bluuebunny/crossref_metadata_2025 huggingface dataset:
Asymmetric enone epoxidation by short solid‐phase bound peptides: Further evidence for catalyst helicity and catalytic activity of individual peptide strands
Authors: Berkessel Albrecht , Koch Burkhard , Toniolo Claudio , Rainaldi Mario , Broxterman Quirinus B. , Kaptein Bernard
Published: November 2005

In the presence of short solid‐phase bound peptide catalysts, the Juliá–Colonna epoxidation of enones (such as chalcone) with hydrogen peroxide can be performed with high enantiomeric excess (≥95% ee). It was proposed earlier (A. Berkessel, N. Gasch, K. Glaubitz, C. Koch, Organic Letters, 2001, Vol. 3, pp. 3839–3842) that this remarkable catalysis is governed by the N‐terminus of individual and helical peptide strands. This mechanistic proposal was scrutinized further. (i) Nonaggregation of the peptide catalysts: five solid‐phase bound statistic mixtures (0/100; 30/70; 50/50; 70/30; 100/0) of D‐Leu and L‐Leu heptamers were generated and assayed as catalysts. A linear dependence of the epoxide ee on the enantiomeric composition of the catalysts resulted. (ii) Catalyst helicity [introduction of the helix‐stabilizing Cα–methyl‐L‐leucine, L‐(αMe)Leu]: solid‐phase bound Leu/(αMe)Leu‐pentamers of composition TentaGel–NH–[(αMe)‐L‐Leu]n–(L‐Leu)m–H (n = 0–4; m = 5–n) were prepared and assayed as catalysts. The introduction of up to two (αMe)‐L‐Leu residues (n = 1, 2) significantly enhanced the catalyst activity relative to the L‐Leu homopentamer (n = 0). Higher (αMe)‐L‐Leu contents (n = 3, 4) led to a decrease in both catalyst activity and enantiopurity of the product epoxide. In summary, both the individual catalytic action of the peptide strands and the helical conformation as the catalytically competent state of the peptide catalysts were further supported. © 2005 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 84: 90–96, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Preparative synthesis of dTDP‐L‐rhamnose through combined enzymatic pathways
Authors: Kang Young‐Bok , Yang Yung‐Hun , Lee Kwang‐Won , Lee Sun‐Gu , Sohng Jae Kyung , Lee Hei Chan , Liou Kwangkyoung , Kim Byung‐Gee
Published: November 2005

dTDP‐L‐rhamnose, an important precursor of O‐antigen, was prepared on a large scale from dTMP by executing an one‐pot reaction in which six enzymes are involved. Two enzymes, dTDP‐4‐keto‐6‐deoxy‐D‐glucose 3,5‐epimerase and dTDP‐4‐keto‐rhamnose reductase, responsible for the conversion of dTDP‐4‐keto‐6‐deoxy‐D‐glucose to dTDP‐L‐rhamnose, were isolated from their putative sequences in the genome of Mesorhizobium loti, functionally expressed in Escherichia coli, and their enzymatic activities were identified. The two enzymes were combined with an enzymatic process for dTDP‐4‐keto‐6‐deoxy‐D‐glucose involving TMP kinase, acetate kinase, dTDP‐glucose synthase, and dTDP‐glucose 4,6‐dehydratase, which allowed us to achieve a preparative scale synthesis of dTDP‐L‐rhamnose using dTMP and glucose‐1‐phosphate as starting materials. About 82% yield of dTDP‐L‐rhamnose was obtained based on initial dTMP concentration at 20 mM dTMP, 1 mM ATP, 10 mM NADH, 60 mM acetyl phosphate, and 80 mM glucose‐1‐phosphate. From the reaction with 20 ml volume, approximately 180 mg of dTDP‐L‐rhamnose was obtained in an overall yield of 60% after two‐step purification, that is, anion exchange chromatography and gel filtration for desalting. The purified product was identified by HPLC, ESI‐MS, and NMR, showing about 95% purity. © 2005 Wiley Periodicals, Inc.
New reaction system for hydrocarbon oxidation by chloroperoxidase
Authors: Park Jin‐Byung , Clark Douglas S.
Published: November 2005

A novel reaction system was developed to maximize the catalytic efficiency of chloroperoxidase (CPO, from Caldariomyces fumago) toward the oxidation of hydrocarbons. The reaction system consisted of an organic/aqueous emulsion comprising pure substrate and aqueous buffer supplemented with the surfactant dioctyl sulfosuccinate. The emulsion system attenuated not only the destabilizing effects of the substrate and product on the enzyme by emulsifying the compounds, but also oxidant toxicity (oxidative stress) by increasing substrate availability. As a result, CPO exhibited total turnover numbers (TTNs, defined as the amount of product produced over the catalytic lifetime of the enzyme) of ca. 20,000 mol product/mol enzyme for the oxidation of styrene, toluene, and o‐, m‐, p‐xylenes. The TTNs are over 10‐fold higher than those previously reported for the oxidation of benzylic hydrocarbons by CPO. This study represents a significant step toward the development of CPO as a practical catalyst for large‐scale organic syntheses. © 2005 Wiley Periodicals, Inc.
Anorectal motility responses to selective stimulation of the ventral sacral nerve roots in an experimental model
Authors: Andersen I S , Rijkhoff N J M , Vukovic A , Buntzen S , Djurhuus J C , Laurberg S
Published: November 2005

Background

Control of defaecation and continence may be lost in patients with spinal cord injury. Electrical stimulation of sacral nerve roots to promote defaecation simultaneously activates both the rectum and the external anal sphincter (EAS), and may actually obstruct defaecation. The aim of this study was to investigate whether the EAS could be blocked selectively by selective stimulation of the ventral sacral nerve roots, and whether activation of the rectum without activation of the EAS could be obtained by stimulation of the ventral sacral nerve roots.

Methods

Selective electrical stimulation was performed using anodal blocking, a tripolar cuff electrode and monophasic rectangular current pulses applied to the sacral nerve roots in nine Göttingen minipigs.

Results

Simultaneous responses in the rectum and the anal canal were observed in five animals, whereas only anal responses were noted in four. Variations in cross-sectional area and an increase in rectal pressure seemed to facilitate defaecation. Without blocking, the increase in anal canal pressure was 16–45 cmH2O. With blocking, this increase was abolished in seven and reduced to 3–6 cmH2O in two animals.

Conclusion

Selective activation of the rectum is possible using an anodal block of somatic motor fibres. This technique holds promise in further development of electro-defaecation.
Inadvertent tracheal perforation during thyroidectomy
Authors: Gosnell J E , Campbell P , Sidhu S , Sywak M , Reeve T S , Delbridge L W
Published: November 2005

Valuable advice for thyroid surgeons
Operative mortality after colorectal resection in the Netherlands
Authors: Engel A F , Oomen J L T , Knol D L , Cuesta M A
Published: November 2005

Background

The aim of this study was to quantify factors related to operative mortality after colorectal resection in the Netherlands.

Methods

Multilevel logistic regression modelling was used. Institutional effects were calculated with and without adjustment for specific patient (age, sex, urgency of operation) and hospital (number of procedures, type of hospital) characteristics. All adult Dutch patients who underwent primary colorectal resection between 1994 and 1999 were included, except those who had (sub)total colectomy or local rectal resection.

Results

A total of 67 594 patients underwent colorectal resection. The in-hospital mortality rate was 7·0 per cent (elective 3·9 per cent, acute 14·3 per cent). Acute operation (odds ratio 3·89) and age (odds ratios 2·63, 5·23 and 10·13 for patients aged 50–69, 70–79 and 80 or more years respectively compared with those aged less than 50 years) had the strongest effects, followed by male sex (odds ratio 1·48) and type of hospital. There was no difference in operative mortality rate between low-, medium- and high-volume hospitals.

Conclusion

In the Netherlands, advanced age and acute operation are by far the most important factors related to operative mortality after colorectal resection. Male sex and type of hospital have only a modest effect, and there is no discernible effect of hospital volume.
The evolving role of gene-based treatment in surgery
Authors: Tan P H , Chan C L H , Chan C , George A J T
Published: November 2005

Background

The completion of the sequencing of the human genome in 2003 marked the dawn of a new era of human biology and medicine. Although these remarkable scientific advances improve the understanding of human biology, the question remains how this rapidly expanding knowledge of functional genomics affects the role of surgeons. This article reviews the potential therapeutic application of gene therapy for various surgical conditions.

Methods

The core of this review was derived from a Medline database literature search.

Results and conclusion

The currently available vectors in the field of gene therapy and their limitations for clinical applications were analysed. The achievements of gene therapy in clinical trials and the future ramifications for surgery were also explored. Whether gene therapy takes a major role in surgical practice will depend greatly on the success of future vector development. Advances in viral vector technology to reduce the inflammatory effect, and improvements in the efficiency of gene delivery using non-viral vector technology, would allow this form of therapy to become more clinically applicable.
Duct-to-mucosa pancreaticogastrostomy is a safe anastomosis following pancreaticoduodenectomy
Authors: Payne R F , Pain J A
Published: November 2005

Background

Pancreatic fistula following pancreaticoduodenectomy is relatively common, and remains a major cause of morbidity and mortality. The aim of this study was to evaluate the results of two-layered duct-to-mucosa pancreaticogastrostomy as a method for restoring pancreaticoenteric continuity.

Methods

Prospectively collected data from 100 consecutive patients who underwent Whipple's pancreaticoduodenectomy for tumour were evaluated. All operations were performed by the same surgeon.

Results

The perioperative 60-day mortality rate was 1·0 per cent. There were no pancreatic fistulas or anastomotic leaks. Sixteen patients had significant complications that delayed discharge from hospital. Twenty-one patients subsequently required empirical pancreatic exocrine supplements.

Conclusion

Two-layered duct-to-mucosa pancreaticogastrostomy for restoration of pancreaticoenteric continuity after pancreaticoduodenectomy is associated with a low incidence of complications.
Collateral warranties: time to break the habit
Authors: Cockram Richard
Published: November 2005

Under English law, one can in general, only sue on a contract if one is a party to it. In simple cases, this is not a problem. However, not all cases are simple. Take, for example, a development project. Key contractual documents are the building contract/subcontracts and also the appointments under which the various consultants are engaged. They contain core obligations, where only the developer and/or the main contractor are the benefiting parties. However, other key players, such as a funder, a purchaser or an occupational tenant, will only participate in the development if they too can enforce those promises. Using collateral warranties is the traditional method for achieving this. In this paper, it will be explained how The Contract (Rights of Third Parties) Act 1999 has created an opportunity to abandon the use of contractors' and consultants' warranties by giving non‐parties to a contract the right to enforce its provisions in cases where the contract expressly provides or clearly intends that they should be able to do so. Copyright © 2005 John Wiley & Sons, Ltd.
High incidence of the os peroneum in a cadaver sample in Johannesburg, South Africa: Possible clinical implications?
Authors: Oyedele Olusegun , Maseko Constance , Mkasi Nkateko , Mashanyana Matshidiso
Published: November 2005

This study set out to investigate the incidence of the os peroneum in a cadaver sample from Johannesburg, South Africa and to note how bio‐demographic parameters affect such incidence. The os peroneum (OP) is a sesamoid bone frequently found in the tendon of the fibularis longus muscle (FLM), as it passes on the plantar aspect of the cuboid bone. While this bone is often an incidental dissection room or radiological finding, OP fractures, with or without associated rupture of the fibularis (peroneus) longus tendons have been reported. Some investigators have also suggested that the presence of the OP may render the tendon of the FLM susceptible to avulsion injuries. The reported incidences of the OP range between 8 and 26%. These data have emanated by and large from radiographic rather than dissection studies, and the influences of biological indices such as age, sex, population group of origin, and side of the body on these incidences remain largely unknown. Forty cadavers (average age = 75 years) were dissected. Os peronei were present in 36 of these cadavers (90.0%), with 96% of them occurring bilaterally. This bilateral incidence was statistically significant (P = 0.007), but there was no significant difference in age (P = 0.38), sex (P = 0.97), or population group (P = 0.17). We hope that the unusually high incidence of the OP reported here will stimulate further research into possible predisposing factors as well as into the speculated associations between sesamoid occurrence, osteoarthritis, and tendon injuries. Clin. Anat. 19:605–610, 2006. © 2005 Wiley‐Liss, Inc.
Discovery of Complex Mixtures of Novel Long‐Chain Quorum Sensing Signals in Free‐Living and Host‐Associated Marine Alphaproteobacteria
Authors: Wagner‐Döbler Irene , Thiel Verena , Eberl Leo , Allgaier Martin , Bodor Agnes , Meyer Sandra , Ebner Sabrina , Hennig Andreas , Pukall Rüdiger , Schulz Stefan
Published: November 2005

More than 100 bacterial isolates from various marine habitats were screened for AHL production by using gfp reporter constructs based on the lasR system of Pseudomonas aeruginosa and the luxR system of Vibrio fischeri. Of the 67 Alphaproteobacteria tested, most of which belonged into the so‐called Roseobacter clade, 39 induced fluorescence in either one or both sensor strains up to 103‐fold compared to controls. Acylated homoserine lactones were identified by GC‐MS analysis and shown to have chain lengths of C8, C10, C13–C16, and C18. One or two double bonds were often present, while a keto or hydroxyl group occurred only rarely in the side chain. Most strains produced several different AHLs. C18‐en‐HSL and C18‐dien‐HSL were produced by Dinoroseobacter shibae, an aerobic anoxygenic phototrophic bacterium isolated from dinoflagellates, and are among the longest AHLs found to date. Z7‐C14‐en‐HSL, which has previously been detected in Rhodobacter sphaeroides, was produced by Roseovarius tolerans and Jannaschia helgolandensis. This signal molecule was synthesised and shown to induce a similar response to the culture supernatant in the respective sensor strain. The widespread occurrence of quorum‐sensing compounds in marine Alphaproteobacteria, both free‐living strains and those associated to eukaryotic algae, points to a great importance of this signalling mechanism for the adaptation of the organisms to their widely different ecological niches.
Solution NMR Studies of an Intrinsically Unstructured Protein within a Dilute, 75 kDa Eukaryotic Protein Assembly; Probing the Practical Limits for Efficiently Assigning Polypeptide Backbone Resonances
Authors: Wang Yuefeng , Filippov Igor , Richter Christian , Luo Rensheng , Kriwacki Richard W.
Published: November 2005

This paper describes an efficient NMR strategy for assigning the backbone resonances of an intrinsically unstructured protein (IUP), p21‐KID, bound to its biological target, Cdk2/cyclin A. In order to overcome the challenges associated with the high molecular weight (75 kDa) and low solubility of the ternary complex (0.2 mM), we used perdeuteration, TROSY, and high‐sensitivity cryogenic NMR probes at high magnetic‐field strengths (i.e. 16.4, 18.8 and 21.1 Tesla). p21‐KID was also prepared by using specific amino acid isotope labels. Most importantly, we studied binary, subcomplexes that allowed resonance assignments to be made in stages. We show that subdomains of p21‐KID folded within binary complexes into the same conformations as observed in the ternary, Cdk2/cyclin A complex. This is a general feature of IUPs, which often adopt highly extended conformations when bound to other proteins. This strategy is suitable for studies of IUPs within considerably larger biomolecular assemblies as long as the IUP can be uniformly and selectively isotope labeled.
Predicting Protein Retention Time in Hydrophobic Interaction Chromatography
Authors: Lienqueo M. E. , Mahn A.
Published: November 2005

A review of hydrophobic interaction chromatography (HIC) of proteins and theories for predicting protein retention time in HIC is given in this paper. A brief description of HIC, hydrophobic interactions and amino acid and protein hydrophobicity is presented and different approaches and models for explaining the retention mechanism of proteins and predicting protein retention time in HIC are described. By using these models it is possible to test different operating conditions for the purification of a target protein and to select the best conditions.
Design Considerations for the Batch Capture of Proteins from Raw Whole Milk by Ion Exchange Chromatography
Authors: Fee C. J. , Chand A.
Published: November 2005

The on‐farm extraction of proteins directly from raw whole milk is a promising approach for the production of minor, high‐value proteins from conventional milk and for the production of recombinant proteins from the milk of transgenic animals. The main advantage of the stirred tank process is that protein extraction is rapid and is achieved in a single step without the need for a pre‐treatment. It also includes the minimization of microbial growth and the potential for batch traceability between individual animals and final product lots.
Protein Engineering Strategies for Selective Protein Purification
Authors: Hedhammar M. , Gräslund T. , Hober S.
Published: November 2005

When producing and purifying recombinant proteins it is of importance to minimize the number of unit operations during the purification procedure. This is accomplished by increasing the selectivity in each step. Due to the high selectivity of affinity chromatography it has a widespread use in protein purification. However, most target proteins lack a suitable affinity ligand usable for capture on a solid matrix. A way to circumvent this obstacle is to genetically fuse the gene encoding the target protein with a gene encoding a purification tag. When the chimeric protein is expressed, the tag allows for specific capture of the fusion protein. In industrial‐scale production, extension of the target protein often is unwanted since it might interfere with the function of the target protein. Hence, a purification scheme developed for the native protein is desired. In this review, different fusion strategies used for protein purification are discussed. Also, the development of ligands for selective affinity purification of native target proteins is surveyed.
Chromatographic Approaches in the Purification of Plasmid DNA for Therapy and Vaccination
Authors: Ferreira G. N. M.
Published: November 2005

The need for large scale plasmid DNA purification processes has increased in the last few years due to the rapid evolution of gene therapy and DNA vaccines. Chromatographic purification of plasmid DNA has specific problems which are mostly related to the structural nature of plasmid DNA, the resemblance of plasmid DNA to some impurities, and the lack of capacity and selectivity of the traditional bead adsorbents. In this paper, plasmid DNA purification using chromatographic processes is reviewed. Initially the most relevant structural and chemical properties of supercoiled plasmid DNA and related impurities are described, and the purification objectives are specified. The most significant properties are highlighted and their possible exploitation for plasmid DNA adsorption is described. After a brief description of currently used chromatographic purification strategies, novel approaches centered on the use and development of new stationary phases with higher capacity utilization are described.
Development and Scale up of Preparative HIC for the Purification of a Recombinant Therapeutic Protein
Authors: Graumann K. , Ebenbichler A. A.
Published: November 2005

In the biopharmaceutical industry, process development has to overcome the paradox between increasing demands on product quality and aggressive overall development time lines. Streamlining development and scale‐up has become a requirement in order to cope with these constraints. Hydrophobic interaction chromatography (HIC) has gained popularity as an efficient tool in downstream process development, which represents an orthogonal method compared to other widely used chromatography principles. Thus, host cell protein (HCP) removal combined with the separation of product variants based on subtle differences in hydrophobicity are major strengths of this separation technique. The development and scale‐up of a preparative HIC step for a therapeutic protein for human use is described. Issues like the removal of product‐ and process‐related impurities have been addressed. The direct transferability of the results, from scale‐down optimization experiments via the pilot scale to the final production scale, clearly show the robustness and power of HIC in this process context.
Potential for Using Histidine Tags in Purification of Proteins at Large Scale
Authors: Gaberc‐Porekar V. , Menart V.
Published: November 2005

Attachment of oligo‐histidine tag (His‐tag) to the protein N‐ or C‐terminus is a good example of early and successful protein engineering to design a unique and generalized purification scheme for virtually any protein. Thus relatively strong and specific binding of His‐tagged protein is achieved on an Immobilized Metal‐Ion Affinity Chromatography (IMAC) matrix. Most popular hexa‐histidine tag and recently also deca‐histidine tag are used in combination with three chelating molecules: iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), and carboxymethyl aspartic acid (CM‐Asp), covalently attached to the chromatographic matrix. The following combinations with divalent metal ions are preferentially used: (Cu, Zn, Ni, Co)‐IDA, Ni‐NTA, and Co‐CM‐Asp. At large scale, regarding cost and product purity, a decisive step is precise and efficient cleavage of His‐tag by the cleavage enzyme. Two‐step IMAC followed by a polishing step appears to be a minimum but still realistic as an approach to generic technology also for more demanding products. Possible drawbacks in using His‐tags and IMAC, such as leaching of metal ions, inefficient cleavage, and batch‐to‐batch reproducibility must be carefully evaluated before transferred to large scale. Although a great majority of reports refer to small laboratory scale isolations for research purposes it appears there is much higher potential for more extensive use of His‐tags and IMAC at large scale than currently documented.
Noninvasive Methods for Characterization of Large‐Volume Monolithic Chromatographic Columns
Authors: Podgornik A. , Vidič J. , Jančar J. , Lendero N. , Frankovič V. , Štrancar A.
Published: November 2005

Chromatographic monoliths exhibit several properties like flow‐unaffected resolution and dynamic binding capacity, low pressure drop and high capacity for extremely large molecules, which are advantageous to the purification of large biomolecules such as proteins, DNA or even viruses. Recently, large‐volume monolithic columns were introduced enabling the monoliths to be incorporated into industrial downstream processes. Due to the monolithic structure, however, conventional methods for resin characterization cannot be applied to monoliths, which limit their usage under cGMP conditions. In this article, a methodology of how to overcome this problem and to determine the most important parameters is presented. Several fast and noninvasive methods for monolith characterization are introduced. Their usage enables accurate determination of monolith pore size distribution and specific surface area, uniformity of the monolith as well as type and density of the active groups before or during monolith usage.
Desensitizing models using covariance matrix transforms or counter‐balanced distortions
Authors: DiFoggio Rocco
Published: November 2005

This paper presents a generalization of the Lagrange multiplier equation for a regression subject to constraints. It introduces two methods for desensitizing models to anticipated spectral artifacts such as baseline variations, wavelength shift, or trace contaminants. For models derived from a covariance matrix such as multiple linear regression (MLR) and principal components regression (PCR) models, the first method shows how a covariance matrix can be desensitized to an artifact spectrum, v, by adding σ2 v ⊗ v to it. For models not derived from a covariance matrix, such as partial least squares (PLS) or neural network (NN) models, the second method shows how distorted copies of the original spectra can be prepared in a counter‐balanced manner to achieve desensitization. Unlike earlier methods that added random distortions to spectra, these new methods never introduce any accidental correlations between the added distortions and the Y‐block. The degree of desensitization is controlled by a parameter, σ, for each artifact from zero (no desensitization) to infinity (complete desensitization, which is the Lagrange multiplier limit). Unlike Lagrange multipliers, these methods permit partial desensitization so we can individually vary the degree of desensitization to each artifact, which is important when desensitization to one artifact inhibits desensitization to another. Copyright © 2005 John Wiley & Sons, Ltd.
Decacyclene as Complexation Manifold: Synthesis, Structure and Properties of Its Fe2 and Fe4 Slipped Triple‐Decker Complexes
Authors: Schneider Jörg J. , Spickermann Dirk , Lehmann Christian W. , Magull Jörg , Krüger Hans‐Jörg , Ensling Jürgen , Gütlich Philipp
Published: November 2005

Reaction of [(η5‐Me4EtC5)FeIICl(tmeda)] (tmeda=N,N,N′N′‐tetramethylethylenediamine) with a polyanion solution of decacyclene (1) results in the formation of the triple‐deckers [{(η5‐Me4EtC5)Fe}2‐μ2‐(η6:η6‐decacyclene)] (3) and [{(η5‐Me4EtC5)Fe}4‐μ4‐(η6:η6:η6:η6‐decacyclene)] (4). Metal complexation in 3 and 4 occurs on opposite faces of the π perimeter in an alternating mode. The decacyclene ring adopts a gently twisted molecular propeller geometry with twofold crystallographic symmetry (C2). Complex 4 crystallizes in the chiral space group C2221; the investigated crystal only contains decacyclene rings with M chirality. The handedness can be assigned unambiguously to the presence of the iron atoms. Cyclovoltammetric studies revealed quasireversible behavior of the redox events and a strong interaction of the Fe atoms in 3 and 4, exemplified by potential differences ΔE of 660 and 770(780) mV between the first and the second individual oxidation processes. This corresponds to a high degree of metal–metal interaction for 3 and 4. The sucesssful syntheses of 3 and 4 together with earlier results from our laboratory proves that all five‐ and six‐membered π subunit sets of 1 are prone to metal complexation. A clear site preference in 1 towards the complexation of [CpR]iron, ‐cobalt, and ‐nickel fragments exists.
A Designed Well‐Folded Monomeric Four‐Helix Bundle Protein Prepared by Fmoc Solid‐Phase Peptide Synthesis and Native Chemical Ligation
Authors: Dolphin Gunnar T.
Published: November 2005

The design and total chemical synthesis of a monomeric native‐like four‐helix bundle protein is presented. The designed protein, GTD‐Lig, consists of 90 amino acids and is based on the dimeric structure of the de novo designed helix‐loop‐helix GTD‐43. GTD‐Lig was prepared by the native chemical ligation strategy and the fragments (45 residues long) were synthesized by applying standard fluorenylmethoxycarbonyl (Fmoc) chemistry. The required peptide–thioester fragment was prepared by anchoring the free γ‐carboxy group of Fmoc‐Glu‐allyl to the solid phase. After chain elongation the allyl moiety was orthogonally removed and the resulting carboxy group was functionalized with a glycine–thioester followed by standard trifluoroacetic acid (TFA) cleavage to produce the unprotected peptide–thioester. The structure of the synthetic protein was examined by far‐ and near‐UV circular dichroism (CD), sedimentation equilibrium ultracentrifugation, and NMR and fluorescence spectroscopy. The spectroscopic methods show a highly helical and native‐like monomeric protein consistent with the design. Heat‐induced unfolding was studied by tryptophan absorbance and far‐UV CD. The thermal unfolding of GTD‐Lig occurs in two steps; a cooperative transition from the native state to an intermediate state and thereafter by noncooperative melting to the unfolded state. The intermediate exhibits the properties of a molten globule such as a retained native secondary structure and a compact hydrophobic core. The thermodynamics of GuHCl‐induced unfolding were evaluated by far‐UV CD monitoring and the unfolding exhibited a cooperative transition that is well‐fitted by a two‐state mechanism from the native to the unfolded state. GTD‐Lig clearly shows the characteristics of a native protein with a well‐defined structure and typical unfolding transitions. The design and synthesis presented herein is of general applicability for the construction of large monomeric proteins.
Synthesis of ansa‐[n]Silacyclopentadienyl–Cycloheptatrienyl–Chromium Complexes (n = 1, 2): Novel Precursors for Polymers Bearing Chromium in the Backbone
Authors: Bartole‐Scott Alexandra , Braunschweig Holger , Kupfer Thomas , Lutz Matthias , Manners Ian , Nguyen Thi‐loan , Radacki Krzysztof , Seeler Fabian
Published: November 2005

Reaction of [(η5‐C5H4Li)(η7‐C7H6Li)Cr]⋅tmeda with a variety of dialkyl(dichloro)silanes in aliphatic solvents afforded the corresponding [1]silatrochrocenophanes. Structural characterization by X‐ray diffraction analysis of the [1]silatrochrocenophanes bearing Me2Si, (iPr)2Si, and silacyclobutane bridges revealed tilt angles α of 15.56(12)°, 15.8(1)°, and 16.33(17)°, respectively. Analogously, a [2]silatrochrocenophane (6) was prepared in excellent yield by reaction of [(η5‐C5H4Li)(η7‐C7H6Li)Cr]⋅tmeda with 1,2‐dichloro‐1,1,2,2‐tetramethyldisilane. This complex also was characterized structurally and exhibited a tilt angle α of 2.60(15)°. The [1]silatrochrocenophane bearing the Me2Si bridge underwent facile and regioselective carbon–silicon bond cleavage with [Pt(PEt3)4] to give a very high yield of an oxidative addition product. The ring‐opening polymerization of these novel [1]silatrochrocenophanes afforded ring‐opened chromium‐based polymers.
Synthesis and Structure of Novel Organocycloborates
Authors: Braunschweig Holger , D'Andola Giovanni , Welton Tom , White Andrew J. P.
Published: November 2005

A series of α,ω‐boryl(bromo)alkanes of the general formula R2B(CH2)nBr (n=3, 4, 5, 6) was obtained in high yield following a standard hydroboration protocol. Upon treatment with Mg turnings and formation of the respective Grignard species, all alkanes with n=4 to 6 underwent an unprecedented boron‐centered cyclisation reaction with formation of boratacyclopentanes, ‐hexanes, and ‐heptanes, respectively. All new compounds were isolated in high yields as colourless, crystalline materials and characterised in solution by multinuclear NMR spectroscopy. Four representative examples were chosen for X‐ray diffraction studies, thus providing the first structurally characterised ring systems of that size at a tetraalkyl borate centre.
On the Rigidity of Polynorbornenes with Dipolar Pendant Groups
Authors: Lin Wei‐Yu , Murugesh Modachur G. , Sudhakar Sundarraj , Yang Hsiao‐Ching , Tai Hwan‐Ching , Chang Chia‐Seng , Liu Yi‐Hung , Wang Yu , Chen I‐Wen Peter , Chen Chun‐hsien , Luh Tien‐Yau
Published: November 2005

A range of polynorbornenes (PNBs) with fused dipolar pendant groups at C‐5,6 positions was synthesized by ring‐opening metathesis polymerization catalyzed by a ruthenium carbene complex (Grubbs I). Photophysical studies, EFISH measurements, and atomic force microscopy images have been used to investigate the structures and morphology of these polymers. These results suggest that the polymers may adopt rigid rod‐like structures. The presence of the double bonds in PNBs appeared to be indispensable for the rigidity of the polymers. Interaction between unsaturated pendant groups may result in coherent alignment leading to a rod‐like structure.
A Mechanistic and Kinetic Study of the Formation of Metal Nanoparticles by Using Synthetic Tyrosine‐Based Oligopeptides
Authors: Si Satyabrata , Bhattacharjee Rama Ranjan , Banerjee Arindam , Mandal Tarun K.
Published: November 2005

Synthetic oligopeptides containing redox‐active tyrosine residues have been employed to prepare gold and silver nanoparticles. In this reduction process an electron from the tyrosinate ion of the peptide is transferred to the metal ion at basic pH through the formation of a tyrosyl radical, which is eventually converted to its dityrosine form during the reaction. This reaction mechanism was confirmed from UV‐visible, fluorescence, and EPR spectroscopy and was found to be pH‐dependent. Transmission electron microscopy measurement shows that the average size and the monodispersity of gold nanoparticles increase as the number of tyrosine residues in the peptide increases. The kinetic study, based on spectrophotometric measurements of the surface plasmon resonance optical property, shows that the rate of formation of gold nanoparticles was much faster at higher pH than at lower pH and was also dependent on the number of tyrosine residues present in the peptide. The dityrosine form of the peptide was found to retain reducing properties like those of tyrosine in basic medium.
Fine Tuning of the Electronic Properties of Linear π‐Conjugated Oligomers by Covalent Bridging
Authors: Blanchard Philippe , Verlhac Patrick , Michaux Laurent , Frère Pierre , Roncali Jean
Published: November 2005

A series of oligothienylenevinylenes, π‐conjugated oligomers rigidified by ethylene bridges attached at different sites of the conjugated backbone, have been constructed by multistep synthetic methodologies. Electronic absorption spectra show that the rigidification of the conjugated system produces a bathochromic shift of the absorption maximum and a narrowing of the HOMO–LUMO energy gap, as compared to the spectra of an open‐chain reference compound. The cyclic voltammograms of all oligomers show that these compounds can be reversibly oxidized into their cation radicals and dications and that rigidification produces a large negative shift of the first oxidation potential, which is indicative of a considerable increase of the HOMO level. Electrochemical data confirm that covalent bridging strongly affects the HOMO and LUMO levels and these data demonstrate that the sites of fixation of the bridges on the π‐conjugated backbone exert a determining effect on the relative stability of the cation radical and dication. Examination of these various results in the light of theoretical calculations shows that in addition to a local control of bond length alternation, and hence of the HOMO–LUMO gap, the fixation of covalent bridges at selected positions of the π‐conjugated system limits the deformation of the π‐conjugated structure upon oxidation to the charged states.
Domino Reactions of 1,3‐Bis‐Silyl Enol Ethers with Benzopyrylium Triflates: Efficient Synthesis of Fluorescent 6H‐Benzo[c]chromen‐6‐ones, Dibenzo[c,d]chromen‐6‐ones, and 2,3‐Dihydro‐1H‐4,6‐dioxachrysen‐5‐ones
Authors: Appel Bettina , Saleh Nehad N. R. , Langer Peter
Published: November 2005

The condensation of 1,3‐bis‐silyl enol ethers with benzopyrylium triflates, generated in situ by the reaction of chromones with Me3SiOTf, afforded functionalized 2,3‐dihydrobenzopyrans; treatment of the latter with NEt3 or BBr3 resulted in a domino retro‐Michael–aldol–lactonization reaction and the formation of a variety of 7‐hydroxy‐6H‐benzo[c]chromen‐6‐ones. The hydroxy group was functionalized by using Suzuki cross‐coupling reactions. The methodology reported was applied to the synthesis of the natural product autumnariol and a new fluorescence dye, which exhibits promising optical properties. 2,3‐Dihydro‐1H‐4,6‐dioxachrysen‐5‐ones were prepared by condensation of chromones with 1,3‐bis‐silyl enol ethers containing a remote chloride group, domino retro‐Michael–aldol–lactonization, and an intramolecular Williamson reaction.
Participation of Sodium in the Bonding of Anionic Networks: Synthesis, Structure, and Bonding of Na3MIn2 (M: Au, Ag).
Authors: Li Bin , Corbett John D.
Published: November 2005

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Structural and Magnetic Properties of Hexagonal Perovskites La1.2Sr2.7MO7.33 (M: Ru, Ir) Containing Peroxide Ions.
Authors: Goetzfried Thomas , Reller Armin , Ebbinghaus Stefan G.
Published: November 2005

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Structure of Partially Reduced Bismuth—Silicate Glasses: EXAFS and MD Study.
Authors: Witkowska Agnieszka , Rybicki Jaroslaw , Di Cicco Andrea
Published: November 2005

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Convenient Preparation and Full Characterization of a Synthetically Useful Salt of the Dithianitronium Cation, SNSSbF6, from Readily Available Starting Materials.
Authors: Cameron T. Stanley , Mailman Aaron , Passmore Jack , Shuvaev Konstantin V.
Published: November 2005

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Lewis Acid Adducts of [PCl2N]3.
Authors: Heston Amy J. , Panzner Matthew J. , Youngs Wiley J. , Tessier Claire A.
Published: November 2005

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A Mesoporous Germanium Oxide with Crystalline Pore Walls and Its Chiral Derivative.
Authors: Zou Xiaodong , Conradsson Tony , Klingstedt Miia , Dadachov Mike S. , O'Keeffe Michael
Published: November 2005

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Octahedral Hexahydroxo Rhenium Cluster Complexes [Re6Q8(OH)6]4‐ (Q: S, Se): Synthesis, Structure, and Properties.
Authors: Yarovoi Spartak S. , Mironov Yuri V. , Naumov Dmitry Y. , Gatilov Yuri V. , Kozlova Svetlana G. , Kim Sung‐Jin , Fedorov Vladimir E.
Published: November 2005

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Improvement of Fluorescence Characteristics of Coumarins: Syntheses and Fluorescence Properties of 6‐Methoxycoumarin and Benzocoumarin Derivatives as Novel Fluorophores Emitting in the Longer Wavelength Region and Their Application to Analytical Reagents.
Authors: Murata Chiyomi , Masuda Toshinobu , Kamochi Yasuko , Todoroki Kenichiro , Yoshida Hideyuki , Nohta Hitoshi , Yamaguchi Masatoshi , Takadate Akira
Published: November 2005

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Electrochemical Combinatorial Organic Syntheses Using Microflow Systems.
Authors: Suga Seiji , Okajima Masayuki , Fujiwara Kazuyuki , Yoshida Jun‐ichi
Published: November 2005

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Regio‐ and Stereochemical Aspects in Synthesis of 2‐Allyl Derivatives of Glycolic, Mandelic and Lactic Acids and Their Iodocyclizations to 3‐Hydroxy‐3,4‐dihydrofuran‐2(5H)‐ones.
Authors: Kaur Pervinder , Singh Palwinder , Kumar Subodh
Published: November 2005

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Catalyzed Asymmetric Aryl Transfer Reactions to Aldehydes with Boroxines as Aryl Source.
Authors: Wu Xiaoyu , Liu Xinyuan , Zhao Gang
Published: November 2005

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Synthesis and Chemical Reactivity of 3‐Oxo‐2‐arylhydrazono‐propanenitriles.
Authors: Abdallah Sanaa O. , Metwally Nadia H. , Anwar Hany F. , Elnagdi Mohamed H.
Published: November 2005

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Addition/Ring‐Opening Reaction of Organoboronic Acids to Cyclobutanones Catalyzed by Rhodium(I)/P(t‐Bu)3 Complex.
Authors: Matsuda Takanori , Makino Masaomi , Murakami Masahiro
Published: November 2005

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Identification of Carbonyl Ylides in Reactions of Isothiazole 1,1‐Dioxides with Rh(II)‐Carbenoids.
Authors: Nikolaev Vs. V. , Krylov I. S. , Schulze B. , Rodina L. L.
Published: November 2005

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Selective Reduction of Nitrocinnamoylfumagillols with α,β‐Unsaturated Ester Using Borohydride Exchange Resin (BER)‐Nickel Acetate.
Authors: Lee Hong Woo , Ahn Joong Bok , Lee Jung Hwa , Kang Sung Kwon , Ahn Soon Kil , Lee Sang Joon
Published: November 2005

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Highly Enantioselective Iridium‐Catalyzed Allylic Aminations with Anionic N‐Nucleophiles.
Authors: Weihofen Robert , Dahnz Axel , Tverskoy Olena , Helmchen Guenter
Published: November 2005

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Iron‐Catalyzed Silylcyanation of Aldehydes and Ketones with Silyl Cyanide Prepared from Silane and Acetonitrile.
Authors: Itazaki Masumi , Nakazawa Hiroshi
Published: November 2005

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Highly Regioselective Heck Reactions of Heteroaryl Halides with Electron‐Rich Olefins in Ionic Liquid.
Authors: Pei Wen , Mo Jun , Xiao Jianliang
Published: November 2005

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Fast and Regioselective Heck Couplings with N‐Acyl‐N‐vinylamine Derivatives.
Authors: Hansen Anders Lindhardt , Skrydstrup Troels
Published: November 2005

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Microwave‐Assisted Decarboxylation of Bicyclic 2‐Pyridone Scaffolds and Identification of Aβ‐Peptide Aggregation Inhibitors.
Authors: Aaberg Veronica , Norman Fredrik , Chorell Erik , Westermark Andreas , Olofsson Anders , Sauer‐Eriksson A. Elisabeth , Almquist Fredrik
Published: November 2005

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A Rapid and Efficient Procedure for Deprotection of 1,1‐Diacetates Catalyzed by Silica Sulfate.
Authors: Jin Tong‐Shou , Zhao Ying , Liu Li‐Bin , Li Tong‐Shuang
Published: November 2005

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Formal Alkyne Insertion into Alkoxycarbene Complexes: Simple Access to Enantiopure Group 6 Alkynyl(alkoxy)carbene Complexes.
Authors: Barluenga Jose , de la Rua Ramon Bernardo , de Saa Diana , Ballesteros Alfredo , Tomas Miguel
Published: November 2005

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A Prodrug System for Hydroxylamines Based on Esterase Catalysis.
Authors: Conejo‐Garcia Ana , Schofield Christopher J.
Published: November 2005

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Preparation of Methyl N‐Substituted Carbamates from Amides Through N‐Chloroamides.
Authors: Hiegel Gene A. , Hogenauer Tyrone J.
Published: November 2005

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Synthesis of Homoallylic Amines by Hydrozirconation—Imine Addition of Allenes.
Authors: Wipf Peter , Pierce Joshua G.
Published: November 2005

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Gallium‐Mediated Allyl Transfer from Bulky Homoallylic Alcohol to Aldehydes via Retro‐Allylation: Stereoselective Synthesis of Both erythro‐ and threo‐Homoallylic Alcohols.
Authors: Hayashi Sayuri , Hirano Koji , Yorimitsu Hideki , Oshima Koichiro
Published: November 2005

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Hyper‐ and Hypotensive Activity of o‐Alkylamino Derivatives of N‐Arylcarbamates.
Authors: Velikorodov A. V. , Tyurenkov I. N. , Timchenko M. V. , Perfilova V. N.
Published: November 2005

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Electrochemical Oxidation of Benzylic Amines into the Corresponding Imines in the Presence of Catalytic Amounts of KI.
Authors: Okimoto Mitsuhiro , Takahashi Yukio , Numata Kaori , Nagata Yuji , Sasaki Gaku
Published: November 2005

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Enantioselective α‐Arylation of Cyclohexanones with Diaryl Iodonium Salts: Application to the Synthesis of (‐)‐Epibatidine.
Authors: Aggarwal Varinder K. , Olofsson Berit
Published: November 2005

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Synthesis of Optically Active α‐Methylamino Acids and Amides Through Biocatalytic Kinetic Resolution of Amides.
Authors: Wang Mei‐Xiang , Liu Jun , Wang De‐Xian , Zheng Qi‐Yu
Published: November 2005

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A General Method for the Preparation of Perfluoroalkanesulfonyl Chlorides.
Authors: Scott Peter J. H. , Campbell Ian B. , Steel Patrick G.
Published: November 2005

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Ring Opening of 2‐(Bromomethyl)‐1‐sulfonylaziridines Towards 1,3‐Heteroatom Substituted 2‐Aminopropane Derivatives.
Authors: D'hooghe Matthias , Rottiers Mario , Kerkaert Inge , De Kimpe Norbert
Published: November 2005

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Site Directed Synthesis of Mono and Disubstituted SF5‐Polyfluoroalkyl Benzenes.
Authors: Winter R. W. , Dodean R. , Smith J. A. , Anilkumar R. , Burton D. J. , Gard G. L.
Published: November 2005

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A Reinvestigation of Modena′s Protocol for the Asymmetric Oxidation of Prochiral Sulfides.
Authors: Massa Antonio , Mazza Valeria , Scettri Arrigo
Published: November 2005

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Electrooxidative Conversion of Dibenzoylbenzene Dihydrazones into the Corresponding Bis‐Diazo Compounds and Bis‐Dimethyl Acetals.
Authors: Okimoto Mitsuhiro , Numata Kaori , Tomozawa Kenta , Shigemoto Takamasa , Hoshi Masayuki , Takahashi Yukio
Published: November 2005

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Efficient Synthesis of Chalcones by a Solid Base Catalyst.
Authors: Kantam M. Lakshmi , Prakash B. Veda , Reddy Ch. Venkat
Published: November 2005

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Application of Recoverable Nanosized Palladium(0) Catalyst in Sonogashira Reaction.
Authors: Li Pinhua , Wang Lei , Li Hongji
Published: November 2005

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Electrophilic Substitution in Aromatic and Heteroaromatic Substrates by Trichlorocyclopropenylium Tetrachloroaluminate.
Authors: Skornyakov Yu. V. , Lozinskaya N. A. , Proskurnina M. V. , Zefirov N. S.
Published: November 2005

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Design, Synthesis, and Evaluation of 2‐Phenoxy‐indan‐1‐one Derivatives as Acetylcholinesterase Inhibitors.
Authors: Sheng Rong , Lin Xiao , Li Jingya , Jiang Yanke , Shang Zhicai , Hu Yongzhou
Published: November 2005

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Polyoxovanadometalate‐Catalyzed Selective Epoxidation of Alkenes with Hydrogen Peroxide.
Authors: Nakagawa Yoshinao , Kamata Keigo , Kotani Miyuki , Yamaguchi Kazuya , Mizuno Noritaka
Published: November 2005

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Lewis Acid Catalyzed Asymmetric Radical Additions of Trialkylboranes to (1R,2S,5R)‐2‐ (1‐methyl‐1‐phenylethyl)‐5‐methylcyclohexyl‐2H‐azirine‐3‐carboxylate.
Authors: Risberg Erik , Fischer Andreas , Somfai Peter
Published: November 2005

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Efficient Synthesis of Novel γ‐Substituted γ‐Butenolides by Lewis Acid Catalyzed Addition of Metal Enolates of Active Methylene Compounds to Mucohalic Acids.
Authors: Zhang Ji , Sarma Koushik Das , Curran Timothy T. , Belmont Daniel T. , Davidson James G.
Published: November 2005

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A Novel Catalyst for the Selective Hydrogenation of Furfural to Furfuryl Alcohol.
Authors: Hao Xiang‐Ying , Zhou Wei , Wang Jun‐Wei , Zhang Yin‐Qing , Liu Shuangxi
Published: November 2005

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Synthesis, Characterization, and Intramolecular Diels—Alder Reaction Tandem Dehydroaromatization of a Diene‐diyne.
Authors: Liu Shu‐Zhi , Tang Guang‐Shi , Wang Jing , Li Xue‐Hua
Published: November 2005

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Synthesis of 2‐Azaspiro[4.4]nonan‐1‐ones via Phosphine‐Catalyzed [3 + 2]‐Cycloadditions.
Authors: Yong Sarah R. , Williams Morwenna C. , Pyne Stephen G. , Ung Alison T. , Skelton Brian W. , White Allan H. , Turner Peter
Published: November 2005

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