Textured tetragonal ZrO2 film grown on (100) silicon surface by DLI metal-organic chemical vapor deposition.

Zirconia (ZrO2) thin films with micronic layer thickness are deposited on Si(100) substrates by MOCVD in a cold wall reactor using direct injection (DLI-CVD) process with Zr2(OiPr)6(thd)2 precursor diluted in cyclohexane. The effects of experimental parameters such as substrate's temperature, injection frequency, oxygen partial pressure in the reactive chamber and deposition duration of the process are investigated in order to produce a strongly textured tetragonal ZrO2 film. The films crystalline structure and crystallite size (several nm) are identified by Grazing incidence X-ray diffraction (GIXRD); the microstructure and morphology are observed with the use of FEG-SEM. GIXRD patterns showed the predominance of nano-crystallized tetragonal phase (or cubic) in the films. Pole figures have been analysed for both {111}(t-c) and {200}(t-c) planes in order to evaluate the relationship binding the preferential crystallographic orientation to the column-like growth structure. Besides, the internal stresses levels (with the use of sin2 psi method) within zirconia layers varied from a compressive to a tensile state depending on the experimental deposition conditions and are related to phase orientation and/or transformation into monoclinic one. It is demonstrated that high temperature, low pressure and low deposition time enhanced the tetragonal phase quality that became highly (200)t textured.

[Validation of a self-assessment questionnaire for swallowing disorders (Deglutition Handicap Index)]. / Validation d'un questionnaire d'auto-évaluation du handicap pour les troubles de la déglutition oropharyngée (Deglutition Handicap Index).

OBJECTIVES: The aim of this study is the psychometric validation of a self-assessment questionnaire about swallowing disorders among adults, insisting on the validity of its content. MATERIAL AND METHOD: Created on the model of the "Voice Handicap Index", this questionnaire is composed of 30 statements on deglutition related aspects in daily life (5 point-rating scale). It is subdivided in three domains of 10 items: physical (S) (symptoms related to swallowing), functional (F) (nutritional and respiratory consequences) and emotional (E) (psychosocial consequences). Our first goal was to verify wether the different domains of the questionnaire were well related to what we wished to quantify or not. Therefore, regarding the domain S we compared the physiopathological mechanisms assessed by videofluoroscopy examination, for the domain F its results compared to the nutritional status and for domain E a scale of quality of life. RESULTS: 96 patients with dysphagia and 53 normal subjects were included in the study. The internal consistency reliability was correct (Cronbach's alpha= 0.9), For the domain S the difference between the normal subjects and the patients was statically significant. Our hypothesis regarding the domains were confirmed but not specifically. The domain S is related to the physiopathological mechanisms but also to the degree of severity. There are some correlations between the domain F and the nutritional status but also the results of the videofluoroscopy and the scale of quality of life. The domain E presents a fair correlation with the quality of life but it's related too much to physiopathological mechanisms, the duration of meal and the severity. As a conclusion, the results of this study allows to resume the validation without modification in the questionnaire. We are thinking, because of its similarity with the "Voice Handicap Index", to name it the "Deglutition Handicap Index".

Role of the C-terminal helix in the folding and stability of yeast phosphoglycerate kinase.

In order to determine the role of the C-terminal helix in the folding and stability of yeast phosphoglycerate kinase, a mutant deleted of the 12 C-terminal residues (PGK delta 404-415) was constructed. This mutant folds in a conformation very similar to that of the wild-type protein, but exhibits a very low activity (0.1% of that of the wild-type enzyme). The main structural effect of the deletion of the C-terminal helix is an increase in flexibility of the whole protein and a decrease in stability by about 5 kcal/mol. The structural properties of the truncated protein are very similar, at least qualitatively, to those in the isolated domains. The accessibility of the thiol group of Cys 97 is identical to that in the isolated N-domain. The large solvent effect on the tryptophan fluorescence in the native protein at very low concentration of denaturant reveals an increase of flexibility of the C-domain, similar to that observed on the isolated C-domain. NMR measurements show that the pH dependence of His C2H and C4H chemical shifts in the truncated protein perfectly matches those of the isolated domains. The addition of the missing peptide provokes a 40-fold increase in enzyme activity at saturation. A dissociation constant of 80 microM was determined. This peptide, which displays a random structure in solution, folds in a helical structure in the region 405-410 as assessed by TRNOESY. All these results show that the C-terminal part of yeast phosphoglycerate kinase is not necessary for most of the initial folding steps but acts to lock the C-domain on the N-domain, thus ensuring the expression of full enzyme activity. Without this sequence, the protein has the sum of the properties of the two isolated domains.

Transferred nuclear Overhauser effect study of the C-terminal helix of yeast phosphoglycerate kinase: NMR solution structure of the C-terminal bound peptide.

Two-dimensional 1H nuclear magnetic resonance spectroscopy is used to determine the structure of the C-terminal complementary peptide (404-415) bound to a mutant phosphoglycerate kinase (1-403). Conformational changes in the peptide induced by the formation of the peptide-protein complex are followed by transferred nuclear Overhauser effect spectroscopy. Measurement of transferred NOEs and molecular modeling reveal an alpha-helix fold in the 405-409 region. This fold is in good agreement with the corresponding helix XIV of the crystallographic structure of wild-type PGK (Watson et al., 1982). The role of the alpha-helix from the C-terminal peptide in the recovery of catalytic activity in the mutant PGK is discussed.

Pharmacology of human dopamine D3 receptor expressed in a mammalian cell line: comparison with D2 receptor.

Two cell lines were created by transfecting cDNAs of the human D2 receptor or the recently cloned human D3 receptor to CHO cells, and the properties of [125I]iodosulpride binding to membranes of these cells were compared. In cell lines expressing the D2 receptor subtype where the selectable marker, a phleomycin-resistance gene, was cotransfected in a different plasmid, a stable expression could be maintained for only few passages. In cell lines expressing the D3 receptor subtype, the selectable marker, a dihydrofolate reductase gene, was cotransfected in the same plasmid and a stable expression could be obtained. In addition, the D3 receptor gene could be amplified in these latter cell lines and a high expression level reached (up to 10(6) binding sites per cell). Sodium and, to a lesser extent, lithium similarly increased [125I]iodosulpride binding to D2 and D3 receptors. In the absence of guanylnucleotide, dopamine had a 24-fold higher apparent affinity at D3 than at D2 receptors. Gpp(NH)p induced rightward shift and steepening of dopamine competition curves at either subtype but the effects were more marked at D2 than at D3 receptors. Several agonists and antagonists, previously regarded as autoreceptor-selective, displayed higher affinities at D3 than at D2 receptors. Although most antagonists used as antipsychotics displayed high affinities at the D3 receptor, all were more potent at the D2 receptor. However, the ratio of Ki values varied over about 10-fold among these compounds, suggesting that they realize differential dopamine receptor subtype occupancy during treatments and that this might be reflected in their clinical profile.

Localization and function of the D3 dopamine receptor.

A novel dopamine receptor has been recently cloned, which differs from D1 and D2 receptors by its sequence, localization, pharmacology and possibly signalling system, hence its designation as D3 receptor. The D3 receptor cDNA was obtained by a combination of screenings of DNA libraries and PCR polymerase chain reaction experiments. It encodes a protein with a predicted structure consisting in 7 transmembrane domains indicating that it belongs to the G-protein coupled receptor family. Its global homology is 52% with the D2 receptor but 78% if only transmembrane domains are considered. Two shorter transcript variants, in addition to the full-length cDNA were detected by PCR in various rat brain regions. The shorter transcripts are generated by alternative splicing and encode two putative proteins respectively interrupted after the second transmembrane domain and lacking the second extracytoplasmic loop. After transfection of this latter isoform into cultured cells, no dopaminergic activity could be detected. These shorter splice variants may regulate the number of active D3 receptors. The human D3 receptor was also cloned using similar approaches with rat D3 receptor cDNA probes and was found highly homologous to the rat receptor, except in the third intracytoplasmic loop. The human D3 receptor gene was assigned to the chromosome 3 at q13.3 band. Visualisation of D3 receptor mRNA in rat brain by in situ hybridization indicated a predominant expression of the message in the ventral striatum and other "limbic" areas. There is no overlap in the distributions of D2 and D3 receptor mRNAs in discrete structures, suggesting that the two transcripts are expressed by different cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding of ellipticine to beta-lactoglobulin. A physico-chemical study of the specific interaction of an antitumor drug with a transport protein.

The unprotonated form of the anti-tumor alkaloid ellipticine binds to beta-lactoglobulins A and B from bovine milk with an affinity constant of 7 +/- 3 x 10(5) M-1. There is one binding site/dimeric protein molecule (the stable form at medium pH). The attachment site is not the beta-barrel nor the hydrophobic site identified as the retinol site in beta-lactoglobulin but a domain located at the interface of the two monomeric units where the ligand lies close to Trp61 of both polypeptide chains. The positive binding enthalpy observed in temperature-jump relaxation experiments is overcome by a strong entropy increase, tentatively thought to result from water release at the binding domain. Accordingly, desolvation is assumed to be the rate-determining step in the process of ellipticine binding.