Molecular evolution and phylogeny of elapid snake venom three-finger toxins

Animal venom components are of considerable interest to researchers across a wide variety of disciplines, including molecular biology, biochemistry, medicine, and evolutionary genetics. The three-finger family of snake venom peptides is a particularly interesting and biochemically complex group of venom peptides, because they are encoded by a large multigene family and display a diverse array of functional activities. In addition, understanding how this complex and highly varied multigene family evolved is an interesting question to researchers investigating the biochemical diversity of these peptides and their impact on human health. Therefore, the purpose of our study was to investigate the long-term evolutionary patterns exhibited by these snake venom toxins to understand the mechanisms by which they diversified into a large, biochemically diverse, multigene family. Our results show a much greater diversity of family members than was previously known, including a number of subfamilies that did not fall within any previously identified groups with characterized activities. In addition, we found that the long-term evolutionary processes that gave rise to the diversity of three-finger toxins are consistent with the birth-and-death model of multigene family evolution. It is anticipated that this three-finger toxin toolkit will prove to be useful in providing a clearer picture of the diversity of investigational ligands or potential therapeutics available within this important family.

Analytical exclusion chromatography

This review summarizes the development of exclusion chromatography, also termed gel filtration, molecular-sieve chromatography and gel permeation chromatography, for the quantitative characterization of solutes and solute interactions. As well as affording a means of determining molecular mass and molecular mass distribution, the technique offers a convenient way of characterizing solute selfassociation and solute-ligand interactions in terms of reaction stoichiometry and equilibrium constant. The availability of molecular-sieve media with different selective porosities ensures that very little restriction is imposed on the size of solute amenable to study. Furthermore, access to a diverse array of assay procedures for monitoring the column eluate endows analytical exclusion chromatography with far greater flexibility than other techniques from the viewpoint of solute concentration range that can be examined. In addition to its widely recognized prowess as a means of solute separation and purification, exclusion chromatography thus also possesses considerable potential for investigating the functional roles of the purified solutes. (C) 2003 Elsevier Science B.V. All rights reserved.

Flotillins and the PHB domain protein family: Rafts, worms and anaesthetics

While our understanding of lipid microdomains has advanced in recent years, many aspects of their formation and dynamics are still unclear. In particular, the molecular determinants that facilitate the partitioning of integral membrane proteins into lipid raft domains are yet to be clarified. This review focuses on a family of raft-associated integral membrane proteins, termed flotillins, which belongs to a larger class of integral membrane proteins that carry an evolutionarily conserved domain called the prohibitin homology (PHB) domain. A number of studies now suggest that eucaryotic proteins carrying this domain have affinity for lipid raft domains. The PHB domain is carried by a diverse array of proteins including stomatin, podocin, the archetypal PHB protein, prohibitin, lower eucaryotic proteins such as the Dictyostelium discoideum proteins vacuolin A and vacuolin B and the Caenorhabditis elegans proteins unc-1, unc-24 and mec-2. The presence of this domain in some procaryotic proteins suggests that the PHB domain may constitute a primordial lipid recognition motif. Recent work has provided new insights into the trafficking and targeting of flotillin and other PHB domain proteins. While the function of this large family of proteins remains unclear, studies of the C. elegans PHB proteins suggest possible links to a class of volatile anaesthetics raising the possibility that these lipophilic agents could influence lipid raft domains. This review will discuss recent insights into the cell biology of flotillins and the large family of evolutionarily conserved PHB domain proteins.

Molecular control of cell type diversity in the developing spinal cord

1, During embryonic development, a diverse array of neurons and glia are generated at specific positions along the dorsoventral and rostro-caudal axes of the spinal cord from a common pool of precursor cells. 2. This cell type diversity can be distinguished by the spatially and temporally coordinated expression of several transcription factors that are also linked to cell type specification at a very early stage of spinal cord development. 3, Recent studies have started to uncover that the generation of cell type diversity in the developing spinal cord. Moreover, distinct cell types in the spinal cord appear to be determined by the spatially and temporally coordinated expression of transcription factors. 4. The expression of these factors also appears to be controlled by gradients of factors expressed by ventral and dorsal midline cells, namely Sonic hedgehog and members of the transforming growth factor-beta family. 5, Changes in the competence of precursor cells and local cell interactions may also play important roles in cell type specification within the developing spinal cord.

Chimeric 16S rDNA sequences of diverse origin are accumulating in the public databases

A significant number of chimeric 16S rDNA sequences of diverse origin were identified in the public databases by partial treeing analysis. This suggests that chimeric sequences, representing phylogenetically novel non-existent organisms, are routinely being overlooked in molecular phylogenetic surveys despite a general awareness of PCR-generated artefacts amongst researchers.

A Ku-band active transmit-array module with a horn or patch array as a signal launching/receiving device

This paper is concerned with the design of a Ku-band active transmit-array module of transistor amplifiers excited by either a pyramidal horn or a patch array Optimal distances between the active transmit array and the signal-launching:receiving device, which is either a passive corporate-fed array or a horn, are determined to maximise the power gain at a design frequency: Having established these conditions, the complete structure is investigated in terms of operational bandwidth and near-field and far-field distributions measured at the output side of the transmit array, The experimental results show that the use of a corporate-fed array as an illuminating/receiving device gives higher gain and significantly larger operational bandwidth, An explanation for this behavior is sought.

Investigations into a wideband spatial beamformer employing a rectangular array of planar monopoles

This paper presents a rectangular array antenna with a suitable signal-processing algorithm that is able to steer the beam in azimuth over a wide frequency band. In the previous approach, which was reported in the literature, an inverse discrete Fourier transform technique was proposed for obtaining the signal weighting coefficients. This approach was demonstrated for large arrays in which the physical parameters of the antenna elements were not considered. In this paper, a modified signal-weighting algorithm that works for arbitrary-size arrays is described. Its validity is demonstrated in examples of moderate-size arrays with real antenna elements. It is shown that in some cases, the original beam-forming algorithm fails, while the new algorithm is able to form the desired radiation pattern over a wide frequency band. The performance of the new algorithm is assessed for two cases when the mutual coupling between array elements is both neglected and taken into account.

Linewidth reduction in a large-smile laser diode array

We present theory and simulations for a spectral narrowing scheme for laser diode arrays (LDAs) that employs optical feedback from a diffraction grating. We calculate the effect of the so-called smile of the LDA and show that it is possible to reduce the effect by using a cylindrical lens set at an angle to the beam. The scheme is implemented on a 19-element LDA with smile of 7.6 mu m and yields frequency narrowing from a free-running width of 2 to 0.15 nm. The experimental results are in good agreement with the theory. (c) 2005 Optical Society of America.

A wideband array antenna with beam-steering capability using real valued weights

This article presents an array antenna with beam-steering capability in azimuth over a wide frequency band using real-valued weighting coefficients that can be realized in practice by amplifiers or attenuators. The described beamforming scheme relies on a 2D (instead of 1D) array structure in order to make sure that there are enough degrees of freedom to realize a given radiation pattern in both the angular and frequency domains. In the presented approach, weights are determined using an inverse discrete Fourier transform (IDFT) technique by neglecting the mutual coupling between array elements. Because of the presence of mutual coupling, the actual array produces a radiation pattern with increased side-lobe levels. In order to counter this effect, the design aims to realize the initial radiation pattern with a lower side-lobe level. This strategy is demonstrated in the design example of 4 X 4 element array. (C) 2005 Wiley Periodicals. Inc.

Fully spatial wide-band beamforming using a rectangular array of planar monopoles

This paper describes a spatial beamformer which by using a rectangular array antenna steers a beam in azimuth over a wide frequency band without frequency filters or tap-delay networks. The weighting coefficients are real numbers which can be realized by attenuators or amplifiers. A prototype including a 4 x 4 array of square planar monopoles and a feeding network composed of attenuators, power divider/combiners and a rat-race hybrid is developed to test the validity of this wide-band beamforming concept. The experimental results prove the validity of this wide-band spatial beamformer for small size arrays.

Multiple-acquisition parallel imaging combined with a transceive array for the amelioration of high-field RF distortion: a modeling study

A new method for ameliorating high-field image distortion caused by radio frequency/tissue interaction is presented and modeled, The proposed method uses, but is not restricted to, a shielded four-element transceive phased array coil and involves performing two separate scans of the same slice with each scan using different excitations during transmission. By optimizing the amplitudes and phases for each scan, antipodal signal profiles can be obtained, and by combining both images together, the image distortion can be reduced several-fold. A hybrid finite-difference time-domain/method-of-moments method is used to theoretically demonstrate the method and also to predict the radio frequency behavior inside the human head. in addition, the proposed method is used in conjunction with the GRAPPA reconstruction technique to enable rapid imaging. Simulation results reported herein for IIT (470 MHz) brain imaging applications demonstrate the feasibility of the concept where multiple acquisitions using parallel imaging elements with GRAPPA reconstruction results in improved image quality. (c) 2006 Wiley Periodicals, Inc.

Wideband beam and steering using a rectangular array of planar monopoles

This article presents the design of a wideband rectangular array of planar monopoles, which is able to steer its beam and nulls over a wide frequency band using real-valued weights. These weights can be realized in practice by amplifiers or attenuators leading to a low cost development of a wideband array antenna with beam and null steering capability. The weights are determined by applying an inverse discrete Fourier transform to an assumed radiation pattern. This wideband beam and null forming concept is verified by full electromagnetic simulations which take into account mutual coupling effects between the array elements.

A dual band 2.4/5.2GHz antenna including a radial line slot array and a patch

The design of an antenna that combines a radial line slot array and a circular patch to operate as a dual band (2.4/5.2 GHz) antenna at the access point of a WLAN is presented. The design has been accomplished using commercially available Ansoft HFSS and in-house developed software. The designed antenna shows good performance in terms of return losses, radiation pattern and circular polarization in the two, 2.4 and 5.2 GHz, frequency bands. Due to its good electrical performance and a relatively low profile and low developmental cost, it should be found attractive for use as an access point antenna for dual band operation.

High frequency (1000 Hz) tympanometry in normal neonates

The characteristics of high frequency (1000 Hz) acoustic admittance results obtained from normal neonates were described in this study. Participants were 170 healthy neonates (96 boys and 74 girls) aged between 1 and 6 days (mean = 3.26 days, SD = 0.92). Transient evoked otoacoustic emissions (TEOAEs), and 226 Hz and 1000 Hz probe tone tympanograms were obtained from the participants using a Madsen Capella OAE/middle ear analyser. The results showed that of the 170 neonates, 34 were not successfully tested in both ears, 14 failed the TEOAE screen in one or both ears, and 122 (70 boys, 52 girls) passed the TEOAE screen in both ears and also maintained an acceptable probe seal during tympanometry. The 1000 Hz tympanometric data for the 122 neonates (244 ears) showed a single-peaked tympanogram in 225 ears (92.2 %), a flat-sloping tympanogram in 14 ears (5.7 %), a double-peaked tympanogram in 3 ears (1.2 %) and other unusual shapes in 2 ears (0.8 %). There was a significant ear effect, with right ears showing significantly higher mean peak compensated static admittance and tympanometric width, but lower mean acoustic admittance at +200 daPa and gradient than left ears. No significant gender effects or its interaction with ear were found. The normative tympanometric data derived from this cohort may serve as a guide for detecting middle ear dysfunction in neonates.

A method to lower the detection limit for optical beat signals from a frequency-dithered stabilized laser

A narrow absorption feature in an atomic or molecular gas (such as iodine or methane) is used as the frequency reference in many stabilized lasers. As part of the stabilization scheme an optical frequency dither is applied to the laser. In optical heterodyne experiments, this dither is transferred to the RF beat signal, reducing the spectral power density and hence the signal to noise ratio over that in the absence of dither. We removed the dither by mixing the raw beat signal with a dithered local oscillator signal. When the dither waveform is matched to that of the reference laser the output signal from the mixer is rendered dither free. Application of this method to a Winters iodine-stabilized helium-neon laser reduced the bandwidth of the beat signal from 6 MHz to 390 kHz, thereby lowering the detection threshold from 5 pW of laser power to 3 pW. In addition, a simple signal detection model is developed which predicts similar threshold reductions.