Tryptophan (Trp) is an essential amino acid obtained from human diet. It is involved not only in de novo biosynthesis of proteins but also in complex metabolic pathways. Redox transformation of tryptophan is under-explored in comparison with kynurenine, serotonin and indole pyruvate pathways. We described herein a mass spectrometric approach that can not only detect electron transfer-associated changes in masses and charges, but also identify electron-directed bond cleavages and radical-radical cross-coupling reactions in redox transformation of tryptophan. Photoactive TiO2 that is widely applied in cosmetic products is used as electron donor and receptor because of the capability to generate photoelectrons and holes. It was demonstrated tryptophan undergoes redox transformation through the removal of an electron from amino nitrogen atom by hole oxidization along with an electron capture in the indole ring. The back and forth electron-shuttle converts electric energy into chemical energy that enforces bond cleavages. Sodium-coupled electron transfer (SCET) was found in complementary with proton-coupled electron transfer in tryptophan. The movement of sodium ions avoids electric charge buildup caused by electron transfer. Various redox products were detected on both light irradiated TiO2 and skins, among which β-carboline shows extensive radical scavenging ability for diverse cross-coupling with indole derivatives. Light-independent redox products have been detected in vivo such as in mouse brain, indicating the presence of in vivo electron transfer-directed redox transformation. It has also been revealed that tryptophan can be arylated on Cα and Cβ atoms in response to the exposure of halogenated aromatics.

The light induced hot-electron on plasmonic nanostructures has been recognized as a breakthrough discovery for photovoltaic and photocatalytic applications. With mass spectrometry, we demonstrate the dynamics of hot electron transfers of anaerobic oxidization reactions on Au decorated TiO2 plasmonic nanoparticles, which were coated on the inner surface of a flask. Those nanoparticles were covered by continuously renewed liquid droplets of solvent and reactants that were transported through a Venturi jet mixer with auto-spray. In addition to intensive mass transfer in such droplet-based nanoreactors, as well as strong adsorption of reactants and rapid desorption of products on materials surfaces, the localized surface plasmon resonance (LSPR) excitation upon visible light illumination, by which accumulated energies of plasmons are transferred to electrons in the conduction band of the material, attributes to the efficient photocatalytic transformation. Mass spectrometric detection of intermediate radical anions and negative ions with stable isotope labeling unambiguously identifies that highly energetic hot electrons can escape from the plasmonic nanostructures, be collected by adsorbed molecules, and initiate bond cleavages. It was demonstrated that losses of two H atoms result in the anaerobic oxidization of each benzyl alcohol molecule to a benzyl aldehyde molecule in the absence of molecular oxygen with more than 90 % yields. The well recyclable plasmonic nanoreactors implicate the injection of transferred electrons eventually back to electronically depleted Au+ positive ions. Bridged by adsorbed molecules, electrons were repeatedly circulated back and forth in plasmonic nanoreactors, where the collected light was eventually converted into chemical energy.

A substrate with n phosphorylated sites may have 2n phosphor-forms for temporal-spatial regulation of biological events. Because phosphates do not significantly change molecular masses but net charges of proteins, those isoforms cannot be separated by regular mass-based sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE). A tandem polymerized gel was developed to resolve phosphor-isoforms with different masses, charges, and posttranslational modifications. Without the usage of SDS, the electrophoresis was primarily performed on three adjacent acidic polyacrylamide gels. After being concentrated on a stacking gel, protonated proteins were then separated on the Zr4+ immobilized gel through the coordination of metal ions with phosphates followed by further charge and mass (z/m)-based electrophoretic separation on a TiO2 containing gel. The presence of TiO2 nanoparticles in the third gel is aimed for the initiation of the polymerization of acrylamide in acidic conditions upon ultraviolet irradiation. Distinct isoforms of α-S1-casein, α-S2-casein, β-casein, and κ casein model proteins located on 11, 8, 8, and 7 different bands of the tandem gel were unambiguously identified, respectively. With the tandem polymerized gel electrophoresis, new phosphorylation events that may occur simultaneously or sequentially were discovered in not only model proteins but also complex biological samples including human saliva, chicken egg, and sprouting maize. This provides a new tool to dissect complex biological processes that are triggered by dynamic phosphorylation events.

Protonation/deprotonation is the well-recognized mass spectrometric mechanism in matrix-assisted laser desorption ionization of organic molecules but not for metal ions with different oxidation states. We describe herein a soft evaporation and ionization technique for metal ions based on iodination/de-iodination in metal-iodide cluster ionization (MICI). It is not only able to determine identities and oxidation states of metal ions but also reveal spatial distributions and isotope ratios in response to physiological or environmental changes. A long chain alcohol 1-tetradecanol with no functional groups that can absorb laser irradiation was used to cover and prevent samples from direct laser ablation. Upon the irradiation of the third harmonic Nd3+:YAG (355 nm, 3 ns), iohexol containing three covalently bonded iodine atoms instantly generates negative iodide ions that can quantitatively form clusters with at least 14 essential metal ions present in plants. The detection limits vary with different metal ions down to low fmol. MICI eliminates the atomization process that obscures metal charges in inductively coupled plasma mass spectrometry. Because only metal ions can be iodinated with iohexol, interferences from the abundant organic molecules of plants that are confronted by secondary ion mass spectrometry (SIMS) are also greatly decreased.

A protonation/deprotonation mechanism has been established for the interpretation of ions in MALDI. We show herein that negative ions can be generated in different ways. Molecules with different electron affinities have been spotted on surfaces of TiO2, ZnO, and a stainless steel plate for the investigation of electron capture dissociation in comparison with photo- or thermal-induced deprotonation upon irradiation of the third harmonic of Nd3+:YAG (355 nm) laser pulses. Detection of C60•- and Fe (II) (porph•-) radical anions unambiguously demonstrates the electron-transfer process and the exothermic capture of electrons. Radical anions of fatty acids were difficult to observe because of electron-directed ultrafast homolytic cleavage of O-H bonds unless there is a conjugated system as that in C60 and porphyrin for the delocalization and stabilization of acquired changes. The surface basicity of substrate materials was found to determine the competition of the electron-capture dissociation with deprotonation processes. Multiple electron transfers to pyrrole, -COOH, and Fe2+ of the heme were observed on TiO2 and the stainless steel plate but not on ZnO. When the heme was deprotonated by proton sponge 1,8-bis(dimethylamino)naphthalene, the occurrence of electron transfer on TiO2 was also not observed. It is proposed that negative charges of deprotonated ions prevent electron transfer due to the repulsive force. When both deprotonation and electron transfer are inhibited, adsorbed fatty acids on TiO2 undergo dehydration reactions to form titanium esters. In contrast, ZnO generates gaseous micelles composed of positive metal ions and negative fatty acid ions through either deprotonation or electron-capture dissociation.

OBJECTIVE:To explore the specific mechanism of sevoflurane in alleviating cerebral ischemia-reperfusion injury (CIRI) in rats through the c-Jun N-terminal kinase (JNK) signaling pathway.MATERIALS AND METHODS:A total of 60 male specific pathogen-free Sprague-Dawley rats were randomly divided into sham group (n=20), model group (n=20), and sevoflurane group (n=20). In the sevoflurane group, sevoflurane (2.5%) was inhaled for 60 min at 24 h before the blockage of cerebral blood supply. The CIRI model was established using the suture method in the model group and sevoflurane group, while the right common carotid artery and external carotid artery were separated and ligated only, without suture placement, in the sham group. At 24 h after reperfusion, the neurological deficit score in each group was calculated, the water content in brain tissues in each group was detected based on dry-wet weight ratio, the infarction volume of brain tissues in each group was detected via 2,3,5-triphenyltetrazolium chloride (TTC) staining, and the apoptosis rate of brain cells in each group was detected using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. Moreover, the protein levels of JNK, p-JNK, B-cell lymphoma-2 (Bcl-2), and the Bcl-2 associated X protein (Bax) in brain tissues were determined using Western blotting, and the gene expressions of Bax and Bcl-2 in brain tissues were determined through fluorescence quantitative Polymerase Chain Reaction (qPCR).RESULTS:It was found that the water content in brain tissues and the cerebral infarction volume were significantly increased in the model group compared with those in the sham group (p<0.01, p<0.01), while they were notably decreased in the sevoflurane group compared with those in the model group (p<0.05, p<0.01). The neurological deficit score was significantly higher in the model group than that in the sham group (p<0.01), while it was remarkably lower in the sevoflurane group than that in the model group (p<0.01). According to the results of the TUNEL assay, the model group had an evidently higher apoptosis rate of brain cells than the sham group (p<0.01), while the sevoflurane group had a lower apoptosis rate of brain cells than the model group (p<0.05). Besides, the results of Western blotting revealed that the model group exhibited remarkably increased protein levels of JNK, p-JNK, and Bax (p<0.05, p<0.01, p<0.01) and a remarkably decreased protein level of Bcl-2 (p<0.01) compared with the sham group. Sevoflurane group had decreased protein levels of JNK, p-JNK, and Bax (p<0.05, p<0.01, p<0.01) and an increased protein level of Bcl-2 (p<0.05) in comparison with the model group. In addition, the gene expression of Bcl-2 significantly declined (p<0.01), and that of Bax remarkably rose (p<0.01) in the model group compared with those in the sham group, while the contrary is the case in the sevoflurane group compared with those in the model group (p<0.05, p<0.01).CONCLUSIONS:Sevoflurane can regulate the protein and gene expressions of Bax and Bcl-2 and reduce apoptosis in CIRI by regulating the JNK signaling pathway, thereby exerting a protective effect on brain tissues and improving the symptoms of neurological deficit.

Electron transfer crucial to bioenergetics is ubiquitously present in biological systemsbut most of them escape from direct observations. By using tryptophan and itsderivatives with 1-CH3, 2-CH3, 5-CH3 and 5-OH substitutions as model molecules,we have unambiguously demonstrated successive two-electron transfer to tryptophanas well as electronic and vibrational excited molecular dissociation with massspectrometry. The ultra-short time delay between two electrons down tosub-attosecond over a distance less than 10 Å was found to cause the strong couplingof electronic and vibrational excitations that was validated by the observation ofradical-radical coupling. Intramolecular H migrations along with two-electrontransfer was demonstrated with H/D exchange and 13C stable isotope labeling. Thisproposed technique allows us to observe the ultrafast electron transfer fromtryptophan to the heme group in myoglobin proteins. It bridges electron transfer toenergy transfer that has been revealed in FRET alone. FeII (porph•‐) and FeI(porph•‐)resulting from one- and two-electron transfer, respectively, have been unambiguouslyidentified

Development of analytical techniques that can monitor the adsorption, transfer and in-situ distribution of environmental pollutants in agricultural products is essential to ensure the implementation of stringent food safety standards for consumer protection. A mass spectrometric imaging approach is described herein to investigate the dynamic changes and spatial distributions of 4, 4'-DDT (dichlorodiphenyltri-chloroethane) in soybean seeds and sprouts during the growth. Soy beans seeds incubated in DDT containing water were sliced in every 20 mu m and directly blotted on the surface of a compressed thin film of (Bi2O3)(0.07)(CoO)(0.03)(ZnO)(0.9) nanoparticles. Endogenous molecules and exogenous DDT compounds in soy bean seeds were ionized and dissociated by photoelectrons that are generated on surfaces of semiconductor nanoparticles upon the irradiation of the 3rd harmonic (355 nm) of Nd3+:YAG laser. Structural identification is achieved by the interpretation of fragment ions resulting from electron-initiated specific bond cleavages or hole oxidization. Mass spectrometric images reveal increased quantities of DDT residues in soy bean seeds and sprouts during the growth. It provides an in situ way without extensive sample preparation to monitor the transfer and distribution of exogenous pollutants as well as the possible impacts on plant growth. (C) 2020 Elsevier B.V. All rights reserved.

OBJECTIVETo observe the expressions of Linc-ROR and proteins in the PI3K-Akt pathway in an ectopic lesion of adenomyosis.PATIENTS AND METHODSThe expression of Linc-ROR in the ectopic endometrium, eutopic endometrium, and normal endometrium of adenomyosis was detected by qRT-PCR. Western blot was used to detect the protein expressions of PI3K-Akt in endometriosis and lesion endometriosis. Cell counting kit-8 (CCK-8) assay was utilized to detect cell proliferative activity. After interfering or overexpressing Linc-ROR, protein expressions of the PI3K-Akt pathway were detected by Western blot.RESULTSLinc-ROR expression in the ectopic endometrium of adenomyosis was higher than that in the eutopic endometrium and normal endometrium, and the expression level of PTEN in adenomyosis tissues was decreased, whilst expression levels of Akt, p-Akt, p-PTEN were increased. Clinical data of enrolled patients indicated that there was a relationship between Linc-ROR expression and the type and severity of dysmenorrhea of adenomyosis. However, no relationship was observed between Linc-ROR expression and age, cesarean section, uterine surgery, and menstrual cycle. Cell counting kit-8 (CCK-8) assay showed that the proliferative activity of cells was significantly decreased after knockdown of Linc-ROR in the adenomyosis cells. Western blot revealed that the expression level of PTEN increased but the expression levels of p-Akt, p-PTEN and p-PDK1 decreased. Overexpression of Linc-ROR obtained the opposite results.CONCLUSIONSLinc-ROR is highly expressed in the ectopic endometrium of adenomyosis, and it can promote the proliferative activity of endometrial cells by activating the PI3K-Akt pathway.

Organochlorines are highly persistent and toxic contaminants that are widely distributed and accumulated in various aquatic or soil environments as well as food chains. Heterogeneous photocatalytic degradation of such pollutants by using semiconductor nanoparticles has been recognized as one of the effective purification ways. Understanding of degradation mechanisms and designing of highly efficient semiconductor nanoparticles require structural identification of various degradation intermediates that are difficult to achieve with current spectroscopic techniques. Herein a mass spectrometric approach was developed to tackle interfacial photoelectron transfer and hydroxyl radical abstraction on different semiconductor nanoparticles. Chlorobenzenes (including hexachlorobenzene and chlorothalonil) adsorbed on the surfaces of nanoparticles were found to instantly undergo dechlorination and ring dissociation through photoelectron capture dissociation and abstraction of a chlorine atom from aromatic C-Cl bond by hydroxyl radicals. Different intermediates have been unambiguously identified with experimental evidences provided by a Q-TOF mass spectrometer. It has been demonstrated that both electron density around atoms and steric effects of side chains contribute to the site selectivity for photoelectron capture and hydroxyl radical abstraction. But the energies needed for chemical bond cleavages and the stabilization of acquired charges play important roles in degradation efficiency. By using mass spectrometric imaging, photocatalytic differences of different semiconductor nanoparticles have been revealed.

Structural identification is challenging in mass spectrometric imaging because of inadequate sample quantities and limited sampling time in each pixel for tandem mass spectrometry (MS/MS) experiments, which are usually used for the generation of fragment ions. We report herein the observation of a cascade of highly specific chemical bond cleavages via a low-energy photoelectron activated radical relays and a competed hole oxidization on surfaces of (Bi2O3)0.07(CoO)0.03(ZnO)0.9 semiconductor nanoparticles irradiated with the 3rd harmonic (355 nm) of the Nd3+: YAG laser. Distinguished from high energy electron impact (EI), this approach generates gaseous radical anions through the exothermic capture of low-energy tunneling electrons that are not able to cause extensive vibrational excitations. It was found not only original radical center but also secondary or even tertiary radical centers cause specific bond cleavages exclusively on α positions. The original radical center directly activates the cleavages of α-positioned chemical bonds that cause the formation of secondary radical centers. Ion fragmentations proceed along the newly formed radical centers that further activate the cleavages of their α-positioned chemical bonds. Using 8 compounds, we have demonstrated various radical reactions involved in desulfonation, cyclization, and ring contraction reactions as well as competed hole oxidization-generated hydroxyl radical substitution reactions. The interpretable fragment ions provide unambiguous experimental evidences for structural elucidation of drug residues and metabolites in mass spectrometric imaging of tissue slices without tandem mass spectrometry (MS/MS).

Dysfunctional glutamate receptors (GluRs) have been implicated in neurological disorders and injuries. Hetero-tetrameric assemblies of different GluR subunits or splicing variants have distinct spatiotemporal expression patterns and pharmacological properties. Mass spectrometric imaging of GluRs-targeted small molecules is important for determining the regional preferences of these compounds. We report herein the development of a mass tag covalently bonded with glutamate or N-methyl-d-aspartate that functions as both an electron acceptor to generate mass spectrometric signals on irradiated (Bi2O3)0.07(CoO)0.03(ZnO)0.9 nanoparticles with the third harmonic (355 nm) of Nd3+:YAG laser and as the core component to target bilobed clamshell-like structures of GluRs. In this approach, different molecules produce the same tag ion. It provides a new avenue for quantitative assessment of spatial densities of different compounds, which cannot be achieved with well-established stable isotope labeling technique due to different ionization efficiency of different compounds. Various coexisting endogenous molecules are also simultaneously detected for investigation of overall physiological changes induced by these compounds. Because semiconductors do not generate background peaks, this method eliminates interferences from organic matrix materials that are used in regular MALDI (matrix assisted laser desorption ionization). The localized ionization provides high spatial resolution that can be down to sub-micrometers.

This study investigated cadherin-1 (Cdh1) expression in the sensorimotor cortex of rats after spinal cord injury (SCI). The repairing effect of Cdh1 was evaluated by silencing its expression with lentivirus-mediated RNAi. Twenty male Sprague-Dawley (SD) rats were randomly divided into a normal group and an operation group. Rats of the operation group were given SCI by the Allen method (T10-T11). Cdh1 expression in the sensorimotor cortex was examined by quantitative real-time polymerase chain reaction (PCR) and Western blot analysis. Thirty male SD rats were divided into a sham-operation (SO) group, a lentivirus vector (LV) group, and a recombinant lentivirus (RL) group. Rat behavior was evaluated using the Basso-Beattie-Bresnahan (BBB) test every week. Ten days after injection, Cdh1 expression was examined by quantitative real-time PCR and Western blot. Six weeks after injury, animals were injected with biotinylated dextran amine-Texas Red (BDA-TR), and then at 8 weeks, spinal cords were removed and sectioned in serial order. The expression of Cdh1 mRNA was significantly higher in the operation than in the normal group (P < 0.05). The expression of Cdh1 mRNA was lower in the RL than in the SO or LV groups at 10 days after injection (P < 0.05). In addition, the BBB score was higher for the RL than for the SO or LV groups at 6 weeks after injury (P < 0.05). A novel population of BDA-labeled axons was observed extending past the lesion in the RL group, which was rarely observed in the SO and LV groups. These results suggest that the anaphase-promoting complex-Cdh1 may play an important role in inhibiting axonal growth.

Option contract with two parameters is studied in a supply chain with a supplier and a retailer. The coordination mechanisms under symmetric information and asymmetric information are investigated respectively. With the symmetric information, the leader retailer can get the channel coordination by setting appropriate contract parameters. Under asymmetric information, we analyze how the supply chain operates with option contract under a uniformly distribution demand. The coordination mechanism with a continuum of the cost type is investigated. The results indicates that optimal supply chain performance requires the retailer to offer a mechanism of option pricing, a function of the declared cost of the supplier, which makes supplier maximize his profit only by reporting his true cost.

New highly fluorinated poly(arylene ether sulfone)s (FPAES), poly(arylene ether ketone)s (FPAEK), and poly(arylene ether)s with several types of NLO chromophores as pendant groups were obtained by a polycondensation reaction using very mild conditions. The different polymer structures were designed with the objective to investigate the influence of both the polarity of the chromophore and the nature of the tether between the NLO chromophore and the chain. The resulting copolymers have glass transition temperatures (T-g's) varying between 160 and 215 degrees C, and they are stable up to 280 degrees C under nitrogen. Although these copolymers are Soluble in common organic solvents, cyclohexanone gave the best film quality and was used for the film preparation. After optimization of the poling conditions, the in situ second harmonic generation (SHG) measurements gave nonresonant Values of the second-order susceptibilities d(33) ranging from 2 to 8 pm/V, and the SHG signals of the poled polymer films were found to be thermally stable below 130 degrees C. Although being comparable with the values obtained for similar polymers and chromophores in the literature, d(33) are smaller than those obtained for more conventional NLO polymers like PMMA-Disperse Red One (PMMA-DR1), which was taken as a reference. An unusual drop of the SHG signal during cooling was found in the thermally assisted orientation process. This drop occurred at a characteristic temperature below T-g. In this relaxation process which has never been observed, intra- and interchain dipolar interactions are shown to play,in important role, which is amplified in the case of chromophores which have their donor group embedded in the main chain, connected by two rigid tethers.

A series of highly fluorinated poly(arylene alkylene ether)s, P6C(F)Xs (X = Non, S, K, SO, Ox) have been prepared by polycondensation reactions of 1H,1H,6H,6H,-perfluorohexane-1,6-diol (6C(F)-diol) with a series of decafluorodiphenyl compounds (DFPXs) including decafluorobiphenyl (DFP), decafluorodiphenyl sulfide (DFPS), decafluorobenzophenone (DFPK), decafluorodiphenyl sulfone (DFPSO), and decafluorodiphenyl oxadiazole (DFPOx). This aromatic nucleophilic substitution polycondensation can be effectively activated by cesium fluoride (CsF) and was completed in a few hours in N,N-dimethylacetamide (DMAc) at room temperature. High molecular weight polymers (M-n = 28 200-64 200 Da) have been prepared from DFP, DFPS, DFPSO, and DFPOx, while the reaction from DFPK only yields low-molecular weight materials (M-n < 8 000 Da). A model reaction using excess 6C(F)-diol (2.5 equiv of DFPK) reveals that the ketone linkage of the DFPK unit is cleaved by the attack of the activated hydroxyl group in the diol during the polycondensation. This cleavage is suppressed when potassium fluoride (KF) was used as a base, and a high molecular weight P6C(F)K (M-n = 33 200 Da) has been prepared. DSC analysis shows that all the resultant polymers are semicrystalline materials, and the melted samples display different crystallization rates in the order of P6C(F)Non > P6C(F)Ox > P6C(F)K > P6C(F)SO similar to P6C(F)S. This sequence is correlated with the bond angles of the X linkages, suggesting a significant influence of the bending of the X linkages on the crystallization capability of the polymers. The P6C(F)Non film has a hydrophobic surface with a water contact angle of 110 degrees, while the other polymers showed reduced values with the increase of the polarities of the X linkages in the order of P6C(F)Non > P6C(F)S > P6C(F)K > P6C(F)Ox > P6C(F)SO.

New fluorinated poly(arylene ether sulfone)s (FPAES) and poly (arylene ether ketone)s (FPAEK) with two types of NLO chromophores as pendant groups were obtained by a polycondensation reaction carried out using very mild reaction conditions. The glass transition temperature (Tg) of these copolymers is between 168 and 190°C. The SHG intensity was measured during thermal corona poling : the dipole orientation starts at 100°C, and reaches a maximum at 160°C, which is lower than Tg. During cooling of the film under the applied electric field, we observed an unusual drop of the SHG intensity starting at 120°C and reaching 70 % of the maximum value. The physical origin of this drop has been investigated and is possibly attributable to a secondary phase transition of the copolymers. Despite this decrease, d33 coefficients measured after poling vary between 2 and 15 pm/V at 1907 nm fundamental wavelength, depending on the first hyperpolarisability of the NLO chromophore. The dipole orientation of all these copolymers is very stable provided the temperature of the films is kept below the temperature threshold of 120 °C, which is below the Tg of the polymers.