Showing papers by "University of Perugia published in 1971"
TL;DR: The hypothesis that the impairment of the right brain-damaged patients on tasks of complex visual perception may be due, at least in part, to unilateral spatial neglect is supported.
82 citations
TL;DR: In this article, the authors provide a sufficiently complete summary of all the quantitative and semiquantitative information available concerning electrophilic substitution in five-membered heteroaromatic rings.
Abstract: Publisher Summary The chapter attempts to provide a sufficiently complete summary of all the quantitative and semiquantitative information available concerning electrophilic substitution in five-membered heteroaromatic rings. The chapter is organized in the following manner. After a preliminary introduction to the “aromaticity” of the five-membered rings, the discussion is centered mainly on the substitution process itself, and the mechanism of the various electrophilic substitutions is considered separately. Afterward attention is shifted from the electrophile to the heteroaromatic substrate, and the relative reactivity of different rings and ring positions is widely examined. Finally, the problem of the transmission of electronic effects of substituents across these rings and the application of Kammett-type correlations is discussed. Systems considered are the parent heterocycles with one heteroatom (furan, thiophene, selenophene, and pyrrole), their monoaza and polyaza derivatives, and the monobenzo derivatives of the above systems. General surveys on the chemistry of furan,l thiophene,2 pyrrle, benz∼thiophene, an d selenophene4 have been published in recent years; reference is made to them, whenever necessary.
81 citations
TL;DR: A study of the absorbance properties of the enzyme in the 300-500 mn range, where the bound coenzyme should show its charac- teristic absorption band, would be highly desirable, since similar studies have provided a good deal of in- formation in other pyridoxal phosphate dependent enzymes.
50 citations
Journal Article•
47 citations
TL;DR: In this paper, the internal heavy atom effect on the radiative and radiationless transitions from the lowest excited states of phenanthrene was investigated, and the halogen substitution induces a larger increase of the intersystem crossing S 1 -T 1 rate than of the T 1 -S 0 one, resulting in a higher overall triplet formation quantum yield and higher radiative decay quantum efficiency from the triplet.
44 citations
TL;DR: This chapter describes structure and catalytic role of the functional groups of aspartate aminotransferase (AAT), a particularly interesting enzyme because its catalytic activity is duplicated by its coenzyme moiety, even in the absence of the specific apoprotein.
Abstract: Publisher Summary This chapter describes structure and catalytic role of the functional groups of aspartate aminotransferase (AAT). AAT is a particularly interesting enzyme because its catalytic activity is duplicated, though with a much smaller efficiency, by its coenzyme moiety, even in the absence of the specific apoprotein. An impressive mass of information on the structure and function of AAT has been obtained in recent years. The general pattern of the chemical events occurring at the active site has been established; the reaction proceeds through a great number of discrete steps, each of which proceeds fast because it is catalyzed by a number of suitably disposed groups on the enzyme; conformational changes contribute to placing the various groups involved in the most appropriate position for the catalysis of each step. Many of the rate and equilibrium constants for the interconversion of the intermediates have been measured. In this chapter, concepts related to the assembly of the holoenzyme are discussed. The binding of the coenzyme to the protein is elaborated. The interaction between the holoenzyme and the substrate is explained. The quaternary structure of the enzyme is also described.
32 citations
TL;DR: In this article, the fundamental vibrations of the Fe(CN) 5 NO 2− ion were assigned to a C 4v symmetry model for the anion, and the significance of the resulting valence force constants is briefly discussed.
30 citations
TL;DR: In this paper, thin-layer chromatography of carbohydrates on silica-gel layers impregnated with molybdic or phospho-tungstic acid has been investigated.
21 citations
TL;DR: In this article, a rough parallelism holds between calculated and observed overall splittings within each tetrahedral T1 band, and a possible way to rationalization of the observed patterns of band components and of their polarization behaviour is outlined in terms of different kinds of geometrie distortions, vibronic couplings and a more appropriate treatment of spin-orbit coupling effects, including those in the ligand atoms.
19 citations
TL;DR: In this article, the polarographic properties of CH3CN have been investigated and a general reduction mechanism is proposed and discussed, and the effects of substituents on the mechanism and on the halfwave potentials have also been examined.
15 citations
TL;DR: In this article, the synthesis by Bruni and Levi, modified by Fackler and Coucouvanis, from ammonium polysulfide has been extended to aliphatic aldehydes, and perthiopivalate (CH 3 ) 3 CCSSS − has been prepared.
TL;DR: In this article, the second-order rate constants are little influenced by the solvent, while the first-order rates vary with its nucleophilicity and steric requirements, and the results are discussed in terms of a suggested reaction mechanism.
Journal Article•
TL;DR: Valdinizza is a typical hypersthene chondrite, belonging to the type 6 chondrites of Van Schmus and Wood (1967), its structure shows evidence of a period of high-temperature recrystallization; interesting features of shock-metamorphism are notable, the microtexture deformations suggesting a high level of stress.
Abstract: The principal data are collected about the fall and the distribution of the fragments of the Valdinizza, Italy, meteorite A complete individual, weighing 872 g, preserved in the United States National Museum, Washington, D C, is described in some detail The mineralogical composition is olivine, Fa25; hypersthene, Fs23; plagioclase, An10; maskelynite; nickel-iron; troilite; chromite; ilmenite and possibly a phosphate mineral Valdinizza is a fairly typical hypersthene chondrite, belonging to the type 6 chondrites of Van Schmus and Wood (1967); its structure shows evidence of a period of high-temperature recrystallization; interesting features of shock-metamorphism are notable, the microtexture deformations suggesting a high level of stress
TL;DR: In this paper, the crystal and molecular structure of dibromo-bis (O-ethyl, N-phenylthiocarbamate)cobalt(II), Co[(C6H5)NHCS(OC2H5)]2Br2 has been determined from three-dimensional single-crystal X-ray data collected by standard film techniques.
TL;DR: In this paper, the relative importance of primary steric effects in acetylation of benzene and thiophene rings was studied and the smaller steric hindrance found in the hetero-aromatic system was explained in terms of molecular geometry.
TL;DR: In this article, a picture of the distribution of various phenolics was obtained by combining the total phenolics determination with selective precipitation of flavonoids with formaldehyde and tannins with cinchonine.
Abstract: The oxidative browning of white wines (maderisation) obtained by fermenting musts derived from progressive pressing cycles, was studied in relation to the phenolic concentration.
A picture of the distribution of the various phenolics was obtained by combining the total phenolics determination with selective precipitation of flavonoids with formaldehyde and tannins with cinchonine.
Both enzymic and non-enzymic browning are directly related to the flavonoids concentration in the wines; a progressive insolubilisation of tannic flavonoids and a polymerisation of the non-tannic flavonoids accompanies the colour change.
The concentration of non-flavonoid phenolics does not vary significantly during oxidative degradation and therefore they tend to become the most representative phenolic fraction in the maderised wines.
TL;DR: Bis(O,O′-diethyldithiophosphato)nickel(II) behaves in a qualitatively similar way with both primary and secondary amines in that 1:1 and 1:2 adducts are found.
TL;DR: The results suggested that within platelets and leukocytes there exists only a single enzyme, and the independent variation of platelet andLeukocyte alkaline phosphatase activity in Down's syndrome is probably not caused by differences in structural or regulator genes between these blood cells.
TL;DR: In this paper, the infrared spectrum of crystalline nitrosyltricarbonylcobalt has been measured at different temperatures between 4000 and 300 cm −1, and it has been shown that the form stable between the melting point and 248°K has the same degree of disorder as the liquid.
TL;DR: In this article, an assignment of the fundamentals relative to the Mn(CN)5NO3− ion was proposed on the basis of a C4v ion symmetry, and normal coordinate treatment was carried out using a diagonal symmetry force field.
TL;DR: In this article, the electronic spectra and magnetic properties of the compounds [ReX5PPh3] (X=Cl, Br; DPE=diphenylphosphinoethane) of D4h symmetry were investigated.
TL;DR: In the solid state, complexes of nickel(II) perchlorate with N - or N,N -substituted thioureas (L ) exist in the solid states as octahedral Ni L 6 (ClO 4 ) 2 or, more rarely, as quadratic low-spin Ni L 4 (CLO 4 ), and the latter can be solvoyzed to pseudooctahedral species of the [Ni L 4− χ (acetone) 2+ χ ] 2+
TL;DR: It is concluded that lung morphogenesis is dependent upon mesenchymal cell metabolism and that the inductive activity takes place for a certain period of incubation.
Abstract: Effects of puromycin on chick embryo lung differentiation in vitro has been studied. Lung morphogenesis stops as a result of wide, deep and specific damages of mesenchymal cells, produced by inhibitor administration. Treated cultures, when transferred into normal nutrient medium, exhibit a certain recovery. We can conclude that 1) lung morphogenesis is dependent upon mesenchymal cell metabolism and that 2) the inductive activity takes place for a certain period of incubation.
TL;DR: In this paper, the infrared spectra for Tetracyanopropenide (TCP) and tetracyansopentadienide (TPD) anions as KBr pellets in the range 4000-300 cm −1, are reported.
01 Jan 1971
TL;DR: Muscles of three patients affected by congenital hypothyroidism due to dysgenesis of the thyroid gland were studied by electron microscope and changes of the ultrastructure of the muscle fibers found with numerous morphological abnormalities of the mitochondria were observed.
Abstract: Muscles of three patients (2 years, 2 years and 7 months, and 11 years of age) affected by congenital hypothyroidism due to dysgenesis of the thyroid gland were studied by electron microscope. The biopsies were performed on the quadriceps muscle. Several alterations were found in the ultrastructure of the muscle fibers. The contractile material underwent atrophy by two recessive processes: by reduction and by degeneration. The former, which affected mainly the white fibers, led to the progressive detachment of myofilaments from the periphery of the myofibrils while they maintainad a normal arrangement in the center. Consequently, their diameter decreased and their interfibrillar spaces enlarged. The latter enlargment, involving the red fibers, caused areas of dedifferentiation involving either the contractile apparatus or the other cell organelles. Modifications of the sarcolemma and basement membrane were seen in the fibers affected by the atrophying processes of the contractile material. Changes of the ultrastructure of the sarcoplasmic reticulum and of the T system were observed with numerous morphological abnormalities of the mitochondria. In addition, accumulation of glycogen and striking changes of the satellite cells were found. The ultrastructural findings are reviewed and discussed in relation to the literature on hypothyroid myopathy.