bluuebunny/crossref_metadata_2025 huggingface dataset:
Printed tri‐band monopole antenna structures for wireless applications
Authors: Gupta R. K.
Published: April 2009

This article proposes a novel tri‐band printed monopole antenna structure for wireless applications in GSM, DCS, and wireless local area network applications, IEEE 802.11 industrial, scientific, and medical (ISM) band. The proposed antenna consists of a rectangular patch monopole printed antenna in which a slot is cut, and dual‐band E‐shape patch is placed. The three arms in monopole antenna generates three resonate frequencies to cover 890–960 MHz GSM band, 1710–1880 MHz DCS band, and 2.4–2.5 GHz ISM band. Slots are removed to coincide with central arm to obtain the second structure. Central arm of antenna resonate at GSM, whereas the other two side arms resonate at DCS and ISM band; therefore three bands can be optimized easily. The proposed antennas can easily be fed by using a 50 Ω probe feed. The simulated VSWR is <2 over 890–960 MHz, 1710–1880 MHz, and 2.4–2.5 GHz The radiation patterns indicate the suitability of these antennas for wireless applications. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1781–1785, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24440
A 0.18 μm 3.1–4.8 GHz CMOS wideband single to differential LNA for UWB system
Authors: Jeong Moo I. , Lee Jung S. , Myung No C. , Kim Jong M. , Lee Chang S.
Published: April 2009

We have proposed a 3.1–4.8 GHz CMOS wideband single to differential low noise amplifier (LNA) for ultra wideband system. The LNA is fabricated with the 0.18 μm 1P6M standard CMOS process. Measurement of the CMOS LNA was performed using RF probe station. From 3.1 to 4.8 GHz, the wideband LNA exhibits a noise figure of 4.8–5.1 dB, a gain of 12.6–15.3 dB, and an input return loss higher than 10 dB. The input IP3 (IIP3) at 4.1 GHz is −19 dBm, and consumes 19.1 mW of power. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1778–1781, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24441
Efficient method for resonant frequency computation of rectangular dielectric resonator antennas
Authors: Gürel Çiğdem Seçkin , Coşar Hayriye
Published: April 2009

In this study, a new and simple formulation is presented for a rectangular dielectric resonator antenna and called as efficient dielectric waveguide model. The results obtained are compared with that of the previous studies and experimental values. It is shown that considerable improvement is achieved over the previous theories within very small percentage errors for almost all cases. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1706–1708, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24442
Application of “bull's eye” corrugated grooves integrated with artificially soft surfaces structure in the patch antenna to improve radiation performance
Authors: Huang Cheng , Zhao Zeyu , Luo Xiangang
Published: April 2009

In this article, a Bull's eye corrugated structure integrated with artificially soft surfaces structure is proposed as the ground plane in the patch antenna. This structure is based on the modulation of surface wave by the bull's eye corrugated structure and the suppression of surplus surface wave at grounded edge by artificially soft surfaces structure. A numerical investigation for the patch antenna surrounded with combined corrugated grooves ground is presented using finite difference time domain method. The gain of the patch antenna is significantly improved by 12.3 dB, and half power beamwidth in the E and H‐plane are dramatically suppressed. The backward radiation is also reduced by 10 dB, which greatly enhances the Front to Backward (F/B) radiation ratio. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1676–1679, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24443
Controlled multiple resonances behavior of asymmetric L‐shaped CPW DGS
Authors: Jiang Hu
Published: April 2009

This article presents an asymmetric L‐shaped coplanar waveguide defected ground structure (DGS). Three asymmetry cases, the transverse, the vertical, and two‐dimensional asymmetries, have been studied under changing the certain dimension parameter. Controlled multiple resonance frequencies with different attenuation level can be observed, when the asymmetry degree is being adjusted. Characteristics of these asymmetric DGSs are modeled by multiple parallel RLC resonance circuits connected with T‐networks. This flexible multiple band‐rejections property is useful to suppress multiple harmonics selectively in small‐sized circuits. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1671–1676, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24444
Elimination of the dependency of the calibration plane and the sample thickness from complex permittivity measurements of thin materials
Authors: Hasar U. C. , Inan O. E.
Published: April 2009

In nonresonant broadband measurements, thin samples do not fill the entire sample holder (a waveguide or coaxial‐line section). In this circumstance, the measured scattering parameters have to be transformed from the calibration plane to the sample end surfaces. Furthermore, it is always attractive to measure the complex permittivity of materials with no prior information of their thickness. This article proposes a simple but powerful method to eliminate the dependency of both the calibration plane and the sample thickness on permittivity measurements of thin nondispersive materials. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1642–1646, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24445
Printed double‐T monopole antennas for triband applications
Authors: Kshetrimayum Rakhesh Singh
Published: April 2009

In this article, we have investigated printed double‐T monopole antennas for triband applications. A close form formula for calculating the antenna resonance frequency is reported. Such printed monopole antennas are compact, less fragile, planar, and easy for design and fabrication. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1640–1642, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24446
SMT pad using a coaxial line structure for LTCC SoP applications
Authors: Lee Young Chul
Published: April 2009

In this work, a SMT (surface mount type) pad using a coaxial‐line‐like vertical via transition is presented for LTCC SoP (system‐on‐package) applications. Because the outer conductors of the coaxial‐like transition overlaps with the CPW line on the PCB board, the overlap part is cut off to eliminate the their interaction or crosstalk. For reduction of radiation and return path, a cap on the top layer of the LTCC substrate is designed. The designed SMT pad was fabricated using the standard LTCC process. The measuredS11andS21are −14 and 0.9 dB, respectively, at 15 GHz. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1769–1772, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24447
Phenomenological and electrical modelization of microcoaxial probes for SNMM
Authors: Castagné M. , Falgayrettes P. , Nativel L. , Marchetti M.
Published: April 2009

We are presenting an unusual set microcoaxial for RF field, associated with a submicron position sensor. The near field is determined experimentally and calculated theoretically with comparative experiments. The measurements are interpreted as an electric model of the probe for applications on the submicron components. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1765–1769, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24448
Schemes of microwave hyperthermia by using flat left‐handed material lenses
Authors: Wang Gang , Gong Yu , Wang Hongjin
Published: April 2009

Effective microwave hyperthermia of cancer is proposed by using slightly lossy flat left‐handed material lenses. High‐resolution focusing of microwave without any auxiliary foci can be achieved in tissue by jointly adjusting the sources behind the flat lenses. Two‐dimensional numerical simulations demonstrate that, for tumor of diameter of 0.6 cm immersed in lossy breast tissue, microwave power can be effectively localized in tumor volume and temperature in tumor may be raised to ∼43.5°C, while keeps below 42°C in the surrounding normal tissue as required in hyperthermia treatment. The proposed Γ‐shaped two‐lens system is proved to an efficient scheme for microwave hyperthermia. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1738–1743, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24449
Enhanced patch antenna performances using dendritic structure metamaterials
Authors: Liu Yahong , Zhao Xiaopeng
Published: April 2009

The patch antenna with dendritic structure metamaterials is proposed and the performance of the antenna is investigated numerically and experimentally. Dendritic structure metamaterials can possess negative permeability due to the resonance of the magnetic polarizability within a band where the electromagnetic wave cannot propagate. The dendritic structure has the merit of fairly high‐level of symmetry and can exhibit excellent isotropy. When the frequency of the antenna lies in the resonant bandgap, the performance of the antenna can be enhanced due to the fantastic electromagnetic characteristic of the dendritic structure. The study results show that compared with the conventional patch antenna without dendritic structure metamaterials, the half‐power beamwidth (HPBW) of the proposed antenna becomes more convergent and the gain is higher. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1732–1738, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24450
Short‐ended coaxial cylinder probe measuring bulk dielectric constant using TDR
Authors: Park Young‐Jin
Published: April 2009

A simple short‐ended coaxial cylinder probe measuring bulk dielectric constant of porous media using time domain reflectometry (TDR) is presented. For the TDR application, reflection behavior of the probe is analyzed in time domain. For time domain analysis, first, input impedance of the probe is calculated using transmission line theory and impedance of each mode propagating in the probe. Second, reflection coefficient is obtained using the input impedance. For verification, a prototype is designed using analysis results and tested for the case of sand. The analysis results are in a good agreement with numerical simulations and measurements. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1638–1640, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24451
Wideband circularly polarized microstrip antenna using broadband quadrature power splitter based on metamaterial transmission line
Authors: Zhao Gang , Jiao Yong‐Chang , Yang Xi , Lin Chen , Song Yue
Published: April 2009

A new design of a wideband circularly polarized microstrip patch antenna with dual capacitively coupled feeds is presented in this article. Axial ratio bandwidth enhancement is achieved for microstrip patch antenna using a broadband quadrature power splitter (QPS). The microstrip and metamaterial transmission lines are connected to two output ports of a Wilkinson power divider as the QPS to achieve broadband quadrature phase difference. The antenna has been investigated numerically and experimentally. Measured results show that the antenna has an impedance bandwidth of 72.6% and a 3‐dB axial ratio bandwidth of 46.9%. The 3‐dB gain bandwidth is about 46.3%, with the peak gain level at 7.0 dBi. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1790–1793, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24452
Characteristics estimation for high‐impedance surfaces based ultrathin radar absorber
Authors: Li You‐Quan , Fu Yun‐Qin , Yuan Nai‐Chang
Published: April 2009

In this article, an ultrathin Radar Absorbing Material (RAM) based on high‐impedance surfaces (HIS) has been investigated. Simple analytical formulas for the input impedance of HIS RAM are present and the equivalent model of lumped resistor is given to achieve better absorbing performance. From the simulated results, it is seen that the absorbing band of HIS RAM is decided by the reflection phase of HIS in the range ±60°, the measured absorbing frequency band moved toward lower‐frequency than the simulated results, which attribute to the parasitic capacitance introduced by lumped resistors. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1775–1778, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24453
Effect of surface resistor loading on high‐impedance surface radar absorber return loss and bandwidth
Authors: Munir A. , Fusco V.
Published: April 2009

A simple method for the selection of the appropriate choice of surface‐mounted loading resistor required for a thin radar absorber based on a high‐impedance surface (HIS) principle is demonstrated. The absorber consists of a HIS, (artificial magnetic ground plane), thickness 0.03λ0 surface‐loaded resistive‐elements interconnecting a textured surface of square patches. The properties of absorber are characterized under normal incident using a parallel plate waveguide measurement technique over the operating frequency range of 2.6–3.95 GHz. We show that for this arrangement return loss and bandwidth are insensitive to ±2% tolerance variations in surface resistor values about the value predicted using the method elaborated in this letter, and that better than −28 dB at 3.125 GHz reflection loss can be obtained with an effective working bandwidth of up to 11% at −10 dB reflection loss. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1773–1775, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24454
Ultrawideband bandpass filter with a controllable notched band
Authors: Gao Shanshan , Xiao Shaoqiu , Wang Bing‐Zhong
Published: April 2009

A compact ultrawideband (UWB) bandpass filter with a controllable notched band within the UWB passband is proposed on the basis of a stub‐loaded modified stepped impedance resonator (SIR) and two identical interdigital feed‐lines. In the design, the modified SIR and the interdigital feed‐lines can work together properly to make up the desired UWB passband. The stubs loaded at each side of the modified SIR can generate a desired notched band within the UWB passband to avoid the interference from wireless local‐area network. There are good agreements between the simulated and measured results. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1745–1748, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24455
Millimeter‐wave dual‐mode filter using circular high‐order mode cavities
Authors: Dong Yuandan , Hong Wei , Tang Hongjun , Wu Ke
Published: April 2009

A novel dual‐mode filter using circular high‐order mode cavities based on substrate integrated waveguide technology is presented. Its dual‐mode character and transmission responses are carefully investigated. Filters in both Ka‐ and Q‐band using two congruent cavities in folded configuration are designed, fabricated with standard PCB process, and measured. Small insertion loss, flat group delay, and good tolerance are observed, which is consistent with the simulation. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1743–1745, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24456
A wideband quasi‐millimeter‐wave bandpass filter using dual‐mode resonator with 5/4 wavelength folded stubs
Authors: Cai Peng , Ma Zhewang , Kanzaki Hitoshi
Published: April 2009

A novel wideband quasi‐millimeter‐wave filter with good in‐band and out‐band performances is proposed in this article. A dual‐mode square ring resonator loaded with two5λ0/4 (λ0is the center wavelength of the filter)folded stubs is introduced to realize a3 dBpassband bandwidth of about15%. Because of the transmission zeros produced by the dual‐mode ring resonator in the stopbands, the proposed filter exhibits sharp attenuations near the passband. On the other hand, a parallel‐coupled two‐mode resonator is introduced and integrated with the dual‐mode ring resonator to get a further improvement of the out‐band performance with wide stopbands. The fabricated filter has an insertion loss better than2 dBin the passband and rejections greater than20 dBat most of the frequencies in the stopbands. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1708–1711, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24457
Editorial
Authors: Chang Kai
Published: April 2009

© 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51:1617, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24458
Diffusion tensor imaging in a rat model of Parkinson's disease after lesioning of the nigrostriatal tract
Authors: Van Camp Nadja , Blockx Ines , Verhoye Marleen , Casteels Cindy , Coun Frea , Leemans Alexander , Sijbers Jan , Baekelandt Veerle , Van Laere Koen , Van der Linden Annemie
Published: April 2009

Parkinson's disease (PD) is characterised by degeneration of the nigrostrial connection causing dramatic changes in the dopaminergic pathway underlying clinical pathology. Till now, no MRI tools were available to follow up any specific PD‐related neurodegeneration. However, recently, diffusion tensor imaging (DTI) has received considerable attention as a new and potential in vivo diagnostic tool for various neurodegenerative diseases. To assess this in PD, we performed DTI in the acute 6‐hydroxydopamine (6‐OHDA) rat model of PD to evaluate diffusion properties in the degenerating nigrostriatal pathway and its connecting structures. Injection of a neurotoxin in the striatum causes retrograde neurodegeneration of the nigrostriatal tract, and selective degeneration of nigral neurons. The advantage of this model is that the lesion size is well controllable by the injected dose of the toxin. The degree of functional impairment was evaluated in vivo using the amphetamine rotation test and µPET imaging of the dopamine transporter (DAT). Despite a nearly complete lesion of the nigrostriatal tract, DTI changes were limited to the ipsilateral substantia nigra (SN). In this study we demonstrate, using voxel‐based statistics (VBS), an increase in fractional anisotropy (FA), whereas all eigenvalues were significantly decreased. VBS enabled us to visualise neurodegeneration of a cluster of neurons but failed to detect degeneration of more diffuse microstructures such as the nigrostriatal fibres or the dopaminergic endings in the striatum. VBS without a priori information proved to be better than manual segmentation of brain structures as it does not suffer from volume averaging and is not susceptible to erroneous segmentations of brain regions that show very little contrast on MRI images such as SN. Copyright © 2009 John Wiley & Sons, Ltd.
Assessment of 31P‐NMR analysis of phospholipid profiles for potential differential diagnosis of human cerebral tumors
Authors: Solivera Juan , Cerdán Sebastián , Pascual José María , Barrios Laura , Roda José María
Published: April 2009

We describe a novel protocol for the non‐histological diagnosis of human brain tumors in vitro combining high‐resolution 31P magnetic resonance spectroscopy (31P‐MRS) of their phospholipid profile and statistical multivariate analysis. Chloroform/methanol extracts from 40 biopsies of human intracranial tumors obtained during neurosurgical procedures were prepared and analyzed by high‐resolution 31P‐MRS. The samples were grouped in the following seven major classes: normal brain (n = 3), low‐grade astrocytomas (n = 4), high‐grade astrocytomas (n = 7), meningiomas (n = 9), schwannomas (n = 3), pituitary adenomas (n = 4), and metastatic tumors (n = 4). The phospholipid profile of every biopsy was determined by 31P‐NMR analysis of its chloroform/methanol extract and characterized by 19 variables including 10 individual phospholipid contributions and 9 phospholipid ratios. Most tumors depicted a decrease in phosphatidylethanolamine (PtdEtn) and phosphatidylserine (PtdSer), the former mainly in neuroepithelial neoplasms and the latter in metastases. An increase in phosphatidylcholine (PtdCho) and phosphatidylinositol (PtdIns) appeared predominantly in primary non‐neuroepithelial tumors. Linear discriminant analysis (LDA) revealed the optimal combination of variables that could classify each biopsy between every pair of classes. The resultant discriminant functions were used to calculate the probability of correct classifications for each individual biopsy within the seven classes considered. Multilateral analysis classified correctly 100% of the normal brain samples, 89% of the meningiomas, 75% of the metastases, and 57% of the high‐grade astrocytomas. The use of phospholipid profiles may complement appropriately previously proposed methods of intelligent diagnosis of human cerebral tumors. Copyright © 2009 John Wiley & Sons, Ltd.
Solution of the Riemann problem for irreversibly compressible media
Authors: Feldgun V. R. , Karinski Y. S. , Yankelevsky D. Z.
Published: April 2009

The Riemann problem for an irreversibly compressible medium has been solved. This solution introduces the maximum medium density that is attained in the process of active loading. To close the system of equations an extra equation is required to describe the transfer of this parameter through the Eulerian mesh. The possible wave configurations have been analyzed and the corresponding equations for the evaluation of the contact pressure and velocity have been obtained. The existence and uniqueness of the solution have been proven. The technique of the Riemann problem's solution for the arbitrary Lagrange Euler mesh was developed. Examples of the Riemann problem solution for various wave configurations show that neglecting the bulk elastic plastic deformations yields significant errors in the results both quantitatively and qualitatively. Copyright © 2009 John Wiley & Sons, Ltd.
The importance of an internal marketing orientation in social services
Authors: Cano Cynthia Rodriguez , Sams Doreen
Published: April 2009

The current research takes an interdisciplinary approach to examine the role of emotions in the successful delivery of social services. Survey data collected from 533 frontline social service providers were subjected to regression analyses. Findings reveal that emotional intelligence mediates the relationship between emotional labor and job stress, which in‐turn impacts job performance. The findings suggest that an internal marketing orientation is needed to better match the organization's products (i.e., jobs) with its internal customers (employees), and in‐turn improve the quality (job performance) of its offerings to its external customers.

Copyright © 2009 John Wiley & Sons, Ltd.
Incorporating a class of constraints into the dynamics of optimal control problems
Authors: Graichen K. , Petit N.
Published: April 2009

A method is proposed to systematically transform a constrained optimal control problem (OCP) into an unconstrained OCP, which can be treated in the standard calculus of variations. The considered class of constraints comprises up to m input constraints and m state constraints with well‐defined relative degree, where m denotes the number of inputs of the given nonlinear system. Starting from an equivalent normal form representation, the constraints are incorporated into a new system dynamics by means of saturation functions and differentiation along the normal form cascade. This procedure leads to a new unconstrained OCP, where an additional penalty term is introduced to avoid the unboundedness of the saturation function arguments if the original constraints are touched. The penalty parameter has to be successively reduced to converge to the original optimal solution. The approach is independent of the method used to solve the new unconstrained OCP. In particular, the constraints cannot be violated during the numerical solution and a successive reduction of the constraints is possible, e.g. to start from an unconstrained solution. Two examples in the single and multiple input case illustrate the potential of the approach. For these examples, a collocation method is used to solve the boundary value problems stemming from the optimality conditions. Copyright © 2009 John Wiley & Sons, Ltd.
MUTYH‐associated polyposis carcinomas frequently lose HLA class I expression—a common event amongst DNA‐repair‐deficient colorectal cancers
Authors: de Miranda Noel FCC , Nielsen Maartje , Pereira Dina , van Puijenbroek Marjo , Vasen Hans F , Hes Frederik J , van Wezel Tom , Morreau Hans
Published: April 2009

Human leukocyte antigen (HLA) class I expression defects frequently occur in colorectal cancers bearing mismatch repair (MMR) deficiencies and are interpreted as immune evasion mechanisms to avoid cancer cell recognition and elimination by the immune system. MMR‐deficient tumours are thought to be more prone to lose HLA class I expression, due to their frequent generation of aberrant peptides which can stimulate a cytotoxic T‐cell‐mediated response. MUTYH‐associated polyposis (MAP) is a colorectal cancer syndrome caused by defects in the MUTYH DNA repair enzyme. Impairment of MUTYH activity could lead to a surplus of mutated peptides which would be presented to cytotoxic T‐cells through the HLA class I molecules. We have studied the frequency of HLA class I expression defects in MAP carcinomas and have compared it to those observed in MMR‐deficient and ‐proficient colorectal tumours. Immunohistochemical detection of the expression of HLA class I, β2‐microglobulin (β2m), and antigen‐processing machinery molecules was performed in 37 primary MAP carcinomas and nine metastases resected from 29 MAP patients. Furthermore, we sequenced the β2m, TAP1, and TAP2 genes. Defects in HLA class I expression were detected in 65% of primary MAP carcinomas, affecting 72% of patients. HLA class I expression abnormalities were often concomitant with β2m expression loss and mutations in the β2m gene. Loss of HLA class I expression is thus a frequent event in MAP carcinomas, similarly to MMR‐deficient colorectal tumours. The extensive mutagenic background of these tumours most likely triggers a strong selective pressure, exerted by the immune system on the tumour, which favours the outgrowth of tumour cell clones with an immune evasive phenotype. Our data provide additional evidence for a link between DNA repair deficiencies and altered HLA class I phenotypes in colorectal cancer. Copyright © 2009 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Bacterial consortium proteomics under 4‐chlorosalicylate carbon‐limiting conditions
Authors: Bobadilla Fazzini Roberto A. , Bielecka Agata , Poucas Quintas Ana K. , Golyshin Peter N. , Preto Maria J. , Timmis Kenneth N. , Martins dos Santos Vitor A. P.
Published: April 2009

In this study, the stable consortium composed by Pseudomonas reinekei strain MT1 and Achromobacter xylosoxidans strain MT3 (cell numbers in proportion 9:1) was under investigation to reveal bacterial interactions that take place under severe nutrient‐limiting conditions. The analysis of steady states in continuous cultures was carried out at the proteome, metabolic profile, and population dynamic levels. Carbon‐limiting studies showed a higher metabolic versatility in the community through upregulation of parallel catabolic enzymes (salicylate 5‐hydroxylase and 17‐fold on 2‐keto‐4‐pentenoate hydratase) indicating a possible alternative carbon routing in the upper degradation pathway highlighting the effect of minor proportions of strain MT3 over the major consortia component strain MT1 with a significant change in the expression levels of the enzymes of the mainly induced biodegradation pathway such as salicylate 1‐hydroxylase and catechol 1,2‐dioxygenase together with important changes in the outer membrane composition of P. reinekei MT1 under different culture conditions. The study has demonstrated the importance of the outer membrane as a sensing/response protective barrier caused by interspecies interactions highlighting the role of the major outer membrane proteins OprF and porin D in P. reinekei sp. MT1 under the culture conditions tested.
Radical anions containing the dioxidated 1,2,5‐thiadiazole heterocycle
Authors: Mirífico María Virginia , Caram José Alberto , Gennaro Ana María , Cobos Carlos Jorge , Vasini Enrique Julio
Published: April 2009

Radical anions of 3,4‐aryl disubstituted 1,2,5‐thiadiazole 1,1‐dioxide were obtained by chemical and electrochemical reduction of their substrates, and characterized by ESR spectroscopy and cyclic voltammetry. The radical anion of the phenanthro[9,10‐c]‐1,2,5‐thiadiazole 1,1‐dioxide was found to be very stable in an aprotic solvent solution and did not react readily when water was added to the aprotic solvent, or the solution was saturated with oxygen gas. The radical formation chemical reaction competed with nucleophilic addition to the CN bond of the thiadiazoles. A possible reaction mechanism, and a common reaction intermediate, supported by density functional theory calculations, is presented for the most stable radical. Copyright © 2009 John Wiley & Sons, Ltd.
A computational study of stereospecifity in the thermal elimination reaction of menthyl benzoate in the gas phase
Authors: Vélez Ederley , Quijano Jairo , Notario Rafael , Pabón Elizabeth , Murillo Juliana , Leal Julieth , Zapata Edilma , Alarcón Gustavo
Published: April 2009

This paper reports a theoretical study, at the B3LYP/6–31 + G(d,p) and M05‐2X/6–31G + (d,p) levels, on the thermal decomposition of menthyl benzoate (2‐isopropyl‐5‐methylcyclohexyl benzoate). It undergoes a unimolecular first‐order elimination to give 3‐menthene (1‐isopropyl‐4‐methylcyclohexene), 2‐menthene (3‐isopropyl‐6‐methylcyclohexene), and benzoic acid. We studied two possible mechanisms trying to explain the formation of 2‐ and 3‐menthene, via six‐membered or four‐membered cyclic transition states. Rate constants were calculated at two temperatures, 587.1 and 598.6 K, and they agree well with the experimentally determined values. We verify that 3‐menthene is the product mainly formed at both temperatures. The progress of the reactions has been followed by means of the Wiberg bond indices. Intrinsic reaction coordinate (IRC) calculations have been carried out to verify that the localized transition state structures connect with the reactants and products and also to verify that the parent compound, menthyl benzoate, is taking the cis‐configuration needed in the reaction. Copyright © 2009 John Wiley & Sons, Ltd.
Theoretical calculations for neighboring group participation in gas‐phase elimination kinetics of 2‐hydroxyphenethyl chloride and 2‐methoxyphenethyl chloride
Authors: Brusco Yannely , Berroteran Neydher , Loroño Marcos , Córdova Tania , Chuchani Gabriel
Published: April 2009

Theoretical calculation of the kinetics and mechanisms of gas‐phase elimination of 2‐hydroxyphenethyl chloride and 2‐methoxyphenethyl chloride has been carried out at the MP2/6‐31G(d,p), B3LYP/6‐31G(d,p), B3LYP/6‐31 + G(d,p), B3PW91/6‐31G(d,p) and CCSD(T) levels of the theory. The two substrates undergo parallel elimination reactions. The first process of elimination appears to proceed through a three‐membered cyclic transition state by the anchimeric assistance of the aromatic ring to produce the corresponding styrene product and HCl. The second process of elimination occurs through a five‐membered cyclic transition state by participation of the oxygen of o‐OH or the o‐OCH3 to yield in both cases benzohydrofuran. The B3PW91/6‐31G(d,p) method was found to be in good agreement with the experimental kinetic and thermodynamic parameters for both substrates in the two reaction channels. However, some differences in the performance of the different methods are observed. NBO analysis of the pyrolysis of both phenethyl chlorides implies a CCl bond polarization, in the sense of Cδ+…Clδ−, which is a rate‐determining step for both parallel reactions. Synchronicity parameters imply polar transition states of these elimination reactions. Copyright © 2009 John Wiley & Sons, Ltd.
Addition of sulfenic acids to monosubstituted acetylenes: a theoretical and experimental study
Authors: Aversa Maria Chiara , Barattucci Anna , Bonaccorsi Paola , Contini Alessandro
Published: April 2009

The reaction of benzenesulfenic acid, generated in situ by thermal decomposition of 3‐(phenylsulfinyl)propanenitrile, with monosubstituted acetylenes was experimentally and theoretically investigated at the DFT level using the MPW1B95 density functional. A computational model based on the Hard Soft Acid Base (HSAB) principle was evaluated for its ability to qualitatively and quantitatively predict the regioselectivity, while kinetics and thermodynamics of the reaction were studied through the analysis of the reaction paths leading to the possible regioisomers. Copyright © 2009 John Wiley & Sons, Ltd.
Neurocognitive and behavioral impact of sleep disordered breathing in children
Authors: Owens Judith A.
Published: April 2009

The consequences of poor quality and/or inadequate sleep in children and adolescents have become a major public health concern, and one in which pediatric health care professionals have become increasingly involved. In particular, insufficient and/or fragmented sleep resulting from primary sleep disorders such as obstructive sleep apnea (OSA), often compounded by the presence of comorbid sleep disorders as well as by voluntary sleep curtailment related to lifestyle and environmental factors, has been implicated in a host of negative consequences. These range from metabolic dysfunction and increased cardiovascular morbidity to impairments in mood and academic performance. The following review will focus on what is currently known about the effects of sleep disordered breathing (SDB) specifically on neurobehavioral and neurocognitive function in children. Because of the scarcity of literature on the cognitive and behavioral impact of sleep disorders in infants and very young children, this review will target largely the preschool/school‐aged child and adolescent populations. In addition, the focus will be on a review of the most recent literature, as a supplement to several excellent previous reviews on the topic.1–4 Pediatr Pulmonol. 2009; 44:417–422. © 2009 Wiley‐Liss, Inc.
Targeted detection of prostate cancer proteins in serum using heavy‐isotope‐labeled‐peptide standards and MALDI‐TOF/TOF
Authors: Li Yan , Sokoll Lori J. , Rush John , Meany Danni , Zou Nan , Chan Daniel W. , Zhang Hui
Published: April 2009

Proteins released from cancer tissues to patient sera can potentially be used to achieve sensitive, specific, and early detection of cancer by means of blood tests. In this study, we used a platform that combines glycopeptide capture, heavy‐isotope‐labeled‐peptide standards, and liquid chromatography coupled to tandem mass spectrometry to determine which glycoproteins from prostate cancer can be detected in sera from patients with early‐stage prostate cancer. The detection limit for prostate‐specific antigen in serum was 3.44 ng/mL; thus, direct identification of low abundance, cancer‐specific proteins was achieved using our platform. We showed that prostatic acid phosphatase and membrane metallo‐endopeptidase that were detected in sera were preferentially expressed in prostate cancer tissues. Levels of these two proteins were elevated in biopsy‐positive patients but not biopsy‐negative groups. Therefore, these two proteins are candidate biomarkers for analysis of patient samples with levels of prostate‐specific antigen in the diagnostic gray zone.
Relating protein conformational changes to packing efficiency and disorder
Authors: Bhardwaj Nitin , Gerstein Mark
Published: April 2009

Changes in protein conformation play key roles in facilitating various biochemical processes, ranging from signaling and phosphorylation to transport and catalysis. While various factors that drive these motions such as environmental changes and binding of small molecules are well understood, specific causative effects on the structural features of the protein due to these conformational changes have not been studied on a large scale. Here, we study protein conformational changes in relation to two key structural metrics: packing efficiency and disorder. Packing has been shown to be crucial for protein stability and function by many protein design and engineering studies. We study changes in packing efficiency during conformational changes, thus extending the analysis from a static context to a dynamic perspective and report some interesting observations. First, we study various proteins that adopt alternate conformations and find that tendencies to show motion and change in packing efficiency are correlated: residues that change their packing efficiency show larger motions. Second, our results suggest that residues that show higher changes in packing during motion are located on the changing interfaces which are formed during these conformational changes. These changing interfaces are slightly different from shear or static interfaces that have been analyzed in previous studies. Third, analysis of packing efficiency changes in the context of secondary structure shows that, as expected, residues buried in helices show the least change in packing efficiency, whereas those embedded in bends are most likely to change packing. Finally, by relating protein disorder to motions, we show that marginally disordered residues which are ordered enough to be crystallized but have sequence patterns indicative of disorder show higher dislocation and a higher change in packing than ordered ones and are located mostly on the changing interfaces. Overall, our results demonstrate that between the two conformations, the cores of the proteins remain mostly intact, whereas the interfaces display the most elasticity, both in terms of disorder and change in packing efficiency. By doing a variety of tests, we also show that our observations are robust to the solvation state of the proteins.
On the occurrence of linear groups in proteins
Authors: Hollingsworth Scott A. , Berkholz Donald S. , Karplus P. Andrew
Published: April 2009

Linear groups—polypeptide conformations based on a single repeating ϕ,ψ‐pair—are a foundational concept in protein structure, yet how they are presented in textbooks is based largely on theoretical studies from the early days of protein structure analysis. Now, ultra‐high resolution protein structures provide a resource for an accurate empirical and systematic assessment of the linear groups that truly exist in proteins. Here, a purely conformation‐based survey of linear groups shows that only three distinct ϕ,ψ‐regions occur: a diverse set of extended conformations mostly present as β‐strands, a broad population of polyproline‐II‐like spirals, and a tight cluster that includes the highly populated α‐helix and the conformationally‐similar but much less populated 310‐helix. Rare, short left‐handed α‐/310‐helical turns with repeating ϕ,ψ‐angles occur, but none are longer than three residues. Misperceptions dispelled by this study are the existence of 2.27‐ and π‐helices as linear groups, the existence of specific ideal ϕ,ψ‐angles for each linear group, and the existence of a substantive difference in the ϕ,ψ‐preferences for parallel versus antiparallel β‐strands. This study provides a concrete basis for updating and enhancing how we think about and teach the basics of protein structure.
Self‐association of streptococcus pyogenes collagen‐like constructs into higher order structures
Authors: Yoshizumi Ayumi , Yu Zhuoxin , Silva Teresita , Thiagarajan Geetha , Ramshaw John A. M. , Inouye Masayori , Brodsky Barbara
Published: April 2009

A number of bacterial collagen‐like proteins with Gly as every third residue and a high Pro content have been observed to form stable triple‐helical structures despite the absence of hydroxyproline (Hyp). Here, the high yield cold‐shock expression system is used to obtain purified recombinant collagen‐like protein (V‐CL) from Streptococcus pyogenes containing an N‐terminal globular domain V followed by the collagen triple‐helix domain CL and the modified construct with two tandem collagen domains V‐CL‐CL. Both constructs and their isolated collagenous domains form stable triple‐helices characterized by very sharp thermal transitions at 35–37°C and by high values of calorimetric enthalpy. Procedures for the formation of collagen SLS crystallites lead to parallel arrays of in register V‐CL‐CL molecules, as well as centrosymmetric arrays of dimers joined at their globular domains. At neutral pH and high concentrations, the bacterial constructs all show a tendency towards aggregation. The isolated collagen domains, CL and CL‐CL, form units of diameter 4–5 nm which bundle together and twist to make larger fibrillar structures. Thus, although this S. pyogenes collagen‐like protein is a cell surface protein with no indication of participation in higher order structure, the triple‐helix domain has the potential of forming fibrillar structures even in the absence of hydroxyproline. The formation of fibrils suggests bacterial collagen proteins may be useful for biomaterials and tissue engineering applications.
Rate and extent of protein localization is controlled by peptide‐binding domain association kinetics and morphology
Authors: Mills Evan , Truong Kevin
Published: April 2009

Protein localization is an important regulatory mechanism in many cell signaling pathways such as cytoskeletal organization and genetic regulation. The specific mechanism of protein localization determines the kinetics and morphological constraints of protein translocation, and thus affects the rate and extent of localization. To investigate the affect of localization kinetics and morphology on protein localization, we designed a protein localization system based on Ca2+‐calmodulin and Src homology 3 domain binding peptides that can translocate between specific localizations in response to a Ca2+signal. We used a stochastic biomolecular simulator to predict that such a protein localization system will exhibit slower and less complete translocations when the association kinetics of a binding domain and peptide are reduced. As well, we predicted that increasing the diffusion resistance by manipulating the morphology of the system would similarly impair translocation speed and completeness. We then constructed a network of synthetic fusion proteins and showed that these predictions could be qualitatively confirmedin vitro. This work provides a basis for explaining the different characteristics (rate and extent) of protein transport and localization in cells as a consequence of the kinetics and morphology of the transport mechanism.
Design, generation, and testing of mammalian expression modules that tag membrane proteins
Authors: Pang John , Zeng Xiaokun , Xiao Rui‐ping , Lakatta Edward G. , Lin Li
Published: April 2009

The expression of mammalian membrane proteins in laboratory cell lines allows their biological functions to be characterized and carefully dissected. However, it is often difficult to design and generate effective antibodies for membrane proteins in the desired studies. As a result, expressed membrane proteins cannot be detected or characterized via common biochemical approaches such as western blotting, immunoprecipitation, or immunohistochemical analysis, and their cellular behaviors cannot be sufficiently investigated. To circumvent such roadblocks, we designed and generated two sets of expression modules that consist of sequences encoding for three essential components: (1) a signal peptide from human receptor for advanced glycation end products that targets the intended protein to the endoplasmic reticulum for cell surface expression; (2) an antigenic epitope tag that elicits specific antibody recognition; and (3) a series of restriction sites that facilitate subcloning of the target membrane protein. The modules were designed with the flexibility to change the epitope tag to suit the specific tagging needs. The modules were subcloned into expression vectors, and were successfully tested with both Type I and Type III human membrane proteins: the receptor for advanced glycation end products, the Toll‐like receptor 4, and the angiotensin II receptor 1. These expressed membrane proteins are readily detected by western blotting, and are immunoprecipitated by antibodies to their relative epitope tags. Immunohistochemical and biochemical analyses also show that the expressed proteins are located at cell surface, and maintain their modifications and biological functions. Thus, the designed modules serve as an effective tool that facilitates biochemical studies of membrane proteins.
Insight into a strategy for attenuating AmpC‐mediated β‐lactam resistance: Structural basis for selective inhibition of the glycoside hydrolase NagZ
Authors: Balcewich Misty D. , Stubbs Keith A. , He Yuan , James Terrence W. , Davies Gideon J. , Vocadlo David J. , Mark Brian L.
Published: April 2009

NagZ is an exo‐N‐acetyl‐β‐glucosaminidase, found within Gram‐negative bacteria, that acts in the peptidoglycan recycling pathway to cleave N‐acetylglucosamine residues off peptidoglycan fragments. This activity is required for resistance to cephalosporins mediated by inducible AmpC β‐lactamase. NagZ uses a catalytic mechanism involving a covalent glycosyl enzyme intermediate, unlike that of the human exo‐N‐acetyl‐β‐glucosaminidases: O‐GlcNAcase and the β‐hexosaminidase isoenzymes. These latter enzymes, which remove GlcNAc from glycoconjugates, use a neighboring‐group catalytic mechanism that proceeds through an oxazoline intermediate. Exploiting these mechanistic differences we previously developed 2‐N‐acyl derivatives of O‐(2‐acetamido‐2‐deoxy‐D‐glucopyranosylidene)amino‐N‐phenylcarbamate (PUGNAc), which selectively inhibits NagZ over the functionally related human enzymes and attenuate antibiotic resistance in Gram‐negatives that harbor inducible AmpC. To understand the structural basis for the selectivity of these inhibitors for NagZ, we have determined its crystallographic structure in complex with N‐valeryl‐PUGNAc, the most selective known inhibitor of NagZ over both the human β‐hexosaminidases and O‐GlcNAcase. The selectivity stems from the five‐carbon acyl chain of N‐valeryl‐PUGNAc, which we found ordered within the enzyme active site. In contrast, a structure determination of a human O‐GlcNAcase homologue bound to a related inhibitor N‐butyryl‐PUGNAc, which bears a four‐carbon chain and is selective for both NagZ and O‐GlcNAcase over the human β‐hexosamnidases, reveals that this inhibitor induces several conformational changes in the active site of this O‐GlcNAcase homologue. A comparison of these complexes, and with the human β‐hexosaminidases, reveals how selectivity for NagZ can be engineered by altering the 2‐N‐acyl substituent of PUGNAc to develop inhibitors that repress AmpC mediated β‐lactam resistance.