered cyclic dilactam, and (ii) the conversion of the dilactams into the corresponding diimidoyl chloride, which undergoes (iii) reductive ring closure to install the dihydropyrrolo[3,2-b]pyrrole core. The first step of the methodology plays the key role due to its substrate limitation, which suffers from the competition of oligomerization and hydrolysis. All the dilactams could successfully convert to the corresponding diimidoyl chlorides, most of which succeeded to give the dihydropyrrolo[3,2-b]pyrrole core. The influence of the substituents and the elongation of conjugated length on the photophysical properties of the obtained heteroacenes were then investigated systematically using UV-vis spectroscopy and cyclic voltammetry. It was found that chlorination and fluorination had quite a different effect on the photophysical properties of the heteroacene, and the ring fusing pattern also had a drastic influence on the band gap of the heteroacene. The successful preparation of a series of heteroacenes bearing a dihydropyrrolo[3,2-b]pyrrole core would provide a wide variety of candidates for further fabrication of organic field-effect transistor devices.

Benzo[f]benzo[5,6]indolo[3,2-b]indole: a stable unsubstituted 4nπ-electron acene with an antiaromatic 1,4-diazapentalene core.

A stable unsubstituted 4nπ-electron acene with an antiaromatic 1,4-diazapentalene core was prepared via an unprecedented mild oxidation. Further investigation showed that the stability of such acenes was dependent on the fusion patterns of the peripheryl benzene rings to the centre core.

Tracking of the molecular motion in the primary event of photoinduced reactions of a phytochromobilin model.

The photoinduced processes of phytochromes have received great research interest for their important biological functions. Phytochromobilin (PΦB), one of the most important phytochrome chromophores, was selected as the prototype to study its photoinduced isomerization. The nonadiabatic dynamics of PΦB from the Pr configuration in the gas phase was investigated by the surface hopping method at the OM2/MRCI level. In the excited state, isolated PΦB does not display the rotation of the two terminal five-membered rings (ring A and ring D), which is assumed to govern the Pr → Pfr process in the protein. Instead, two S1/S0 conical intersection seams (CI01α and CI01ß) characterized by the rotation of the two central rings (ring B and ring C) were proven to play essential roles for the photoisomerization of PΦB in the gas phase. These two conical intersections (CI01α and CI01ß) are accessible by the twisting motions of the C9-C10 and C10-C11 bonds, respectively. The CI01α and CI01ß seams, instead of their minimum-energy points, are responsible for the nonadiabatic dynamics. For both channels, the trajectories may propagate forward to the isomerization products or backward to the original Pr configuration after the S1 → S0 hops.

Photoinduced nonadiabatic decay and dissociation dynamics of dimethylnitramine.

Dimethylnitramine (DMNA) is a prototype system used in the investigation of the unimolecular decomposition mechanism of the nitramine-compound family. The photoinduced excited-state nonadiabatic processes and successive unimolecular dissociation of DMNA were investigated by trajectory surface-hopping dynamics at the semiempirical OM2/MRCI level. Two S1/S0 conical intersections (CI01α and CI01ß) were found to play essential roles in the nonadiabatic decay dynamics of DMNA. After the S1 → S0 decay, the excess kinetic energy finally results in the cleavage of the N-N bond in the ground electronic state. The two reaction channels through CI01α and CI01ß show differences in molecular motions and decay features. The trajectories passing CI01α can hop one or several times, and the intramolecular vibrational energy transfer in the ground state takes place before dissociation, whereas trajectories following the CI01ß channel mainly dissociate directly after only one S1 → S0 hop.