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PubMed1998

Synthesis and Characterization of Dimeric, Trimeric, and Tetrameric Gallophosphonates and Gallophosphates.

THF/toluene solutions of phosphonic or phosphoric acids were reacted with (t)Bu(3)Ga at low temperature to yield the cyclic dimers [(t)Bu(2)GaO(2)P(OH)R](2) (R = Ph, Me, (t)Bu, H, OH; 1-5). Poor crystallinity and variable thermal stabilities of 1-5 necessitated derivatization with Me(3)SiNMe(2) to yield [(t)Bu(2)GaO(2)P(OSiMe(3))R](2) (R = Ph, Me, (t)Bu, H, OSiMe(3); 6-10), which were more amenable to purification and characterization. In solution, trans isomers were predominant for 6 and 7 at ambient temperature, whereas the cis isomer of 8 was predominant. NMR spectroscopy demonstrated cis-trans interconversion for 6-8 and crossover experiments showed interconversion to occur by, or be accompanied with, an intermolecular exchange process. Thermolysis of 3 in refluxing toluene yielded the cluster [((t)BuGa)(2)((t)Bu(2)Ga)(O(3)P(t)Bu)(2){O(2)P(OH)(t)Bu}] (11), which was converted to [((t)BuGa)(2)((t)Bu(2)Ga)(O(3)P(t)Bu)(2){O(2)P(OSiMe(3))(t)Bu}] (12) with Me(3)SiNMe(2). Thermolysis of 1-3 in refluxing diglyme, or solid-state pyrolysis at 250 degrees C in vacuo, yielded [(t)BuGaO(3)PR](4) (R = Ph, (t)Bu, Me; 13-15). The gallophosphate [(t)BuGaO(3)P(OSiMe(3))](4) (16) was similarly obtained by reaction of (t)Bu(3)Ga with H(3)PO(4) in refluxing diglyme, followed by trimethylsilylation with Me(3)SiNMe(2). Compounds 13-16 possess cuboidal Ga(4)P(4)O(12) cores analogous to double-four-ring secondary building units in the gallophosphates cloverite, gallophosphate-A, and ULM-5. The thermal, hydrolytic, and oxidative stabilities of 13-16 are discussed, as are observed intermolecular exchange processes. In addition to characterization of 1-16 by multinuclear ((1)H, (13)C, (31)P) NMR spectroscopy, infrared spectroscopy, mass spectrometry, and elemental analysis, molecular structures for compounds 6, 8, 10, 12, 14, 15, and 16 were determined by X-ray crystallography.

Journal Article↗

PubMed2005

Fatty acid composition and antioxidant properties of cold-pressed marionberry, boysenberry, red raspberry, and blueberry seed oils.

Cold-pressed marionberry, boysenberry, red raspberry, and blueberry seed oils were evaluated for their fatty acid composition, carotenoid content, tocopherol profile, total phenolic content (TPC), oxidative stability index (OSI), peroxide value, and antioxidant properties. All tested seed oils contained significant levels of alpha-linolenic acid ranging from 19.6 to 32.4 g per 100 g of oil, along with a low ratio of n-6/n-3 fatty acids (1.64-3.99). The total carotenoid content ranged from 12.5 to 30.0 micromoles per kg oil. Zeaxanthin was the major carotenoid compound in all tested berry seed oils, along with beta-carotene, lutein, and cryptoxanthin. Total tocopherol was 260.6-2276.9 mumoles per kg oil, including alpha-, gamma-, and delta-tocopherols. OSI values were 20.07, 20.30, and 44.76 h for the marionberry, red raspberry, and boysenberry seed oils, respectively. The highest TPC of 2.0 mg gallic acid equivalents per gram of oil was observed in the red raspberry seed oil, while the strongest oxygen radical absorbance capacity was in boysenberry seed oil extract (77.9 micromol trolox equivalents per g oil). All tested berry seed oils directly reacted with and quenched DPPH radicals in a dose- and time-dependent manner. These data suggest that the cold-pressed berry seed oils may serve as potential dietary sources of tocopherols, carotenoids, and natural antioxidants.

Antioxidants↗

PubMed2003

Beneficial effect of oleoylated lipids on paraoxonase 1: protection against oxidative inactivation and stabilization.

The effect of lipids on PON1 (paraoxonase 1), one of antioxidant proteins in high-density lipoprotein, was investigated in respect to inhibition, protection against oxidative inactivation, and stabilization. When the effect of lipids on the PON1 activity was examined, a remarkable inhibition was expressed by polyenoic fatty acids (C18:2-C20:5). Linoleic acid, the most potent ( K(i), 3.8 microM), showed competitive inhibition. Next, various lipids were examined for prevention against the inactivation of PON1 by ascorbate/Cu2+, which caused a remarkable (>or =90%) inactivation of PON1. Compared with saturated fatty acids (C6-C18), exhibiting a modest protection (9-40%), monoenoic acids (C16:1-C20:1) showed a greater maximal protective effect (Emax, 70-82%), with oleic acid being the most effective (EC50, 2.7 microM). In contrast, polyenoic acids showed no protection. Noteworthy, linoleic acid prohibited the protective action of oleic acid non-competitively. In the structure-activity relationship, a negatively charged group seems to be required for the protective action. Consistent with this, dioleoylphosphatidylglycerol, negatively charged, was more protective than dioleoylphosphatidylcholine. These data, together with requirement of Ca2+ (EC50, 0.6 microM) for the protective action, may support the existence of a specific site responsible for the protective action. A similar protective action of lipids was also observed in the inactivation of PON1 by ascorbate/Fe2+, peroxides or p -hydroxymercuribenzoate. Separately, PON1 was stabilized by oleic acid or oleoylated phospholipids, in combination with Ca2+, but not linoleic acid. These results suggest that in contrast to an adverse action of linoleic acid, monoenoic acids or their phospholipid derivatives play a beneficial role in protecting PON1 from oxidative inactivation as well as in stabilizing PON1.

Aryldialkylphosphatase↗

PubMed2004

Hypothesis: selective phosphodiesterase-5 inhibition improves outcome in preeclampsia.

The pathogenesis of preeclampsia stems from aberrant changes at the placental interface. The trophoblastic endovascular invasion of tonic spiral arteries that converts them to passive conduits falters. Uteroplacental insufficiency and fetoplacental hypoxemia result. Secondary maternal oxidative stress and an excessive inflammatory response to pregnancy generate the clinical syndrome of preeclampsia. Current treatment focuses on preventing seizures, controlling hypertension, preserving renal function and delivering the baby. We propose that the pathophysiological changes induced by preeclampsia in the placenta parallel those caused by persistent hypoxemia in the lungs at high altitude or with chronic obstructive pulmonary disease. Unrelenting pulmonary hypoxic vasoconstriction induces pulmonary hypertension and cor pulmonale. Inhalation of nitric oxide and phosphodiesterase-5 inhibitors opposes pulmonary hypoxic vasoconstriction, alleviates pulmonary hypertension and improves systemic oxygenation. Notably nitric oxide donor therapy also counters hypoxemic fetoplacental vasoconstriction, a biological response analogous to pulmonary hypoxic vasoconstriction. Fetal oxygenation and nutrition improve. Placental upstream resistance to umbilical arterial blood flow decreases. Fetal right ventricular impedance falls. Heart failure (cor placentale) is avoided. Emergency preterm delivery can be postponed. Other than low dose aspirin and antioxidants vitamins C and E no available therapy specifically targets the underlying disease profile. We hypothesize that, like nitric oxide donation, pharmacological inhibition of placental phosphodiesterase-5 will also protect the fetus but for a longer time. Biological availability of guanosine 3'5'-cyclic monophosphate is boosted due to slowed hydrolysis. Adenosine 3'5'-cyclic monphosphate levels increase in parallel. Cyclic nucleotide accumulation dilates intact tonic spiral arteries and counters hypoxemic fetoplacental vasoconstriction. Intervillous and intravillous perfusion pick up. Maternal to fetal placental circulatory matching improves. Enhanced placental oxygen uptake alleviates hypoxemic fetal stress. Appropriate fetal nutrition resumes. Cor placentale and severe intrauterine growth restriction are averted. Increased maternal cyclic nucleotide concentrations promote systemic vasodilatation so that blood pressures fall. Preemption of oxidative stress initiated by "consumptive" oxidation of nitric oxide stabilizes the vascular endothelium and corrects coagulopathy. Anti-inflammatory and immunosuppressant adenosine 3'5'-cyclic monphosphate offsets the extreme gestational inflammatory response. Cellular injury and multi-organ damage are prevented. One tablet a day of the new long acting phosphodiesterase-5 inhibitor, tadalafil (half life of 17.5 h) theoretically should allow a preterm pregnancy affected by preeclampsia to continue safely. Selective monitoring of vital organ functions guards against life-threatening maternal complications. Regular biophysical profiling warns the obstetrician of impending fetal compromise. Fetal growth and vital organ maturation can continue. As a result workloads imposed upon neonatal intensivists will lighten. Parental anxiety and concern will be allayed. The cost of treating preeclamptic mothers and their extremely low birth weight infants will decrease. Money saved by midwifery services in poorer states can be used to pay for better prenatal care. Severe preeclampsia/eclampsia will be less common. Maternal and perinatal morbidity and mortality will be reduced. Because the human immunodeficiency virus often infects individuals at a workforce eligible age, the global acquired immunodeficiency syndrome pandemic has already brought many nations to the brink of economic ruin. Potentially productive lives saved for the future will help restore them fiscally.

3',5'-Cyclic-GMP Phosphodiesterases↗

PubMed1997

In vivo biocompatibility and biostability of modified polyurethanes.

Modified segmented polyurethanes were examined for biostability and biocompatibility using an in vivo cage implant system for time intervals of 1, 2, 3, 5, and 10 weeks. Two types of materials were used: polyether polyurethanes and polycarbonate polyurethanes. Two unmodified polyether polyurethanes (PEUU A' and SPU-PRM), one PDMS endcapped polyether polyurethane (SPU-S), and two polycarbonate polyurethanes (SPU-PCU and SPU-C) were investigated in this study. Techniques used to characterize untreated materials were dynamic water contact angle, stress-strain analysis, and gel permeation chromatography. Cellular response was measured by exudate analysis and by macrophage and foreign body giant cell (FBGC) densities. Material characterization, postimplantation, was done by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) in order to quantify biodegradation and scanning electron microscopy (SEM) to qualitatively describe the cellular response and biodegradation. The exudate analysis showed that the acute and chronic inflammatory responses for all materials were similar. Lower FBGC densities and cell coverage on SPU-S were attributed to the hydrophobic surface provided by the PDMS endgroups. The polycarbonate polyurethanes did not show any significant differences in cell coverage or FBGC densities even though the macrophage densities were slightly lower compared to polyether polyurethanes. By 10 weeks, biodegradation in the case of PEUU A' and SPU-PRM was extensive as compared to SPU-S because the PDMS endcaps of SPU-S provided a shield against the oxygen radicals secreted by macrophages and FBGCs and lowered the rate of biodegradation. In the case of polycarbonate polyurethanes, the oxidative stability of the carbonate linkage lowered the rate of biodegradation tremendously as compared to the polyether polyurethanes (including SPU-S). The minor amount of biodegradation seen in polycarbonate polyurethanes at 10 weeks was attributed to hydrolysis of the carbonate linkage.

Animals↗

PubMed1998

Heat and storage effects on the flavour of peanuts.

Two peanut varieties, Giza 4 and Giza 5 were subjected to different heat treatments such as drying in solar drier at air speed 0.5 and 2 m/sec with average temperature 45 and 60 degrees C and heating in oven at 120 and 150 degrees C. The sensory evaluation of the two varieties showed insignificant differences among varieties and heating processes. A correlation between the sensory and instrumental data was found. The high sensory scores of samples heated at 150 degrees C were attributed to the presence of high concentration of pyrazines which were thought to contribute to flavour and aroma of fresh roasted peanut. A comparative study between the main chemical classes retained in peanut samples after storage for 3 months at room temperature showed that the aldehydes derived lipids increased significantly in the solar dried samples. The antioxidative components produced via Maillard reaction resulted in oxidative stability of the samples heated in oven.

Aldehydes↗

PubMed2003

Properties of a novel magnetized alginate for magnetic resonance imaging.

Implanting recombinant cells encapsulated in alginate microcapsules to secrete therapeutic proteins has been proven clinically effective in treating several murine models of human diseases. However, once implanted, these microcapsules cannot be assessed without invasive surgery. We now report the preparation and characterization of a novel ferrofluid to render these microcapsules visible with magnetic resonance imaging (MRI). The ferrofluid was prepared as a colloidal iron oxide stabilized in water by alginate. The presence of iron particles in the ferrofluid was verified with chemical titration, dynamic light scattering, and magnetization measurement. The microcapsules fabricated with various concentrations of the ferrofluid in the core, or on the surface of alginate microcapsules, or both, all produced microcapsules with smooth surfaces as shown with light and scanning electron microscopy. However, at the nanoscale level, as revealed with atomic force microscopy, the ferrofluid-fabricated microcapsules demonstrated increased granularity, particularly when the ferrofluid was used to laminate the surface. From the force spectroscopy measurements, these modified microcapsules showed increasing surface rigidity in the following order: traditional alginate < ferrofluid in the core < ferrofluid on the surface. Although the mechanical stability of low-concentration ferrofluid (0.1%) microcapsules was reduced, increasing concentrations, up to 20%, were able to improve stability. When these ferrofluid microcapsules were examined with MRI, their T(2) relaxation time was reduced, thereby producing increased contrast readily detectable with MRI, whereas the traditional alginate microcapsules showed no difference when compared with water. In conclusion, such ferrofluid-enhanced alginate is suitable for fabricating microcapsules that offer the potential for in vivo tracking of implanted microcapsules without invasive surgery.

Alginates↗

PubMed2004

Self-assembled monolayers of dendritic polyglycerol derivatives on gold that resist the adsorption of proteins.

Highly protein-resistant, self-assembled monolayers (SAMs) of dendritic polyglycerols (PGs) on gold can easily be obtained by simple chemical modification of these readily available polymers with a surface-active disulfide linker group. Several disulfide-functionalized PGs were synthesized by N,N'-dicyclohexylcarbodiimide-mediated ester coupling of thioctic acid. Monolayers of the disulfide-functionalized PG derivatives spontaneously form on a semitransparent gold surface and effectively prevent the adsorption of proteins, as demonstrated by surface plasmon resonance (SPR) kinetic measurements. A structure-activity relationship relating the polymer architecture to its ability to effectuate protein resistance has been derived from results of different surface characterization techniques (SPR, attenuated total reflectance infrared (ATR-IR), and contact-angle measurements). Dendritic PGs combine the characteristic structural features of several highly protein-resistant surfaces: a highly flexible aliphatic polyether, hydrophilic surface groups, and a highly branched architecture. PG monolayers are as protein resistant as poly(ethylene glycol) (PEG) SAMs and are significantly better than dextran-coated surfaces, which are currently used as the background for SPR spectroscopy. Due to the higher thermal and oxidative stability of the bulk PG as compared to the PEG and the easy accessibility of these materials, dendritic polyglycerols are novel and promising candidates as surface coatings for biomedical applications.

Adsorption↗

PubMed1990

[Progress report. Lipid peroxidation. 2. Secondary reactions].

Lipids and lipid containing foods are altered by autoxidative processes resulting in the formation of hydroperoxides which are considered as the actual primary autoxidation products. These hydroperoxides cause a variety of secondary reactions giving di- and trihydroperoxides, hydroperoxyepidioxides, endoperoxides and hydroperoxyepoxides, so called secondary autoxidation products at a primary level. Sometimes they are only minor substances. The formation of primary autoxidation products is accelerated by reaction conditions as increased temperature, oxygen, metal ions and sensibilizers but is inhibited by natural and synthetic antioxidants. The decomposition of hydroperoxides and secondary autoxidation products at the primary level results in volatile substances decreasing the flavour quality of lipid containing foods. Simultaneously there are other cleavage and decomposition products remaining in the lipid causing a reduction of its oxidative stability.

Chemical Phenomena↗

PubMed2004

Poly(carbonate urethane) and poly(ether urethane) biodegradation: in vivo studies.

Several strategies have been used to increase the biostability of medical-grade polyurethanes while maintaining biocompatibility and mechanical properties. One approach is to chemically modify or replace the susceptible soft segment. Currently, poly(carbonate urethanes) (PCUs) are being evaluated as a replacement of poly(ether urethanes) (PEUs) in medical devices because of the increased oxidative stability of the polycarbonate soft segment. Preliminary in vivo and in vitro studies have reported improved biostability of PCUs over PEUs. Although several studies have reported evidence of in vitro degradation of these new polyurethanes, there has been no evidence of significant in vivo degradation that validates a degradation mechanism. In this study, the effect of soft segment chemistry on the phase morphology, mechanical properties, and in vivo response of commercial-grade PEU and PCU elastomers was examined. Results from dynamic mechanical testing and infrared spectroscopy suggested that the phase separation was better in PCU as compared with PEU. In addition, the higher modulus and reduced ultimate elongation of PCU was attributed to the reduced flexibility of the polycarbonate soft segment. Following material characterization, the in vivo biostability and biocompatibility of PEU and PCU were studied using a subcutaneous cage implant protocol. The results from the cage implant study and cell culture experiments indicated that monocytes adhere, differentiate, and fuse to form foreign body giant cells on both polyurethanes. It is now generally accepted that the reactive oxygen species released by these adherent macrophages and foreign body giant cells initiate PEU biodegradation. Attenuated total reflectance-Fourier transform infrared analysis of explanted samples provided evidence of chain scission and crosslinking in both polyurethanes. This indicated that the PCU was also susceptible to biodegradation by agents released from adherent cells. These results reinforce the need to evaluate and understand the biodegradation mechanisms of PCUs.

Biocompatible Materials↗

PubMed2006

A novel polymer for potential use in a trileaflet heart valve.

A novel polyolefin, poly(styrene-b-isobutylene-b-styrene) (Quatromer), is being proposed as a viable polymer for use in trileaflet heart valves because of its oxidative stability. The current study was designed to assess the polymer's hemocompatibility and mechanical durability. Mechanical characterization included static tensile tests and dynamic tension-tension and bending fatigue tests, where the properties of isotropic and composite (polypropylene (PP) embedded) Quatromer specimens were compared with those of a polyurethane (PUR) approved for cardiovascular applications. It was found that by embedding PP fibers into the Quatromer matrix, the tensile and fatigue properties of the polymer could be improved, making them comparable, if not better than the PUR. The thrombotic potential of Quatromer was compared with the PUR, glutaraldehyde-fixed porcine valve material, and a positive and negative control by measuring platelet deposition with radiolabeled platelets in a parallel plate flow configuration. The porcine valve material was found to have significantly higher platelet deposition under all flow regimes, while no significant difference existed between Quatromer and PUR. In conclusion, Quatromer is shown to have suitable hemocompatibility and mechanical durability for use in polymer trileaflet heart valves, and fiber reinforcement can effectively be used to tailor the mechanical properties.

Animals↗

PubMed2001

Dietary effects of bitter gourd oil on blood and liver lipids of rats.

Bitter gourd is widely used as an edible plant in Asia. In this study, we evaluated the effects of bitter gourd oil (BGO) on the blood and liver lipids of rats. Three groups of rats were given a basal diet (AIN-93G) containing 7% fat by weight. The dietary fat consisted of soybean oil (control), soybean oil + BGO (6.5:0.5, w/w; 0.5% BGO), or soybean oil + BGO (5:2, w/w; 2.0% BGO). This fat treatment gave 3.4 and 15.4% of cis(c)9,trans(t)11,t13-18:3 in the dietary fat of 0.5 and 2.0% BGO, respectively. Fatty acid analysis showed the occurrence of c9,t11-18:2 in the liver of rats fed BGO diets, whereas this conjugated linoleic acid (CLA) isomer was not detected in the liver of rats fed the control diet. Furthermore, dietary BGO decreased the concentration of 18:2n-6 and increased the concentration of 22:6n-3. The formation of the CLA isomer in the liver lipids of rats fed BGO diets could be explained by either of the following two metabolic pathways, namely, enzymatic biohydrogenation of c9,t11,t13-18:3 or enzymatic isomerization of c9,c12-18:2. The BGO diets had significantly reduced free cholesterol levels with a trend toward an increase in HDL cholesterol, but there was no significant change in the total cholesterol. The dietary BGO also affected the level of plasma hydroperoxides. A slight but significant increase in hydroperoxides was found in the rats fed 2.0% BGO. This may be attributed to the lower oxidative stability of c9,t11,t13-18:3 in BGO.

Animal Nutritional Physiological Phenomena↗

PubMed1999

Impact of processing on formation of trans fatty acids.

Trans fatty acids are formed during hydrogenation which is done to improve the functionality and oxidative stability of oils. Several process conditions affect the content of trans fatty acids in hydrogenated oil. There is conflicting evidence as to whether intake of trans fatty acids, in foods such as margarine, affects the types and levels of cholesterol produced in the blood. Epidemiological studies have shown associated increases in total cholesterol and low density lipoproteins, as well as decreased levels of high density lipo-proteins in the blood. It is unknown whether these effects are related directly to trans fatty acids or to the decrease of unsaturated fatty acids in the diet. This chapter will cover the recent nutritional status of trans fatty acids and the effect of processing on the levels of trans fatty acids in foods.

Adult↗

PubMed2006

Mapping of the loci controlling oleic and linolenic acid contents and development of fad2 and fad3 allele-specific markers in canola (Brassica napus L.).

The quality of canola oil is determined by its constituent fatty acids such as oleic acid (C18:1), linoleic acid (C18:2) and linolenic acid (C18:3). Most canola cultivars normally produce oil with about 55-65% oleic acid and 8-12% linolenic acid. High concentrations of linolenic acid lead to oil instability and off-type flavor, while high levels of oleic acid increase oxidative stability and nutritional value of oil. Therefore, development of canola cultivars with increased oleic acid and reduced linolenic acid is highly desirable for canola oil quality. In this study, we have mapped one locus that has a major effect and one locus that has a minor effect for high oleic acid and two loci that have major effects for low linolenic acid in a doubled haploid population. The major locus for high C18:1 was proven to be the fatty acid desaturase-2 (fad2) gene and it is located on the linkage group N5; the minor locus is located on N1. One major QTL for C18:3 is the fatty acid desaturase-3 gene of the genome C (fad3c) and it is located on N14. The second major QTL resides on N4 and is the fad3a gene of the A genome. We have sequenced genomic clones of the fad2 and fad3c genes amplified from an EMS-induced mutant and a wild-type canola cultivar. A comparison of the mutant and wild-type allele sequences of the fad2 and fad3c genes revealed single nucleotide mutations in each of the genes. Detailed sequence analyses suggested mechanisms by which both the mutations can cause altered fatty acid content. Based on the sequence differences between the mutant and wild-type alleles, two single nucleotide polymorphism (SNP) markers, corresponding to the fad2 and fad3c gene mutations, were developed. These markers will be highly useful for direct selection of desirable fad2 and fad3c alleles during marker-assisted trait introgression and breeding of canola with high oleic and low linolenic acid.

Alleles↗

PubMed1981

Cytoplasmic streaming in a heliozoan.

A method is described utilizing deuterium oxide stabilization of microtubules that allows the separation of stable axopodia from the cell body. In some instances the isolated axopodia are broken open and display two classes of cytoplasmic linear elements, microtubules and microfilaments, lying side by side. This morphological arrangement is consistent with the hypothesis that microtubules support a microfilament-based contractile apparatus in heliozoans and probably other cell types as well. Also included is a description of pseudopodial formation from axopodial cytoplasm in response to mechanical stimulation. The pseudopodial motility is discussed in relation to the particle saltations also observed in these cells and to different levels of organization or activation of the contractile machinery.

Animals↗

PubMedDate not supplied

A study of factors affecting the labelling of tartrate with 188Re and the transchelation of the 188Re from the tartrate to a protein.

The formation of 188Re-tartrate for use in transchelation reactions and the transchelation of the 188Re onto albumin was studied. Two labelled tartrate products were separated using a non-traditional mobile phase on ITLC strips. Tartrate labelling yield increases with pH but so does the instability when the product is exposed to air. Lower pH's are preferred when oxygen-free labelling conditions can be achieved. Higher tin levels protect against air oxidation. Stability of the Re-tartrate complex is supported by addition of ascorbic acid and ferrous sulphate, however both these agents decreased the rate of the formation of the Re-tartrate complex. The labelling efficiency of a perrhenate solution decreased with the time for which it is stored prior to the labelling reaction, depending on the radioactive concentration.Re-albumin transchelation efficiency increases with the tartrate concentration, while increased stability of the Re-tartrate complex lowers the transchelation yields of Re-albumin.

Chelating Agents↗

PubMed2005

Thermostable D-carbamoylase from Sinorhizobium morelens S-5: purification, characterization and gene expression in Escherichia coli.

A d-carbamoylase from Sinorhizobium morelens S-5 was purified and characterized. The enzyme was purified 189-fold to homogeneity with a yield of 19.1% by aqueous two-phase extraction and two steps of column chromatography. The enzyme is a homotetramer with a native molecular mass of 150 kDa and a subunit relative molecular mass of 38 kDa. The optimum pH and temperature of the enzyme were pH 7.0 and 60 degrees C, respectively. The enzyme showed high thermal and oxidative stability. It was found to have a K(m) of 3.76 mM and a V(max) of 383 U/mg for N-carbamoyl-d-p-hydroxyphenylglycine. The hyuC gene coding for this enzyme was cloned, and its nucleotide sequence was determined. The deduced amino acid sequence encoded by the hyuC gene exhibited high homology to the amino acid sequences of d-carbamoylase from other sources. The gene could be highly expressed in Escherichia coli, and the product was purified to homogeneity from the recombinant. Our results show that the enzyme has great potential for industrial application.

Amidohydrolases↗

PubMed2005

The anti-oxidative properties of alpha-tocopherol in gamma-irradiated UHMWPE with respect to fatigue and oxidation resistance.

Although addition of an antioxidant (alpha-tocopherol) is reported to prevent delamination in ultrahigh molecular weight polyethylene (UHMWPE) knee components, contribution of alpha-tocopherol as an antioxidant to the improvement of long-term fatigue performance of UHMWPE is an unknown mechanism. To solve this problem, bi-directional sliding fatigue tests were performed for gamma-irradiated (25 kGy), gamma-irradiated (25 kGy) with 0.3 wt% alpha-tocopherol added, and gamma-irradiated (25 kGy) with 0.3 wt% tocopheryl acetate added UHMWPE specimens. Internal defect initiation was quantified with scanning acoustic tomography (SAT). Also, oxidation index and crystallinity were obtained from infrared absorption spectra measured using Fourier transform infrared (FT-IR) microscopy. Only gamma-irradiated UHMWPE specimens resulted in severe fatigue fractures. alpha-Tocopherol-added UHMWPE specimens showed significantly lower projected area ratio of defects (1.80+/-0.82) than did gamma-irradiated (7.0+/-2.29) and tocopheryl acetate-added ones (8.50+/-2.01). The oxidation index of gamma-irradiated UHMWPE specimens (0.111+/-0.0052) was extremely higher compared to those of doped ones; 0.0179+/-0.0026 and 0.0144+/-0.0069 for alpha-tocopherol-added and tocopheryl acetate-added ones, respectively. The crystallinity of gamma-irradiated UHMWPE specimens (57.5+/-1.16) was lower compared to those of doped ones; 60.3+/-0.72 and 60.4+/-1.38 for alpha-tocopherol-added and tocopheryl acetate-added ones, respectively. The incorporation of alpha-tocopherol significantly improves the long-term fatigue performance of gamma-irradiated UHMWPE with oxidation stability. Also, the addition of alpha-tocopherol controls macromolecular structures resulting in the improvement of fatigue performance of UHMWPE.

Antioxidants↗