A phosphonate-induced gene which promotes Penicillium-mediated bioconversion of cis-propenylphosphonic acid to fosfomycin. (1/27)

Penicillium decumbens is able to epoxidize cis-propenylphosphonic acid (cPA) to produce the antibiotic fosfomycin [FOM; also referred to as phosphonomycin and (-)-cis-1,2-epoxypropylphosphonic acid], a bioconversion of considerable commercial significance. We sought to improve the efficiency of the process by overexpression of the genes involved. A conventional approach of isolating the presumed epoxidase and its corresponding gene was not possible since cPA epoxidation could not be achieved with protein extracts. As an alternative approach, proteins induced by cPA were detected by two-dimensional gel electrophoresis. The observation that a 31-kDa protein (EpoA) was both cPA induced and overaccumulated in a strain which more efficiently converted cPA suggested that it might take part in the bioconversion. EpoA was purified, its amino acid sequence was partially determined, and the corresponding gene was isolated from cosmid and cDNA libraries with oligonucleotide probes. The DNA sequence for this gene (epoA) contained two introns and an open reading frame encoding a peptide of 277 amino acids having some similarity to oxygenases. When the gene was subcloned into P. decumbens, a fourfold increase in epoxidation activity was achieved. epoA-disruption mutants which were obtained by homologous recombination could not convert cPA to FOM. To investigate the regulation of the epoA promoter, the bialaphos resistance gene (bar, encoding phosphinothricin acetyltransferase) was used to replace the epoA-coding region. In P. decumbens, expression of the bar reporter gene was induced by cPA, FOM, and phosphorous acid but not by phosphoric acid.  (+info)

Certification of standard reference material 970, ascorbic acid in serum, and analysis of associated interlaboratory bias in the measurement process. (2/27)

BACKGROUND: The accurate and reproducible measurement of ascorbic acid is essential in delineating the role of ascorbic acid as a diagnostic tool for human disease and for the comparison of data acquired by different laboratories. A stabilized pair of standards of ascorbic acid in human serum, which is compatible with most analytical methods, have been prepared. METHODS: The certification was based on the gravimetric addition of ascorbic acid to metaphosphoric acid-stabilized, ascorbic acid-depleted serum and NIST liquid chromatography-electrochemical measurements. The NIST results were analyzed statistically for homogeneity, and the expanded uncertainty of each SRM was calculated using all of the NIST data. An interlaboratory comparison exercise was also performed. RESULTS: These materials, Standard Reference Material (SRM) 970 Ascorbic Acid in Serum, Level I and Level II, are homogeneous and are certified to contain (10.07 +/- 0.21) and (30.57 +/- 0.28) mmol ascorbic acid/L of solution (expanded uncertainty), respectively. In the interlaboratory comparison (n = 17), the relative SDs for the two materials were 22% and 19%. CONCLUSIONS: Two lots of serum, each containing different amounts of ascorbic acid stabilized in metaphosphoric acid, have been prepared and characterized. Many laboratories provide inaccurate results.  (+info)

Pharmacokinetics of a tumor necrosis factor-alpha phosphorothioate 2'-O-(2-methoxyethyl) modified antisense oligonucleotide: comparison across species. (3/27)

The pharmacokinetics of a 2'-O-(2-methoxyethyl)-ribose modified phosphorothioate oligonucleotide, ISIS 104838 (human tumor necrosis factor-alpha antisense), have been characterized in mouse, rat, dog, monkey, and human. Plasma pharmacokinetics after i.v. administration exhibited relatively rapid distribution from plasma to tissues with a distribution half-life estimated from approximately 15 to 45 min in all species. Absorption after s.c. injection was high (80-100%), and absorption after intrajejunal administration in proprietary formulations was as high as 10% bioavailability compared with i.v. administration. Urinary excretion of the parent drug was low, with less than 1% of the administered dose excreted in urine after i.v. infusion in monkeys at clinically relevant doses (< or = 5 mg/kg). ISIS 104838 is highly bound to plasma proteins, likely preventing renal filtration. However, shortened oligonucleotide metabolites of ISIS 104838 lose their affinity to bind plasma proteins. Thus, excretion of radiolabel (mostly as metabolites) in urine (75%) and feces (5-10%) was nearly complete by 90 days. Elimination of ISIS 104838 from tissue was slow (multiple days) for all species, depending on the tissue or organ. The highest concentrations of ISIS 104838 in tissues were seen in kidney, liver, lymph nodes, bone marrow, and spleen. In general, concentrations of ISIS 104838 were higher in monkey tissues than in rodents at body weight-equivalent doses. Plasma pharmacokinetics scale well across species as a function of body weight alone. This favorable pharmacokinetic profile for ISIS 104838 provides guidance for clinical development and appears to support infrequent and convenient dose administration.  (+info)

Determination of dehydroascorbic acid in mouse tissues and plasma by using tris(2-carboxyethyl)phosphine hydrochloride as reductant in metaphosphoric acid/ethylenediaminetetraacetic acid solution. (4/27)

Ascorbic acid (AA) has a strong anti-oxidant function evident as its ability to scavenge superoxide radicals in vitro. Moreover, AA is an essential ingredient for post-translational proline hydroxylation of collagen molecules. Dehydroascorbic acid (DHA), the oxidized form of AA, is generated from these reactions. In this study, we describe an improved method for assessing DHA in biological samples. The use of 35 mM tris(2-carboxyethyl)phosphine hydrochloride (TCEP) as a reductant completely reduced DHA to AA after 2 h on ice in a 5% solution of metaphosphoric acid containing 1 mM ethylenediaminetetraacetic acid (EDTA) at pH 1.5. This method enabled us to measure the DHA content in multiple tissues and plasma of 6-weeks-old mice. The percentages of DHA per total AA differed markedly among these tissues, i.e., from 0.8 to 19.5%. The lung, heart, spleen and plasma had the highest levels at more than 10% of DHA per total AA content, whereas the cerebrum, cerebellum, liver, kidney and small intestine had less than 5% of DHA per total AA content. This difference in DHA content may indicate an important disparity of oxidative stress levels among physiologic sites. Therefore, this improved method provides a useful standard for all DHA determinations.  (+info)

Ascorbic and dehydroascorbic acids measured in plasma preserved with dithiothreitol or metaphosphoric acid. (5/27)

We describe a rapid method for accurately and precisely measuring ascorbic acid and dehydroascorbic acid in plasma. Total analysis time is less than 10 min, replicate analyses of a single pool provide precision less than or equal to 2%, and values measured in supplemented samples agree with known concentrations of 4.68 and 11.83 mg/L. The stability and homogeneity of lyophilized plasma samples supplemented with ascorbic acid and dithiothreitol are documented. We also describe a procedure in which metaphosphoric acid (50 g/L) is used to prepare a reference material for the measurement of ascorbic acid and dehydroascorbic acid. The procedure for both acids consists of first measuring the native ascorbic acid, then reducing the dehydroascorbic acid, at neutral pH, with dithiothreitol, and finally measuring the total ascorbic acid; dehydroascorbic acid is then determined by difference. The metaphosphoric-acid-treated samples were stable at -70 degrees C, but stability decreased with temperature over the range examined, 4-50 degrees C.  (+info)

A review of the developments of multi-purpose primers and adhesives comprising novel dithiooctanoate monomers and phosphonic acid monomers. (6/27)

This paper reviews the developments of dithiooctanoate monomers and acidic adhesive monomers, and their roles in multi-purpose primers and adhesives in promoting adhesion to multiple substrate materials. Novel dithiooctanoate monomers exhibited excellent bonding to precious metals and alloys when compared against conventional sulfur-containing monomers. Newly developed phosphonic acid monomers, endowed with a water-soluble nature, enabled sufficient demineralization of dental hard tissues and thus improved bonding to both ground enamel and dentin. The optimal combination for bonding to dental hard tissues and precious and non-precious metals and alloys was 5.0 wt% 10-methacryloyloxydecyl 6,8-dithiooctanoate (10-MDDT) and 1.0 wt% 6-methacryloyloxyhexyl phosphonoacetate (6-MHPA). For bonding to dental porcelain, alumina, zirconia, and gold (Au) alloy, a ternary combination of silane coupling agent, acidic adhesive monomers, and dithiooctanoate monomers seemed promising. The latest development was a single-bottle, multi-purpose, self-etching adhesive which contained only acidic adhesive monomers and dithiooctanoate monomers but which produced strong adhesion to ground enamel and dentin, sandblasted zirconia, and Au alloy.  (+info)

The mechanisms of inhibition of frog endplate currents with homologous derivatives of the 1,1-dimethyl-3-oxybutyl phosphonic acid. (7/27)

The mode of inhibition of endplate currents by four esters of 1,1-dimethyl-3-oxybutyl phosphonic acid with different lipophilicities and molecule lengths were estimated by mathematical modeling based on previous electrophysiological data supplemented by several experiments with rhythmic stimulation. The aim was to discriminate between their receptor and non-receptor effects. It was shown that all esters have a two-component mechanism of depression: inhibition of the receptor open channel and allosteric modulation of the receptor-channel complex. The ratio of both functional components depends on the length and lipophilicity of the esters. Short and less lipophilic esters mostly act as open channel inhibitors and the rate of inhibition substantially depends on the rate of stimulation, i. e. probability of the receptor-channel opening. As the length of the ester radicals and their lipophilicity increased, these compounds were more active as allosteric receptor inhibitors, probably hindering the function of nAChRs from the lipid annulus.  (+info)

Hepatitis B surface antigen declines and clearance during long-term tenofovir therapy in patients coinfected with HBV and HIV. (8/27)