Spin splitting unconstrained by electron pairing: the spin-vibronic states

Spin splitting of individual vibronic states was observed in a single molecule where all the electrons are paired, as well as a molecule with one extra electron injected. This observation was made possible by the use of a scanning tunneling microscope capable of reaching ∼800  mK in a magnetic field up to 9 T and the sharpness of the vibronic states, ∼1  meV. These conditions also led to the resolution of spectral diffusion caused by minute fluctuations at the probing location of the molecule.

Inhibiting fatty acid amide hydrolase normalizes endotoxin-induced enhanced gastrointestinal motility in mice

BACKGROUND AND PURPOSE

Gastrointestinal (GI) motility is regulated in part by fatty acid ethanolamides (FAEs), including the endocannabinoid (EC) anandamide (AEA). The actions of FAEs are terminated by fatty acid amide hydrolase (FAAH). We investigated the actions of the novel FAAH inhibitor AM3506 on normal and enhanced GI motility.

EXPERIMENTAL APPROACH

We examined the effect of AM3506 on electrically-evoked contractility in vitro and GI transit and colonic faecal output in vivo, in normal and FAAH-deficient mice treated with saline or LPS (100 µg·kg(-1), i.p.), in the presence and absence of cannabinoid (CB) receptor antagonists. mRNA expression was measured by quantitative real time-PCR, EC levels by liquid chromatography-MS and FAAH activity by the conversion of [(3)H]-AEA to [(3)H]-ethanolamine in intestinal extracts. FAAH expression was examined by immunohistochemistry.

KEY RESULTS

FAAH was dominantly expressed in the enteric nervous system; its mRNA levels were higher in the ileum than the colon. LPS enhanced ileal contractility in the absence of overt inflammation. AM3506 reversed the enhanced electrically-evoked contractions of the ileum through CB(1) and CB(2) receptors. LPS increased the rate of upper GI transit and faecal output. AM3506 normalized the enhanced GI transit through CB(1) and CB(2) receptors and faecal output through CB(1) receptors. LPS did not increase GI transit in FAAH-deficient mice.

CONCLUSIONS AND IMPLICATIONS

Inhibiting FAAH normalizes various parameters of GI dysmotility in intestinal pathophysiology. Inhibition of FAAH represents a new approach to the treatment of disordered intestinal motility.

Real-space imaging of Kondo screening in a two-dimensional O₂ lattice

Kondo lattice systems can exhibit unusual many-body behaviors that result from the interplay between onsite Kondo screening and intersite coupling. We used scanning tunneling microscopy to image the Kondo resonance in a nonconventional Kondo lattice formed by self-assembled oxygen (O(2)) molecules, which are paramagnetic, on the gold reconstructed surface [Au(110)-1×2]. The interplay between the intermolecular coupling for molecules adsorbed along chains and the onsite Kondo effect leads to the coexistence of both local and nonlocal Kondo screening at the atomic level. The latter provides evidence for collective deconfinement of magnetization induced in Au, whereas the former shows local "hybridization" between the Kondo clouds of nearest-neighbor O(2) molecules.

Laser and Thermal Induced Reactions of Mo(CO)6, CH3CH2OH, and NO on Si(111)7 × 7

Laser induced reactions of Mo(CO)6, CH3CH2OH, and NO adsorbed on Si(111)7 × 7 at 257 and 514 nm were studied and compared with thermally induced reactions under ultrahigh vacuum conditions utilizing laser induced desorption spectroscopy, thermal desorption spectroscopy, high resolution electron energy loss spectroscopy, and Auger electron spectroscopy. By using continuous wave laser irradiation, photolytic effects are clearly distinguished from pyrolytic effects. Mo(CO)6 and CH3CH2OH adsorbed on Si behave similarly as in the gas phase, whereas a substrate-mediated reaction channel is observed for NO adsorbed on Si.

Photoreactions of Mo(CO)6 on Potassium Precovered Silicon Surface with UV to IR Radiation

The adsorption and photoreactions of Mo(CO)6 coadsorbed with K on Si(111)7×7 at 90 K have been studied under ultra-high vacuum conditions. It is found that dissociative adsorption of Mo(CO)6 on the K preadsorbed surface occurs for coverages below a monolayer. A multilayer of physisorbed Mo(CO)6 molecules is formed on top of the monolayer. Under photon irradiation physisorbed Mo(CO)6 molecules are dissociated and CO desorption is observed. The photoreactions of Mo(CO)6 occur over a wide wavelength range from the UV to IR. In contrast, only UV radiation induces photoreactions of Mo(CO)6 on the K-free Si(111)7×7 surface. Evidently K opens a new channel for the photoreactions of Mo(CO)6 on the surface. A mechanism involving interactions between photogenerated charge carriers and the substrate-adsorbate complex is proposed.

Viewing the interior of a single molecule: vibronically resolved photon imaging at submolecular resolution

We report the spatial imaging of the photon transition probability of a single molecule at submolecular resolution. Photon imaging of a ringlike pattern is further resolved as two orthogonal vibronic transitions after incorporating spectral selectivity. A theoretical model and the calculated intensity images reveal that the transition probability is dominated by the symmetry of the positions of the tip and the transition dipole moment. This imaging technique enables the probing of the electronic and optical properties in the interior of a single molecule.

Adaptation of intestinal secretomotor function and nutrient absorption in response to diet-induced obesity

BACKGROUND

The gut plays a significant role in the development of obesity, notably through peptide signaling to the brain. However, few studies have investigated intestinal function per se in a rodent model of diet-induced obesity (DIO). Our aim was to investigate intestinal secretomotor function and glucose transport in DIO and diet-resistant (DR) rat jejunum.

METHODS

Male outbred Sprague-Dawley rats were maintained on a medium high fat diet for 9-10 weeks and split into DIO and DR groups based on weight gain. Mucosal-submucosal preparations of the proximal jejunum were mounted in Ussing chambers and voltage-clamped at 0 mV. Glucose (10 mmol L(-1)), 2-deoxy-D-glucose (10 mmol L(-1)), and leptin (10 nmol L(-1)) were added to the luminal side of the tissue and veratridine (30 micromol L(-1)), bethanechol (100 micromol L(-1)), and forskolin (10 micromol L(-1)) were added to the basolateral side of the tissue.

KEY RESULTS

Secretomotor responses were significantly decreased in DIO jejunum compared to DR tissues. Glucose-stimulated increases in I(sc) in DR animals, that were sensitive to leptin inhibition, were significantly reduced in DIO rats. Decreased sodium glucose transporter-1 mediated glucose transport was accompanied by a concomitant increase in the expression of jejunal glucose transporter-2.

CONCLUSIONS & INFERENCES

These data suggest that submucosal nerve function is compromised in DIO rats and electrogenic glucose transport is significantly decreased. The latter may represent an adaptive response to limit nutrient absorption in the jejunum from DIO rats. However, the loss of secretomotor control may lead to an altered host defense with a resultant change in intestinal flora contributing to the maintenance of obesity.

Azithromycin decreases crevicular fluid volume and mediator content

Azithromycin enhances the response to root planing and produces anti-inflammatory effects in treating chronic lung disease. This led us to hypothesize that azithromycin inhibits inflammatory mediator production in gingiva, leading to decreased gingival crevicular fluid (GCF) volume. To test this hypothesis, ten periodontally healthy volunteers received azithromycin every 24 hours for 48 hours. GCF samples were collected from 12 maxillary interproximal sites prior to azithromycin (baseline) and 2, 4, 7, and 14 days later. Samples were assayed for IL-1beta, IL-8, TNF-alpha, VEGF, IL-6, and IL-10. With azithromycin treatment, GCF volume decreased significantly on days 2 through 7 (P < 0.05), but increased toward baseline levels on day 14. This was accompanied by a transient decrease in the content of IL-1beta, IL-8, TNF-alpha, and VEGF (P < 0.05). IL-6 and IL-10 were not detected. Since plaque was absent throughout the study, the findings suggest that azithromycin produces anti-inflammatory effects in gingiva.

The subfornical organ: a central nervous system site for actions of circulating leptin

Adipose tissue plays a critical role in energy homeostasis, secreting adipokines that control feeding, thermogenesis, and neuroendocrine function. Leptin is the prototypic adipokine that acts centrally to signal long-term energy balance. While hypothalamic and brain stem nuclei are well-established sites of action of leptin, we tested the hypothesis that leptin signaling occurs in the subfornical organ (SFO). The SFO is a circumventricular organ (CVO) that lacks the normal blood-brain barrier, is an important site in central autonomic regulation, and has been suggested to have a role in modulating peripheral signals indicating energy status. We report here the presence of mRNA for the signaling form of the leptin receptor in SFO and leptin receptor localization by immunohistochemistry within this CVO. Central administration of leptin resulted in phosphorylation of STAT3 in neurons of SFO. Whole cell current-clamp recordings from dissociated SFO neurons demonstrated that leptin (10 nM) influenced the excitability of 64% (46/72) of SFO neurons. Leptin was found to depolarize the majority of responsive neurons with a mean change in membrane potential of 7.3 +/- 0.6 mV (39% of all SFO neurons), while the remaining cells that responded to leptin hyperpolarized (-6.9 +/- 0.7 mV, 25% of all SFO neurons). Similar depolarizing and hyperpolarizing effects of leptin were observed in recordings from acutely prepared SFO slice preparations. Leptin was found to influence the same population of SFO neurons influenced by amylin as three of four cells tested for the effects of bath application of both amylin and leptin depolarized to both peptides. These observations identify the SFO as a possible central nervous system location, with direct access to the peripheral circulation, at which leptin may act to influence hypothalamic control of energy homeostasis.

Low body mass not vitamin D receptor polymorphisms predict osteoporosis in patients with inflammatory bowel disease

BACKGROUND

Osteoporosis is a recognized complication of inflammatory bowel disease (IBD). Aim To investigate the role of environmental factors and vitamin D receptor (VDR) variants on the prevalence of osteoporosis.

METHODS

DEXA scans and case note review were performed on 440 IBD patients from 1997 to 2006. All the IBD patients and 240 healthy controls were genotyped for VDR variants Taq-1 and Apa-1 using PCR-RFLP.

RESULTS

Osteoporosis and osteopenia rates were 15% and 18% for IBD, 16% and 18% for Crohn's disease (CD) and 13% and 19% for ulcerative colitis, respectively. On univariate analysis of the CD patients, low body mass index (BMI, <18.5) and smoking status (P = 0.008 and 0.005 respectively) were associated with osteoporosis and osteopenia. Low BMI was also associated with osteoporosis on multivariate analysis in CD (P = 0.021, OR 5.83, CI 1.31-25.94). No difference was observed between Taq-1 and Apa-1 VDR polymorphisms in IBD, CD, ulcerative colitis and healthy controls. However, CD males were more likely to carry the variant Taq-1 polymorphism than healthy controls males (P = 0.0018, OR 1.94, CI 1.28-2.92) and female CD patients (P = 0.0061, OR 1.60, CI 1.17-2.44).

CONCLUSIONS

In this well-phenotyped cohort of IBD patients, a relatively low prevalence of osteoporosis was observed. Low BMI was the only independent risk factor identified to be associated with osteoporosis.

Controlling single-molecule negative differential resistance in a double-barrier tunnel junction

We observed the transition from negative differential resistance (NDR) to the absence of NDR in the differential conductance (dI/dV) spectra of single copper-phthalocyanine (CuPc) molecules adsorbed on one, two, and three atomic layers of NaBr grown on a NiAl(110) substrate. Through numerical simulation, this transition is attributed to two phenomena in the double-barrier tunnel junction: (i) the opposite bias dependence of the vacuum and NaBr barrier heights, and (ii) the changing barrier widths for CuPc molecules adsorbed on different layers of NaBr.

Downregulated hypothalamic 5-HT3 receptor expression and enhanced 5-HT3 receptor antagonist-mediated improvement in fatigue-like behaviour in cholestatic rats

The serotonin neurotransmitter system, including the 5-HT(3) receptor, has been implicated in the genesis of fatigue in patients with liver disease. Therefore, we examined the possible role of 5-HT(3) receptors in cholestasis-associated fatigue. Rats were either bile duct resected (BDR) or sham resected and studied 10 days postsurgery. A significant decrease in hypothalamic 5-HT(3) receptor expression was detected by immunohistochemistry and Western blot in BDR vs sham rats, coupled with increased hypothalamic serotonin turnover identified by an elevated 5-hydroxyindoleacetic acid (5-HIAA) to 5-HT ratio in BDR vs sham rats. To examine fatigue-like behaviour, an activity meter was used. BDR rats exhibited significantly lower locomotor activity than did sham animals. Subcutaneous injection of the 5-HT(3) receptor antagonist tropisetron (0.1 mg kg(-1)) resulted in significantly increased locomotor activity in BDR rats compared to the activity in saline-treated controls, but was without effect in sham rats. However, a 10-fold higher dose of tropisetron significantly increased locomotor activity in both BDR and sham rats compared to saline-injected controls. These findings indicate that cholestasis in the rat is associated with increased hypothalamic serotonin turnover, decreased hypothalamic 5-HT(3) receptor expression, and enhanced sensitivity to locomotor activation induced by 5-HT(3) receptor antagonism, thereby implicating the 5-HT(3) receptor system in cholestasis associated fatigue.

Reversible switching among three adsorbate configurations in a single [2.2]paracyclophane-based molecule

Single 4,7,12,15-tetrakis(4'-dimethylaminostyryl)[2.2]paracyclophane molecules adsorb on NiAl(110) in different configurations. When the symmetry axes of the molecules are properly oriented with respect to the surface lattice, three adsorbate states of different conductance can be reversibly induced and directly imaged with a scanning tunneling microscope. Couplings between tunneling electrons and adsorbate vibrational and electronic states are primarily responsible for the transformation. However, change from low to high conductance configuration can also be triggered by electric field in the junction.

Spatial variations in submolecular vibronic spectroscopy on a thin insulating film

Scanning tunneling spectroscopy on single naphthalocyanine molecules adsorbed on an ultrathin aluminum oxide film exhibits electron-vibronic coupling that varies with the position of tunneling over the molecule. The spectra at different positions are composed of several series of equally spaced peaks, which are interpreted as progression of progressions of molecular vibrational modes. The spatial variations correlate with the molecular orbital structure, revealing spatially dependent electron-vibronic coupling and selective vibrational excitation.

Unravelling the complexities of the NF-κB signalling pathway using mouse knockout and transgenic models

The nuclear factor-kappaB (NF-kappaB) signalling pathway serves a crucial role in regulating the transcriptional responses of physiological processes that include cell division, cell survival, differentiation, immunity and inflammation. Here we outline studies using mouse models in which the core components of the NF-kappaB pathway, namely the IkappaB kinase subunits (IKKalpha, IKKbeta and NEMO), the IkappaB proteins (IkappaBalpha, IkappaBbeta, IkappaBvarepsilon and Bcl-3) and the five NF-kappaB transcription factors (NF-kappaB1, NF-kappaB2, c-Rel, RelA and RelB), have been genetically manipulated using transgenic and knockout technology.

Wavelet-based prognostic model with comparative genomic hybridization (CGH) data in patients with hepatocellular carcinoma (HCC)

20026

Background: In order to obtain a good prognostic model for HCC, clinical data alone may not be adequate. DNA microarray technology has enabled quantification of thousands of genes in a single assay but it has the inborn drawback of high background noise. In order to deal with the problem of information overflow, we developed multivariate dependencies approach using CGH to guide the initial modeling process. This approach takes into account the multivariate nature and potential interaction among the genes during the prognostic modeling process. Methods: The study includes 165 patients with CGH data containing 858 regions/bands. The clinical outcome is survival at 1.72 years. Potential prognostic factors include CGH regions, albumin, ALT, bilirubin, AFP, ascites, alkaline phosphatase (ALP), tumor size, and encephalopathy. We used a blocked wavelet-shrinkage principal component analysis (BWSPCA) to reduce the dimension of CGH data with respect to clinical outcome and followed by logistic regression. We compared the BWSPCA with PCA alone, supervised PCA (Bair et al. 2004), and supervised BWSPCA. Results: Among the 165 patients, 133 (80%) were male, average age of 54.8 years, 78 (47%) stage I-II and 75 (45%) ECOG 0–2. PCA alone and supervised PCA models failed to identify significant CGH regions. BWSPCA model includes tumor size (p = 0.005), albumin (p = 0.047), ALP (p = 0.025), Chr.6q25.1 (p = 0.031), Chr.12q24.32 (p = 0.012), Chr.Xq28 (p = 0.035). Supervised BWSPCA approach includes tumor size (p = 0.016), ALP (p = 0.002), Chr.12q24.11 (p = 0.047). The area under the receiver operating curve (ROC) for the BWSPCA model was 0.78 with a sensitivity and specificity about 0.8 and 0.6 respectively. Conclusions: PCA alone is not effective in identifying CGH regions as prognostic factors. Supervised learning approach did not improve the results. The BWSPCA method identified a number of significant CGH regions associated with survival outcome for HCC patients. These results would be verified in future study. This method will be extended and applied to develop prognostic models using both CGH and DNA microarray data. Acknowledgement: This study is funded by the Research Grant Council of Hong Kong #CUHK4469/03M.

No significant financial relationships to disclose.

Imaging and vibrational spectroscopy of single pyridine molecules on Ag(110) using a low-temperature scanning tunneling microscope

A scanning tunneling microscope (STM) was used to extract the images of single, isolated pyridine molecules adsorbed on Ag(110) and to record their vibrational spectrum at 13 K. On the STM image, the pyridine molecule appears as an elongated protrusion along the [001] direction on top of a silver atom, indicating that it is bonded through its nitrogen lone pair electrons. STM inelastic electron tunneling spectroscopy of the adsorbed pyridine revealed C-D and C-H stretch modes at 282 and 378 meV, respectively.

Atomic-Scale Coupling of Photons to Single-Molecule Junctions

Spatial resolution at the atomic scale has been achieved in the coupling of light to single molecules adsorbed on a surface. Electron transfer to a single molecule induced by green to near-infrared light in the junction of a scanning tunneling microscope (STM) exhibited spatially varying probability that is confined within the molecule. The mechanism involves photo-induced resonant tunneling in which a photoexcited electron in the STM tip is transferred to the molecule. The coupling of photons to the tunneling process provides a pathway to explore molecular dynamics with the combined capabilities of lasers and the STM.

Atomic scale control of single molecule charging

A scanning tunneling microscope was used to study charging of single copper phthalocyanine molecules adsorbed on an ultrathin Al(2)O(3) film grown on a NiAl(110) surface. A double-barrier tunnel junction is formed by a vacuum barrier between the tip and the molecule and an oxide barrier between the molecule and the NiAl. In this geometry the molecule can be charged by the tunneling electrons. This charging was found to be strongly dependent on the position of the tip above the molecule and the applied bias voltage.

Atomic-scale rectification at microwave frequency

Microwave of known amplitude and frequency, irradiating the junction of a low temperature scanning tunneling microscope, was found to induce a dc signal. This rectification current is spatially localized and exhibits chemical sensitivity at the atomic scale. Dependence of the rectification current on the sample bias voltage reveals spin splitting in the electronic state of a single Mn atom and vibrations of single MnCO molecule. These results demonstrate the feasibility of atomic scale nonlinear spectroscopy and the potential for the detection of resonance phenomena excited with a spatially extended electromagnetic wave.