Synthesis of 1-acyl-5-pyrazolones and pyrrolidino[2,3-c]pyrazol-3-ones

The reactivity of acetamidrazones I in strong basicity conditions was examined. When compounds I are reacted with equivalent quantities of α-haloketones in sodium alcoholate, the pyrrolidino[2,3-c]pyrazol-3-ones IV were obtained by intermediate formation of 1-acyl-3-amino-5-pyrazolones III .     

Protein-Based Biosensors for Diabetic Patients

In this article we show the recent progress in the field of glucose sensing based on the utilization of enzymes and proteins as probes for stable and non-consuming fluorescence biosensors. We developed a new methodology for glucose sensing using inactive forms of enzymes such as the glucose oxidase from Aspergillus niger, the glucose dehydrogenase from the thermophilic microorganism Thermoplasma acidophilum, and the glucokinase from the thermophilic eubacterium Bacillus stearothermophilus. Glucose oxidase was rendered inactive by removal of the FAD cofactor. The resulting apo-glucose oxidase still binds glucose as observed from a decrease in its intrinsic tryptophan fluorescence. 8-Anilino-1-naphthalene sulfonic acid was found to bind spontaneously to apo-glucose oxidase as seen from an enhancement of the ANS fluorescence. The steady state intensity of the bound ANS decreased 25% upon binding of glucose, and the mean lifetime of the bound ANS decreased about 40%. These spectral changes occurred with a midpoint from 10 to 20 mM glucose, which is comparable to the KD of holo-glucose oxidase. The ANS-labeled apo-glucose dehydrogenase from Thermoplasma acidophilum also displayed an approximate 25% decrease in emission intensity upon binding glucose. This decrease can be also used to measure the glucose concentration. The thermophilic apo-glucose dehydrogenase was also stable in the presence of organic solvents, allowing determination of glucose in the presence of acetone. The third enzyme used for glucose sensing was the glucokinase from Bacillus stearothermophilus. A fluorescence competitive assay for the determination of glucose was developed based on the utilization of this thermostable enzyme. Taken together, our results show that enzymes which use glucose as their substrate can be used as reversible and non-consuming glucose biosensors in the absence of required co-factors. Moreover, the possibility of using inactive apo-enzymes for a reversible sensor greatly expands the range of proteins which can be used as sensors, not only for glucose, but for a wide variety of biochemically relevant analytes.     

HREELS investigation of the first stage of interaction of atomic hydrogen with GaAs(1 1 0) surfaces

The interaction of atomic hydrogen with a cleaved GaAs(1 1 0) surface has been investigated by high resolution electron energy loss spectroscopy. This technique, which is extremely surface sensitive, enables the detection of very small amounts of adsorbate and the indication of the adsorption sites. We have exposed a GaAs(1 1 0) surface to atomic hydrogen in the 10-10⁴ L range. This upper limit corresponds to the onset of the monolayer coverage. The effect of the H exposure is detected in the region of phonon-plasmon losses already at an exposure of 10 L, indicating the occurrence of a band bending. The three layer model for the dielectric function of the GaAs(1 1 0) surface had to be adopted to account for the results. At higher loss energies the stretching vibrations of Ga-H and As-H are also detected from the lowest exposures. The possibility that the As-H signal is given by a double loss (Ga-H + phonon) is ruled out for this surface, therefore, it comes out that from the first stage of interaction H bonds to both Ga and As. The intensity of both Ga-H and As-H signal increases faster than the expected number of adsorbed H atoms suggesting that the dynamical dipole drops drastically with increasing exposure.     

Study of the dielectric loss of heavily doped NaCl:CaCl2

The dielectric loss of NaCl doped with varying CaCl₂ concentrations is investigated at different frequencies and temperatures. An analysis of the results reveals that the observed relaxation loss is caused by three superimposed loss maxima, which are attributed to two kinds of impurity vacancy complexes and to precipitates.     

RDF analysis of structural evolution during the primary crystallization of the Fe40Ni38Mo4B18 glassy alloy

The changes in the atomic structure of amorphous Fe₄₀Ni₃₈Mo₄B₁₈ during the crystallization process were studied by X-ray diffraction. The radial distribution functions of various specimens frozen at significant points of the relative DSC thermograms, were obtained from the interference functions by means of the usual Fourier analysis.

It appears from the results that the onset of crystal formation implies the simultaneous occurrence of atomic rearrangements involving the basic structural units already present in the unannealed sample; a five-fold symmetry and icosahedral structure were found for these units. An effort was made to correlate the progress in the crystalline organization with the significant features of the DSC related thermograms.     

Tethered Satellites in the geophysical environment

Summary A short presentation is given of the basic physical principle of a Tethered-Satellite System. The motion equations are summarized. A variety of physical phenomena in the upper atmosphere and ionosphere, as well as related to geomagnetism and gravity field will benefit by such type of missions; they are briefly illustrated and discussed. Near-term and far-term perspective applications are finally presented. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

t−d excitons in the optical spectrum of semiconducting SmS and Sm1−xGdx alloys

Thermomodulation studies of the optical properties of Sm_1?xGd_xS alloys are presented for x ? 0.15. A new interpretation of the low energy absorption peaks as excitons, where a Sm 5d electron is bound to a localized hole in the 4f shell, is strongly suggested.     

Low-energy gamma-ray sources observed by the MISO telescope

Summary The MISO telescope is a gamma-ray detector operating in the (0.1÷20) MeV energy range. This instrument was flown success-fully from Palestine, Texas (U.S.A.) in May 1977, October 1978, September 1979 and May 1980. During the four flights, the telescope observed a number of galactic and extragalactic sources. The Crab Nebula was detected in 1980 and its spectrum was measured up to 2 MeV. Cygnus X-1 was observed in 1979 and 1980 and was found to be in different hard X-ray states on each occasion: in a superlow state in 1979 and in a low state in 1980. The COS-B high-energy (E>50 MeV) gamma-ray sources CG 135+1 (1978) and CG 195+4 (1978) were also observed by the same instrument. From the region containing CG 135+1 a 5σ excess was measured in the counting rate of the telescope above 120 keV. No statistically significant low-energy gamma-ray flux was detected from CG 195+4. The Seyfert galaxies NCG 4151 (1977, 1979, 1980), and MCG 8-11-11 (1979), the BL LAC object MK 501 (1979) and the ?peculiar? galaxy NGC 1275 (1979) were also searched for gamma-ray emission. The data on NGC 4151 and MCG 8-11-11 are consistent with power law spectra having photon indices α∼1 in the (0.1÷3) MeV energy range. Above this energy, the MISO and SAS-2/COS-B measurements require spectral breaks to α≥3. Upper limits were obtained on the emission from both MK 501 and NGC 1275. Paper presented at the 2° Convegno Nazionale di Fisica Cosmica, held at L'Aquila, 29 May–2 June 1984.     

Desaturase reactions complicate the use of norcarane as a mechanistic probe. Unraveling the mixture of twenty-plus products formed in enzyme-catalyzed oxidations of norcarane

Norcarane, bicyclo[4.1.0]heptane, has been widely used as a mechanistic probe in studies of oxidations catalyzed by several iron-containing enzymes. We report here that, in addition to oxygenated products, norcarane is also oxidized by iron-containing enzymes in desaturase reactions that give 2-norcarene and 3-norcarene. Furthermore, secondary products from further oxidation reactions of the norcarenes are produced in yields that are comparable to those of the minor products from oxidation of the norcarane. We studied oxidations catalyzed by a representative spectrum of iron-containing enzymes including four cytochrome P450 enzymes, CYP2B1, CYPDelta2B4, CYPDelta2E1, and CYPDelta2E1 T303A, and three diiron enzymes, soluble methane monooxygenase (sMMO) from Methylococcus capsulatus (Bath), toluene monooxygenase (ToMO) from Pseudomonas stutzeri OX1, and phenol hydroxylase (PH) from Pseudomonas stutzeri OX1. 2-Norcarene and 3-norcarene and their oxidation products were found in all reaction mixtures, accounting for up to half of the oxidation products in some cases. In total, more than 20 oxidation products were identified from the enzyme-catalyzed reactions of norcarane. The putative radical-derived product from the oxidation of norcarane, 3-hydroxymethylcyclohexene (21), and the putative cation-derived product from the oxidation of norcarane, cyclohept-3-enol (22), coelute with other oxidation products on low-polarity GC columns. The yields of product 21 found in this study are smaller than those previously reported for the same or similar enzymes in studies where the products from norcarene oxidations were ignored, and therefore, the limiting values for lifetimes of radical intermediates produced in the enzyme-catalyzed oxidation reactions are shorter than those previously reported.