The interactome of metabolic enzyme carbonic anhydrase IX reveals novel roles in tumor cell migration and invadopodia/MMP14-mediated invasion

Carbonic anhydrase IX (CAIX) is a hypoxia inducible factor 1-induced, cell surface pH regulating enzyme with an established role in tumor progression and clinical outcome. However, the molecular basis of CAIX-mediated tumor progression remains unclear. Here, we have utilized proximity dependent biotinylation (BioID) to map the CAIX ‘interactome’ in breast cancer cells in order to identify physiologically relevant CAIX-associating proteins with potential roles in tumor progression. High confidence proteins identified include metabolic transporters, β1 integrins, integrin-associated protein CD98hc and matrix metalloprotease 14 (MMP14). Biochemical studies validate the association of CAIX with α2β1 integrin, CD98hc and MMP14, and immunofluorescence microscopy demonstrates colocalization of CAIX with α2β1 integrin and MMP14 in F-actin/cofilin-positive lamellipodia/pseudopodia, and with MMP14 to cortactin/Tks5-positive invadopodia. Modulation of CAIX expression and activity results in significant changes in cell migration, collagen degradation and invasion. Mechanistically, we demonstrate that CAIX associates with MMP14 through potential phosphorylation residues within its intracellular domain, and that CAIX enhances MMP14-mediated collagen degradation by directly contributing hydrogen ions required for MMP14 catalytic activity. These findings establish hypoxia-induced CAIX as a novel metabolic component of cellular migration and invasion structures, and provide new mechanistic insights into its role in tumor cell biology.

Dimorphism by Singularity Theory in a Model for River Ecology

Geritz, Gyllenberg, Jacobs, and Parvinen show that two similar species can coexist only if their strategies are in a sector of parameter space near a nondegenerate evolutionarily singular strategy. We show that the dimorphism region can be more general by using the unfolding theory of Wang and Golubitsky near a degenerate evolutionarily singular strategy. Specifically, we use a PDE model of river species as an example of this approach. Our finding shows that the dimorphism region can exhibit various different forms that are strikingly different from previously known results in adaptive dynamics.

Patient-activation and guideline-concordant pharmacological treatment after bone density testing: the PAADRN randomized controlled trial

Patients often do not know or understand their bone density test results, and pharmacological treatment rates are low. In a clinical trial of 7749 patients, we used a tailored patient-activation result letter accompanied by a bone health brochure to improve appropriate pharmacological treatment. Treatment rates, however, did not improve.

INTRODUCTION

Patients often do not know or understand their dual-energy x-ray absorptiometry (DXA) test results, which may lead to suboptimal care. We tested whether usual care augmented by a tailored patient-activation DXA result letter accompanied by an educational brochure would improve guideline-concordant pharmacological treatment compared to usual care only.

METHODS

We conducted a randomized, controlled, double-blinded, pragmatic clinical trial at three health care centers in the USA. We randomized 7749 patients ≥50 years old and presenting for DXA between February 2012 and August 2014. The primary clinical endpoint at 12 and 52 weeks post-DXA was receiving guideline-concordant pharmacological treatment. We also examined four of the steps along the pathway from DXA testing to that clinical endpoint, including (1) receiving and (2) understanding their DXA results and (3) having subsequent contact with their provider and (4) discussing their results and options.

RESULTS

Mean age was 66.6 years, 83.8 % were women, and 75.3 % were non-Hispanic whites. Intention-to-treat analyses revealed that guideline-concordant pharmacological treatment was not improved at either 12 weeks (65.1 vs. 64.3 %, p = 0.506) or 52 weeks (65.2 vs. 63.8 %, p = 0.250) post-DXA, even though patients in the intervention group were more likely (all p < 0.001) to recall receiving their DXA results letter at 12 weeks, correctly identify their results at 12 and 52 weeks, have contact with their provider at 52 weeks, and have discussed their results with their provider at 12 and 52 weeks.

CONCLUSION

A tailored DXA result letter and educational brochure failed to improve guideline-concordant care in patients who received DXA.

Predictors of bone mineral density testing among older women on Medicare

Although dual-energy X-ray absorptiometry (DXA) is recommended for all women ≥65 and is covered by Medicare, 40 % of women on Medicare report never having had a DXA. In a longitudinal cohort of 3492 women followed for two decades, we identified several risk factors that should be targeted to improve DXA testing rates.

INTRODUCTION

DXA is used to measure bone mineral density, screen for osteoporosis, and assess fracture risk. DXA is recommended for all women ≥65 years old. Although Medicare covers DXA every 24 months for women, about 40 % report never having had a DXA test, and little is known from prospective cohort studies about which subgroups of women have low use rates and should be targeted for interventions. Our objective was to identify predictors of DXA use in a nationally representative cohort of women on Medicare.

METHODS

We used baseline and biennial follow-up survey data (1993-2012) for 3492 women ≥70 years old from the nationally representative closed cohort known as the Survey on Assets and Health Dynamics among the Oldest Old (AHEAD). The survey data for these women were then linked to their Medicare claims (1991-2012), yielding 17,345 person years of observation. DXA tests were identified from the Medicare claims, and Cox proportional hazard regression models were used with both fixed and time-dependent predictors from the survey interviews including demographic characteristics, socioeconomic factors, health status, health habits, and the living environment.

RESULTS

DXA use was positively associated with being Hispanic American, better cognition, higher income, having arthritis, using other preventative services, and living in Florida or other southern states. DXA use was negatively associated with age, being African-American, being overweight or obese, having mobility limitations, and smoking.

CONCLUSIONS

Interventions to increase DXA use should target the characteristics that were observed here to be negatively associated with such screening.

Rare Variants in LAMA5 Gene associated with FLT4 and FOXC2 Mutations in Primary Lymphedema May Contribute to Severity

Mutations in the Fms-related tyrosine kinase 4 (FLT4) and forkhead box protein C2 (FOXC2) genes cause Milroy disease (MD) and lymphedema-distichiasis syndrome (LDS), respectively, but the mechanism underlying disease pathology remains unclear. Applying whole-exome sequencing to two families with MD, one LDS family, and one sporadic LDS case, we identified four rare variants in the laminin subunit alpha-5 gene (LAMA5) in subjects carrying novel and known missense FLT4 mutations and a 7-bp duplication and 1-bp insertion in FOXC2. Phenotyping was expanded in some individuals using magnetic resonance lymphangiography, indiocyanine green fluorescence lymphography, and immunofluorescent lymphatic staining of skin tissue. Skin lymphatic staining showed the existence of dermal lymphatic vasculature in the MD case. Significant lymphatic dysfunction was observed in both MD and LDS patients. In the MD patient, tortuous lymphatics in the dorsum of the foot were slowly enhanced on indocyanine green fluorescent lymphography (ICG) imaging. Dilated lymph collectors with disruption and lymph leakage were observed in the familial LDS case on magnetic resonance lymphangiography (MRL). Numerous tortuous lymph collectors were visualized along the entire length of affected lower limbs on MRL imaging, and retrograde lymph flow was observed in the lymph collectors during ICG lymphography in the isolated LDS case. The finding of rare LAMA5 variants together with FLT4 and FOXC2 mutations suggests that these mutations may be co-responsible for these disorders and most likely interfere with the function of lymphatics. Further, larger studies are needed to confirm these results.

Evolution of natal dispersal in spatially heterogenous environments

Understanding the evolution of dispersal is an important issue in evolutionary ecology. For continuous time models in which individuals disperse throughout their lifetime, it has been shown that a balanced dispersal strategy, which results in an ideal free distribution, is evolutionary stable in spatially varying but temporally constant environments. Many species, however, primarily disperse prior to reproduction (natal dispersal) and less commonly between reproductive events (breeding dispersal). These species include territorial species such as birds and reef fish, and sessile species such as plants, and mollusks. As demographic and dispersal terms combine in a multiplicative way for models of natal dispersal, rather than the additive way for the previously studied models, we develop new mathematical methods to study the evolution of natal dispersal for continuous-time and discrete-time models. A fundamental ecological dichotomy is identified for the non-trivial equilibrium of these models: (i) the per-capita growth rates for individuals in all patches are equal to zero, or (ii) individuals in some patches experience negative per-capita growth rates, while individuals in other patches experience positive per-capita growth rates. The first possibility corresponds to an ideal-free distribution, while the second possibility corresponds to a "source-sink" spatial structure. We prove that populations with a dispersal strategy leading to an ideal-free distribution displace populations with dispersal strategy leading to a source-sink spatial structure. When there are patches which cannot sustain a population, ideal-free strategies can be achieved by sedentary populations, and we show that these populations can displace populations with any irreducible dispersal strategy. Collectively, these results support that evolution selects for natal or breeding dispersal strategies which lead to ideal-free distributions in spatially heterogenous, but temporally homogenous, environments.

A Novel Micro Wall Slip Model Based on Chain Length and Temperature

A micro chain length and temperature (MCLT) wall slip model of polymer was developed on the basis of chain length and temperature. The effectiveness and accuracy of the MCLT slip model were verified through a micro-square-column filling rate experiment for Polypropylene (PP) material and a micro-square-column pressure difference experiment for Polystyrene (PS) material. The difference between the simulated data of the MCLT slip model and the experimental data decreased with decreasing feature size. The accuracy of the MCLT slip model was enhanced by decreasing the feature size. When the feature size was decreased to 200 μm, the maximum deviation between the simulated filling rate by the MCLT slip model and the experimental result was 8.67 %. Moreover, under different shearing rates, the simulated pressure drop by the MCLT slip model was closer to the experimental result than that by the conventional slip model. The micro-scale flow characteristics of the melt were also explored using the MCLT slip model. Melt flow velocity decreased from the center of the micro-channel to the wall, and the wall slip phenomenon was beneficial to the melt flow.

Peroxisome proliferator-activated receptorβ/δ activation is essential for modulating p-Foxo1/Foxo1 status in functional insulin-positive cell differentiation

Peroxisome proliferator-activated receptors (PPARs) participate in energy homeostasis and play essential roles in diabetes therapy through their effects on non-pancreas tissues. Pathological microenvironment may influence the metabolic requirements for the maintenance of stem cell differentiation. Accordingly, understanding the mechanisms of PPARs on pancreatic β-cell differentiation may be helpful to find the underlying targets of disrupted energy homeostasis under the pancreatic disease condition. PPARs are involved in stem cell differentiation via mitochondrial oxidative phosphorylation, but the subtype member activation and the downstream regulation in functional insulin-positive (INS⁺) cell differentiation remain unclear. Here, we show a novel role of PPARβ/δ activation in determining INS⁺ cell differentiation and functional maturation. We found PPARβ/δ expression selectively upregulated in mouse embryonic pancreases or stem cells-derived INS⁺ cells at the pancreatic mature stage in vivo and in vitro. Strikingly, given the inefficiency of generating INS⁺ cells in vitro, PPARβ/δ activation displayed increasing mouse and human ES cell-derived INS⁺ cell numbers and insulin secretion. This phenomenon was closely associated with the forkhead box protein O1 (Foxo1) nuclear shuttling, which was dependent on PPARβ/δ downstream PI3K/Akt signaling transduction. The present study reveals the essential role of PPARβ/δ activation on p-Foxo1/Foxo1 status, and in turn, determining INS⁺ cell generation and insulin secretion via affecting pancreatic and duodenal homeobox-1 expression. The results demonstrate the underlying mechanism by which PPARβ/δ activation promotes functional INS⁺ cell differentiation. It also provides potential targets for anti-diabetes drug discovery and hopeful clinical applications in human cell therapy.

Lower free testosterone level is correlated with left ventricular diastolic dysfunction in asymptomatic middle-aged men with type 2 diabetes mellitus

AIMS

Low testosterone (T) level is associated with cardiovascular risk factors. However, the relationship between T level and heart function in asymptomatic men with type 2 diabetes mellitus (T2DM) is unknown.

METHODS

A total of 325 men were recruited who had no history, symptoms, or signs of heart disease.

RESULTS

T2DM had significantly lower free T (FT) levels than those with normal glucose metabolism (NGM) (428 ± 38 pmol/l vs. 444 ± 38 pmol/l, p = 0.0002), and had an increased risk of LVDD (66.1% vs. 31.8%). There was a significant difference in FT level between subjects with and without LVDD among those with T2DM (421 ± 37 pmol/l vs. 442 ± 40 pmol/l, p = 0.0007), but not among those with NGM (439 ± 37 pmol/l vs. 447 ± 39 pmol/l, p = 0.247) or in the group overall (426 ± 38 pmol/l vs. 445 ± 38 pmol/l, p = 0.156). Lower FT level was significantly associated with LVDD [univariate odds ratio (OR) = 0.63, p = 0.032; multivariate OR = 0.71, p = 0.039]. Receiver operating characteristic curve analysis of the usefulness of FT level for predicting LVDD showed an area under the curve (AUC) of 0.85 for T2DM (p < 0.001) and 0.66 for NGM (p < 0.05). FT level had a high predictive value for LVDD in T2DM (83% for FT < 414 pmol/l), but a low predictive value in NGM (61% for FT < 423 pmol/l). Comparison of the AUCs showed that FT level was more strongly correlated with LVDD in T2DM than in NGM.

CONCLUSIONS

Lower FT level is correlated with LVDD in asymptomatic middle-aged men with T2DM.

Evolution of dispersal in closed advective environments

We study a two-species competition model in a closed advective environment, where individuals are exposed to unidirectional flow (advection) but no individuals are lost through the boundary. The two species have the same growth and advection rates but different random dispersal rates. The linear stability analysis of the semi-trivial steady state suggests that, in contrast to the case without advection, slow dispersal is generally selected against in closed advective environments. We investigate the invasion exponent for various types of resource functions, and our analysis suggests that there might exist some intermediate dispersal rate that will be selected. When the diffusion and advection rates are small and comparable, we determine criteria for the existence and multiplicity of singular strategies and evolutionarily stable strategies. We further show that every singular strategy is convergent stable.

Prognostic value of the neutrophil-to-lymphocyte ratio in patients with acute-on-chronic liver failure

OBJECTIVES

The neutrophil-to-lymphocyte ratio (NLR) is a novel inflammation index that has been shown to independently predict poor clinical outcomes. We aimed to evaluate the role of NLR in the prediction of 3-month mortality in patients with acute-on-chronic liver failure (AoCLF).

METHODS

One hundred and twenty-seven patients, including 46 patients with chronic hepatitis B (CHB), 81 with AoCLF and 58 healthy controls (HCs), were enrolled in the study. All patients were followed up for 4 months. The primary end-point was in-hospital mortality at the end of 90 days. A blood sample was collected for all subjects at admission to examine liver function, renal function, international normalised ratio, C-reactive protein and neutrophil and lymphocyte counts, and NLRs were calculated. A total of six clinical chemistry and biochemical variables were analysed for potential associations with outcomes using Cox proportional hazards and multiple regression models.

RESULTS

Acute-on-chronic liver failure patients had significantly higher NLRs on admission compared with HCs and CHB patients (all p = 0.001). Patients with elevated NLRs were associated with increased severity of liver disease and 3-month mortality rates. According to multivariate analysis, only NLR was an independent predictor for mortality (p = 0.025).

CONCLUSIONS

The NLR measured at admission can serve as an independent predictor for 3-month mortality rate in AoCLF patients.

Design of a high voltage stimulator chip for a stroke rehabilitation system

This paper describes the design of an 8-channel high voltage stimulator chip for rehabilitation of stroke patients through surface stimulation, which requires high stimulation currents and high compliance voltage. The chip gets stimulation control data through its Serial Peripheral Interface (SPI), and can accordingly generate biphasic stimulation currents with different amplitudes, duration, frequencies and polarities independently for each channel. The current driver is implemented with thick oxide devices with a supply voltage up to 90V. The chip is designed in a 0.35εm X-FAB high voltage process.

Pharmacokinetics, safety, and monotherapy antiviral activity of GSK1265744, an HIV integrase strand transfer inhibitor

BACKGROUND

GSK1265744 is an HIV integrase strand transfer inhibitor selected for clinical development.

OBJECTIVE

This first-time-in-human and phase IIa investigation assessed GSK1265744 antiviral activity, pharmacokinetics, safety, and tolerability in healthy and HIV-1-infected subjects.

METHODS

This double-blind, placebo-controlled study consisted of a dose escalation of single (part A) and multiple (part B) oral doses in 48 healthy subjects and an oral dose (part C) in 11 HIV-1-infected subjects. In part A, 2 cohorts of 9 subjects received either 5 and 25 mg or 10 and 50 mg. In part B, 3 cohorts of 10 subjects received 5, 10, or 25 mg once daily for 14 days. In part C and the phase IIa study, subjects received 5 or 30 mg once daily for 10 days.

RESULTS

Dose-proportional increases in drug exposure were observed in healthy and HIV-1-infected subjects. In healthy subjects, pharmacokinetic variability was low following single or repeat dosing (coefficient of variation, 13%-34% and 15%-23%, respectively). Mean plasma half-life was 31.5 hours. GSK1265744 monotherapy significantly reduced plasma HIV-1 RNA from baseline to day 11 in HIV-1-infected subjects receiving 5 or 30 mg versus placebo (P < .001); mean decrease was 2.2 to 2.3 log10 copies/mL, respectively. Study drug was generally well tolerated with no clinically relevant trends in laboratory values, vital signs, or electrocardiograms.

CONCLUSIONS

GSK1265744 was well tolerated in healthy and HIV-1-infected subjects. Results demonstrate once-daily doses of 5 or 30 mg exceeded minimum target therapeutic concentrations and produced a significant reduction in plasma HIV-1 RNA viral load.

Abstract P3-01-04: Obesity induces functional transcriptomic changes enhancing the cancer hallmarks of estrogen receptor-positive breast cancer

Obesity increases the risk of cancer death among postmenopausal women with estrogen receptor-positive (ER+) breast cancer, but the direct evidence for the mechanisms is lacking. The purpose of this study is to demonstrate direct evidence for the mechanisms mediating this epidemiologic phenomenon. Transcriptomic profiles of pretreatment biopsies from a prospective cohort of 137 ER+ breast cancer patients were analyzed. A transgenic and an orthotopic/syngeneic obese mouse models were created to phenocopy obese patients and evaluate the effect of obesity on breast carcinogenesis and tumor progression, and to explore further direct mechanisms. Functional transcriptomic analysis of untreated human ER+ breast cancer revealed that obesity was associated with increased insulin signaling among others. Many of the functional changes in obese patients were linked to cancer hallmarks. Obese mouse models recapitulated the functional transcriptomic landscape of obesity-associated changes seen in human ER+ breast cancer and demonstrated the role of the Akt/mTOR pathway in obesity-induced breast carcinogenesis and tumor progression. Functional transcriptomic analysis identified 85 biological functions common to humans and mice. An in vitro co-culture model revealed that adipocyte-secreted adipokines (e.g., TIMP-1) regulate adipocyte-induced breast cancer cell proliferation and invasion. The human transcriptomic data provided direct evidence for the roles of hyperinsulinemia, estrogen signaling, adipokine secretion, and inflammation in the link between obesity and ER+ breast cancer. Our animal experiments provide strong evidence for the causal relationship between obesity and accelerated carcinogenesis and cancer progression and for potential therapeutic interventions by blocking these signaling pathways.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-01-04.

Evolution of dispersal in open advective environments

We consider a two-species competition model in a one-dimensional advective environment, where individuals are exposed to unidirectional flow. The two species follow the same population dynamics but have different random dispersal rates and are subject to a net loss of individuals from the habitat at the downstream end. In the case of non-advective environments, it is well known that lower diffusion rates are favored by selection in spatially varying but temporally constant environments, with or without net loss at the boundary. We consider several different biological scenarios that give rise to different boundary conditions, in particular hostile and "free-flow" conditions. We establish the existence of a critical advection speed for the persistence of a single species. We derive a formula for the invasion exponent and perform a linear stability analysis of the semi-trivial steady state under free-flow boundary conditions for constant and linear growth rate. For homogeneous advective environments with free-flow boundary conditions, we show that populations with higher dispersal rate will always displace populations with slower dispersal rate. In contrast, our analysis of a spatially implicit model suggest that for hostile boundary conditions, there is a unique dispersal rate that is evolutionarily stable. Nevertheless, both scenarios show that unidirectional flow can put slow dispersers at a disadvantage and higher dispersal rate can evolve.

Sustained reduction of alloantibody secreting plasma cells and donor specific antibody with proteasome inhibition in mice

The long-lived plasma cells, which develop after alloantigen sensitization, produce donor specific alloantibodies (DSAs) that generate a positive serum cross-match and preclude transplantation. Bortezomib, a proteasome inhibitor, is being investigated in clinical desensitization protocols, however preclinical studies in a transplant model are nonexistent. We hypothesized that sustained treatment with only a proteasome inhibitor would eliminate plasma cells and reduce DSA over time. Cardiac allografts were transplanted into murine recipients. Eight weeks after allograft rejection the proteasome inhibitor, bortezomib, was injected intravenously twice weekly for 60 days. Serum alloantibody responses were assayed using flow cross-match. Total and alloreactive plasma cell numbers were enumerated using flow cytometry and ELISPOT. All recipients of cardiac allografts rejected their graft promptly within 16 days and demonstrated alloantibody by flow cross-match. DSA was sustained in the control mice while mice treated with bortezomib had sustained elimination of DSA and a marked reduction in plasma cell population. Also, bortezomib was associated with an increased level of BLyS. Within a murine model, proteasome inhibition can eliminate alloantibody secreting plasma cells, and reduce alloantibody. Cessation of bortezomib is not associated with return of DSA.

p53 protein accumulation and genetic alterations in human giant cell tumors of bone (osteoclastomas)

Inactivation of tumor suppressor genes represents a critical determinant in the development of a large proportion of human cancers. The tumor suppressor gene p53 is the most frequently altered gene in human cancers. In the present study, p53 protein accumulation, gene mutation and the association between p53 alteration and clinicopathological parameters was analyzed in 29 giant cell tumors of bone. p53 overexpression was detected by immunohistochemistry in 23 of 29 (79%) primary tumors but not in adjacent bone tissue. p53 gene mutations in exons 5-8 were detected in 15 of 29 (52%) of the tumors by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. In 15 (52%) of 29 patient specimens, p53 immunostaining and mutations in exons 5-8 were concordant. Eleven (38%) of 29 tumors overexpressed p53 in the absence of mutations in exons 5-8. No significant association between p53 alterations and clinicopathological parameters was found. The present study represents the first report to assess p53 protein content and gene mutation in a substantial number of giant cell tumors of bone and suggests that p53 alterations play an important role in the development of this neoplasm.

A model of sexual selection and female use of refuge in a coercive mating system

In many non-monogamous systems, males invest less in progeny than do females. This leaves males with higher potential rates of reproduction, and a likelihood of sexual conflict, including, in some systems, coercive matings. If coercive matings are costly, the best female strategy may be to avoid male interaction. We present a model that demonstrates female movement in response to male harassment as a mechanism to lower the costs associated with male coercion, and the effect that female movement has on selection in males for male harassment. We found that, when females can move from a habitat patch to a refuge to which males do not have access, there may be a selection for either high, or low harassment male phenotype, or both, depending on the relationship between the harassment level of male types in the population and a threshold level of male harassment. This threshold harassment level depends on the relative number of males and females in the population, and the relative resource values of the habitat; the threshold increases as the sex ratio favours females, and decreases with the value of the refuge patch or total population. Our model predicts that selection will favour the harassment level that lies closest to this threshold level of harassment, and differing harassment levels will coexist within the population only if they lie on the opposite sides of the threshold harassment. Our model is consistent with empirical results suggesting that an intermediate harassment level provides maximum reproductive fitness to males when females are mobile.

On several conjectures from evolution of dispersal

We address several conjectures raised in Cantrell et al. [Evolution of dispersal and ideal free distribution, Math. Biosci. Eng. 7 (2010), pp. 17-36 [ 9 ]] concerning the dynamics of a diffusion-advection-competition model for two competing species. A conditional dispersal strategy, which results in the ideal free distribution of a single population at equilibrium, was found in Cantrell et al. [ 9 ]. It was shown in [ 9 ] that this special dispersal strategy is a local evolutionarily stable strategy (ESS) when the random diffusion rates of the two species are equal, and here we show that it is a global ESS for arbitrary random diffusion rates. The conditions in [ 9 ] for the coexistence of two species are substantially improved. Finally, we show that this special dispersal strategy is not globally convergent stable for certain resource functions, in contrast with the result from [ 9 ], which roughly says that this dispersal strategy is globally convergent stable for any monotone resource function.

Investigating Catalytic Properties of Composite Nanoparticle Assemblies

We present herein recent findings of an investigation of catalyst assembly and activation using metallic nanoparticles encapsulated with organic monolayers. Gold nanocrystals (2∼5 nm) encapsulated with thiolate monolayers assembled on electrode surfaces, were found to be catalytically active towards electrooxidation of CO and MeOH upon activation. The activation involved partial removal of the encapsulating thiolates and the formation of surface oxygenated species. A polymeric film was also used as a substrate for the assembly of the nanoparticle catalysts. When the polymer matrix was doped with small amounts of Pt, a remarkable catalytic activity was observed. These catalysts were characterized utilizing cyclic voltammetry and atomic force microscopy.

Evolution of dispersal and the ideal free distribution

A general question in the study of the evolution of dispersal is what kind of dispersal strategies can convey competitive advantages and thus will evolve. We consider a two species competition model in which the species are assumed to have the same population dynamics but different dispersal strategies. Both species disperse by random diffusion and advection along certain gradients, with the same random dispersal rates but different advection coefficients. We found a conditional dispersal strategy which results in the ideal free distribution of species, and show that it is a local evolutionarily stable strategy. We further show that this strategy is also a global convergent stable strategy under suitable assumptions, and our results illustrate how the evolution of conditional dispersal can lead to an ideal free distribution. The underlying biological reason is that the species with this particular dispersal strategy can perfectly match the environmental resource, which leads to its fitness being equilibrated across the habitats.