bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organometallic–Polypeptide Block Copolymers: Synthesis and Self‐Assembly of Poly(ferrocenyldimethylsilane)‐b‐Poly(ε‐benzyloxycarbonyl‐L‐Lysine)
Authors: Wang Yishan , Zou Shan , Kim Kyoung Taek , Manners Ian , Winnik Mitchell A. 
Published: July 2008

AbstractA new type of metallopolymer‐polypeptide block copolymer poly(ferrocenyldimethylsilane)‐b‐poly (ε‐benzyloxycarbonyl‐l‐lysine) was synthesized by ring‐opening polymerization of ε‐benzyloxycarbonyl‐l‐lysine N‐carboxyanhydride initiated by using a primary amino‐terminated poly(ferrocenyldimethylsilane). Studies on the self‐organization behavior of this polypeptide block copolymer in both the bulk state and in solution were performed. In the bulk state, a cylindrical‐in‐lamellar structure was observed in a compositionally asymmetric sample. Rod‐like micelles with a polyferrocenylsilane core formed in a polypeptide‐selective solvent alone or in the presence of a common solvent. Significantly, an additional small quantity of the common solvent assisted the formation of longer micelles and micelles with better shape‐regularity. This is attributed to a decrease in the number of nucleation events and PFS core reorganization effects.
Polyviologen Dendrimers as Hosts and Charge‐Storing Devices
Authors: Ronconi Célia M. , Stoddart J. Fraser , Balzani Vincenzo , Baroncini Massimo , Ceroni Paola , Giansante Carlo , Venturi Margherita 
Published: July 2008

AbstractTwo dendrimers were designed and synthesized that contain a 1,3,5‐trisubstituted benzenoid core and incorporate 9 and 21 viologen (4,4′‐bipyridinium) units in their branches in addition to hydrophilic (aryloxy) terminal groups. For comparison purposes, model compounds containing one and two viologen units were also studied. These polycationic dendrimers form strong host–guest complexes with the dianionic form of the red dye eosin in dilute CH2Cl2 solutions. Titration experiments, based on fluorescence measurements, showed that each viologen unit in the dendritic structures becomes associated with an eosin dianion. Electrochemical (in MeCN) and photosensitization (in CH2Cl2) experiments revealed that only a fraction of the viologen units present in the dendritic structures can be reduced. This fraction corresponds to the number of viologen units present in the outer shells of the dendrimers. The reasons for incomplete charge pooling are discussed. Comparison with the behavior of polyviologen dendrimers that are terminated with bulky tetraarylmethane groups and were studied previously enabled the role played by the terminal groups in the redox and hosting properties to be elucidated.
Two‐Dimensionally Extended Porphyrin Tapes: Synthesis and Shape‐Dependent Two‐Photon Absorption Properties
Authors: Nakamura Yasuyuki , Jang So Young , Tanaka Takayuki , Aratani Naoki , Lim Jong Min , Kim Kil Suk , Kim Dongho , Osuka Atsuhiro 
Published: July 2008

AbstractWe report the synthesis and characterization of L‐ and T‐shaped porphyrin tapes as extensible structural motifs of two‐dimensionally extended porphyrin tapes. The two‐photon absorption (TPA) cross‐section values (σ(2)) for L‐ and T‐shaped porphyrin tapes as well as those for linear trimeric and tetrameric porphyrin tapes were measured by an open‐aperture Z‐scan method at 2300 nm, a wavelength at which the one‐photon absorption contribution is either zero or almost negligible. Under these conditions, the σ(2) values for the linear porphyrin tape trimer and tetramer were determined to be 18 500 and 41 200 GM, respectively. The σ(2) value for the L‐shaped trimer was determined to be 8700 GM, which is only half that of the linear trimer, whereas the σ(2) value for the T‐shaped tetramer was measured to be 35 700 GM. These results clearly indicate the dependence of the TPA cross‐section on the molecular shape, which underscores the importance of directionality in the π‐conjugation pathway for the enhancement of TPA cross‐ section.
A Flexible Method for the Conjugation of Aminooxy Ligands to Preformed Complexes of Nucleic Acids and Lipids
Authors: Hecker James G. , Berger Gideon O. , Scarfo Keith A. , Zou Shaomin , Nantz Michael H. 
Published: July 2008

AbstractAttachment of targeted ligands to nonviral DNA or RNA delivery systems is a promising strategy that seeks to overcome the poor target selectivity generally observed in systemic delivery applications. Several methods have been developed for the conjugation of ligands to lipids or polymers, however, direct conjugation of ligands onto lipid– or polymer–nucleic acid complexes is not as straightforward. Here, we examine an oximation approach to directly label a lipoplex formulation. Specifically, we report the synthesis of a cationic diketo lipid DMDK, and its use as a convenient ligation tool for attachment of aminooxy‐functionalized reagents after its complexation with DNA. We demonstrate the feasibility of direct lipoplex labeling by attaching an aminooxy‐functionalized fluorescent probe onto pre‐formed plasmid DNA–DMDK lipoplexes (luciferase, GFP). The results reveal that DMDK protects DNA from degradation on exposure to either DNase or human cerebral spinal fluid, and that simple mixing of DMDK lipoplexes with the aminooxy probe labels the complexes without sacrificing transfection efficiency. The biocompatibility and selectivity of this method, as well as the ease of bioconjugation, make this labeling approach ideal for biological applications.
Syntaxin 3b is a t‐SNARE specific for ribbon synapses of the retina
Authors: Curtis Leigh B. , Doneske Blair , Liu Xiaoqin , Thaller Christina , McNew James A. , Janz Roger 
Published: August 2008

AbstractPrevious studies have demonstrated that ribbon synapses in the retina do not contain the t‐SNARE (target‐soluble N‐ethylmaleimide‐sensitive factor attachment protein receptor) syntaxin 1A that is found in conventional synapses of the nervous system. In contrast, ribbon synapses of the retina contain the related isoform syntaxin 3. In addition to its localization in ribbon synapses, syntaxin 3 is also found in nonneuronal cells, where it has been implicated in the trafficking of transport vesicles to the apical plasma membrane of polarized cells. The syntaxin 3 gene codes for four different splice forms, syntaxins 3A, 3B, 3C, and 3D. We demonstrate here by using analysis of EST databases, RT‐PCR, in situ hybridization, and Northern blot analysis that cells in the mouse retina express only syntaxin 3B. In contrast, nonneuronal tissues, such as kidney, express only syntaxin 3A. The two major syntaxin isoforms (3A and 3B) have an identical N‐terminal domain but differ in the C‐terminal half of the SNARE domain and the C‐terminal transmembrane domain. These two domains are thought to be directly involved in synaptic vesicle fusion. The interaction of syntaxin 1A and syntaxin 3B with other synaptic proteins was examined. We found that both proteins bind Munc18/N‐sec1 with similar affinity. In contrast, syntaxin 3B had a much lower binding affinity for the t‐SNARE SNAP25 compared with syntaxin 1A. By using an in vitro fusion assay, we could demonstrate that vesicles containing syntaxin 3B and SNAP25 could fuse with vesicles containing synaptobrevin2/VAMP2, demonstrating that syntaxin 3B can function as a t‐SNARE. J. Comp. Neurol. 510:550–559, 2008. © 2008 Wiley‐Liss, Inc.
Photothermal Detection of Individual Gold Nanoparticles: Perspectives for High‐Throughput Screening
Authors: Kulzer Florian , Laurens Niels , Besser Jaya , Schmidt Thomas , Orrit Michel , Spaink Herman P. 
Published: July 2008

AbstractWe use photothermal microscopy to detect and image individual gold nanoparticles that are either embedded in a polymer film or immobilized in an aqueous environment. Reducing the numerical aperture of the detection optics allows us to achieve a 200‐fold‐enlarged detection volume while still retaining sufficient detectivity. We characterize the capabilities of this approach for the detection of gold colloids with a diameter of 20 nm, with emphasis on practical aspects that are important for high‐throughput‐screening applications. The extended detection volume in combination with the stability of the photothermal signal are major advantages compared to fluorescence‐based approaches, which are limited by photoblinking and photobleaching. Careful consideration is given to the trade‐off between the maximum increase in local temperature that can be tolerated by a biological specimen and the minimum integration time needed to reliably determine whether a given volume contains a target species. We find that our approach has the potential to increase the detection‐limited flow rate (i.e. the limit given by the detection volume divided by the minimum detection time) by two to three orders of magnitude.
Adsorption of 1,3‐Benzenedithiol and 1,3‐Benzenedimethanethiol on Gold Surfaces
Authors: Lim Jong Kuk , Kim Youngmin , Kwon Ohyun , Joo Sang‐Woo 
Published: July 2008

AbstractThe adsorption characteristics of 1,3‐benzenedithiol (1,3‐BDT) and 1,3‐benzenedimethanethiol (1,3‐BDMT) on Au surfaces are investigated by means of surface‐enhanced Raman scattering, UV/Vis absorption spectroscopy, and cyclic voltammetry (CV). 1,3‐BDMT is found to adsorb via two S–Au linkages at concentrations below monolayer coverage, but to have an upright geometry as the concentration increases on Au nanoparticles. On the other hand, 1,3‐BDT is found to adsorb by forming two S–Au linkages, regardless of concentration, based on the disappearance of the ν(SH)free stretching band. Because of the absence of the methylene unit, 1,3‐BDT appeares not to self‐assemble efficiently on Au surfaces. The UV/Vis absorption spectroscopy and CV techniques are also applied to check the formation of self‐assembled monolayers of 1,3‐BDT and 1,3‐BDMT on Au. Density functional theory calculations based on a simple adsorption model using an Au8 cluster are performed to better understand the nature of the adsorption characteristics of 1,3‐BDT and 1,3‐BDMT on Au surfaces.
Associative Versus Dissociative Mechanisms of Phosphate Monoester Hydrolysis: On the Interpretation of Activation Entropies
Authors: Kamerlin Shina C. L. , Florián Jan , Warshel Arieh 
Published: July 2008

AbstractPhosphate monoester and anhydride hydrolysis is ubiquitous in biology, being involved in, amongst other things, signal transduction, energy production, and the regulation of protein function. Therefore, this reaction has understandably been the focus of intensive research. Nevertheless, the precise mechanism by which phosphate monoester hydrolysis proceeds remains controversial. Traditionally, it has been assumed and frequently implied that a near‐zero activation entropy is indicative of a dissociative pathway. Herein, we examine free‐energy surfaces for the hydrolysis of the methyl phosphate dianion and the methyl pyrophosphate trianion in aqueous solution. In both cases, the reaction can proceed through either compact or expansive concerted (ANDN) transition states, with fairly similar barriers. We have evaluated the activation entropies for each transition state and demonstrate that both associative and dissociative transition states have near‐zero entropies of activation that are in good agreement with experimental values. Therefore, we believe that the activation entropy alone is not a useful diagnostic tool, as it depends not only on bond orders at the transition state, but also on other issues that include (but are not limited to) steric factors determining the configurational volumes available to reactants during the reaction, solvation and desolvation effects that may be associated with charge redistribution upon approaching the transition state and entropy changes associated with intramolecular degrees of freedom as the transition state is approached.
Significance of intercellular spaces (windows) in effusion fluid cytology: A study of 46 samples
Authors: Murugan Paari , Siddaraju Neelaiah , Habeebullah Syed , Basu Debdatta 
Published: August 2008

AbstractThe presence and nature of intercellular windows were studied on 46 body cavity fluid samples chosen on the basis of an unequivocal diagnosis on May‐Grünwald‐Giemsa (MGG)/Papanicolaou‐stained smears and cell blocks. Of these, 24 cases had adenocarcinoma (AC) and seven had reactive mesothelium (RM) with 15 having distinct populations of both. Mucicarmine and PAS stains were used wherever indicated. The specificity of windows for predicting reactive mesothelium was evaluated. Intercellular windows were found in all cases of reactive mesothelium coinciding with the presence of the fuzzy peripheral microvillous borders. Surprisingly, as many as 17/39 (44%) of the adenocarcinomas also exhibited this feature, of which 13 had a distinctly visible evenly distributed ciliated cell membrane. In addition, 30/39 (77%) cases of AC exhibited a “window‐like” appearance caused by cytoplasmic vacuolation. None of the adenocarcinoma clusters with true window formation showed positivity for the mucin stains, whereas all the clusters with pseudowindows caused by vacuolation were stained. Thus the specificity of intercellular windows for RM was merely 56%, though the sensitivity was 100%. On the other hand, the absence of windows was 100% specific for adenocarcinoma. Intercellular windows, though a feature of reactive mesothelial cell populations, can also be found in cases of ciliated adenocarcinomas and may not have a significant predictive value. Diagn. Cytopathol. 2008;36:628–632. © 2008 Wiley‐Liss, Inc.
Potential use of insulin as an anti‐inflammatory drug
Authors: Dandona Paresh , Chaudhuri Ajay , Ghanim Husam , Mohanty Priya 
Published: July 2008

AbstractAcute hyperglycemia worsens morbidity and mortality in critically ill patients. The control of hyperglycemia with insulin improves clinical outcomes in patients with a stay of more than 3–5 days in the intensive care unit (ICU) and in coronary artery bypass graft (CABG) patients. However, clinical benefits of insulin infusion have not been seen consistently in patients with acute coronary syndromes. Since all previous studies in the ICU have centered on the normalization of glycemia, we still do not know whether insulin exerts beneficial effects over and above those observed with reduction of blood glucose concentrations. The regimens used in acute coronary syndromes infuse fixed doses of insulin with high rates of glucose and are usually associated with hyperglycemia; this may neutralize the beneficial effects of insulin. In this article, we discuss data demonstrating an anti‐inflammatory effect of insulin and a pro‐inflammatory effect of glucose. We provide a mechanistic justification for the benefits of maintaining euglycemia with insulin infusions in the hospitalized patients. To investigate the clinical benefits of the anti‐inflammatory effects of insulin, we also suggest further investigations directed toward optimization of insulin infusion regimens to determine whether restoration of glucose levels toward normal with higher infusion rates and concentrations of insulin will lead to further improvement in outcomes in the critical care and acute coronary syndromes. Drug Dev Res 69:101–110, 2008 © 2008 Wiley‐Liss, Inc.
Insulin treatment in pregnancy
Authors: Trujillo Angelina 
Published: July 2008

AbstractDue to the teratogenic potential of many oral hypoglycemic agents, insulin injections are the primary treatment for diabetes in pregnant women. There has been insufficient study of insulin glargine in pregnancy. Therefore, NPH insulin continues to be the primary basal insulin used in pregnancies. The insulin requirement rises substantially in the second and third trimesters. NPH insulin and rapid‐acting insulin are mixed typically in a 1:1 ratio and administered at each main meal. The insulin pump is a viable alternative to multiple injections. During labor, insulin requirements decrease sharply, and in the post‐partum period return to the levels of the non‐pregnant state. Drug Dev Res 69:119–123, 2008.© 2008 Wiley‐Liss, Inc.
The science behind Exubera®
Authors: Schachner Holly 
Published: July 2008

AbstractFear of needles constitutes a significant barrier to the use of insulin. Lung tissue offers a large permeable surface for rapid and predictable absorption of insulin into the bloodstream. Exubera insulin was the first inhaled insulin to be approved and marketed for clinical use. The present review is intended to summarize the data to present with Exubera insulin. The pharmacodynamic effect of this inhaled insulin is similar to that of injected regular human insulin. There are small changes in lung function that parallel age‐related changes in patients who are not taking inhaled insulin. Cough occurs frequently but does not affect the overall insulin effect. Patients who start using insulin gain weight, but there is less weight gain with Exubera use than with comparable doses of injected insulin. In multiple studies, the incidence of hypoglycemia with Exubera is similar to that with regular insulin. There is concern that insulin may act as a growth factor on the lung epithelium. Recently, analysis of existing data showed that six patients on Exubera developed lung cancer compared to only one on comparator injectable insulin, all cases occurred in former smokers. However, studies were not powered for this safety issue and numbers were too small to conclude a causal relationship between Exubera exposure and occurrence of lung cancer. Pfizer decided to discontinue marketing Exubera on October 18, 2007. The decision was based upon failure to meet financial landmarks rather than due to concern about possible safety issues. Drug Dev Res 69:130–137, 2008. © 2008 Wiley‐Liss, Inc.
Preserving β Cells in Type 1 Diabetes mellitus: the role of immunological tolerance
Authors: Pillemer Stanley R. 
Published: July 2008

AbstractType 1 diabetes mellitus (T1DM) is characterized by an autoimmune attack on beta cells of the islets of Langerhans. This immunological attack is mediated by effector T‐lymphocytes and results in the destruction of the β cells. One approach to abrogating the immunological attack is to use immunosuppressive treatments. Such treatments tend to broadly suppress the immune system. A better approach is to develop treatments that induce tolerance. Autoimmune diseases are associated with the presence of inadequate numbers of functionally active regulatory T cells (Tregs). Tregs can induce a state of immunological tolerance and suppress the inflammation and destruction of target tissues. Teplizumab, also known as hOKT3γ1 (Ala‐Ala), is a humanized monoclonal antibody that induces Tregs. In clinical trials, treatment with this antibody preserved insulin production and improved metabolic control during the first year of T1DM. A pivotal multinational trial is in progress to determine the efficacy and safety of teplizumab in the treatment of new onset T1DM. Drug Dev Res 69:153–157, 2008. ©2008 Wiley‐Liss, Inc.
Vanadium(I) Chloride and Lithium Vanadium(I) Dihydride as Selective Epimetallating Reagents for π‐ and σ‐Bonded Organic Substrates
Authors: Eisch John J. , Fregene Paul O. 
Published: July 2008

AbstractSubvalent vanadium(I) salts, of empirical formulas, VCl, vanadium(I) chloride and LiVH2, lithium vanadium(I) dihydride, whose efficient preparation, structural constitution and mode of reaction toward certain organic substrates have been described in a preceding article, are here evaluated in their reactions toward a wide variety of π‐ and σ‐bonded organic substrates, namely carbonyl, imine, azo, alkene, 1,3‐diene, nitrile π‐bonds and C–X, C–O, C–N and N–N σ‐bonds. Compared with the high reactivity of CrCl and LiCrH2 reagents in attacking both types of bonds, the VCl and LiVH2 reagents were much milder and selective in epimetallating π‐bonds, often forming the 1:1 adduct of LiVH2 and π‐bonded substrate as the major product. Finally, the vanadium reagents showed little tendency to cleave C–O, C–S and C–N bonds and a smaller scope in cleaving C–X bonds than their chromium counterparts. Because of their selectivity these vanadium reagents offer the following preparative promise: 1) smooth McMurry carbonyl coupling to their reductive dimers; 2) deoxygenation of epoxides; 3) selective aromatic C–X reduction; 4) high yields of epimetallated carbonyls or imines as intermediates to ‐hydroxy and ‐amino acids; 5) 1,4‐reductions of 1,3‐alkadienes; 6) reductive dimerization of nitriles to ketones; 7) 1,4 or 1,n‐epimetallations leading to acyloins or indoles; and 8) reductive dimerizations of azines to produce unusual imidazole derivatives. In explaining the greater kinetic stability of the 1:1 LiVH2 adduct with carbonyl or imine substrates it is pointed out that such epimetallated adducts from LiVH2 would likely be diamagnetic, whereas such adducts from LiCrH2 have an unpaired electron on the Cr center and hence would rupture, so that the electron would be on the C center.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Correlations between pyrolysis combustion flow calorimetry and conventional flammability tests with halogen‐free flame retardant polyolefin compounds
Authors: Cogen Jeffrey M. , Lin Thomas S. , Lyon Richard E. 
Published: July 2008

AbstractSeven halogen‐free flame retardant (FR) compounds were evaluated using pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry. Performance of wires coated with the compounds was evaluated using industry standard flame tests. The results suggest that time to peak heat release rate (PHRR) and total heat released (THR) in cone calorimetry (and THR and temperature at PHRR in PCFC) be given more attention in FR compound evaluation. Results were analyzed using flame spread theory. As predicted, the lateral flame spread velocity was independent of PHRR and heat release capacity. However, no angular dependence of flame spread velocity was observed. Thus, the thermal theory of ignition and flame spread, which assumes that ignition at the flame front occurs at a particular flame and ignition temperature, provides little insight into the performance of the compounds. However, results are consistent with a heat release rate greater than about 66kW/m2 during flame propagation for sustained ignition of insulated wires containing mineral fillers, in agreement with a critical heat release rate criterion for burning. Mineral fillers can reduce heat release rate below the threshold value by lowering the flaming combustion efficiency and fuel content. A rapid screening procedure using PCFC is suggested by logistic regression of the binary (burn/no‐burn) results. Copyright © 2008 John Wiley & Sons, Ltd.
A computational study of gas flow in a De‐Laval micronozzle at different throat diameters
Authors: Lin C. X. , Gadepalli V. V. V. 
Published: July 2008

AbstractA numerical study has been carried out to investigate the gas flows in a micronozzle using a continuum model under both slip and no‐slip boundary conditions. The governing equations were solved with a finite volume method. The numerical model was validated with available experimental data. Numerical results of exit thrust showed good agreement with experimental data except at very low Reynolds numbers. For parametric studies on the effect of geometric scaling, the nozzle throat diameter was varied from 10 to 0.1 mm, whereas throat Reynolds number was varied from 5 to 2000. A correlation has also been developed to calculate the specific impulse at specified throat diameter and Reynolds number. The effect of different gases on the specific impulse of the nozzle, such as helium, nitrogen, argon and carbon dioxide, was also examined. Copyright © 2008 John Wiley & Sons, Ltd.