bluuebunny/crossref_metadata_2025_split huggingface dataset:
Functionalized Supramolecular Nanoporous Arrays for Surface Templating
Authors: Perdigão Luís M. A. , Saywell Alex , Fontes Giselle N. , Staniec Paul A. , Goretzki Gudrun , Phillips Anna G. , Champness Neil R. , Beton Peter H. 
Published: July 2008

AbstractControlled self‐assembly and chemical tailoring of bimolecular networks on surfaces is demonstrated using structural derivatives of 3,4:9,10‐perylenetetracarboxylic diimide (PTCDI) combined with melamine (1,3,5‐triazine‐2,4,6‐triamine). Two functionalised PTCDI derivatives have been synthesised, Br2–PTCDI and di(propylthio)–PTCDI, through attachment of chemical side groups to the perylene core. Self‐assembled structures formed by these molecules on a Ag–Si(111)${\sqrt{3}}$×${\sqrt{3}}$R30° surface were studied with a room‐temperature scanning tunneling microscope under ultrahigh vacuum conditions. It is shown that the introduction of side groups can have a significant effect upon both the structures formed, notably in the case of di(propylthio)–PTCDI which forms a previously unreported unimolecular hexagonal arrangement, and their entrapment behaviour. These results demonstrate a new route of functionalisation for network pores, opening up the possibility of designing nanostructured surface structures with chemical selectivity and applications in nanostructure templating.
Combining G‐Quadruplex Targeting Motifs on a Single Peptide Nucleic Acid Scaffold: A Hybrid (3+1) PNA–DNA Bimolecular Quadruplex
Authors: Paul Alexis , Sengupta Poulami , Krishnan Yamuna , Ladame Sylvain 
Published: July 2008

AbstractWe describe the first G‐quadruplex targeting approach that combines intercalation and hybridization strategies by investigating the interaction of a G‐rich petide nucleic acid (PNA) acridone conjugate 1 with a three‐repeat fragment of the human telomere G 3 to form a hybrid PNA–DNA quadruplex that mimicks the biologically relevant (3+1) pure DNA dimeric telomeric quadruplex. Using a combination of UV and fluorescence spectroscopy, circular dichroism (CD), and mass‐spectrometry, we show that PNA 1 can induce the formation of a bimolecular hybrid quadruplex even at low salt concentration upon interaction with a single‐stranded three‐repeat fragment of telomeric DNA. However, PNA 1 cannot invade a short fragment of B‐DNA even if the latter contains a CCC motif complementary to the PNA sequence. These studies could open up new possibilities for the design of a novel generation of quadruplex ligands that target not only the external features of the quadruplex but also its central core constituted by the tetrads themselves.
Intermolecular Alkene and Alkyne Hydroacylation with β‐S‐Substituted Aldehydes: Mechanistic Insight into the Role of a Hemilabile P–O–P Ligand
Authors: Moxham Gemma L. , Randell‐Sly Helen , Brayshaw Simon K. , Weller Andrew S. , Willis Michael C. 
Published: July 2008

AbstractA straightforward to assemble catalytic system for the intermolecular hydroacylation reaction of β‐S‐substituted aldehydes with activated and unactivated alkenes and alkynes is reported. These catalysts promote the hydroacylation reaction between β‐S‐substituted aldehydes and challenging substrates, such as internal alkynes and 1‐octene. The catalysts are based upon [Rh(cod)(DPEphos)][ClO4] (DPEphos=bis(2‐diphenylphosphinophenyl)ether, cod=cyclooctadiene) and were designed to make use of the hemilabile capabilities of the DPEphos ligand to stabilise key acyl–hydrido intermediates against reductive decarbonylation, which results in catalyst death. Studies on the stoichiometric addition of aldehyde (either ortho‐HCOCH2CH2SMe or ortho‐HCOC6H4SMe) and methylacrylate to precursor acetone complexes [Rh(acetone)2(DPEphos)][X] [X=closo‐CB11H6Cl6 or [BArF4] (ArF = 3,5‐(CF3)2C6H3)] reveal the role of the hemilabile DPEphos ligand. The crystal structure of [Rh(acetone)2(DPEphos)][X] shows a cis‐coordinated diphosphine ligand with the oxygen atom of the DPEphos distal from the rhodium. Addition of aldehyde forms the acyl hydride complexes [Rh(DPEphos)(COCH2CH2SMe)H][X] or [Rh(DPEphos)(COC6H4SMe)H][X], which have a trans‐spanning DPEphos ligand and a coordinated ether group. Compared to analogous complexes prepared with dppe (dppe=1,2‐bis(diphenylphosphino)ethane), these DPEphos complexes show significantly increased resistance towards reductive decarbonylation. The crystal structure of the reductive decarbonylation product [Rh(CO)(DPEphos)(EtSMe)][closo‐CB11H6I6] is reported. Addition of alkene (methylacrylate) to the acyl–hydrido complexes forms the final complexes [Rh(DPEphos)(η1‐MeSC2H4‐η1‐COC2H4CO2Me)][X] and [Rh(DPEphos)(η1‐MeSC6H4‐η1‐COC2H4CO2Me)][X], which have been identified spectroscopically and by ESIMS/MS. Intermediate species in this transformation have been observed and tentatively characterised as the alkyl–acyl complexes [Rh(CH2CH2CO2Me)(COC2H4SMe)(DPEphos)][X] and [Rh(CH2CH2CO2Me)(COC6H4SMe)(DPEphos)][X]. In these complexes, the DPEphos ligand is now cis chelating. A model for the (unobserved) transient alkene complex that would result from addition of alkene to the acyl–hydrido complexes comes from formation of the MeCN adducts [Rh(DPEphos)(MeSC2H4CO)H(MeCN)][X] and [Rh(DPEphos)(MeSC6H4CO)H(MeCN)][X]. Changing the ligand from DPEphos to one with a CH2 linkage, [Ph2P(C6H4)]2CH2, gave only decomposition on addition of aldehyde to the acetone precursor, which demonstrated the importance of the hemiabile ether group in DPEphos. With [Ph2P(C6H4)]2S, the sulfur atom has the opposite effect and binds too strongly to the metal centre to allow access to productive acetone intermediates.
Textural Manipulation of Mesoporous Materials for Hosting of Metallic Nanocatalysts
Authors: Sun Junming , Bao Xinhe 
Published: July 2008

AbstractThe preparation and stabilization of nanoparticles are becoming very crucial issues in the field of so‐called “nanocatalysis”. Recent developments in supramolecular self‐assembled porous materials have opened a new way to get nanoparticles hosted in the channels of such materials. In this paper, a new approach towards monodisperse and thermally stable metal nanoparticles by confining them in ordered mesoporous materials is presented, and three aspects are illustrated. Firstly, the recent progress in the functional control of mesoporous materials will be briefly introduced, and the rational tuning of the textures, pore size, and pore length is demonstrated by controlling supramolecular self‐assembly behavior. A novel synthesis of short‐pore mesoporous materials is emphasized for their easy mass transfer in both biomolecule absorption and the facile assembly of metal nanocomposites within their pore channels. In the second part, the different routes for encapsulating monodisperse nanoparticles inside channels of porous materials are discussed, which mainly includes the ion‐exchange/conventional incipient wetness impregnation, in situ encapsulation routes, organometallic methodologies, and surface functionalization schemes. A facile in situ autoreduction route is highlighted to get monodisperse metal nanoparticles with tunable sizes inside the channels of mesoporous silica. Finally, confinement of mesoporous materials is demonstrated to improve the thermal stability of monodisperse metal nanoparticles catalysts and a special emphasis will be focused on the stabilization of the metal nanoparticles with a low Tammann temperature. Several catalytic reactions concerning the catalysis of nanoparticles will be presented. These uniform nanochannels, which confine monodisperse and stable metal nanoparticles catalysts, are of great importance in the exploration of size‐dependent catalytic chemistry and further understanding the nature of catalytic reactions.
Folate‐Equipped Pegylated Archaeal Lipid Derivatives: Synthesis and Transfection Properties
Authors: Lainé Céline , Mornet Emmanuel , Lemiègre Loïc , Montier Tristan , Cammas‐Marion Sandrine , Neveu Cécile , Carmoy Nathalie , Lehn Pierre , Benvegnu Thierry 
Published: July 2008

AbstractWe have previously shown that synthetic archaeal lipid analogues are useful vectors for drug/gene delivery. We report herein the synthesis and gene transfer properties of a series of novel di‐ and tetraether‐type archaeal derivatives with a poly(ethylene glycol) (PEG) chain and further equipped with a folic acid (FA) group. The synthetic strategy and the purification by dialysis ensured complete removal of free FA. The lipids were mixed with a conventional glycine betaine‐based cationic lipid and the resulting formulations were tested in transfection assays after complexation with plasmid DNA. All four novel co‐lipids afforded efficient in vitro gene transfection. Moreover, the FA‐equipped derivatives permitted ligand/receptor‐based targeted transfection; their activity was inhibited when free FA was added to the transfection medium. These novel archaeal derivatives equipped with FA‐PEG moieties may thus be of great interest for targeted in vivo transfection.
A Simple and Efficient Strategy To Enhance the Antioxidant Activities of Amino‐Substituted Glutathione Peroxidase Mimics
Authors: Bhabak Krishna P. , Mugesh Govindasamy 
Published: July 2008

AbstractThe glutathione peroxidase (GPx) activities of some diaryl diselenides incorporating tertiary amino groups were studied with H2O2, Cum‐OOH, and tBuOOH as substrates and with PhSH as thiol co‐substrate. Simple replacement of a hydrogen atom with a methoxy group dramatically enhances the GPx activity. The introduction of methoxy substituents ortho to selenium in N,N‐dialkylbenzylamine‐based compounds makes the basicity of the amino groups perfect for the catalysis. The presence of 6‐OMe groups prevents possible Se⋅⋅⋅N interactions in the selenols, increasing their zwitterionic characters. The methoxy substituents also protect the selenium in the selenenic acid intermediates from overoxidation to seleninic acids or irreversible inactivation to selenonic acid derivatives. The additional substituents also play a crucial role in the selenenyl sulfide intermediates, by preventing thiol exchange reactions—which would normally lead to an inactivation pathway—at the selenium centers. The strengths of Se⋅⋅⋅N interactions in the selenenyl sulfide intermediates are dramatically reduced upon introduction of the methoxy substituents, which not only reduce the thiol exchange reactions at selenium but also enhance the nucleophilic attack of the incoming thiols at sulfur. The facile attack of thiols at sulfur in the selenenyl sulfides also prevents the reactions between the selenenyl sulfides and H2O2 that can regenerate the selenenic acids (reverse‐GPx cycle). These studies reveal that the simple 6‐OMe groups play multiple roles in each of the catalytically active intermediates by introducing steric and electronic effects that are required for efficient catalysis.
TEMPO Supported on Magnetic C/Co‐Nanoparticles: A Highly Active and Recyclable Organocatalyst
Authors: Schätz Alexander , Grass Robert N. , Stark Wendelin J. , Reiser Oliver 
Published: July 2008

AbstractTEMPO was grafted on graphene‐coated nanobeads with a magnetic cobalt core by using a general applicable “click”‐chemistry protocol. The new heterogeneous CoNP–TEMPO emerged as a highly active catalyst for the chemoselective oxidation of primary and secondary alcohols using bleach as terminal oxidant. The outstanding stability of the C/Co nanoparticles enables the nanopowder to tolerate several TEMPO‐mediated iterative oxidation reactions without any significant loss in catalyst activity. Furthermore, the excellent magnetic properties enable the rapid separation and quantitative recycling of CoNP–TEMPO out of the reaction mixture by simple magnetic decantation. The recovered nanoparticles can be subsequently reused without any further purification.
Pt@MOF‐177: Synthesis, Room‐Temperature Hydrogen Storage and Oxidation Catalysis
Authors: Proch Sebastian , Herrmannsdörfer Justus , Kempe Rhett , Kern Christoph , Jess Andreas , Seyfarth Lena , Senker Jürgen 
Published: July 2008

AbstractThe gas‐phase loading of [Zn4O(btb)2]8 (MOF‐177; H3btb=1,3,5‐benzenetribenzoic acid) with the volatile platinum precursor [Me3PtCp′] (Cp′=methylcyclopentadienyl) was confirmed by solid state 13C magic angle spinning (MAS)‐NMR spectroscopy. Subsequent reduction of the inclusion compound [Me3PtCp′]4@MOF‐177 by hydrogen at 100 bar and 100 °C for 24 h was carried out and gave rise to the formation of platinum nanoparticles in a size regime of 2–5 nm embedded in the unchanged MOF‐177 host lattice as confirmed by transmission electron microscopy (TEM) micrographs and powder X‐ray diffraction (PXRD). The room‐temperature hydrogen adsorption of Pt@MOF‐177 has been followed in a gravimetric fashion (magnetic suspension balance) and shows almost 2.5 wt % in the first cycle, but is decreased down to 0.5 wt % in consecutive cycles. The catalytic activity of Pt@MOF‐177 towards the solvent‐ and base‐free room temperature oxidation of alcohols in air has been tested and shows Pt@MOF‐177 to be an efficient catalyst in the oxidation of alcohols.
Assessing Synthetic Strategies: Total Syntheses of (±)‐Neodolabellane‐Type Diterpenoids
Authors: Valente Cory , Organ Michael G. 
Published: July 2008

AbstractTwo strategies, namely a cross‐metathesis/ring‐closing metathesis and Pd‐catalyzed Stille allylation/Nozaki–Hiyama–Kishi coupling, are examined for the preparation of neodolabellane‐type diterpenoids 1 and 2. Whereas the first approach possessed synthetic limitations, the latter was successfully employed to provide compounds 1 and 2 in 8.8 % (14 steps) and 8 % (15 steps) overall yields, respectively.
Structure–Activity Relationships of Phenylalkylamines as Agonist Ligands for 5‐HT2AReceptors
Authors: Blaazer Antoni R. , Smid Pieter , Kruse Chris G. 
Published: July 2008

AbstractAgonist activation of central 5‐HT2Areceptors results in diverse effects, such as hallucinations and changes of consciousness. Recent findings indicate that activation of the 5‐HT2Areceptor also leads to interesting physiological responses, possibly holding therapeutic value. Selective agonists are needed to study the full therapeutic potential of this receptor. 5‐HT2Aligands with agonist profiles are primarily derived from phenylalkylamines, indolealkylamines, and certain piperazines. Of these, phenylalkylamines, most notably substituted phenylisopropylamines, are considered the most selective agonists for 5‐HT2receptors. This review summarizes the structure–activity relationships (SAR) of phenylalkylamines as agonist ligands for 5‐HT2Areceptors. Selectivity is a central theme, as is selectivity for the 5‐HT2Areceptor and for its specific signaling pathways. SAR data from receptor affinity studies, functional assays, behavioral drug discrimination as well as human studies are discussed.
Distribution of voltage‐gated potassium and hyperpolarization‐activated channels in sensory afferent fibers in the rat carotid body
Authors: Buniel Maria , Glazebrook Patricia A. , Ramirez‐Navarro Angelina , Kunze Diana L. 
Published: July 2008

AbstractThe chemosensory glomus cells of the carotid body (CB) detect changes in O2 tension. Carotid sinus nerve fibers, which originate from peripheral sensory neurons located within the petrosal ganglion, innervate the CB. Release of transmitter from glomus cells activates the sensory afferent fibers to transmit information to the nucleus of the solitary tract in the brainstem. The ion channels expressed within the sensory nerve terminals play an essential role in the ability of the terminal to initiate action potentials in response to transmitter‐evoked depolarization. However, with a few exceptions, the identity of ion channels expressed in these peripheral nerve fibers is unknown. This study addresses the expression of voltage‐gated channels in the sensory fibers with a focus on channels that set the resting membrane potential and regulate discharge patterns. By using immunohistochemistry and fluorescence confocal microscopy, potassium channel subunits and HCN (hyperpolarization‐activated) family members were localized both in petrosal neurons that expressed tyrosine hydroxylase and in the CSN axons within the carotid body. Channels contributing to resting membrane potential, including HCN2 responsible in part for Ih current and the KCNQ2 and KCNQ5 subunits thought to underlie the neuronal “M current,” were identified in the sensory neurons and their axons innervating the carotid body. In addition, the results presented here demonstrate expression of several potassium channels that shape the action potential and the frequency of discharge, including Kv1.4, Kv1.5, Kv4.3, and KCa (BK). The role of these channels should be considered in interpretation of the fiber discharge in response to perturbation of the carotid body environment. J. Comp. Neurol. 510:367–377, 2008. © 2008 Wiley‐Liss, Inc.
Solvent as a Probe of Active Site Motion and Chemistry during the Hydrogen Tunnelling Reaction in Morphinone Reductase
Authors: Hay Sam , Pudney Christopher R. , Sutcliffe Michael J. , Scrutton Nigel S. 
Published: July 2008

AbstractThe reductive half‐reaction of morphinone reductase involves a hydride transfer from enzyme‐bound β‐nicotinamide adenine dinucleotide (NADH) to a flavin mononucleotide (FMN). We have previously demonstrated that this step proceeds via a quantum mechanical tunnelling mechanism. Herein, we probe the effect of the solvent on the active site chemistry. The pKa of the reduced FMN N1 is 7.4±0.7, based on the pH‐dependence of the FMN midpoint potential. We rule out that protonation of the reduced FMN N1 is coupled to the preceding H‐transfer as both the rate and temperature‐dependence of the reaction are insensitive to changes in solution pH above and below this pKa. Further, the solvent kinetic isotope effect is ∼1.0 and both the 1° and 2° KIEs are insensitive to solution pH. The effect of the solvent’s dielectric constant is investigated and the rate of H‐transfer is found to be unaffected by changes in the dielectric constant between ∼60 and 80. We suggest that, while there is crystallographic evidence for some water in the active site, the putative promoting motion involved in the H‐tunnelling reaction is insensitive to such changes.
A linearly adaptive gate drive technique for light‐load efficiency improvement of DC–DC converters
Authors: Liu Pang‐Jung , Chen Yi‐Jan Emery 
Published: July 2008

AbstractThis paper presents a linearly adaptive gate drive technique to improve the light‐load efficiency of DC–DC converters. The optimal‐driving voltages of the power MOSFETs for reducing gate‐driving loss can be well modeled by a linear function of the load current. By scaling the gate drive voltage dynamically with respect to load current, the light‐load efficiency can be enhanced. The experimental result shows that the proposed gate drive technique can attain about 9% incremental light‐load efficiency enhancement. Copyright © 2008 John Wiley & Sons, Ltd.
Insulin: moments in history
Authors: Rendell Marc 
Published: July 2008

AbstractThe isolation of insulin by Banting and Best in 1922 was a historic event of life‐saving importance. Thousands of individuals doomed to die of type I diabetes were saved. The inspiring story of insulin continued to grow and evolve with the development of PZI, NPH, and lente insulins. The advent of production of human insulin from recombinant DNA brought an end to the extraction of insulin from animal pancreas. Modification of the amino acid sequences of insulin led to new forms of fast‐acting insulin, such as lispro, aspart, and glulisine, and to long‐acting insulins like glargine and detemir. The technology of insulin pumps advanced from large, cumbersome equipment to present‐day devices no bigger than a hand calculator. The accuracy of implantable glucose sensors improved progressively, culminating in the approval of devices that will soon exert reliable feedback control of insulin pumps. Transplantation of the pancreas offers a cure for type I diabetes, and the development of islet cell transplantation continues. It is now appreciated that islet cells regenerate in the normal pancreas, and islet cell neogenesis agents have been identified and may eventually contribute to the reversal of diabetes. Drug Dev Res 69:95–100, 2008. ©2008 Wiley‐Liss, Inc.
Mechanisms of β cell failure in the pathogenesis of Type 2 diabetes
Authors: Accili Domenico 
Published: July 2008

Abstractβ cell failure plays a key role in the pathogenesis of type 2 diabetes. It consists of impaired insulin secretion and decreased β cell mass. Recent insight into the pathogenesis of diabetes‐associated β cell failure has shown that (1) β cell compensation to insulin resistance occurs primarily via increased β cell replication; (2) commonly employed diabetes treatments are associated with a seemingly irreversible loss of β cell function; and (3) most diabetes‐associated genes identified in recent genome‐wide association studies appear to regulate β cell mass and/or function, as opposed to insulin action. Experimental studies in animal models have contributed to establishing the idea that pancreatic β cells are an “insulin target tissue,” in which insulin signaling links insulin secretion with cellular proliferation and survival. It is possible that β cell failure represents but another aspect of insulin resistance. Prevention of β cell dysfunction is a critical goal of diabetes therapy, and it will require the identification of “druggable” cellular pathways that can be enlisted in the clinic to achieve durability of treatment. Drug Dev Res 69:111–115, 2008 © 2008 Wiley‐Liss, Inc.
Initiating insulin in type 2 diabetes
Authors: Dailey George 
Published: July 2008

AbstractThere are a variety of oral hypoglycemic agents available for use in type 2 diabetes. Despite the increasing choices of oral agents, insulin therapy remains the most effective means to lower blood glucose and often must be used. There is some controversy as to the best approach to the initiation of insulin treatment in type 2 diabetes. The approach we favor begins with basal insulin with later addition of premeal rapid‐acting insulin. Drug Dev Res 69:116–118, 2008. © 2008 Wiley‐Liss, Inc.
Insulin treatment of post‐prandial hyperglycemia
Authors: Rendell Marc S. 
Published: July 2008

AbstractWith evidence that elevated post‐prandial glucose (PPG) is a major risk factor for cardiovascular disease, there is increasing emphasis on primary treatment of PPG in diabetes. The carbohydrate content of a meal is the principal contribution to PPG, so efforts to reduce carbohydrate ingestion are an important dietary approach to management. Although all oral hypoglycemics reduce PPG, newer agents including disaccharidase inhibitors and meglitinides act more selectively to lower PPG. GLP‐1 agonists and pramlintide act primarily on post‐meal glucose. DPP‐IV inhibitors are oral agents that raise GLP‐1 levels. Unquestionably, exogenous insulin is the most potent agent to lower PPG levels. Long‐acting basal insulin has much less effect on PPG than rapid‐acting insulin taken at the time of a meal. Inhaled insulin is no more effective than injectable insulin but is much more acceptable to most patients and may thus lead to administration of insulin earlier in the course of type II diabetes. Drug Dev Res 69:124–129, 2008. © 2008 Wiley‐Liss, Inc.