Polyvinyl Pyrollidone Research Articles

Direct micropatterning of high dielectric BaTiO 3 films by laser-induced pyrolysis with a nano-crystalline seeding technique

A direct patterning method of dielectric BaTiO 3 (BT) films is proposed, which applies laser-induced pyrolysis in combination with nano-crystalline seeding technique. A precursor solution of a BT complex alkoxide containing BT nano-crystalline particles with polyvinylpyrollidone (PVP) as dispersion stabilizer was spin-coated on Pt substrate. An Ar + laser beam was focused and scanned on spin-coated BT films, which induced pyrolysis and crystallization of the films with spatial selectivity. Micropatterns were obtained by striping laser-unirradiated regions on the films with HCl aqueous solution. Raman spectra of the micropattern confirmed that the structures were tetragonal crystalline BT. Clear micropatterns with a line width of ca. 3 μm and an interval of 5 μm were formed at PVP concentrations of 25 and 50 kg/m 3. The dielectric constant and dissipation factor of the film fabricated at a laser energy density of 27 MW/cm 2 and a scanning speed of 25 μm/s attained 76.2 and 0.07, respectively, for a measurement frequency of 100 kHz.

Bacteria and cell cytocompatibility studies on coated medical grade titanium surfaces

Acute and chronic osteomyelitis caused by staphylococci can be difficult to treat by conventional means and often has marked consequences for the patient. Current methods of treatment involve the use of systemic antibiotics, the local implantation of nondegradable drug carriers, and surgical debridement. A possible solution that could prevent initial bacterial adhesion could be to modify the implant surface with an antimicrobial coating while maintaining biocompatibility to host cells. This study describes the cytocompatibility evaluation of different coatings (poly(D,L-lactide) (PDLLA), politerefate (PTF), calcium phosphate/anodic plasma-chemical treatment (CaP/APC), polyurethane (PU), and polyvinylpyrollidone (PVP) on titanium surfaces with and without chlorhexidine diacetate (CHA) to Staphylococcus aureus, Staphylococcus epidermidis, and hTERT human fibroblasts. Surface characterization of the coatings showed no significant variation in the roughness or hydrophobicity of the coated surfaces, except the CaP/APC surface that was porous yet the smoothest, and PVP, PVP+CHA, and CaP/APC+CHA that were more hydrophilic in nature than the others. On the surfaces without CHA, both staphylococcal strains and spread fibroblasts were observed, but on the CHA impregnated surfaces few bacteria and no intact fibroblasts were seen. Flow cytometry found fewer bacteria in the media and on the surfaces containing CHA in comparison to the surfaces without CHA. The release kinetics varied from slow (over 200 h) to burst release: PDLLA>PTF>PU>CaP/APC=PVP. This study showed that PDLLA and PTF have the best potential as coatings on implants for drug delivery, as they were cytocompatible to hTERT fibroblasts, eluted CHA effectively, and passed mechanical testing. The actual release kinetics of PDLLA and PTF are important, as the amount of CHA present should remain above the minimal inhibitory concentration value for a limited time before disappearing completely.

Electrochemical rectification at electrode surface modified with poly (acrylic acid) and decane thiol

Gold surface modified with a two-component system consisting of poly (acrylic acid) (PAA) by electropolymerizing acrylic acid (AA) and decane thiol (DT), further functionalized with ferrocene monocarboxylic acid (FMC) through covalent linkage, was used to demonstrate mediated electron transfer resulting in a unidirectional flow of current. The electrode surface was modified using two different configurations. In Configuration 1 (Config. 1), electrode surface modified with FMC showed rectification behavior when contacted with a solution containing methylene blue (MB). In Configuration 2, redox-active bilayer was constructed using polyvinyl pyrollidone (PVP) and hexaamineruthernium (II) chloride [Ru(NH3)6]2+ showed rectification characteristics. The continuous rectification property of the redox-active bilayer is achieved by releasing the trapped [Ru(NH3)6]3+ in the outer layer using a reductant (ascorbic acid). Spectroelectrochemical measurements were made to study the reduction property of the ascorbic acid. Atomic force microscopic images and impedance measurements were also made on the modified electrode surfaces to explore the compactness of the first layer (PAA and PAA/DT).

Effect of Hydrophilic Polymer on Solubilization of Fenofibrate by Cyclodextrin Complexation

The present work investigates the possibility of improvement of the complexation efficiency of cyclodextrin towards a drug by adding a third auxiliary component (hydrophilic polymer). Phase solubility Analysis at 25 °C was used to investigate the interaction of the drug in both the binary systems (viz. Drug-Cyclodextrin and Drug-Polymer) and the ternary system (Drug-Cyclodextrin-Polymer). The combined use of polymer and cyclodextrin was clearly more effective in enhancing the aqueous solubility of the fenofibrate in comparison with the corresponding drug-cyclodextrin or drug-polymer binary systems. Hydrophilic polymers increased the complexation efficacy of cyclodextrin towards fenofibrate (as shown by the increased stability constants of the complexes). Polyvinyl Pyrollidone (PVP) was found to be most effective in enhancing the solubilization of fenofibrate by β-Cyclodextrin, the best results were obtained in ternary system with β-Cyclodextrin in presence of 1%w/v (PVP). Formulated ternary system with optimized drug:cyclodextrin:polymer ratio of 1:3.5:1 w/w resulted in a significant improvement in the dissolution rate of fenofibrate and showed 90% dissolution efficiency (D.E) as compared to around 15% and 83% of the plain drug and binary system respectively. DSC studies was carried out to characterize the ternary complex.

Sol-Gel Synthesis of Thick Ta2O5 Films for Photonic Band Gap Materials

ABSTRACTAdvances in microelectromechanical systems has generated an ever growing demand for novel insulating material applicable to high temperature systems. Photonic bandgap materials are appealing for such applications, specifically Ta2O5 due to its high index of refraction, refractory nature and negligible absorbance in the infrared region. The challenge faced in the realization of such materials is the synthesis of crack free Ta2O5 films whose thickness is in the order of a quarter wavelength of the incident infrared radiation.This work seeks to investigate the effect of addition of polyvinyl pyrollidone (PVP) as a binder material in the sol gel synthesis of thick, uniform and crack free Ta2O5 films. Incorporation of PVP into the sol precursor has enabled uniform and crack free films with thicknesses of up to 2.4 microns to be realized. Chemical probing of the precursor was conducted via TGA, FTIR, and NMR analysis of the sol to elucidate the processes behind this film formation. The calcined oxide films were characterized via SEM, XRD and XPS.

Crystallo-co-agglomeration: A novel technique to obtain ibuprofen-paracetamol agglomerates

The purpose of this research was to obtain directly compressible agglomerates of ibuprofen-paracetamol containing a desired ratio of drugs using a crystallo-co-agglomeration technique. Crystallo-co-agglomeration is an extension of the spherical crystallization technique, which enables simultaneous crystallization and agglomeration of 2 or more drugs or crystallization of a drug and its simultaneous agglomeration with another drug or excipient. Dichloromethane (DCM)-water system containing polyethylene glycol (PEG) 6000, polyvinyl pyrollidone, and ethylcellulose was used as the crystallization system. DCM acted as a good solvent for ibuprofen and bridging liquid for agglomeration. The process was performed at pH 5, considering the low solubility of ibuprofen and the stability of paracetamol. Loss of paracetamol was reduced by maintaining a low process temperature and by the addition of dextrose as a solubility suppressant. The agglomerates were characterized by differential scanning calorimetry, powder x-ray diffraction (PXRD), and scanning electron microscopy and were evaluated for tableting properties. The spherical agglomerates contained an ibuprofen-paracetamol ratio in the range of 1.23 to 1.36. Micromeritic, mechanical, and compressional properties of the agglomerates were affected by incorporated polymer. The PXRD data showed reduction in intensities owing to dilution and reduced crystallinity. Thermal data showed interaction between components at higher temperature. Ethylcellulose imparted mechanical strength to the agglomerates as well as compacts. The agglomerates containing PEG have better compressibility but drug release in the initial stages was affected owing to asperity melting, yielding harder compacts. The agglomeration and properties of agglomerates were influenced by the nature of polymer.

Legume seed inoculation technology—a review

Inoculation of legume seed is an efficient and convenient way of introducing effective rhizobia to soil and subsequently the rhizosphere of legumes. However, its full potential is yet to be realised. Following widespread crop failures, the manufacture of high quality inoculants revolutionised legume technology in Australia in the 1960s. Many improvements to inoculants and the advent of an inoculant control service ensured that quality was optimised and maintained. Minimum standards for the number of rhizobia per seed were set after consideration of several factors including seed size and loss of viability during inoculation. Despite manufacturers' recommendations for storage and application of inoculants, there is a distinct lack of control over the inoculation process; hence the full potential of high quality products may not always be achieved. The efficacy of inoculation varies depending on several factors, all of which affect the number of viable rhizobia available for infection of legume roots. Increased numbers of viable rhizobia per seed by application of inoculant above the commercially recommended rate, results in a continued linear increase in nodulation and yield. Several studies have reported yield increases of up to 25%. However, applying higher quantities of inoculant is uneconomical and technically difficult. Alternatively, higher numbers of viable rhizobia per seed may be achieved by improving survival during seed inoculation. Despite recognition of the factors affecting survival of rhizobia on seed and a substantial demand for commercially pre-inoculated legume seed, poor survival is still a major concern. Desiccation, temperature and seed coat toxicity all influence survival of rhizobia on seed. Their adverse effects may be ameliorated by selecting tolerant rhizobial strains and legume seed cultivars with low toxicity or artificially, by the use of additives in the seed coating. The accumulation of the desiccant protectant trehalose in strains of rhizobia, may result in better survival under desiccation stress. Similarly, the accumulation of exopolysaccharide (EPS) may act as a barrier reducing excessive water loss. Polymeric adhesives such as gum arabic, methyl cellulose and polyvinyl pyrollidone (PVP) have improved survival. However, studies of additives used in inoculation have been ad hoc and little of their mode of action is understood. A better understanding of the mechanisms involved in the protection of rhizobia from adverse conditions will assist in defining the optimum conditions for seed inoculation and storage to ensure a higher quality product for farmers at the time of sowing.

Oral delivery of insulin from enteric-coated capsules containing sodium salicylate: effect on relative hypoglycemia of diabetic beagle dogs

The hypoglycemic effect of Eudragit S100 enteric-coated capsules containing sodium salicylate as an absorption promoter formulated with insulin in various ways: as physical mixture, by wet granulation or in suppository bases (polyethylene glycol 4000 or Witepsol W35) was studied in hyperglycemic beagle dogs. The capsules containing insulin formulated with sodium salicylate (50 mg) and prepared by either physical mixing or wet granulation using 10% polyvinyl pyrollidone gave almost the same results producing a maximum reduction in plasma glucose level ( C max) of 81.53±8.21 and 79.59±5.75%, T max of 6 and 5 h, area under the curve (AUC) of 69.37±48.64 and 57.98±23.15% reduction hour (% red. h) and resulting in relative hypoglycemia (RH) of 8.73±6.12 and 7.29±2.91%, respectively. Formulation of insulin with sodium salicylate in PEG 4000 produced a lower AUC of 37.30±10.36% red. h and RH of 4.69±1.3%. While, formulation in Witepsol W35 (0.5, 1.0 and 2.0 g) that was sieved to produce particle size of 180–315 μm and filled in enteric-coated capsules showed that formulating insulin and sodium salicylate in 1 g base is the best formulation. It produced 25% reduction in plasma glucose levels of the hyperglycemic beagle dogs at T max of 4 h and the largest AUC of 100.10±25.72% red. h, resulting in the highest RH of 12.59±3.23%. In conclusion, 25–30% reduction in plasma glucose levels and RH of about 12.5% relative to subcutaneous injection of regular soluble insulin can be achieved by formulating insulin in Witepsol W35 (1 g) with sodium salicylate (50 mg) as an absorption promoter, reducing the resulting mass into particle size 180–315 μm, packing into hard gelatin capsules and coating with Eudragit S100.

Effect of Bioadhesive Polymers, Sodium Salicylate, Polyoxyethylene-9-lauryl Ether, and Method of Preparation on the Relative Hypoglycemia Produced by Insulin Enteric-Coated Capsules in Diabetic Beagle Dogs

ABSTRACTThe hypoglycemic effect of oral insulin capsules coated with pH-dependent Eudragit® S100 and containing various absorption promoters was studied in hyperglycemic beagle dogs. The absorption enhancers used were bioadhesive polymers, sodium salicylate, and non-ionic surfactants. A comparative study of the bioadhesive polymers, polycarbophil (PC), hydroxypropyl methylcellulose (HPMC), and carbopol 934 in insulin-coated capsules revealed no significant difference between the insulin capsules containing these polymers, giving relative hypoglycemia (RH) values ranging from 4.3±2.3% to 6.5±5.1%. It was also found that the method of preparation of the mixture of the bioadhesive polymer with insulin either by physical mixing or freeze-drying did not affect the RH values obtained. Sodium salicylate, when used in insulin enteric-coated capsules (50 mg) mixed with insulin as a physical mixture, or prepared by wet granulation using 10% polyvinyl pyrollidone (PVP), or by freeze-drying, produced RH values ranging from 7.3±2.9% to 9.4±3.7%. When sodium salicylate (100 mg) was used with insulin in freeze-dried granules an RH value of 10±2.6% was produced. As the dose of insulin increased from 6 to 9 U/kg, the area under curve (AUC) of the enteric-coated capsules containing 50 mg sodium salicylate increased from 73.2±27.8% to 121.4±102.7% reduction, but the RH did not change significantly. Insulin capsules containing polyoxyethylene-9-lauryl ether (POELE) used in its optimum concentration (2%), found in these experiments, produced RH of 9.5±6.8% when prepared as granules by wetting with a few drops of absolute alcohol in the presence of PC (50 mg). Insulin capsules containing lower (1%) or higher (3%) concentrations of POELE and prepared with PC, 50 mg by wet granulation produced lower RH of about 6%. The enteric-coated oral insulin capsules containing insulin (6 or 9 U/kg) and sodium salicylate (50 mg) as an absorption promoter, together with the bioadhesive polymer polycarbophil (50 mg), and prepared either by wet granulation using ethanol or by freeze-drying, are the best formulations to be used. They achieved a reduction in plasma glucose levels of about 25–30% and RH of about 10%. Also insulin (9 U/kg) capsules containing 2% POELE produced a 28% reduction in plasma glucose levels and RH of 9.6±6.8%.

New Approach for Determination of Macroscopic Binding Constants of Ligands to Macromolecules

A new method has been developed for determining macroscopic binding constants of a few surfactants to some macromolecules. Then, the binding of ionic surfactants (cetyltrimethyl ammonium bromide, tetradecyltrimethyl ammonium bromide, and sodium tetradecyl sulfate) [STS]) to macromolecules (bovine serum albumin, human serum albumin, and polyvinyl pyrollidone was investigated. The binding constants and binding isotherms were calculated using this new method. Experimental data were obtained through a potentiometry technique. Finally, the results obtained were compared with the results obtained based on the Wyman binding potential concept.

Hormonal regulation of the glucose transporter GLUT I in the lactating rat mammary gland.

Conference Article| February 01 1992 Hormonal regulation of the glucose transporter GLUT I in the lactating rat mammary gland H.A.C. FAWCETT; H.A.C. FAWCETT 1Hannah Research Institute, Ayr KA6 5HL, U.K. Search for other works by this author on: This Site PubMed Google Scholar S.A. BALDWIN; S.A. BALDWIN *Departments of Biochemistry & Chemistry and of Protein & Molecular Biology, Royal Free Hospital School of Medicine (University of London), Rowland Hill Street, London NW3 2PF, U.K. Search for other works by this author on: This Site PubMed Google Scholar D.J. FLINT D.J. FLINT 1Hannah Research Institute, Ayr KA6 5HL, U.K. Search for other works by this author on: This Site PubMed Google Scholar Biochem Soc Trans (1992) 20 (1): 17S. https://doi.org/10.1042/bst020017s Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter LinkedIn Cite Icon Cite Get Permissions Citation H.A.C. FAWCETT, S.A. BALDWIN, D.J. FLINT; Hormonal regulation of the glucose transporter GLUT I in the lactating rat mammary gland. Biochem Soc Trans 1 February 1992; 20 (1): 17S. doi: https://doi.org/10.1042/bst020017s Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Society Transactions Search Advanced Search Keywords: CB154, bromocryptine, GH, growth hormone, GLUT, glucose transporter gene family type, GT, glucose transporter(s), IGF-I, insulin-like growth factor I, PRL, prolactin, PVP, polyvinyl pyrollidone This content is only available as a PDF. © 1992 Biochemical Society1992 Article PDF first page preview Close Modal You do not currently have access to this content.

Influence of ozone and acid mist on the contents of gibberellic acid (GA 3) in spruce needles ( Picea abies) (L.) Karst.

The phytohormone GA 3 in needles from 4-year-old Norway spruce trees was analyzed after treatment with ozone and acid mist in environmental chambers under controlled conditions. GA 3 was extracted with methanol from the lyophilized material. Subsequent purification steps included the use of polyvinylpyrollidone (PVP), cartridge reversed-phase purification, ethylacetate extraction and HPLC. The GA 3 was determined in the methylated form by means of a highly specific and sensitive enzyme immunoassay. Higher GA 3 contents were detected in young needles (year 1987) as compared to older ones (year 1986). However, no statistically significant differences were found in the GA 3 levels between the controls and the needles of trees which were treated with increased levels of ozone and acidic mist.

Deposition of amorphous mercury selenide thin films by aqueous reactive solution growth technique

A chemical method has been developed for the preparation of Mercury selenide (HgSe) thin films on glass substrate at room temperature. Mercury selenide thin films was prepared by using mercury formamide a novel complex compound and sodium selenosulphate as a selenide releasing agent. The adherence and uniformity of the film was improved by adding polyvinyl pyrollidone as minor additive. X-ray diffraction, optical absorption and electrical measurements were performed to characterize the deposition of Mercury selenide. The films were found to be amorphous, p-type semiconductor with an energy gap of 1.42eV.

Effect of gas—liquid interfaces on the growth of suspended mammalian cells: mechanisms of cell damage by bubbles

The hypothesis is examined that cell death in sparged systems for suspended mammalian cell culture is associated only with the region of bubble disengagement at the medium surface. The effects of bubble diameter, superficial gas velocities, and the nonionic surfactant Pluronic F-68 on hybridoma viability have been reported previously. The work reported here extends these experimental studies to a range of bubble columns and for the culture of not only hybridoma but also myeloma, BHK-21, and lymphoblastoid (RAJI) cells lines. In short bubble columns, small bubbles and high bubble frequencies are more detrimental to hybridoma cells than BHK-21 suspension cells. Both fetal calf serum (FCS) and Pluronic F-68 have concentration-dependent protective effects on cells. In defined serum-free media, gross mechanical disruption of hybridoma cells and loss of cells and medium components at the medium surface occur on sparging. With increasing bubble column height, a progressively increasing retention of cell viability is observed for all cell types. By implication, this is because the proportion of time spent by cells in the “destructive zone” at the medium surface is reduced as the column height increases. Finally, two mechanisms of cell damage are proposed: damage due to rapid oscillations caused by bursting bubbles, and damage due to shearing in draining liquid films (or lamellae) in foams. It is proposed that Pluronic (and other polymers such as polyethylene glycol and polyvinyl pyrollidone) act as cell protective agents by stabilizing foams and thereby reducing film drainage and bubble bursting in the vicinity of cells.

Acid phosphatases of the mosquito Culex tarsalis coquillett

1. 1. Spectrophotometric and isoelectric focusing (IEF) electrophoretic characterization of the acid phosphatases (ACP) of the mosquito, Culex tarsalis, are presented. 2. 2. ACP hydrolysis of P- nitrophenylphosphate ( P np ) was optimal at 37°C, pH 5.25 in the presence of 15 mM MgCl 2 and 0.1% (w/v) polyvinylpyrollidone (PVP). V max and K m values varied significantly between the various mosquito strains examined. 3. 3. Several divalent cations (i.e. Mn 2+, Ca 2+, Ba 2+ and Co 2+), either the chloride or sulphate salts, were stimulatory for ACP. Both Cu 2+ and Fe 2+ (15 mM) were inhibitory. 4. 4. Slight inhibition (i.e. 10%) of ACP activity was observed with dithiothreitol (100 mM) and 50% inhibition by cysteine (100 mM). 5. 5. ACP activity was cyclic during the 15-day post-adult emergence period of the study. No significant differences were noted between the ACP specific activities of males and females nor between geographic strains. 6. 6. IEF electrophoresis revealed three α-naphthyl phosphate hydrolytic ACP isozymes within the pH 4.5–5.5 range (i.e. ACP 4.8, ACP 5.3 and ACP 5.5). 7. 7. IEF ACP isozymes were stimulated by PVP, Mg 2+, Zn 2+ and inhibited by cysteine, EDTA (except ACP 5.3) and NaF1. 8. 8. IEF detection of ACP with P np revealed an ACP isozyme (ACP 4.3) distinct from those ACP isozymes capable of α-naphthyl phosphate hydrolysis.

Preparation of 99 mTc-tin-phosphate polyvinyl pyrollidone stabilized colloid and distribution in bone marrow

Technetium-99 m-Sn-phosphate colloid was prepared in the presence of polyvinylpyrollidone(PVP), molecular weight 44,000, for bone marrow imaging. Size of the colloidal particles, as determined by coulter counter, microphotographic and electron microscopic studies was 15–35 nm. The colloid preparation was checked for the presence of any soluble components by Sephadex G-25 chromatography. Scintigraphy in rabbits showed a high concentration of the colloid in the bone marrow. Tissue distribution studies in rabbits showed 26.7% of the injected dose at 1 h post-injection in the bone marrow collected from femoral shaft and head. Although liver and spleen showed considerable levels of activity, kidneys and compact bone did not show any uptake. The colloid cleared from the blood exponentionally with a first phase showing a relatively fast clearance while in the second phase it disappeared more slowly. Uptake of the colloid in human bone marrow was close to that in the rabbit and thus clinical evaluation is warranted.

Alkaline phosphatases of the mosquito, Culex tarsalis coquillett

1. 1. Spectrophotometric and isoelectric focusing (IEF) electrophoretic characterization of the alkaline phosphatases (ALKP) of the mosquito, Culex tarsalis, are presented. 2. 2. With p-nitrophenylphosphate ( Pnp) as substrate, ALKP was optimally active at 37°C, pH 8.0, 30 mM MgCl 2, V max was 35.8 μmoles/10 min and the K m was 5.7 mM, with no demonstrable requirement for Zn 2+. 3. 3. The spectrophotometric enzyme(s) was stimulated by dithiothreitol, 2-mercaptoethanol, and polyvinylpyrollidone (PVP); inhibited by NaF, several alternative cations (Ca 2+, Ba 2+, Fe 2+, Cu 2+), and EDTA. 4. 4. ALKP activity was cyclic during the 15 day post-adult emergence period of the study. No significant differences were noted between the specific activities of males and females. 5. 5. IEF electrophoresis revealed 6 ALKP isozymes detected with α-naphthylphosphate within the pH range 4.0–5.5, with a second group of 3 rather indistinct species in the pH 6.0–7.0 range. 6. 6. IEF ALKP isozymes were stimulated by Mg 2+ and PVP and inhibited by EDTA (except ALKP 5.0) and cysteine; partial inhibition with phenylalanine. 7. 7. IEF detection of ALKP activity with Pnp indicated that the majority of the activity was localized in the pH 4.0–5.5 range, in close agreement with the α-naphthylphosphate results.

The influence of molecular weight on immunogenicity and suppressor cells in the immune response to polyvinylpyrollidone

The primary 19S immune response to the T-independent antigen polyvinylpyrollidone (PVP) is normally dependent on the molecular weight of the immunogen. The low molecular weight preparation, PVP 10 (molecular weight of 10,000), is apparently nonimmunogenic, whereas PVP 40 and PVP 360 induce significant antibody responses. Results show, however, that in the absence of T-cells PVP 10 is immunogenic both in vivo and in vitro. In addition, PVP 10 is shown to be a potent activator of suppressor T cells, as measured by the response of normal B cells to PVP 360 when such B cells are mixed with T cells or thymocytes primed with PVP 10.

The interaction of oxidation products of pyrogallol with poly-L-lysine. A model oxidative beer haze

Iodate oxidation of pyrogallol at pH 4 produces an agent capable of precipitation poly-l-lysine and lysozyme. This substance is neither purpurogallin nor one of its oxidation products. The solubility of the poly-l-lysine precipitate in 6m-guanidine hydrochloride and in 1m-NaOH indicates that hydrogen bonding is responsible for precipitation. While the oxidized pyrogallol solutions do not contain tannins detectable by the method ofChapon, polyvinylpyrollidone (PVP) does prevent precipitation. Once formed, the precipitate does not redissolve in PVP. The pyrogallol oxidation products have no effect on the lysine-free polypeptide (poly-N(5) hydroxyethyl-l-glutamine.

The enzymic conversion of squalene, 2(3),22(23)-diepoxide to α-onocerin by a cell-free extract of Ononis spinosa

2.3. Preparation of enzyme Seedlings of Ononis spinosa were grown by the University of Liverpool Botanic Gardens. Both roots and leaves of 2 month old seedlings were used as a source of enzyme. About 10 g of tissue were ground with a pestle and mortar under liquid nitrogen. The frozen powder was stirred into 0.1 M potassium phosphate pH 7.2 (30 ml), containing 2% (w/v) soluble polyvinyl pyrollidone, 0.05% (w/v) cysteine, ascorbate (0.05 M) and sucrose (0.2 M). The homogenate was strained throu.& gauze and the filtrate centrifuged at 20,000 g for 20 min. The pellet was discarded. All manipulations were carried out at o-4O.