Low Molecular Weight Range Research Articles

Variations of Landfill Leachate's Properties in Conjunction with the Treatment Process

A study was done on the variations of water quality parameters, in conjunction with the processing steps, installed for the treatment of leachate from a sanitary landfill. The leachate was primarily subjected to biological treatment, composed of anaerobic digestion, aerobic treatment, and rotating biological contact in series. The effluent from the rotating biological contact process was further treated by combination of flocculation-sedimentation and adsorption processes. Finally, it was polished by the reverse osmosis process before discharge. The quality of raw leachate, of influents to and of effluents from the reverse osmosis process was assessed and compared. To determine size - dependent behavior of organic materials, analyses were also made for the fractionated samples through ultrafiltration. The overall treatment efficiency was about 98 % for removal of organic materials. Most of the organic materials were in the low molecular weight range. In particular, about 95% of the biological oxygen demand was found to be exerted by the fraction of organic material of which cut - off molecular weight was less than 500. The analysis of molecular weight distribution confirmed that the organic materials resistant to the removal by the treatment process were humic substances, of which cut off molecular weight was greater than 500. The reverse osmosis process showed a high efficiency for removal of high molecular weight constituents. However, the final effluent showed an unexpectedly high oxygen demand.

The plant defence activator acibenzolar-S-methyl primes cowpea [ Vigna unguiculata(L.) Walp.] seedlings for rapid induction of resistance

Cowpea [ Vigna unguiculata(L.) Walp.] seedlings, raised from seeds treated with acibenzolar-S-methyl [benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester; BTH], were inoculated at 7 days old withColletotrichum destructivum . Tissue penetration was reduced markedly and intracellular infection vesicles were invariably restricted to the initially-infected epidermal cells of treated hypocotyls and leaves. The destructive necrotrophic phase of disease development was effectively blocked by a hypersensitive response in these cells, thereby protecting seedlings against damping-off. The enhanced resistance of BTH-treated tissues was associated with rapid, transient increases in the activities of two key enzymes of the phenylpropanoid/flavonoid pathway, phenylalanine ammonia-lyase (PAL) and chalcone isomerase (CHI). Subsequently, there was an early, accelerated accumulation of the isoflavonoid phytoalexins kievitone and phaseollidin in treated hypocotyls. In addition, several protein bands, in the low-molecular weight range, developed in these treated challenged tissues. These responses occurred following inoculation of a normally susceptible cultivar (IT82E-60) with the pathogen, and were not observed in induced, uninoculated tissues. These results suggest that BTH protects cowpea seedlings by potentiating an early defence response rather than by altering the constitutive resistance of tissues.

Immunoglobulin subclass responses of wild brown rats to Sarcocystissingaporensis

Immunoglobulin subclass responses of wild brown rats ( Rattus norvegicus) from southeastern Asia to the endemic cyst-forming coccidian Sarcocystis singaporensis were characterised. The antibody response of brown rats to wild-type parasites (high reproductive capacity) showed a Th1 profile during acute infection, namely elevated concentrations of parasite-specific IgG2b and IgG2c and absence of IgG1. Chronic infection (bradyzoite development) resulted in a mixed Th1/Th2 pattern whereby significant concentrations of IgG1 appeared. A primary infection with 1000 sporocysts eight days before challenge induced protection, accompanied by significant concentrations of IgA and IgG2, particularly IgG2a. Western blot analysis of rat sera, using sporozoite and bradyzoite-extracts as antigen, revealed that IgG1, IgG2a, and IgG2b predominantly recognised molecules between 70–80 kDa in one or the other stage. Some of the antibodies were possibly directed against a 79 kDa heat shock protein of sporozoites. An apparent unresponsiveness to molecules in the low molecular weight range, particularly of bradyzoite antigens, was observed. This was abrogated by infection of rats with an avirulent strain of S. singaporensis (low reproductive capacity) indicating that a parasite that was less adapted to its host provoked a stronger immune response. These results suggest the existence of an immune evasion strategy used by Sarcocystis and show that wild rodents may be suitable as immunological research objects, reflecting the natural situation.

An investigation into the surface deposition of progesterone on poly (d,l-) lactic acid microspheres using micro-thermal analysis.

Polylactic acid microspheres are well established as delivery vehicles for a range of low molecular weight and proteinaceous drugs (1–3). However, there is arguably a paucity of information available regarding the physical characteristics of these spheres, with few studies (4) addressing the issue of the manner in which drugs are distributed through the polymeric matrix. Following earlier studies (5,6) we recently investigated the use of modulated temperature DSC (MTDSC) as a means of monitoring the distribution of progesterone within poly(d,l-lactide) spheres using a range of loadings up to 50% w/w (7). By monitoring the thermal response of the spheres we obtained strong evidence for the drug being present as a separate amorphous phase at 30% w/w loading and as a distinct crystalline phase at 50% w/w loading. Complementary SEM studies showed marked changes in the surface morphology of the spheres at these two concentrations, leading to the suggestion of surface drug deposition. However, it was not possible at that stage to definitively establish the location of the drug using the methodologies available. A recent advance within the thermal analysis field has been the introduction of micro-thermal analysis (micro-TA, 8–10). This method is based on the same principles as conventional AFM but involves the replacement of the probe tip with a Wollaston wire loop. The apex of the wire is etched away to leave the silver filament exposed, resulting in a higher resistance in this section of the tip. Application of a voltage therefore results in Joule heating, hence one may apply a thermal signal to highly specific regions of a sample. In addition, the technique allows isothermal measurement of thermal conductivity by rastering over the surface and measuring the tip resistance. The technique has attracted considerable interest, particularly within the polymer science field, as it represents a unique method of performing thermal analysis on highly specific regions of a sample without the necessity of heating the material in its entirety. Early studies on pharmaceutical materials have also yielded highly encouraging results (11,12). The ability of micro-TA to perform localised thermal analysis suggests that the method may be a means of establishing whether the progesterone is indeed present on the surface of the aforementioned microspheres. The objective of the present study was therefore to investigate the use of micro-TA as a novel means of characterising the surface of the PLA microspheres, with a particular view to obtaining further evidence for the presence or absence of progesterone on the exterior of the spheres.

L to d Amino Acid Isomerization in a Peptide Hormone Is a Late Post-translational Event Occurring in Specialized Neurosecretory Cells

Modification of the chirality of a single amino acid residue within a peptide chain appears to be novel additional mechanism leading to structural and functional diversification of eukaryotic bioactive peptides. This phenomenon has been studied at the cellular level in a neuroendocrine organ which elaborates a mixture of diastereoisomers of a 72-residue neuropeptide, crustacean hyperglycemic hormone. For the first time, amino acid isomerization has been shown to occur in the perikarya of fully specialized neurosecretory cells, as a late step of the maturation of the hyperglycemic hormone precursor and after propeptide cleavage. The specificity and efficiency of this phenomenon indicates the existence of a new enzyme family involved in the biogenesis of peptide hormones.

Emissions of CH3Br, organochlorines, and organoiodines from temperate macroalgae

The production rates of a range of low molecular weight halogenated organics have been determined in cultures of five temperate species of macroalgae collected from the north coast of Norfolk, England. Compounds studied included CH3Br, the chlorinated organics CH3Cl, CH2Cl2 and CHCl3, and the iodinated organics CH3I, C2H5I, and CH2ClI. Measurements of a wider range of halocarbon concentrations in an isolated rockpool and in air over the seaweed bed were also conducted to evaluate the local impact of the seaweeds on halocarbon concentrations in the natural environment. Estimates for the global emissions of some of the key halogenated compounds from macroalgae have been derived. In general macrophytes appear not to be globally significant producers of the particular halocarbons studied. In coastal regions, however, the impact on local atmospheric composition and chemistry could be greater.

Molecular Weight Characterization of Poly(N-isopropylacrylamide) Prepared by Living Free-Radical Polymerization

A series of relatively monodisperse samples of poly(N-isopropylacrylamide) were synthesized by reversible addition−fragmentation chain transfer (RAFT) over the molecular weight range 2 × 103−3 × 105. For molecular weights below 4 × 104, conditions were found so that polydispersity remained below 1.4 up to high conversion (72%). Molecular weight distributions of polymer obtained using GPC in THF and MALDI were in accord for the low molecular weight range (typically 105). Particular care is required in GPC sample preparation: it is necessary to ensure that trace amounts of water are initially present when drying a polymer sample prior to dissolution in THF, to avoid irreversible chain aggregation. The log/log plot of intrinsic viscosity against molecular weight for polyNIPAM was found to be linear for molecular weights <105, after which the hydrodynamic volume seems to be independent of molecular weight. The Mark−Houwink parameters obtained from the lower molecular weight data are K = 10-(4.24±0.42) dL g-1 and a = 0.78 ± 0.09.

Aldosterone induces ras methylation in A6 epithelia.

Aldosterone increases Na(+) reabsorption by renal epithelial cells: the acute actions (<4 h) appear to be promoted by protein methylation. This paper describes the relationship between protein methylation and aldosterone's action and describes aldosterone-mediated targets for methylation in cultured renal cells (A6). Aldosterone increases protein methylation from 7.90 +/- 0.60 to 20.1 +/- 0.80 methyl ester cpm/microg protein. Aldosterone stimulates protein methylation by increasing methyltransferase activity from 14.0 +/- 0.64 in aldosterone-depleted cells to 31.8 +/- 2.60 methyl ester cpm/microg protein per hour in aldosterone-treated cells. Three known methyltransferase inhibitors reduce the aldosterone-induced increase in methyltransferase activity. One of these inhibitors, the isoprenyl-cysteine methyltransferase-specific inhibitor, S-trans, trans-farnesylthiosalicylic acid, completely blocks aldosterone-induced protein methylation and also aldosterone-induced short-circuit current. Aldosterone induces protein methylation in two molecular weight ranges: near 90 kDa and around 20 kDa. The lower molecular weight range is the weight of small G proteins, and aldosterone does increase both Ras protein 1.6-fold and Ras methylation almost 12-fold. Also, Ras antisense oligonucleotides reduce the activity of Na(+) channels by about fivefold. We conclude that 1) protein methylation is essential for aldosterone-induced increases in Na(+) transport; 2) one target for methylation is p21(ras); and 3) inhibition of Ras expression or Ras methylation inhibits Na(+) channel activity.

Characterization of polyisoprene by temperature gradient interaction chromatography

Temperature gradient interaction chromatography (TGIC) analysis of polyisoprene (PI) is reported. PI can be fractionated in terms of molecular weight with high resolution by TGIC using a C18 bondedd silica column as the stationary phase and a mixture of CH 2 Cl 2 /CH 3 CN (80/20. v/v as the mobile phase. The temperature was increased during the elution from 5°C to 34°C to optimize the fractionation of high molecular weight PI. The relatively poor resolation in the low molecular weight range was improved by changing the eluent composition. For example, all the oligomeric species from the unimer to the 29mer of a low molecular weight PI (average mol. wt.: 900) were fully resolved with the mixed eluent of CH 2 Cl 2 / CH 3 CN (50/50, v/v) and a linear temperature program from 6°C to 40°C. In addition, simultaneons site exclusion chromatography and TGIC fractionation of PI/polystyrene, PI/poly(methylmethacrylate) mixtures are also reported.

Towards highly functionalized and semi-rigid polyzwitterions, 2. Poly(zwitterionic isocyanides): synthesis and specific properties

Selective quaternization of the tertiary amino site of N,N-dimethyl-N-(3-isocyanopropyl)amine by 1,3-propanesultone or 2,2-dicyanoketene-ethylene acetal quantitatively yields the zwitterionic isocyanides of the ammoniopropanesulfonate (SI, —N+(CH3)2—(CH2)3—SO3–) or ammonioethoxydicyanoethenolate (EI, —N+(CH3)2—(CH2)2—O—CO—C–(CN)2) type, respectively. Their polymerization initiated with NiCl2·6 H2O in methanol (SI) or in N,N-dimethylformamide (EI) solution leads with high yields (>70%) to the corresponding poly(isocyanides) in a rather low molecular weight range (DPw ˜ 80–600). PSI is soluble in a few organic protic solvents such as glycol or m-cresol and displays typical UCST behavior in pure water (Tc ≈ 35°C) with “salting in” effects in the presence of LiClO4. PEI is soluble in a few dipolar aprotic solvents such as DMF, NMP or DMSO with typical LCST behavior and “salting in” effects in the presence of LiCl; secondly, in fairly concentrated KSCN aqueous solutions (>1 M) with a typical UCST behavior strongly dependent on salt concentration (dT/d[KSCN] ≈ 252°C·L·mol–1). Analysis of the [η] – Mw data for PSI (0.05 M LiClO4 in H2O) and PEI (0.05 M LiCl in DMF) according to the Bohdanecky's approximation of the Yamakawa-Fujii theory for wormlike chains allows to estimate their persistence length to be about 60 Å for a hydrodynamic diameter of about 15 Å. For polymer volume fractions Φp > 0.30, the PSI/glycol gels display local nematic order as revealed by polarizing optical microscopy and small angle X-ray scattering (Bragg spacing d ∝ Φp–0.45). The two poly(isocyanides) are non-crystalline but slightly birefringent polymers showing only local order (one SAXS peak). PSI dissolves stoichiometric amounts of NaB(C6H5)4, LiClO4, NaI and NaSCN to yield amorphous and birefringent blends which display optimized long range order in the latter case: a hexagonal bidimentional lattice of zwitterionic cylinders spreading over a coherence length of about 300 Å.

Towards highly functionalized and semi-rigid polyzwitterions, 2. Poly(zwitterionic isocyanides): synthesis and specific properties

Selective quaternization of the tertiary amino site of N,N-dimethyl-N-(3-isocyanopropyl)amine by 1,3-propanesultone or 2,2-dicyanoketene-ethylene acetal quantitatively yields the zwitterionic isocyanides of the ammoniopropanesulfonate (SI, —N+(CH3)2—(CH2)3—SO3–) or ammonioethoxydicyanoethenolate (EI, —N+(CH3)2—(CH2)2—O—CO—C–(CN)2) type, respectively. Their polymerization initiated with NiCl2·6 H2O in methanol (SI) or in N,N-dimethylformamide (EI) solution leads with high yields (>70%) to the corresponding poly(isocyanides) in a rather low molecular weight range (DPw ˜ 80–600). PSI is soluble in a few organic protic solvents such as glycol or m-cresol and displays typical UCST behavior in pure water (Tc ≈ 35°C) with “salting in” effects in the presence of LiClO4. PEI is soluble in a few dipolar aprotic solvents such as DMF, NMP or DMSO with typical LCST behavior and “salting in” effects in the presence of LiCl; secondly, in fairly concentrated KSCN aqueous solutions (>1 M) with a typical UCST behavior strongly dependent on salt concentration (dT/d[KSCN] ≈ 252°C·L·mol–1). Analysis of the [η] – Mw data for PSI (0.05 M LiClO4 in H2O) and PEI (0.05 M LiCl in DMF) according to the Bohdanecky's approximation of the Yamakawa-Fujii theory for wormlike chains allows to estimate their persistence length to be about 60 A for a hydrodynamic diameter of about 15 A. For polymer volume fractions Φp > 0.30, the PSI/glycol gels display local nematic order as revealed by polarizing optical microscopy and small angle X-ray scattering (Bragg spacing d ∝ Φp–0.45). The two poly(isocyanides) are non-crystalline but slightly birefringent polymers showing only local order (one SAXS peak). PSI dissolves stoichiometric amounts of NaB(C6H5)4, LiClO4, NaI and NaSCN to yield amorphous and birefringent blends which display optimized long range order in the latter case: a hexagonal bidimentional lattice of zwitterionic cylinders spreading over a coherence length of about 300 A.

Characterisation of soluble residual chemical oxygen demand (COD) in anaerobic wastewater treatment effluents

Anaerobic wastewater treatment processes cannot usually achieve discharge levels of COD without some form of post-treatment due to the high levels of soluble residual COD in the effluent. However, there is very little information in the literature on the nature of this material, and hence the aim of this work was to characterise effluents from several different anaerobic processes by their: molecular weight (MW) distributions (using the techniques of ultrafiltration and size exclusion chromatography); biodegradability (both aerobic and anaerobic) and activated carbon adsorption characteristics. The MW distribution data indicated that the majority (up to 89% w/w) of the material present in the effluents was in the low MW range (i.e. MW<1kDa), although there was a significant amount (up to 22% w/w) in the high MW range (i.e. MW>300kDa). Differences in the distributions were observed according to reactor type, with effluents from anaerobic baffled reactors (ABRs) containing a higher proportion of high MW material than effluents from other reactor types. Aerobic degradation of the effluents was significantly more successful than anaerobic, despite the fact that the low MW material was found to be the most difficult to degrade aerobically. Activated carbon adsorption revealed that the low MW material was more difficult to adsorb than the high MW compounds. The data was fitted to Freundlich, Langmuir and BET isotherms and it was concluded that the Freundlich model was the most accurate for predicting removal efficiencies especially with regard to scale up. Some generic patterns emerged with respect to the characterisation of the effluents and these will assist in decisions regarding post-treatment. Nevertheless, in order for these generic patterns to be confirmed more work is needed on characterising effluent samples from anaerobic treatments.

The Effect of Reoxygenation with 21% or 100% Oxygen on Hypercapnic-Hypoxia Induced DNA Damage in Cerebral Cortices of Newborn Piglets † 1024

Previous studies have shown that both hypoxia, and hypoxia followed by reoxygenation with either 21% or 100% oxygen are associated with significant generation of free radicals in the cerebral cortices of newborn piglets. The present study investigates the DNA degradation pattern associated with cell death following cerebral hypercapnic hypoxia. Studies were performed on groups(n=4 each) of anesthetized and ventilated newborn piglets. Group 1 was a room air control, and Groups 2 and 3 were exposed to 1hr of hypercapnic-hypoxia followed by reventilation with either 21% or 100% oxygen for 45 minutes, respectively. Group 4 was made hypercapnic and hypoxic but was not reventilated. Hypercapnic hypoxia was achieved by slow inhalation of CO2 and a reduction in the FiO2 to 0.05-0.07. Prior to reventilation, mean values for pH, PaO2 and PaCO2 were 7.05, 20 mmHg and 82 mmHg respectively. After the period of reventilation, brain tissue was removed for analysis. ATP and phosphocreatine (PCr) concentrations were determined biochemically as indices of brain tissue energy metabolism. Mean concentrations of ATP in Grp 1, and the 21% (Grp 2) and 100% (Grp 3) reventilated groups were 4.26, 5.18 and 4.40 mmol/ g brain; PCr values were 3.71, 3.65 and 3.18 mmol/g brain, respectively. Brain cell nuclei and DNA were isolated and the pattern of DNA degradation was assessed using 1% agarose gel-electrophoresis. The gel pattern in Group 1 showed a single band of DNA. High-molecular weight DNA appeared as a large smear in Groups 2 and 3. Although the gel pattern in Group 4 revealed DNA degradation predominantly as a continuous smear, discrete bands of DNA fragments were identified in the lower molecular weight range (2,000-100 bp). The presence of a smear as opposed to a ladder-type pattern implies random fragmentation of DNA, possibly mediated by free radicals, and not due to the action of specific endonucleases. We speculate that irrespective of the O2 concentration used during reoxygenation, the molecular structure of the DNA is altered without being cleaved into small fragments.

Liquid‐liquid phase separation in polysulfone/solvent/water systems

The cloud point curves for polysulfone (PSf)/solvent/water systems were determined by a titration method. A small amount of water was needed to induce liquid-liquid demixing and the temperature effect was small. From numerical calculations, it was found that the binary interaction parameters for the PSf/solvent/water system enlarges the homogeneous region in the phase diagram with a smaller nonsolvent-polymer interaction parameter χ13, a greater nonsolvent-solvent interaction parameter χ12, and a smaller solvent-polymer interaction parameter χ23 and the effect of polymer molecular weight was negligible except in the range of low molecular weight. The phase diagrams, calculated with constant χ12 that was chosen from the concentration-dependent interaction parameter g12 value of the concentration range, were similar to the results obtained with g12. The slope of the tie lines indicated that demixing of the ternary system occurred at relatively similar nonsolvent concentration in both phases. A value of 2.7 for the water-PSf interaction parameter was obtained by fitting the experimental cloud point curve with the calculated binodal lines. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2643–2653, 1997

Liquid-liquid phase separation in polysulfone/solvent/water systems

The cloud point curves for polysulfone (PSf)/solvent/water systems were determined by a titration method. A small amount of water was needed to induce liquid-liquid demixing and the temperature effect was small. From numerical calculations, it was found that the binary interaction parameters for the PSf/solvent/water system enlarges the homogeneous region in the phase diagram with a smaller nonsolvent-polymer interaction parameter χ13, a greater nonsolvent-solvent interaction parameter χ12, and a smaller solvent-polymer interaction parameter χ23 and the effect of polymer molecular weight was negligible except in the range of low molecular weight. The phase diagrams, calculated with constant χ12 that was chosen from the concentration-dependent interaction parameter g12 value of the concentration range, were similar to the results obtained with g12. The slope of the tie lines indicated that demixing of the ternary system occurred at relatively similar nonsolvent concentration in both phases. A value of 2.7 for the water-PSf interaction parameter was obtained by fitting the experimental cloud point curve with the calculated binodal lines. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2643–2653, 1997

Antigenic analysis of Rhodococcus equi preparations using different horse sera

An R. equi vaccine, prepared under conditions which induce the expression of many antigens, and which has given encouraging results in field trials, was analyzed by SDS-PAGE and immunoblots and compared with other R. equi preparations: a preparation made in with the same technique from a nonvirulent isolate (virulence associated protein negative, VapA-negative); a whole cell preparation of a VapA-positive R. equi, prepared as a standard bacterin; and a semipurified VapA preparation (APTX). The antigens in these preparations were analyzed using hyperimmune sera (from adult horses vaccinated with the R. equi vaccine), passively and actively immunized foals' sera, asymptomatic but serologically positive foals' sera, sera from R. equi pneumonic foals, an equine APTX antiserum, and a VapA monoclonal antibody (Mab). The vaccine under study had many proteins in high concentrations. Hyperimmune sera reacted strongly with vaccine antigens in the high molecular weight regions. In the low molecular weight range, it reacted in the 14 and less kDa zone. Sera from passively immunized foals reacted similarly but not so strongly. Actively immunized foals gave very weak reactions. With the APTX extract, the Mab reacted with bands at 15–17, 44 and 66 kDa; it reacted weakly with the whole cell and not with the VapA-negative preparations. The APTX antiserum and the Mab reacted strongly with the vaccine at the 14 and less kDa zone, and also with bands at 21, 44 and 66 kDa and very tenuously at 18 kDa, but not in the expected 15–17 kDa zone, suggesting that the native form of VapA is altered but without loss of antigenicity in the vaccine preparation. Our results suggest that other higher molecular weight antigens, in addition to VapA, may be important in inducing antibodies that protect young foals from R. equi pneumonia. These antigens are in high concentrations and in an immunogenic form in the vaccine.

Proteolytic Activity in the Seminal Plasma of the Mud Crab, Scylla serrata (Forskal)

The protein composition and proteolytic activity of the seminal plasma of the brachyuran crab, Scylla serrata, were studied. The seminal plasma proteins are mainly glycoproteinaceous, many of them lying in the lower molecular weight range as evidenced by high performance liquid chromatography (HPLC). Protease activity was detected using casein as the substrate. The enzyme was highly active in the pH range 7.0–9.0, exhibiting maximum activity at pH 8.0. The enzyme was active at temperatures up to 40°C. Enzyme activity was inhibited by the serine protease inhibitor Phenyl Methyl Sulfonyl Fluoride (PMSF) but not by the metalloprotease inhibitor Ethylene Diamine Tetra Acetic acid (EDTA) indicating that it is a serine protease. The effect of substrate concentration on the enzyme activity was also studied. The proteins were fractionated by gel filtration chromatography on Sephadex G-200 column. A clear zone of proteolysis was detected against a stained background in the third fraction when electrophoresed on casein-containing polyacrylamide gel. The molecular weight of this fraction was determined to be approximately 6000D. The protease activity in the seminal plasma may be related to the formation and/or dissolution of sperm plug formed during mating in these brachyuran crabs.

The effect of molecular weight on the rheological and tensile properties of poly(ε-caprolactone)

Abstract Molecular weight fractions of poly(e-caprolactone) (PCL) were obtained by catalytic degradation and characterised by theological measurements. Pseudoplastic behaviour was found in the higher molecular weight fractions, the degree of which lessened as the thermal motion of the polymer chains increased. The exponential factor of the viscosity/ molecular weight relationship indicated that the fractions were above the critical molecular weight for viscous flow determined as 15–16 000. Activation energies for viscous flow showed an inverse relationship with molecular weight, the significance of which has been discussed. Melt quenching resulted in lower melt viscosities due to a reduction in melting point by formation of additional amorphous regions. Tensile measurements indicated that PCL was a brittle material with a molecular weight of > 16 900 being required for free film formation. Elongation and tensile strength values increased with molecular weight although remaining low, indicating both the low molecular weight range investigated and the high degree of PCL crystallinity. PCL showed that it had rheological and tensile properties that with modification would make it a potential candidate in the novel technique of powder coating of pharmaceutical compacts.

Low Molecular Weight Heparin Is Responsible for the Anti-Xa Activity of Desmin 370

Dermatan sulphate does not catalyse the inactivation of factor Xa. However, the low molecular weight (LMW) dermatan sulphate Desmin 370 has been shown to generate circulating anti-Xa activity following administration to humans. Using a single batch of Desmin 370, we measured 3 U/mg of anti-Xa activity by amidolytic assay in vitro. The material responsible for this activity had a lower molecular weight range (6000 and 1800 Da) than Desmin 370 and was more highly sulphated than the bulk of the drug. Heparinase digestion of Desmin 370 eliminated 90% of the in vitro anti-Xa activity without significantly interfering with its ability to potentiate inactivation of thrombin by HCII, suggesting that the anti-Xa activity is not due to dermatan sulphate and is probably heparin. When 125I-labelled Desmin 370 together with 40 mg/kg carrier drug was administered intravenously to a rabbit, anti-Xa activity was readily detectable in the plasma for up to 10 h and had a longer half-life than the sulphated radiolabel. Most of this anticoagulant activity was recovered from the plasma by Polybrene affinity chromatography and was probably a sulphated glycosaminoglycan. Administration of the heparinase-digested drug to a rabbit resulted in 70% less anti-Xa activity than the undigested drug. We conclude that Desmin 370 contains detectable quantities of biologically active low molecular weight heparin, which is responsible for persistent anti-Xa activity following intravenous administration.

Purification and characterization of a low molecular weight zinc binding protein from human placenta.

A low molecular weight, native zinc binding, cytosolic protein (LMZP) has been isolated, purified and characterized from human normal term placenta. Gel filtration of heat treated placental cytosol after sequential acetone precipitation (80% ppt) revealed a major zinc binding protein in the range of low molecular weight. This partially purified zinc binding fraction was further fractionated on DEAE-Sephadex A-25. The zinc was eluted in one of the three peak fractions. Further, the purity of zinc binding protein was confirmed on fast protein liquid chromatography (FPLC). The purified placental LMZP was homogenous on SDS-polyacrylamide gel electrophoresis with a single band. Ultraviolet (UV) spectrum of LMZP showed an absorption maximum at 257 nm which disappeared at pH 2. Molecular weight of LMZP as determined by gel chromatography, SDS-polyacrylamide gel electrophoresis and amino acid analysis was 6 kDa. It was calculated that 1 g atom of zinc was bound to 1 mole of the LMZP. Unlike in classical metallothionein, the amino acid composition of placental LMZP revealed the presence of aromatic amino acids, lower content of cysteine and higher content of histidine, glutamic acid and aspartic acid (10, 9 and 5 residues/mole, respectively).