bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metabolic Engineering for Microbial Production and Applications of Copolyesters Consisting of 3‐Hydroxybutyrate and Medium‐Chain‐Length 3‐Hydroxyalkanoates
Authors: Zou Xiang Hui , Chen Guo‐Qiang 
Published: February 2007

AbstractPoly(hydroxyalkanoate)s (PHAs) are a class of microbially synthesized polyesters that combine biological properties, such as biocompatibility and biodegradability, and non‐bioproperties such as thermoprocessability, piezoelectricity, and nonlinear optical activity. PHA monomer structures and their contents strongly affect the PHA properties. Using metabolic engineering approaches, PHA structures and contents can be manipulated to achieve controllable monomer and PHA cellular contents. This paper focuses on metabolic engineering methods to produce PHA consisting of 3‐hydroxybutyrate (3HB) and medium‐chain‐length 3‐hydroxyalkanoates (3HA) in recombinant microbial systems. This type of copolyester has mechanical and thermal properties similar to conventional plastics such as poly(propylene) and poly(ethylene terephthalate) (PET). In addition, pathways containing engineered PHA synthases have proven to be useful for enhanced PHA production with adjustable PHA monomers and contents. The applications of PHA as implant biomaterials are briefly discussed here. In the very near term, metabolic engineering will help solve many problems in promoting PHA as a new type of plastic material for many applications.magnified image
Construction of pha‐Operon‐Defined Knockout Mutants of Pseudomonas putida KT2442 and their Applications in Poly(hydroxyalkanoate) Production
Authors: Ouyang Shao‐Ping , Liu Qian , Fang Lei , Chen Guo‐Qiang 
Published: February 2007

AbstractPseudomonas putida KT2442 could accumulate medium‐chain‐length poly(hydroxyalkanoate)s (PHA) consisting of 3‐hydroxyhexanoate, 3‐hydroxyoctanoate, 3‐hydroxydecanoate, and 3‐hydroxydodecanoate from a wide range of carbon sources. In this study, the PHA synthase pha operon (phaC1‐phaZ‐phaC2) was knocked out and the vgb gene encoding vitreoscilla hemoglobin protein (VHb), which could enhance oxygen uptake rate especially at low oxygen concentration, was integrated into the P. putida KT2442 genome to replace the deleted fragment. The resulting mutant P. putida KTOY01 or gene‐replaced mutant KTOY02 was used as the host to study PHA synthase properties and PHA production. Different PHA polymerase (PhaC) genes, phaCRe from Rastonia eutropha H16, phaCAc from Aeromonas cavie, and phaC2Ps from Pseudomonas stutzeri 1317, were expressed in the mutant strains to test the PhaC enzyme substrate specificity. The result showed P. putida KTOY01 or KTOY02 could provide not only mcl PHA monomers but also 3‐hydroxybutyrate from fatty acids, which may allow the production of copolyesters poly(3HB‐co‐mcl 3HA). Plasmid pCJY10 containing phaC2Ps, phbA, and phbB genes encoding PHA polymerase, β‐ketothiolase, and acetoacetyl‐CoA reductase, respectively, were transformed into P. putida KTOY01 and KTOY02. Shake‐flask culture showed P. putida KTOY01 or KTOY02 (pCJY10) could accumulate poly(3HB‐co‐mcl 3HA) from glucose. The above result showed pha operon knockout mutant of P. putida KT2442 was a very useful host of great potential not only for studying PhaC synthase, but also for microbial production of copolyesters poly(3HB‐co‐mcl 3HA), which is very difficult to obtain.magnified image
TiO2 Sphere‐Tube‐Fiber Transition Induced by Oligovaline Concentration Variation
Authors: Mantion Alexandre , Taubert Andreas 
Published: February 2007

AbstractL‐Valine‐based oligopeptides with the general structure Z‐(L‐Val)n‐OMe or OH (n = 1–4) form stable organogels in a variety of solvents, including the inorganic liquid tetraethylorthosilicate. The acid form Z‐(L‐Val)n‐OH is a less efficient gelator than the methyl ester, but forms stable organogels in aromatic solvents and di‐ and trichloromethane. In all cases the peptides form micrometer long helical fibers with a β‐sheet structure. IR and X‐ray diffraction show that the peptides have closely related structures in the crystalline state and the fibers in the organogels. The gels are efficient templates for the fabrication of complex titania architectures on a (sub)micron length scale: at low peptide concentrations titania spheres form and at higher concentrations one‐dimensional shapes like hollow titania tubes or titania fibers are observed. The tubes are stable towards calcination whereas the fibers (partially) transform into spherical or even bulk particles.magnified image
Increase of Fluorescence Anisotropy Upon Self‐Assembly in Headgroup‐Labeled Surfactants
Authors: Kastantin Mark , Ananthanarayanan Badriprasad , Lin Brian , Ressl Jan , Black Matthew , Tirrell Matthew 
Published: February 2007

AbstractThe change in fluorescence anisotropy upon micellization in headgroup‐labeled surfactants is investigated. After eliminating the likelihood of depolarizing RET, anisotropy is shown to increase upon self‐assembly due to increased rotational correlation times of the fluorophore. This is shown using two surfactant‐fluorophore systems. Anisotropy in NBD‐labeled phospholipids is studied both in chloroform (unaggregated) and in water (unilamellar vesicles), while in tryptophan‐containing peptide‐amphiphiles, the variation of anisotropy with concentration leads to a reasonable measurement of CAC. Anisotropy increase is shown to be largely the product of increased rotational correlation times for the fluorophore, relative to its τ. These results serve as a basis for future work that measures the amount of depolarizing energy transfer, characterizing distances between similar fluorescent headgroups on mixed micelles.magnified image
Modeling of Bovine Type‐I Collagen Fibrils: Interaction with Pickling and Retanning Agents
Authors: Bulo Rosa E. , Siggel Lorenz , Molnar Ferenc , Weiss Horst 
Published: February 2007

AbstractBovine Type I collagen was investigated, building on a large scale computer model of a collagen fibril in water, and focusing on two stages of the leather manufacturing process. The effects of different salts (NaCl, CaCl2, and Na2SO4) on the swelling behavior of collagen at low pH (the pickling process) were studied. The salts suppress the swelling of the fibrils at low pH and we find specific stabilizing influences for CaCl2 and Na2SO4, due to weak Ca2+/Cl− and strong SO/lysine/arginine interactions, respectively. Using state‐of‐the‐art sampling techniques, such as the metadynamics algorithm, to allow an efficient exploration of configuration space, we were able to investigate the effect of polyacrylate and poly(methyl acrylate) – two polymeric retanning agents – on the fibril. Both polymers interact with the ammonium groups on the surface, but polyacrylate shows significantly stronger interactions. We suggest that it is this stronger interaction that contributes to the reduced suitability of PAA as a tanning agent.magnified image
Sulfated Glycopolymer Thin Films—Preparation, Characterization, and Biological Activity
Authors: Grombe Ringo , Gouzy Marie F. , Maitz Manfred F. , Freundenberg Uwe , Zschoche Stefan , Simon Frank , Pompe Tilo , Sperling Claudia , Werner Carsten 
Published: February 2007

AbstractThe impact of heparinoid characteristics on model surfaces obtained from immobilization of sole sulfate groups as well as sulfated glycosides, sulfated cellulose, and definite heparin has been investigated. The obtained layers were physico‐chemically characterized regarding film thickness, chemical composition, wettability, and surface morphology. Antithrombin adsorption, studied by fluorescence labeling, revealed a strong dependence on the presence of glycosidic structures and on the molecular weight of the grafted saccharide. On contact with whole blood, the coatings resulted in a diminished plasmatic and cellular coagulation in vitro, which did not reflect well the antithrombin binding. Therefore, more complex activating pathways are discussed.magnified image
A Flexible Approach to the Preparation of Polymer Scaffolds for Tissue Engineering
Authors: Borgaonkar Poonam , Sharma Sachin , Chen Ming , Bhowmick Sankha , Schmidt Daniel F. 
Published: February 2007

AbstractPorous polyester thermoset xerogels have been produced via sol–gel chemistry as a first step in the development of sol–gel derived tissue engineering scaffolds templated by replica molding and/or salt leaching. The pore structure of these untemplated thermosets is tunable and can be altered independent of or in tandem with alterations in composition. Cytocompatibility studies on these xerogels imply the effects of both pore size and materials chemistry, with fully aliphatic polyesters with large pore structures allowing the growth of mammalian cells. To the best of our knowledge, this represents the first report examining the preparation and potential of sol–gel derived porous polymer xerogels as tissue engineering scaffolds.magnified image
Design Parameters and Current Fabrication Approaches for Developing Bioinspired Dry Adhesives
Authors: del Campo Aránzazu , Arzt Eduard 
Published: February 2007

AbstractThe attachment pads of some beetles, spiders, flies, and geckos are covered by a dense array of long hairs with characteristic geometries. This curious surface topography allows them to firmly attach to and easily release from almost any kind of surface. In a technological context, such reversible adhesion could enable robots to walk along walls or ceilings, or lead to new medical devices, disposable plasters, reusable adhesive tapes, etc. Artificial fibrillar surfaces mimicking nature's design have been recently fabricated, but their adhesion performance is still far from that of natural systems. This review describes the progress in this field during the last few years and discusses the issues pending for the future.magnified image
Synthesis of Magnetite Nanoparticles for Bio‐ and Nanotechnology: Genetic Engineering and Biomimetics of Bacterial Magnetosomes
Authors: Lang Claus , Schüler Dirk , Faivre Damien 
Published: February 2007

AbstractMagnetotactic bacteria (MTB) have the ability to navigate along the Earth's magnetic field. This so‐called magnetotaxis is a result of the presence of magnetosomes, organelles which comprise nanometer‐sized intracellular crystals of magnetite (Fe3O4) enveloped by a membrane. Because of their unique characteristics, magnetosomes have a high potential for nano‐ and biotechnological applications, which require a specifically designed particle surface. The functionalization of magnetosomes is possible either by chemical modification of purified particles or by genetic engineering of magnetosome membrane proteins. The second approach is potentially superior to chemical approaches as a large variety of biological functions such as protein tags, fluorophores, and enzymes may be directly incorporated in a site‐specific manner during magnetosome biomineralization. An alternative to the bacterial production of magnetosomes are biomimetic approaches, which aim to mimic the bacterial biomineralization pathway in vitro. In MTB a number of magnetosome proteins with putative functions in the biomineralization of the nanoparticles have been identified by genetic and biochemical approaches. The initial results obtained by several groups indicate that some of these proteins have an impact on nanomagnetite properties in vitro. In this article the key features of magnetosomes are discussed, an overview of their potential applications are given, and different strategies are proposed for the functionalization of magnetosome particles and for the biomimetism of their biomineralization pathway.magnified image
Folate and colorectal cancer: An evidence‐based critical review
Authors: Kim Young‐In 
Published: February 2007

AbstractCurrently available evidence from epidemiologic, animal, and intervention studies does not unequivocally support the role of folate, a water‐soluble B vitamin and important cofactor in one‐carbon transfer, in the development and progression of colorectal cancer (CRC). However, when the portfolio of evidence from these studies is analyzed critically, the overall conclusion supports the inverse association between folate status and CRC risk. It is becoming increasingly evident that folate possesses dual modulatory effects on colorectal carcinogenesis depending on the timing and dose of folate intervention. Folate deficiency has an inhibitory effect whereas folate supplementation has a promoting effect on the progression of established colorectal neoplasms. In contrast, folate deficiency in normal colorectal mucosa appears to predispose it to neoplastic transformation, and modest levels of folic acid supplementation suppress, whereas supraphysiologic supplemental doses enhance, the development of cancer in normal colorectal mucosa. Several potential mechanisms relating to the disruption of one‐carbon transfer reactions exist to support the dual modulatory role of folate in colorectal carcinogenesis. Based on the lack of compelling supportive evidence and on the potential tumor‐promoting effect, routine folic acid supplementation should not be recommended as a chemopreventive measure against CRC at present.
Diaphragmatic paralysis following minor cervical trauma
Authors: Merino‐Ramírez Miguel A. , Juan Gustavo , Ramón Mercedes , Cortijo Julio , Morcillo Esteban J. 
Published: February 2007

AbstractTwo asthmatic patients developed unilateral diaphragmatic paralysis from phrenic nerve injury, in one case following cervical chiropractic manipulation and in the other after a motorcycle accident. Both presented with increased dyspnea and orthopnea. Diagnosis, severity, and level of the lesion were established by neurophysiological methods, which are preferred to chest radiography and diaphragmatic ultrasonography. In spite of only partial electrophysiological recovery of the nerve, both patients were asymptomatic 1 year later. Muscle Nerve, 2007
Novel SOD1 N86K mutation is associated with a severe phenotype in familial ALS
Authors: Beck Marcus , Sendtner Michael , Toyka Klaus V. 
Published: February 2007

AbstractFamilial amyotrophic lateral sclerosis (ALS) is frequently associated with mutations in the SOD1 gene. We identified a rapidly progressive disease in a patient with an inherited ALS. The identified heterozygous T>A exchange in position 1067 in the SOD1 gene results in an amino acid substitution of lysine for asparagine at position 86 (N86K) of the SOD1 protein. The family history suggested that this autosomal dominantly inherited mutation may be associated with rapidly progressive disease. Muscle Nerve, 2007
Diagnostic ultrasound for nerve transection
Authors: Cartwright Michael S. , Chloros George D. , Walker Francis O. , Wiesler Ethan R. , Campbell William W. 
Published: February 2007

AbstractThe current approach for localizing and assessing the severity of traumatic peripheral nerve injuries involves clinical evaluation and electrodiagnostic studies. However, the ability of this approach to determine the extent of nerve damage within the first 6 weeks after trauma is limited. This is problematic because outcome is improved with early surgical intervention after complete nerve transection. This led us to explore alternative techniques, such as imaging, for assessing peripheral nerve injuries. Twelve fresh cadavers were obtained and after inspection 20 arms were deemed suitable for inclusion in the study. Random sites were transected in median, ulnar, and radial nerves, and sham skin incisions were performed throughout the arm. These nerves were then systematically scanned by an ultrasonographer blinded to the nerve transection sites, who made a final decision as to whether the nerve was transected. High‐resolution ultrasound was able to identify transected nerves in the upper extremity with 89% sensitivity and 95% specificity in fresh cadavers. This proof‐of‐concept study shows that ultrasound can accurately identify nerve transection, which should lead to further ultrasound studies in patients with traumatic peripheral nerve injuries. Muscle Nerve, 2007
Elevated brain scyllo‐inositol concentrations in patients with Alzheimer's disease
Authors: Griffith H. Randall , den Hollander Jan A. , Stewart Chris C. , Evanochko William T. , Buchthal Steven D. , Harrell Lindy E. , Zamrini Edward Y. , Brockington John C. , Marson Daniel C. 
Published: February 2007

Abstractin vivo 1H MRS reveals reduced N‐acetylaspartate (NAA) and elevated myo‐inositol (mI) in patients with mild Alzheimer's disease (AD) and patients with amnestic mild cognitive impairment (MCI). We are unaware of studies that have documented abnormal scyllo‐inositol (sI) levels in patients with AD or patients with MCI, although a previous MRS study in older adults has indicated that sI is a peak of interest to measure in AD. Fifteen patients with mild AD, 26 patients with amnestic MCI, and 19 healthy older adults were recruited to this study. All underwent 1H MRS of the posterior cingulate gyrus of the brain using a 3 T MRI scanner. Increases in the sI/creatine (Cr) ratio were observed in patients with mild AD (P < 0.05). The mI/Cr ratio was raised in patients with mild AD (P < 0.01) and MCI (P < 0.05). Reduced NAA/Cr was detected in patients with mild AD (P < 0.05). The sI/Cr ratio correlated negatively (r = −0.60, P < 0.05) with a measure of clock drawing in patients with mild AD, indicating that impaired cognitive ability in AD is associated with higher concentrations of sI/Cr. In vivo measurement of sI/Cr in the posterior cingulate gyrus of patients with mild AD revealed increases compared with cognitively healthy older adults. Further research on the mechanisms of sI increase in AD is needed. Future studies on the longitudinal course of sI/Cr in MCI and AD appear warranted. Copyright © 2007 John Wiley & Sons, Ltd.
Gadobenate dimeglumine as a contrast agent for MRI of the mouse liver
Authors: Inoue Yusuke , Yoshikawa Kohki , Nomura Yukihiro , Izawa Kiyoko , Shimada Morio , Tojo Arinobu , Ohtomo Kuni 
Published: February 2007

AbstractWe investigated the characteristics and utility of gadobenate dimeglumine (Gd‐BOPTA) for MRI of the mouse liver. Mice were imaged under isoflurane anesthesia using a T1‐weighted, three‐dimensional fast low‐angle shot (3D FLASH) sequence before and after intravenous or subcutaneous injection of Gd‐BOPTA, and the time course of the contrast effect was examined. The appropriate dose for subcutaneous injection was determined visually, and the inter‐ and intra‐observer reproducibilities in liver volumetry were evaluated with and without contrast injection. When mice were imaged sequentially before and after Gd‐BOPTA injection and isoflurane anesthesia was maintained throughout the experiment, a long‐lasting contrast effect was noted in the liver. Subcutaneous injection caused delayed, but favorable, enhancement. Washout from the liver was definitely accelerated in conscious mice in comparison with anesthetized mice. Visual evaluation indicated that a dose of 0.1 mmol/kg was appropriate for clear delineation of the entire liver margin, and the application of Gd‐BOPTA significantly improved the inter‐ and intra‐observer reproducibilities of liver volumetry. In conclusion, the intravenous or subcutaneous injection of Gd‐BOPTA has a favorable contrast effect for the mouse liver, resulting in clear visualization of the liver border and improved reproducibility of liver volumetry. The possible influence of anesthesia on the pharmacokinetics of a contrast agent should be considered in determining the optimal scan timing. Copyright © 2007 John Wiley & Sons, Ltd.
Least‐squares solutions of matrix inverse problem for bi‐symmetric matrices with a submatrix constraint
Authors: Liao An‐ping , Lei Yuan 
Published: February 2007

AbstractAn n × n real matrix A = (aij)n × n is called bi‐symmetric matrix if A is both symmetric and per‐symmetric, that is, aij = aji and aij = an+1−1,n+1−i (i, j = 1, 2,..., n). This paper is mainly concerned with finding the least‐squares bi‐symmetric solutions of matrix inverse problem AX = B with a submatrix constraint, where X and B are given matrices of suitable sizes. Moreover, in the corresponding solution set, the analytical expression of the optimal approximation solution to a given matrix A* is derived. A direct method for finding the optimal approximation solution is described in detail, and three numerical examples are provided to show the validity of our algorithm. Copyright © 2007 John Wiley & Sons, Ltd.
Remarks on the efficiency of POD for model reduction in non‐linear dynamics of continuous elastic systems
Authors: Sampaio Rubens , Soize Christian 
Published: February 2007

AbstractThe first objective of this paper is to analyse the efficiency of the reduced models constructed using the proper orthogonal decomposition (POD)‐basis and the LIN‐basis in non‐linear dynamics for continuous elastic systems. The POD‐basis is the Hilbertian basis constructed with the POD method while the LIN‐basis is the Hilbertian basis derived from the generalized continuous eigenvalue problem associated with the underlying conservative part of the continuous elastic system and usually called the eigenmodes of vibration. The efficiency of the POD‐basis or the LIN‐basis is related to the rate of convergence in the frequency domain of the solution constructed with the reduced model with respect to its dimension. A basis will be more efficient than another if the reduced‐order solution of the Galerkin projection converges to the solution of the dynamical system more rapidly than the reduced‐order solution of the other.As a second objective of this paper, we present the usual results concerning the POD method using a continuous formulation, with respect to both time and space variables, and then deriving the numerical approximations. Such a presentation allows convergence discussions to be treated.Six examples in non‐linear elastodynamics problems are presented in order to analyse the efficiency of the POD‐basis and the LIN‐basis. It is concluded that the POD‐basis is not more efficient than the LIN‐basis for the examples treated in non‐linear elastodynamics. Copyright © 2007 John Wiley & Sons, Ltd.
A new plate bending element based on orthogonal polynomials expansion of the curvature field
Authors: Pitacco I. 
Published: February 2007

AbstractA new approach to derive finite elements for the thin plate model is presented. The proposed method approximates compatible Kirchhoff formulations by means of orthogonal polynomials expansion of the curvature field depending only on the element boundary traces. With respect to the compatible formulation the proposed method produces elements that beneficially underestimate the deformation energy. A simple triangular element is developed and investigated from both the theoretical and the numerical point of view and numerically compared with other two well‐known elements. Copyright © 2007 John Wiley & Sons, Ltd.
Evolutionary optimization for passive gamma tomography reconstruction of circular inclusions in nuclear waste vaults
Authors: Mera N. S. 
Published: February 2007

AbstractIn this study we investigate numerically the possibility of reconstructing the interior details of a nuclear waste vault using photon flux measurements. The passive gamma ray tomography method is employed in order to simultaneously retrieve the intensity and the location of strongly radioactive components. After reformulating the problem as an optimization problem the objective functional obtained is found to have a multi‐modal non‐smooth structure. Therefore, evolutionary algorithms are used in order to minimize the objective functional in order to determine the radioactive components. Circular inclusions are considered and detailed numerical results are presented for both exact and noisy data. Copyright © 2007 John Wiley & Sons, Ltd.