Search results for "Spectrophotometry"
showing 10 items of 644 documents
Amino acid substitutions enhancing thermostability of Bacillus polymyxa beta-glucosidase A
1996
Mutations enhancing the thermostability of β-glucosidase A of Bacillus polymyxa, a family 1 glycosyl hydrolase, have been obtained after hydroxylamine mutagenesis of a plasmid containing the bglA gene, transformation of Escherichia coli with the mutagenized plasmid, and identification of transformant colonies that showed β-glucosidase activity after a thermal treatment that inactivated the wild-type enzyme. Two additive mutations have been characterized that cause replacement of glutamate at position 96 by lysine and of methionine at position 416 by isoleucine respectively. The thermoresistant mutant enzymes showed increased resistance to other denaturing agents, such as pH and urea, while …
Thermal lens spectrometry in biochemical analysis.
1994
The photothermal spectroscopic techniques, with special emphasis on the thermal lens spectrometry (TLS), are introduced to the non-specialist in laser spectroscopy. The following topics are treated on an elementary basis: fundamentals and analytical characteristics, instrumentation, selectivity and multi-wavelength capability, the models describing the signal-concentration relationship, the sensitivity, background noise and limits of detection, the influence of light scattering and flow. Applications related to the fields of clinical and biochemical analysis and organic pollution are given. The thermal lens circular dichroism and the infrared TLS are also briefly outlined.
Thermal degradation and isomerisation kinetics of triolein studied by infrared spectrometry and GC–MS combined with chemometrics
2008
Authors version of article published in the journal: Chemistry and Physics of Lipids Published version available on Science Direct: http://dx.doi.org/10.1016/j.chemphyslip.2008.12.002 Triolein, a triglyceride containing oleic acid as the only acid moiety in the glyceride molecules has been isothermally treated at 280,300,and 325 degrees C in glass vials under nitrogen atmosphere. The products formed during the thermal treatment at each temperature have been analysed both by infrared spectrometry and GC-MS. The CC-MS analysis was performed after derivatisation of the fatty acids into their methyl esters (FAMEs). Chemometric tools were used in determining the concentrations of the main produc…
Impulsive solvent heating probed by picosecond x-ray diffraction
2006
The time-resolved diffraction signal from a laser-excited solution has three principal components: the solute-only term, the solute-solvent cross term, and the solvent-only term. The last term is very sensitive to the thermodynamic state of the bulk solvent, which may change during a chemical reaction due to energy transfer from light-absorbing solute molecules to the surrounding solvent molecules and the following relaxation to equilibrium with the environment around the scattering volume. The volume expansion coefficient alpha for a liquid is typically approximately 1 x 10(-3) K(-1), which is about 1000 times greater than for a solid. Hence solvent scattering is a very sensitive on-line t…
Reduction of clozapine-induced hypersalivation by pirenzepine is safe.
2004
Introduction Hypersalivation is known as a frequent, disturbing, and socially stigmatizing side effect of therapy with the atypical antipsychotic clozapine. It has been shown that the addition of the anticholinergic pirenzepine is able to reduce clozapine-induced hypersalivation, probably by blocking M4-receptors. Nevertheless, a pharmacokinetic interaction between both compounds cannot be excluded. Methods In this pilot study, 29 schizophrenic patients (ICD-10; 51.7 % female; age: 36.7 +/- 8.7 years [mean +/- SD]) were included. Serum concentrations of clozapine and its pharmacologically active metabolite N-desmethylclozapine were determined under steady-state conditions by automated HPLC …
Quantitative colorimetric-imaging analysis of nickel in iron meteorites.
2011
A quantitative analytical imaging approach for determining the nickel content of metallic meteorites is proposed. The approach uses a digital image of a series of standard solutions of the nickel-dimethylglyoxime coloured chelate and a meteorite sample solution subjected to the same treatment as the nickel standards for quantitation. The image is processed with suitable software to assign a colour-dependent numerical value (analytical signal) to each standard. Such a value is directly proportional to the analyte concentration, which facilitates construction of a calibration graph where the value for the unknown sample can be interpolated to calculate the nickel content of the meteorite. The…
Presence and coding properties of 2'-O-methyl-5-carbamoylmethyluridine (ncm5Um) in the wobble position of the anticodon of tRNA(Leu) (U*AA) from brew…
1992
AbstractThe unknown modified nucleoside U* has been isolated by enzymatic and HPLC protocols from tRNALeu(U*AA) recently discovered in brewer's yeast. The pure U* nucleoside has been characterized by electron impact mass spectroscopy, and comparison of its chromatographic and UV-absorption properties with those of appropriate synthetic compounds. The structure of U* was established as 2′-O-methyl-5-carbamoylmethyluridine (ncm5Um). The yeast tRNALeu (U*AA) is the only tRNA so far sequenced which has been shown to contain ncm5Um. The location of such a modified uridine at the first position of the anticodon restricts the decoding property to A of the leucine UUA codon.
Determination of pesticide residues in fruit and vegetables.
1996
A review concerning the determination of pesticide residues in fruit and vegetables is presented. The basic principles and recent developments in the extraction and quantitation of pesticides are discussed. Consideration is given to solid phase and supercritical extraction techniques, automation and robotic systems, and immunoassay procedures.
Automated simultaneous triple dissolution profiles of two drugs, sulphamethoxazole-trimethoprim and hydrochlorothiazide-captopril in solid oral dosag…
2003
This article deals with the simultaneous determination of three dissolution profiles with the aid of the new and emerging continuous-flow methodology known as multicommutation. This methodology is based on a flow network of a set of solenoid valves controlled by the computer and acting as independent multicommutators to allow the easy and automated control of flowing solutions. The obtained three dissolution profiles from one dosage form are the whole formulation profile or "global profile" recommended by pharmacopoeias, and, at same time, are recorded two "individual" profiles from two drugs present in the formulation. This is the second attempt to obtain simultaneously three dissolution p…
Photochemical electrocyclisation of 3-vinylindoles to pyrido[2,3-a]-, pyrido[4,3-a]- and thieno[2,3-a]-carbazoles: Design, synthesis, DNA binding and…
2009
In the context of the design and synthesis of DNA ligands, some new hetarene annelated carbazoles were synthesized. As lead structure the intercalating tetracyclic systems pyrido[2,3-a]- and pyrido[4,3-a]-carbazoles and in one case a thieno[2,3-a]-carbazole were taken into account. A dialkyl amino amidic chain was introduced to the planar chromophoric system with the intent to generate minor groove binding properties. The cytotoxicity of some compounds was examined by the NCI antitumor screening. Furthermore, biophysical as well as biochemical studies were performed in order to get some information about the DNA-binding properties and inhibition of DNA related functional enzymes of this new…