Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: KEGG:D06522 (Silica)
2,396 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Silica-based ion-exchange Sep-Pak cartridges, packed with either carboxymethyl (CM) cation-exchanger or a quaternary methyl ammonium (QMA) anion exchanger, are now available. The feasibility of using ion-exchange Sep-Pak cartridges for the fractionation of pituitary peptides was investigated. Extracts of bovine posterior pituitaries were fractionated at either pH 5 or pH 7 by pairs of cation and anion exchangers, connected in series. The capacity to bind peptides was well correlated with the theoretical charge calculated for a variety of peptides. At pH 5 the entire tissue extract could be fractionated into either basic or acidic pools. In contrast, at pH 7 only the more basic or acidic peptides were retained by the respective ion exchangers. The rest of the peptides passed through both ion exchangers and were recovered in the neutral pool. The ion-exchange fractionation principle was used to facilitate the purification of 35S-labelled intermediate pituitary glycopeptides, prepared by incubating mouse intermediate lobes in explant culture with 35S-labelled sulphate. 35S-labelled glycosylated forms of Lys1 gamma 3MSH, corticotropin-like intermediate lobe peptide, and the amino terminal or 16K fragment of pro-opiomelanocortin (i.e. 16K1-74) were fractionated into separate pools such that they could be purified to homogeneity in a single step by reversed-phase high-performance liquid chromatography (RP-HPLC). Purification by conventional means would require at least two RP-HPLC steps. Thus, radiolabelled peptides can be purified with the minimum of chromatographic manipulation, thereby ensuring maximal recoveries.
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PMID:Use of ion-exchange Sep-Pak cartridges in the batch fractionation of pituitary peptides. 373 37

Adsorption of monomeric, dimeric, or trimeric quaternary ammonium surfactant on silica from its aqueous solution has been investigated by measuring adsorption density, zeta potential, and dispersion stability. The monomeric (dodecyltrimethylammonium bromide, 1RQ), dimeric (1,2-bis(dodecyldimethylammonio)ethane dibromide, 2RenQ), and trimeric (methyldodecylbis[2-dimethyldodecylammonio) ethyl] ammonium tribromide, 3RdienQ) surfactants are used in this study. The amounts adsorbed at saturation decrease with increasing dodecyl chain number of the surfactants from 1RQ to 2RenQ and 3RdienQ. Silica suspensions by adsorption of the surfactants exhibit a process of dispersion-flocculation-redispersion with the surfactant concentration for the three surfactants which can be correlated with the change in zeta potentials. ESR measurements using methyl 12-doxylstearate show that the microviscosities in 2RenQ- and 3RdienQ-adsorbed layers are greater than that in the 1RQ-adsorbed layer. Under a constant feed concentration of 2-naphthol, the adsolubilized amounts of 2-naphthol increase, reach a maximum, and then decrease with the surfactant concentration for the three surfactants. The ratio of maximum amount of 2-naphthol adsolubilized to the adsorbed amount of surfactant on silica increases with an increase in the dodecyl chain number of the surfactants from 1RQ to 2RenQ and 3RdienQ. In addition, from a two-step process of adsorption-adsolubilization, it is suggested that 2RenQ and 3RdienQ adsorb on much stronger than 1RQ, keeping 2-naphthol in their adsorbed layers.
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PMID:Adsorption and Adsolubilization by Monomeric, Dimeric, or Trimeric Quaternary Ammonium Surfactant at Silica/Water Interface 895 98

A rapid and specific high-performance liquid chromatography assay of lamotrigine in human plasma is described. Lamotrigine is extracted with dichloromethane from buffered plasma to which an internal standard has been added. The solvent is directly injected into a 250 x 4.6-mm Spherisorb Silica column and the drug is eluted by using a mixture of methanol, n-heptane, dichloromethane, and 28-30% ammonium hydroxide (20:40:40:0.3 vol/vol) at a flow rate of 1 ml/min. The eluates are detected at 240 nm. The assay requires 250 microliters of sample, and concentrations as low as 0.4 microgram/ml can be measured accurately. The method is linear in the range of 0.4-16 micrograms/ml, with a mean coefficient of correlation (r) > or = 0.997. Within- and between-day relative standard deviations at three different concentration levels (1, 4, and 8 micrograms/ml) are < or = 8.6%.
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PMID:A rapid and specific assay for the determination of lamotrigine in human plasma by normal-phase HPLC. 902 58

The preparation and evaluation of zirconium-adsorbing silica gel (Zr-Silica) as an ion-exchange stationary phase in ion chromatography for inorganic anions and cations was carried out. The Zr-Silica was prepared by the reaction of silanol groups on the surface of the silica gel with zirconium butoxide (Zr(OCH2CH2CH2CH3)4) in ethanol. The ion-exchange characteristics of the Zr-Silica were evaluated using 10 mM tartaric acid at pH 2.5 as eluent. The Zr-Silica was found to act as a cation-exchanger under the eluent conditions. The retention behavior of alkali and alkaline earth metal cations was then investigated. The Zr-Silica column was proved to be suitable for the simultaneous separation of alkali metal cations and ammonium ion. Excellent separation of the cations on a 15 cm Zr-Silica column was achieved in 25 min using 10 mM tartaric acid as eluent.
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PMID:Ion-chromatographic behavior of alkali metal cations and ammonium ion on zirconium-adsorbing silica gel. 1091 30

A high-performance thin-layer chromatographic (HPTLC) method was used to determine the glycoalkaloids alpha-solanine and alpha-chaconine in potatoes. Alpha-solanine and alpha-chaconine are extracted from dehydrated potatoes with boiling methanol-acetic acid (95 + 5, v/v). The analytes are separated on a Silica Gel 60 F254 HPTLC plate by a saturated mixture of dichloromethane-methanol-water-concentrated ammonium hydroxide (70 + 30 + 4 + 0.4, v/v), which is used for vertical development of the plate up to a distance of 85 mm. For visualization, the plate is dipped 3 times into a modified Carr-Price reagent, 20% (w/v) antimony(III) chloride in acetic acid-dichloromethane (1 + 3, v/v), and subsequently heated on a hot plate at 105 degrees C for 5 min. The glycoalkaloids all appear as red chromatographic zones on a colorless background. Densitometric quantification is performed at 507 nm by reflectance scanning. After determination of the appropriate response function, the proposed method was validated. Good results with respect to linearity, accuracy, and precision were obtained in the concentration range studied.
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PMID:Determination of alpha-solanine and alpha-chaconine in potatoes by high-performance thin-layer chromatography/densitometry. 1112 55

The application of unmodified silica gel (Super Micro Bead Silica Gel B-5, SMBSG B-5) as a cation-exchange stationary phase in ion chromatography with indirect photometric detection (IC-IPD) for the separation of common mono- and divalent cations (Li+, Na+, NH4+, K+, Mg2+ and Ca2+) was carried out using various aromatic monoamines [tyramine [4-(2-aminoethyl)phenol], benzylamine, phenylethylamine, 2-methylpyridine and 2,6-dimethylpyridine] as eluents. When using these amines as eluents, the peak resolution between these mono- and divalent cations was not quite satisfactory and the peak shapes of NH4+ and K+ were largely destroyed on the SMBSG B-5 silica gel column. Hence, the application of SMBSG B-5 silica gel calcinated at 200, 400, 600, 800 and 1000 degrees C for 5 h in the IC-IPD was carried out. The peak shapes of the monovalent cations were greatly improved with increasing calcination temperature and, as a result, symmetrical peaks of these mono- and divalent cations were obtained on the SMBSG B-5 silica gel calcinated at 1000 degrees C as the stationary phase. In contrast, the peak resolution between these mono- and divalent cations was not improved. Therefore, crown ethers [18-crown-6 (1,4,7,10,13,15-hexaoxacyclooctadecane), 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane)] were added to the eluent for the complete separation of these mono- and divalent cations. Excellent simultaneous separation and highly sensitive detection at 275 nm were achieved in 25 min on a column (150x4.6 mm I.D.) packed with SMBSG B-5 silica gel calcinated at 1000 degrees C by elution with 0.75 mM tyramine-0.25 mM oxalic acid at pH 5.0 containing either 1.0 mM 18-crown-6 or 10 mM 15-crown-5.
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PMID:Simultaneous separation of common mono- and divalent cations on a calcinated silica gel column by ion chromatography with indirect photometric detection and aromatic monoamines-oxalic acid, containing crown ethers, used as eluent. 1210 45

Ion chromatographic behavior of common mono- and divalent cations (Li+, Na+, NH4+, K+, Mg2+ and Ca2+) on columns packed with silica gels (Super Micro Bead Silica Gel B-5, SMBSG B-5) calcinated at 200, 400, 600, 800 and 1000 degrees C for 5 h was investigated using nitric acid containing crown ethers [18-crown-6 (1,4,7,10,13,15-hexaoxacyclooctadecane) and 15-crown-5 (1,4,7,10,13-pentaoxacyclopentadecane)] as eluent. When using 0.5 mM HNO3 as the eluent, the calcination had almost no effect on the improvement of peak resolution between these mono- and divalent cations. In contrast, when using 0.5 mM HNO3 containing crown ethers as the eluent, with increasing the calcinating temperature, the amount of crown ethers adsorbed on the corresponding calcinated SMBSG B-5 silica gels columns increased and, as a consequence, peak resolution between these mono- and divalent cations was quite improved. Excellent simultaneous separation of these mono- and divalent cations was achieved on column (150x4.6 mm I.D.) packed with the SMBSG B-5 silica gel calcinated at 1000 degrees C by elution with 0.5 mM HNO3 containing either 1.0 mM 18-crown-6 or 5.0 mM 15-crown-5.
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PMID:Retention behavior of common mono- and divalent cations on calcinated silica gel columns in ion chromatography with conductimetric detection and the use of nitric acid, containing crown ethers, as eluents. 1210 47

The application of unmodified silica gel (Super Micro Bead Silica Gel B-5, SMBSG B-5) as cation-exchange stationary phase in ion chromatography with indirect photometric detection for common mono- and divalent cations (Li+, Na+, NH4+, K+, Mg2+ and Ca2+) was carried out using 0.75 mM tyramine [4-(2-aminoethyl)phenol]-0.25 mM oxalic acid at pH 5.0 as the eluent. Although complete group separation between these mono- and divalent cations was achieved on the SMBSG B-5 column (150x4.6 mm I.D.) in 12 min, peak shapes of NH4+ and K+ were strongly tailed. Hence, the application of SMBSG B-5 silica gel treated with conc. hydrochloric acid at reflux-temperature for 12 h for the simultaneous separation of these cations was carried out. Although the retention volumes of these cations decreased on the acid-treated SMBSG B-5 silica gel column, the peak shapes of NH4+ and K+ were quite improved. Excellent simultaneous separation and highly sensitive detection at 275 nm [detection limits (signal-to-noise ratio of 3 and injection volume of 20 microl), 0.34 microM for Li+, 0.47 microM for Na+, 0.39 microM for NH4+, 0.59 microM for K+, 0.24 microM for Mg2+ and 0.28 microM for Ca2+] were achieved in 15 min on the acid-treated SMBSG B-5 column using 0.5 mM tyramine-0.2 mM oxalic acid-10 mM 18-crown-6 (1,4,7,10,13,15-hexaoxacyclooctadecane) at pH 5.5 as the eluent.
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PMID:Simultaneous separation of common mono- and divalent cations on an acid-treated silica gel column by ion chromatography with indirect photometric detection and tyramine-oxalic acid, containing 18-crown-6 as eluent. 1210 48

Solid-phase extraction (SPE) is becoming a commonly used extraction technique. Most existing SPE methods extract a single drug from a relatively clean biological matrix (e.g., plasma, serum, or urine) using a silica-based column. These methods, however, are generally not satisfactory for forensic applications because the majority of biological samples are not as clean (e.g., whole blood, bile, tissues). Silica-based columns also may have reproducibility and stability problems. Polymer-based columns have been developed to overcome some of these limitations. In this study, sequential extraction of acidic, neutral, and basic drugs from whole blood using a polymer-based column, Oasis MCX, was undertaken. The extraction procedure developed involved a conditioning step using methanol followed by water; a three-step wash sequence using water, 0.1 M hydrochloric acid, then water/methanol (95:5); and two elution steps. One elution step was for acidic and neutral drugs utilizing acetone/chloroform (1:1), and a second used ethyl acetate/ammonium hydroxide (98:2) for basic drugs. Of the drugs tested, 75% were extractable from whole blood and detectable at therapeutic concentrations. Good recoveries and clean extracts were achieved for the basic drugs; however, the extracts were not as clean for acidic drugs. Unfortunately, the Oasis MCX procedure was not suitable for extracting all drugs (e.g., benzodiazepines).
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PMID:A general screening method for acidic, neutral, and basic drugs in whole blood using the Oasis MCX column. 1222 13

Silica nanoparticles were prepared in a microemulsion system, using polyoxyethylene nonylphenyl ether/cyclohexane/ammonium hydroxide. The surface charge of the particle was modified with PLL [poly(L-lysine)]. PAGE demonstrated the ability of PMS-NP (PLL-modified silica nanoparticles) to bind and protect antisense ODNs (oligonucleotides). The intracellular localization of FITC-labelled ODN was investigated by fluorescence microscopy. The results demonstrated that ODN could be delivered to cytoplasm. Flow-cytometry analysis showed a 20-fold enhancement of ODN delivered by PMS-NP compared with free ODN for a serum-free medium. Blocking efficacy of c- myc antisense ODN, delivered by PMS-NP, was examined in HNE1 and HeLa cell lines. Significant down-regulation of c- myc mRNA levels was observed in both the cell lines. However, the cellular uptake efficiency and antisense effects on target gene decreased in the presence of serum-containing medium. The analysis of the filtration assay showed that PMS-NP interacted with serum proteins. These results indicated that PMS-NP was a suitable delivery vector for antisense ODN, although its delivery efficiency decreased in the presence of a serum-containing medium.
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PMID:Poly(L-lysine)-modified silica nanoparticles for the delivery of antisense oligonucleotides. 1503 38


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