: The solution structure of a new B‐chain mutant of bovine insulin, in which the cysteines B7 and... more : The solution structure of a new B‐chain mutant of bovine insulin, in which the cysteines B7 and B19 are replaced by two serines, has been determined by circular dichroism, 2D‐NMR and molecular modeling. This structure is compared with that of the oxidized B‐chain of bovine insulin [Hawkins et al. (1995) Int. J. Peptide Protein Res.46, 424–433]. Circular dichroism spectroscopy showed in particular that a higher percentage of helical secondary structure for the B‐chain mutant is estimated in trifluoroethanol solution in comparison with the oxidized B‐chain. 2D‐NMR experiments confirmed, among multiple conformations, that the B‐chain mutant presents defined secondary structures such as a α‐helix between residues B9 and B19, and a β‐turn between amino acids B20 and B23 in aqueous trifluoroethanol. The 3D structures, which are consistent with NMR data and were obtained using a simulated annealing protocol, showed that the tertiary structure of the B‐chain mutant is better resolved and is more in agreement with the insulin crystal structure than the oxidized B‐chain structure described by Hawkins et al. An explanation could be the presence of two sulfonate groups in the oxidized insulin B‐chain. Either by their charges and/or their size, such chemical groups could play a destructuring effect and thus could favor peptide flexibility and conformational averaging. Thus, this study provides new insights on the folding of isolated B‐chains.
OBJECTIVE This study investigated the chemical and structural changes in the mineral phase and co... more OBJECTIVE This study investigated the chemical and structural changes in the mineral phase and collagen of dentin during application of a mild universal adhesive. Particular attention was paid to the role of isopropanol and changes in water molecules. METHODS In vitro application of the mild universal adhesive on dentin with two established etching modes (self-etch and etch-and-rinse) was studied using solid state nuclear magnetic resonance spectroscopy. RESULTS It was evidenced that the etch-and-rinse mode leads to a decrease of the inorganic apatite and a reorganization of the residual mineral phase with a low amount of adhesive phosphate monoesters calcium salt formed, compared to the self-etch mode. In contrast, the adhesive interacts very similarly to the level of dentin collagen in both protocols, with a strong decrease in the amount of the free water molecules induced by the presence of isopropanol as the adhesive solvent, but without significant changes in the initial collagen structure. For both modes, the adhesive acrylates monomers remain mobile and can infiltrate the collagen. SIGNIFICANCE Understanding the molecular interactions between dentin and adhesive solutions is a major challenge for designing products that lead to the formation of ideal dentin resin hybrid layer. Notably, one point considered essential is the presence of unbound water which, over time, is associated with a hydrolytic degradation of the organic matrix. Isopropanol, as an adhesive solvent, leads to a decrease in the amount of the less stable water molecules while the water molecules strongly attached to the collagen are retained, thus preserving the collagen structure.
Phosphorus Sulfur and Silicon and The Related Elements, Aug 1, 1997
... A NON CLASSICAL REACTION OF 2(3)- BROMOMETHYL-3(2)-NITROTHIOPHENES TOWARDS BASES ADAM DAICH&q... more ... A NON CLASSICAL REACTION OF 2(3)- BROMOMETHYL-3(2)-NITROTHIOPHENES TOWARDS BASES ADAM DAICH", YANN PRIGENTb and BERNARD DECRODC"' ... B. Rigo, R. Dolaine, S. El Ghammarti, D. Couturier, J. Heremcyclic Chem., 33, 1063-1066 (1996). ...
Journal of the American Chemical Society, Nov 11, 2009
The Stokes-Einstein expression of the diffusion coefficient as a function of the hydrodynamic rad... more The Stokes-Einstein expression of the diffusion coefficient as a function of the hydrodynamic radius of the diffusing object does not explicitly carry the mass dependency of the object. It is possible to correlate the translational self-diffusion coefficients D with the molecular weight M for an ensemble of cyclic or hollow clusters ranging from about 200 to 30,000 g x mol(-1). From this correlation, the mass of a cluster can be deduced from its diffusion coefficient. Consistency of diffusion as a power law of mass and Stokes-Einstein formulation is completely fulfilled with the selected compounds of this contribution.
La trichorzianine tavii est un peptide antibiotique compose de 19 residus qui a la propriete de f... more La trichorzianine tavii est un peptide antibiotique compose de 19 residus qui a la propriete de former, dans les bicouches phospholipides, ces canaux dont l'activite depend d'un potentiel trans-membranaire. Afin de tenter de comprendre le mecanisme d'action du peptide sur les membranes, l'etude structurale de tavii en solution dans le methanol et en milieu micellaire (rapport molaire sds/tavii=50) a ete realisee par resonance magnetique nucleaire #1h, #1#3c et #1#5n. Une attribution complete des signaux rmn a ete realisee pour ces trois noyaux. De nombreuses informations conformationnelles ont ete obtenues a l'aide d'experiences de rmn 2d (cosy-dqf, hohaha, noesy, roesy, hmqc, hm3c). Les valeurs de constantes de couplage 3jhn-ch, les coefficients de temperature des groupes nh et cc, les temps de relaxation longitudinaux #1#3c ont ete determines et les effets overhauser nucleaires analyses quantitativement. L'ensemble de ces resultats a permis de realiser la modelisation du peptide. Les conformations de la trichorzianine tavii en solution dans le methanol et en milieu micellaire, determinees par ces methodes, semblent similaires et sont caracterisees par une helice droite rigide, coudee au niveau des residus u#9-s#1#0 et incluant deux tours d'helice 3#1#0 au niveau de la proline et un tour mixte /3#1#0 en partie n-terminale. En presence de sds, tavii apparait aussi structure qu'en solution methanolique. Ces resultats suggerent que le mecanisme d'action de ce peptide sur les membranes met en jeu une reorientation globale de l'helice dans la bicouche et non un mouvement d'une partie du squelette peptidique
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ABSTRACT Harzianin HK VI, one of the major peptides of the natural mixture of peptaibol antibioti... more ABSTRACT Harzianin HK VI, one of the major peptides of the natural mixture of peptaibol antibiotics biosynthesized by the fungus Trichoderma pseudokoningii, has been isolated by a multi-step chromatography procedure including HPLC. Its sequence was determined by positive ion FAB MS and two-dimensional 1H and 13C NMR experiments (COSY, HOHAHA, HSQC-HOHAHA, HMBC), allowing the location in the sequence of two isoleucines at positions 3 and 4 and of two leucines at positions 7 and 8, which could not be distinguished on the basis of their 1H NMR spin systems. Harzianin HK VI is an 11-residue peptaibol with two Aib-Pro sequences at positions 5–6 and 9–10. From ROESY data and amide temperature coefficients, a β-bend ribbon stabillised by intramolecular hydrogen bonds of the 4→1 type is suggested. Despite the short sequence, harzianin HK VI increases the permeability of liposome bilayers to the same extent as longer 14-residue peptaibols.
from various Trichodenna species, 11to 20-residue amphiphilic peptides have been isolated and the... more from various Trichodenna species, 11to 20-residue amphiphilic peptides have been isolated and their sequences elucidatedjrom FAB MS and NMR data. They are structured in helices, mainly of the a-type. Their membrane activity has been examined by using SUV as model membranes. Introduction Trichoderma are saprophytic and ubiquitous soil fungi with cellulolytic activity and T. viride the type species of the genus, is ranked as one of the most widely distributed of all soU fungi. The genus is characterized by fast growing colonies with conidia more usually green. Rifai (1) distinguished nine species aggrcgated, based on microscopie characters, but the macroscopic features are very similar for most of them. Among the species we have studied were T. harzianum, a very common species described in Africa, America and Europe, T. koningii, also common in Europe, Central-America, India, Tahiti, New-Zealand and lapan and T. longibrachiatum, quite rare, found in France but also in New-Zealand (2)....
La presente invention concerne de nouveaux supports chromatographiques de grande purete a base de... more La presente invention concerne de nouveaux supports chromatographiques de grande purete a base de cyclodextrines natives ou modifiees, liees regioselectivement en position 2, 3 ou 6 a un gel de silice par l'intermediaire d'un bras espaceur contenant un heteroatome. Elle concerne egalement leur procede de fabrication et leurs applications.
: The solution structure of a new B‐chain mutant of bovine insulin, in which the cysteines B7 and... more : The solution structure of a new B‐chain mutant of bovine insulin, in which the cysteines B7 and B19 are replaced by two serines, has been determined by circular dichroism, 2D‐NMR and molecular modeling. This structure is compared with that of the oxidized B‐chain of bovine insulin [Hawkins et al. (1995) Int. J. Peptide Protein Res.46, 424–433]. Circular dichroism spectroscopy showed in particular that a higher percentage of helical secondary structure for the B‐chain mutant is estimated in trifluoroethanol solution in comparison with the oxidized B‐chain. 2D‐NMR experiments confirmed, among multiple conformations, that the B‐chain mutant presents defined secondary structures such as a α‐helix between residues B9 and B19, and a β‐turn between amino acids B20 and B23 in aqueous trifluoroethanol. The 3D structures, which are consistent with NMR data and were obtained using a simulated annealing protocol, showed that the tertiary structure of the B‐chain mutant is better resolved and is more in agreement with the insulin crystal structure than the oxidized B‐chain structure described by Hawkins et al. An explanation could be the presence of two sulfonate groups in the oxidized insulin B‐chain. Either by their charges and/or their size, such chemical groups could play a destructuring effect and thus could favor peptide flexibility and conformational averaging. Thus, this study provides new insights on the folding of isolated B‐chains.
OBJECTIVE This study investigated the chemical and structural changes in the mineral phase and co... more OBJECTIVE This study investigated the chemical and structural changes in the mineral phase and collagen of dentin during application of a mild universal adhesive. Particular attention was paid to the role of isopropanol and changes in water molecules. METHODS In vitro application of the mild universal adhesive on dentin with two established etching modes (self-etch and etch-and-rinse) was studied using solid state nuclear magnetic resonance spectroscopy. RESULTS It was evidenced that the etch-and-rinse mode leads to a decrease of the inorganic apatite and a reorganization of the residual mineral phase with a low amount of adhesive phosphate monoesters calcium salt formed, compared to the self-etch mode. In contrast, the adhesive interacts very similarly to the level of dentin collagen in both protocols, with a strong decrease in the amount of the free water molecules induced by the presence of isopropanol as the adhesive solvent, but without significant changes in the initial collagen structure. For both modes, the adhesive acrylates monomers remain mobile and can infiltrate the collagen. SIGNIFICANCE Understanding the molecular interactions between dentin and adhesive solutions is a major challenge for designing products that lead to the formation of ideal dentin resin hybrid layer. Notably, one point considered essential is the presence of unbound water which, over time, is associated with a hydrolytic degradation of the organic matrix. Isopropanol, as an adhesive solvent, leads to a decrease in the amount of the less stable water molecules while the water molecules strongly attached to the collagen are retained, thus preserving the collagen structure.
Phosphorus Sulfur and Silicon and The Related Elements, Aug 1, 1997
... A NON CLASSICAL REACTION OF 2(3)- BROMOMETHYL-3(2)-NITROTHIOPHENES TOWARDS BASES ADAM DAICH&q... more ... A NON CLASSICAL REACTION OF 2(3)- BROMOMETHYL-3(2)-NITROTHIOPHENES TOWARDS BASES ADAM DAICH", YANN PRIGENTb and BERNARD DECRODC"' ... B. Rigo, R. Dolaine, S. El Ghammarti, D. Couturier, J. Heremcyclic Chem., 33, 1063-1066 (1996). ...
Journal of the American Chemical Society, Nov 11, 2009
The Stokes-Einstein expression of the diffusion coefficient as a function of the hydrodynamic rad... more The Stokes-Einstein expression of the diffusion coefficient as a function of the hydrodynamic radius of the diffusing object does not explicitly carry the mass dependency of the object. It is possible to correlate the translational self-diffusion coefficients D with the molecular weight M for an ensemble of cyclic or hollow clusters ranging from about 200 to 30,000 g x mol(-1). From this correlation, the mass of a cluster can be deduced from its diffusion coefficient. Consistency of diffusion as a power law of mass and Stokes-Einstein formulation is completely fulfilled with the selected compounds of this contribution.
La trichorzianine tavii est un peptide antibiotique compose de 19 residus qui a la propriete de f... more La trichorzianine tavii est un peptide antibiotique compose de 19 residus qui a la propriete de former, dans les bicouches phospholipides, ces canaux dont l'activite depend d'un potentiel trans-membranaire. Afin de tenter de comprendre le mecanisme d'action du peptide sur les membranes, l'etude structurale de tavii en solution dans le methanol et en milieu micellaire (rapport molaire sds/tavii=50) a ete realisee par resonance magnetique nucleaire #1h, #1#3c et #1#5n. Une attribution complete des signaux rmn a ete realisee pour ces trois noyaux. De nombreuses informations conformationnelles ont ete obtenues a l'aide d'experiences de rmn 2d (cosy-dqf, hohaha, noesy, roesy, hmqc, hm3c). Les valeurs de constantes de couplage 3jhn-ch, les coefficients de temperature des groupes nh et cc, les temps de relaxation longitudinaux #1#3c ont ete determines et les effets overhauser nucleaires analyses quantitativement. L'ensemble de ces resultats a permis de realiser la modelisation du peptide. Les conformations de la trichorzianine tavii en solution dans le methanol et en milieu micellaire, determinees par ces methodes, semblent similaires et sont caracterisees par une helice droite rigide, coudee au niveau des residus u#9-s#1#0 et incluant deux tours d'helice 3#1#0 au niveau de la proline et un tour mixte /3#1#0 en partie n-terminale. En presence de sds, tavii apparait aussi structure qu'en solution methanolique. Ces resultats suggerent que le mecanisme d'action de ce peptide sur les membranes met en jeu une reorientation globale de l'helice dans la bicouche et non un mouvement d'une partie du squelette peptidique
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
ABSTRACT Harzianin HK VI, one of the major peptides of the natural mixture of peptaibol antibioti... more ABSTRACT Harzianin HK VI, one of the major peptides of the natural mixture of peptaibol antibiotics biosynthesized by the fungus Trichoderma pseudokoningii, has been isolated by a multi-step chromatography procedure including HPLC. Its sequence was determined by positive ion FAB MS and two-dimensional 1H and 13C NMR experiments (COSY, HOHAHA, HSQC-HOHAHA, HMBC), allowing the location in the sequence of two isoleucines at positions 3 and 4 and of two leucines at positions 7 and 8, which could not be distinguished on the basis of their 1H NMR spin systems. Harzianin HK VI is an 11-residue peptaibol with two Aib-Pro sequences at positions 5–6 and 9–10. From ROESY data and amide temperature coefficients, a β-bend ribbon stabillised by intramolecular hydrogen bonds of the 4→1 type is suggested. Despite the short sequence, harzianin HK VI increases the permeability of liposome bilayers to the same extent as longer 14-residue peptaibols.
from various Trichodenna species, 11to 20-residue amphiphilic peptides have been isolated and the... more from various Trichodenna species, 11to 20-residue amphiphilic peptides have been isolated and their sequences elucidatedjrom FAB MS and NMR data. They are structured in helices, mainly of the a-type. Their membrane activity has been examined by using SUV as model membranes. Introduction Trichoderma are saprophytic and ubiquitous soil fungi with cellulolytic activity and T. viride the type species of the genus, is ranked as one of the most widely distributed of all soU fungi. The genus is characterized by fast growing colonies with conidia more usually green. Rifai (1) distinguished nine species aggrcgated, based on microscopie characters, but the macroscopic features are very similar for most of them. Among the species we have studied were T. harzianum, a very common species described in Africa, America and Europe, T. koningii, also common in Europe, Central-America, India, Tahiti, New-Zealand and lapan and T. longibrachiatum, quite rare, found in France but also in New-Zealand (2)....
La presente invention concerne de nouveaux supports chromatographiques de grande purete a base de... more La presente invention concerne de nouveaux supports chromatographiques de grande purete a base de cyclodextrines natives ou modifiees, liees regioselectivement en position 2, 3 ou 6 a un gel de silice par l'intermediaire d'un bras espaceur contenant un heteroatome. Elle concerne egalement leur procede de fabrication et leurs applications.
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