Molecular Orientation and Energy Transfer Dynamics of a Metal Oxide Bound Self-Assembled Trilayer.

Self-assembly of molecular multilayers via metal ion linkages has become an important strategy for interfacial engineering of metalloid and metal oxide (MOx) substrates, with applications in numerous areas, including energy harvesting, catalysis, and chemical sensing. An important aspect for the rational design of these multilayers is knowledge of the molecular structure-function relationships. For example, in a multilayer composed of different chromophores in each layer, the molecular orientation of each layer, both relative to the adjacent layers and the substrate, influences the efficiency of vectorial energy and electron transfer. Here, we describe an approach using UV-vis attenuated total reflection (ATR) spectroscopy to determine the mean dipole tilt angle of chromophores in each layer in a metal ion-linked trilayer self-assembled on indium-tin oxide. To our knowledge, this is the first report demonstrating the measurement of the orientation of three different chromophores in a single assembly. The ATR approach allows the adsorption of each layer to be monitored in real-time, and any changes in the orientation of an underlying layer arising from the adsorption of an overlying layer can be detected. We also performed transient absorption spectroscopy to monitor interlayer energy transfer dynamics in order to relate structure to function. We found that near unity efficiency, sub-nanosecond energy transfer between the third and second layer was primarily dictated by the distance between the chromophores. Thus, in this case, the orientation had minimal impact at such proximity.

Molecular Orientation of -PO3H2 and -COOH Functionalized Dyes on TiO2, Al2O3, ZrO2, and ITO: A Comparative Study.

Modification of transparent metal oxide (MOx) surfaces with organic monolayers is widely employed to tailor the properties of interfaces in organic electronic devices, and MOx substrates modified with light-absorbing chromophores are a key component of dye-sensitized solar cells (DSSCs). The effects of an organic modifier on the performance of a MOx-based device are frequently assessed by performing experiments on model monolayer|MOx interfaces, where an "inert" MOx (e.g., Al2O3) is used as a control for an "active" MOx (e.g., TiO2). An underlying assumption in these studies is that the structure of the MOx-monolayer complex is similar between different metal oxides. The validity of this assumption was examined in the present study. Using UV-Vis attenuated total reflection spectroscopy, we measured the mean dipole tilt angle of 4,4'-(anthracene-9,10-diyl)bis(4,1-phenylene)diphosphonic acid (A1P) adsorbed on indium tin oxide (ITO), TiO2, ZrO2, and Al2O3. When the surface roughness of the MOx substrate and the surface coverage (𝛤) of the A1P film were constant, the molecular orientation of A1P was the same on these substrates. The study was extended to 4,4'-(anthracene-9,10-diyl)bis(4,1-phenylene)dicarboxylic acid (A1C) adsorbed on the same group of MOx substrates. The mean tilt angle of A1C and A1P films on ITO was the same, which is likely due the intermolecular interactions resulting from the high and approximately equal 𝛤 of both films. Comparing A1C films at the same 𝛤 on TiO2 and Al2O3 having the same surface roughness, there was no difference in the mean tilt angle. MD simulations of A1C and A1P on TiO2 produced nearly identical tilt angle distributions, which supports the experimental findings. This study provides first experimental support for the assumption that the structure of the MOx-modifer film is the same on an "active" substrate vs. a "inert" control substrate.

Nanomechanical Properties of Artificial Lipid Bilayers Composed of Fluid and Polymerizable Lipids.

Polymerization enhances the stability of a planar supported lipid bilayer (PSLB) but it also changes its chemical and mechanical properties, attenuates lipid diffusion, and may affect the activity of integral membrane proteins. Mixed bilayers composed of fluid lipids and poly(lipids) may provide an appropriate combination of polymeric stability coupled with the fluidity and elasticity needed to maintain the bioactivity of reconstituted receptors. Previously (Langmuir, 2019, 35, 12483-12491) we showed that binary mixtures of the polymerizable lipid bis-SorbPC and the fluid lipid DPhPC form phase-segregated PSLBs composed of nanoscale fluid and poly(lipid) domains. Here we used atomic force microscopy (AFM) to compare the nanoscale mechanical properties of these binary PSLBs with single-component PSLBs. The elastic (Young's) modulus, area compressibility modulus, and bending modulus of bis-SorbPC PSLBs increased upon polymerization. Before polymerization, breakthrough events at forces below 5 nN were observed, but after polymerization, the AFM tip could not penetrate the PSLB up to an applied force of 20 nN. These results are attributed to the polymeric network in poly(bis-SorbPC), which increases the bilayer stiffness and resists compression and bending. In binary DPhPC/poly(bis-SorbPC) PSLBs, the DPhPC domains are less stiff, more compressible, and are less resistant to rupture and bending compared to pure DPhPC bilayers. These differences are attributed to bis-SorbPC monomers and oligomers present in DPhPC domains that disrupt the packing of DPhPC molecules. In contrast, the poly(bis-SorbPC) domains are stiffer and less compressible relative to pure PSLBs; this difference is attributed to DPhPC filling the nm-scale pores in the polymerized domains that are created during bis-SorbPC polymerization. Thus, incomplete phase segregation increases the stability of poly(bis-SorbPC) but has the opposite, detrimental effect for DPhPC. Overall, these results provide guidance for the design of partially polymerized bilayers for technological uses.

Shear-Mediated Platelet Activation is Accompanied by Unique Alterations in Platelet Release of Lipids.

INTRODUCTION: Platelet activation by mechanical means such as shear stress exposure, is a vital driver of thrombotic risk in implantable blood-contacting devices used in the treatment of heart failure. Lipids are essential in platelets activation and have been studied following biochemical activation. However, little is known regarding lipid alterations occurring with mechanical shear-mediated platelet activation. METHODS: Here, we determined if shear-activation of platelets induced lipidome changes that differ from those associated with biochemically-mediated platelet activation. We performed high-resolution lipidomic analysis on purified platelets from four healthy human donors. For each donor, we compared the lipidome of platelets that were non-activated or activated by shear, ADP, or thrombin treatment. RESULTS: We found that shear activation altered cell-associated lipids and led to the release of lipids into the extracellular environment. Shear-activated platelets released 21 phospholipids and sphingomyelins at levels statistically higher than platelets activated by biochemical stimulation. CONCLUSIONS: We conclude that shear-mediated activation of platelets alters the basal platelet lipidome. Further, these alterations differ and are unique in comparison to the lipidome of biochemically activated platelets. Many of the released phospholipids contained an arachidonic acid tail or were phosphatidylserine lipids, which have known procoagulant properties. Our findings suggest that lipids released by shear-activated platelets may contribute to altered thrombosis in patients with implanted cardiovascular therapeutic devices. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12195-021-00692-x.

Expression of truncated Kir6.2 promotes insertion of functionally inverted ATP-sensitive K+ channels.

ATP-sensitive K+ (KATP) channels couple cellular metabolism to electrical activity in many cell types. Wild-type KATP channels are comprised of four pore forming (Kir6.x) and four regulatory (sulfonylurea receptor, SURx) subunits that each contain RKR endoplasmic reticulum retention sequences that serve to properly translocate the channel to the plasma membrane. Truncated Kir6.x variants lacking RKR sequences facilitate plasma membrane expression of functional Kir6.x in the absence of SURx; however, the effects of channel truncation on plasma membrane orientation have not been explored. To investigate the role of truncation on plasma membrane orientation of ATP sensitive K+ channels, three truncated variants of Kir6.2 were used (Kir6.2ΔC26, 6xHis-Kir6.2ΔC26, and 6xHis-EGFP-Kir6.2ΔC26). Oocyte expression of Kir6.2ΔC26 shows the presence of a population of inverted inserted channels in the plasma membrane, which is not present when co-expressed with SUR1. Immunocytochemical staining of intact and permeabilized HEK293 cells revealed that the N-terminus of 6xHis-Kir6.2ΔC26 was accessible on both sides of the plasma membrane at roughly equivalent ratios, whereas the N-terminus of 6xHis-EGFP-Kir6.2Δ26 was only accessible on the intracellular face. In HEK293 cells, whole-cell electrophysiological recordings showed a ca. 50% reduction in K+ current upon addition of ATP to the extracellular solution for 6xHis-Kir6.2ΔC26, though sensitivity to extracellular ATP was not observed in 6xHis-EGFP-Kir6.2ΔC26. Importantly, the population of channels that is inverted exhibited similar function to properly inserted channels within the plasma membrane. Taken together, these data suggest that in the absence of SURx, inverted channels can be formed from truncated Kir6.x subunits that are functionally active which may provide a new model for testing pharmacological modulators of Kir6.x, but also indicates the need for added caution when using truncated Kir6.2 mutants.

Design of Affinity Chromatography Peptide Ligands Through Combinatorial Peptide Library Screening.

In this chapter, a protocol to design affinity chromatography matrices with short peptide ligands immobilized for protein purification is described. The first step consists of the synthesis of a combinatorial peptide library on the hydroxymethylbenzoyl (HMBA)-ChemMatrix resin by the divide-couple-recombine (DCR) method using the Fmoc chemistry. Next, the library is screened with the protein of interest labeled with a fluorescent dye or biotin. Subsequently, peptides contained on positive beads are identified by tandem matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS/MS), and those sequences showing greater consensus are synthesized in larger quantities and immobilized on chromatographic supports. Finally, target protein adsorption on peptide affinity matrices is evaluated through equilibrium adsorption isotherms and breakthrough curves.

Examining the influence of bilayer structure on energy transfer and molecular photon upconversion in metal ion linked multilayers.

Metal ion linked multilayers is a unique motif to spatially control and geometrically restrict molecules on a metal oxide surface and is of interest in a number of promising applications. Here we use a bilayer composed of a metal oxide surface, an anthracene annihilator molecule, Zn(II) linking ion, and porphyrin sensitizers to probe the influence of the position of the metal ion binding site on energy transfer, photon upconversion, and photocurrent generation. Despite being energetically similar, varying the position of the carboxy metal ion binding group (i.e. ortho, meta, para) of the Pt(II) tetraphenyl porphyrin sensitizer had a large impact on energy transfer rates and upconverted photocurrent that can be attributed to differences in their geometries. From polarized attenuated total reflectance measurements of the bilayers on ITO, we found that the orientation of the first layer (anthracene) was largely unperturbed by subsequent layers. However, the tilt angle of the porphyrin plane varies dramatically from 41° to 64° to 57° for the para-, meta-, and ortho-COOH substituted porphyrin molecules, which is likely responsible for the variation in energy transfer rates. We go on to show using molecular dynamics simulations that there is considerable flexibility in porphyrin orientation, indicating that an average structure is insufficient to predict the ensemble behavior. Instead, even a small subset of the population with highly favorable energy transfer rates can be the primary driver in increasing the likelihood of energy transfer. Gaining control of the orientation and its distribution will be a critical step in maximizing the potential of the metal ion linked structures.

Potential-Modulated Total Internal Reflection Fluorescence for Measurement of the Electron Transfer Kinetics of Submonolayers on Optically Transparent Electrodes.

An electroreflectance method to determine the electron transfer rate constant of a film of redox-active chromophores immobilized on an optically transparent electrode when the surface coverage of the film is very low (<0.1 monolayer) is described herein. The method, potential-modulated total internal reflection fluorescence (PM-TIRF) spectroscopy, is a fluorescence version of potential-modulated attenuated total reflection (PM-ATR) spectroscopy that is applicable when the immobilized chromophores are luminescent. The method was tested using perylene diimide (PDI) molecules functionalized with p-phenylene phosphonic acid (PA) moieties that bind strongly to indium-tin oxide (ITO). Conditions to prepare PDI-phenyl-PA films that exhibit absorbance and fluorescence spectra characteristic of monomeric (i.e., nonaggregated) molecules were identified; the electrochemical surface coverage was approximately 0.03 monolayer. The tilt angle of the long axis of the PDI molecular plane is 58° relative to the ITO surface normal, 25° greater than the tilt angle of aggregated PDI-phenyl-PA films, which have a surface coverage of approximately one monolayer. The more in-plane orientation of monomeric films is likely due to the absence of cofacial π-π interactions present in aggregated films and possibly a difference in PA-ITO binding modes. The electron transfer rate constant (ks,opt) of monomeric PDI-phenyl-PA films was determined using PM-TIRF and compared with PM-ATR results obtained for aggregated films. For PDI monomers, ks,opt = 3.8 × 103 s-1, which is about 3.7-fold less than ks,opt for aggregated films. The slower kinetics are attributed to the absence of electron self-exchange between monomeric PDI molecules. Differences in the electroactivity of the binding sites on the ITO electrode surface also may play a role. This is the first demonstration of PM-TIRF for determining electron transfer rate constants at an electrode/organic film interface.

Incomplete penetrance in familial Alzheimer's disease with PSEN1 Ala260Gly mutation.

Presenilin1 (PSEN1) gene is the most common known genetic cause of early-onset familial Alzheimer's disease. We describe an Italian family with the known p.Ala260Gly mutation in PSEN1 gene. The presence of an asymptomatic 64-year-old male carrying the mutation provides evidence of a possible incomplete penetrance leading to a wider range of age at onset. In order to evaluate whether or not epigenetic modifications could contribute to the phenotypic heterogeneity, we assessed global DNA methylation levels which resulted significantly higher in the three females than in their presymptomatic brother. The study suggests that DNA methylation can contribute to slowing down or possibly protecting from the manifestation of symptoms even in monogenic diseases, emphasizing the great complexity of familial Alzheimer's disease.

Incorporating posttransplant cyclophosphamide-based prophylaxis as standard-of-care outside the haploidentical setting: challenges and review of the literature.

Posttransplant high-dose cyclophosphamide (PTCy) effectively prevents GvHD after haploidentical SCT. However, its use in HLA-matched SCT has been less explored. Fifty-six consecutive patients who underwent allo-SCT for hematological malignancies have been included in this prospective single-center protocol. Donors have been HLA-identical siblings, fully-matched unrelated or 1-allele-mismatched unrelated donors in 30%, 32%, and 37% of cases, respectively. Nine patients have received a TBI-containing MAC regimen, while the remaining (84%) received RIC platforms based on Fludarabine plus Busulfan/Melphalan. Due to the high graft failure (GF) rate (21%) in a preliminary analysis in the allo-RIC cohort (n = 29), protocol amendments have been implemented, with no further cases of GF after the introduction of mini-thiotepa (0/18). The overall incidence of grade II-IV acute GvHD is 24% (95% CI: 17-31%) with four steroid-refractory cases. Severe chronic GvHD has occurred in only 1 of 43 evaluable cases. The 1-year NRM and relapse are 18% (95% CI: 12-26%) and 30% (18-42%) and the OS and DFS are 78% and 64%, respectively. These outcomes support the feasibility of using PTCy as a SOC outside the haplo-setting, albeit mini-thiotepa (3 mg/kg) was incorporated in the standard allo-RIC platforms to prevent GF. Despite the limitations of a single-center experience and the short follow-up, these protocols show promising results with particular benefit in reducing the occurrence of moderate-to-severe GvHD.

Nanodomain Formation in Planar Supported Lipid Bilayers Composed of Fluid and Polymerized Dienoyl Lipids.

Polymerization of synthetic phospholipid monomers has been widely used to enhance the stability of lipid membranes in applications such as membrane-based biosensing, where the inherent instability of fluid-phase lipid bilayers can be problematic. However, lipid polymerization typically decreases membrane fluidity, which may be required to maintain the activity of reconstituted integral proteins and peptides. Prior work has shown that a bilayer composed of binary mixtures of poly(lipid) and fluid lipid exhibits enhanced stability and supports the function of incorporated biomolecules. This work examines the structural basis of these findings using planar supported lipid bilayers (PSLBs) composed of binary mixtures of a polymerizable lipid, 1,2-bis[10-(2',4'-hexadienoloxy)decanoyl]-sn-glycero-3-phosphocholine (bis-SorbPC), and a nonpolymerizable lipid, 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC). Fluorescence recovery after photobleaching (FRAP) measurements showed that long-range lateral diffusion was minimally affected when the poly(lipid) mole ratio was ≤0.7. Atomic force microscopy, used to examine phase segregation in these PSLBs, showed that DPhPC forms a continuous lipid matrix that is 0.2-0.4 nm thicker than the island-like poly(bis-SorbPC) domains, with lateral dimensions of ≤200 nm. The nanoscale phase segregation allows for long-range lateral diffusion of lipid probes in the DPhPC matrix. The combination of fluidity and stability in these materials should make them useful in membrane-based biosensing applications.

Aspectos morfocuantitativos de las vellosidades coriales libres en gestas normales, con diabetes, hipertensión arterial y restricción del crecimiento intrauterino / Morphoquantitative characteristics of free corial vellosities in normal births, with diabetes, hypertension and restriction of intrauterine growth

Las patologías de la gestación como la hipertensión, diabetes mellitus gestacional, o restricción del crecimiento intrauterino, pueden determinar modificaciones en las características morfológicas macro y microscópicas de la placenta y sus vellosidades coriales libres, y en el feto se puede acompañar de manifestaciones patológicas, con riesgo para su calidad de vida futura, e incluso su viabilidad. El objetivo de este trabajo consistió en describir aspectos morfométricos e histológicos de las vellosidades coriales libres en gestas normales, con diabetes e hipertensión arterial. Se utilizaron 30 placentas humanas y fueron separadas, según presencia o ausencia de patologías en el embarazo, en tres grupos: Normal (N), Síndrome Hipertensivo del Embarazo (SHE), Diabetes (D) y Restricción del Crecimiento Intrauterino (RCIU). Se usó ficha para registrar peso placentario y del recién nacido Todas las muestras fueron fijadas en formalina tamponada al 10 %. De cada una fueron extraídas 5 muestras, obteniendo 25 cortes por cada placenta. Posteriormente, fueron teñidas con H&E, Azul Alcián y Tricrómico de Masson. Además, se efectuó el análisis histológico y morfométrico (ImageJ®) de las vellosidades coriales. El análisis estadístico fue realizado utilizando ANOVA. Entre los cambios morfológicos, se encontró una relación peso placentario/peso del recién nacido aumentada en la Diabetes Mellitus Gestacional asociada a cambios histológicos. No hubo cambios morfométricos significativos entre placentas N, SHE y D. Hubo un aumento en el número de vasos coriales en placentas del grupo D (P < 0,05) y de la superficie entre las vellosidades coriales. En el grupo SHE hubo aumento moderado de nudos sinciciales y presencia de fibrina en el estroma. Las placentas con Diabetes Mellitus Gestacional experimentan alteraciones histológicas, como consecuencia de cambios estructurales y funcionales. Además, el aumento de vasos sanguíneos en placentas con diabetes se produce por neoformación vascular y mayor penetración de vasos sanguíneos dentro de las vellosidades. En el caso del SHE las alteraciones placentarias se relacionan con la gravedad de la enfermedad.

Gestational pathologies such as hypertension, gestational diabetes mellitus and restriction of intrauterine growth can determine changes in the macro and microscopic morphological characteristics of the placenta and its free chorionic villi. In the fetus it can be accompanied by pathological manifestations with risk to its viability and future quality of life. The aim of this work was to describe morphometric and histological aspects of free chorionic villi in normal pregnancies associated with diabetes, hypertension and restriction of intrauterine growth. Thirty human placentas were used and were separated into three groups: Normal (N), Hypertensive Pregnancy Syndrome (SHE), Diabetes (D), and Restriction of Intrauterine Growth (RIG) according to evident pathologies or absence thereof during pregnancy. Tab was used to record placental and newborn weight. All samples were fixed in 10 % buffered formalin. From each, 5 samples were extracted, obtaining 25 cuts for each placenta. Subsequently, they were stained with H & E, Alcian Blue and Masson's Trichrome. In addition, histological and morphometric analysis (ImageJ®) of the chorion villus was carried out. Statistical analysis was performed using ANOVA. Among the morphological changes, an increased placental weight / weight ratio of the newborn was found in Gestational Diabetes Mellitus associated with histological changes. There were no significant morphometric changes between placentas N, SHE and D. There was an increase in the number of corial vessels in placentas of group D (P <0.05) and of the surface between the chorion villi. In the SHE group there was a moderate increase in syncytial nodes and presence of fibrin in the stroma. Placentas with Gestational Diabetes Mellitus experience histological alterations, as a consequence of structural and functional changes. In addition, the increase of blood vessels in placentas D is produced by vascular neoformation and increased penetration of blood vessels into the villi. In the case of SHE, placental alterations are related to the severity of the disease.

Expression, purification, and electrophysiological characterization of a recombinant, fluorescent Kir6.2 in mammalian cells.

The inwardly rectifying K+ (Kir) channel, Kir6.2, plays critical roles in physiological processes in the brain, heart, and pancreas. Although Kir6.2 has been extensively studied in numerous expression systems, a comprehensive description of an expression and purification protocol has not been reported. We expressed and characterized a recombinant Kir6.2, with an N-terminal decahistidine tag, enhanced green fluorescent protein (eGFP) and deletion of C-terminal 26 amino acids, in succession, denoted eGFP-Kir6.2Δ26. eGFP-Kir6.2Δ26 was expressed in HEK293 cells and a purification protocol developed. Electrophysiological characterization showed that eGFP-Kir6.2Δ26 retains native single channel conductance (64 ±â€¯3.3 pS), mean open times (τ1 = 0.72 ms, τ2 = 15.3 ms) and ATP affinity (IC50 = 115 ±â€¯25 µM) when expressed in HEK293 cells. Detergent screening using size exclusion chromatography (SEC) identified Fos-choline-14 (FC-14) as the most suitable surfactant for protein solubilization, as evidenced by maintenance of the native tetrameric structure in SDS-PAGE and western blot analysis. A two-step scheme using Co2+-metal affinity chromatography and SEC was implemented for purification. Purified protein activity was assessed by reconstituting eGFP-Kir6.2Δ26 in black lipid membranes (BLMs) composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (POPG), l-α-phosphatidylinositol-4,5-bisphosphate (PIP2) in a 89.5:10:0.5 mol ratio. Reconstituted eGFP-Kir6.2Δ26 displayed similar single channel conductance (61.8 ±â€¯0.54 pS) compared to eGFP-Kir6.2Δ26 expressed in HEK293 membranes; however, channel mean open times increased (τ1 = 7.9 ms, τ2 = 61.9 ms) and ATP inhibition was significantly reduced for eGFP-Kir6.2Δ26 reconstituted into BLMs (IC50 = 3.14 ±â€¯0.4 mM). Overall, this protocol should be foundational for the production of purified Kir6.2 for future structural and biochemical studies.

[Appendicitis versus nonspecific acute abdominal pain: diagnostic accuracy of ultrasound]. / Apendicitis versus dolor abdominal agudo inespecífico: rendimiento diagnóstico de la ecografía.

PURPOUSE: The aim of this study is to assess the diagnostic accuracy of ultrasound to differentiate appendicitis from nonspecific acute abdominal pain, that is the most common process requiring differential diagnosis in clinical practice. MATERIAL AND METHODS: Patients admitted for suspicion of appendicitis were prospectively evaluated in our hospital during two years (2013-2014). Cases of nonspecific acute abdominal pain and appendicitis assessed by ultrasound were enrolled in the study. The different variables collected were statistically analyzed by descriptive, univariate and diagnostic accuracy studies. RESULTS: A total of 275 patients were studied, 143 cases of nonspecific acute abdominal pain and 132 cases of appendicitis. Ultrasound sensitivity and specificity to differentiate appendicitis were 94.7% and 87.4% respectively, with a 12.6% rate of false positives and a 5.3% rate of false negatives. The rate of false negatives in perforated group was 17.4% and analysis according to Pediatric Appendicitis Score risk groups showed a 12.2% rate of false positives in low-risk group and a 6.3% rate of false negatives in high-risk group. CONCLUSIONS: The use of ultrasound in low clinical probability cases of appendicitis could rise unnecessary surgery rate, due to the significant number of false positives in this group of patients. In high probability clinical cases, ultrasound does not contribute too much to diagnosis and it could be a confusion factor by the significant number of false negative associated to perforated appendicitis.

OBJETIVO: El objetivo del estudio es evaluar el rendimiento diagnóstico de la ecografía para diferenciar la apendicitis del dolor abdominal agudo inespecífico, principal proceso con el que requiere diagnóstico diferencial en la práctica clínica. MATERIAL Y METODOS: Se evaluaron los pacientes atendidos por sospecha de apendicitis en nuestro centro durante 2 años (2013-2014), incorporando al estudio los casos de dolor abdominal agudo inespecífico y apendicitis en los que se realizó ecografía. Las diferentes variables recogidas se analizaron estadísticamente de manera descriptiva, univariante y con estudios de rendimiento diagnóstico. RESULTADOS: Se estudiaron 275 casos; 143 casos de dolor abdominal agudo inespecífico y 132 casos de apendicitis. La sensibilidad y especificidad de la ecografía para diferenciar apendicitis fue del 94,7% y 87,4%, respectivamente, con un porcentaje de falsos positivos del 12,6% y de falsos negativos del 5,3%. El porcentaje de falsos negativos en el grupo de apendicitis perforada alcanzó el 17,4% y el análisis según los grupos de riesgo establecidos por el Pediatric Appendicitis Score mostró un porcentaje de falsos positivos del 12,2% en el grupo de bajo riesgo y de falsos negativos del 6,3% en el grupo de alto riesgo. CONCLUSIONES: El uso de la ecografía en casos de baja probabilidad clínica de apendicitis podría incrementar la tasa de cirugía innecesaria, debido al significativo número de falsos positivos en este grupo de pacientes. En casos de alta probabilidad clínica de apendicitis, la ecografía aporta poco al diagnóstico, e incluso podría ser un factor de confusión por el significativo número de falsos negativos asociados a la apendicitis perforada.

Axially Bound Ruthenium Phthalocyanine Monolayers on Indium Tin Oxide: Structure, Energetics, and Charge Transfer Properties.

The efficiency of charge collection at the organic/transparent conducting oxide (TCO) interface in organic photovoltaic (OPV) devices affects overall device efficiency. Modifying the TCO with an electrochemically active molecule may enhance OPV efficiency by providing a charge-transfer pathway between the electrode and the organic active layer, and may also mitigate surface recombination. The synthesis and characterization of phosphonic acid-ruthenium phthalocyanine (RuPcPA) monolayer films on indium tin oxide (ITO), designed to facilitate charge harvesting at ITO electrodes, is presented in this work. The PA group was installed axially relative to the Pc plane so that upon deposition, RuPcPA molecules were preferentially aligned with the ITO surface plane. The tilt angle of 22° between the normal axes to the Pc plane and the ITO surface plane, measured by attenuated total reflectance (ATR) spectroscopy, is consistent with a predominately in-plane orientation. The effect of surface roughness on RuPcPA orientation was modeled, and a correlation was obtained between experimental and theoretical mean tilt angles. Based on electrochemical and spectroelectrochemical studies, RuPcPA monolayers are composed predominately of monomers. Electrochemical impedance spectroscopy (EIS) and potential modulated-ATR (PM-ATR) spectroscopy were used to characterize the electron-transfer (ET) kinetics of these monolayers. A rate constant of 4.0 × 103 s-1 was measured using EIS, consistent with a short tunneling distance between the chromophore and the electrode surface. Using PM-ATR, ks,opt values of 2.2 × 103 and 2.4 × 103 s-1 were measured using TE and TM polarized light, respectively; the similarity of these values is consistent with a narrow molecular orientation distribution and narrow range of tunneling distances. The ionization potential of RuPcPA-modified ITO was measured using ultraviolet photoelectron spectroscopy and the results indicate favorable energetics for hole collection at the RuPcPA/ITO interface, indicating that this type of TCO modification may be useful for enhancing charge collection efficiency in OPV devices.

Apendicitis versus dolor abdominal agudo inespecífico: rendimiento diagnóstico de la ecografía / Appendicitis versus nonspecific acute abdominal pain: diagnostic accuracy of ultrasound

Objetivo. El objetivo del estudio es evaluar el rendimiento diagnóstico de la ecografía para diferenciar la apendicitis del dolor abdominal agudo inespecífico, principal proceso con el que requiere diagnóstico diferencial en la práctica clínica. Material y métodos. Se evaluaron los pacientes atendidos por sospecha de apendicitis en nuestro centro durante 2 años (2013-2014), incorporando al estudio los casos de dolor abdominal agudo inespecífico y apendicitis en los que se realizó ecografía. Las diferentes variables recogidas se analizaron estadísticamente de manera descriptiva, univariante y con estudios de rendimiento diagnóstico. Resultados. Se estudiaron 275 casos; 143 casos de dolor abdominal agudo inespecífico y 132 casos de apendicitis. La sensibilidad y especificidad de la ecografía para diferenciar apendicitis fue del 94,7% y 87,4%, respectivamente, con un porcentaje de falsos positivos del 12,6% y de falsos negativos del 5,3%. El porcentaje de falsos negativos en el grupo de apendicitis perforada alcanzó el 17,4% y el análisis según los grupos de riesgo establecidos por el Pediatric Appendicitis Score mostró un porcentaje de falsos positivos del 12,2% en el grupo de bajo riesgo y de falsos negativos del 6,3% en el grupo de alto riesgo. Conclusiones. El uso de la ecografía en casos de baja probabilidad clínica de apendicitis podría incrementar la tasa de cirugía innecesaria, debido al significativo número de falsos positivos en este grupo de pacientes. En casos de alta probabilidad clínica de apendicitis, la ecografía aporta poco al diagnóstico, e incluso podría ser un factor de confusión por el significativo número de falsos negativos asociados a la apendicitis perforada (AU)

Purpose. The aim of this study is to assess the diagnostic accuracy of ultrasound to differentiate appendicitis from nonspecific acute abdominal pain, that is the most common process requiring differential diagnosis in clinical practice. Material and methods. Patients admitted for suspicion of appendicitis were prospectively evaluated in our hospital during two years (2013-2014). Cases of nonspecific acute abdominal pain and appendicitis assessed by ultrasound were enrolled in the study. The different variables collected were statistically analyzed by descriptive, univariate and diagnostic accuracy studies. Results. A total of 275 patients were studied, 143 cases of nonspecific acute abdominal pain and 132 cases of appendicitis. Ultrasound sensitivity and specificity to differentiate appendicitis were 94.7% and 87.4% respectively, with a 12.6% rate of false positives and a 5.3% rate of false negatives. The rate of false negatives in perforated group was 17.4% and analysis according to Pediatric Appendicitis Score risk groups showed a 12.2% rate of false positives in low-risk group and a 6.3% rate of false negatives in high-risk group. Conclusions. The use of ultrasound in low clinical probability cases of appendicitis could rise unnecessary surgery rate, due to the significant number of false positives in this group of patients. In high probability clinical cases, ultrasound does not contribute too much to diagnosis and it could be a confusion factor by the significant number of false negative associated to perforated appendicitis (AU)

Characterization of Charge-Transfer Kinetics at Organic/Electrode Interfaces Using Potential-modulated Attenuated Total Reflectance (PM-ATR) Spectroscopy.

Potential-modulated attenuated total reflectance (PM-ATR) spectroscopy is a spectroelectrochemical method that utilizes the potential modulation approach and a waveguide ATR geometry. This unique combination enables measurements of electron-transfer (ET) kinetics of monolayer to submonolayer thin films on waveguide electrode surfaces. Selective probing of molecular subpopulations in a film can be achieved by choosing appropriate combinations of applied potential, wavelength, and polarization of light, which allows subpopulation structure to be correlated with ET kinetics. In this review, the basic theory of PM-ATR is introduced, and examples illustrating characterization of the structure and ET kinetics of organic semiconductor monolayers on electrode surfaces are presented, demonstrating the capabilities and applications of the PM-ATR technique.

Determining Band-Edge Energies and Morphology-Dependent Stability of Formamidinium Lead Perovskite Films Using Spectroelectrochemistry and Photoelectron Spectroscopy.

We show for the first time that the frontier orbital energetics (conduction band minimum (CBM) and valence band maximum (VBM)) of device-relevant, methylammonium bromide (MABr)-doped, formamidinium lead trihalide perovskite (FA-PVSK) thin films can be characterized using UV-vis spectroelectrochemistry, which provides an additional and straightforward experimental technique for determining energy band values relative to more traditional methods based on photoelectron spectroscopy. FA-PVSK films are processed via a two-step deposition process, known to provide high efficiency solar cells, on semitransparent indium tin oxide (ITO) and titanium dioxide (TiO2) electrodes. Spectroelectrochemical characterization is carried out in a nonsolvent electrolyte, and the onset potential for bleaching of the FA-PVSK absorbance is used to estimate the CBM, which provides values of ca. -4.0 eV versus vacuum on both ITO and TiO2 electrodes. Since electron injection occurs from the electrode to the perovskite, the CBM is uniquely probed at the buried metal oxide/FA-PVSK interface, which is otherwise difficult to characterize for thick films. UPS characterization of the same FA-PVSK thin films provide complementary near-surface measurements of the VBM and electrode-dependent energetics. In addition to energetics, controlled electrochemical charge injection experiments in the nonsolvent electrolyte reveal decomposition pathways that are related to morphology-dependent heterogeneity in the electrochemical and chemical stability of these films. X-ray photoelectron spectroscopy of these electrochemically treated FA-PVSK films shows changes in the average near-surface stoichiometry, which suggests that lead-rich crystal termination planes are the most likely sites for electron trapping and thus nanometer-scale perovskite decomposition.

Shear-mediated platelet activation in the free flow: Perspectives on the emerging spectrum of cell mechanobiological mechanisms mediating cardiovascular implant thrombosis.

Shear-mediated platelet activation (SMPA) is central in thrombosis of implantable cardiovascular therapeutic devices. Despite the morbidity and mortality associated with thrombosis of these devices, our understanding of mechanisms operative in SMPA, particularly in free flowing blood, remains limited. Herein we present and discuss a range of emerging mechanisms for consideration for "free flow" activation under supraphysiologic shear. Further definition and manipulation of these mechanisms will afford opportunities for novel pharmacologic and mechanical strategies to limit SMPA and enhance overall implant device safety.