Search results for "Chromatography"
showing 10 items of 5037 documents
Stability of Cannabinoids in Hair Samples Exposed to Sunlight
2000
It has been well recognized that hashish and marihuana lose potency during storage because of a decrease in the content of tetrahydrocannabinol (THC), which is the major psychoactive constituent of cannabis (1). The effect of oxygen on stored plant and resin materials or solutions of pure cannabinoids seems much less significant than that of higher temperatures (≥37 °C) or light (2)(3)(4)(5)(6)(7). A few data are available on the stability of THC and major metabolites in blood (8)(9)(10)(11). However, the stability of cannabinoids in the hair shaft has not been addressed, although scalp hair represents one of the most exposed parts of the body. Therefore, a study was performed to elucidate …
Enantioselective determination of plasma protein binding of common amphetamine-type stimulants.
2021
Amphetamine-type stimulants (ATS) like amphetamine ('speed'), methamphetamine ('crystal meth') and 3,4-methylenedioxy-N-methylamphetamine (MDMA, 'ecstasy') represent some of the most frequently abused drugs worldwide. Another less frequently abused ATS is 4-fluoroamphetamine (4-FA). The enantiomers of these four compounds exhibit different pharmacokinetic and pharmacodynamic properties. According to the free drug theory, the pharmacological properties of a substance are dependent on its plasma protein binding (PPB). However, data on PPB of stimulant enantiomers in humans are rare or non-existent. Human plasma samples were spiked with racemic mixtures of the stimulants and subjected to ultra…
Characterization of the synthetic cannabinoid MDMB-CHMCZCA
2016
The synthetic cannabinoid MDMB-CHMCZCA was characterized by various spectroscopic techniques including NMR spectroscopy and tandem mass spectrometry. The synthetic sample was found to be of S-configuration by VCD spectroscopy and comparison of the data with DFT calculations, while ECD spectroscopy was found to be inconclusive in this case. The enantiomeric purity of samples from test purchases and police seizures was assessed by a self-developed chiral HPLC method.
Analysis of a soluble lipid-protein complex carrying endogenous 11-cis retinaldehyde from bovine retinal pigment epithelium.
1989
A soluble lipid-protein complex in bovine retinal pigment epithelium is shown to carry endogenous 11-cis retinaldehyde, in the extent of 15% of the total 11-cis retinaldehyde found in this tissue. The complex, analyzed with respect to its chemical composition, exhibits a lipid composition close resembling the lipid composition of the rod outer segment membrane; the SDS-PAGE evidences the presence of a number of protein bands, two of which of 34 and 27 kDa appear glycoproteins. Finally, the lipid-protein complex exhibits a discrete level of a Cathepsin D-like protease activity. From the above, the possibility is discussed that the soluble lipid-protein complex could represent some phagolysos…
A single mutation in the recombinant light chain of tetanus toxin abolishes its proteolytic activity and removes the toxicity seen after reconstituti…
1994
Specific proteolysis by the tetanus toxin light chain of a vesicle-associated membrane protein (VAMP) involved in exocytosis is thought to underlie its intracellular blockade of neurotransmitter release. To substantiate this mechanism, recombinant light chain was expressed as a maltose binding protein-light chain fusion product in Escherichia coli. After purification of affinity chromatography and cleavage with factor Xa, the resultant light chain was isolated and its identity confirmed by Western blotting and N-terminal sequencing. It exhibited activity similar to that of the native light chain in proteolyzing its target in isolated bovine small synaptic vesicles and in hydrolyzing a 62-re…
Production and characterization of the recombinant Sphingomonas chlorophenolica pentachlorophenol 4-monooxygenase.
2001
Abstract Pentachlorophenol 4-monooxygenase (PCP4MO) from Sphingomonas chlorophenolica is a flavoprotein that hydroxylates PCP in the presence of NADPH and oxygen. In order to investigate the structure and function of active site, recombinant PCP4MO (rePCP4MO) was produced in Escherichia coli as a glutathione S-transferase (GST) fusion protein. Moreover, a tobacco etch virus (TEV) protease cleavage site (EKLYFQG) was introduced into GST-PCP4MO and a his-tagged TEV protease was employed. Hence, a two-step purification protocol was developed which allowed obtaining 15–20 mg of rePCP4MO from 1 L culture. The rePCP4MO revealed identity with native enzyme by SDS–PAGE and N-terminal sequence analy…
High-performance liquid chromatographic determination of diuretics in urine by micellar liquid chromatography.
1992
The use of micellar liquid chromatography for the determination of diuretics in urine by direct injection of the sample into the chromatographic system is discussed. The retention of the urine matrix at the beginning of the chromatograms was observed for different sodium dodecyl sulphate (SDS) mobile phases. The eluent strengths of a hybrid SDS-methanol micellar mobile phase for several diuretics were compared and related to the stationary phase/water partition coefficient with a purely micellar mobile phase. The urine band was appreciably narrower with a mobile phase of 0.05 M SDS-5% methanol (v/v) at 50 degrees C (pH 6.9). With this mobile phase the determination of bendroflumethiazide an…
Determination of metal concentrations in certified plastic reference materials after small-size autoclave and microwave-assisted digestion followed w…
2017
Abstract The digestion methods for the determination of As, Cd, Cr, Pb, Sb, Sn and Zn concentrations in plastic samples using microwave-assisted digestion (MW-AD) and small-size autoclave digestion was developed. The certified polyethylene, polypropylene, polyvinyl chloride and acrylonitrile butadiene styrene certified reference materials were used in order to find digestion method working properly for several sample matrices. Efficiency of the digestion methods was evaluated by analyzing the residual carbon in digests by TOC analyzer. MW-AD using a mixture of 7 mL of HNO 3 and 3 mL of H 2 O 2 as a digestion solution resulted in excellent recoveries for As, Cd, Pb, Sb and Zn, and were in th…
Differentiation among dairy products by combination of fast field cycling NMR relaxometry data and chemometrics
2021
A set of commercial milk and Sicilian cheeses was analysed by a combination of fast field cycling (FFC) nuclear magnetic resonance (NMR) relaxometry and chemometrics. The NMR dispersion (NMRD) curves were successfully analysed with a mathematical model applied on Parmigiano-Reggiano (PR) cheese. Regression parameters were led back to the molecular components of cheeses (water trapped in casein micelles, proteins and fats) and milk samples (water belonging to hydration shells around dispersed colloidal particles of different sizes and bulk water). The application of chemometric analysis on relaxometric data enabled differentiating milk from cheeses and revealing differences within the two sa…
Micelles in Mixtures of Sodium Dodecyl Sulfate and a Bolaform Surfactant
2006
Mixtures composed of water, sodium dodecyl sulfate (SDS), and a bolaform surfactant with two aza-crown ethers as polar headgroups (termed Bola C-16) were investigated by modulating the mole ratios between the components. The two surfactants have ionic and nonionic, but ionizable, headgroups, respectively. The ionization is due to the complexation of alkali ions by the aza-crown ether unit(s). Structural, thermodynamic, and transport properties of the above mixtures were investigated. Results from surface tension, translational self-diffusion, and small angle neutron scattering ( SANS) are reported and discussed. Interactions between the two surfactants to form mixed micelles result in a com…