The chloroplast import receptor Toc34 functions as preprotein-regulated GTPase

Toc34 is a protein of the chloroplast outer envelope membrane that acts as receptor for preproteins containing a transit sequence. The recognition of preproteins by Toc34 is regulated by GTP binding and phosphorylation. The phosphorylation site of Toc34 is located at serine 113, close to the postulated triphosphate binding site. This can explain the down-regulation of Toc34 by phosphorylation, resulting in the loss of GTP binding. Vice versa, GTP but not GDP binding of Toc34 influences the phosphorylation. The nucleotide specificity of Toc34 is not only determined by the classical nucleotide binding domains but by a non-typical region at the N-terminus of the protein. As a result, the GTP binding properties are unusual, since the triphosphate moiety of GTP is bound with higher affinity than the purine base. Purified Toc34 hydrolyses GTP at a low rate, which could regulate the receptor function. The rate of hydrolysis is greatly stimulated by a precursor protein

In Vitro Synthesis of Chlorophyll A in the Dark Triggers Accumulation of Chlorophyll A Apoproteins in Barley Etioplasts”

An in vitro translation system using lysed etioplasts was developed to test if the accumulation of plastid-encoded chlorophyll a apoproteins is dependent on the de novo synthesis of chlorophyll a. The P700 apoproteins, CP47 and CP43, were not radiolabeled in pulsechase translation assays employing lysed etioplasts in the absence of added chlorophyll precursors. When chlorophyllide a plus phytylpyrophosphate were added to lysed etioplast translation assays in the dark, chlorophyll a was synthesized and radiolabeled P700 apoproteins, CP47 and CP43, and a protein which comigrates with D1 accumulated. Chlorophyllide a or phytylpyrophosphate added separately to the translation assay in darkness did not induce chlorophyll a formation or chlorophyll a apoprotein accumulation. Chlorophyll a formation and chlorophyll a apoprotein accumulation were also induced in the lysed etioplast translation system by the photoreduction of protochlorophyllide to chlorophyllide a in the presence of exogenous phytylpyrophosphate. Accumulation of radiolabeled CP47 was detectable when very low levels of chlorophyll a were synthesized de novo (less than 0.01 nmol/10(7) plastids), and radiolabel increased linearly with increasing de novo chlorophyll a formation. Higher levels of de novo synthesized chlorophyll a were required prior to detection of radiolabel incorporation into the P700 apoproteins and CP43 (greater than 0.01 nmol/10(7) plastids). Radiolabel incorporation into the P700 apoproteins, CP47 and CP43, saturated at a chlorophyll a concentration which corresponds to 50% of the etioplast protochlorophyllide content (0.06 nmol of chlorophyll a/10(7) plastids)

The postpneumonectomy syndrome: clinical presentation and treatment

Background: Postpneumonectomy syndrome (PPS) is a rare complication after pneumonectomy. It consists of an excessive mediastinal shift resulting in compression and stretching of the tracheobronchial tree and the esophagus. The aim of this study was to give a comprehensive overview of diagnosis, variety of symptoms and evaluation of surgical treatment of PPS. Methods: We retrospectively reviewed the charts of all our patients with PPS since 1994 with respect to symptomatology, treatment and outcome. Our results were compared with case reports and case series in the literature. Results: Six women with a median age of 56.5 years (range 49-65) developed PPS after pneumonectomy for the treatment of lung cancer. Four presented with a right PPS and two with a left PPS, respectively. Symptoms consisted of shortness of breath in all patients and dysphagia as well as heartburn in two patients. Correction of PPS required re-exploration of the pneumonectomy space, reposition of the mediastinum followed by the insertion of single silicone prosthesis in five patients or fixation of the mediastinum with a xenopericardial graft in one patient. We could observe an improvement of the FEV(1)/FVC ratio in all our patients and the clinical improvement of shortness of breath was better than we expected by changes of lung function. Four patients returned to their regular activities with a follow-up of four years. We found 73 cases of PPS in the literature, on the right side in 50 patients (68%) and on the left side in 23 patients (32%). Fifty-nine patients (81%) were treated surgically. Symptoms can be suspicious for cardiogenic origin and vary from heartburn to recurrent syncopes. Conclusion: PPS is rare and not predictable. It can occur after right or left pneumonectomy. Symptoms are manifold and result from a shift, leading to compression and stretching of the two conduits located within the mediastinum, the tracheobronchial tree and the esophagus and consists of shortness of breath, stridor and heartburn. Diagnosis must be made by exclusion. Implantation of prosthesis is the most commonly used and effective treatmen

Protein‐free synthetic surfactant for the prevention and treatment of respiratory distress syndrome in neonates

Q1Q11-9This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: To evaluate the effectiveness of intratracheal administration of synthetic protein‐free pulmonary surfactant in neonates at risk of developing RDS or with established RDS. Comparison 1: Does intratracheal administration of synthetic protein‐free pulmonary surfactant compared to air placebo or normal saline or no treatment reduce mortality and other complications of preterm birth in preterm infants at risk of developing RDS? Comparison 2: Does intratracheal administration of synthetic protein‐free pulmonary surfactant compared to air placebo or normal saline or no treatment reduce mortality and other complications of preterm birth in preterm infants with clinical and/or radiologic evidence of respiratory distress syndrome requiring assisted ventilation

The protein import apparatus of chloroplasts

Routing of cytosolically synthesized precursor proteins into chloroplasts is a specific process which involves a multitude of soluble and membrane components. In this review we wil1 focus on early events of the translocation pathway of nuclear coded plastidic precursor proteins and compare import routes for polypeptide of the outer chloroplast envelope to that of internal chloroplast compartments. A number of proteins housed in the chloroplast envelopes have been implied to be involved in the translocation process, but so far a certain function has not been assigned to any of these proteins. The only exception could be an envelope localized hsc 70 homologue which could retain the import competence of a precursor protein in transit into the organelle

Silicon-hydroxyapatite bioactive coatings (Si-HA) from diatomaceous earth and SiO2: study of adhesion and proliferation of osteoblast-like cells

The aim of this study consisted of investigating the influence of bioactive ceramic coatings of silicon substituted hydroxyapatite (Si-HA) over the behaviour of the human osteoblast-like cell (SaOS-2) line. Pulsed laser deposition (PLD) was the selected technique to deposit the coatings over titanium substrates. Diatomaceous earth and SiO2, together with commercial hydroxyapatite were respectively the silicon and HA sources used to produce the Si-HA coatings. HA coatings with 0% of silicon were used as control of the experiment. [...]info:eu-repo/semantics/publishedVersio

Influence of wettability on constitutive relations and its role in upscaling

The lattice Boltzmann (LB) method is applied to simulating multifluid flow in porous media at sub-pore resolution to determine constitutive behaviors. The authors address the importance of the LB technique for identifying process based constitutive relationships, and demonstrate its application through analysis of the influence of wettability on interfacial areas and constitutive relationships. Porous media surface wettability is varied from uniformly strongly wetted by the resident fluid through strongly wetted by the displacing fluid. Spatially variable wettability is also demonstrated. Primary imbibition and drainage displacements are run, and interfacial areas (IFA) as a function of time are determined and compared. Results indicate that wettability is an important factor in displacement behavior and resulting interfacial area. Primary imbibition in a strongly wet material under capillary dominated flows produces film flow, resulting in high IFAs that decrease with increasing saturation and viscous forces. Primary drainage produces initially high IFA that decreases slightly with increasing saturation or pressure drop. Surfaces with spatially variable wetting can have a strong influence on resulting fluid distributions and fluid flow

Developing the R&D 100 award-winning lattice Boltzmann permeameter toward a marketable product

This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Computational models of oil, gas, and water flow through porous reservoir rock are used in reservoir management to decide whether or not, and how, to develop and produce hydrocarbon reserves. The flow models have major impact on these decisions so their accuracy, cost, and speed is paramount. The accuracy of the flow models is strongly dependent on the accuracy of the physical characterization of the reservoir rock`s pore-fluid system. System characterization is typically done in the laboratory. As an alternative, we have developed a numerical approach for determining the constitutive information. The project sought to use computational techniques that could incorporate all of the basic physical processes that influence fluid movement through the porous rock yet remain computationally efficient. The lattice Boltzmann (LB) numerical technique fits these requirements, and is able to incorporate complex pore geometries exactly and reproduce behavior of multiple fluids. The flexibility of the LB approach allows the numerical model, called the lattice Boltzmann Permeameter (LBP), to determine constitutive relationships (i.e., relative permeabilities) over a much wider range of conditions than can be achieved in a laboratory. Our project was directed toward improving the LBP to make it available to a wide range of users. Improvements were made in computational speed and efficiency, user interfaces, and visualization capabilities