Microbial degradation of poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in soils.

The microbial degradation of tensile test pieces made of poly(3-hydroxybutyrate) [P(3HB)] or a copolymer of 90% 3-hydroxybutyric acid and 10% 3-hydroxyvaleric acid was studied in soils incubated at a constant temperature of 15, 28, or 40 degrees C for up to 200 days. In addition, hydrolytic degradation in sterile buffer at temperatures ranging from 4 to 55 degrees C was monitored for 98 days. Degradation was measured through loss of weight (surface erosion), molecular weight, and mechanical strength. While no weight loss was recorded in sterile buffer, samples incubated in soils were degraded at an erosion rate of 0.03 to 0.64% weight loss per day, depending on the polymer, the soil, and the incubation temperature. The erosion rate was enhanced by incubation at higher temperatures, and in most cases the copolymer lost weight at a higher rate than the homopolymer. The molecular weights of samples incubated at 40 degrees C in soils and those incubated at 40 degrees C in sterile buffer decreased at similar rates, while the molecular weights of samples incubated at lower temperatures remained almost unaffected, indicating that molecular weight decrease is due to simple hydrolysis and not to the action of biodegrading microorganisms. The degradation resulted in loss of mechanical properties. From the samples used in the biodegradation studies, 295 dominant microbial strains capable of degrading P (3HB) and the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer in vitro were isolated and identified.(ABSTRACT TRUNCATED AT 250 WORDS)     

Palladium(II) complexes containing pyrazole-derived ligands of biological interest. Four,five and six coordinate palladium(II) complexes with 5(3)-methylpyrazole-3(5)-carboxamide and 5(3)-methylpyrazole-3(5)-carbohydrazide

Neutral bis-complexes of palladium(II) with 5(3)- methylpyrazole-3(5)-carboxamide (mpa) and 5(3)- methylpyrazole-3(5)carbohydrazide (mph) of the type PdX₂·2L (where L = mpa, mph; X = Cl, Br, I, SCN, NO₃, ClO₄) have been synthesised and spectroscopically characterised. Available physico-chemical data indicate the mpa complexes of Pd(II) to be trans-square planar species with the primary ligand molecule showing monodentate behavior through the pyrazolyl ring nitrogen only. The Pd(II)—thiocyanate complex of mpa is proposed to have a pseudo-square pyramidal geometry attained through bridging anionic component. The complexes PdX₂·2mph (X = Cl, NO₃) appear to be six-coordinate species at least in the solid state; the corresponding thiocyanato variety has in all probability a five coordinate structure. The species, Pd(ClO₄)₂·2mph is a usual four coordinate one with non-coordinating perchlorate group. The monochelates, PdX₂·mph (X = Br, I), are cis-square planar varieties. The ligand molecule, mph, in all cases is believed to function as (N,N) bidentate ligand in its ‘imidol’ form except in the thiocyanate complex where unusually it exhibits both the monodentate and bidentate functions in the same species.     

Combined coenzyme-substrate analogues of various dehydrogenases. Synthesis of (3S)- and (3R)-5-(3-carboxy-3-hydroxypropyl)nicotinamide adenine dinucleotide and their interaction with (S)- and (R)-lactate-specific dehydrogenases.

Two diastereomeric nicotinamide adenine dinucleotide (NAD+) derivatives were synthesized in which the substrates of (S)-and (R)-lactate-specific dehydrogenases are covalently attached via a methylene spacer at position 5 of the nicotinamide ring. The corresponding nicotinamide derivatives were obtained stereospecifically by enzymatic reduction of 5-(2-oxalylethyl)nicotinamide. (3S)-5-(3-Carboxy-3-hydroxypropyl)-NAD+ undergoes and intramolecular hydride transfer in the presence of pig heart lactate dehydrogenase, forming the corresponding coenzyme-substrate analogue composed of pyruvate and NADH. No cross-reaction products resulting from an intermolecular reaction are observed. Two (R)-lactate specific dehydrogenases, however, do not catalyze a similar reaction in either one of the two diastereomers. A possible arrangement of the substrates in the active centers of these enzymes is proposed. 5-Methyl-NAD+ and 5-methyl-NADH are active coenzymes of pig heart lactate dehydrogenase in contrast to reports in the literature. (S)-Lactate binds to this enzyme in the absence of coenzyme, exhibiting a dissociation constant of 11 mM.     

NaHCO(3) and KHCO(3) ingestion rapidly increases renal electrolyte excretion in humans.

This paper describes and quantifies acute responses of the kidneys in correcting plasma volume, acid-base, and ion disturbances resulting from NaHCO(3) and KHCO(3) ingestion. Renal excretion of ions and water was studied in five men after ingestion of 3.57 mmol/kg body mass of sodium bicarbonate (NaHCO(3)) and, in a separate trial, potassium bicarbonate (KHCO(3)). Subjects had a Foley catheter inserted into the bladder and indwelling catheters placed into an antecubital vein and a brachial artery. Blood and urine were sampled in the 30-min period before, the 60-min period during, and the 210-min period after ingestion of the solutions. NaHCO(3) ingestion resulted in a rapid, transient diuresis and natriuresis. Cumulative urine output was 44 +/- 11% of ingested volume, resulting in a 555 +/- 119 ml increase in total body water at the end of the experiment. The cumulative increase (above basal levels) in renal Na(+) excretion accounted for 24 +/- 2% of ingested Na(+). In the KHCO(3) trial, arterial plasma K(+) concentration rapidly increased from 4.25 +/- 0.10 to a peak of 7.17 +/- 0.13 meq/l 140 min after the beginning of ingestion. This increase resulted in a pronounced, transient diuresis, with cumulative urine output at 270 min similar to the volume ingested, natriuresis, and a pronounced kaliuresis that was maintained until the end of the experiment. Cumulative (above basal) renal K(+) excretion at 270 min accounted for 26 +/- 5% of ingested K(+). The kidneys were important in mediating rapid corrections of substantial portions of the fluid and electrolyte disturbances resulting from ingestion of KHCO(3) and NaHCO(3) solutions.     

Relaxin-like bioactivity of ovine Insulin 3 (INSL3) analogues.

Relaxin is an insulin-like peptide consisting of two separate chains (A and B) joined by two inter- and one intrachain disulfide bonds. Binding to its receptor requires an Arg-X-X-X-Arg-X-X-Ile motif in the B-chain. A related member of the insulin superfamily, INSL3, has a tertiary structure that is predicted to be similar to relaxin. It also possesses an Arg-X-X-X-Arg motif within its B-chain, although this is displaced by four amino acids towards the C-terminus from the corresponding position within relaxin. We have previously shown that synthetic INSL3 itself does not display relaxin-like activity although analogue (Analogue A) with an introduced arginine residue in the B-chain giving it an Arg cassette in the exact relaxin position does possess weak activity. In order to identify further the structural features that impart relaxin function, solid phase peptide synthesis was used to prepare three additional analogues for bioassay. Each of these contained point substitutions within the arginine cassette. Analogue D contained the full human relaxin binding cassette, Analogue G consisted of the native INSL3 sequence containing an Arg to Ala substitution, and Analogue E was a further modification of Analogue A, with the same substitution. Each analogue was fully chemically characterized by a number of criteria. Detailed circular dichroism spectroscopy analyses showed that the changes caused little alteration of secondary structure and, hence, overall conformation. However, each analogue displayed only weak relaxin-like activity. These results indicate that while the arginine cassette is vital for relaxin-like activity, there are additional, as yet unidentified structural requirements for relaxin binding.     

L-myo-inositol 1,4,5,6-tetrakisphosphate (3-hydroxy)kinase.

Homogenates of primary-cultured murine bone macrophages contain an enzyme capable of synthesizing myo-[3H]inositol pentakisphosphate from myo-[3H]inositol tetrakisphosphate fractions derived from myo-[3H]inositol-labelled mouse macrophages and chick erythrocytes. D-myo-inositol 1,3,4,5-tetrakis[32P]-phosphate present in the same incubations was not phosphorylated. Since the myo-[3H]inositol-labelled tetrakisphosphate fractions used as substrates consist of a mixture of L-myo-inositol 1,4,5,6-tetrakisphosphate (60-85%) and a periodate-resistant tetrakisphosphate(s) whose characteristics are consistent with those of D-myo-inositol 1,3,4,5-tetrakisphosphate (the preceding paper [Stephens, Hawkins, Carter, Chahwala, Morris, Whetton & Downes (1988) Biochem. J. 249, 271-282] ), these data suggest the existence of a kinase that phosphorylates L-myo-inositol 1,4,5,6-tetrakisphosphate to give a myo-inositol pentakisphosphate. A similar activity was identified in homogenates of rat cerebrum, liver, heart and parotid gland. D-myo-Inositol 1,3,4,5-tetrakis[32P]phosphate in the same incubations was not a substrate. The activity was almost entirely soluble in all the tissues investigated and was found at its greatest specific activity in brain cytosol. The activity was purified 120-fold from a rat brain homogenate by (NH4)2SO4 fractionation and anion-exchange chromatography. The activity was clearly distinct from D-myo-inositol 1,4,5-trisphosphate (3-hydroxy)kinase. Incubation of this partially purified preparation with L-myo-[3H]inositol 1,4,5,6-tetrakisphosphate from chick erythrocytes and [gamma-32P]ATP resulted in the formation of L-myo-[3H]-inositol [1-32P]1,3,4,5,6-pentakisphosphate. The enzyme is therefore identified as an L-myo-inositol 1,4,5,6-tetrakisphosphate (3-hydroxy)kinase.     

Incorporation of 3H from delta-(L-alpha-amino (4,5-3H)adipyl)-L-cysteinyl-D-(4,4-3H)valine into isopenicillin N.

1. delta-(L-alpha-Amino[4,5-3H]adipyl)-L-cysteinyl-D-[4,4-3H]valine has been synthesized from its constituent amino acids, the L-alpha-amino[4,5-3H]adipic acid being obtained by reduction with 3H2 of methyl 5-acetamido-5,5-diethoxycarbonylpent-2-enoate and subsequent decarboxylation and hydrolysis. 2. In a cell-free system prepared by lysis of protoplasts of Cephalosporium acremonium 3H was incorporated from the doubly labelled tripeptide into a compound that behaved like penicillin N or isopenicillin N. The relative specific radioactivities of the alpha-aminoadipyl and penicillamine moieties of the penicillin were the same (within experimental error) as those of the alpha-aminoadipic acid and valine residues respectively of the tripeptide. 3. The behaviour of the labelled alpha-aminoadipic acid from the penicillin to the L-amino acid oxidase of Crotalus adamanteus venom showed that it was mainly L-alpha-aminoadipic acid. 4. The results are consistent with the hypothesis that the carbon skeleton of the LLD-tripeptide is incorporated intact into the penicillin molecule and that the first product is isopenicillin N.     

Spectroscopic investigations of Er(3+) :CdO-Bi(2) O(3) -B(2) O(3) glasses

This article reports on the optical properties of Er³⁺ ions doped CdO–Bi₂O₃–B₂O₃ (CdBiB) glasses. The materials were characterized by optical absorption and emission spectra. By using Judd–Ofelt theory, the intensity parameters Ω_λ (λ = 2, 4, 6) and also oscillatory strengths were calculated from the absorption spectra. The results were used to compute the radiative properties of Er³⁺:CdBiB glasses. The concentration quenching and energy transfer from Yb³⁺–Er³⁺ were explained. The stimulated emission cross‐section, full width at half maximum (FWHM) and FWHM × values are also calculated for all the Er³⁺:CdBiB glasses. Copyright © 2011 John Wiley & Sons, Ltd.     

Degradation of poly (3-hydroxybutyrate) and its copolymer poly (3-hydroxybutyrate-co-3-hydroxyvalerate) by a marine Streptomyces sp. SNG9.

A marine Streptomyces sp. SNG9 was characterized by its ability to utilize poly(3-hydroxybutyrate) (PHB) and its copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate P (3HB-co-HV). The bacterium grew efficiently in a simple mineral liquid medium enriched with 0.1% poly(3-hydroxybutyrate) powder as the sole carbon source. Cells excreted PHB depolymerase and degraded the polymer particles to complete clarity in 4 days. The degradation activity was detectable by the formation of a clear zone around the colony (petri plates) or a clear depth under the colony (test tubes). The expression of PHB depolymerase was repressed by the presence of simple soluble carbon sources. Bacterial degradation of the naturally occurring sheets of poly(3-hydroxybutyrate) and its copolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) was observed by scanning electron microscopy (SEM). Morphological alterations of the polymers sheets were evidence for bacterial hydrolysis.     

Preparation and characterization of eukaryotic initiation factor EIF-3. Formation of binary (EIF-3-Met-tRNAf) and ternary (EIF-3-Met-tRNAf-GTP) complexes.

The 133,000 X g supernatant fraction prepared from ascites cells in 20 mM KCl (low CKl supernatant) contained the initiation factors EIF-1 and EIF-2 (and the elongation factore EF-1 and EF-2) but lacked EIF-3; thus, low KCl supernatant could be used to assay for EIF-3. EIF-3 was prepared from a crude initiation factor perparation (a 250 mM KCl extract of ascites cell ribosomes precipitated with 70% saturated ammonium sulfate) by chromatography on DEAE-Sephadex A-50 and hydroxylapatite. The EIF-O had no detectable EIF-1 and little or no EIF-2. Factor EIF-3 was required fro translation of encephalomyocarditis virus RNA. The molecular weight of EIF-3 was estimated by Sephadex G-200 filtration to be 139,000; the sedimentation coefficient was calculated to be about 5.8. EIF-3 formed a binary complex specifically with the initiator tRNA, Met-tRNAf, and if GTP was present the factor formed a ternary complex (EIF-3-Met-tRNAf-GTP). The EIF-3 preparation had no methionyl-tRNA synthetase activity to account for binding. Complex-formation was with eukaryotic Met-tRNAf and no other aminoacyl-tRNA. The binary and ternary complexes were retained quantitatively on Millipore filters (which was the most convenient assay), but they could also be demonstrated by filtration through Sephadex G-100 or by glycerol gradient centrifugation. GTP increased the rate, the amount, and the stability of complex formed; the ration of GTP to Met-tRNAf in the ternary complex appeared to be 1. The binary and the ternary complexes transferred Met-tRNAf to the 40 S ribosomal subunits, but not to 60 S subparticles. The factor-dependent binding of Met-tRNAf to the 40 S subunit did not require mRNA (or GTP). In the presence of 60 S subunits, the initiator tRNA bound to 40 S subunits was not transferred to 80 S ribosomes even if mRNA was added--that reaction may require another initiation factor. Treatment of EIF-3 with N-ethylmaleimide led to loss of its activity in complex formation and in support of the translation of encephalomyocarditis virus RNA. In addition to forming the binary and ternary complexes, and supporting the translation of encephalomyocarditis virus RNA, EIF-3 also increases the number of free ribosomal subunits by either preventing their association or causing dissociation of 80 S couples.