bluuebunny/crossref_metadata_2025_split huggingface dataset:
Shedding New Light on ZnCl2‐Mediated Addition Reactions of Grignard Reagents to Ketones: Structural Authentication of Key Intermediates and Diffusion‐Ordered NMR Studies
Authors: Armstrong David R. , Clegg William , García‐Alvarez Pablo , McCall Matthew D. , Nuttall Lorraine , Kennedy Alan R. , Russo Luca , Hevia Eva 
Published: March 2011

AbstractBuilding on recent advances in synthesis showing that the addition of inorganic salts to Grignard reagents can greatly enhance their performance in alkylation reactions to ketones, this study explores the reactions of EtMgCl with benzophenone in the presence of stoichiometric or catalytic amounts of ZnCl2 with the aim of furthering the understanding of the role and constitution of the organometallic species involved in these transformations. Investigations into the metathesis reactions of three molar equivalents of EtMgCl with ZnCl2 led to the isolation and characterisation (X‐ray crystallography and 1H and 13C NMR spectroscopy) of novel magnesium “zinc‐rich” zincate [{(THF)6Mg2Cl3}+{Zn2Et5}−] (1), whose complicated constitution in THF solutions was assessed by variable‐temperature 1H DOSY NMR studies. Compound 1 reacted with one equivalent of benzophenone to yield magnesium magnesiate [{(THF)6Mg2Cl3}+{Mg2(OC(Et)Ph2)2Cl3(THF)}−] (3), whose structure was determined by X‐ray crystallography. 1H NMR monitoring of this reaction showed two equivalents of ZnEt2 formed as a co‐product, which together with the “magnesium only constitution” of 3 provides experimental insights into how zinc can be efficiently recycled in these reactions, and therefore used catalytically. The chemoselectivity of this reaction can be rationalised in terms of the synergic effect of magnesium and zinc and contrasts with the results obtained when benzophenone was allowed to react with EtMgCl in the absence of ZnCl2, where the reduction of the ketone takes place preferentially. The reduction product [{(THF)5Mg3Cl4{OC(H)Ph(CF3)}2] (4) obtained from the reaction of EtMgCl with 2,2,2‐trifluoroacetophenone was established by X‐ray crystallography and multinuclear (1H, 13C and 19F) NMR spectroscopy. Compounds 3 and 4 exhibit new structural motifs in magnesium chemistry having MgCl2 integrated within their constitution, which highlights the new role of this inorganic salt in providing structural support for the newly generated alkoxide ligand.
Pseudo‐Bimolecular [2+2] Cycloaddition Studied by Time‐Resolved Photoelectron Spectroscopy
Authors: Brogaard Rasmus Y. , Boguslavskiy Andrey E. , Schalk Oliver , Enright Gary D. , Hopf Henning , Raev Vitaly A. , Jones Peter G. , Thomsen Ditte L. , Sølling Theis I. , Stolow Albert 
Published: March 2011

AbstractThe first study of pseudo‐bimolecular cycloaddition reaction dynamics in the gas phase is presented. We used femtosecond time‐resolved photoelectron spectroscopy (TRPES) to study the [2+2] photocycloaddition in the model system pseudo‐gem‐divinyl[2.2]paracyclophane. From X‐ray crystal diffraction measurements we found that the ground‐state molecule can exist in two conformers; a reactive one in which the vinyl groups are immediately situated for [2+2] cycloaddition and a nonreactive conformer in which they point in opposite directions. From the measured S1 lifetimes we assigned a clear relation between the conformation and the excited‐state reactivity; the reactive conformer has a lifetime of 13 ps, populating the ground state through a conical intersection leading to [2+2] cycloaddition, whereas the nonreactive conformer has a lifetime of 400 ps. Ab initio calculations were performed to locate the relevant conical intersection (CI) and calculate an excited‐state [2+2] cycloaddition reaction path. The interpretation of the results is supported by experimental results on the similar but nonreactive pseudo‐para‐divinyl[2.2]paracyclophane, which has a lifetime of more than 500 ps in the S1 state.
Liquid chromatographic resolution of 3‐amino‐1,4‐benzodiazepin‐2‐one derivatives on various Pirkle‐type chiral stationary phases
Authors: Park Je Young , Cho Hwan Sun , Hyun Myung Ho 
Published: March 2011

AbstractThe two enantiomers of N‐acyl amide and N‐ureide derivatives of 3‐amino‐5‐phenyl‐1,4‐benzodiazepin‐2‐ones, which have been known to show anti‐respiratory syncytial virus (RSV) activity, were resolved on seven different Pirkle‐type chiral stationary phases (CSPs) with the use of 10% isopropyl alcohol in hexane as a mobile phase. Among the seven Pirkle‐type CSPs, the one based on (S)‐leucine derivative named as N‐Phe‐L‐Leu was found to be most successful, the separation factors (α) and the resolutions (RS) for seven analytes being in the range of 1.78–4.21 and 5.94–15.08, respectively. By resolving N‐benzyloxycarbonyl derivatives of 3‐amino‐5‐phenyl(or 5‐methyl)‐1,4‐benzodiazepin‐2‐ones on Pirkle‐type CSPs, the phenyl ring at the 5‐position and the NH hydrogen at the 1‐position of analytes were found to play an important role in the chiral recognition. Chirality, 2011. © 2011 Wiley Periodicals, Inc.
The domain organization of the bacterial intermediate filament‐like protein crescentin is important for assembly and function
Authors: Cabeen Matthew T. , Herrmann Harald , Jacobs‐Wagner Christine 
Published: March 2011

AbstractCrescentin is a bacterial filament‐forming protein that exhibits domain organization features found in metazoan intermediate filament (IF) proteins. Structure‐function studies of eukaryotic IFs have been hindered by a lack of simple genetic systems and easily quantifiable phenotypes. Here we exploit the characteristic localization of the crescentin structure along the inner curvature of Caulobacter crescentus cells and the loss of cell curvature associated with impaired crescentin function to analyze the importance of the domain organization of crescentin. By combining biochemistry and ultrastructural analysis in vitro with cellular localization and functional studies, we show that crescentin requires its distinctive domain organization, and furthermore that different structural elements have distinct structural and functional contributions. The head domain can be functionally subdivided into two subdomains; the first (amino‐terminal) is required for function but not assembly, while the second is necessary for structure assembly. The rod domain is similarly required for structure assembly, and the linker L1 appears important to prevent runaway assembly into nonfunctional aggregates. The data also suggest that the stutter and the tail domain have critical functional roles in stabilizing crescentin structures against disassembly by monovalent cations in the cytoplasm. This study suggests that the IF‐like behavior of crescentin is a consequence of its domain organization, implying that the IF protein layout is an adaptable cytoskeletal motif, much like the actin and tubulin folds, that is broadly exploited for various functions throughout life from bacteria to humans. © 2011 Wiley‐Liss, Inc.
Hematology/oncology fellows' training in palliative care
Authors: Buss Mary K. , Lessen David S. , Sullivan Amy M. , Von Roenn Jamie , Arnold Robert M. , Block Susan D. 
Published: March 2011

AbstractBACKGROUND:Palliative care is recognized as integral to the practice of oncology, yet many oncologists report inadequate training in critical palliative care domains, such as symptom management, psychosocial care, and communication skills. The authors of this report sought to assess the quantity and quality of palliative care education within oncology fellowships.METHODS:Second‐year oncology fellows completed a 104‐item survey that was modified and adapted from a national survey of medical students and residents. Items allowed comparison between palliative care and nonpalliative care topics.RESULTS:Of 402 eligible fellows, 63.2% responded (n = 254). Respondents were: 52% men, 62% Caucasian, and 64% US medical school graduates. Twenty‐six percent had completed a palliative care rotation. Fellows rated the overall quality of fellowship teaching more highly than teaching on palliative care (3.7 v 3.0 on a 1‐5 scale; t = 10.2; P < .001). Rates of being observed (81%) and receiving feedback (80%) on an end‐of‐life communication skill were high. Psychosocial needs of patients received some attention: Fifty‐seven percent of fellows reported that they were conveyed as a core competency, but only 32% of fellows received explicit education on assessing and managing depression at the end of life. Fellows rarely reported receiving explicit education on opioid rotation (33%). Fellows scored a median of 2 of 4 items that tested basic palliative care knowledge, and only 23% correctly performed an opioid conversion.CONCLUSIONS:Fellows rated the quality of palliative care education as inferior to overall oncology training and may benefit from more teaching on pain management, psychosocial care, and communication skills. Cancer 2011;. © 2011 American Cancer Society.
Improved survival in patients with lymph node‐positive gastric cancer who received preoperative radiation
Authors: Shridhar Ravi , Dombi George W. , Finkelstein Steven E. , Meredith Kenneth L. , Hoffe Sarah E. 
Published: March 2011

AbstractBACKGROUND:Several trials have been conducted to determine the feasibility of preoperative radiotherapy (RT) for gastric cancer. However, the absolute benefit from radiotherapy remains to be defined. In this study, the authors examined the use of preoperative RT (Pre‐RT) and postoperative RT (PORT) in patients with gastric cancer from the Surveillance, Epidemiology, and End Results (SEER) database.METHODS:The overall survival of patients who had nonmetastatic, resected gastric cancer between 2000 and 2006 was analyzed from the SEER database. Kaplan‐Meier survival curves comparing Pre‐RT, PORT, and no RT (No‐RT) were analyzed using the log‐rank test. A multivariate analysis (MVA) was conducted using Cox proportional hazards regression.RESULTS:The authors identified 10,251 patients. There was no survival benefit for patients who received Pre‐RT or PORT compared with No‐RT patients for the entire cohort. Conversely, among lymph node‐positive patients, there was a significant survival benefit from both Pre‐RT and PORT compared with No‐RT (log‐rank test: PORT, P < .0001; Pre‐RT, P = .0261). The median survival and 5‐year overall survival among lymph node‐positive patients were 22 months and 24%, respectively, for Pre‐RT;29 months and 34%, respectively, for PORT; and 19 months and 20%, respectively, for No‐RT. MVA demonstrated that Pre‐RT, PORT, and removing ≥15 lymph nodes were independent predictors of improved survival, whereas tumor classification, lymph node status, tumor size, and tumor location were independent predictors of death.CONCLUSIONS:The current results supported the use of Pre‐RT in select patients with gastric cancer. However, additional trials will be needed to confirm these findings. Cancer 2011;. © 2011 American Cancer Society.
Incidence and mortality in epithelial ovarian cancer by family history of any cancer
Authors: Hemminki Kari , Sundquist Jan , Brandt Andreas 
Published: March 2011

AbstractBACKGROUND:Practically all data on familial risk in ovarian and other cancers are based on incident cancer, whereas familiality in cancer mortality is largely unknown. If fatal forms of cancer are a highly familial subtype, then familial risk for mortality may exceed that of incidence, which is relevant for clinical decision making and counseling.METHODS:Ovarian cancer patients in the nationwide Swedish Family Cancer Database were classified according to fatal and nonfatal (incident) family history. Familial risks for incident and fatal ovarian cancer were calculated for offspring based on their parental or sibling family history of any cancer using standardized incidence ratios (SIRs) for incidence and standardized mortality ratios (SMRs) for mortality. Offspring without family history were referents.RESULTS:The database included 24,757 mothers and 8138 daughters with ovarian cancer. When a mother had ovarian cancer, the SIR for incident ovarian cancer in daughters was 2.69, and when a sister had ovarian cancer it was 3.49. The SMRs for fatal cancer by fatal cancer in probands were 3.39 and 5.80, respectively. For fatal serous cancers among siblings, the SMR was 6.16, compared with 10.01 for the endometrioid type. Ovarian cancer was associated with maternal (SIR, 1.22; SMR, 1.56) and sororal breast cancer (SIR, 1.27). Another discordant association was between ovarian and paternal prostate cancer (SIR, 1.12; SMR, 1.66).CONCLUSIONS:Fatal familial risks were higher for concordant ovarian, ovarian‐breast, and ovarian‐prostate cancers than the corresponding incident risks. This may suggest that highly fatal subtypes exist for these cancers, calling for genetic dissection. Cancer 2011. © 2011 American Cancer Society.
Effect of Surface Modification on Semiconductor Nanocrystal Fluorescence Lifetime
Authors: Ruedas‐Rama Maria J. , Orte Angel , Hall Elizabeth A. H. , Alvarez‐Pez Jose M. , Talavera Eva M. 
Published: March 2011

AbstractSemiconductor nanocrystals, namely, quantum dots (QDs), present a set of unique photoluminescence properties, which has led to increased interest in using them as advantageous alternatives to conventional organic dyes. Many applications of QDs involve surface modification to enhance the solubility or biocompatibility of the QDs. One of the least exploited properties of QDs is the very long photoluminescence lifetime that usually has complex kinetics owing to the effect of quantum confinement. Herein, we describe the effect of different surface modifications on the photoluminescence decay kinetics of QDs. The different surface modifications were carefully chosen to provide lipophilic or water‐soluble QDs with either positive or negative surface net charges. We also survey the effect on the QD lifetime of several ligands that interact with the QD surface, such as organic chromophores or fluorescent proteins. The results obtained demonstrate that time‐resolved fluorescence is a useful tool for QD‐based sensing to set the basis for the development of time‐resolved‐based nanosensors.
From tert‐Butylhydrazine Adducts of AlR3 (R = Me, CMe3) to Oligonuclear AlN Cage Compounds – Evidence for a Hydrazine Twist Across an Al3 Triangle
Authors: Uhl Werner , Hagemeier Elke , Layh Marcus , Rezaeirad Babak , Kösters Jutta , Würthwein Ernst‐Ulrich , Ghavtadze Nugzar , Massa Werner 
Published: March 2011

AbstractThe thermal decomposition of the hydrazine adducts R3Al←NH2–N(H)CMe3 (1a, R = CMe3; 1b, R = Me) was investigated. Compound 1a afforded the hydrazide [(Me3C)2Al–N(H)–N(H)–CMe3]2 (2) upon heating to 155 °C. Compound 2 is dimeric in the solid state with a four‐membered Al2N2 heterocycle in its molecular core. Heating of 2 to 190 °C gave the drum‐like imidoalane [Me3CAlNH]6 (4) in which the Al and N atoms occupy the vertices of a hexagonal prism. This reaction is believed to proceed via the dimeric amide [(Me3C)2Al–NH2]2 (3) that was isolated in small quantities from a mixture obtained at a slightly lower temperature. Adduct 1b, which is sterically less shielded than 1a, decomposes readily at room temperature to yield an unprecedented Al–N cage compound, [Me2Al–N(H)–N(H)CMe3]2[MeAl–N(CMe3)–NH] (5), with a norbornane‐like arrangement of three Al and four N atoms, and a hydrazinediido group in the bridging position. Heating of 5 gave, with the release of methane, the tetraaluminum compound [MeAlN(H)–NCMe3]4 (6) in which four hydrazinediide moieties are bridged by AlMe groups. Heating of 6 resulted in the gradual degradation of the N–N bonds and the formal release of 1 or 3 equiv. of nitrene, N–H, to give the unique cage compounds (MeAl)4[N(H)–NCMe3]3(NCMe3) (7) and (MeAl)4[N(H)–NCMe3](NCMe3)3 (8). The structures of compounds 6–8 may be derived from Al4N4 cubes in which a number of edges (four, three or one) are bridged by nitrogen atoms of hydrazinediido groups.
Site‐Selective Arylation of Alizarin and Purpurin Based on Suzuki–Miyaura Cross‐Coupling Reactions
Authors: Mahal Ahmed , Villinger Alexander , Langer Peter 
Published: March 2011

AbstractA variety of arylated anthraquinones were prepared by site‐selective Suzuki–Miyaura cross‐coupling reactions of the bis‐ and tris(triflates) of alizarin and purpurin, respectively. The site‐selectivity is controlled by the electronic influence of the carbonyl group and by steric parameters.
Efficient Tandem Morita–Baylis–Hillman/Double Cross‐Aldol Reaction between Cyclic Enones and Formaldehyde Promoted by N‐Methylpyrrolidine
Authors: Guerra Krassimira P. , Afonso Carlos A. M. 
Published: March 2011

AbstractThe Lewis base N‐methylpyrrolidine acts in water as an efficient promoter of tandem reactions between 2 cyclopenten‐1‐one and aqueous formaldehyde. The reaction pathway includes, as consecutive independent steps, a MBH reaction and a double cross‐aldol reaction to furnish the new 2,5,5‐tris(hydroxymethyl)‐2‐cyclopenten‐1‐one in excellent yield. A range of cyclic enones and 4‐nitrobenzaldehyde undergo the tandem reaction similarly. The reaction mechanism was also investigated.
Synthesis and Photophysical Properties of Alkynylated Pyrimidines by Site‐Selective Sonogashira Reactions of 2,4,5,6‐Tetrachloropyrimidine; First Synthesis of Tetraalkynyl‐pyrimidines
Authors: Malik Imran , Ahmed Zeeshan , Reimann Sebastian , Ali Iftikhar , Villinger Alexander , Langer Peter 
Published: March 2011

AbstractA variety of novel alkynyl‐substituted pyrimidines were prepared by the first site‐selective Sonogashira cross‐coupling reactions of 2,4,5,6‐tetrachloropyrimidine. The products, di‐, tri‐, and tetraalkynyl‐pyrimidines, exhibit fluorescence in the range of 395–470 nm. The synthesis of tetraalkynyl‐pyrimidines has not been previously reported, nor has the synthesis of chlorinated di‐ and trialkynylated pyrimidines.
Efficient Access to C1‐ and C3‐Functionalized Isoquinolines: Towards Potential Lanthanide Ligands
Authors: Caillé Fabien , Buron Frédéric , Tóth Éva , Suzenet Franck 
Published: March 2011

AbstractHighly substituted isoquinolines have been synthesized by two different pathways using either a Pictet–Grams or a Bischler–Napieralski approach. While the first synthesis afforded C1‐functionalizable 1,3‐dimethylisoquinoline derivatives, the second approach allowed the isolation of isoquinoline derivatives bearing a reactive ester function at the challenging C3 position. Among the large variety of efficient chemistry that can be independently or simultaneously performed at the C1 and C3 positions of the isoquinoline ring, 1,3‐dibromomethylisoquinoline derivatives have proven to be efficient intermediates for the synthesis of highly valuable ligands for lanthanide complexation.
Biphasic Voltammetry of N,N,N′,N′‐Tetraphenyl‐para‐phenylenediamine Microdroplets, Microparticles and Microparticle Suspensions
Authors: Halls Jonathan E. , Wadhawan Jay D. 
Published: March 2011

AbstractThe aqueous biphasic voltammetry of the title compound is examined when it is immobilised on an electrode surface either when dissolved in an array of nitrobenzene droplets, in the form of solid microparticles, or when an electrode is immersed into a three‐dimensional aqueous suspension of the solid. In each case, a different electrode reaction is observed to occur, even though the supporting electrolyte is unchanged, with either counter ion transfer across a liquid | liquid interface, or with electrochemical dissolution of the solid particles, or a suggested diffusive‐type electron hopping between individual redox centres embedded within the solid crystals.
Determination of Chemical Oxygen Demand Based on Novel Photoelectro‐bifunctional Electrodes
Authors: Qu Xiao , Tian Min , Chen Shuai , Liao Baoqiang , Chen Aicheng 
Published: March 2011

AbstractA novel photoelectro‐bifunctional electrode (TiO2/Ti/TiO2‐Pt) for the rapid determination of chemical oxygen demand (COD) has been developed. The TiO2 nanotubes, serving as the photocatalyst and the support of the electrocatalyst, were directly grown on both sides of a Ti plate by anodic oxidation. Pt nanoparticles were loaded on one side of TiO2 nanotubes by the photoreduction method. For the COD determination, the bifunctional electrode exhibits a low detection limit (9.5 mg/L), high sensitivity of 3.55×10−3 mA/(mg/L COD) and high Cl− tolerance (1400 mg/L). When used for the test of real wastewater samples, the results were in excellent agreement with those determined by the standard K2Cr2O7 method.
Effects of ionic strength, temperature and conformation on affinity interactions of β2‐glycoprotein I monitored by capillary electrophoresis
Authors: Bohlin Maria E. , Blomberg Lars G. , Heegaard Niels H. H. 
Published: March 2011

AbstractWe have used CE to evaluate the interaction between β2‐glycoprotein I (β2gpI) and heparin. β2gpI is a human plasma protein involved in the blood coagulation cascade. It is of interest to functionally characterize the interactions of β2gpI because the exact function is not entirely known and because circulating autoantibodies against β2gpI are associated with an increased risk of thrombotic events. The effect of the ionic strength, temperature, and conformation of the protein on the interaction between β2gpI and heparin has been studied. The CE procedure for this study is simple, fast, and automatic. β2gpI and heparin were allowed to interact during electrophoresis at different ionic strength buffers and at different capillary temperatures. To mimic perturbation of the conformation of β2gpI, different denaturing agents (SDS, ACN, and urea) were added to the BGE. While simple 1:1 binding isotherms were obtained at 22°C, the data strongly suggest that at physiological temperature the binding stoichiometry is not 1:1 and/or that cooperative interactions begin to play a role. We found that (i) theKD‐values differed by a factor of 60 at the ionic strengths studied (ii) β2gpI was resistant to denaturation with SDS and ACN, but was partially denatured by urea, and (iii) theKDfor the β2gpI–heparin interaction in the presence of urea was ten times higher than theKDdetermined at the same conditions without urea added. Therefore, we conclude that the interaction between β2gpI and heparin is dependent on electrostatic interactions and on the conformation of β2gpI.
Reduction of protein concentration range difference followed by multicolumn fractionation prior to 2‐DE and LC‐MS/MS profiling of serum proteins
Authors: Selvaraju Subhashini , El Rassi Ziad 
Published: March 2011

AbstractThis article is concerned with the reduction of protein concentration range differences by the peptide beads library technology (ProteoMiner™ or “equalizer” technology), which in principle allows the enrichment of proteins to the same concentration level (i.e. protein equalizer) regardless of the original protein abundance in a given biological fluid such as human serum, which is the subject of our investigation. After the equalization step, the captured proteins from human serum were fractionated on a series of tandem monolithic columns with surface‐bound iminodiacetic acid ligands to which three different metal ions, namely, Zn2+, Ni2+ and Cu2+ were immobilized to yield the so‐called immobilized metal affinity chromatography columns. These three monolithic columns were connected to a reversed‐phase column packed with polystyrene divinyl benzene beads. Aliquots taken from the four collected fractions from the four tandem columns were subsequently fractionated by 2‐DE. Also, aliquots from the four collected fractions were tryptically digested and analyzed by LC‐MS/MS. The strategy of subsequent fractionation on the four tandem columns after equalization allowed the identification of more proteins than simply using the equalization by ProteoMiner™. The equalizer technology was compared to the immuno‐subtraction approach. While the ProteoMiner™ technology is superior in terms of the overall number of captured proteins, it only complements the immuno‐subtraction approach since the latter can capture the proteins that were not captured by the former.