Acid-soluble Material Research Articles

Effective purification of graphite via low pulp density flotation-low temperature alkali roasting-acid leaching route: From laboratory-scale to pilot-scale

A typical flake graphite concentrate sampled from a graphite flotation plant was used to prepare high purity graphite. The carbon content of the concentrate was 85.6%, and silicate and iron-containing minerals were found principally in the concentrate. High-grade graphite concentrate with a carbon content of 95% was obtained in the flotation process with feed pulp of 5% solids by weight after regrinding by a low-speed ball milling system. A small amount of the flotation reagents such as caustic soda, water glass, kerosene, and pine oil were added. The resulting flotation concentrate was mixed with alkali and roasted at 500 °C for 90 min. During the alkali roasting, the silicate mineral was converted into the water- and acid-soluble materials. Afterward, the soluble materials and iron-containing minerals were dissolved by acid leaching. As a result, a product with a carbon content of 99.82% was prepared. According to the calculation results of Gibbs energy, the reactions between impurities and chemicals in alkali roasting and acid leaching processes were spontaneous. The purification route was very effective for high purity graphite production and has been successfully applied in the pilot-scale experiment.

Colmatating of productive gas formations while drilling wells with abnormally lower hydrostatic pressures

Today the pressures in productive gas collectors on the Dnieper-Donets rift are considerably lower than hydrostatic ones. Opening such formations while drilling is a challenging task in terms of preventing losses and differential pressures. In order to solve the problem, one needs to improve the methods of effective temporary colmation of productive formations with acid-soluble materials under the conditions of abnormally low formation pressures during drilling on fields with late terms of development. Traditional algorithms of lost circulation control in abnormally low reservoir pressure, developed by leading world services companies, often turn out to be unworkable. In order to conduct the lost circulation control, one often chooses colmatants, which totally align with the principles of ideal packaging, however do not meet the criterion of strength or resistance to significant differential pressure. As a result, in the course of the subsequent drilling there can be another circulation loss in already colmated layer. In Ukraine the lost circulation control sphere is being developed by means of selecting colmatants according to a new principle. The article has proposed the activities for the lost circulation curing and pollution reducing of productive collectors. For this purpose the generalized characteristic-criterion of colmatants has been developed and used. The criterion got a name “flexibility”, i.e. a deformation, compaction and penetration (into porous-fissured medium) capability under immense pressure. With the help of the criterion the set of particular colmatant have been chosen; also, principles of colmatant mixtures selection under the relevant geological and mining conditions have been identified. In many cases, there is no need to calculate the physical parameters of the formation and the circulation loss crack due to flexibility of colmatant; one only has to select the optimal concentrations of materials and the periodicity of input these materials to the mud. The developed technology confirms the need to improve the algorithms for circulation loss prevention and curing, primarily for conditions of abnormally low reservoir pressures.

Oxidative Copolymerization of <i>o-</i>Hydroxy-<i>m</i>-Phenylenediamine and <i>O</i>- Toluidine - Synthesis, Structure and Properties of Copolymers

Oxidative copolymerization of o-hydroxybenzylidene-m-phenylenediamine and o-toluidine in a solution of sulfuric acid synthesized new copolymers of different composition. Structures of the copolymers obtained were confirmed by IR spectroscopy. It is shown that the copolymers obtained are not fusible materials and acid-soluble materials. The synthesized copolymers have been found to possess sufficient thermostability. The process of decomposition of the copolymers occurs in several stages, the temperature ranges depending on their composition.

Impacts of carbonization temperature on the Pb(II) adsorption by wheat straw-derived biochar and related mechanism.

To determine the quantitative correlations between physicochemical characteristics and Pb(II) adsorption amounts of biochar fractions, we prepared wheat straw-derived biochar under various carbonization temperatures (300-900 °C). The different fractions of the wheat straw-derived biochar, water-soluble material (WM), acid-soluble material (AM), and organic material (OM), were acquired. The ash content, ultimate analysis, pH, ion strength (IS), cation exchange capacity (CEC), and acidic functional groups (AFG) were characterized. The Pb(II) adsorption amounts of different biochars and their fractions were determined. The results revealed that the proportions of biochar fractions (WM, AM, and OM) varied with various carbonization temperatures. The maximum Pb(II) adsorption amount of wheat straw-derived biochar (qTotal) was 157.95 ± 0.13 mg/g obtained at 800 °C, and the quantitative correlations between Pb(II) adsorption amount (q) and carbonization temperature (T) can be elaborated by qTotal = 170.72-336.62exp(-0.0035T) (R2 = 0.97), qWM = 106.18-390.10exp(-0.0046T) (R2 = 0.98), qAM = 496.16-477.74exp(-0.0001T) (R2 = 0.79), and qOM = 1.80 + 34.69exp(-0.0038T) (R2 = 0.85). For rate of contribution (RC) for Pb(II) adsorption, when T < 400 °C, the order was AM (60.72 ± 7.33%) > OM (23.41 ± 7.33%) > WM (15.87 ± 0.30%); however, when T ≥ 400 °C, the order was WM (52.31 ± 0.85% - 67.65 ± 2.99%) > AM (29.65 ± 0.46% - 35.77 ± 0.12%) > OM (2.30 ± 0.47% - 12.02 ± 2.43%). Moreover, qWM and qAM exhibited significant positive linear correlations with ash (qWM = 9.92Ash - 123.65, and qAM = 2.13Ash - 0.49), qTotal was predominantly affected by ash content (qTotal = 10.97 Ash - 95.49). The EDX, XRD, and FTIR analysis results further clarified that ion exchange and precipitation were the main adsorption mechanisms for Pb(II) adsorption by wheat straw-derived biochar.

Rheological properties and damage-control mechanism of oil-based drilling fluid with different types of weighting agents.

The great amount of solid particles contained in a weighting agent is a major cause of the problems in both rheology properties and damage control mechanism of an oil-based drilling fluid (OBM). Therefore, a proper type of weighting agent can be a solution for the application of OBM. In this study, three weighting agents that have been commonly used with OBM, namely, standard barite, submicron barite and superfine manganese ore, are studied. Rheological properties of OBM and the degree of formation damage are assessed with regard to the three weighting agents. The agents are also studied in aspects of particle size, micromorphology, filtration loss and wall-building property, acid dissolution efficiency of mud cake, lubricity and sedimentation stability to analyse the effects of the agents on rheological properties and the degree of damage as well as to figure out the mechanism of rheology control and damage control. For the OBM, there is a mutual effect between rheological stability and the degree of damage. In consideration of the agents' properties, we can enhance the rheological stability of the OBM and control the degree of formation damage by properly selecting particle size, using acid-soluble materials and forming the mud cake with ultra-low permeability that can easily be cleared away.

Novel Coiled-Tubing Perforation Technique and Stimulation in Carbonate Gas Well

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper IPTC 18880, “Novel Abrasive Perforating With Acid-Soluble Material and Subsequent Coiled-Tubing Jetting-Assisted Stimulation Provide Outstanding Results in Carbonate Gas Well,” by Adrian Buenrostro, Nahr Abulhamayel, Usman Malik, Mohammad Bu Suwaileh, and Saad Driweesh, Saudi Aramco, and Alejandro Chacon, José Camilo Jimenez Fadul, and José Noguera, Halliburton, prepared for the 2016 International Petroleum Technology Conference, Bangkok, Thailand, 14–16 November. The paper has not been peer reviewed. Copyright 2016 International Petroleum Technology Conference. Reproduced by permission. Abrasive perforating with coiled tubing (CT) is a technique that has proved to be a valuable alternative to conventional perforating with electric line. The application is particularly valuable whenever a high rate or fracture-stimulation treatment is to follow because of the significant reduction in tortuosity and pumping friction losses across perforations. This paper discusses a novel approach to abrasive perforating, including the first-ever use of an acid-soluble abrasive material and ending with CT-jetting-assisted nitrified stimulation. Introduction Many carbonate gas wells located in the northern section of the Ghawar reservoir exhibit a low-permeability profile and are characterized by having low reservoir pressure. Fracture gradients in a formation in this area of the field are on the order of 1.12 psi/ft, which is considerably greater than that of more-conventional tight gas formations. One particular well, located on the flank of the reservoir, was designed to be completed with a plug-and-perforate acid-fracturing operation, but issues arose with this option that finally caused the abandonment of the fracturing treatment. To find a solution that would be feasible and economically viable, an innovative perforation and stimulation technique was engineered for this well. Design of the Perforation Technique and Yard Testing The team was able to source a newly developed acid-soluble abrasive material that enabled the same quality of perforations to be created without performing a cleanout run because the acid from the stimulation would dissolve the abrasive material, saving at least 2 days of operation. The abrasive material was sourced, and several yard tests were completed to determine if the material had the same abrasive characteristics as common 20/40- or 100-mesh sand. It was necessary to compare the time required to penetrate the steel and cement with the results obtained using common sand. This benchmarking was key to determining if additional time and fluid resources were necessary to obtain the same penetration. A yard test was set up with two metallic 55-gal drums cut halfway lengthwise and then welded together. This created a receptacle that allowed the team to place a 6⅝-in. casing section with 100% standoff and then fill the entire annular space with cement. The drum was then set on top of cement blocks, and the abrasive-jetting tool was introduced.

Technology Focus: Coiled Tubing Applications (June 2016)

Technology Focus Another tough year has passed since the last coiled-tubing feature in JPT. In spite of the difficult economic climate, the SPE/ ICoTA Coiled Tubing and Well Intervention Conference and Exhibition moved to a new venue this year, the George R. Brown Convention Center in Houston, because of the continued growth of the exhibition in prior years. Attendance was down by only a small percentage, which, I hope, is an encouraging sign. As mentioned in last year’s feature, the coiled-tubing industry is adapting to the changing environment. Several papers at this year’s conference discussed various aspects of subsea work performed with coiled tubing. Two papers presented different methods to use coiled tubing to enter or drill wellbores by using either an injector or a snubbing jack at the seabed and a secondary coiled-tubing injector at the surface. In both methods, the coiled tubing runs freely through the water— that is, the coiled tubing is not contained within a secondary riser pipe—and, hence, many in the industry are referring to this new technique as riserless coiled tubing. Other subsea operations mentioned included the use of coiled tubing as a downline for pumping fluids from a vessel to a subsea tree or pipeline. While this is not new to the coiled-tubing industry, tooling and vessel-based-equipment improvements have been developed to make operations safer and more versatile. Also in this arena, new thermoplastic composite materials are being introduced to the market and may bring further enhancements. These types of developments require considerable investment on behalf of the companies involved and tend to signal confidence in the longer-term return. Meanwhile, investment in furthering the understanding of the performance of steel materials for coiled-tubing well-intervention operations continues to grow. This performance envelope is being examined in terms of both the mechanical (e.g., abrasion and fatigue) and the environmental (e.g., sour-well environments). For example, renewed studies are being conducted on the combination of high-cycle elastic and low-cycle plastic fatigue, which currently has relevance to subsea work. Formerly, such studies were limited to the use of coiled tubing as a pump string. Additionally, established knowledge of solids transport in high-angle wells, from both field experience and laboratory work, is being applied more widely to reduce costs through increased efficiency. This has been a long implementation curve for the coiled-tubing industry. The next 12 months could bring upturns and downturns and greater or lesser volatility. Whatever may happen, the coiled-tubing industry’s record last year indicates that it will still be moving forward. Recommended additional reading at OnePetro: www.onepetro.org. SPE 179096 Localized Extreme Coiled-Tubing Wall Loss—Causes and Remediation Practices by Steven Craig, Baker Hughes, et al. SPE 179083 Novel Abrasive Perforating With Acid-Soluble Material and Subsequent Hydrajet-Assisted Stimulation Provide Outstanding Results in Carbonate Gas Well by Alejandro Chacon, Halliburton, et al. SPE 168294 Coiled-Tubing-Material Selection for Velocity Strings in Sour Brine Service by I. Ward, Shell Canada, et al.

Bilberry and bilberry press cake as sources of dietary fibre

BackgroundDietary recommendations for Nordic countries urge the use of plant foods as a basis for healthy nutrition. Currently, the level of dietary fibre (DF) intake is not adequate. Berries are an elementary part of the recommended Nordic healthy diet and could be consumed in higher amounts.Materials and methodsFinnish bilberries and a bilberry press cake from juice processing were studied for DF content, carbohydrate composition, and non-carbohydrate fibre content, which was analysed as sulphuric acid insoluble and soluble material. The microstructure of all samples was also studied using light microscopy and toluidine blue O, calcofluor, and acid fuchsin staining.ResultsThe total DF contents of fresh and freeze-dried bilberries and the press cake were 3.0, 24.1, and 58.9%, respectively. Most of the DF was insoluble. Only about half of it was carbohydrate, the rest being mostly sulphuric acid–insoluble material, waxy cutin from skins, and resilient seeds. Bilberry seeds represented over half of the press cake fraction, and in addition to skin, they were the major DF sources. Microscopy revealed that skins in the press cake were intact and the surface of the seeds had thick-walled cells.ConclusionsBilberry press cake is thus a good source of insoluble non-carbohydrate DF, and could be used to provide DF-rich foods to contribute to versatile intake of DF.

Antibacterial action of acetic acid soluble material isolated from Mucor rouxii and its application onto textile

Acetic acid soluble material (AcSM) is a chitosan-rich fraction isolated from the fungal cell wall materials. The final step in the traditional production of fungal chitosan is the separation of chitosan from the cell wall AcSM via raising the pH to 9–10 followed by centrifugation. This step results in further undesirable economic and environmental effects. The goal of this paper is to avoid that by investigating the antimicrobial effect of the whole AcSM from Mucor rouxii DSM-1191 cell wall and its application on cotton fabrics. The treated fabrics were characterized through monitoring the textile physical properties and for the antibacterial activity against Escherichia coli and Micrococcus luteus. Results showed that Mucor rouxii DSM-1191 has excellent potentials to be used for cell wall AcSM production on industrial scale with a maximum content of 40% in dry mycelia. The obtained results indicated that the physical properties of the treated fabrics, as well as the antibacterial activity, were improved after treatment with fungal AcSM.

Influence of torrefaction on some chemical and energy properties of maritime pine and pedunculate oak

This study investigated the influence of heat treatment on the chemical composition and energy properties of maritime pine (Pinus pinaster) and pedunculate oak (Quercus robur). Samples were treated in a new experimental device at 220, 250, or 280 °C for 1 or 5 hours. Chemical and energy analyses were performed using standard methods. Our results clearly demonstrated an increased degradation of the material due to the combined effects of temperature and treatment duration. This mass loss was basically due to degradation of acid-soluble materials. The energy analysis showed that the fixed carbon content and higher heating value increased, for both species, whereas the volatile matter content decreased with increased extent of treatment (cumulated effects of temperature and time). In the range of temperature and duration studied here, the dimensionless energy properties for both species obeyed the same functions of overall mass loss. The relationships obtained allow quantification of the increase in wood energy concentration due to torrefaction. Mass loss is an excellent indicator of treatment extent. Analytical expressions allowing the prediction of energy and chemical properties as a function of overall mass loss, within the range of treatment extents studied here, are provided.

High-precision Mg isotopic systematics of bulk chondrites

Variations of the mass-independent abundance of 26Mg ( δ 26Mg*) and stable Mg ( δ 25Mg) isotope composition of chondrites are important because they constrain the homogeneity of 26Al and Mg isotopes in the proto-planetary disc and the validity of the short-lived 26Al-to- 26Mg chronometer applied to meteorites. We present high-precision Mg isotope data and Al/Mg ratios of chondrites representing nearly all major chondrite classes, including a step-leaching experiment on the CM2 chondrite Murchison. δ 26Mg* variations in leachates of Murchison representing acid soluble material are ≤ 30 times smaller than reported for neutron-rich isotopes of Ti and Cr and do not reveal resolvable deficits in δ 26Mg* (−0.002 to + 0.118‰). Very small variations in δ 26Mg* anomalies in bulk chondrites (−0.006 to + 0.019‰) correlate with increasing 27Al/ 24Mg ratios and δ 50Ti, reflecting the variable presence of calcium–aluminium-rich inclusions (CAIs) in some types of carbonaceous chondrites. Similarly, release of radiogenic 26Mg produced by 26Al decay from CAI material in the step-leaching of Murchison best explains the high δ 26Mg* observed in the last, aggressive, leaching steps of this experiment. Overall, the observed variations in δ 26Mg* are small and potential differences beyond that which result from the presence of CAI-like material cannot be detected within the analytical uncertainties of this study (± 0.004‰). The results do not allow radical heterogeneity of 26Al (≥±30%) or measurable Mg nucleosynthetic heterogeneity (≥±0.005‰) to have existed on a planetesimal scale in the proto-planetary disc. Combined with published δ 26Mg* data for CAIs, the bulk chondrite data yield a precise initial ( 26Al/ 27Al) 0 = (5.21 ± 0.06) × 10 − 5 and δ 26Mg* = −0.0340 ± 0.0016‰ for the Solar System. However, it is not possible with the currently available data to determine with certainty whether CAIs and the material from which planetesimals accreted including chondrite parent bodies had precisely the same initial levels of 26Al, although planetesimals and planets appear to have accreted from material with a mean initial ( 26Al/ 27Al) 0 in the range of 2.1 to 6.7 × 10 − 5 . The average stable Mg isotope composition of all analysed chondrites, with the exception of a chondrule from the CBa chondrite Gujba ( δ 25Mg DSM - 3 = −0.032 ± 0.035‰), is δ 25Mg DSM - 3 = −0.152 ± 0.079‰ (2 sd) and is indistinguishable from that of the Earth's mantle.

Sources of molecularly uncharacterized organic carbon in sinking particles from three ocean basins: A coupled Δ 14C and δ 13C approach

Abstract Several recent studies have suggested dramatically different ideas about the source and nature of molecularly uncharacterized organic carbon (MUC) in sinking marine particles (POC). Carbon isotope data coupled with hydrolysis has indicated MUC is lipid-like material, suggesting selective preservation [Hwang, J. and Druffel, E.R.M., 2003. Lipid-like material as the source of the uncharacterized organic carbon in the ocean? Science, 299: 881–884.]. In contrast, NMR-based work has strongly indicated non-selective degradation, with amino acid dominating resistant material [Hedges, J.I. et al., 2001. Evidence for non-selective preservation of organic matter in sinking marine particles. Nature, 409: 801–804.]. This study set out to explore this seeming paradox, and to examine the hypothesis that the nature of MUC may vary strongly between margin and open ocean regions. We examined the coupled elemental, stable and radiocarbon isotopic compositions of three fractions of sinking POC: lipids, acid soluble (AS) material (a proxy for hydrolyzable biomolecules), and acid insoluble (AI) material (a proxy for the MUC). Δ 14C and δ 13C measurements were made on three time-series of sediment trap samples in widely separate ocean regions: Santa Barbara Basin, Cariaco Basin, and an oceanic site in the Eastern Subtropical Atlantic off Dakar, Africa. Δ 14C compositions of AI fractions at all sites indicated substantial contribution by pre-aged marine carbon sources (40–60% of total sinking POC), not derived from direct export of surface productivity. Comparison of δ 13C and Δ 14C values with coexisting lipid and AS signatures also suggested widely different AI compositions from different ocean environments. AI material in coastal California waters consistently appeared lipid-like, in agreement with several studies near the same region [Hwang, J. and Druffel, E.R.M., 2003. Lipid-like material as the source of the uncharacterized organic carbon in the ocean? Science, 299: 881–884.; Hwang, J., Druffel, E.R.M., Eglinton, T.I. and Repeta, D.J., 2006b. Source(s) and cycling of the nonhydrolyzable organic fraction of oceanic particles. Geochimica et Cosmochimica Acta, 70: 5162–5168.]. In contrast, our oceanic site's AI isotopic signatures were more consistent with non-selective preservation of a range of biochemical classes. AI compositions in Cariaco Basin proved to be variable with time, suggesting a complex and variable mixture of AI sources. These results suggest a major divergence between coastal and oceanic AI sources and composition. Taken together, we propose that the dominant mechanism influencing molecularly uncharacterized material is non-selective preservation during initial water column transit; influenced to varying degrees by subsequent addition of allochthonous and 14C-depleted organic carbon sources. In our coastal margin sites, all AI properties point to resuspended sediment as the most likely source of total uncharacterizable POC. In our more oceanic site, where particles have much longer transit times, incorporation of old DOC into POC, in addition to resuspended sediment, may have a substantial influence on overall Δ 14C ages. We propose that major differences between AI compositions in different locations is tied to variation in availability of such pre-aged OC sources, linked to regional oceanographic conditions and strongly influenced by proximity to continental shelves. The strong correlations we observe between %AI vs. %AS composition and elemental and isotopic values also implies that substantial amounts of POC collected via sediment traps in some locations is not exported directly from surface production, but added from other pre-aged reservoirs.

Bone Morphogenetic Protein-4, a Novel Modulator of Melanogenesis

Bone morphogenetic proteins (BMPs), members of the transforming growth factor-beta family, signal in many cells including neural precursors. Two receptors, types 1 and 2, coordinately mediate BMP signaling, and type 1 receptor has two forms: A and B. Using RT-PCR we found that neural crest-derived human melanocytes express BMP receptor-1A, -1B, and -2. Furthermore, melanocytes and the surrounding keratinocytes express BMP-4, suggesting both autocrine and paracrine effects of this molecule. Moreover, BMP-4 supplementation of cultured human melanocytes decreases melanin synthesis, tyrosinase mRNA, and protein. The mechanism of this BMP-4 effect on tyrosinase and ultimately on melanogenesis involves modest decreases of tyrosinase transcription rate and mRNA stability. Moreover, ultraviolet irradiation, the best recognized environmental stimulator of melanogenesis, down-regulated the mRNA of BMP receptor-1B in melanocytes. Our data provide evidence of a novel regulatory pathway for melanogenesis in human skin.

Sr-Nd isotope geochemistry of eolian dust of the arid-semiarid areas in China: Implications for loess provenance and monsoon evolution

Minerals and rocks have distinct 87Sr/86Sr and 143Nd/144Nd ratios, depending on their geological origin and ages, and these isotope ratios are less altered than elemental composition during transport in the atmosphere or after deposition as sediments, thus stable isotopes of Sr and Nd have great potential as tracers for provenance and transport of materials. During the hypergene process, Sr isotope ratios of sediments are controlled by their parent rocks, particle sizes and chemical weathering. In general, the higher the Sr isotope ratios of parent rocks, and/or the more the fine-grained fractions, and/or the stronger the chemical weathering, thus the higher the Sr isotope ratios of sediments. On the contrary, there are lower Sr isotope ratios of sediments. Nd isotope ratios of sediments, independent of their particle sizes and chemical weathering, are only associated with parent rocks. For the provenance of the Chinese Loess Plateau, different reseachers drew discordant and even contradictory conclusions by using the method of Sr-Nd isotopic tracing. From the previous Nd isotope data, it is considered that the Tarim Basin, deserts in the central and west parts of Inner Mongolia and the Tibetan Plateau are the main sources of the Chinese Loess Plateau, and are also manufacturers for eolian dust of the Far East regions, together with the Chinese Loess Plateau. Sr isotope ratios of eolian dust are solely affected by wind sorting and weathering-pedogenesis due to its homogeneous composition in the Chinese Loess Plateau. Wind sorting is related to the East Asian winter monsoon but weathering-pedogenesis is mainly associated with the East Asian summer monsoon. Studies on Sr isotopic compositions of the loess-paleosol sequence suggest that 87Sr/86Sr ratios in acid-soluble materials are an index for chemical weathering intensity of the Chinese Loess Plateau, indicating the East Asian summer monsoon variations, whereas 87Sr/86Sr ratios in acid-insoluble materials are significantly controlled by particle sizes, and can be used as a proxy indicator reflecting the East Asian winter monsoon variations. Variations of 87Sr/86Sr ratios in acid-insoluble materials in the past 2.6Ma further demonstrate that the East Asian winter monsoon gradually strengthened since the beginning of the Quaternary period. This result agrees with the prior conclusion that climate gradually cooled since the onset of the Quaternary Ice Age.

Studies on T4-Head Maturation

The substrate specificity of 49+-enzyme was investigated in vitro. The enzyme showed a marked preference for rapidly sedimenting T4 DNA (greater than 1000 S) when helix-destabilizing proteins from Escherichia coli or phage T4 were added to the reaction. Regular replicative T4 DNA (200-S DNA) or denatured T4 DNA was not cleaved by the enzyme in the presence of these proteins but if they were omitted from the reaction both DNAs become good substrates for the enzyme. 200-S DNA was cleaved at its natural sites of single strandedness which occur at one-genome intervals. Gaps in T4 DNA which were constructed by treatment of a nicked DNA with exonuclease III were also cleaved by 49+-enzyme in the absence of helix-destabilizing proteins. Single-stranded T4 DNA was extensively degraded and up to 50% of the material was found to be acid-soluble in a limit digest. The degradation products were predominantly oligonucleotides of random size. No preference for a 5'-terminal nucleotide was observed in material from a limit digest with M13 DNA. Double-stranded DNA was nicked upon exposure to 49+-enzyme and double-strand breakage finally occurred by an accumulation of single-strand interruptions. No acid-soluble material was produced from native T4 DNA. The introduction of nicks in native DNA did not improve its properties as a substrate for the enzyme. Double-stranded DNA was about 100-fold less sensitive to the enzyme than single-stranded DNA.

Studies on lactulose formulations for colon-specific drug delivery

A novel, colon-targeted delivery system (CODES™), which uses lactulose, was investigated in this study. Lactulose is not absorbed in the upper GI tract, but degraded to organic acids by enterobacteria in the lower gastrointestinal tract, especially the colon. A CODES™ consists of three components: a core containing lactulose and the drug, an inner acid-soluble material layer, and an outer layer of an enterosoluble material. When a CODES™ containing a pigment was introduced into the rat cecum directly after shaking in JP 2nd fluid for 3 h, pigment release was observed 1 h after introduction. A CODES™ containing 5-aminosalicylic acid (5-ASA) was orally administered to fasting and fed dogs to evaluate its pharmacokinetic profiles. 5-ASA was first detected in plasma after 3 h, which is the reported colon arrival time for indigestible solids, after dosing to fasting dogs. The T max in fed dogs was delayed by 9 h when compared to fasting dogs. This corresponds to the gastric emptying time. However, the C max and AUC under fed conditions were almost as same as those under fasting conditions. The results of this study show that lactulose can act as a trigger for drug release in the colon, utilizing the action of enterobacteria.

Influence of soil constituents on soil phosphorus sorption and desorption

A study was conducted to examine phosphorus (P) sorption and immediate desorption in 0.01 M CaCl2 in unmanured and manured grassland and arable soils after chemical treatment designed to remove organic matter [sodium hypochlorite (NaOCl)], aluminum (Al) and iron (Fe) oxides [dithionite-citrate], and acid soluble materials [hydrochloric acid (HCl)], either in combination or individually. Removal of Al and Fe oxides had the greatest effect in decreasing P sorption and increasing P desorption relative to the fraction of P previously sorbed. Sorption of P was approximately 2 to 5 times greater in soils extracted with HCl than in dithionite-citrate treated soils, while P desorption as a fraction of P sorbed was approximately one-seventh that in dithionite-citrate treated soils. The effect of HCl pretreatment was more pronounced in arable soils compared to grassland soils, which reflected the influence of Ca on P solubility. Following pretreatment with NaOCl, P sorption was similar in manured and unmanured arable soils. This was not the case in the corresponding grassland soils which was attributed to either physical occlusion of sorption sites by organic matter and/or differences in the chemical nature and stability of soil organic matter in the grassland compared to arable soils.

Non-enzymatic RNA hydrolysis promoted by the combined catalytic activity of buffers and magnesium ions.

Although Mg2+ is an important cofactor for the specific degradation of RNA by ribozymes, it is not considered as a typical chemical nuclease. In this study we show that in combination with common buffers such as tris(hydroxymethyl)aminomethane and sodium borate, Mg2+ is a powerful catalyst for the degradation of RNA. pH and temperature are found to be the principal factors for the efficient degradation of RNA. Whereas in Tris-HCl/Mg2+ the efficient cleavage starts at pH values higher than 7.5 and temperatures higher than 37 degrees C, in sodium borate RNA degradation begins at pH 7.0 and at 37 degrees C. RNA hydrolysis promoted under the combined catalytic activity of buffer/Mg2+ results in partially degraded RNA and negligible amounts of acid-soluble material. Reaction is insensitive to the concentration of monovalent cations but is completely prevented by chelating agents (EDTA and citrate) at concentrations exceeding that of Mg2+. Borate-magnesium reaction is inhibited also by some polyvalent alcohols (glycerol) and sugars.

Noninvasive procedure for in situ determination of skin surface aspartic proteinase activity in animals; implications for human skin.

The present study demonstrated a noninvasive procedure for in situ determination of stratum corneum aspartic proteinase in the living animal. A non-leaky well, containing [125I]S-carboxymethylated insulin B-chain (ICMI) as a substrate, was constructed on the shaved back of anesthetized guinea pigs and rats. The enzymatic activity was determined by measuring the radiolabeled trichloroacetic acid soluble material. We demonstrated pepstatin-sensitive proteinase activity bound to the skin surface indicating the involvement of aspartic proteinase(s) such as cathepsin D and/or E. Aged rats had about six fold lower activity than young animals. The proteinase activity was inhibited by the alkylating agent mechlorethamine and by the cosmetic propylene glycol. A similar procedure was carried out with intact human skin pieces obtained during plastic surgery. The activity was inhibited by antihuman cathepsin D antibodies. Cathepsin D was immunohistochemically localized in the corneal and granular layers of the epidermis. Skin surface aspartic proteinase/cathepsin D activity may serve as a marker for skin aging or for certain skin disorders leading to a new approach to their medical treatments.

Loss of GSH, Oxidative Stress, and Decrease of Intracellular pH as Sequential Steps in Viral Infection

Madin-Darby canine kidney cells infected with Sendai virus rapidly lose GSH without increase in the oxidized products. The reduced tripeptide was quantitatively recovered in the culture medium of the cells. Since the GSH loss in infected cells was not blocked by methionine, a known inhibitor of hepatocyte GSH transport, a nonspecific leakage through the plasma membrane is proposed. UV-irradiated Sendai virus gave the same results, confirming that the major loss of GSH was due to membrane perturbation upon virus fusion. Consequent to the loss of the tripeptide, an intracellular pH decrease occurred, which was due to a reversible impairment of the Na+/H+ antiporter, the main system responsible for maintaining unaltered pHi in those cells. At the end of the infection period, a rise in both pHi value and GSH content was observed, with a complete recovery in the activity of the antiporter. However, a secondary set up of oxidative stress was observed after 24 h from infection, which is the time necessary for virus budding from cells. In this case, the GSH decrease was partly due to preferential incorporation of the cysteine residue in the viral proteins and partly engaged in mixed disulfides with intracellular proteins. In conclusion, under our conditions of viral infection, oxidative stress is imposed by GSH depletion, occurring in two steps and following direct virus challenge of the cell membrane without the intervention of reactive oxygen species. These results provide a rationale for the reported, and often contradictory, mutual effects of GSH and viral infection.