1,432 research outputs found
Come saremo. Storie di umanità tecnologicamente modificata
No full textCambiamento climatico. Instabilità finanziaria. Migrazioni. Disuguaglianze. Accelerazione digitale e lentezza politica. Le grandi trasformazioni di oggi irrompono nel dibattito di ogni giorno con le loro imprevedibilità e il loro fascino. Ma perché è tanto importante discutere di futuro e di innovazione? Cosa possiamo fare dinanzi fronte alle sfide mai affrontate prima da Homo sapiens? In questo scenario, “Come saremo” non offre previsioni ma un metodo per guardare avanti consapevolmente, con la sola certezza che possiamo coltivare: il futuro sta tutto nelle conseguenze delle nostre azioni. La sintesi inedita delle voci di De Biase e Pievani indaga le tendenze dell’evoluzione tecnologica e le sue narrazioni mediatiche, e converge su una domanda: abbiamo la possibilità di influire sulla sua direzione? Chiude il volume una serie di testimonianze (economisti, esperti di comunicazione, ingegneri-hacker, architetti e filosofi del linguaggio) su cosa significa oggi creare e diffondere una cultura dell’innovazione
La investigación en la Universidad de Buenos Aires : su organización, la Facultad de Derecho y el Instituto de Investigaciones "Ambrosio L. Gioja"
No full textFil: Di Biase, Nicolás. Universidad de Buenos Aires. Facultad de Derecho. Buenos Aires, Argentin
The role of an active site aspartate residue in the catalytic activity of Glutamate decarboxylase from Escherichia coli.
No full textThe EMBO Conference focuses on fundamental and applied aspects of biocatalysis, with an emphasis on the impact that enzyme research has at the interface of biology and chemistry. The sessions will cover an array of topics including computational, chemistry and structural approaches, as well as directed evolution, bioinformatics and spectroscopic methods, aimed towards better understanding of enzyme mechanisms and mechanisms of complex multifunctional enzyme systems, in vitro and in vivo. The importance of the electrostatic and dynamical properties of enzymes will be addressed. The impact of this knowledge for drug discovery research and research on non-natural biocatalytic systems will be highlighted. Established and emerging scientists from academic and industrial settings will be available to stimulate discussion and provide perspective on the topics of this conference. We strongly encourage participation of students and postdoctoral associates, providing opportunities for discussion and networking. Oral presentations chosen from submitted poster abstracts will provide additional opportunities for discussing new and innovative ideas. The speakers are encouraged to give a brief introduction of the field in which they work and allow for sufficient time for discussion.Escherichia coli glutamate decarboxylase is a homohexameric PLP-dependent enzyme and a major structural component of the glutamate-based acid resistance system in this microorganism as well as in many orally-acquired, neutralophilic bacteria [1,2]. In fact the decarboxylation of L-glutamate, besides yielding γ-aminobutyrate (GABA) and CO2, consumes 1 H+/catalytic cycle, an activity shown to be beneficial for protecting the cell under extreme acid stress [1]. We have extensively characterized one of the two E. coli isoforms, the B isoform (EcGadB) and shown that it displays pH-dependency in activity in the acid range, being maximally active at pH 4-5 while showing negligible or no activity at or above pH 6.5. Based on the crystal structures of EcGadB at neutral and acidic pH, as well as in the presence of halides, and of a mutant form deleted at the N-terminal, we hypothesize that together with His465 (the penultimate residues in the amino acid sequence), Asp86 is a likely candidate for controlling the acidic range of activity of EcGad [3,4]. Notably, both residues are highly conserved in bacterial Gad [1]. The contribution to EcGadB spectroscopic and catalytic properties by His465, a critical residue for controlling active site access, was previously investigated [5].
In the present work, we carried out detailed biochemical characterization of the EcGadB-Asp86 mutant. However, in order to appreciate the contribution of Asp86 to the catalytic properties of EcGadB, it was necessary to incorporate the mutation Asp86→Asn in the mutant GadB_H465A, thereby avoiding the masking effect of His465 at pH>5.5. Our data show that, unlike wild-type EcGadB and GadB_H465A, the double mutant GadB_D86N¬-H465A, while retaining substrate specificity, is a more robust catalyst in the pH range 7-8 and displays an altered solvent kinetic isotope effect. Hence, GadB_D86N¬-H465A is less sensitive to pH increase during the decarboxylation reaction.
We proposed that immobilization of EcGadB can be exploited for GABA synthesis at the industrial level [6]. GABA in turn can be used as precursor of 2-pyrrolidone, an industrial solvent, and of nylon 4. Thus mutant forms of EcGadB less sensitive to pH increase (i.e. > 5.5) are highly desirable. Based on our data, pH is no longer a limiting reaction parameter for GadB_D86N¬-H465A.
References
[1] De Biase D, Pennacchietti E. (2012) Mol. Microbiol 86: 770-86.
[2] Lund P, Tramonti A, De Biase D. (2014) FEMS Microbiol Rev 38: 1091–125.
[3] Capitani G, De Biase D, et al. (2003) EMBO J. 22: 4027-4037.
[4] Gut H, Pennacchietti E, et al. (2006) EMBO J. 25: 2643-2651.
[5] Pennacchietti E, Lammens TM, et al. (2009) J Biol Chem. 284: 31587-96.
[6] Lammens TM, De Biase D, et al. (2009) Green Chemistry 11: 1562-67
Applicazione di clorexidina digluconata e clorexidina diidroclorica (Chlo-Site-Ghimas) nel trattamento delle parodontiti
No full textBiochemical characterization of Glutamate decarboxylase from Mycobacterium tuberculosis
No full textDuring the infectious process Mycobacterium tuberculosis typically encounters an acid stress in the human macrophage phago(lyso)some (pH 4.5-6.0) [1]. Nonetheless, how M. tuberculosis survives this challenge is little understood.
We have characterized M. tuberculosis glutamate decarboxylase (MtGadB). GadB catalyzes the decarboxylation of L-glutamate to yield GABA, while consuming one H+/catalytic cycle. It is a key enzyme in the potent glutamate-dependent acid resistance system found in many neutralophilic bacteria [2]. So far the only role proposed for MtGadB is to fill the interrupted TCA cycle in M. tuberculosis [3]. However, the perfect conservation of all key residues known as “GAD signature” [2] suggests that MtGadB may also play a role in protecting M. tuberculosis from acid stress.
MtgadB was cloned into two different vectors, for expression with/without a His-tag. The best conditions for expression were screened by a rapid colorimetric assay. MtGadB was purified using either an ion exchange or an affinity chromatography. The oligomeric state was assessed by gel filtration chromatography. The pH-dependent activity and titration curves were compared with those of the E. coli and Brucella microti GadBs that we have characterized [4]. This study sets the basis to uncover the role of GadB in M. tuberculosis biology, and its potential as a “druggable” target.
[1] Vandal et al. (2009) J Bacteriol. 191:4714-4721. [2] De Biase and Pennacchietti (2012) Mol. Microbiol 86:770-786. [3] Tian et al. (2005) PNAS 102:10670-10675. [4] Grassini et al. (2015) FEBS Open Bio 5:209-18
O072. An uncommon case of sinusal arrest in Cluster Headache
No full textIt is well known how migraine attacks are strictly associated to abnormalities of cardiac rhythm. Aygun et al[1] have studied 30 patients during migraine attacks, observing abnormalities of rhythm (including sinus arrhythmia, atrial premature contraction and ventricular premature contraction), intervals greater than 0.2 seconds, corrected QT intervals greater than 0.44 seconds, T inversion and ST-segment abnormalities. However, the role of autonomic nervous system variations in migraine attack-related electrocardiographic changes remains uncertain. Moreover, in patients with migraine parasympathetic nervous system alterations were observed during normal daily activity in the headache-free period[2].
In July 2015, a 45-year-old man was referred to us for evaluation because of a recurrent migraine associated with bradycardia. He referred recurrent migraine attacks, frequently occurring at night and in the supine position. During the acute phases of the attacks he described bradycardia, and sometimes, thoracic oppression. Furthermore, our patient told us about a clinical history of panic attacks and renal colics with syncope.
He is currently taking topiramate and oxygen therapy at high doses (15 lt/min) during attacks.
In order to better understand the previous episodes of syncope and the phases of bradycardia occurrence during the pain attacks, we monitored his electrocardiogram for 24h.
During the 24h registration, he had three attacks of migraine preceded by warning signs, one of them at night time. Analyzing the ECG, we observed sinusal rhythm, medium CF 74 bpm (28-115 bpm), normal PR interval, rare supraventricular and ventricular premature contractions. In correspondence to the migraine attacks, we observed sinus bradycardia and sinus pauses with RR maximum interval of 5.5 seconds, sometimes with the occurrence of junctional rhythm, without loss of consciousness. Considering the results of this monitoring, we decided to implant a pace-maker.
This case demonstrates the importance of autonomic dysregulation in a patient with migraine, showing the need of further studies to better understand the phenomenon.
Written informed consent to publication was obtained from the patient(s)
Fano 3-folds from homogeneous vector bundles over Grassmannians
No full textWe rework the Mori–Mukai classification of Fano 3-folds, by describing each of the 105 families via biregular models as zero loci of general global sections of homogeneous vector bundles over products of Grassmannians
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