1,130 research outputs found
The effect of salts on the derivatization and chromatography of amino acids
Effect of salts on derivatization and chromatography of amino acid
The hydrolysis of proteins
Temperature effects on hydrolysis reaction in protein amino acid
Assessing the efficiency of first-principles basin-hopping sampling
We present a systematic performance analysis of first-principles
basin-hopping (BH) runs, with the target to identify all low-energy isomers of
small Si and Cu clusters described within density-functional theory. As
representative and widely employed move classes we focus on single-particle and
collective moves, in which one or all atoms in the cluster at once are
displaced in a random direction by some prescribed move distance, respectively.
The analysis provides detailed insights into the bottlenecks and governing
factors for the sampling efficiency, as well as simple rules-of-thumb for
near-optimum move settings, that are intriguingly independent of the distinctly
different chemistry of Si and Cu. At corresponding settings, the observed
performance of the BH algorithm employing two simple, general-purpose move
classes is already very good, and for the small systems studied essentially
limited by frequent revisits to a few dominant isomers.Comment: 11 pages including 8 figures; related publications can be found at
http://www.fhi-berlin.mpg.de/th/th.htm
Gas-liquid chromatography of amino acids in biological substances
Developing gas-liquid chromatographic method for quantitative analysis of amino acids in blood plasma and urin
The quantitative determination of chromic oxide in feeds and feces
Digitized 2007 AES.Includes bibliographical references (page 16)
The search for an identification of amino acids, nucleobases and nucleosides in samples returned from Mars
The Mars Sample Return mission will provide us with a unique source of material from our solar system; material which could advance our knowledge of the processes of chemical evolution. As has been pointed out, Mars geological investigations based on the Viking datasets have shown that primordial Mars was in many biologically important ways similar to the primordial Earth; the presence of surface liquid water, moderate surface temperatures, and atmosphere of carbon dioxide and nitrogen, and high geothermal heat flow. Indeed, it would seem that conditions on Earth and Mars were fundamentally similar during the first one billion years or so. As has been pointed out, Mars may well contain the best preserved record of the events that transpired on the early planets. Examination of that early record will involve searching for many things, from microfossils to isotopic abundance data. We propose an investigation of the returned Mars samples for biologically important organic compounds, with emphases on amino acids, the purine and pyrimidine bases, and nucleosides
The search for and identification of amino acids, nucleobases and nucleosides in samples returned from Mars
An investigation of the returned Mars samples for biologically important organic compounds, with emphasis on amino acid, the puring and pyrimidine bases, and nucleosides is proposed. These studies would be conducted on subsurface samples obtained by drilling past the surface oxidizing layer with emphasis on samples containing the larges quantities of organic carbon as determined by the rover gas chromatographic mass spectrometer (GCMS). Extraction of these molecules from the returned samples will be performed using the hydrothermal extraction technique described by Cheng and Ponnamperuma. More rigorous extraction methods will be developed and evaluated. For analysis of the extract for free amino acids or amino acids present in a bound or peptidic form, aliquots will be analyzed by capillary GCMS both before and after hydrolysis with 6N hydrochloric acid. Establishment of the presence of amino acids would then lead to the next logical step which would be the use of chiral stationary gas chromatography phases to determine the enatiomeic composition of the amino acids present, and thus potentially establish their biotic or abiotic origin. Confirmational analyses for amino acids would include ion-exchange and reversed-phase liquid chromatographic analysis. For analyses of the returned Mars samples for nucleobases and nucleosides, affinity and reversed-phase liquid chromatography would be utilized. This technology coupled with scanning UV detection for identification, presents a powerful tool for nucleobase and nucleoside analysis. Mass spectrometric analysis of these compounds would confirm their presence in samples returned form Mars
The determination of lindane residues on pickles : critical points in the Schechter-Hornstein colorimetric method
The work reported was done under Department of Agricultural Chemistry Research Project 132, 'Analytical Services'--P. [2].Digitized 2007 AES.Includes bibliographical references (page 24)
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