bluuebunny/crossref_metadata_2025 huggingface dataset:
Programmed antibodies as tailor‐made catalysts
Authors: Pandit Upendra K.
Published: September 2010

Antibodies raised against stable transition‐state analogues of specific reactions act as catalysts for the same reactions. Catalytic antibodies have been developed for a variety of reaction types. These include: hydrolysis of carbonates, esters, amides and phosphates, transacylation, cleavage of ethers and acetals, sigmatropic rearrangement, cis‐trans isomerization, 4 + 2 cycloaddition, β‐elimination, photochemical cycloaddition and photo‐induced cleavage and decarboxylation. Strategies have been evolved for constructing antibody active sites incorporating metal ions and organic cofactors. These extend the scope of designed antibody catalysts. The chiral nature of the antibody pocket induces enantioselectivity in the catalyzed reaction in several cases. The concept of antibody catalysis opens up the principal possibility of designing tailor‐made catalysts for any pre‐selected reaction.
Multinuclear‐magnetic‐resonance study of the coordination of aluminium (III)‐aldarate complexes with calcium(II) in aqueous solution
Authors: Venema F. R. , Peters J. A. , van Bekkum H.
Published: September 2010

The coordination of aluminium(III)‐aldarate complexes with calcium(II) in aqueous solution has been investigated with the use of 1H‐, 13C‐, 17O‐, and 27Al‐NMR spectroscopy. Xylarate and mannarate adopt, in the presence of AlIII and CaII, 1:2 AlIII‐ligand complexes with tetrahedrally coordinated AlIII. The AlIII‐xylarate complex binds one, whereas the mannarate complex binds two CaII ions. Arabinarate and glucarate give 2:2 AlIII‐ligand complexes with tetrahedrally coordinated AlIII, which bind one and two CaII ions, respectively. The CaII sites of all the complexes contain free carboxylate groups and, additionally, AlIII‐bonded (hydr)oxy or free α‐hydroxy groups.
Perception and generalization of protective groups in the COSYMA system
Authors: Hamm P. , Ellermann L. , Jauffret P. , Kaufmann G.
Published: September 2010

A new approach to computer‐assisted design of organic synthesis is proposed with the COSYMA system. This system was described in a previous paper. It is based on adaptation of a registered synthesis strategy to the structure of a new target molecule. An improvement to the COSYMA system founded on the perception of protection and deprotection reactions, is presented in this paper. The aim is to increase the performance of the system, to enable a clearer display with more complete results.
Reaction of C60 and C70 with ozone at different temperatures
Authors: Heymann Dieter , Chibante L. P. Felipe
Published: September 2010

The reactions of C60 and C70, dissolved in toluene, with ozone at 100, 23.5, 0. ‐ 16, and ‐ 78°C are reported. Both fullerenes are transformed swiftly at all of these temperatures. Both fullerenes form monoxides, dioxides and possibly higher oxides. The ratio of the rate parameters for the transformations of the two fullerenes change only slightly in the above temperature range. C60, however, is transformed about 40% faster than C70. The maximum yields of C60O, C60O2 and C70O increase at higher temperature.
Synthesis and exploratory photophysical investigation of donor‐bridge‐acceptor systems derived from N‐substituted 4‐piperidones
Authors: Scherer T. , Hielkema W. , Krijnen B. , Hermant R. M. , Eijckelhoff C. , Kerkhof F. , Ng A. K. F. , Verleg R. , van der Tol E. B. , Brouwer A. M. , Verhoeven J. W.
Published: September 2010

We report a two‐step synthesis for N‐aryl‐ and N‐alkyl‐substituted 4‐piperidones, in which the N substituent can easily be varied. A number of intramolecular donor‐acceptor systems was synthesized from these piperidones by conversion of the carbonyl functionality. The influence of the N‐aryl donor on the electronic absorption and fluorescence spectra was investigated systematically. It was concluded that some systems can be used as efficient fluorescent probes with a high sensitivity for solvent polarity.
Preparation of dyes derived from Eriochrome Red B and Acid Alizarin Violet N soluble in organic solvents
Authors: Katritzky Alan R. , Rachwal Bogumila , Rachwal Stanislaw , Smith Terrance P. , Macomber David W.
Published: September 2010

Both hydroxy groups of Eriochrome Red B are protected by acetylation and the sulfonic acid group is converted to the sulfonyl chloride with phosphorus pentachloride. Reaction with dibutylamine orN‐butylbenzeneethanamine followed by the deprotection gives red azo dyes7aor7b, readily soluble in chloroform and toluene. A similar procedure applied to Acid Alizarin Violet N gives only a multicomponent mixture. Friedel‐Crafts reaction between dibutylsulfamoyl chloride and 2‐nitrophenol givesN,N‐dibutyl‐4‐hydroxy‐3‐nitrobenzenesulfonamide (11). Reduction of the nitro group gives amine14which is diazotized and coupled with 2‐naphthol to give the required dye13giving deep‐red solutions in methanol, chloroform and acetone.
Electrophilic substitution of two monohomoperylenes and perylene
Authors: Cerfontain Hans , Koeberg‐Telder Ankie , Lerch Ulrike
Published: September 2010

Various types of electrophilic substitution of monohomoperylene(1)and its 11,11‐difluoro derivative(2)have been studied,viz. Bromination, nitration, acylation, formylation and sulfonation. Bromination withN‐bromosuccinimide (NBS) of1in dichloromethane leads to initial substitution mainly at the α positions 2 and 10,i.e., of the annuleno moiety, followed by further substitution of the β positions 4 and 8 of the same moiety, and of the α positions 2′ and 10′ of the naphthaleno moiety. Reaction of1with 5.0 mol‐equiv. of NBS yields 2,4,8,10,2′‐pentabromo‐1in 46% yield.

Sulfonation of1with SO3in dichloromethane using 1.2 mol‐equiv. of dioxane as reactivity moderator leads to the formation of1‐2‐sulfonic acid (1‐2‐S),1‐2,10‐S2, and the intermediate σ complex6. Sulfonation of the 11,11‐difluoro derivative2leads to the formation of2‐2‐S,2‐2,10‐S2and 2‐2,10‐disulfonic anhydride(7), together with small amounts of2‐2,2′‐S2or/and2‐2,10′‐S2. The other types of electrophilic substitution of1and2studied were found to proceed similarly, in that the initial substitution occurs at the 2‐position and the subsequent one at the 10‐position,i.e., perito the primarily introduced substituent.

The chemical behaviour (i.e., the substitution pattern and relative reactivity) of the two monohomoperylenes1and2have been compared with that of 1,6‐methano[10]annulene(3), its 11,11‐difluoro derivative(4), and perylene (5). For example, the sulfonation reactivity ratio of the naphthalene to the [10]annuleno moiety is significantly greater for2than1, as predicted on the basis of the higher sulfonation reactivity of3compared to4.
Total synthesis of (+)‐13‐ethyl‐3‐methoxygona‐1,3,5,9(11)‐tetraen‐17‐one via the tandem Claisen‐ene strategy
Authors: Groen‐Piotrowska E. M. , Groen M. B.
Published: September 2010

A total synthesis of the title compound 2, a potential precursor of the progestagens desogestrel and 3‐ketodesogestrel, is described. The backbone of the steroid was assembled by condensation of 1,2‐dihydro‐4,7‐dimethoxynaphthalene (12) and [S‐(Z)]‐8,9‐dihydroxy‐7‐ethyl‐6‐nonen‐2‐ynoic acid methyl ester 9‐(tert‐butyldimethyl)silyl ether (11), prepared from [R‐(+ )]‐glyceraldehyde acetonide (4), and subsequent Claisen rearrangement. Heating of the resulting disecosteroid (14) at 170°C gave a 1:1 mixture of 9,11‐secosteroids, 15 and 16, having the 8α, 13β, 14α‐ and 8α, 13α, 14α‐configuration, respectively. The 13β‐epimer 15 was converted into 11‐bromo‐13‐ethyl‐3‐methoxy‐9,11‐secogona‐1,3,5(10)‐triene‐9,17‐dione (21), which reacted with triphenylphosphine under high pressure conditions (12 kbar, 55°C) to give the corresponding phosphonium salt 22. The intramolecular Wittig reaction of 22 proceeded with epimerization at C‐8 to give exclusively (8α)‐13‐ethyl‐3‐methoxygona‐1,3,5,9(11)‐tetraen‐17‐one (23) which, upon treatment with acid, isomerized to the title compound 2.
Synthesis of concave receptors derived from diphenylglycoluril
Authors: Sijbesma R. P. , Nolte R. J. M.
Published: September 2010

Improved synthetic methods are described for the synthesis of concave receptor molecules. These receptors consist of a diphenylglycoluril unit, flanked by two aromatic moieties. The most versatile synthetic method consists of Lewis‐acid‐catalyzed reaction of a tetrakis(chloromethyl) derivative of diphenylglycoluril with the appropriate benzene or naphthalene derivative.
Case histories of peptidomimetics: Progression from peptides to drugs
Authors: Adang Anton E. P. , Hermkens Pedro H. H. , Linders Joannes T. M. , Ottenheijm Harry C. J. , van Staveren Catherina J.
Published: September 2010

There is a growing number of biologically active peptides which have potential for the development of new therapeutics. However, native peptides are only rarely directly usable as drugs, due to inherent limitations which include rapid proteolysis and metabolism, poor transport properties, rapid excretion by the liver and kidneys, and low oral activity. Furthermore, peptides are often aselective in their actions owing to their flexible structure. In efforts to address these limitations, peptides are modified into mimetics with specific physical, chemical and biological characteristics. These so‐called peptidomimetics are derived from peptides by partly or completely removing the amide bonds while retaining essential amino acid side chains in a defined, spatial relationship. They can be developed in a rational design cycle which starts either from a lead compound obtained in a screening programme or from the parent peptide. In the latter approach, which is the focus of this overview, first the smallest, active sequence is found, and the significance of each amino acid for the biological activity is determined. In the following steps the bioactive conformation is defined by the introduction of local and global constraints. In the final step the essential amino acid side chains are positioned onto a scaffold, preferably a small, polyfunctional ring of defined stereochemistry, using structural information obtained in earlier steps. Five examples of the application of the peptidomimetic design cycle in medicinal chemistry are described here, illustrating the progression from native peptides to therapeutically useful drugs.
Aggregation behaviour and copper‐binding properties of surfactants containing imidazole and pyrazole ligands
Authors: van Esch J.H. , Damen M. , Feiters M.C. , Nolte R.J.M.
Published: September 2010

The synthesis and aggregation behaviour of simple dialkylamine‐imidazole and dialkylamine‐pyrazole surfactants is described. In the presence of one equivalent of HCl the imidazole surfactants form stable vesicular dispersions. Addition of copper(II) dichloride to these dispersions leads to formation of metallo‐vesicles in which four imidazole groups are coordinated to one copper(II) ion. These metallo‐vesicles are unstable and are slowly converted into stacked bilayers, which precipitate. The pyrazole surfactants on the other hand do not form vesicles but give, with one molar equivalent of HCl, water‐insoluble stacked bilayers. The pyrazole moieties in these stacked bilayers do not coordinate copper(II) ions. This behaviour is most probably due to the formation of an intramolecular hydrogen bond in the mono‐protonated pyrazole surfactant molecule. The imidazole surfactants cannot form such a hydrogen bond.
Surface monolayers and aqueous bilayers of single‐chain ammonium amphiphiles which contain benzylideneaniline and salicylideneaniline units
Authors: Nishimi Taisei , Ishikawa Yuichi , Ando Reiko , Kunitake Toyoki
Published: September 2010

The assembling properties of single‐chain ammonium amphiphiles containing benzylideneaniline and salicylideneaniline units as rigid segments in the formation of aqueous bilayers, cast multi‐bilayers, and surface monolayers were studied. Electron microscopy indicated that aggregate morphologies observed in water, such as vesicles and fibers, were dependent on the nature of the aromatic unit and the alkyl‐chain length of the component amphiphiles. The patterns of molecular assembly in bilayers were examined by absorption spectroscopy of aqueous bilayers and X‐ray diffraction of cast multi‐bilayer films. The patterns were virtually identical to those of the corresponding azobenzene bilayers, and commonly determined by combinations of alkyl‐chain lengths. This alkyl‐chain combination was crucial for formation of stable surface monolayers.
Synthesis and photochemistry of (2S,4R)‐ and (2S,4R)‐1,2,3,4‐tetrahydro‐4‐ethyl‐1,1,4‐trimethyl‐3Z‐ethylidene‐2‐naphthalenols
Authors: Miesen F. W. A. M. , van Dongen J. L. J. , Meijer E. W.
Published: September 2010

The synthesis and photochemistry of optically pure (2S,4R)‐ and (2R,4R)‐1,2,3,4‐tetrahydro‐4‐ethyl‐1,1,4‐trimethyl‐3Z‐ethylidene‐2‐naphthalenols 10a and 11a are described. Naphthalenols 10a and 11a were prepared in seven steps from 2‐phenylbutanenitrile. Synthesis is mainly based upon acylation of isobutene by the optically active 2‐methyl‐2‐phenylbutanoyl chloride (5), and a Wittig reaction, while the ethylidene naphthalenones 8a and 9a are separated by HPLC. Under inert conditions, irradiation of both alcohols gives rise to E‐Z isomerization, followed by photodegradation reactions, leading to the formation of indane 12 by the elimination of formaldehyde. Irradiation of oxygenated solutions of 10a reveals a rapid photoaddition of oxygen to the double bond, leading to the stereo‐ and regioselective formation of hydroperoxide 13 and epoxy alcohol 15a, which hydrolyses on standing to triol 16a. The observed stereochemistry is explained by the stereoselective coordination of the hydroxyl group at the chiral allylic site with the attacking electrophilic oxygen. In the case of 11a a more complicated reaction mixture was obtained in which, analogously, the epoxy alcohol 15b and triol 16b were present. Semi‐empirical MNDO, AM1 and PM3 calculations revealed that, in the preferential ground state conformation, the hydroxyl group occupies an orthogonal position with respect to the exocyclic double bond. Fluorescence measurements revealed that the reactive state in the photochemistry of these naphthalenol systems under inert conditions is the triplet state. In the photoreactions of optically pure compounds 10a and 11a, we were unable to identify products analogous to 2, which are claimed to originate from the racemic precursors 1 via a planar 1,3 OH shift from a singlet (in the double bond) excited state. Clean photochemical reactions were observed only when 10a and 11a were irradiated in oxygenated solutions, resulting in stereo‐ and regiospecific photoproducts.
The fabrication of “high‐technology” catalysts
Authors: Ribeiro F.H. , Somorjai G.A.
Published: September 2010

To produce reaction products with 100% chemical selectivity, and to attain much higher turnover rates and number of turnovers, the development of new methods of catalyst preparation are necessary. Precise control of particle size, the separation between catalyst particles and their superior chemical and thermal stability must be achieved. To this end, five new methods of preparation of high‐technology catalysts are being studied. These are: (A) the method successfully used by W.M.H. Sachtler for metal particle deposition in zeolite cages, (B) the deposition of metal particles by atomic layer epitaxy, (C) controlled nucleation and growth of metal particles by substrate spinning, (D) deposition of metals on oxides by evaporation, (E) preparation of ordered metal arrays by electron‐beam lithography using microelectronic techniques. These different methods are described and discussed, and their present states of development are assessed.
Fano coupling in perturbed solid acid hydroxyls
Authors: van Santen R.A.
Published: September 2010

A simple analytical expression for the Evans window in the infrared absorption spectrum of hydrogen‐bonded basic molecules in protonic zeolites is presented. The expression shows that the essential parameters are the position of the shifted “uncoupled” OH stretching frequency, its width, the position of the in‐plane bending overtone and the coupling of this mode with the OH stretching mode. Analysis of the Fermi resonances in the OH stretching band profile provides a method to determine whether adsorbed molecules are hydrogen bonded or protonated.
Molecular events on metal surfaces. FEM and FIM studies of metals and supported catalysts
Authors: Knor Z.
Published: September 2010

The application of field‐emission microscopy (FEM) and field‐ion microscopy (FIM) to surface studies related to catalysis (symmetry of atomic‐like states localized at the surface atoms of transition metals, spillover effect, dissipation of energy, etc.) is discussed together with a new approach to modeling of supported bimetallic catalysts in these devices.
Surface processes in the catalytic oxidative coupling of methane to ethane
Authors: Buyevskaya Olga , Wolf Dorit , Baerns Manfred
Published: September 2010

Recent results on surface reaction steps in the oxidative coupling of methane (OCM) obtained from (1) transient experiments and (2) a microkinetic analysis are summarized. The interaction of methane and oxygen with MgO and Sm2O3 surfaces was investigated by applying H/D‐ and oxygen‐isotope‐exchange reactions. The role of short‐lived adsorbed oxygen species in methane activation and product formation over MgO and Sm2O3 catalysts is discussed. Furthermore, elementary reaction steps and their rate constants are derived for the oxidative conversion of methane to COx and ethane from kinetic data for different (CaO)x(CeO2)1−x catalysts; the rate constants are related to the solid's properties, i.e., electron and O2− conductivity.
Influence of chlorine and metal cation impurities in the CO hydrogenation over Pd/SiO2 and Rh/SiO2
Authors: Gloor A.P. , Prins R.
Published: September 2010

Catalysts were prepared from ultra pure SiO2, Pd and Rh nitrates and chlorides, and by doping with Al, Fe, Na, K or Ca nitrate. The activities and selectivities of the Pd and Rh catalysts were investigated in CO hydrogenation at 553K, H2/CO = 2 or 3, and 2.5 or 4 MPa, respectively. Both the additives and the noble‐metal anions had a strong influence on the catalytic properties, even when no anions were present after catalyst preparation. These influences are due to dissolution of the metal additives by the aqueous noble‐metal salt solution during catalyst preparation, so that after reduction the additives end up in the vicinity of the metal particles. Chloride solutions extract the additives better from the catalyst support surface than nitrate solutions and therefore have a stronger influence on the catalytic properties, especially of SiO2‐supported catalysts.
The chelate effect in binding, catalysis, and chemotherapy
Authors: Breslow Ronald
Published: September 2010

Jacobus Henricus van't Hoff was in many senses the father of modern chemistry. It is a great honor to be invited to give this eighth van't Hoff lecture, and a great pleasure to visit the Netherlands again. Among his other contributions, van't Hoff made us aware of the importance of the three‐dimensional structure of chemical substances. In 1874 he was the first to explain optical isomerism and geometrical isomerism in organic chemistry, ruffling the feathers of older established chemists such as Kolbe.

In this lecture, I will describe three studies in somewhat diverse areas ‐ binding, catalysis, and cancer chemotherapy ‐ that are related in the sense that they all involve the cooperative action of two groups of a molecule acting on a substrate. As will become clear, the three‐dimensional arrangement of these groups (“La chimie dans l'espace”) is a critical aspect of their effective cooperation.
Endohedral fullerene research
Authors: Holleman Iwan , Boogaarts Maarten G. H. , Meijer Gerard
Published: September 2010

Research on endohedral fullerenes has yielded unambiguous evidence for the existence of selected inside‐the‐cage complexes. Milligram quantities of purified samples of metallofullerenes have been produced, and characterized via techniques that selectively probe the endohedral guest. Experiments aimed at a detailed understanding of the molecular properties of the endohedral complexes as well as of the material properties of compounds containing endohedral fullerenes have just started.
Role of the stereochemistry of 3′‐fluoro‐3′‐deoxy analogues of 2‐5A in binding to and activation of mouse RNase L
Authors: Kalinichenko Elena N. , Podkopaeva Tatjana L. , Poopeiko Nicolai E. , Kelve Merike , Saarma Mart , Mikhailopulo Igor A. , van den Boogaart Jacquelien E. , Altona Cornelis
Published: September 2010

The synthesis of two sets of analogues of 2‐5A trimer containing 9‐(3‐fluoro‐3‐deoxy‐β‐D‐xylo‐furanosyl)adenine (AF) or 3′‐fluoro‐3′‐deoxyadenosine (AF) at different positions of the chain is described, along with the preparation of the corresponding 5′‐monophosphates and 5′‐diphosphorylated (core) trimers. The ability of each ribo and xylo isomeric pair of fluorodeoxy analogues of 2‐5A (i) to compete with p3(A2′p)3A3′[32P]pC3′p for binding to RNase L in L929 cell extracts, and (ii) to activate the partially purified RNase L from L929 cell extracts to hydrolyze poly(U)[3H], was compared to that of the related 3′‐deoxy analogue [Torrence et al., J. Biol. Chem. 263, 1131 (1988)] and the parent trimer, p3A3, using radiobinding and RNase L‐(2′,5′)pentaadenylate(core)‐agarose assays, respectively. Evidence is presented to show that the stereochemistry of the trimers plays an important role, specifically in the second process. The most striking observation is that, compared to 2‐5A, p3A(AF)A was found to be nine times more effective an activator of RNase L, whereas isomeric p3A(AF)A is 30 times less effective.
An abasic site induces a bulged conformation in the single‐stranded DNA trimer d(Ap(ab)pA). An NMR and model‐building study
Authors: van den Boogaart Jacquelien E. , Huige Cornelis J. M. , Boal Jila H. , Egan William , Altona Cornelis
Published: September 2010

1′,2′‐Dideoxy‐D‐ribofuranose (ab), its 5′‐ and 3′‐phosphorylated analogues (ab5 and ab3), and the DNA trimer d(Ap(ab)pA) have been studied by means of proton NMR spectroscopy. These fragments are of interest as model compounds for abasic lesions occurring in vivo. All abasic sugars exhibit similar S‐type sugar conformations with populations of S‐conformer varying from 75% (in ab and ab5) to 83% (in ab3 and dab(2)), Ps ≈ 144° and Φs in the range from 30 to 33°. Having established the presence of mainly S‐type sugar, we could assign the H1′ and H1″ protons of all abasic residues stereospecifically on the basis of their respective vicinal coupling constants. The trimer exhibits considerable flexibility in the backbone. Moreover, chemical shifts as a function of temperature and chemical‐shift differences between abasic sugar protons in the trimer and in the abasic monomers point to the presence of a structure in which dab(2) is bulged out of the helix and the terminal residues stack on top of each other. Several models which fit the experimental data are presented.
Thionyl‐chloride‐pyridine‐mediated rearrangement of tertiary alcohols
Authors: Banerjee Ajoy K. , Vera William
Published: September 2010

Tertiary alcohols 5 and 8 undergo rearrangement on treatment with thionyl chloride and pyridine, yielding octahydronaphthalenes 6 and 9, respectively. Alcohol 12 under similar treatment affords a mixture of tetrahydronaphthalene 14 and diene 15, whereas alcohol 22 suffers no rearrangement but produces olefin 23.
Circular‐dichroism power of chiral, bridged, aromatic compounds. 7,8,15,16‐Tetrahydro‐7,15‐methanocycloocta[1,2‐a:5,6‐a′]dinaphthalene derivatives
Authors: Harada Nobuyuki , Hiyoshi Norie , Naemura Koichiro
Published: September 2010

The circular dichroism (CD) and UV spectra of chiral bridged aromatic compounds, 7,8,15,16−tetrahydro‐7,15‐methanocycloocta[1,2‐a:5,6‐a′]dinaphthalene‐8,16 ‐diol [(‐)‐1] and −8,16‐ dione [(‐)‐2], have been theoretically calculated by application of the π‐electron self‐consistent‐ field‐configuration‐interaction‐dipole‐velocity molecular orbital (SCF‐CI‐DV MO) method. The shape of component CD and UV bands was approximated by the Gaussian distribution method (A), or by employing the observed band shape of the UV spectra of model compounds (method B). The calculated CD and UV curves were in good agreement with the observed ones. For compound (7S,8R,15S,16R)‐(‐)‐1, method A: calcd. CD, λext 237.0 nm (Δϵ −319.2), 224.2 (+ 344.9), A = −664.1; obsd. CD, λext 233.0 nm (Δϵ −671.0), 222.3 (+ 194.6), A = −865.6. The calculated CD and UV spectral curves of compound 1 obtained by the application of method B were in excellent agreement with the observed ones: calcd. CD, λext 233.6 nm (Δϵ −740.8), 222.2 (+ 265.0), A = −1005.8; obsd. CD, λext 233.0 nm (Δϵ −671.0), 222.3 (+ 194.6), A = −865.6. For compound (7S,15S)‐(‐)‐2, method A: calcd. CD, λext 256.4 nm (Δϵ −69.4), 220.3 (+ 103.5); obsd. CD, λext 254.4 nm (Δϵ −89.0), 217.0 (+ 222.1). The absolute configurations of chiral, bridged aromatics (‐)‐1 and (‐)‐2 have thus been established.
Enzymatic ammoniolysis of amino acid derivatives
Authors: de Zoete M. C. , Ouwehand A. A. , van Rantwijk F. , Sheldon R. A.
Published: September 2010

The ammoniolysis of amino acid esters and their derivatives was performed with lipases and proteases yielding the corresponding amino acid amides with moderate to high enantioselectivity. Phenylglycine methyl ester racemized slowly under the reaction conditions.
Is there a preferred expression for the composition of a mixture of enantiomers?
Authors: Kagan Henri B.
Published: September 2010

The advantages and disadvantages of using enantiomeric excess, enantiomeric composition or enantiomer ratio to describe a mixture of enantiomers, are discussed with respect to various stereochemical situations.
The enantiomeric excess determination and dynamic behaviour of cyclic phosphoric acids used for resolution
Authors: Hulst Ron , Kruizinga Wim , Wynberg Hans , Feringa Ben L. , Kellogg Richard M.
Published: September 2010

A method is presented to determine the enantiomeric excess (ee) of phosphoric acids 1, which are extensively used as resolving agents, by means of diastereomeric salt formation with chiral amines. The unexpected dynamic behaviour of these systems leads us to postulate a model, which we refer to as non‐reciprocal behaviour.
Induced chirality of guest molecules encapsulated into a dendritic box
Authors: Jansen Johan F. G. A. , de Brabander‐van den Berg Ellen M. M. , Meijer E. W.
Published: September 2010

The internal cavities of a dendritic box, constructed from poly(propylene imine) dendrimers and enantiomerically pure N‐tBOC‐L‐phenylalanine hydroxysuccinimide esters, possess distinct chiral properties as was demonstrated with the observation of induced optical activity of a variety of guests encapsulated in the box. This induced optical activity of guests is measured with CD (circular dichroism) spectroscopy and is remarkable as the optical activity of the amino acid outer shell itself is vanishingly small. Although small, the effects observed are significant in many cases, whilst in other cases the guests encapsulated do not show an induced CD. Indications for an enforced close proximity and some kind of ordering of guests is found by the observation of an exciton‐coupled CD spectrum in the case of four Bengal Rose molecules encapsulated in a single dendritic box. It is shown that the effects are dependent on the solvent used and the history of the sample. Therefore, the observation of induced optical activity can be used to study the mode of encapsulation of the guests into the box.
The synthesis of pure Amadori rearrangement products
Authors: Noomen S. N. , Breel G. J. , Winkel C.
Published: September 2010

The term “Maillard reaction” is used to describe a complex set of reactions in foods leading to flavour generation and non‐enzymatic browning. The first step in this process is the so‐called Amadori rearrangement: a reducing saccharide and a peptide fragment react to form an Amadori Rearrangement Product (ARP). To be able to do model studies on flavour generation, gram amounts of pure ARP are required. In the present study, glucose‐derived ARPs were synthesised from specifically protected and activated starting compounds. After deprotection and purification, pure ARPs were obtained. This is the first time that ARPs of dipeptides have been isolated.
Synthesis and aggregation behavior of 2‐(4‐butyloctyl) malonic acid in aqueous solution. The formation of physically and colloidally stable vesicles by a branched‐chain malonate
Authors: de Groot Rimke W. , Wagenaar Anno , Sein Arjen , Engberts Jan B. F. N.
Published: September 2010

A new surfactant with a branched monoalkyl chain and a malonate headgroup has been synthesized: 2‐(4‐butyloctyl)malonic acid (BOMA). From the geometry of the surfactant, reflected in a packing parameter (P), it was anticipated that the surfactant would preferably aggregate in bilayers. This expectation was borne out in practice by the aggregation behavior, as studied by transmission electron microscopy (TEM) with negatively stained samples and freeze‐fracture samples of aqueous vesicle dispersions. The structure of the surfactant headgroup has been varied by changes in pH of the vesicle dispersions. Over a wide pH range (pH 2.8‐12.8) small unilamellar vesicles with a size of 20–50 nm were observed. Multilamellar vesicles were observed as well in the pH range 2.8–5.1. Phase‐penetration experiments using an optical polarization microscope showed the birth and growth of myelins and multilamellar vesicles over a pH range 1.5‐13.1. At pH < 2.8, a phase separation occured into a surfactant‐rich, optically isotropic phase and a surfactant‐lean phase. The physical and colloidal stability of the vesicular aggregates is high: up to one year as confirmed by TEM. The fusogenic properties of BOMA vesicles were examined. Upon the addition of Ca2+ ions, aggregates tended to become larger, but the formation of Ca2+ surfactant crystals was also observed.
A look at the value creation effects of patenting and capital investment through a real options lens: the moderating role of uncertainty
Authors: Levitas Edward , Chi Tailan
Published: September 2010

This article applies a real options approach to analyzing the impact of a firm's investment in appropriable technology (as represented by the intensity of its patenting activities and capital investment) on the firm's opportunities to create value through future investment (as represented by Tobin's q). Recognizing the mixed results with regard to the relationship between patenting and firm value, we argue that such investment may primarily create value by offering future technology options and that the relationship may be more appropriately modeled on the basis of real options theory. We argue that patenting creates and replenishes a firm's technology options whereas capital investment entails the exercise of such options. Three hypotheses are derived from a valuation model based on the real options approach and tested using a fixed‐effects panel data procedure. The results of our empirical analysis using a sample of 161 U.S.‐based biotechnology firms are consistent with our predictions. Copyright © 2010 Strategic Management Society.
Bias and efficiency of multiple imputation compared with complete‐case analysis for missing covariate values
Authors: White Ian R. , Carlin John B.
Published: September 2010

When missing data occur in one or more covariates in a regression model, multiple imputation (MI) is widely advocated as an improvement over complete‐case analysis (CC). We use theoretical arguments and simulation studies to compare these methods with MI implemented under a missing at random assumption.

When data are missing completely at random, both methods have negligible bias, and MI is more efficient than CC across a wide range of scenarios. For other missing data mechanisms, bias arises in one or both methods. In our simulation setting, CC is biased towards the null when data are missing at random. However, when missingness is independent of the outcome given the covariates, CC has negligible bias and MI is biased away from the null. With more general missing data mechanisms, bias tends to be smaller for MI than for CC.

Since MI is not always better than CC for missing covariate problems, the choice of method should take into account what is known about the missing data mechanism in a particular substantive application. Importantly, the choice of method should not be based on comparison of standard errors. We propose new ways to understand empirical differences between MI and CC, which may provide insights into the appropriateness of the assumptions underlying each method, and we propose a new index for assessing the likely gain in precision from MI: the fraction of incomplete cases among the observed values of a covariate (FICO). Copyright © 2010 John Wiley & Sons, Ltd.
Bayesian approach to cancer‐trend analysis using age‐stratified Poisson regression models
Authors: Ghosh Pulak , Ghosh Kaushik , Tiwari Ram C.
Published: September 2010

Annual Percentage Change (APC) summarizes trends in age‐adjusted cancer rates over short time‐intervals. This measure implicitly assumes linearity of the log‐rates over the intervals in question, which may not be valid, especially for relatively longer time‐intervals. An alternative is the Average Annual Percentage Change (AAPC), which computes a weighted average of APC values over intervals where log‐rates are piece‐wise linear.

In this article, we propose a Bayesian approach to calculating APC and AAPC values from age‐adjusted cancer rate data. The procedure involves modeling the corresponding counts using age‐specific Poisson regression models with a log‐link function that contains unknown joinpoints. The slope‐changes at the joinpoints are assumed to have a mixture distribution with point mass at zero and the joinpoints are assumed to be uniformly distributed subject to order‐restrictions. Additionally, the age‐specific intercept parameters are modeled nonparametrically using a Dirichlet process prior. The proposed method can be used to construct Bayesian credible intervals for AAPC using age‐adjusted mortality rates. This provides a significant improvement over the currently available frequentist method, where variance calculations are done conditional on the joinpoint locations.

Simulation studies are used to demonstrate the success of the method in capturing trend‐changes. Finally, the proposed method is illustrated using data on prostate cancer incidence. Copyright © 2010 John Wiley & Sons, Ltd.
Viral Coat Proteins as Flexible Nano‐Building‐Blocks for Nanoparticle Encapsulation
Authors: Li Feng , Li Ke , Cui Zong‐Qiang , Zhang Zhi‐Ping , Wei Hong‐Ping , Gao Ding , Deng Jiao‐Yu , Zhang Xian‐En
Published: September 2010

Viral capsid–nanoparticle hybrid structures offer new opportunities for nanobiotechnology. We previously generated virus‐based nanoparticles (VNPs) of simian virus 40 (SV40) containing quantum dots (QDs) for cellular imaging. However, as an interesting issue of nano‐bio interfaces, the mechanism of nanoparticle (NP) encapsulation by viral coat proteins remains unclear. Here, four kinds of QDs with the same core/shell but different surface coatings are tested for encapsulation. All the QDs can be encapsulated efficiently and there is no correlation between the encapsulation efficiency and the surface charge of the QDs. All the SV40 VNPs encapsulating differently modified QDs show similar structures, fluorescence properties, and activity in entering living cells. These results demonstrate the flexibility of SV40 major capsid protein VP1 in NP encapsulation and provide new clues to the mechanism of NP packaging by viral shells.
Cartesian theories on the passions, the pineal gland and the pathogenesis of affective disorders: an early forerunner
Authors: López-Muñoz F. , Alamo C.
Published: September 2010

The relationship between physical and functional alterations in the pineal gland, the ‘passions’ (emotions or feelings) and psychopathology has been a constant throughout the history of medicine. One of the most influential authors on this subject was René Descartes, who discussed it in his workThe Treatise on the Passions of the Soul(1649). Descartes believed that ‘passions’ were sensitive movements that the soul, located in the pineal gland, experienced due to its union with the body, by circulating animal spirits. Descartes described sadness as one of the six primitive passions of the soul, which leads to melancholy if not remedied. Cartesian theories had a great deal of influence on the way that mental pathologies were considered throughout the entire 17th century and during much of the 18th century, but the link between the pineal gland and psychiatric disorders it was definitively highlighted in the 20th century, with the discovery of melatonin in 1958. The recent development of a new pharmacological agent acting through melatonergic receptors (agomelatine) has confirmed the close link between the pineal gland and affective disorders.
Economic downturns and population mental health: research findings, gaps, challenges and priorities
Authors: Zivin K. , Paczkowski M. , Galea S.
Published: September 2010

Prior research suggests that the current global economic crisis may be negatively affecting population mental health. In that context, this paper has several goals: (1) to discuss theoretical and conceptual explanations for how and why economic downturns might negatively affect population mental health; (2) present an overview of the literature on the relationship between economic recessions and population mental health; (3) discuss the limitations of existing empirical work; and (4) highlight opportunities for improvements in both research and practice designed to mitigate any negative impact of economic declines on the mental health of populations. Research has consistently demonstrated that economic crises are negatively associated with population mental health. How economic downturns influence mental health should be considered in policies such as social protection programs that aim to promote recovery.
Associations between diurnal preference, sleep quality and externalizing behaviours: a behavioural genetic analysis
Authors: Barclay N. L. , Eley T. C. , Maughan B. , Rowe R. , Gregory A. M.
Published: September 2010

Background

Certain aspects of sleep co-occur with externalizing behaviours in youth, yet little is known about these associations in adults. The present study: (1) examines the associations between diurnal preference (morningness versus eveningness), sleep quality and externalizing behaviours; (2) explores the extent to which genetic and environmental influences are shared between or are unique to these phenotypes; (3) examines the extent to which genetic and environmental influences account for these associations.

Method

Questionnaires assessing diurnal preference, sleep quality and externalizing behaviours were completed by 1556 young adult twins and siblings.

Results

A preference for eveningness and poor sleep quality were associated with greater externalizing symptoms [r=0.28 (95% CI 0.23–0.33) and 0.34 (95% CI 0.28–0.39), respectively]. A total of 18% of the genetic influences on externalizing behaviours were shared with diurnal preference and sleep quality and an additional 14% were shared with sleep quality alone. Non-shared environmental influences common to the phenotypes were small (2%). The association between diurnal preference and externalizing behaviours was mostly explained by genetic influences [additive genetic influence (A)=80% (95% CI 0.56–1.01)], as was the association between sleep quality and externalizing behaviours [A=81% (95% CI 0.62–0.99)]. Non-shared environmental (E) influences accounted for the remaining variance for both associations [E=20% (95% CI −0.01 to 0.44) and 19% (95% CI 0.01–0.38), respectively].

Conclusions

A preference for eveningness and poor sleep quality are moderately associated with externalizing behaviours in young adults. There is a moderate amount of shared genetic influences between the phenotypes and genetic influences account for a large proportion of the association between sleep and externalizing behaviours. Further research could focus on identifying specific genetic polymorphisms common to both sleep and externalizing behaviours.
Deep crustal structure beneath large igneous provinces and the petrologic evolution of flood basalts
Authors: Ridley Victoria A. , Richards Mark A.
Published: September 2010

We present a review of seismological constraints on deep crustal structures underlying large igneous provinces (LIPs), largely from wide‐angle seismic refraction surveys. The main purpose of this review is to ascertain whether this seismic evidence is consistent with, or contrary to, petrological models for the genesis of flood basalt lavas. Where high‐quality data are available beneath continental flood basalt (CFB) provinces (Emeishan, Columbia River, Deccan, Siberia), high‐velocity structures (Vp ∼ 6.9–7.5 km/sec) are typically found immediately overlying the Moho in layers of order ∼5–15 km thick. Oceanic plateau (OP) LIPs exhibit similar layers, with a conspicuous layer of very high crustal velocity (Vp ∼ 7.7 km/sec) beneath the enormous Ontong‐Java plateau. These structures are similar to inferred ultramafic underplating structures seen beneath active hot spots such as Hawaii, the Marquesas, and La Reunion. Petrogenetic models for flood basalt volcanism based on hot plume melting beneath mature lithosphere suggest that these deep seismic structures may consist in large part of cumulate bodies of olivine and clinopyroxene which result from ponding and deep‐crustal fractionation of ultramafic primary melts. Such fractionation is necessary to produce basalts with typical MgO contents of ∼6–8%, as observed for the vast bulk of observed flood basalts, from primary melts with MgO contents of order ∼15–18% (or greater) such as result from hot, deep melting beneath the lithosphere. The volumes of cumulate bodies and ultramafic intrusions in the lowermost crust, often described in the literature as “underplating,” are comparable to those of the overlying basaltic formations, also consistent with petrological models. Further definition of the deep seismic structure beneath such prominent LIPs as the Ontong‐Java Plateau could place better constraints on flood basalt petrogenesis by determining the relative volumes of ultramafic bodies and basaltic lavas, thereby better constraining the overall process of LIP emplacement.
Development of a combined CloudSat‐CALIPSO cloud mask to show global cloud distribution
Authors: Hagihara Yuichiro , Okamoto Hajime , Yoshida Ryo
Published: September 2010

We developed a cloud mask scheme that combines measurements from CloudSat and Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellites. First, we developed a cloud mask scheme for CALIPSO using a threshold of the attenuated total backscattering coefficient and a spatial continuity test. We then developed a combined CloudSat‐CALIPSO cloud mask. These cloud masks were applied to 3 months of data from September to November 2006, and the vertical distributions of zonal mean cloud fractions and cloud coverage were analyzed. We also examined the standard vertical feature mask (VFM) cloud scheme. The VFM occasionally made false detections because of its horizontal averaging procedure and seemed to misclassify noise or aerosols as clouds. In addition, the VFM appeared to significantly overestimate low‐level clouds. Below 2 km, the cloud fraction differed by as much as 25% between the VFM and our combined scheme. We also compared the zonal mean cloud coverage for the topmost layer detected by the sensors using our CALIPSO scheme, the VFM, our combined CloudSat‐CALIPSO scheme, and the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) results. For low‐level clouds (>680 hPa), the MODIS result was larger than that of our CloudSat‐CALIPSO scheme, and results from the VFM and our CALIPSO scheme differed by as much as 15%. The CALIPSO, CloudSat‐CALIPSO, and MODIS results were similar for total cloud coverage, but the VFM result was different. Because of possible misclassification at low levels, the VFM showed the largest cloud coverage in middle and low latitudes.
Observed aerosol and liquid water path relationships in marine stratocumulus
Authors: Zheng Xue , Albrecht Bruce , Minnis Patrick , Ayers Kirk , Jonson Haflidi H.
Published: September 2010

The stratocumulus‐topped marine boundary layer (BL), aerosol, and cloud properties observed on research flights made off the coast of northern Chile in the Southeastern Pacific (20°S, 72°W) during the VAMOS Ocean‐Cloud‐Atmosphere‐Land Study‐Regional Experiment (VOCALS‐REx) were used to examine the variation of liquid water path (LWP) and cloud condensation nuclei (CCN). Ten flights were made under similar meteorological conditions where the BL structure was well‐mixed, clouds were solid, and the conditions at the surface and at the top of the BL were similar. A strong positive correlation between the LWP, which varied from 15 to 73 gm−2, and the BL CCN, which ranged from 190 to 565 cm−3, was observed. Analysis of the highest and the lowest CCN concentration cases confirms that the differences in the thermodynamic jumps at the top of the BL and the turbulent fluxes at the surface cannot explain the observed differences in the LWP. Cloud properties from satellite retrievals combined with a back trajectories analysis demonstrated that the LWP differences observed at the time of the aircraft flights are also prevalent during the night‐time hours prior to the aircraft observations. These results provide evidence for CCN and LWP relationships that are not fully explained by current hypotheses from numerical modeling.
Varying interplanetary magnetic field By effects on interhemispheric conjugate auroral features during a weak substorm
Authors: Motoba T. , Hosokawa K. , Sato N. , Kadokura A. , Bjornsson G.
Published: September 2010

Interhemispheric conjugate auroral features during a weak substorm interval were investigated using simultaneous all‐sky camera (ASC) measurements at the northern and southern geomagnetic conjugate points at Tjörnes (TJO; 66.2°N, 342.9°E) in Iceland and Syowa Station (SYO; 69.0°S, 39.6°E) in Antarctica. Around postmidnight, just after the substorm onset, the ASC field of view (FOV) at TJO was first filled with dynamic auroral activations; however, its counterpart was not detected over the zenith at SYO at that time. In contrast, in the late stage (about 20 min after the onset) of substorm development we observed spiral‐like auroral arcs with a similar shape drifting eastward across the center of each ASC FOV, although the one at TJO preceded the one at SYO. The time sequence of the interhemispheric conjugate auroral features was well reflected in the geomagnetic field variations at both stations. On the basis of a detailed comparison of both ASC images, we identified that the northern geomagnetic footprint of SYO was displaced poleward of TJO by up to 3.0° or more in the initial stage of substorm development, whereas in the late stage it was displaced eastward by up to ∼1 h relative to TJO and then moved closer to TJO. We emphasize that the dynamic motion of the conjugate points is a consequence of the time‐dependent magnetotail field reconfiguration process, controlled by the varying interplanetary magnetic field By polarity.