Normal vs. Inverted Ordering of Reduction Potentials in [FeFe]-Hydrogenases Biomimetics: Effect of the Dithiolate Bulk.

Three hexacarbonyl diiron dithiolate complexes [Fe2 (CO)6 (µ-(SCH2 )2 X)] with different substituted bridgeheads (X=CH2 , CEt2 , CBn2 (Bn=CH2 C6 H5 )), have been studied under the same experimental conditions by cyclic voltammetry in dichloromethane [NBu4 ][PF6 ] 0.2 M. DFT calculations were performed to rationalize the mechanism of reduction of these compounds. The three complexes undergo a two-electron transfer whose the mechanism depends on the bulkiness of the dithiolate bridge, which involves a different timing of the structural changes (Fe-S bond cleavage, inversion of conformation and CO bridging) vs redox steps. The introduction of a bulky group in the dithiolate linker has obviously an effect on normally ordered (as for propanedithiolate (pdt)) or inverted (pdtEt2 , pdtBn2 ) reduction potentials. Et→Bn replacement is not theoretically predicted to alter the geometry and energy of the most stable mono-reduced and bi-reduced forms but such a replacement alters the kinetics of the electron transfer vs the structural changes.

Intestinal Conventional Ultrasonography, Contrast-Enhanced Ultrasonography and Magnetic Resonance Enterography in Assessment of Crohn's Disease Activity: A Comparison with Surgical Histopathology Analysis.

BACKGROUND AND AIMS: Contrast-enhanced ultrasonography (CEUS) is a potential interesting method for assessing accurately Crohn's disease (CD) activity. We compared the value of intestinal ultrasonography (US) coupled with contrast agent injection with that of magnetic resonance enterography (MRE) in the assessment of small bowel CD activity using surgical histopathology analysis as reference. METHODS: Seventeen clinically active CD patients (14 women, mean age 33 years) requiring an ileal or ileocolonic resection were prospectively enrolled. All performed a MRE and a US coupled with contrast agent injection (CEUS) less than 8 weeks prior to surgery. Various imaging qualitative and quantitative parameters were recorded and their respective performance to detect disease activity, disease extension and presence of complications was compared to surgical histopathological analysis. RESULTS: The median wall thickness measured by US differed significantly between patients with non-severely active CD (n = 5) and those with severely active CD (n = 12) [7.0 mm, IQR (6.5-9.5) vs 10.0 mm, IQR (8.0-12.0), respectively; p = 0.03]. A non-significant trend was found with MRE with a median wall thickness in severe active CD of 10.0 mm, IQR (8.0-13.7) compared with 8.0 mm, IQR (7.5-10.5) in non-severely active CD (p = 0.07). The area under the ROC curve (AUROC) of the wall thickness assessed by US and MRE to identify patients with or without severely active CD on surgical specimens were 0.85, 95% CI (0.64-1.04), p = 0.03 and 0.80, 95% CI (0.56-1.01), p = 0.07, respectively. Among the parameters derived from the time-intensity curve during CEUS, time to peak and rise time were the two most accurate markers [AUROC = 0.88, 95% CI (0.70-1.04), p = 0.02 and 0.86, 95% CI (0.68-1.04), p = 0.03] to detect patients with severely active CD assessed on surgical specimens. CONCLUSION: The accuracy of intestinal CEUS is close to that of conventional US to detect disease activity. A thickened bowel and shortened time to peak and rise time were the most accurate to identify CD patients with severe histological disease activity.

Insights into Triazolylidene Ligands Behaviour at a Di-Iron Site Related to [FeFe]-Hydrogenases.

The behaviour of triazolylidene ligands coordinated at a {Fe2(CO)5(µ-dithiolate)} core related to the active site of [FeFe]-hydrogenases have been considered to determine whether such carbenes may act as redox electron-reservoirs, with innocent or non-innocent properties. A novel complex featuring a mesoionic carbene (MIC) [Fe2(CO)5(Pmpt)(µ-pdt)] (1; Pmpt = 1-phenyl-3-methyl-4-phenyl-1,2,3-triazol-5-ylidene; pdt = propanedithiolate) was synthesized and characterized by IR, 1H, 13C{1H} NMR spectroscopies, elemental analyses, X-ray diffraction ,and cyclic voltammetry. Comparison with the spectroscopic characteristics of its analogue [Fe2(CO)5(Pmbt)(µ-pdt)] (2; Pmbt = 1-phenyl-3-methyl-4-butyl-1,2,3-triazol-5-ylidene) showed the effect of the replacement of a n-butyl by a phenyl group in the 1,2,3-triazole heterocycle. A DFT study was performed to rationalize the electronic behaviour of 1, 2 upon the transfer of two electrons and showed that such carbenes do not behave as redox ligands. With highly perfluorinated carbenes, electronic communication between the di-iron site and the triazole cycle is still limited, suggesting low redox properties of MIC ligands used in this study. Finally, although the catalytic performances of 2 towards proton reduction are weak, the protonation process after a two-electron reduction of 2 was examined by DFT and revealed that the protonation process is favoured by S-protonation but the stabilized diprotonated intermediate featuring a {Fe-H⋯H-S} interaction does not facilitate the release of H2 and may explain low efficiency towards HER (Hydrogen Evolution Reaction).

Insights into the Two-Electron Reductive Process of [FeFe]H2 ase Biomimetics: Cyclic Voltammetry and DFT Investigation on Chelate Control of Redox Properties of [Fe2 (CO)4 (κ2 -Chelate)(µ-Dithiolate)].

The electrochemical reduction of complexes [Fe2 (CO)4 (κ2 -phen)(µ-xdt)] (phen=1,10-phenanthroline; xdt=pdt (1), adtiPr (2)) in MeCN-[Bu4 N][PF6 ] 0.2 m is described as a two-reduction process. DFT calculations show that 1 and its monoreduced form 1- display metal- and phenanthroline-centered frontier orbitals (LUMO and SOMO) indicating the non-innocence of the phenanthroline ligand. Two energetically close geometries were found for the doubly reduced species suggesting an intriguing influence of the phenanthroline ligand leading to the cleavage of a Fe-S bond as proposed generally for this type of complex or retaining the electron density and avoiding Fe-S cleavage. Extension of calculations to other complexes with edt, adtiPr bridge and even virtual species [Fe2 (CO)4 (κ2 -phen)(µ-adtR )] (R=CH(CF3 )2 , H) or [Fe2 (CO)4 (κ2 -phen)(µ-pdtR )] (R=CH(CF3 )2 , iPr) showed that the relative stability between both two-electron-reduced isomers depends on the nature of the bridge and the possibility to establish a remote anagostic interaction between the iron center {Fe(CO)3 } and the group carried by the bridged-head atom of the dithiolate group.

A Diiron Hydrogenase Mimic Featuring a 1,2,3-Triazolylidene.

A novel complex featuring a mesoionic carbene [Fe2(CO)5(trz)(µ-pdt)] (1) (trz = 1-phenyl-l,3-methyl,4-butyl-1,2,3-triazol-5-ylidene), was synthesized and spectroscopically and structurally characterized. The reductive behaviour of this compound in the presence and in the absence of acid (CH3CO2H) was examined by cyclic voltammetry (CV) that revealed the lack of efficient activity towards proton reduction.

FeMo Heterobimetallic Dithiolate Complexes: Investigation of Their Electron Transfer Chemistry and Reactivity toward Acids, a Density Functional Theory Rationalization.

The electrochemical behavior of complexes [FeMo(CO)5(κ2-dppe)(µ-pdt)] (1) and [FeMo(CO)4(MeCN)(κ2-dppe)(µ-pdt)] (2), in the absence and in the presence of acid, has been investigated. The reduction of 1 follows at slow scan rates, in CH2Cl2-[NBu4][PF6] and acid-free media, an ECrevE mechanism that is supported by cyclic voltammetry (CV) experiments and digital CV simulations. In MeCN-[NBu4][PF6], the electrochemical reduction of 1 is the same as in dichloromethane and follows an ECE mechanism at slow scan rates, but with a positive shift of the redox potentials. In contrast, the oxidation of 1 is strongly solvent-dependent. In dichloromethane, the oxidation of 1 is reversible and involves a single electron, while in acetonitrile, it is irreversible at moderate and slow scan rates ( v ≤ ca. 1 V s-1), and some chemical reversibility is apparent at higher scan rates ( v = 10 V s-1). Density functional theory calculations revealed that the chemical step in the ECrevE mechanism corresponds to the dissociation of one PPh2 end of the diphosphine ligand and the transfer of the semibridging CO to the Fe atom, similarly to the mechanism observed in the FeFe analogue complex. However, in the case of 1, the subsequent coordination of the phosphine ligand to the other metal is an unfavorable process.

Electrochemical and Theoretical Investigations of the Oxidatively Induced Reactivity of the Complex [Fe2 (CO)4 (κ2 -dmpe)(µ-adtBn )] Related to the Active Site of [FeFe] Hydrogenases.

Electrochemical oxidation of the complex [Fe2 (CO)4 (κ2 -dmpe)(µ-adtBn )] (adtBn =(SCH2 )2 NCH2 C6 H5 , dmpe=Me2 PCH2 CH2 PMe2 ) (1) has been studied by cyclic voltammetry (CV) in acetonitrile and in dichloromethane in the presence of various substrates L (L=MeCN, trimethylphosphite, isocyanide). The oxidized species, [1-MeCN](PF6 )2 , [1-(P(OMe)3 )2 ](PF6 )2 and [1-(RNC)4 ](PF6 )2 (R=tert-butyl, xylyl), have been prepared and characterized by IR and NMR spectroscopies and, except [1-MeCN](PF6 )2 , by X-ray diffraction analysis. The crystallographic structures of the new FeII FeII complexes reveal that the association of one additional ligand (P(OMe)3 or RNC) occurs and, according to the nature of the substrates, further substitutions of one or three carbonyl groups, by P(OMe)3 or RNC, respectively, arise. Density functional theory (DFT) calculations have been performed to elucidate and discriminate, in each case, the mechanisms leading to the corresponding oxidized species. Moreover, the different degree of ligand substitution in the diiron core has been theoretically rationalized.

Influence of the Dithiolate Bridge on the Oxidative Processes of Diiron Models Related to the Active Site of [FeFe] Hydrogenases.

Electrochemical studies of [Fe2 (CO)4 (κ2 -dmpe)(µ-dithiolate)] (dithiolate=adtBn , pdt) and density functional theory (DFT) calculations reveal the striking influence of an amine functionality in the dithiolate bridge on their oxidative properties. [Fe2 (CO)4 (κ2 -dmpe)(µ-adtBn )] (1) undergoes two one-electron oxidation steps, with the first being partially reversible and the second irreversible. When the adtBn bridge is replaced with pdt, a shift of 60 mV towards more positive potentials is observed for the first oxidation whereas 290 mV separate the oxidation potentials of the two cations. Under CO, oxidation of azadithiolate compound 1 occurs according to an ECE process whereas an EC mechanism takes place for the propanedithiolate species 2. The dication species [1-CO]2+ resulting from the two-electron oxidation of 1 has been spectroscopically and structurally characterized. The molecular details underlying the reactivity of oxidized species have been explored by DFT calculations. The differences in the behaviors of 1 and 2 are mainly due to the presence, or not, of favored interactions between the dithiolate bridge and the diiron site depending on the redox states, FeI FeII or FeII FeII , of the complexes.

A diferrous dithiolate as a model of the elusive H(ox)(inact) state of the [FeFe] hydrogenases: an electrochemical and theoretical dissection of its redox chemistry.

The reduction of the Fe(II)Fe(II) complex [Fe2(CO)2{P(OMe)3}2(κ(2)-IMe-CH2-IMe)(µ-CO)(µ-pdt)](2+) (2P(2+); pdt = S(CH2)3S), which is a synthetic model of the H cluster of the [FeFe] hydrogenases in its inactive state, has been investigated electrochemically and theoretically (by density functional theory, DFT) in order to determine the mechanisms, intermediates, and products of the related processes. The electrochemical reduction of 2P(2+) occurs according to an ECE-type reaction where the intervening chemical step is the loss of one P(OMe)3 ligand. This outcome, which is based on cyclic voltammetric experiments, is strongly supported by DFT calculations that provide additional information on the intermediates and the energetics of the reactions involved. The electrochemical reoxidation of the neutral product of the reduction follows an EEC process where the chemical step is the binding of P(OMe)3 to a dicationic intermediate. DFT calculations reveal that this intermediate has an unusual geometry wherein one of the two C-H bonds of a side methylene from the pdt group forms an agostic interaction with one Fe center. This interaction is crucial to stabilize the 32e(-) diferrous center and concomitantly to preserve Fe(II) from binding of weakly coordinating species. Nonetheless, it could be displaced by a relatively stronger electron donor such as H2, which could be relevant for the design of new oxidation catalysts.

Acid-base control of hemilabile proton-responsive protecting devices in dimolybdenum, thiolate-bridged complexes.

Dimolybdenum thiolate-bridged complexes [Mo2Cp2(µ-SMe)2(µ-SCH2CH2E)] (E = O (2) or NH (4)) with a proton-dependent protecting device have been synthesized by reaction of [Mo2Cp2(µ-SMe)2(µ-Cl)2] (1) with SCH2CH2EH. The reactivity of the resultant quadruply bridged complexes with acid was investigated in the absence and in the presence of a potential ligand (N2, MeCN, RNC). While the protonation of complexes 2 and 4 under N2 in dichloromethane produced only the oxidized derivatives instead of the desired diazenido compound, ligand binding was observed in MeCN or in the presence of RNC (R = t-Bu, Xyl). Whereas acetonitrile loss from [Mo2Cp2(µ-SMe)2(µ-SCH2CH2OH)(MeCN)2](+) (8(+)) prevented the isolation and characterization of this species, the t-BuNC analogue (6(+)) could be characterized by an X-ray crystal structure. The electrochemistry of 2 and 2(+) was investigated in CH2Cl2 and in MeCN, both in the absence and in the presence of acid. While the addition of HBF4·Et2O to a dichloromethane solution of 2 only produced 2(+) (and presumably H2), 8(+) was the major product of the protonation in MeCN.

A new FeMo complex as a model of heterobimetallic assemblies in natural systems: Mössbauer and density functional theory investigations.

The design of the new FeMo heterobimetallic species [FeMo(CO)5(κ(2)-dppe)(µ-pdt)] is reported. Mössbauer spectroscopy and density functional theory calculations give deep insight into the electronic and structural properties of this compound.

Endothelium-selective activation of AMP-activated protein kinase prevents diabetes mellitus-induced impairment in vascular function and reendothelialization via induction of heme oxygenase-1 in mice.

BACKGROUND: Endothelial damage and dysfunction are crucial mediators that link diabetes mellitus with atherosclerotic cardiovascular disease. AMP-activated kinase (AMPK) has been implicated in regulation of both energy metabolism and vascular homeostasis. The present study investigated whether endothelium-selective activation of AMPK prevents diabetes mellitus-induced endothelial damage and vascular dysfunction by improving reendothelialization in mice. METHODS AND RESULTS: Transgenic mice with endothelium-selective expression of a constitutively active (CA) AMPK were generated and rendered diabetic by the injection of streptozotocin. Relaxation and reendothelialization of carotid arteries and circulating numbers of endothelial progenitor cells (EPCs) were examined after wire-induced denudation. Bone marrow-derived EPCs were isolated to monitor their in vivo and in vitro function. Compared with wild-type littermates, the CA-AMPK transgenic mice were resistant to diabetes mellitus-induced impairment in endothelium-dependent relaxation and reendothelialization of their injured carotid arteries. These changes in the transgenic mice were accompanied by increased mobilization of EPCs and enhanced incorporation of EPCs into injured blood vessels. Furthermore, EPCs from the transgenic mice exhibited augmented adhesion, migration, and tube formation capacities. At the molecular level, the expression of heme oxygenase (HO)-1 and the secretion of stromal cell-derived factor (SDF)-1α were upregulated in EPCs derived from the transgenic mice, whereas AMPK-mediated elevation of serum SDF-1α levels and improvements of EPC function and reendothelialization were all abrogated by pharmacological inhibition of heme oxygenase-1. CONCLUSIONS: Endothelium-specific AMPK activation is sufficient to protect against diabetes mellitus-induced aggravation of vascular injury by promoting EPC function and reendothelialization via upregulation of heme oxygenase-1 and SDF-1α.

New Fe(I) -Fe(I) complex featuring a rotated conformation related to the [2 Fe](H) subsite of [Fe-Fe] hydrogenase.

Rotated geometry: The first example of a dinuclear iron(I)-iron(I) complex featuring a fully rotated geometry related to the active site of [Fe-Fe] hydrogenase is reported.

Prevalence of abnormal Papanicolaou smears in female sex workers in Hong Kong.

OBJECTIVE. To investigate the prevalence of pre-cancerous uterine cervix lesions as detected in Papanicolaou (Pap) smears from female sex workers in Hong Kong. DESIGN. Retrospective analysis of laboratory records. SETTING. Private anatomical pathology laboratory, Hong Kong. PATIENTS. Female sex workers undergoing Pap smear examinations at two non-governmental organisations between 2006 and 2012. MAIN OUTCOME MEASURES. Detection of pre-cancerous uterine cervical conditions and their management. RESULTS. A total of 2697 satisfactory Pap smears from female sex workers were performed during the study period from 2006 to 2012. In these subjects, the point prevalence of low-grade squamous intraepithelial lesion and atypical squamous cells of unknown significance was 10.12% (compared with 3.92% for the general population during the same period), whereas that of high-grade squamous intraepithelial lesions and atypical squamous cells of unknown significance with or without high-grade intraepithelial lesions was 2.22% (compared with 0.54% in the general population). For both categories of lesions, the higher prevalence among female sex workers than in the general population was statistically significant. Most patients who had abnormal Pap smears received proper referrals and follow-up management according to recommended guidelines. CONCLUSIONS. Female sex workers in Hong Kong as a group had a significantly higher prevalence of abnormal Pap smears than the general population. Non-governmental organisations providing free-of-charge screening services to these women helped early detection and proper follow-up for those who had abnormal Pap smears, whilst also increasing their awareness of women's health issues.

Toll-like receptor-4 mediates obesity-induced non-alcoholic steatohepatitis through activation of X-box binding protein-1 in mice.

BACKGROUND: Non-alcoholic fatty liver disease is an obesity-related chronic liver disorder ranging from simple steatosis to non-alcoholic steatohepatitis (NASH), which may progress to liver fibrosis and cirrhosis. OBJECTIVE: Tto investigate the role of Toll-like receptor (TLR) 4 in mediating the transition from steatosis to inflammation. METHODS: ApoE(-/-)/TLR4(mut) mice and ApoE(-/-)/TLR4 wild-type mice (ApoE(-/-)/TLR4-WT) were generated by cross-breeding an ApoE-deficient (ApoE(-/-)) strain with TLR4-mutant (TLR4(mut)) mice, which were fed with high-fat, high-cholesterol (HFHC) diet to induce obesity. RESULTS: ApoE(-/-)/TLR4-WT mice fed with an HFHC diet for 12 weeks developed typical pathological features of NASH, which is associated with obesity and the metabolic syndrome. By contrast, ApoE(-/-)/TLR4(mut) mice lacking functional TLR4 were resistant to HFHC diet-induced liver inflammation and injury and were less susceptible to the diet-induced production of reactive oxygen species (ROS) and proinflammatory cytokines. In ApoE(-/-)/TLR4-WT mice, X-box binding protein-1 (XBP-1), a transcription factor involved in the unfolded protein responses, was activated in the liver by an HFHC diet, whereas XBP-1 activation was abrogated in ApoE(-/-)/TLR4(mut) mice. In primary rat Kupffer cells, endotoxin induced XBP-1 activation through ROS production, whereas siRNA-mediated knockdown of XBP-1 expression resulted in a marked attenuation in endotoxin-evoked NF-κB activation and cytokine production. Furthermore, adenovirus-mediated expression of dominant negative XBP-1 led to a significant attenuation in HFHC diet-induced liver inflammation and injury in mice. CONCLUSIONS: These findings support the key role of TLR4 in Kupffer cells in mediating the progression of simple steatosis to NASH, by inducing ROS-dependent activation of XBP-1.

Duplication of the internal carotid artery and segmental aplasia of the vertebral arteries.

The internal carotid artery mainly supplies the brain. As the internal carotid artery contributes to the formation of the cerebral arterial circle, its variations are relevant in imaging, interventional radiology, and surgery. Knowledge of these variations is important for vascular anastomosis in free flap reconstruction and in arterial ligatures for haemostasis. During a cadaveric cervical dissection, a duplicated left internal carotid artery was incidentally observed in the carotid triangle of the neck. The internal carotid branches were dissected up to their distribution to the brain. The two branches of the left internal carotid artery penetrated into the base of the skull by the carotid canal and the foramen magnum, respectively. With the right internal carotid artery, they formed the cerebral arterial circle. The basilar artery was formed by the branch of the left internal carotid artery entering the skull by the foramen magnum. The right internal carotid artery and the two branches of the left internal carotid gave rise to all of the arteries of the cerebral arterial circle. The vertebral arteries did not contribute to its formation. This duplication of the internal carotid arteries is rare, as the literature does not describe any case of vertebral artery aplasia replaced by an internal carotid artery.

Potential of Marine Strains of Pseudoalteromonas to Improve Resistance of Juvenile Sea Bass to Pathogens and Limit Biofilm Development.

The European sea bass (Dicentrarchus labrax), one of the most produced marine fish species in Europe, is acutely vulnerable to multiple infectious hazards. In this study, we investigated the potential probiotic effect of some marine Pseudoalteromonas bacterial strains against two major pathogens of this species, Vibrio harveyi and the nervous necrosis virus (NNV), and examined their antibiofilm effect. Impregnation phase was done by repeated immersion of juvenile's sea bass during 8 to 12 weeks in seawater containing the probiotic candidates at a concentration of 106 CFU/mL. Four candidates were tested: (1) a combination of two strains producing antimicrobial compounds, hCg-42 and hOe-125; (2) strain 3J6, with known antibiofilm properties; (3) strain RA15, from the same genus, but with no identified probiotic effect; and (4) a control group without probiotics. At the end of the impregnation phase, fish underwent an infection challenge with V. harveyi or with a pathogenic strain of NNV and mortality was monitored. For the V. harveyi challenge, improved survival rates of 10 and 25% were obtained for the RA15 and the mix hCg-42 + hOe-125-impregnated groups, respectively. For the NNV challenge, no significant benefic effect of the probiotics on infection kinetics or cumulative mortality was observed. At the end of the impregnation phase, the maximal thickness of biofilm was significantly lower in the 3J6, double strain, and RA15 groups, compared with the non-impregnated control group. This study highlights the interesting probiotic potential of marine bacteria to limit mortalities induced by bacterial pathogens as well as biofilm development.

Electrochemical and theoretical investigations of the role of the appended base on the reduction of protons by [Fe2(CO)4(κ2-PNP(R)(µ-S(CH2)3S] (PNP(R) ={Ph2PCH2}2NR, R=Me, Ph).

The behavior of [Fe(2)(CO)(4)(κ(2)-PNP(R))(µ-pdt)] (PNP(R) =(Ph(2)PCH(2))(2)NR, R=Me (1), Ph (2); pdt=S(CH(2))(3)S) in the presence of acids is investigated experimentally and theoretically (using density functional theory) in order to determine the mechanisms of the proton reduction steps supported by these complexes, and to assess the role of the PNP(R) appended base in these processes for different redox states of the metal centers. The nature of the R substituent of the nitrogen base does not substantially affect the course of the protonation of the neutral complex by CF(3)SO(3)H or CH(3)SO(3)H; the cation with a bridging hydride ligand, 1 µH(+) (R=Me) or 2 µH(+) (R=Ph) is obtained rapidly. Only 1 µH(+) can be protonated at the nitrogen atom of the PNP chelate by HBF(4)·Et(2)O or CF(3)SO(3)H, which results in a positive shift of the proton reduction by approximately 0.15 V. The theoretical study demonstrates that in this process, dihydrogen can be released from a η(2)-H(2) species in the Fe(I)Fe(II) state. When R=Ph, the bridging hydride cation 2 µH(+) cannot be protonated at the amine function by HBF(4)·Et(2)O or CF(3)SO(3)H, and protonation at the N atom of the one-electron reduced analogue is also less favored than that of a S atom of the partially de-coordinated dithiolate bridge. In this situation, proton reduction occurs at the potential of the bridging hydride cation, 2 µH(+). The rate constants of the overall proton reduction processes are small for both complexes 1 and 2 (k(obs) ≈4-7 s(-1)) because of the slow intramolecular proton migration and H(2) release steps identified by the theoretical study.

Oxidatively induced reactivity of [Fe2(CO)4(κ2-dppe)(µ-pdt)]: an electrochemical and theoretical study of the structure change and ligand binding processes.

The one-electron oxidation of the diiron complex [Fe(2)(CO)(4)(κ(2)-dppe)(µ-pdt)] (1) (dppe = Ph(2)PCH(2)CH(2)PPh(2); pdt = S(CH(2))(3)S) has been investigated in the absence and in the presence of P(OMe)(3), by both electrochemical and theoretical methods, to shed light on the mechanism and the location of the oxidatively induced structure change. While cyclic voltammetric experiments did not allow to discriminate between a two-step (EC) and a concerted, quasi-reversible (QR) process, density functional theory (DFT) calculations favor the first option. When P(OMe)(3) is present, the one-electron oxidation produces singly and doubly substituted cations, [Fe(2)(CO)(4-n){P(OMe)(3)}(n)(κ(2)-dppe)(µ-pdt)](+) (n = 1: 2(+); n = 2: 3(+)) following mechanisms that were investigated in detail by DFT. Although the most stable isomer of 1(+) and 2(+) (and 3(+)) show a rotated Fe(dppe) center, binding of P(OMe)(3) occurs at the neighboring iron center of both 1(+) and 2(+). The neutral compound 3 was obtained by controlled-potential reduction of the corresponding cation, while 2 was quantitatively produced by reaction of 3 with CO. The CO dependent conversion of 3 into 2 as well as the 2(+) ↔ 3(+) interconversion were examined by DFT.

Contribution of the dorsal subiculum to memory for temporal order and novelty detection using objects, odors, or spatial locations in the rat.

The contribution of the dorsal subiculum (DS) to memory for temporal order and novelty detection was assessed using a spontaneous exploration paradigm with objects (visual/tactile stimuli), odors, or spatial locations (Hunsaker, Fieldsted, Rosenberg, & Kesner, 2008). Rats with selective excitotoxic lesions of the DS were compared to sham-operated rats (SHAM) in the two exploration tests. In temporal order tests, two previously explored stimuli were presented and normal rats typically show a preference for exploring the stimulus that was first explored compared to the other stimulus. In novelty detection tests, a familiar and a new stimulus were presented and normal rats typically have a preference for exploring new stimuli. In temporal order tests, results indicated that Group SHAM explored significantly more the first than the last stimulus they met when the stimuli were odors or objects. In addition, SHAM rats predictably displayed a significant preference for the new stimulus in the novelty detection tests with objects, odors, and spatial locations. Group DS did not differ from controls on the temporal order and the novelty detection tests with objects or odors. However, on the novelty detection test with spatial locations, Group DS differed from Group SHAM. These results suggest that the DS is necessary for the memory of spatial locations but not of objects and odors.