Numerical results in the Kondo problem

A numerically solvable Kondo model is formulated. It is shown that for certain cases the limit T → 0 does not yield the correct ground state.     

Sampling, storage, and analysis of C2-C7 non-methane hydrocarbons from the US National Oceanic and Atmospheric Administration Cooperative Air Sampling Network glass flasks

An analytical technique was developed to analyze light non-methane hydrocarbons (NMHC), including ethane, propane, iso-butane, n-butane, iso-pentane, n-pentane, n-hexane, isoprene, benzene and toluene from whole air samples collected in 2.5l-glass flasks used by the National Oceanic and Atmospheric Administration, Earth System Research Laboratory, Global Monitoring Division (NOAA ESRL GMD, Boulder, CO, USA) Cooperative Air Sampling Network. This method relies on utilizing the remaining air in these flasks (which is at below-ambient pressure at this stage) after the completion of all routine greenhouse gas measurements from these samples. NMHC in sample aliquots extracted from the flasks were preconcentrated with a custom-made, cryogen-free inlet system and analyzed by gas chromatography (GC) with flame ionization detection (FID). C2-C7 NMHC, depending on their ambient air mixing ratios, could be measured with accuracy and repeatability errors of generally < or =10-20%. Larger deviations were found for ethene and propene. Hexane was systematically overestimated due to a chromatographic co-elution problem. Saturated NMHC showed less than 5% changes in their mixing ratios in glass flask samples that were stored for up to 1 year. In the same experiment ethene and propene increased at approximately 30% yr(-1). A series of blank experiments showed negligible contamination from the sampling process and from storage (<10 pptv yr(-1)) of samples in these glass flasks. Results from flask NMHC analyses were compared to in-situ NMHC measurements at the Global Atmospheric Watch station in Hohenpeissenberg, Germany. This 9-months side-by-side comparison showed good agreement between both methods. More than 94% of all data comparisons for C2-C5 alkanes, isoprene, benzene and toluene fell within the combined accuracy and precision objectives of the World Meteorological Organization Global Atmosphere Watch (WMO-GAW) for NMHC measurements.     

Evaluation of solid adsorbent materials for cryogen-free trapping-gas chromatographic analysis of atmospheric C2-C6 non-methane hydrocarbons

Nine commercial solid adsorbent materials (in order of decreasing surface area: Carboxen 1000, Carbosieve S III, molecular sieve 5A, molecular sieve 4A, silica gel, Carboxen 563, activated alumina, Carbotrap and Carboxen 1016) were investigated for their ability to trap and release C2-C6 non-methane hydrocarbons (NMHCs) in atmospheric samples for subsequent thermal desorption gas chromatography-flame ionization detection analysis (GC-FID). Recovery rates for 23 NMHCs and methyl chloride (CH3Cl) were determined. A microtrap filled with the three adsorbents Carbosieve S III, Carboxen 563 and Carboxen 1016 was found to allow for the analysis of the widest range of target analytes. A detection limit of approximately 3pptC [parts per trillion (carbon)] in a 1l air sample and a linear response over a wide range of volatilities and sample volumes was determined for this configuration. Water vapor in the sample air was found to causes interference in trapping and subsequent chromatographic analysis of light NMHCs. A Peltier-cooled, regenerable water trap inserted into the sample flow path was found to mitigate these problems and to allow quantitative and reproducible results for all analytes at all tested humidity conditions.     

Reactions of Podophyllotoxin with DDQ

Introduction 2, 3-Dichloro-5, 6-dicyanobenzoquinone (DDQ) can react with lignans of the mono- arylidene-butyrolactone1, aryltetralin2, dibenzylbutane3 and aryltetralin-butyrolactone4,5 series. We have studied the reactions of this reagent with podophyllotoxin 1, which is a well-known natural product on account of its long history of use in folk medicine and the biological activity of its many derivatives6. In particular, derivatives of 4-demethyl epipodophyllotoxin are used in cancer chemo…     

Misfolding of Luciferase at the Single‐Molecule Level

The folding of complex proteins can be dramatically affected by misfolding transitions. Directly observing misfolding and distinguishing it from aggregation is challenging. Experiments with optical tweezers revealed transitions between the folded states of a single protein in the absence of mechanical tension. Nonfolded chains of the multidomain protein luciferase folded within seconds to different partially folded states, one of which was stable over several minutes and was more resistant to forced unfolding than other partially folded states. Luciferase monomers can thus adopt a stable misfolded state and can do so without interacting with aggregation partners. This result supports the notion that luciferase misfolding is the cause of the low refolding yields and aggregation observed with this protein. This approach could be used to study misfolding transitions in other large proteins, as well as the factors that affect misfolding.     

An investigation of the coagulological potential of the venoms of some Central Asian snakes

The compositions of the proteolytic complexes of the venoms of the crotalid Agkistrodon halys halysand the viperid Echis multisquamatushave been investigated with the aid of a large number of specific natural and model substrates. A comparative analysis of the results obtained has revealed a predominance in the crotalid venom of fibrinogen-hydrolyzing enzymes, while the viperid venom is characterized as a procoagulant of the prothrombin-activating type. Among the fibrinogenases of the crotalid venom, a thrombin-like enzyme and a plasmin-like proteinase have been revealed and obtained in a purified state. A prothrombin-activating enzyme from the viperid venom has been isolated in the purified state and characterized with the aid of specific substrates.     

An investigation of the coagulological potential of the venoms of some Central Asian snakes

The compositions of the proteolytic complexes of the venoms of the crotalid Agkistrodon halys halysand the viperid Echis multisquamatushave been investigated with the aid of a large number of specific natural and model substrates. A comparative analysis of the results obtained has revealed a predominance in the crotalid venom of fibrinogen-hydrolyzing enzymes, while the viperid venom is characterized as a procoagulant of the prothrombin-activating type. Among the fibrinogenases of the crotalid venom, a thrombin-like enzyme and a plasmin-like proteinase have been revealed and obtained in a purified state. A prothrombin-activating enzyme from the viperid venom has been isolated in the purified state and characterized with the aid of specific substrates. Work performed with the support of the Nederlandse Organisatie voor Wetenschappelijk Onderzoek.Institute of Biochemistry of the Academy of Sciences of the Uzebekistan Republic, Tashkent. Department of Biochemistry, Cardiovascular Research Institute, University of Limburg, Maastricht, The Netherlands. Translated from Khimiya Prirodnykh Soedinenii, Vol. 3, pp. 447–454, May–June, 1993.