247 research outputs found
Interacção biomembranar : parâmetros que influenciam a ligação de dendrimeros, peptidos lipidados e carregados electricamente a biomembranas
No full textDissertação de mestrado em Biofísica em BionanossistemasTodas as células, unidade de vida, apresentam-se compartimentalizadas por uma
bicamada lipídica permitindo que numerosos processos ocorram á superfície dos
organelos por uma associação reversível de proteínas do citosol. Nestes processos simples
parâmetros físicos como, curvatura membranar e/ou densidade de carga poderão ser
importantes “inputs” para criar respostas temporais e espaciais.(Bigay & Antonny, 2012).
A maioria dos estudos encontram-se focados em parâmetros físico-quimicos das
biomoléculas como os maiores reguladores na interacção com membranas. Deste modo o
papel desempenhado pelas propriedades membranares não se encontram completamente
elucidados.
Neste projecto, eu irei investigar a um nível singular as propriedades físicas das
biomembranas e a sua directa influência na associação reversível com biomoléculas. Para
este efeito, eu irei utilizar biomoléculas com função definida e analisar o seu
comportamento quando importantes parâmetros associados as mesmas são manipulados.
De modo a obter estes objectivos, irei utilizar um ensaio “in-vitro”, onde lipossomas
fluorescentes individuais serão imobilizados numa superfície de vidro e visualizados
usando microscopia laser confocal.
Deste modo, eu planeei o uso de lipossomas singulares e monitorizar como os parâmetros
membranares afectam a ligação de três classes diferentes de moléculas: primeiramente um
péptido lipidado derivado da GTPase N-Ras (tN-Ras), para o estudo da forma da
membrana na ligação peptídica. Em segundo o dendrimero (PAMAM G6) para elucidar o
papel desempenhado pelas interacções hidrofóbicas e electroestáticas. Por último um
péptido derivado da proteína membranar myristoyled alanine-rich C kinase substrate
(MARCKS), para o estudo de como o pH de lipossomas individuais poderão regular o
recrutamento específico de péptidos altamente catiónicos.All cells, the unit of life, are compartmentalized by a lipid bilayer allowing numerous
molecular processes to occur at the surface of organelles through reversible association of
proteins from the cytosol. In these processes simple physical parameters such as
membrane curvature and/or charge density can be important inputs to create sharp
temporal and spatial responses.(Bigay & Antonny, 2012)
Most studies focus on the physicochemical parameters of the biomolecules as the major
regulators of the interaction with membranes. This means that the role played by
membrane properties are still not fully understood.
In this project, I will investigate at single level the physical properties of biomembranes
and their direct influence in the reversible association with biomolecules. For this, I will
be using biomolecules with defined function to analyze the behavior when important
parameters associated with biomembranes are manipulated. To accomplish these goals, I
will use an in vitro assay, where individual fluorescent liposomes are immobilized on a
glass surface and imaged using confocal microscopy.
Thus, I planned use of single liposomes and monitor parameters affecting the membrane
binding of three different classes of molecules: first lipidated peptide derived from the NGTPase
RAS (tN-RAS) for the study of the membrane shape in the peptide bond.
Secondly, a dendrimer (PAMAM G6), to elucidate the role of hydrophobic and
electrostatic interactions. Finally, a peptide derived from the membrane protein
myristoyled alanine-rich C kinase substrate (MARCKS), to study how the individual pH
of liposomes may regulate the recruitment of specific highly cationic peptide
The Language of Shape: Biological Reactions are Dramatically Affected by the Shape of Lipid Membranes
No full textOrganic Monolayers: characterization by AFM and their use for the patterned immobilization of vesicles
No full textOrganic monolayers : characterization by AFM and their use for the patterned immobilization of vesicles
No full textLCPP
Το νομικό καθεστώς της νηολόγησης πλοίων υπό Κ.Δ.Ν.Δ. και άρθρο 13 ν.δ. 2687/1953 (ελαττώματα, θεραπεία, διαγραφή, διπλή νηολόγηση)
No full textΜέσα στα πλαίσια της παρούσης εργασίας, προσεγγίζονται διαδοχικά η νομοθεσία της προστασίας κεφαλαίων εξωτερικού, τα πλοία τα οποία νηολογούνται ως κεφάλαια εξωτερικού και το καθεστώς της νηολόγησής τους, το καθεστώς της νηολόγησης των πλοίων κοινών διατάξεων, οι προϋποθέσεις της νηολόγησής τους, οι συνέπειες της έλλειψης αυτών και τυχόν τρόποι θεραπείας τους, ενώ επιπροσθέτως λαμβάνει χώρα μία σύγκριση των δύο αυτών κατηγοριών πλοίων όσον αφορά στις πράξεις που λαμβάνουν δημοσιότητα στα βιβλία νηολογίων ώστε να εντοπισθούν οι μεταξύ τους υφιστάμενες διαφορές. Στο ίδιο πλαίσιο, παρεμπιπτόντως, παρουσιάζονται τα ειδικά καθεστώτα νηολόγησης στην ελληνική νομοθεσία, τα οποία και αφορούν σε πλωτά ναυπηγήματα και προβλέπονται σε ειδικούς νόμους. Επιπλέον, παρουσιάζεται το θέμα της πιθανής διπλής νηολόγησης ενός πλοίου, όπως αυτό υπάρχει και δύναται να αντιμετωπισθεί δυνάμει του ελληνικού θεσμικού πλαισίου, με έμφαση στις ατέλειες του παρόντος θεσμικού πλαισίου και τα μειονεκτήματα αυτού. Με βάση το σύνολο των παραπάνω θεμάτων, παρουσιάζεται συνολικά και με μία κριτική προσέγγιση το ζήτημα των πλοίων τα οποία νηολογούνται ως κεφάλαια εξωτερικού, σε αντιδιαστολή με τα πλοία κοινών διατάξεων, ενώ εξετάζεται και η σχέση του εν λόγω θεσμικού πλαισίου με το δίκαιο της Ευρωπαϊκής Ένωσης. Και επί τη βάσει των παραπάνω, διατυπώνονται προτάσεις για τη βελτίωση όψεων του ισχύοντος θεσμικού πλαισίου.Within the frame of this dissertation, the legislation of the protection of the foreign capitals, the ships which are registered as foreign capitals and their registration regime, the legal regime of the ships which are registered under common provisions, along with the preconditions of their registration, the implications in cases where those preconditions are not met and the potential ways of treatment, are consecutively approached. Furthermore, there takes place a comparison between those two categories of ships, as far as the acts published at the respective register books are concerned, in order to identify the existing differences. In the same context, the special registration regimes which are related to the floating constructions and they are provided in special laws, are also presented. In addition, the issue of the ships' double registration is also examined, as it incurs and it can be possibly restored by the current Greek institutional framework, focusing upon its deficiencies and its shortcomings. Taking into consideration the aforementioned areas of interest, it is integrally and critically presented the issue of the ships which are registered as foreign capitals vis a vis the ships registered under common provisions, while it is also examined the relationship of the current institutional framework with the EU law. Based on the abovementioned deductions, suggestions are made aiming at the improvement of the existing institutional framework
Regulation of the mammalian-brain V-ATPase through ultraslow mode-switching
No full textVacuolar-type adenosine triphosphatases (V-ATPases)1–3 are electrogenic rotary mechanoenzymes structurally related to F-type ATP synthases4,5. They hydrolyse ATP to establish electrochemical proton gradients for a plethora of cellular processes1,3. In neurons, the loading of all neurotransmitters into synaptic vesicles is energized by about one V-ATPase molecule per synaptic vesicle6,7. To shed light on this bona fide single-molecule biological process, we investigated electrogenic proton-pumping by single mammalian-brain V-ATPases in single synaptic vesicles. Here we show that V-ATPases do not pump continuously in time, as suggested by observing the rotation of bacterial homologues8 and assuming strict ATP–proton coupling. Instead, they stochastically switch between three ultralong-lived modes: proton-pumping, inactive and proton-leaky. Notably, direct observation of pumping revealed that physiologically relevant concentrations of ATP do not regulate the intrinsic pumping rate. ATP regulates V-ATPase activity through the switching probability of the proton-pumping mode. By contrast, electrochemical proton gradients regulate the pumping rate and the switching of the pumping and inactive modes. A direct consequence of mode-switching is all-or-none stochastic fluctuations in the electrochemical gradient of synaptic vesicles that would be expected to introduce stochasticity in proton-driven secondary active loading of neurotransmitters and may thus have important implications for neurotransmission. This work reveals and emphasizes the mechanistic and biological importance of ultraslow mode-switching.</p
Subnanometer actuation of a tethered lipid bilayer monitored with fluorescence resonance energy transfer
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