The nuclear lamina is a filamentous nuclear structure intimately connected to the inner nuclear membrane. It is composed of lamins, which are also present in the nuclear interior, and lamin-associated proteins. The nuclear lamina is involved directly or indirectly in many nuclear activities, including DNA replication and transcription, nuclear and chromatin organization, cell cycle regulation, cell development and differentiation, nuclear migration and apoptosis. Mutations in nuclear lamina genes cause a wide range of heritable human diseases, the molecular mechanisms for which are not well understood. This review describes our current knowledge of interactions between nuclear lamina proteins and chromatin, chromatin-remodeling factors, specific transcription factors and RNA polymerase II transcription machinery. Recent studies provide new insights into the nature and regulation of these interactions and suggest additional roles for the nuclear lamina.
An edible and/or chewable article contg. at least one food grade substance having adsorption affinity towards at least one dental plaque (biofilm) constituent and capable of reducing and/or removing the oral biofilm while present in the mouth is described. Particular articles are chewing gums, sweets, candies, candy- and other nutritional bars, ice creams, chocolates, confectionery and bakery/pastry products, honey, dairy products and beverages, and oral hygiene products such as tooth pastes, oral gels and mouthwashes. A chewing gum comprises a conventional gum base and at least one food grade active substance having adsorption affinity towards at least one dental plaque (biofilm) constituent (bacteria and proteins and bacterial cell-free enzymes) and capable of reducing and/or removing the oral biofilm while present in the mouth. Typical active substances are polysaccharides and non-toxic salts thereof, such as alginates, chitosan, CM-cellulose, agar and carrageenan, inorg. substances such as silica, hydroxyapatite and calcium carbonate, and proteins, particularly gelatin and lectin. The chewing gum and other articles are particularly intended for removing and/or for preventing or reducing dental plaque (biofilm), and controlling oral, dental and periodontal diseases. For example, chewing gum base contg. sodium alginate exhibited high binding properties for Streptococcus mutans, av. of 2000% compared to the gum base without the alginate (control = 100% adhesion). Other polysaccharides, such as carrageenan, agar, sodium CM-cellulose and chitosan also exhibited higher adsorption than the control chewing gum base, but less than the alginate (500%, 510%, 600%, and 400%, resp.). [on SciFinder(R)]
A remarkable change in the conductivity of a polyaniline (PAN) Langmuir monolayer in the conducting state, as a function of surface pressure, has been observed using scanning electrochemical microscopy (SECM). The film conductivity, as expressed by the SECM current response of a redox mediator, was measured in-situ in a Langmuir film balance. The conductivity of the film increases significantly with surface pressure, above a threshold value of ca. 20 mN m-1.[on SciFinder (R)]
A remarkable change in the cond. of a polyaniline (PANI) Langmuir monolayer in the conducting state, as a function of surface pressure, was obsd. using scanning electrochem. microscopy (SECM). The film cond., as expressed by the SECM current response of a redox mediator, was measured in-situ in a Langmuir film balance. The cond. of the film increases significantly with surface pressure, above a threshold value of ca. 20 mN m-1. [on SciFinder(R)]
The application of self-assembled monolayers (SAMs) as a means of achieving speciation in heavy metal electrochem. detn. is demonstrated. SAMs are monomol. org. layers that can be chem. attached onto different electrode materials and used for the selective extn. of heavy metals. The selectivity is achieved by assembling monolayers that have pendant ligands, which interact selectively with the analytes in the soln. For example, the formation of a monolayer comprising a pyridine group was used to selectively ext. Cr(VI) from aq. solns., whereas the selective detn. of Fe(II) was accomplished using a covalently bound terpyridine monolayer. Yet, detg. the heterogeneous binding consts. of the metallic species by the SAMs is of significant importance and allows studying quant. the interactions between the monolayer and the metal ions. The authors have developed a few methods for detg. the binding consts. of heavy metal ions by SAMs of which two of them are briefly discussed here. [on SciFinder(R)]
Sol-gel films were electrodeposited on Al electrodes following the methodol. the authors have developed and is based on applying neg. potentials. This increases the pH at the surface, causing acceleration of the polymn. The authors' process follows the two step method, in which the monomer is 1st hydrolyzed in acidic soln. (pH ∼ 4) and only then the neg. potential is applied, which consumes protons and releases hydroxyl ions, thus enhancing the condensation. Films made of different monomers, i.e., tetraethoxysilane (TEOS), Me trimethoxysilane and Ph trimethoxysilane (PTMOS), were prepd., characterized and examd. for their corrosion inhibition properties. Potentiodynamic polarization, electrochem. impedance spectroscopy, optical and SEM as well as at. force microscopy were used as a means of film characterization. Hydrophobic and steric silanes, such as PTMOS showed a considerable corrosion inhibition capacity as compared to the capacity exhibited by less hydrophobic and steric derivs. such as TEOS. The difference between the conventional dip-coating method and the electrodeposition approach for depositing sol-gel films was also examd., indicating a clear advantage of the latter. [on SciFinder(R)]
We find the key behind the existence traits of asymptotic saturated nonlinear optical solitons in the emergence of linear wave segments. These traits, produced by the progressive relegation of nonlinear dynamics to wave tails, allow a direct and versatile analytical prediction of self-trapping existence conditions and simple soliton scaling laws, which we confirm experimentally in saturated-Kerr self-trapping observed in photorefractives. This approach provides the means to correctly evaluate beam tails in the saturated regime, which is instrumental in the prediction of soliton interaction forces. (C) 2003 Optical Society of America.
We present a theoretical study of the energetics, equilibrium size, and size distribution of membrane pores composed of electrically charged amphipathic peptides. The peptides are modeled as cylinders (mimicking alpha-helices) carrying different amounts of charge, with the charge being uniformly distributed over a hydrophilic face, defined by the angle subtended by polar amino acid residues. The free energy of a pore of a given radius, R, and a given number of peptides, s, is expressed as a sum of the peptides' electrostatic charging energy (calculated using Poisson-Boltzmann theory), and the lipid-perturbation energy associated with the formation of a membrane rim (which we model as being semitoroidal) in the gap between neighboring peptides. A simple phenomenological model is used to calculate the membrane perturbation energy. The balance between the opposing forces (namely, the radial free energy derivatives) associated with the electrostatic free energy that favors large R, and the membrane perturbation term that favors small R, dictates the equilibrium properties of the pore. Systematic calculations are reported for circular pores composed of various numbers of peptides, carrying different amounts of charge (1-6 elementary, positive charges) and characterized by different polar angles. We find that the optimal R's, for all (except, possibly, very weakly) charged peptides conform to the ``toroidal'' pore model, whereby a membrane rim larger than similar to1 nm intervenes between neighboring peptides. Only weakly charged peptides are likely to form ``barrel-stave'' pores where the peptides essentially touch one another. Treating pore formation as a two-dimensional self-assembly phenomenon, a simple statistical thermodynamic model is formulated and used to calculate pore size distributions. We find that the average pore size and size polydispersity increase with peptide charge and with the amphipathic polar angle. We also argue that the transition of peptides from the adsorbed to the inserted (membrane pore) state is cooperative and thus occurs rather abruptly upon a change in ambient conditions.
Liquid pyridine and polymeric solutions of poly(4-vinyl pyridine)/pyridine/water doped with Europium exhibit a broad blue emission centered at 460 nm with low intensities emissions at 590 and 614 nm under excitation of 380 nm wavelength via a pyridine electronic state. Under excitation of 395 nm wavelength to the 5L6 state effective quenching of Eu(III) 5D0 emission in both cases was observed. The polymeric solution is a photosensitive material and becomes a gel under UV-irradiation. In a gel the longer-wavelength yellow-colored emission under excitation of 460–480 nm appears. The presence of Eu(III) significantly increases the intensity of this emission. The maximum of the peak position is blue shifted from 524 to 504 nm and its quantum efficiency is higher by a factor of five. We make a first effort to interpret the results.
Meteorological radar is a remote sensing system that provides rainfall estimations at high spatial and temporal resolutions. The radar-based rainfall intensities (R) are calculated from the observed radar reflectivities (Z). Often, rain gauge rainfall observations are used in combination with the radar data to find the optimal parameters in the Z–R transformation equation. The scale dependency of the power-law Z–R parameters when estimated from radar reflectivity and rain gauge intensity data is explored herein. The multiplicative (a) and exponent (b) parameters are said to be “scale dependent” if applying the observed and calculated rainfall intensities to objective function at different scale results in different “optimal” parameters. Radar and gauge data were analyzed from convective storms over a midsize, semiarid, and well-equipped watershed. Using the root-mean-square difference (rmsd) objective function, a significant scale dependency was observed. Increased time- and space scales resulted in a considerable increase of the a parameter and decrease of the b parameter. Two sources of uncertainties related to scale dependency were examined: 1) observational uncertainties, which were studied both experimentally and with simplified models that allow representation of observation errors; and 2) model uncertainties. It was found that observational errors are mainly (but not only) associated with positive bias of the b parameter that is reduced with integration, at least for small scales. Model errors also result in scale dependency, but the trend is less systematic, as in the case of observational errors. It is concluded that identification of optimal scale for Z–R relationship determination requires further knowledge of reflectivity and rain-intensity error structure.
Meteorological radar is a remote sensing system that provides rainfall estimations at high spatial and temporal resolutions. The radar-based rainfall intensities (R) are calculated from the observed radar reflectivities (Z). Often, rain gauge rainfall observations are used in combination with the radar data to find the optimal parameters in the Z–R transformation equation. The scale dependency of the power-law Z–R parameters when estimated from radar reflectivity and rain gauge intensity data is explored herein. The multiplicative (a) and exponent (b) parameters are said to be “scale dependent” if applying the observed and calculated rainfall intensities to objective function at different scale results in different “optimal” parameters. Radar and gauge data were analyzed from convective storms over a midsize, semiarid, and well-equipped watershed. Using the root-mean-square difference (rmsd) objective function, a significant scale dependency was observed. Increased time- and space scales resulted in a considerable increase of the a parameter and decrease of the b parameter. Two sources of uncertainties related to scale dependency were examined: 1) observational uncertainties, which were studied both experimentally and with simplified models that allow representation of observation errors; and 2) model uncertainties. It was found that observational errors are mainly (but not only) associated with positive bias of the b parameter that is reduced with integration, at least for small scales. Model errors also result in scale dependency, but the trend is less systematic, as in the case of observational errors. It is concluded that identification of optimal scale for Z–R relationship determination requires further knowledge of reflectivity and rain-intensity error structure.
