Field response of the northern spruce bark beetle Ips duplicatus (Sahlberg) (Coleoptera: Curculionidae,Scolytinae) to different combinations of synthetic pheromone with (−)‐α‐pinene and (+)‐limonene

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Drug‐binding energetics of human α‐1‐acid glycoprotein assessed by isothermal titration calorimetry and molecular docking simulations

This study utilizes sensitive, modern isothermal titration calorimetric methods to characterize the microscopic thermodynamic parameters that drive the binding of basic drugs to α‐1‐acid glycoprotein (AGP) and thereby rationalize the thermodynamic data in relation to docking models and crystallographic structures of the drug–AGP complexes. The binding of basic compounds from the tricyclic antidepressant series, together with miaserine, chlorpromazine, disopyramide and cimetidine, all displayed an exothermically driven binding interaction with AGP. The impact of protonation/deprotonation events, ionic strength, temperature and the individual selectivity of the A and F1*S AGP variants on drug‐binding thermodynamics was characterized. A correlation plot of the thermodynamic parameters for all of the test compounds revealed that an enthalpy–entropy compensation is in effect. The exothermic binding energetics of the test compounds were driven by a combination of favorable (negative) enthalpic (?Hº) and favorable (positive) entropic (?Sº) contributions to the Gibbs free energy (?Gº). Collectively, the data imply that the free energies that drive drug binding to AGP and its relationship to drug serum residency evolve from the complex interplay of enthalpic and entropic forces from interactions with explicit combinations of hydrophobic and polar side‐chain sub‐domains within the multi‐lobed AGP ligand binding cavity.Copyright © 2012 John Wiley & Sons, Ltd.     

The Asymmetry of (−)α‐Pinene as Revealed from its Raman Optical Activity Spectrum

An algorithm is employed to retrieve the differential bond polarizabilities of the C‐C bonds from the Raman optical activity (ROA) spectrum of (?)α‐pinene. (?)α‐pinene possesses two asymmetric centers (carbon atoms) and a local mirror symmetry. These differential bond polarizabilities show the characteristics of the asymmetry around the asymmetric carbons with respect to the mirror reflection. This analysis is accompanied along with the ROA mode signatures and the calculated β(G ')² and β(A)²which show the ROA coupling mechanisms involving the electric/magnetic dipoles and the electric dipole/quadrupole, respectively. Chirality 25:600–605, 2013. © 2013 Wiley Periodicals, Inc.     

Probing the interaction of distamycin A with S100β: the “unexpected” ability of S100β to bind to DNA‐binding ligands

DNA‐minor‐groove‐binding ligands are potent antineoplastic molecules. The antibiotic distamycin A is the prototype of one class of these DNA‐interfering molecules that have been largely used in vitro. The affinity of distamycin A for DNA is well known, and the structural details of the complexes with some B‐DNA and G‐quadruplex‐forming DNA sequences have been already elucidated. Here, we show that distamycin A binds S100β, a protein involved in the regulation of several cellular processes. The reported affinity of distamycin A for the calcium(II)‐loaded S100β reinforces the idea that some biological activities of the DNA‐minor‐groove‐binding ligands arise from the binding to cellular proteins. Copyright © 2015 John Wiley & Sons, Ltd.     

The pyrolysis of (−)‐(S)‐nicotine: Racemization and decomposition

The pyrolytic behaviour of (?)‐(S)‐nicotine in methanol was investigated using on‐line pyrolysis GC/MS to establish whether racemization to the R(+) antipode occurs and to identify other products of pyrolysis. The conditions used included pyrolysing the sample for 15 seconds in an atmosphere of 9% oxygen in nitrogen (275ml/min total flow) across the temperature range of 200°C–1000°C. A chiral Cyclodex‐B analytical column (30m × 0.25mm i.d. × 0.25 μm film thickness) was used to separate the enantiomers of nicotine, although the two enantiomer peaks were not baseline resolved. The results of the experiment shows that there is no increase in (+)‐(R)‐nicotine levels across a wide temperature range. This suggests that the elevated levels of (+)‐R‐nicotine observed in tobacco smoke (compared to tobacco leaf material) are not due to the pyrolytic auto‐racemization of (?)‐(S)‐nicotine but are a result of more complex interactions between (?)‐(S)‐nicotine and other smoke components. The pyrolysis of isotopically labelled nicotine established that nicotine undergoes thermal decomposition to β‐nicotyrine which in turn may decompose to other products. Chirality 2010. © 2009 Wiley‐Liss, Inc.     

Enantiomeric Separation of Bicyclo[2.2.2]octane‐Based 2‐Amino‐3‐Carboxylic Acids on Macrocyclic Glycopeptide Chiral Stationary Phases

Direct high‐performance liquid chromatographic (HPLC) separation of four bicyclo[2.2.2]octane based 2‐amino‐3‐carboxylic acid enantiomers were developed on chiral stationary phases (CSPs) containing different macrocyclic glycopeptide antibiotic selectors. The analyses were performed under reversed‐phase, polar organic and polar ionic mode on macrocyclic‐glycopeptide‐based Chirobiotic T, T2, TAG, and R columns. The effects of the mobile phase composition including the acid and base modifier, the structure of the analytes, and the temperature on the separations were investigated. Experiments were achieved at constant mobile phase compositions on different stationary phases in the temperature range 5–40°C. Thermodynamic parameters were calculated from plots of ln k or ln α versus 1/T. It was recognized that the enantioseparations in reversed‐phase and polar organic mode were enthalpically driven, but under polar‐ionic conditions entropically driven enantioseparation was observed as well. Baseline separation and determination of elution sequence were achieved in all cases. Chirality 26:200–208, 2014. © 2014 Wiley Periodicals, Inc.     

Conformations of peptides containing a chiral cyclic α, α‐disubstituted α‐amino acid within the sequence of Aib residues

A single chiral cyclic α,α‐disubstituted amino acid, (3S,4S)‐1‐amino‐(3,4‐dimethoxy)cyclopentanecarboxylic acid [(S,S)‐Ac₅c^dOM], was placed at the N‐terminal or C‐terminal positions of achiral α‐aminoisobutyric acid (Aib) peptide segments. The IR and ¹H NMR spectra indicated that the dominant conformations of two peptides Cbz‐[(S,S)‐Ac₅c^dOM]‐(Aib)₄‐OEt ( 1) and Cbz‐(Aib)₄‐[(S,S)‐Ac₅c^dOM]‐OMe (2) in solution were helical structures. X‐ray crystallographic analysis of 1 and 2 revealed that a left‐handed (M) 3₁₀‐helical structure was present in 1 and that a right‐handed (P) 3₁₀‐helical structure was present in 2 in their crystalline states. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.     

Enantioselective σ1 receptor binding and biotransformation of the spirocyclic PET tracer 1′‐benzyl‐3‐(3‐fluoropropyl)‐3H‐spiro[[2]benzofuran‐1,4′‐piperidine]

It was shown that racemic (±)‐ 2 [1′‐benzyl‐3‐(3‐fluoropropyl)‐3H‐spiro[[2]benzofuran‐1,4′‐piperidine], WMS‐1813 ] represents a promising positron emission tomography (PET) tracer for the investigation of centrally located σ₁ receptors. To study the pharmacological activity of the enantiomers of 2 , a preparative HPLC separation of (R)‐2 and (S)‐2 was performed. The absolute configuration of the enantiomers was determined by CD‐spectroscopy together with theoretical calculations of the CD‐spectrum of a model compound. In receptor binding studies with the radioligand [³H]‐(+)‐pentazocine, (S)‐2 was thrice more potent than its (R)‐configured enantiomer (R)‐2 . The metabolic degradation of the more potent (S)‐enantiomer was considerably slower than the metabolism of (R)‐2 . The structures of the main metabolites of both enantiomers were elucidated by determination of the exact mass using an Orbitrap‐LC‐MS system. These experiments showed a stereoselective biotransformation of the enantiomers of 2 . Chirality, 2011. © 2010 Wiley‐Liss, Inc.     

Preparation of aminated core‐shell fluorescent nanoparticles and their application to the synchronous fluorescence determination of γ‐globulin

Amino‐modified silica nanoparticles (FSNPs) doped with fluorescein isothiocyanate (FITC) were synthesized by using an aqueous core of reverse‐micelle microemulsion as the nanoreactor in an easy one‐pot method. Due to the FITC conjugating with (3‐aminopropyl)triethoxysilane (APTS), the nanoparticles prevent the FITC from leaching from the silica matrix when immersed in aqueous solution. SEM, FTIR, fluorescence lifetime, a photobleaching experiment and synchronous fluorescence spectra were used to characterize the FSNPs. The synchronous fluorescence signal of FSNPs was enhanced when trace amounts of γ‐globulin (γ‐G) were added. Under the optimal experimental conditions, the enhanced fluorescence intensity (ΔF) was linear with the concentration of γ‐G (c) in the range 0.3–4.8 µg/mL, with a detection limit of 0.04 µg/mL. The proposed method is simple, sensitive for the determination of trace amounts of γ‐G and used to determine the content of γ‐G in synthetic samples with satisfactory results. Copyright © 2008 John Wiley & Sons, Ltd.     

Comparative study of toxic effects of zearalenone and its two major metabolites α‐zearalenol and β‐zearalenol on cultured human Caco‐2 cells

Zearalenone (ZEN) is a fusarotoxin converted predominantly into α‐zearalenol (α‐Zol) and β‐zearalenol (β‐Zol) by hepatic hydroxysteroid dehydrogenases. The feeding of naturally contaminated grains with ZEN was associated with hyperestrogenic and adverse effects on humans and animals. There is a lack of information on the attribution of the toxic effects of these toxins. One wonders if these effects are due to the parent molecule (ZEN) or to its major metabolites (α‐Zol and β‐Zol). Using human Caco‐2 cells, we looked for the molecular mechanisms of toxicity of ZEN, α‐Zol, and β‐Zol. Toxicity effects were studied by MTT viability assay and oxidative stress induction by measuring malondialdehyde (MDA) generation. To check whether the oxidative stress induction was associated to DNA lesions, we looked for DNA fragmentation by means of the Comet and the diphenylamine assays. To specify cell death pathway, we investigated caspase‐3 activation, confirmed by poly(ADP‐ribose) polymerase cleavage and by Bcl‐2 depletion. Our results clearly demonstrated that ZEN as well as its two metabolites presented variable toxic effects. They induced cell death and an increase in MDA generation. These effects were associated to DNA fragmentation as well as caspase‐3 activation. The observed toxic effects seem to be relieved by the metabolism of ZEN into α‐Zol and β‐Zol. © 2009 Wiley Periodicals, Inc. J Biochem Mol Toxicol 23:233–243, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20284     

A novel Fe(II)/α‐ketoglutarate‐dependent dioxygenase from Burkholderia ambifaria has β‐hydroxylating activity of N‐succinyl l‐leucine

An Fe(II)/α‐ketoglutarate‐dependent dioxygenase, SadA, was obtained from Burkholderia ambifaria AMMD and heterologously expressed in Escherichia coli. Purified recombinant SadA had catalytic activity towards several N‐substituted l‐amino acids, which was especially strong with N‐succinyl l‐leucine. With the NMR and LC‐MS analysis, SadA converted N‐succinyl l‐leucine into N‐succinyl l‐threo‐β‐hydroxyleucine with >99% diastereoselectivity. SadA is the first enzyme catalysing β‐hydroxylation of aliphatic amino acid‐related substances and a potent biocatalyst for the preparation of optically active β‐hydroxy amino acids.     

Syntheses and β‐adrenergic binding affinities of (R)‐ and (S)‐fluoronaphthyloxypropanolamines

The β‐adrenergic receptors mediate several physiological processes including heart rate (β₁), bronchodilation (β₂), and lipolysis (β₃). Therefore, selectivity is important for a possible therapeutic agent acting via these receptors. Aryloxypropanolamines are β‐receptor agonists or antagonists, depending on the aryl group and its substituents. We therefore hypothesized that fluorine substitution on the aromatic ring in this class could lead to significant biological effects because of the unique chemical characteristics of fluorine. Because the target compound has a chiral center, we set out to synthesize the two enantiomers so that effects of stereochemistry on biological activity could be evaluated. Syntheses of the enantiomers were performed starting with commercially available fluoronaphthalene and subsequent use of the chiral synthon (2R)‐ or (2S)‐glycidyl 3‐nitrobenzenesulfonate, depending on the desired enantiomer. High‐pressure liquid chromatography (HPLC) methods were used to characterize %ee. Each enantiomer was synthesized. They exhibited nanomolar binding activities on β‐adrenergic receptors. The (S)‐enantiomer was found to be up to 310 times more potent than the (R). It was also found to be about five‐fold more selective for β₂‐ than for β₁‐receptors. The current report demonstrates the importance of stereochemistry for the fluoroaromatic β‐receptor ligands. Chirality 11:144–148, 1999. © 1999 Wiley‐Liss, Inc.     

Synthesis and antimicrobial activity of α‐aminoboronic‐containing peptidomimetics

A library of 175 dipeptidomimetics and tripeptidomimetics containing an α‐amino boronic acid or boronate has been synthesized, and the activity toward Mycobacterium tuberculosis, Candida albicans, Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Pseudomonas aeruginosa has been screened. Although there is no clear structure–activity relationship, several compounds exhibit promising activity against different pathogens. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.     

Role of oxygen supply in α, ω‐dodecanedioic acid biosynthesis from n‐dodecane by Candida viswanathii ipe‐1: Effect of stirring speed and aeration

α, ω‐Dodecanedioic acid (DC₁₂) usually serves as a monomer of polyamides or some special nylons. During the biosynthesis, oxygenation cascaded in conversion of hydrophobic n‐dodecane to DC₁₂, while the oxidation of n‐dodecane took place in the intracellular space. Therefore, it was important to investigate the role of oxygen supply on the cell growth and DC₁₂ biosynthesis. It was found that stirring speed and aeration influenced the dissolved oxygen (DO) concentration which in turn affected cell growth as well as DC₁₂ biosynthesis. However, the effect of culture redox potential (Orp) level on DC₁₂ biosynthesis was more significant than that of DO level. For DC₁₂ biosynthesis, the first step was to form the emulsion droplets through the interaction of n‐dodecane and the cell. When the stirring speed was enhanced, slits in the surface layer of the emulsion droplets would be increased. Thus, the substances transportation by water through the slits would be intensified, leading to an enhanced DC₁₂ production. Compared with the batch culture at a lower stirring speed (400 rpm) without culture redox potential (Orp) control, the DC₁₂ concentration was increased by 5 times up to 201.3 g/L with Orp controlled above 0 mV at a higher stirring speed (800 rpm).     

A quantitative anharmonic analysis of the amide A band in α‐helical poly(L‐alanine)

Polarized ir spectra of oriented films of α‐helical poly(l ‐alanine) (α‐PLA) have been obtained as a function of residual solvent dichloroacetic acid (DCA). The amide A, B, II, and V regions exhibit multiple bands whose structure depends on the residual DCA content, and those associated with the α_I‐PLA structure have been identified. A calculation of the relevant cubic anharmonic force constants indicates that, contrary to previous assignments, the overtone of amide II(A) is in Fermi resonance with the NH stretch fundamental, whose unperturbed frequency we now find to be at 3314 cm⁻¹, significantly higher than the previously suggested 3279 cm⁻¹. The presence of a structure in addition to the standard α_I‐PLA is indicated by our analysis. © 1999 John Wiley & Sons, Inc. Biopoly 49: 195–207, 1999     

Engineering the serpin α1‐antitrypsin: A diversity of goals and techniques

α₁‐Antitrypsin (α₁‐AT) serves as an archetypal example for the serine proteinase inhibitor (serpin) protein family and has been used as a scaffold for protein engineering for >35 years. Techniques used to engineer α₁‐AT include targeted mutagenesis, protein fusions, phage display, glycoengineering, and consensus protein design. The goals of engineering have also been diverse, ranging from understanding serpin structure–function relationships, to the design of more potent or more specific proteinase inhibitors with potential therapeutic relevance. Here we summarize the history of these protein engineering efforts, describing the techniques applied to engineer α₁‐AT, specific mutants of interest, and providing an appended catalog of the >200 α₁‐AT mutants published to date.     

The role of the C(2) configuration and methyl substitution on the catalytic activity of novel 2,3,3‐ and 2,7,7‐trimethyl‐substituted γ‐aminonorbornan‐2‐ols

A new set of optically active 2,3,3‐ and 2,7,7‐trimethyl‐substituted γ‐aminonorbornan‐2‐ols have been obtained from 2‐methylenenorbornane‐1‐carbonitriles derived from (+)‐camphor and (?)‐fenchone and probed as chiral ligands for the enantioselective addition of diethylzinc to benzaldehyde. This has allowed the study of the structural factors influencing the chirality transfer, such as variation of the relative configuration at C(2) and steric hindrance at C(2), C(3), and C(7) positions of norbornane, which result in the observance of the important role played by the gem‐dimethyl position in γ‐aminonorbornan‐2‐exo‐ols. An empirical rationalization of the obtained experimental results has been realized on the basis of energetically‐favored diastereomeric Noyori‐like transition states. Chirality 2010. © 2010 Wiley‐Liss, Inc.