Search results for "S2"

Logarithmic bundles of deformed Weyl arrangements of type $A_2$

2016

We consider deformations of the Weyl arrangement of type $A_2$, which include the extended Shi and Catalan arrangements. These last ones are well-known to be free. We study their sheaves of logarithmic vector fields in all other cases, and show that they are Steiner bundles. Also, we determine explicitly their unstable lines. As a corollary, some counter-examples to the shift isomorphism problem are given.

Substrate impact on the thickness dependence of vibrational and optical properties of large area $MoS_2$ produced by gold-assisted exfoliation

2021

The gold-assisted exfoliation is a very effective method to produce large-area ($cm^2$-scale) membranes of molybdenum disulfide ($MoS_2$) for electronics. However, the strong $MoS_2/Au$ interaction, beneficial for the exfoliation process, has a strong impact on the vibrational and light emission properties of $MoS_2$. Here, we report an atomic force microscopy (AFM), micro-Raman ($\mu-R$) and micro-Photoluminescence ($\mu-PL$) investigation of $MoS_2$ with variable thickness exfoliated on Au and subsequently transferred on an $Al_2O_3/Si$ substrate. The $E_{2g}$ - $A_{1g}$ vibrational modes separation $\Delta\mu$ (typically used to estimate $MoS_2$ thickness) exhibits an anomalous large val…

Respiration and low cAMP-dependent protein kinase activity are required for high-level expression of the peroxisomal thiolase gene in Saccharomyces c…

1996

Transcription of genes for peroxisomal proteins is repressed by glucose and induced by oleate. At least for the peroxisomal thiolase gene (POT1) there is a third regulatory mechanism, mediated by the transcription factor Adr1p, which is responsible for the high-level expression of the gene in stationary phase. Here we show that a region in the POT1 promoter that extends from positions -238 to -152 mediates this mechanism, and we suggest that Adr1p acts indirectly on POT1. We have also analyzed the role of the cAMP-dependent protein kinase (PKA) in the transcriptional regulation of POT1. PKA exerts a negative control: the high, unregulated PKA activity in a bcy1 mutant maintains POT1 transcr…

Adeguamento dello SPES2 per Prove di Sicurezza. Analisi Preliminari per La Simulazione di un Incidente Tipo Fukushima su SPES-2

2012

Direct Identification of Each Specific Mutation in Codon 12 and 13 of ci-ki-ras2 by SSCP Analysis

1998

We compared the SSCP behaviour of the DNA fragments containing c-ki-ras 2 wild type 12 and 13 codons or each of the 12 possible point mutated sequences in these two codons. We found that a single electrophoresis condition was sufficient to distinguish each specific mutation from the other 11 and from the wild type sequence. This observation makes it possible to identify each specific mutation directly by SSCP without any need for reamplification and sequencing.

Role of glycine-82 as a pivot point during the transition from the inactive to the active form of the yeast Ras2 protein

1991

AbstractRas proteins bind either GDP or GTP with high affinity. However, only the GTP-bound form of the yeast Ras2 protein is able to stimulate adenylyl cyclase. To identify amino acid residues that play a role in the conversion from the GDP-bound to the GTP-bound state of Ras proteins, we have searched for single amino acid substitutions that selectively affected the binding of one of the two nucleotides. We have found that the replacement of glycine-82 of the Ras2 protein by serine resulted in an increased rate of dissociation of Gpp(NH)p, a nonhydrolysable analog of GTP, while the GDP dissociation rate was not significantly modified. Glycine-82 resides in a region that is highly conserve…

Energetic aspects of intramolecular coupling between the nucleotide binding site and the distal switch II region of the yeast RAS2 protein

1994

AbstractWe have studied the interaction of the yeast RAS2 protein with guanine nucleotides using energetic parameters for the dissociation of RAS·nucleotide complexes. The results indicated that a Gly → Ser substitution at position 82 led to an altered interaction with GppNHp and, to a lesser extent, also with GDP. It was also possible to conclude that structural perturbation of Gly82 can stimulate nucleotide release by decreasing the energetic barrier for nucleotide dissociation. This, together with the observation that residues 80 and 81 are involved in the response of RAS to nucleotide exchange factors without affecting GDP binding per se, suggests a potential mechanism for exchange fact…

Phosphorylation of an Overexpressed Yeast Ras2 Protein During the G1 Phase of the Cell Cycle

1994

RAS proteins regulate growth and differentiation in evolutionarily distant systems such as vertebrates and yeast (for reviews, see Tamanoi, 1988; Gibbs and Marshall, 1989; Broach and Deschenes, 1990). At the moleular level, a key function of the yeast RAS1 and RAS2 proteins (collectively referred to as RAS) is to positively regulate the production of cyclic AMP at the onset of the G1 phase of the cell cycle (Toda et al., 1985; De Vendittis et al., 1986). At this stage, RAS proteins are transiently activated by the noncovalent binding of a GTP molecule. Reversal of the effect occurs by the hydrolytic splitting of the ’γ-phosphate of GTP, that leaves a functionally inactive RASGDP complex, th…

Genetic polymorphism of the bitter taste TAS2R38 gene in central Sicily

2007

Bitter taste genetics and food preference in italian population

2010

Objective: To investigate the possible role of the polymorphic bitter taste gene, TAS2R38, known to be involved in the perception of the bitter synthetic chemical phenylthiocarbamide (PTC), in influencing food preference and body mass index(BMI). Methods: up to now more than 1500 university students (17-25 years old) at Catania, Cosenza, Rome, Palermo, Pisa, Parma, Chieti, Trento University have been enrolled in the study. DNA was extracted from saliva, and genotyped by TaqMan assay for the most frequent polymorphism (PAV/AVI) of TAS2R38 gene. A possible association between genotype and food preference was assessed by administering a detailed questionnaire for food preferences and life styl…