Visualizing delocalized correlated electronic states in twisted double bilayer graphene.

The discovery of interaction-driven insulating and superconducting phases in moiré van der Waals heterostructures has sparked considerable interest in understanding the novel correlated physics of these systems. While a significant number of studies have focused on twisted bilayer graphene, correlated insulating states and a superconductivity-like transition up to 12 K have been reported in recent transport measurements of twisted double bilayer graphene. Here we present a scanning tunneling microscopy and spectroscopy study of gate-tunable twisted double bilayer graphene devices. We observe splitting of the van Hove singularity peak by ~20 meV at half-filling of the conduction flat band, with a corresponding reduction of the local density of states at the Fermi level. By mapping the tunneling differential conductance we show that this correlated system exhibits energetically split states that are spatially delocalized throughout the different regions in the moiré unit cell, inconsistent with order originating solely from onsite Coulomb repulsion within strongly-localized orbitals. We have performed self-consistent Hartree-Fock calculations that suggest exchange-driven spontaneous symmetry breaking in the degenerate conduction flat band is the origin of the observed correlated state. Our results provide new insight into the nature of electron-electron interactions in twisted double bilayer graphene and related moiré systems.

Extraction and characterization of polysaccharides from Semen Cassiae by microwave-assisted aqueous two-phase extraction coupled with spectroscopy and HPLC.

A novel and rapid method for simultaneous extraction and separation of the different polysaccharides from Semen Cassiae (SC) was developed by microwave-assisted aqueous two-phase extraction (MAATPE) in a one-step procedure. Using ethanol/ammonium sulfate system as a multiphase solvent, the effects of MAATPE on the extraction of polysaccharides from SC such as the composition of the ATPS, extraction time, temperature and solvent-to-material ratio were investigated by UV-vis analysis. Under the optimum conditions, the yields of polysaccharides were 4.49% for the top phase, 8.80% for the bottom phase and 13.29% for total polysaccharides, respectively. Compared with heating solvent extraction and ultrasonic assisted extraction, MAATPE exhibited the higher extraction yields in shorter time. Fourier-transform infrared spectra showed that two polysaccharides extracted from SC to the top and bottom phases by MAATPE were different from each other in their chemical structures. Through acid hydrolysis and PMP derivatization prior to HPLC, analytical results by indicated that a polysaccharide of the top phases was a relatively homogeneous homepolysaccharide composed of dominant gucose glucose while that of the bottom phase was a water-soluble heteropolysaccharide with multiple components of glucose, xylose, arabinose, galactose, mannose and glucuronic acid. Molar ratios of monosaccharides were 95.13:4.27:0.60 of glucose: arabinose: galactose for the polysaccharide from the top phase and 62.96:14.07:6.67: 6.67:5.19:4.44 of glucose: xylose: arabinose: galactose: mannose: glucuronic acid for that from the bottom phase, respectively. The mechanism for MAATPE process was also discussed in detail. MAATPE with the aid of microwave and the selectivity of the ATPS not only improved yields of the extraction, but also obtained a variety of polysaccharides. Hence, it was proved as a green, efficient and promising alternative to simultaneous extraction of polysaccharides from SC.

Enantioseparation of Racemic Flurbiprofen by Aqueous Two-Phase Extraction With Binary Chiral Selectors of L-dioctyl Tartrate and L-tryptophan.

A novel method for chiral separation of flurbiprofen enantiomers was developed using aqueous two-phase extraction (ATPE) coupled with biphasic recognition chiral extraction (BRCE). An aqueous two-phase system (ATPS) was used as an extracting solvent which was composed of ethanol (35.0% w/w) and ammonium sulfate (18.0% w/w). The chiral selectors in ATPS for BRCE consideration were L-dioctyl tartrate and L-tryptophan, which were screened from amino acids, ß-cyclodextrin derivatives, and L-tartrate esters. Factors such as the amounts of L-dioctyl tartrate and L-tryptophan, pH, flurbiprofen concentration, and the operation temperature were investigated in terms of chiral separation of flurbiprofen enantiomers. The optimum conditions were as follows: L-dioctyl tartrate, 80 mg; L-tryptophan, 40 mg; pH, 4.0; flurbiprofen concentration, 0.10 mmol/L; and temperature, 25 °C. The maximum separation factor α for flurbiprofen enantiomers could reach 2.34. The mechanism of chiral separation of flurbiprofen enantiomers is discussed and studied. The results showed that synergistic extraction has been established by L-dioctyl tartrate and L-tryptophan, which enantioselectively recognized R- and S-enantiomers in top and bottom phases, respectively. Compared to conventional liquid-liquid extraction, ATPE coupled with BRCE possessed higher separation efficiency and enantioselectivity without the use of any other organic solvents. The proposed method is a potential and powerful alternative to conventional extraction for separation of various enantiomers.

[[Chiral separation of five arylpropionic acid drugs and determination of their enantiomers in pharmaceutical preparations by reversed-phase high performance liquid chromatography with cellulose-tris-(4-methylbenzoate) stationary phase]].

Chromatographic behaviors for enantiomeric separation of arylpropionic acid drugs were systematically developed by reversed phase-high performance liquid chromatography (RP-HPLC) using cellulose-tris-(4-methylbenzoate) (CTMB) as chiral stationary phase (CSP). The effects of the composition of the mobile phase, additives and temperature on chiral separation of flurbiprofen, pranoprofen, naproxen, ibuprofen and loxoprofen were further investigated. The enantiomers had been successfully separated on CSP of CTMB by the mobile phase of methanol-0.1% (v/v) formic acid except naproxen by acetonitrile-0.1% (v/v) formic acid at 25 °C. The mechanisms of the racemic resolution for the above mentioned five drugs are discussed thermodynamically and structurally. The resolutions between respective enantiomers for arylpropionic acid drugs on CTMB had significant differences due to their chromatographic behaviors. The order of resolutions ranked pranoprofen, loxoprofen, flurbiprofen, ibuprofen and naproxen. The method established has been successfully applied to the determination of the enantiomers of the five drugs in commercial preparations under the optimized conditions. It proved that the method is simple, reliable and accurate.

Combined TIPS with portal-azygous disconnection improved the long term clinical outcome in portal hypertension patients.

OBJECTIVE: The results of TIPS and the combined TIPS and portal-azygous disconnection for portal hypertension and variceal bleeding were evaluated. METHODS: 358 patients with portal hypertension were admitted to our clinical ward because of variceal bleeding. 263 patients underwent TIPS and 95 patients with combined TIPS and portal-azygous disconnection. Portal hemodynamics was evaluated by pressure measurements, venography and Doppler ultrasound before and 2 weeks after the procedure. The rates of shunt patency, rebleeding, encephalopathy and survival were observed during the follow-up period from 1 to 10 years. RESULTS: The portal pressure and HVPG were decreased significantly after TIPS. TIPS procedure was successfully performed in 97.50% patients. During 1 month after treatment, acute shunt occlusion occurred in 3.42% patients with TIPS and there were no occluded shunts in patients with combined TIPS and portal-azygous disconnection. Encephalopathy was observed in 36.50% patients with TIPS and 18.95% with combined TIPS and portal-azygous disconnection. Recurrent variceal bleeding was documented in 6.46% patients with TIPS and none of patients with combined TIPS and azygous portal disconnection. Thirty-three patients with TIPS and two patients with combined TIPS and portal-azygous disconnection died. During follow-up periods, the patency of shunts in patients with TIPS and patients combined TIPS and azygous portal disconnection was 68.47, 43.84 and 87.06, 57.65% in 12 and 24 months after operation, respectively. The rates of rebleeding, and encephalopathy in patients with TIPS and patients with combined TIPS and azygous portal disconnection were 17.95, 31.79 and 7.04, 16.47%, respectively. The survival rate in 1, 5, 10 years in patients with TIPS and patients combined TIPS and azygous portal disconnection was 87.68, 51.23, 39.90 and 94.12, 81.18, 76.47%. CONCLUSION: Combined TIPS and portal-azygous disconnection can improve the effect of TIPS for portal hypertension.

[The change in expression of Toll-like receptor 4 on peripheral blood mononuclear cell after continuous renal replacement therapy in patients with sepsis].

OBJECTIVE: To explore the change in Toll-like receptor 4 (TLR4) of peripheral blood mononuclear cell (PBMC) and the expression of cytokines in patients with sepsis, and to investigate the role of continuous renal replacement therapy (CRRT) in its modulation. METHODS: A clinical study was performed in 13 patients with sepsis which were divided into improved group (n=7) and healing group (n=6), according to their outcome. Another 6 healthy individuals served as normal control. The mRNA expression of TLR4 on PBMC was detected by reverse transcription-polymerase chain reaction (RT-PCR), the protein expression of TLR4 on PBMC was assayed with flow cytometry, the expressions of IL-6 and TNF-alpha were measured by enzyme linked immunoadsorbent assay (ELISA). RESULTS: TLR4 mRNA, IL-6, TNF-alpha, and TLR4 protein expressions were upregulated markedly in patients suffering from sepsis. The above parameters were decreased significantly after CRRT (all P<0.05) and in the same time, the clinic condition turn up, in the meanwhile, the expression of TLR4 went down, but it still have some expression on monocyte in improved group. CONCLUSION: The down regulation of TLR4 through CRRT may imply an important mechanism in the CRRT on patients with sepsis.

[Role of trefoil peptides in modulation of gastric adaptation to stress].

OBJECTIVE: To investigate the role of trefoil peptides in modulation of gastric adaptation to water restraint stress (WRS) in rats. METHODS: Wistar rats were exposed to single or repeated WRS for 4 hours every other day for up to 6 days, gastric mucosal blood flow (GMBF) was measured by LDF-3 flowmeter, the extent of gastric mucosal lesions was evaluated grossly and histologically, and expression of PS2 intestinal trefoil peptide (ITF), cyclooxygenase (COX-2), inducible nitric oxide synthase (iNOS) and transferase growth factor-alpha (TGF-alpha) were determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western blot. RESULTS: One application of WRS produced extensive gastric mucosal erosion. With repeated WRS, the gastric mucosa became adapted to the stress of WRS, and the ulcerative index (UI) was reduced by 22.0% that of one WRS challenge after four consecutive WRS. Expression of PS2 was markedly decreased and expression of ITF, COX-2, iNOS and TGF-alpha were markedly increased after single stress. But this adaptation to WRS was accompanied by increased GMBF and active cell proliferation in the neck region of gastric glands, and by increased expression of PS2, ITF, TGF-alpha, but reduced expression of COX-2 and iNOS. CONCLUSION: Gastric adaptation to WRS injury involves enhanced cell proliferation, increased expression of PS2, ITF, TGF-alpha and reduced expression of COX-2 and iNOS, suggesting trefoil peptides might play an important modulating role in this phenomenon.

Serial analysis of gene expression in mice with lipopolysaccharide-induced acute lung injury.

OBJECTIVE: To monitor the systemic gene expression profile in a murine model of lipopolysaccharide-induced acute lung injury. METHODS: Acute lung injury was induced by intratracheal injection of lipopolysaccharide in 3 mice. Another 3 normal mice receiving same volume of normal saline were taken as the controls. The comprehensive gene expression profile was monitored by the recently modified long serial analysis of gene expression. RESULTS: A total of 24,670 tags representing 12,168 transcripts in the control mice and 26,378 tags representing 13,397 transcripts in the mice with lung injury were identified respectively. There were 11 transcripts increasing and 7 transcripts decreasing more than 10 folds in the lipopolysaccharide-treated mice. The most overexpressed genes in the mice with lung injury included serum amyloid A3, metallothionein 2, lipocalin 2, cyclin-dependent kinase inhibitor 1A, lactate dehydrogenase 1, melatonin receptor, S100 calcium-binding protein A9, natriuretic peptide precursor, etc. Mitogen activated protein kinase 3, serum albumin, complement component 1 inhibitor, and ATP synthase were underexpressed in the lung injury mice. CONCLUSIONS: Serial analysis of gene expression provides a molecular characteristic of acute lung injury.

Cyclooxygenase 2, pS2, inducible nitric oxide synthase and transforming growth factor alpha in gastric adaptation to stress.

AIM: To determine the role of mucosal gene expression of cyclooxygenase 2 (COX-2), pS2 (belongs to trefoil peptides), inducible nitric oxide synthase (iNOS) and transforming growth factor alpha (TGFalpha) in gastric adaptation to water immersion and restraint stress (WRS) in rats. METHODS: Wistar rats were exposed to single or repeated WRS for 4 h every other day for up to 6 d. Gastric mucosal blood flow (GMBF) was measured by laser Doppler flowmeter-3. The extent of gastric mucosal lesions were evaluated grossly and histologically and expressions of COX-2, pS2,iNOS and TGFalpha were determined by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot. RESULTS: The damage to the surface of gastric epithelium with focal areas of deep haemorrhagic necrosis was induced by repeated WRS. The adaptative cytoprotection against stress was developed with activation of cell proliferation in the neck regions of gastric glands. The ulcer index (UI) in groups II, III and IV was markedly reduced as compared with group I (I: 47.23+/-1.20; IV: 10.39+/-1.18,P<0.01). GMBF significantly decreased after first exposure to WRS with an adaptive increasement of GMBF in experimental groups after repetitive challenges with WRS. After the 4th WRS, the value of GMBF almost restored to normal level (I: 321.87+/-8.85; IV: 455.95+/-11.81, P<0.01). First WRS significantly decreased the expression of pS2 and significantly increased the expressions of COX-2, iNOS and TGFalpha. After repeated WRS, pS2 and TGFalpha expressions gradually increased (pS2: I: 0.37+/-0.02; IV: 0.77+/-0.01; TGFalpha: I: 0.86+/-0.01; IV: 0.93+/-0.03, P<0.05) with a decrease in the expressions of COX-2 and iNOS (COX-2: I: 0.45+/-0.02; IV: 0.22+/-0.01; iNOS: I: 0.93+/-0.01; IV: 0.56+/-0.01, P<0.01). Expressions of pS2, COX-2, iNOS and TGFalpha showed regular changes with a good relationship among them. CONCLUSION: Gastric adaptation to WRS injury involves enhanced cell proliferation, increased expression of pS2 and TGFalpha, and reduced expression of COX-2 and iNOS. These changes play an important role in adaptation of gastric mucosa after repeated WRS.

Role of TFF in healing of stress-induced gastric lesions.

AIM: To determine the changes of pS2 and ITF of TFF expression in gastric mucosa and the effect on ulcer healing of pS2, ITF to Water-immersion and restraint stress (WRS) in rats. METHODS: Wistar rats were exposed to single or repeated WRS for 4 h every other day for up to 6 days.Gastric mucosal blood flow (GMBF) was measured by LDF-3 flowmeter and the extent of gastric mucosal lesions were evaluated grossly and histologically. Expression of pS2 and ITF mRNA was determined by RT-PCR. Immunohistochemistry was used to further detect the expression of pS2 and ITF. RESULTS: WRS applied once produced numerous gastric mucosal erosions, but the number of these lesions gradually declined and GMBF restored at 2, 4, 8 h after stress. The area of gastric mucosal lesion was reduced by 64.9 % and GMBF was increased by 89.8 % at 8 h. The healing of stress-induced ulcerations was accompanied by increased expression of pS2 (0.51+/-0.14 vs 0.77+/-0.11, P<0.01) and ITF (0.022+/-0.001 vs 0.177+/-0.010, P<0.01). The results were demonstrated further by immunohistochemistry of pS2 (0.95+/-0.11 vs 1.41+/-0.04, P<0.01) and ITF (0.134+/-0.001 vs 0.253+/-0.01,P<0.01). With repeated WRS, adaptation to this WRS developed, the area of gastric mucosal lesions was reduced by 22.0 % after four consecutive WRS. This adaptation to WRS was accompanied by increased GMBF (being increased by 94.2 %), active cell proliferation in the neck region of gastric glands, and increased expression of pS2 (0.37+/-0.02 vs 0.77+/-0.01, P<0.01) and ITF (0.040+/- 0.001 vs 0.372+/-0.010, P<0.01). The result was demonstrated further by immunohistochemistry of pS2 (0.55+/-0.04 vs 2.46+/-0.08, P<0.01) and ITF (0.134+/-0.001 vs 0.354+/-0.070, P<0.01). CONCLUSION: TFF may not only participate in the early phase of epithelial repair known as restitution (maked by increased cell migration), but also play an important role in the subsequent, protracted phase of glandular renewal(made by cell proliferation).

Posttraumatic expression of MHC II molecules: an experimental and clinical study.

OBJECTIVE: To evaluate the role of MHC II expression in posttrauma immune disturbances and infections. METHODS: In experimental study, peritoneal macrophages were harvested from traumatized mice and treated with GM-CSF, Ia molecules were determined by flow cytometry. In 24 trauma patients, monocyte HLA-DR expression was measured by APAAP technique. RESULTS: Marked inhibition of MHC II molecule expression was found in both traumatized mice and patients. In traumatic patients with infection, the inhibition was more severe. Treatment with GM-CSF in mice partially restored the Ia expression. CONCLUSIONS: Inhibition of MHC II molecules plays an important role in postrauma immune disturbances. There is a close relationship between HLA-DR inhibition and clinical infections.