Titanium Dioxide Mesoporous Electrodes for Solid‐State Dye‐Sensitized Solar Cells: Cross‐Analysis of the Critical Parameters

We report a comparative study on the use of four different mesoporous titanium dioxide (TiO₂) photo‐electrodes for the fabrication of solid‐state dye‐sensitized solar cells (sDSSCs). The photovoltaic parameters of the device correlate with several intrinsic properties of the film, based not only on its morphological features, as commonly considered in standard characterizations, but also on the transport and the electronic properties of the photo‐electrode. These properties differ significantly for TiO₂ electrodes processed using different colloidal pastes, and are decisive for the photovoltaic efficiency, ranging from 3.7% up to 5.1%. In particular, the dielectric permittivity of each mesoporous layer (ε_eff) and the number of traps (N_t) determined by the space‐charge‐limited current (SCLC) theory are found to be a bottle‐neck for the charge transport, greatly influencing the fill factor (FF) and open circuit voltage (V_oc) of the cells. In addition, a direct correlation between TiO₂ surface potential with the V_oc was established. Cross‐analysis of key macroscopic parameters of the films prior to integration in the devices, in particular focusing on the determination of the capacitance and surface potential shift of the TiO₂ mesoporous anode, represents a straightforward yet powerful method to screen and select the most suitable TiO₂ for applications in sDSSCs.     

Susceptibility to Helicobacter pylori infection: results of an epidemiological investigation among gastric cancer patients

The aim of this study was to identify the clinical, demographic, lifestyle factors and selected genetic polymorphisms that affect the susceptibility towards Helicobacter pylori (H. pylori) infection in gastric cancer patients. Histological confirmed gastric adenocarcinoma cases that underwent curative gastrectomy between 2002 and 2012 were included. Gastric biopsy samples were obtained to determine the H. pylori status, and further cagA status and vacA m and s genotypes by polymerase chain reaction. Patients were interviewed with structured questionnaires, and blood samples were collected for EPHX1, GSTM1, GSTT1, IL1B, IL1-RN, MTHFR and p53 genotyping. Proportions were compared in univariate analysis, while the relation between putative risk factors and H. pylori status and genotype were measured using logistic regression analysis. One hundred forty-nine gastric cancer patients were included, of which 78.5 % were H. pylori positive. Among positive patients 50 % were cagA+, 72.5 % vacA m1 and 80.7 % vacA s1. The presence of cagA was less frequent among vacA m1 (p = 0.031) and vacA s1 (p = 0.052) subtypes. The presence of father history for any cancer was a significant risk factor for H. pylori infection [adjusted odds ratio (OR) = 8.18, 95 % confidence interval (CI) 1.04–64.55]. EPHX1 exon 3 T > C (OR = 0.35, CI 95 % 0.13–0.94), IL1B-511 T > C (OR = 0.38, CI 95 % 0.15–0.97) and IL1-RN VNTR (OR = 0.19, CI 95 % 0.06–0.58) polymorphisms were protective towards H. pylori infection in the univariate analysis. Wine consumption was associated with higher risk of carrying the H. pylori vacA m1 virulent subtype (p = 0.034). Lastly, cardiovascular diseases were less common among cagA positive subjects (p = 0.023). Father history of any cancer is a risk factor for H. pylori infection. Polymorphisms in IL1B-511, IL1-RN and EPHX1 exon 3 genes might be protective towards H. pylori infection.     

Biocompatible Anionic Polymeric Microspheres as Priming Delivery System for Effetive HIV/AIDS Tat-Based Vaccines

Here we describe a prime-boost regimen of vaccination in Macaca fascicularis that combines priming with novel anionic microspheres designed to deliver the biologically active HIV-1 Tat protein and boosting with Tat in Alum. This regimen of immunization modulated the IgG subclass profile and elicited a balanced Th1-Th2 type of humoral and cellular responses. Remarkably, following intravenous challenge with SHIV89.6P_cy243, vaccinees significantly blunted acute viremia, as compared to control monkeys, and this control was associated with significantly lower CD4⁺ T cell depletion rate during the acute phase of infection and higher ability to resume the CD4⁺ T cell counts in the post-acute and chronic phases of infection. The long lasting control of viremia was associated with the persistence of high titers anti-Tat antibodies whose profile clearly distinguished vaccinees in controllers and viremics. Controllers, as opposed to vaccinated and viremic cynos, exhibited significantly higher pre-challenge antibody responses to peptides spanning the glutamine-rich and the RGD-integrin-binding regions of Tat. Finally, among vaccinees, titers of anti-Tat IgG1, IgG3 and IgG4 subclasses had a significant association with control of viremia in the acute and post-acute phases of infection. Altogether these findings indicate that the Tat/H1D/Alum regimen of immunization holds promise for next generation vaccines with Tat protein or other proteins for which maintenance of the native conformation and activity are critical for optimal immunogenicity. Our results also provide novel information on the role of anti-Tat responses in the prevention of HIV pathogenesis and for the design of new vaccine candidates.     

A Novel Technique of Contrast-Enhanced Optical Coherence Tomography Imaging in Evaluation of Clearance of Lipids in Human Tears

Purpose

The aim of this work was to gather preliminary data in different conditions of healthy eyes, aqueous tear deficient dry eyes, obstructive meibomian gland disease (MGD) and non-obvious obstructive MGD (NOMGD) individuals, using a new, contrast-enhanced optical coherence tomography (OCT) imaging method to evaluate the clearance of lipids in human tears.

Methods

Eighty-two adult patients presenting with complaints of ocular irritation were studied for abnormalities of the ocular surface and classified as healthy (n = 21), aqueous tear deficient dry eyes (n = 20), obstructive MGD (n = 15) and NOMGD (n = 26) individuals. A lipid-based tracer, containing an oil-in-water emulsion, was used to obtain an enhanced OCT imaging of the lower tear meniscus. After instillation, a dramatic initial increase of reflectivity of the lower tear meniscus was detected by OCT, followed by a decay back to baseline values over time. Based on this finding, the clearance of lipids was measured in real-time by Fourier-domain anterior segment OCT.

Results

The differences in the clearance of lipids among the four groups as well as the correlations between symptom questionnaire score, standardized visual scale test, fluorescein break-up time, ocular surface fluorescein staining score, Schirmer I test scores were found to be statistically significant. The individual areas under the curve of the clearance of lipids calculated by the receiver operating characteristic curve technique ranged from 0.66 to 0.98, suggesting reliable sensitivity and specificity of lipid-enhanced OCT imaging.

Conclusions

This new technique of contrast-enhanced OCT imaging of the tear film following lipid-based tracer instillation provides a measure of the clearance of lipids. The quantitative values found are in agreement with other methods of evaluation of the lacrimal system. An improvement of the clinician''s ability in the diagnosis and understanding of abnormalities of the ocular surface may be achieved by this simple approach.     

Factors Influencing the Measurement of Lysosomal Enzymes Activity in Human Cerebrospinal Fluid

Measurements of the activities of lysosomal enzymes in cerebrospinal fluid have recently been proposed as putative biomarkers for Parkinson''s disease and other synucleinopathies. To define the operating procedures useful for ensuring the reliability of these measurements, we analyzed several pre-analytical factors that may influence the activity of β-glucocerebrosidase, α-mannosidase, β-mannosidase, β-galactosidase, α-fucosidase, β-hexosaminidase, cathepsin D and cathepsin E in cerebrospinal fluid. Lysosomal enzyme activities were measured by well-established fluorimetric assays in a consecutive series of patients (n = 28) with different neurological conditions, including Parkinson''s disease. The precision, pre-storage and storage conditions, and freeze/thaw cycles were evaluated. All of the assays showed within- and between-run variabilities below 10%. At −20°C, only cathepsin D was stable up to 40 weeks. At −80°C, the cathepsin D, cathepsin E, and β-mannosidase activities did not change significantly up to 40 weeks, while β-glucocerebrosidase activity was stable up to 32 weeks. The β-galactosidase and α-fucosidase activities significantly increased (+54.9±38.08% after 4 weeks and +88.94±36.19% after 16 weeks, respectively). Up to four freeze/thaw cycles did not significantly affect the activities of cathepsins D and E. The β-glucocerebrosidase activity showed a slight decrease (−14.6%) after two freeze/thaw cycles. The measurement of lysosomal enzyme activities in cerebrospinal fluid is reliable and reproducible if pre-analytical factors are accurately taken into consideration. Therefore, the analytical recommendations that ensue from this study may contribute to the establishment of actual values for the activities of cerebrospinal fluid lysosomal enzymes as putative biomarkers for Parkinson''s disease and other neurodegenerative disorders.     

Stable Single α-Helices Are Constant Force Springs in Proteins

Single α-helix (SAH) domains are rich in charged residues (Arg, Lys, and Glu) and stable in solution over a wide range of pH and salt concentrations. They are found in many different proteins where they bridge two functional domains. To test the idea that their high stability might enable these proteins to resist unfolding along their length, the properties and unfolding behavior of the predicted SAH domain from myosin-10 were characterized. The expressed and purified SAH domain was highly helical, melted non-cooperatively, and was monomeric as shown by circular dichroism and mass spectrometry as expected for a SAH domain. Single molecule force spectroscopy experiments showed that the SAH domain unfolded at very low forces (<30 pN) without a characteristic unfolding peak. Molecular dynamics simulations showed that the SAH domain unfolds progressively as the length is increased and refolds progressively as the length is reduced. This enables the SAH domain to act as a constant force spring in the mechanically dynamic environment of the cell.     

Resurgent current and voltage sensor trapping enhanced activation by a beta-scorpion toxin solely in Nav1.6 channel. Significance in mice Purkinje neurons

Resurgent currents are functionally crucial in sustaining the high frequency firing of cerebellar Purkinje neurons expressing Na(v)1.6 channels. Beta-scorpion toxins, such as CssIV, induce a left shift in the voltage-dependent activation of Na(v)1.2 channels by "trapping" the IIS4 voltage sensor segment. We found that the dangerous Cn2 beta-scorpion peptide induces both the left shift voltage-dependent activation and a transient resurgent current only in human Na(v)1.6 channels (among 1.1-1.7), whereas CssIV did not induce the resurgent current. Cn2 also produced both actions in mouse Purkinje cells. These findings suggest that only distinct beta-toxins produce resurgent currents. We suggest that the novel and unique selectivity of Cn2 could make it a model drug to replace deep brain stimulation of the subthalamic nucleus in patients with Parkinson disease.     

A new and efficient entry to D-xylo-hexos-4-ulose and some derivatives thereof through epoxidation of the 3,4-hexeno derivative of diacetone-D-glucose

A new preparation of D-xylo-hexos-4-ulose (1) and of its 3-m-chlorobenzoate (2) has been devised using the epoxidation of 3-deoxy-1,2:5,6-di-O-isopropylidene-D-erythro-hex-3-enofuranose (6) as the key step. The epoxidation of 6 in CH2Cl2 furnished with high yield 1,2:5,6-di-O-isopropylidene-3-O-m-chlorobenzoyl-4-C-hydroxy-D-xylo-hexos-4-ulo-1,4-furanose as a mixture of C-4 hemiacetal anomers (7a,b), which, on acid hydrolysis, gave a tautomeric mixture of 3-O-m-chlorobenzoyl-D-xylo-hexos-4-ulose (2) with an overall 60% yield from 6. The formation of 4-C-methoxy-diacetone-D-glucose derivatives (11a,b) through epoxidation-methanolysis of 6, took place with reduced yield because of the competition between m-chlorobenzoic acid (MCBA) and methanol to the opening by attack at C-4 of the intermediate epoxide and the formation of acyclic products arising from the alternative nucleophilic attack at C-1. Acid hydrolysis of derivatives 11 gave D-xylo-hexos-4-ulose (1) with a 35% overall yield from 6. NMR analysis showed that 2 is composed, in CD3CN, mainly by a 7:3 mixture of 4-keto-alpha- and beta-pyranose forms, while 1, in D2O, is present as a more complex mixture constituted mainly by 4-keto-alpha- and beta-pyranoses and their respective hydrates in a 17:15:34:34 ratio.     

Molecular dynamics simulation of dextran extension by constant force in single molecule AFM

The extension of 1-6 polysaccharides has been studied in a series of recent single molecule AFM experiments. For dextran, a key finding was the existence of a plateau in the force-extension curve at forces between 700 and 1000 pN. We studied the extension of the dextran 10-mer under constant force using atomistic simulation with various force fields. All the force fields reproduce the experimental plateau on the force-extension curve. With AMBER94 and AMBER-GLYCAM04 force fields the plateau can be explained by a transition of the glucopyranose rings in the dextran monomers from the chair ((4)C(1)) to the inverted chair ((1)C(4)) conformation while other processes occur at smaller (rotation around C5-C6 bond) or higher (chairs to boat transitions) forces. The CHARMM force field provides a different picture which associates the occurrence of the plateau to chair-boat transitions of the glucopyranose rings.