Amino Acids 785, 787 of the Na+/H+ Exchanger Cytoplasmic Tail Modulate Protein Activity and Tail Conformation

The mammalian Na⁺/H⁺ exchanger isoform 1 (NHE1) is a plasma membrane protein ubiquitously present in humans. It regulates intracellular pH by removing an intracellular proton in exchange for an extracellular sodium. It consists of a 500 amino acid membrane domain plus a 315 amino acid, regulatory cytosolic tail. Here, we investigated the effect of mutation of two amino acids of the regulatory tail, Ser⁷⁸⁵ and Ser⁷⁸⁷, that were similar in location and context to two amino acids of the Arabidopsis Na⁺/H⁺ exchanger SOS1. Mutation of these two amino acids to either Ala or phosphomimetic Glu did not affect surface targeting but led to a slight reduction in the level of protein expressed. The activity of the NHE1 protein was reduced in the phosphomimetic mutations and the effect was due to a decrease in Vmax activity. The Ser to Glu mutations also caused a change in the apparent molecular weight of both the full-length protein and of the cytosolic tail of NHE1. A conformational change in this region was indicated by differential trypsin sensitivity. We also found that a peptide containing amino acids 783–790 bound to several more proximal regions of the NHE1 tail in in vitro protein interaction experiments. The results are the first characterization of these two amino acids and show that they have significant effects on enzyme kinetics and the structure of the NHE1 protein.     

Structural and physical properties of dried Anaheim chilli peppers modified by low‐temperature blanching

The effect of low‐temperature blanching and drying processes on the ultrastructural and physical properties of Anaheim chilli pepper was studied and optimum conditions to provide a final product with maximum firmness were determined. Lots of Anaheim pepper were blanched in water for 4 min at 48, 55, 65, 75 and 82 °C and maintained for hold times of 35, 45, 60, 75 and 85 min, blanched again for 4 min at 96 °C and dehydrated at 53, 60, 70, 80 and 87 °C. After treatment the samples were rehydrated in water at 30 °C. Rehydration ratio, texture and structural changes were evaluated. Optimisation used a second‐order rotatable central composite design. Texture and rehydration ratio were affected by blanching temperature and the interaction of blanching temperature with hold time (p ≤ 0.05); drying temperature did not show a significant effect. The best results, ie those which gave greatest firmness, were obtained by blanching at 64 °C for 4 min, holding for 55 min after blanching, followed by a second blanching at 96 °C for 4 min and then drying at 70 °C. Evaluation of the rehydrated dried pepper by microscopy showed that low‐temperature blanching close to the optimum conditions provided a protective effect in maintaining cell wall integrity. The results of processing increased firmness in the rehydrated product by a factor of 1.97. Copyright © 2003 Society of Chemical Industry     

Temperature variation of optical energy gap values of the compound CuGaTe2

Measurements of optical absorption in the temperature range 20 to 300K were made on polycrstalline samples of the compound CuGaTe₂. These results were used to determine values of the optical energy gap E_g as a function of temperature T. The resulting curves of E_g vs T were fitted to a simplified Manoogian-Leclerc equation and the fitted coefficients used to give values of (dE_g/dT)₁ and (dE_g/dT)₂, due to lattice dilation and electron-phonon contributions, respectively. Hence, the deformation potentials of the valence and conduction bands were estimated for the present compound.     

Robust-control-based controller design for a mobile robot

The control of a mobile robot using a linear model with uncertainty for design purposes is investigated. The uncertainty arises from the variation of the operation point of the mobile robot. Robust Control Theory is used for the controller design, which allows dealing with systems whose parameters may vary between certain bounds. The proposed controller has shown, in experimentation tests, an acceptable performance and an easy and simple practical implementation. Also, an application of the proposed controller to a leader-following problem is shown; in it, the relative position between robots is obtained through a laser.     

Release kinetics of antioxidant compounds from Hibiscus sabdariffa L. encapsulated in gelatin beads and coated with sodium alginate

Gelatin beads containing a concentrated extract of Roselle (Hibiscus sabdariffa L.) calyx rich in polyphenolic compounds were coated with sodium alginate and ionotropically gelled using CaCl₂. Single‐coated beads and double‐coated beads were obtained by this technique, and the release pattern of the loaded extract was evaluated. As a result, release pattern of these compounds fits properly to a first–order Weibull distribution equation. The release rate constant decreased linearly with the number of alginate coats and with the increase in immersion time in CaCl₂ and the Lag period increased significantly with the number of alginate coats. The release of H. sabdariffa's polyphenols can be well controlled manipulating the number of alginate coats and the immersion time in a CaCl₂ solution, allowing not only to control the gastrointestinal segment where they could be released but also to control the release rate with the certainty that the initial concentration will be completely released showing a highly significant antioxidant activity as well.     

Adsorption of CH3S and CF3S on Pt(111) surface: a density functional theory study

Density functional theory calculations have been performed to study binding modes of adsorbed CX₃S (X = H and F) on Pt(111) for a large range of adsorbate coverages and the consequent work function shifts. We find that these properties are all strongly correlated to the surface coverage. Depending on the molecular coverage on Pt surface, the work function shift may be as large as 0.7 eV for Pt–CH₃S and 1.5 eV for Pt–CF₃S with respect to the clean surface value. Two factors contribute to the work function shift: the charge transfer between the molecule and the surface, and the molecular dipole moment. While the charge transfer contribution always tend to decrease the work function, the molecular dipole moment contribution for the CH₃S and CF₃S cases are oppositely directed. Thus, appropriate choices of molecular components and control of surface coverage would be effective techniques to tune the work function of the metal surfaces.     

Physical properties and antilisterial activity of bioactive edible films containing Lactobacillus plantarum

Bioactive polymeric films were developed from the incorporation of Lactobacillus plantarum into polysaccharide or protein edible films. Lactic acid bacteria (LAB) were added directly to the film forming solution and films were obtained by casting. Four different biopolymers were tested: sodium caseinate, pea protein, methylcellulose and hydroxypropylmethylcellulose. In order to study the impact of the incorporation of the protective culture into the biopolymer matrix, the water vapour permeability (WVP), optical and mechanical properties of the dry films were evaluated. Furthermore, survival of L. plantarum and the antimicrobial potential of bioactive films against Listeria innocua were studied. Whereas optical and mechanical properties of the films were not notably altered by the LAB incorporation, WVP values increased for all biopolymers. Viability of the strain was lower in cellulose derivative matrices than in protein films, although bacteriocin production in the newly prepared films was greater in these matrices. As a result, a significant antimicrobial activity against L. innocua was observed for polysaccharide matrices, which was not observed for protein films, where the bacteriocin production is delayed. In pea protein films the maximum bacteriocin production occurs at 15 storage days and afterwards decreases. So, the nature of the biopolymer and the knowledge of time when an adequate bacteriocin concentration is produced are key to use bioactive films in an effective way.     

A motion control algorithm for a continuous mining machine based on a hierarchical Real-time Control System design methodology

The drive toward increased safety for coal miners has led to the development of computer-assisted methods of underground coal mining. The development of control architectures for the control of the movement of continuous mining machines (tramming control) is an important part of this overall effort. The tramming control algorithm design described is in concert with hierarchical architecture design principles developed at National Institute of Standards and Technology (NIST), referred to as the Real-time Control Systems (RCS) methodology. The algorithm design allows for the control of both cutting and free-space movement by a continuous mining machine and allows for a high degree of human operator interaction.This work is sponsored by the U.S. Bureau of Mines under Interagency Agreement (J0189027).