The Experts below are selected from a list of 222 Experts worldwide ranked by ideXlab platform
Hideki Abe - One of the best experts on this subject based on the ideXlab platform.
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Thermal degradation of environmentally degradable poly(hydroxyalkanoic Acid)s.
Macromolecular bioscience, 2006Co-Authors: Hideki AbeAbstract:Aliphatic polyesters have attracted industrial attention as environmentally degradable thermoplastics to be used for a wide range of applications. Besides intensive studies on the biodegradability of aliphatic polyesters, understanding of the thermal stability has importance for processing, application, and recycling. The details of thermal degradation processes of five types of aliphatic polyesters; namely, poly(L-lactide), poly(3-Hydroxybutyric Acid), poly(4-Hydroxybutyric Acid), poly(delta-valerolactone), and poly(epsilon-caprolactone), were investigated by means of several thermoanalytical techniques under both isothermal and non-isothermal conditions. In this feature article, the thermal degradation behaviors of aliphatic polyesters with different numbers of carbon atoms in the main chain of the monomeric unit are reviewed. In addition, the effects of chain-end structure and residual metal compounds on the thermal degradation processes of aliphatic polyesters consisting of hydroxyalkanoic Acid monomeric units are presented. Schemes of thermal degradation reaction of poly(hydroxyalkanoic Acid)s.
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Thermal degradation behavior of poly(4-Hydroxybutyric Acid)
Polymer Degradation and Stability, 2006Co-Authors: Kang Ju Kim, Yoshiharu Doi, Hideki Abe, David P. MartinAbstract:Abstract Thermal degradation behavior of poly(4-Hydroxybutyric Acid) (P(4HB)) was investigated by thermogravimetric and pyrolysis–gas chromatography mass spectrometric analyses under both isothermal and non-isothermal conditions. Based on the thermogravimetric analysis, it was found that two distinct processes occurred at temperatures below and above 350 °C during the non-isothermal degradation of P(4HB) samples depending on both the molecular weight and the heating rate. From 1 H NMR analysis of the residual P(4HB) molecules after isothermal degradations at different temperatures, it was confirmed that the ω-hydroxyl chain-end was remained unchanged in the residual P(4HB) molecules at temperatures below 300 °C, while the ω-chain-end of P(4HB) molecules was converted to 3-butenoyl units at temperatures above 300 °C. In contrast, the majority of the volatile products evolved during thermal degradation of P(4HB) was γ-butyrolactone regardless of the degradation temperature. From these results, it is concluded that during the thermal degradation of P(4HB), the selective formation of γ-butyrolactone via unzipping reaction from the ω-hydroxyl chain-end predominantly occurs at temperatures below 300 °C. At temperatures above 300 °C, both the cis -elimination reaction of 4HB unit and the formation of cyclic macromolecules of P(4HB) via intramolecular transesterification take place in addition to unzipping reaction from the ω-hydroxyl chain-end. Finally, the primary reaction of thermal degradation of P(4HB) at temperatures above 350 °C progresses by the cyclic rupture via intramolecular transesterification of P(4HB) molecules with a release of γ-butyrolactone as volatile product. Moreover, we carried out the thermal degradation tests for copolymer of 93 mol% of 4HB with 7 mol% of 3-Hydroxybutyric Acid (3HB) to examine the effect of 3HB units on thermal stability of P(4HB).
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Crystalline morphology and thermal properties for random copolyesters of (R)‐3‐Hydroxybutyric Acid with different hydroxyalkanoic groups
Macromolecular Symposia, 2001Co-Authors: Hideki Abe, Yoshiharu DoiAbstract:The solid-state structures and thermal properties of melt-crystallized films of random copolymers of (R)-3-Hydroxybutyric Acid (3HB) with different hydroxyalkanoic Acids such as (R)-3-hydroxypentanoic Acid (3HV), (R)-3-hydroxyhexanoic Acid (3HH), medium-chain-length (R)-3-hydroxyalkanoic Acids (mcl-3HA; C8-C12), 4-Hydroxybutyric Acid (4HB), and 6-hydroxyhexanoic Acid (6HH) were characterized by means of small-angle X-ray scattering, differential scanning calorimetry, and optical microscopy. The randomly distributed second monomer units except for 3HV in copolyesters act as defects of P(3HB) crystal and are excluded from the P(3HB) crystalline lamellae. The lamellar thickness of copolymers decreased with an increase in either the main-chain or the side-chain carbon numbers of second monomer units. In addition, the growth rate of spherulites decreased with an increase in the carbon numbers of second monomer units for copolymers with an identical comonomer composition. These results indicate that the steric bulkiness of second monomer unit affects on the crystallization of 3HB segments in random copolyesters.
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Solid-State Structures and Enzymatic Degradabilities for Melt-Crystallized Films of Copolymers of (R)-3-Hydroxybutyric Acid with Different Hydroxyalkanoic Acids
Macromolecules, 1998Co-Authors: Hideki Abe, Yoshiharu Doi, Hiromichi Aoki, Takashi AkehataAbstract:The films of random copolymers of (R)-3-Hydroxybutyric Acid with different hydroxyalkanoic Acids such as (R)-3-hydroxypentanoic Acid, (R)-3-hydroxyhexanoic Acid, 4-Hydroxybutyric Acid, 6-hydroxyhexanoic Acid, and (S,S)-lactide were prepared by the melt-crystallized method at various crystallization temperatures. The solid-state structures and thermal properties of melt-crystallized films were characterized by means of wide-angle X-ray diffraction, small-angle X-ray scattering, differential scanning calorimetry, optical microscopy, and scanning electron microscopy. Both the long period distance and the lamellar thickness of melt-crystallized polyester films were increased with an increase in the crystallization temperature. The melting temperature of polyester films also increased with an increase in the crystallization temperature. From the relationship between lamellar thickness and melting temperature, it has been concluded that randomly distributed second monomer units except for the (R)-3-hydroxypenta...
C.a.j.m. Jakobs - One of the best experts on this subject based on the ideXlab platform.
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Sedation with 4-Hydroxybutyric Acid: a potential pitfall in the diagnosis of SSADH deficiency.
Journal of inherited metabolic disease, 2004Co-Authors: Nicole I. Wolf, C.a.j.m. Jakobs, Dorothea Haas, Georg F. Hoffmann, Gajja S. Salomons, Ron A. Wevers, Udo F. H. Engelke, Dietz RatingAbstract:Deficiency of succinic semialdehyde dehydrogenase (SSADH) is a rare neurometabolic disorder with accumulation of 4-Hydroxybutyric Acid (4-HBA) as a biochemical hallmark. We present a boy with an unresolved severe neurological disorder and intermittent elevation of 4-HBA in serum and CSF which was later shown to result from iatrogenic administration of 4-HBA for sedation purposes.
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4-Hydroxybutyric Acid and the clinical phenotype of succinic semialdehyde dehydrogenase deficiency, an inborn error of GABA metabolism.
Neuropediatrics, 1998Co-Authors: Kenneth M. Gibson, A. K. Hodson, C. F. Hoffmann, Teodoro Bottiglieri, C.a.j.m. JakobsAbstract:SSADH deficiency, a rare inborn error of human metabolism, disrupts the normal metabolism of the inhibitory neurotransmitter GABA. In response to the defect, physiologic fluids from patients accumulate GHB, a compound with numerous neuromodulatory properties. Clinical and bio-chemical findings in patients are contrasted with existing neuropharmacologic data on GHB in animals and men. We conclude that GHB contributes to the pathogenesis of SSADH deficiency; whether this effect is mediated by GHB, by GABA following metabolic interconversion, or via synergistic mechanisms by both compounds, remains to be determined. An animal model of SSADH deficiency should further define the role of GHB in the pathogenesis of SSADH deficiency, and provide a useful vehicle for the evaluation of new therapeutic intervention.
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Differing clinical presentation of succinic semialdehyde dehydrogenase deficiency in adolescent siblings from Lifu Island, New Caledonia
Journal of inherited metabolic disease, 1997Co-Authors: Kenneth M. Gibson, C.a.j.m. Jakobs, Daniel Rabier, A. E. Doskey, C. MorlatAbstract:Succinic semialdehyde dehydrogenase (SSADH) deficiency (McKusick 271980) is a rare inherited defect in 4-aminobutyric Acid (GABA) metabolism. The primary defect results in the accumulation of succinic semialdehyde, which is reduced to 4-Hydroxybutyric Acid, the biochemical marker for the disease and a compound with neurogenic properties (Jakobs et al 1993; Scriver and Gibson 1995). As the number of identified patients is still small, the clinical phenotype of the disease is not yet fully developed. Most patients, who originate primarily from Northern Europe, Asia and North America, present with varying deficiencies of mental, motor and language development, variably accompanied by hypotonia, ataxia, seizures and ocular or reflex abnormalities (Scriver and Gibson 1995). Unrelated patients have presented with considerable heterogeneity in clinical manifestations. However, the clinical presentation within sibships has been more consistent. We report a differing clinical phenotype of SSADH deficiency in adolescent male and female siblings whose parents had migrated from Fiji to Lifu Island, off the Eastern coast of New Caledonia (France).
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Pre- and postnatal diagnosis of succinic semialdehyde dehydrogenase deficiency using enzyme and metabolite assays.
Journal of inherited metabolic disease, 1994Co-Authors: Kenneth M. Gibson, H. Ogier, C. Baumann, Eva Rossier, Brigitte Vollmer, C.a.j.m. JakobsAbstract:We Report our cumulative experience for the prenatal diagnosis of succinic semialdehyde dehydrogenase (SSADH) deficiency in seven ‘at-risk’ pregnancies from four unrelated families. Prenatal diagnosis was performed by determination of 4-Hydroxybutyric Acid (4-HBA) concentration in amniotic fluid using isotope-dilution gas chromatography-mass spectrometry in conjunction with assay of SSADH activity in biopsied chorionic villus and/or cultured amniocytes. In three of four pregnancies predicted as affected, confirmation was obtained by demonstration of deficient SSADH activity in fetal tissues. Our results suggest that determination of 4-HBA concentration in amniotic fluid combined with enzyme determination in cultured or biopsied tissue represents a reliable method for the prenatal diagnosis of SSADH deficiency.
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Enzymatic and immunological demonstration of normal and defective succinic semialdehyde dehydrogenase activity in fetal brain, liver and kidney.
Journal of inherited metabolic disease, 1993Co-Authors: Ken L. Chambliss, C.a.j.m. Jakobs, C. F. Lee, H. Ogier, Daniel Rabier, Kenneth M. GibsonAbstract:Succinic semialdehyde dehydrogenase (SSADH; EC 1.2. 1.24) deficiency (McKusick 271980) is an inborn error of 4-aminobutyric Acid (GABA) metabolism. The enzymatic defect blocks the oxidation of succinic semialdehyde (SSA) to succinic Acid, resulting in conversion of SSA to 4-Hydroxybutyric Acid (γ-Hydroxybutyric Acid, CHB), which accumulates in patients' physiological fluids. SSADH-deficient patients present with variable retardation of intellectual, motor and speech development, often accompanied by ataxia and hypotonia (Jakobs et al 1993a)
Kenneth M. Gibson - One of the best experts on this subject based on the ideXlab platform.
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4-Hydroxybutyric Acid and the clinical phenotype of succinic semialdehyde dehydrogenase deficiency, an inborn error of GABA metabolism.
Neuropediatrics, 1998Co-Authors: Kenneth M. Gibson, A. K. Hodson, C. F. Hoffmann, Teodoro Bottiglieri, C.a.j.m. JakobsAbstract:SSADH deficiency, a rare inborn error of human metabolism, disrupts the normal metabolism of the inhibitory neurotransmitter GABA. In response to the defect, physiologic fluids from patients accumulate GHB, a compound with numerous neuromodulatory properties. Clinical and bio-chemical findings in patients are contrasted with existing neuropharmacologic data on GHB in animals and men. We conclude that GHB contributes to the pathogenesis of SSADH deficiency; whether this effect is mediated by GHB, by GABA following metabolic interconversion, or via synergistic mechanisms by both compounds, remains to be determined. An animal model of SSADH deficiency should further define the role of GHB in the pathogenesis of SSADH deficiency, and provide a useful vehicle for the evaluation of new therapeutic intervention.
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Differing clinical presentation of succinic semialdehyde dehydrogenase deficiency in adolescent siblings from Lifu Island, New Caledonia
Journal of inherited metabolic disease, 1997Co-Authors: Kenneth M. Gibson, C.a.j.m. Jakobs, Daniel Rabier, A. E. Doskey, C. MorlatAbstract:Succinic semialdehyde dehydrogenase (SSADH) deficiency (McKusick 271980) is a rare inherited defect in 4-aminobutyric Acid (GABA) metabolism. The primary defect results in the accumulation of succinic semialdehyde, which is reduced to 4-Hydroxybutyric Acid, the biochemical marker for the disease and a compound with neurogenic properties (Jakobs et al 1993; Scriver and Gibson 1995). As the number of identified patients is still small, the clinical phenotype of the disease is not yet fully developed. Most patients, who originate primarily from Northern Europe, Asia and North America, present with varying deficiencies of mental, motor and language development, variably accompanied by hypotonia, ataxia, seizures and ocular or reflex abnormalities (Scriver and Gibson 1995). Unrelated patients have presented with considerable heterogeneity in clinical manifestations. However, the clinical presentation within sibships has been more consistent. We report a differing clinical phenotype of SSADH deficiency in adolescent male and female siblings whose parents had migrated from Fiji to Lifu Island, off the Eastern coast of New Caledonia (France).
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Pre- and postnatal diagnosis of succinic semialdehyde dehydrogenase deficiency using enzyme and metabolite assays.
Journal of inherited metabolic disease, 1994Co-Authors: Kenneth M. Gibson, H. Ogier, C. Baumann, Eva Rossier, Brigitte Vollmer, C.a.j.m. JakobsAbstract:We Report our cumulative experience for the prenatal diagnosis of succinic semialdehyde dehydrogenase (SSADH) deficiency in seven ‘at-risk’ pregnancies from four unrelated families. Prenatal diagnosis was performed by determination of 4-Hydroxybutyric Acid (4-HBA) concentration in amniotic fluid using isotope-dilution gas chromatography-mass spectrometry in conjunction with assay of SSADH activity in biopsied chorionic villus and/or cultured amniocytes. In three of four pregnancies predicted as affected, confirmation was obtained by demonstration of deficient SSADH activity in fetal tissues. Our results suggest that determination of 4-HBA concentration in amniotic fluid combined with enzyme determination in cultured or biopsied tissue represents a reliable method for the prenatal diagnosis of SSADH deficiency.
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Enzymatic and immunological demonstration of normal and defective succinic semialdehyde dehydrogenase activity in fetal brain, liver and kidney.
Journal of inherited metabolic disease, 1993Co-Authors: Ken L. Chambliss, C.a.j.m. Jakobs, C. F. Lee, H. Ogier, Daniel Rabier, Kenneth M. GibsonAbstract:Succinic semialdehyde dehydrogenase (SSADH; EC 1.2. 1.24) deficiency (McKusick 271980) is an inborn error of 4-aminobutyric Acid (GABA) metabolism. The enzymatic defect blocks the oxidation of succinic semialdehyde (SSA) to succinic Acid, resulting in conversion of SSA to 4-Hydroxybutyric Acid (γ-Hydroxybutyric Acid, CHB), which accumulates in patients' physiological fluids. SSADH-deficient patients present with variable retardation of intellectual, motor and speech development, often accompanied by ataxia and hypotonia (Jakobs et al 1993a)
Yoshiharu Doi - One of the best experts on this subject based on the ideXlab platform.
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Thermal degradation behavior of poly(4-Hydroxybutyric Acid)
Polymer Degradation and Stability, 2006Co-Authors: Kang Ju Kim, Yoshiharu Doi, Hideki Abe, David P. MartinAbstract:Abstract Thermal degradation behavior of poly(4-Hydroxybutyric Acid) (P(4HB)) was investigated by thermogravimetric and pyrolysis–gas chromatography mass spectrometric analyses under both isothermal and non-isothermal conditions. Based on the thermogravimetric analysis, it was found that two distinct processes occurred at temperatures below and above 350 °C during the non-isothermal degradation of P(4HB) samples depending on both the molecular weight and the heating rate. From 1 H NMR analysis of the residual P(4HB) molecules after isothermal degradations at different temperatures, it was confirmed that the ω-hydroxyl chain-end was remained unchanged in the residual P(4HB) molecules at temperatures below 300 °C, while the ω-chain-end of P(4HB) molecules was converted to 3-butenoyl units at temperatures above 300 °C. In contrast, the majority of the volatile products evolved during thermal degradation of P(4HB) was γ-butyrolactone regardless of the degradation temperature. From these results, it is concluded that during the thermal degradation of P(4HB), the selective formation of γ-butyrolactone via unzipping reaction from the ω-hydroxyl chain-end predominantly occurs at temperatures below 300 °C. At temperatures above 300 °C, both the cis -elimination reaction of 4HB unit and the formation of cyclic macromolecules of P(4HB) via intramolecular transesterification take place in addition to unzipping reaction from the ω-hydroxyl chain-end. Finally, the primary reaction of thermal degradation of P(4HB) at temperatures above 350 °C progresses by the cyclic rupture via intramolecular transesterification of P(4HB) molecules with a release of γ-butyrolactone as volatile product. Moreover, we carried out the thermal degradation tests for copolymer of 93 mol% of 4HB with 7 mol% of 3-Hydroxybutyric Acid (3HB) to examine the effect of 3HB units on thermal stability of P(4HB).
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Crystalline morphology and thermal properties for random copolyesters of (R)‐3‐Hydroxybutyric Acid with different hydroxyalkanoic groups
Macromolecular Symposia, 2001Co-Authors: Hideki Abe, Yoshiharu DoiAbstract:The solid-state structures and thermal properties of melt-crystallized films of random copolymers of (R)-3-Hydroxybutyric Acid (3HB) with different hydroxyalkanoic Acids such as (R)-3-hydroxypentanoic Acid (3HV), (R)-3-hydroxyhexanoic Acid (3HH), medium-chain-length (R)-3-hydroxyalkanoic Acids (mcl-3HA; C8-C12), 4-Hydroxybutyric Acid (4HB), and 6-hydroxyhexanoic Acid (6HH) were characterized by means of small-angle X-ray scattering, differential scanning calorimetry, and optical microscopy. The randomly distributed second monomer units except for 3HV in copolyesters act as defects of P(3HB) crystal and are excluded from the P(3HB) crystalline lamellae. The lamellar thickness of copolymers decreased with an increase in either the main-chain or the side-chain carbon numbers of second monomer units. In addition, the growth rate of spherulites decreased with an increase in the carbon numbers of second monomer units for copolymers with an identical comonomer composition. These results indicate that the steric bulkiness of second monomer unit affects on the crystallization of 3HB segments in random copolyesters.
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Solid-State Structures and Enzymatic Degradabilities for Melt-Crystallized Films of Copolymers of (R)-3-Hydroxybutyric Acid with Different Hydroxyalkanoic Acids
Macromolecules, 1998Co-Authors: Hideki Abe, Yoshiharu Doi, Hiromichi Aoki, Takashi AkehataAbstract:The films of random copolymers of (R)-3-Hydroxybutyric Acid with different hydroxyalkanoic Acids such as (R)-3-hydroxypentanoic Acid, (R)-3-hydroxyhexanoic Acid, 4-Hydroxybutyric Acid, 6-hydroxyhexanoic Acid, and (S,S)-lactide were prepared by the melt-crystallized method at various crystallization temperatures. The solid-state structures and thermal properties of melt-crystallized films were characterized by means of wide-angle X-ray diffraction, small-angle X-ray scattering, differential scanning calorimetry, optical microscopy, and scanning electron microscopy. Both the long period distance and the lamellar thickness of melt-crystallized polyester films were increased with an increase in the crystallization temperature. The melting temperature of polyester films also increased with an increase in the crystallization temperature. From the relationship between lamellar thickness and melting temperature, it has been concluded that randomly distributed second monomer units except for the (R)-3-hydroxypenta...
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microbial synthesis and properties of poly 3 hydroxybutyrate co 4 hydroxybutyrate in comamonas Acidovorans
International Journal of Biological Macromolecules, 1994Co-Authors: Yuji Saito, Yoshiharu DoiAbstract:Comamonas Acidovorans DS-17 was isolated from activated sludge and found to produce copolymers of 3-hydroxybutyrate (3HB) and 4-hydroxybutyrate (4HB) at 30°C under growth-limited conditions. When 1,4-butanediol or 4-Hydroxybutyric Acid was used as the sole carbon source, a P(4HB) homopolymer was produced. Random copolymers of 3HB and 4HB units were produced on the addition of glucose or 3-Hydroxybutyric Acid to the culture solution of 4-Hydroxybutyric Acid. The physical properties of P(3HB-co-4HB) copolyesters with high 4HB fractions (64–100 mol%) were investigated. The copolyester films with high 4HB fractions exhibited the characteristics of a thermoplastic elastomer, and the tensile strength increased from 17 to 104 MPa as the 4HB fraction was increased from 64 to 100 mol%. The biodegradabilities of P(3HB-co-4HB) films were studied in aqueous solutions of extracellular polyhydroxybutyrate (PHB) depolymerase from Alcaligenes faecalis or of lipase from Rhizopus delemer. The erosion rate of P(3HB-co-4HB) films by PHB depolymerase decreased as the 4HB fraction in copolyester was increased from 64 to 100 mol%. In contrast, the erosion rate of films by lipase increased with the 4HB fraction.
Yoshio Inoue - One of the best experts on this subject based on the ideXlab platform.
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Comonomer unit composition and thermal properties of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)s biosynthesized by Ralstonia eutropha.
Biomacromolecules, 2001Co-Authors: Kazuki Ishida, Yi Wang, Yoshio InoueAbstract:A series of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)s [P(3HB-co-4HB)s] with different 4HB content, biosynthesized by Ralstonia eutropha H16 with mixed carbon sources of 4-Hydroxybutyric Acid (4HBA) and butyric Acid, were fractionated by solvent/nonsolvent fractionation into copolyester fractions with different 4HB content and narrower compositional distribution. The fractions obtained were classified into two groups, 3HB- and 4HB-rich P(3HB-co-4HB)s. The thermal properties were investigated for these fractionated copolyesters. With increasing 4HB content, the melting temperature at first decreased while 3HB content was rich, and then increased while 4HB content was rich. The glass transition temperature decreased linearly with increasing 4HB content. The 4HB-rich P(3HB-co-4HB) was found to be immiscible with the 3HB-rich P(3HB-co-4HB), as two glass transitions corresponding to those of respective P(3HB-co-4HB)s were observed by DSC. It was concluded that as-produced bacterial P(3HB-co-4HB) samples use...
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Solid-state structure and properties of bacterial copolyesters
Journal of Molecular Structure, 1998Co-Authors: Yoshio InoueAbstract:Abstract In this review article, the solid-state structures and properties of some bacterially synthesized copolyesters, including poly(3-Hydroxybutyric Acid-co-3-hydroxyvaleric Acid), poly(3-Hydroxybutyric Acid-co-4-Hydroxybutyric Acid) and poly(3-Hydroxybutyric Acid-co-3-hydroxypropionic Acid), are described based mainly on our results obtained by solid-state high-resolution 13 C NMR, differential scanning calorimetry as well as molecular mechanics calculation methods. For the binary copolyesters of 3-Hydroxybutyric Acid, it was found that both 3-Hydroxybutyric Acid and 3-hydroxyvaleric Acid units can cocrystallize in the same crystalline lattice, but the 3-Hydroxybutyric Acid unit cannot cocrystallize with the 4-Hydroxybutyric Acid and the 3-hydroxypropionic Acid units.
