Biomedical subjects

Yi Wang

Publications and source records attributed to Yi Wang.

At least 307 records · Page 17Linked to original sources

PubMed2002

[Transarterial embolization for hemorrhage due to spontaneous rupture in hepatocellular carcinoma].

OBJECTIVE: To evaluate the efficacy of transarterial embolization (TAE) for intraperitoneal hemorrhage due to spontaneous rupture in hepatocellular carcinoma (HCC). METHODS: Fourty-two patients with ruptured HCC were divided into 4 groups according to the type of their previous treatment: Group A-TAE followed by elective hepatectomy 15, Group B- TAE alone 11, Group C-emergency operation 6 and group D-medical conservative management 10. RESULTS: Celiac arteriography done before the present treatment showed extravasation of contrast material in 7 (26.9%) of the 26 patients in group A and B, and hypervascular tumor was observed in the rest. The hemostasis success rate of group A, B and C were 100%, which were much higher than that of group D (40%) (P < 0.05). The in-hospital mortality rates of group A, B and C were 0, 3.8% and 16.7% (P > 0.05), which were much lower than that of group D (80%) (P < 0.01). The 1-year survival rate of group A (76.3%) was higher than those in groups B (47.5%) and C (43.7%) (P < 0.05). There was no 1-year survivor in group D. CONCLUSION: Transarterial embolization is safe and effective for hemorrhage due to spontaneous rupture in hepatocellular carcinoma. For resectable lesions, TAE is a preferential treatment to be given first, then followed by elective hepatectomy.

Adult↗

PubMed2002

[Sequence difference of ribosomal DNA second internal transcribed spacer in Anopheles minimus in different localities].

OBJECTIVE: To compare the sequence difference of the ribosomal DNA second internal transcribed spacer (ITS2) in Anopheles minimus from Yunnan, Hainan, Guangxi of China and from Thailand. METHODS: Single mosquito's legs were digested to extract DNA; the rDNA-ITS2 region was amplified by specific primers and the PCR products were purified, sequenced and analysed. RESULTS: Two different kinds of ITS2 sequences, temporarily named as An. minimus A and An. minimus C, were found in this study. The length and GC contents of ITS2 region in species A and species C are 481 bp, 54.04% and 483 bp, 54.23%, respectively. Two species differed by 5.8% in the ITS2 sequences owing to 22 fixed nucleotide substitutions and indels. CONCLUSION: Two cryptic species, An. minimus A and An. minimus C, were found in the research localities.

Animals↗

PubMed2002

[Study on low density lipoprotein receptor of adult Schistosoma japonicum].

OBJECTIVE: To provide a theoretical basis for the study of vaccines against Schistosoma japonicum, the receptor for human LDL in the tegument of adult Schistosoma japonicum was investigated. METHODS: Proteins existed in adult Schistosoma japonicum membrane were extracted by Triton X-100 and purified through reverse-phase high performance liquid chromatography (HPLC), and the main protein peaks were then collected separately. 125I-LDL of human plasma as the ligand, through the radioautography and radioligand binding assay, the protein which can bind human serum 125I-LDL specifically was identified. The molecular weight and IEF were detected by SDS-PAGE. RESULTS: According to the radioautography and radioligand binding assay, a protein with retention time of 10.5 min was proved to be able to bind human serum 125I-LDL specifically. SDS-PAGE revealed that the molecular weight of the purified protein is 60-65 kDa, and its IEF is 6.7. CONCLUSION: LDL binding protein may exist on the surface of both male and female adult Schistosoma japonicum with the function of obtaining cholesterol from host circulating system.

Animals↗

PubMed2002

[Effect of Angelica sinensis polysaccharides on lymphocyte proliferation and induction of IFN-gamma].

AIM: To study the effect of Angelica sinsensis polysaccharides on lymphocyte proliferation and induction of IFN-gamma. METHODS: Angelica sinensis polysaccharides(AP) were separated into AP-I, AP-II, AP-III and AP-IV by alcohol deposition with different concentration. The radioactivities of [3H]-TdR uptake by lymphocyte were used to determine the ability of lymphocyte. The bioactivity of IFN-gamma was measured by violet crystalline dying. RESULTS: AP-IV was found to be composed of Ara and Glu in the ratio of 0.99:6.47, the molecular weight was estimated to be 5,600. AP-I and AP-II 100 mg.kg-1 i.p. were found to significantly augment mice splenocyte proliferation, release IFN-gamma and increase IFN-gamma bioactivity. 50 micrograms.mL-1 AP-I, AP-II and AP-III were shown to enhance the proliferative response of the mouse spleen lymphocytes in vitro. CONCLUSION: AP-I and AP-II showed higher immunoactivity than AP-III, AP-IV had no effect.

Angelica sinensis↗

PubMed2002

Simultaneous operative treatment of patients with primary liver cancer associated with portal hypertension.

OBJECTIVE: To explore the operative procedure for patients with primary liver cancer associated with portal hyper tension (PLCPH). METHODS: We analyzed retrospectively the effect of operative procedure for 9 patients with PLCPH complicated by severe esophageal varicosity and hypersplenism. RESULTS: All patients underwent liver resection and pericardiac devascularization with splenectomy. Of the 9 patients, 2 died from liver cancer recurrence separately 13 and 16 months after operation, and 1 died from massive duodenal ulcer bleeding and multiple organs failure. Six patients survived 3, 4, 8, 10, 12 and 25 months after operation. CONCLUSIONS: The patients with PLCPH undergoing simultaneous operation could acquire curative effect as compared with those who underwent liver resection. This operation is beneficial to the patients with poor liver function.

Adult↗

PubMed2002

Influence of preoperative transcatheter arterial chemoembolization on liver resection in patients with resectable hepatocellular carcinoma.

OBJECTIVE: To assess the influence of preoperative transcatheter arterial chemoembolization (TACE) on liver resection in patients with resectable hepatocellular carcinoma (HCC). METHODS: Of 126 patients with resectable HCC, 62 received preoperative TACE (TACE group) and the remaining 64 patients were selected as controls (non-TACE group). Perioperative risk factors including liver function alteration, mean blood loss during operation, mean time of clamping the porta hepatis, length of operation, postoperative abdominal drainage at day 1, 2 and 3, morbidity and mortality were compared between the two groups. RESULTS: Neither significant difference in liver function alteration nor mortality was observed between the two groups. More severe hepatic cirrhosis, longer operation time, more blood loss and postoperative abdominal drainage were noted in the TACE group than in the non-TACE group. There was no significant difference in postoperative morbidity between the two groups. CONCLUSIONS: Preoperative TACE for resectable HCC increases surgical difficulty and risk, and therefore should be considered prudently according to the individuality of patients.

Abdomen↗

PubMed2002

Intermittent portal triad clamping in resection of liver tumors involving the hepatocaval confluence.

OBJECTIVE: To review our experience in and the results of resecting liver tumors involving the hepatocaval confluence under intermittent portal triad clamping (PTC). METHODS: Sixty-eight consecutive patients with liver tumors involving the hepatocaval confluence underwent hepatectomies with liver parenchymal transections under intermittent PTC. RESULTS: All the tumors were successfully resected under PTC, except for one in which the infrahepatic inferior vena cava was concomitantly occluded in addition to PTC. There was neither operative death nor uncontrollable massive bleeding or air embolism occurred in our patients. The bleedings from the main and short hepatic veins and right adrenal veins were properly managed during the operation, with a mean intraoperative blood loss of 1400 ml. Of the 68 tumors resected, 65 were hepatocellular carcinomas (HCC). Their 1-, 2-, 3- and 4-year survival rates were 64.11%, 52.82%, 44.90% and 36.98%, respectively, and the patients with HCC with capsules survived significantly longer than those with HCC without capsules. CONCLUSIONS: The liver tumors involving the hepatocaval confluence could be safely resected simply under PTC, without routine use of total hepatic vascular exclusion. As for HCCs in this area, the tumor with capsule is a better indicator for surgical resection than that without capsule.

Adult↗

PubMed2002

Effect of seawater soaking on explosive cornea injury.

OBJECTIVE: To observe the changes in corneal tissue after explosive corneal injury and the effect of seawater soaking on the healing of cornea after explosive injury with the help of optical microscope. METHODS: Make 10 similar explosive injury models of rabbit's eyeball using 10 adult grey rabbits. For each rabbit, both eyes are artificially injured through explosion; its right eye is the comparison eye and after the injury the left eye is soaked in seawater for 30 minutes. (Conduct slit lamp examinations, fluorescein dyeing, and ultrasonic cornea thickness metering on the corneas at intervals, that is, before the injury, 1, 2, 3, 4, 5, 7, 9, 12, 15 days after the injury respectively. Examine the corneas under the optical microscope and make comparisons. RESULTS: The corneal thickness of the experiment eye becomes apparently thicker than that of the comparison eye after the injury. The corneal clouding of the former apparently aggravates compared with the latter. The healing of corneal epithelium in the injured eye is slower compared with that in the comparison eye. Comparative examination under the optical microscope shows: after the injury, the corneal tissue of the experiment eye changes distinctly, its healing is delayed and the vascularization degree becomes high in corneal stroma. CONCLUSION: Scars and vascularization of various degrees will appear in corneal stroma after explosive injuries. Seawater soaking will have bad effects on the healing of the cornea injured in explosions.

Animals↗

PubMedDate not supplied

Simultaneous determination of ginsenosides in Panax ginseng with different growth ages using high-performance liquid chromatography-mass spectrometry.

The contents of ginsenosides in Panax ginseng not only vary in different parts of the root, but also exhibit yearly variation. In this study, an HPLC-MS method was established in order to simultaneously analyse ginsenosides Rb1, Rb2, Rb3, Rc, Rd, Re, Rf, Rg1 and Rg2. The concentration of ginsenosides in the tap root and root fibre were compared and the yearly variations of nine ginsenosides elucidated. The results indicate that the total content of ginsenosides in the main root and the root fibre both attain a maximum level in the fourth year of growth, although the amount in the former is much higher than in the latter. The variation in the content of ginsenosides during a 2-6 year period suggests that cultivated P. Ginseng can be harvested after the fourth year. The current results will provide useful information for the quality control and good agricultural practice farming of ginseng.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Influence of two transfectors on delivery of 99mTc antisense DNA in tumor-bearing mice.

PURPOSE: The aim of the study is to determine whether delivery into tumor cells in vivo of a 99mTc-labeled antisense phosphorothioate DNA targeting the mdr1 mRNA improves after electrostatic complexation with the transmembrane transfector (TF) carriers Neophectin or jetPEI as was observed by us in vitro. METHODS: The biodistribution of the labeled antisense DNA before and after complexation with either TF was determined in nude mice bearing KB-G2 (Pgp++) tumors. RESULTS: Complexation with either TF resulted in significantly higher background radioactivity levels in almost all normal tissues and modest improvement in tumor accumulation at best. The tumor accumulation was lower compared to naked at six hours (0.34 and 0.23 vs. 0.40% ID/g) and modestly higher at 24-28 hours (0.15 and 0.15 vs. 0.12% ID/g) for Neophectin and jetPEI, respectively. That blood was less than 0.18% ID/g for both TFs even at six hours suggests that tumor accumulations may have suffered from rapid blood clearance. CONCLUSION: The results of this investigation show that because of the unfavorable pharmacokinetics of radiolabeled phosphorothioate DNAs when electrostatically complexed to jetPEI or Neophectin, neither TF appears to be useful in vivo despite favorable results in vitro. Future studies will devote greater consideration to the relative rates of tumor accumulation and blood clearance.

Animals↗

PubMedDate not supplied

Improved delivery in cell culture of radiolabeled antisense DNAs by duplex formation.

PURPOSE: Delivery remains an unresolved problem in applications requiring intravenous administration of DNAs. Recently improved antisense translation interruption in cells was reported for an antisense (AS) oligomer as a duplex compared to singlet AS oligomer presumably because of improved delivery. The unstable phosphodiester backbone of the sense (S) oligomer and its shorter chain length apparently encouraged intracellular dissociation and release of the AS oligomer. We have investigated the mechanism involved to evaluate whether the approach may be useful for antisense radionuclide imaging. PROCEDURES: Duplexes were formed between an AS phosphorothioate DNA against the mdr1 mRNA and the uniform phoshorothioate or uniform phosphodiester sense (S) DNAs with either four or six mismatches. RESULTS: Accumulations in KB-G2 (Pgp++) cells of radiolabeled AS DNA as duplex accumulated threefold higher compared to singlet. Accumulation was still antisense as shown by reduced accumulations with the radiolabel on the S DNA. However, the DNA backbone had no clear influence on accumulations. CONCLUSIONS: Targeting of mRNAs with radiolabeled AS DNAs may be improved in cell culture if duplexed with an S DNA engineered for low hybridization affinity to encourage dissociation in the presence of the target mRNA.

Cell Culture Techniques↗

PubMedDate not supplied

Optical pretargeting of tumor with fluorescent MORF oligomers.

OBJECTIVE: Pretargeting with radioactivity has significantly improved tumor to normal tissue radioactivity ratios over conventional antibody imaging in both animal studies and clinical trials. This laboratory is investigating DNA analogues such as phosphorodiamidate morpholinos (MORFs) for pretargeting using technetium-99m ((99m)Tc) for detection. However, the unique properties of fluorescence activation and quenching combined with oligomers with their unique properties of hybridization may be particularly useful when used together for pretargeting with optical detection. The use of linear fluorophore-conjugated oligomer duplexes have been little used in animals, and to our knowledge, have not previously been considered for pretargeting applications. METHODS: A MORF/cDNA pair was selected such that when hybridized, the fluorescence of the Cy5.5-conjugated 25 mer MORF (Cy5.5-MORF25) is inhibited with a BHQ3-conjugated 18 mer complementary DNA (BHQ3-cDNA18). The short BHQ3-cDNA18 was selected to dissociate in the presence of a long cMORF25 in the pretargeted tumor, thus releasing the inhibitor from the Cy5.5 emitter. In this manner, the Cy5.5 fluorescence will be inhibited everywhere but in the target. The dissociation was first examined in vitro by adding the duplex to the cMORF25 both in solution and immobilized on polystyrene microspheres and by surface plasmon resonance (SPR). Thereafter, biotinylated cMORF25 immobilized on streptavidin polystyrene microspheres were administered intramuscularly in one thigh of hairless SKH-1 mice as target while an identical weight of the identical microspheres but without the cMORF25 was administered in the contralateral thigh as control. The animals then received IV the Cy5.5-MORF25/BHQ3-cDNA18 duplex or equal molar dosage of single-chain Cy5.5-MORF25 and were imaged. RESULTS: The SPR studies showed that the immobilized cDNA18 rapidly captured the flowing MORF25 to provide a duplex with a slow dissociation rate constant. Furthermore, when cMORF25 was next allowed to flow over the now immobilized duplex, the cDNA18 was unable to prevent dissociation of the heteroduplex and the formation and release of the cMORF25-MORF25 homoduplex. Images of animals obtained soon after receiving the Cy5.5-MORF25 singlet showed intense whole body fluorescence obscuring the target thigh. However, only 5 minutes after receiving the Cy5.5-MORF25/BHQ3-cDNA18 duplex, the target thigh was clearly visible along with only the kidneys. CONCLUSIONS: This first study of optical pretargeting provides a proof of concept that oligomer pretargeting found to be useful with radioactivity detection is applicable with fluorescent detection as well. In addition, our results demonstrate that by using linear oligomers for optical pretargeting, chain lengths (and base sequences) may be manipulated to provide duplexes with stabilities and fluorescence inhibition optimized for pretargeting and other in vivo applications of optical imaging.

Animals↗

PubMedDate not supplied

Accuracy of radionuclide ventriculography assessed by magnetic resonance imaging in patients with abnormal left ventricles.

BACKGROUND: We compared gated blood pool single photon emission computed tomography (SPECT) (GBPS), planar gated blood pool imaging (planar GBP), and cardiac magnetic resonance (CMR) measurements of left ventricular (LV) end-diastolic volume (EDV) and ejection fraction (EF) in patients with abnormal left ventricles. METHODS AND RESULTS: LV functional parameters were measured for 40 subjects (age, 59 +/- 13 years; 85% male) by GBPS, planar GBP, and CMR. GBPS data were analyzed by use of count-threshold software (BP-SPECT) and surface gradient software (QBS). Limits of agreement with CMR for EF were -5% to +18%, -15% to +14%, and -15% to +16% for BP-SPECT, QBS, and planar GBP, respectively. However, limits of agreement with CMR for LV EDV were wide by both GBPS methods: -118 mL to +55 mL and -143 mL to +22 mL for BP-SPECT and QBS, respectively. Bland-Altman reproducibility limits for EF were -9% to +8%, -6% to +9%, and -7% to +7% by BP-SPECT, QBS, and planar GBP, respectively, and those for EDV were -46 mL to +48 mL and -31 mL to +35 mL by BP-SPECT and QBS, respectively. CONCLUSION: GBPS LV EF measurements agree with measurements by CMR and are as reproducible as planar GBP measurements. However, wide limits of agreement of radionuclide versus CMR values suggest that caution must be applied in interpreting GBPS LV volume results, especially for patients with markedly abnormal left ventricles.

Female↗

PubMedDate not supplied

Radiometal-labeled peptide-PNA conjugates for targeting bcl-2 expression: preparation, characterization, and in vitro mRNA binding.

A new antisense peptide-peptide nucleic acid (peptide-PNA) conjugate, designed for targeting bcl-2 expression, has been radiolabeled, characterized, and evaluated for bcl-2 mRNA binding in a cell-free system. A PNA complementary to the first six codons of the bcl-2 gene was synthesized by standard solid-phase Fmoc chemistry and conjugated to a new derivative of 1,4,7,10-tetraazacyclododecane-N,N',N",N'"-tetraacetic acid (DOTA) that allows macrocyclic radiometal chelates to be incorporated into any sequence position of a peptide-PNA conjugate. The DOTA-PNA conjugate was then coupled to a membrane-permeating transduction peptide, PTD-4, designed for intracellular delivery of the radiolabeled PNA. The conjugate was characterized by HPLC and ESI-MS and labeled with (111)In and (90)Y to high specific activities (>1000 Ci/mmol) with high radiochemical purity. Northern blot analysis showed that (90)Y-PTD-4-K(DOTA)-anti-bcl-2-PNA bound specifically to as little as 50 fmol of bcl-2 mRNA, a result equivalent to that obtained with the analogous (32)P-labeled DNA antisense oligonucleotide. Thus, the mRNA targeting properties of (111)In- and (90)Y-PTD-4-K(DOTA)-anti-bcl-2-PNA demonstrate potential for diagnostic imaging and targeted radiotherapy applications in bcl-2-positive cancers.

Antineoplastic Agents↗

PubMedDate not supplied

Synthesis of radiometal-labeled and fluorescent cell-permeating peptide-PNA conjugates for targeting the bcl-2 proto-oncogene.

The B-cell lymphoma/leukemia-2 (bcl-2) proto-oncogene has been associated with the transformation of benign lesions to malignancy, disease progression, poor prognosis, reduced survival, and development of resistance to radiation and chemotherapy in many types of cancer. The objective of this work was to synthesize an antisense peptide nucleic acid (PNA) complementary to the first six codons of the bcl-2 open reading frame, conjugated to a membrane-permeating peptide for intracellular delivery, and modified with a bifunctional chelating agent for targeting imaging and therapeutic radiometals to tumors overexpressing bcl-2. Four peptide-PNA constructs were synthesized by a combination of manual and automated stepwise elongation techniques, including bcl-2 antisense conjugates and nonsense conjugates with no complementarity to any known mammalian gene or DNA sequence. The PNA sequences were synthesized manually by solid-phase 9-fluorenylmethoxycarbonyl (Fmoc) techniques. Then a fully protected lysine monomer, modified with 1,4,7,10-tetraazacyclododecane-N,N',N'',N'"-tetraacetic acid (DOTA) for radiometal chelation, was coupled manually to each PNA sequence. Synthesis of the DOTA-PNA conjugates was followed by automated elongation with a peptide sequence (PTD-4-glycine, PTD-4-G), known to mediate cellular internalization of impermeable effector molecules, or its retro-inverso analogue (ri-PTD-4-G). Preparation of the four conjugates required an innovative synthetic strategy, using mild acid conditions to generate hydrophobic, partially deprotected intermediates. These intermediates were purified by semipreparative reversed-phase HPLC and completely deprotected to yield pure peptide-PNA conjugates in 6% to 9% overall yield. Using modifications of this synthetic strategy, the ri-PTD-4-G conjugate of bcl-2 antisense PNA was prepared using a lysine derivative of tetramethylrhodamine (TMR) for fluorescence microscopy. Plasma stability studies showed that (111)In-DOTA-labeled ri-PTD-4-G-anti-bcl-2 PNA was stable for 168 h at 37 degrees C, unlike the conjugate containing the parent peptide sequence. Scanning confocal fluorescence microscopy of TMR-labeled ri-PTD-4-G-anti-bcl-2 PNA in Raji lymphoma cells demonstrated that the retro-inverso peptide was active in membrane permeation and mediated cellular internalization of the antisense PNA into the cytoplasm, where high concentrations of bcl-2 mRNA are expected to be present.

Antineoplastic Agents↗

PubMedDate not supplied

Enzymatic hydrolysis of bacterial poly(3-hydroxybutyrate-co-3-hydroxypropionate)s by poly(3-hydroxyalkanoate) depolymerase from Acidovorax Sp. TP4.

Enzymatic degradability has been investigated for a series of bacterial poly(3-hydroxybutyrate-co-3-hydroxypropionate)s (P(3HB-co-3HP)s) with 3-hydroxypropionate (3HP) unit contents from 11 to 86 mol % as well as poly(3-hydroxybutyrate) (P(3HB)) and chemosynthesized poly(3-hydroxypropionate) (P(3HP)). The behavior of degradation by two types of extracellular poly(3-hydroxyalkanoate) (PHA) depolymerases purified from Ralstonia pikettii T1 and Acidovorax Sp. TP4, defined respectively as PHA depolymerase types I and II according to the position of the lipase box in the catalytic domain, were compared in relation to the thermal properties and crystalline structures of the PHA samples elucidated by differential scanning calorimetry and wide-angle X-ray diffraction. The degradation products were characterized by high-performance liquid chromatography and one- (1D) and two-dimension (2D) (1)H NMR spectroscopy. It was found that the PHA depolymerase of Acidovorax Sp. TP4 showed degradation behavior different from that shown by depolymerase of R. pikettii T1. PHA depolymerase from Acidovorax Sp. TP4 degraded the P(3HB-co-3HP) films with lower crystallinity in higher rates than those with higher crystallinity, no matter what kinds of crystalline structures they formed. In contrast, PHA depolymerase from R. pikettii T1 degraded P(3HB-co-3HP) films forming P(3HB) crystalline structure in higher rates than those forming P(3HP)s. The increase in amorphous nature of the P(3HB-co-3HP) films with P(3HB)-homopolymer-like crystalline structure increases and then decreases the rate of degradation by depolymerase from R. pikettii T1. The 3-hydroxybutyrate (3HB) monomer was produced as a major product by the hydrolysis of P(3HB) film by PHA depolymerase from Acidovorax Sp. TP4. The P(3HB-co-3HP) films could be degraded into 3HB and 3-hydroxypropionate (3HP) monomer at last, indicating that the catalytic domain of the enzyme recognized at least two monomeric units as substrates. While the PHA depolymerase from R. pikettii T1 hydrolyzed P(3HB) film into 3HB dimer as a major product, and the catalytic domain recognized at least three monomeric units. The degradation behavior of P(3HB-co-3HP) films by the PHA depolymerase of Acidovorax Sp. TP4 could be distinguished from that by the depolymerase of R. pikettii T1.

Betaproteobacteria↗

PubMedDate not supplied

Enzymatic hydrolysis of chemosynthesized atactic poly(3-hydroxybutyrate) by poly(3-hydroxyalkanoate) depolymerase from Acidovorax Sp. TP4 and Ralstonia pickettii T1.

The enzymatic degradability of chemosynthesized atactic poly([R,S]-3-hydroxybutyrate) [a-P(3HB)] by two types of extracellular poly(3-hydroxyalkanoate) (PHA) depolymerases purified from Ralstonia pickettii T1 (PhaZ(ral)) and Acidovorax Sp. TP4 (PhaZ(aci)), defined respectively as PHA depolymerase types I and II according to the position of the lipase box in the catalytic domain, were studied. The enzymatic degradation of a-P(3HB) by PhaZ(aci) depolymerase was confirmed from the results of weight loss and the scanning electron micrographs. The degradation products were characterized by one- and two-dimension (1)H NMR spectroscopy. It was found that a-P(3HB) could be degraded into monomer, dimer, and trimer by PhaZ(aci) depolymerase at temperatures ranging from 4 to 20 degrees C, while a-P(3HB) could hardly be hydrolyzed by PhaZ(ral) depolymerase in the same temperature range. These results suggested that the chemosynthesized a-P(3HB) could be degraded in the pure state by natural PHA depolymerase.

Biodegradation, Environmental↗

PubMedDate not supplied

Studies on comonomer compositional distribution of bacterial poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)s and thermal characteristics of their factions.

The comonomer-unit compositional distributions have been investigated for bacterial poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HH)] samples with 3HH unit content of 13.8, 18.0, 22.0, and 54.0 mol %. They were comonomer compositionally fractionated using chloroform/n-heptane mixed solvent at ambient temperature. The fractionation of P(3HB-co-18.0 mol %3HH) and P(3HB-co-22.0 mol % 3HH), which could not be carried out effectively at room temperature, were refractionated at 70 degrees C in the mixed solvent. Fractions with different 3HH unit content in a wide range (from 4.4 to 80.7 mol %) were obtained. By use of these fractions with narrow compositional distribution, the comonomer composition dependence of thermal properties was investigated by differential scanning calorimetry. The melting point (T(m)) and heat of fusion (DeltaH) decreased as the 3HH unit content increased in the range of low 3HH content (<40 mol %), while they increased as the 3HH unit content increased in the high 3HH content range (>70 mol %). The minimum T(m) and DeltaH values were found to exist at 3HH unit content of about 60 mol %. The glass transition temperature (T(g)) decreased linearly with the increase of 3HH unit content. The values of T(m), DeltaH, and T(g) of P(3HB-co-3HH)s were compared with those of poly(3-hydroxybutyrate-co-3-hydroxyvalerate), poly(3-hydroxybutyrate-co-3-hydroxypropionate), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate), and the effects of comonomer types on the thermal properties were revealed.

3-Hydroxybutyric Acid↗