Time filter

Source Type

Pascal R.,Max Mousseron Institute of Biomolecules | Pross A.,Ben - Gurion University of the Negev
Journal of Systems Chemistry | Year: 2014

The conceptual divide separating the physical and biological sciences continues to challenge modern science. In this perspective it is proposed that the two sciences can be directly connected through the fundamental concept of stability. Physicochemical stability is shown to have a logical, rather than an empirical basis, and able to manifest itself in two distinct and often contrary ways, one thermodynamic, reflecting energetic considerations, and the other kinetic, reflecting time/persistence considerations. Each stability kind is shown to rest on a particular mathematical truism. Thermodynamic stability, the energetic expression, has a probabilistic/statistical basis due to Boltzmann, and leads to the Second Law of Thermodynamics. Dynamic kinetic stability (DKS), the time/persistence expression, is attributed to the stability associated with persistent replicating systems, and derives from the mathematics of exponential growth. The existence of two distinct stability kinds, each mathematically-based, leads to two distinct organizational forms of matter, animate and inanimate. That understanding offers insight into the reasons for the observation of just those two organizational forms, their different material characteristics, and provides a logical basis for understanding the nature of chemical and biological transformations, both within, and between, the two forms. © 2014 Pascal and Pross; licensee Chemistry Central Ltd. Source

Vert M.,Max Mousseron Institute of Biomolecules
Macromolecular Bioscience | Year: 2011

Man-made artificial organic polymers are among the more recent sources of materials used by humans. In medicine, they contribute to applications in surgery, dentistry and pharmacology. Nowadays, innovations in the field of therapeutic polymers rely on novel polymers for specific applications such as guided tissue regeneration, tissue engineering, drug delivery systems, gene transfection, etc. Introducing reactive chemical functions within or along polymer backbones is an attractive route to generate functional polymers for medicine. However, any candidate to effective application must fulfil a number of requirements, grouped under the terms biocompatibility and biofunctionality, to be of real interest and have a future for effective application. Whenever the application requires a therapeutic aid for a limited period of time to help natural healing, bioresorbability is to be taken into account on top of biocompatibility and biofunctionality. This contribution presents the case of "artificial biopolymers" and discusses the potential of some members of the family with respect to temporary therapeutic applications that require functional polymers. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Vautrin J.,Max Mousseron Institute of Biomolecules
Neurochemistry International | Year: 2010

The vesicular hypothesis originally introduced to explain the quantal nature of presynaptic neurotransmitter (NT) release has been initially confirmed by the presence of NT within presynaptic vesicles and by an exo-endocytotic traffic associated with intense synaptic activity. Since then, an increasing number of synaptic transmission properties cannot be readily incorporated into the now popular model in which each quantal NT packet is prepared in a vesicle and is released by diffusion across the synaptic cleft when this vesicle fuses transiently or definitively with the plasma membrane. Interestingly, presynaptic exocytosis exhibits the characteristics of the ubiquitous secretory pathway by which all eukaryotic cells interact with their immediate environment, not just externalizing soluble products, but principally delivering at particular location of the cell surface specific glycoconjugates constituting the extracellular matrix (ECM) that mediates intercellular adhesion, recognition and signaling. Recent studies point to the involvement of vesicular glycoproteins in fast transmission after their incorporation into the transsynaptic ECM, or synaptomatrix. The notion of synaptomatrix is presented as a multimolecular tight arrangement that is dynamically remodeled in a use-dependent fashion via PKC to support synaptic morpho-functional plasticity. The data reviewed suggests that the synaptomatrix controls in a Ca2+ entry-dependent manner the solubility of the NT in the cleft to support fast transmission. © 2010 Elsevier Ltd. Source

Tilly D.,CNRS Chemistry Institute of Rennes | Dayaker G.,Max Mousseron Institute of Biomolecules | Bachu P.,University of Queensland
Catalysis Science and Technology | Year: 2014

This review provides a perspective on C-H bond functionalization mediated by cobalt complexes used in either stoichiometric or catalytic amounts, without the contribution of any other transition metal, for organic synthesis applications. The competitive cost, availability and lower toxicity of cobalt compared to precious transition metals constitute valuable advantages of the methods. © the Partner Organisations 2014. Source

Pascal R.,Max Mousseron Institute of Biomolecules
Journal of Systems Chemistry | Year: 2012

Any living organism can be considered as a component of a dissipative process coupling an irreversible consumption of energy to the growth, reproduction and evolution of living things. Close interactions between metabolism and reproduction are thus required, which means that metabolism has two main functions. The first one, which is the most easily perceptible, corresponds to the synthesis of the components of living beings that are not found in the environment (anabolism). The second one, which is usually associated with the former, is the dissipative process coupling the consumption of energy to self-organization and reproduction and introducing irreversibility in the process. Considering the origin of life, the formation of at least some of the building blocks constituting a living organism can be envisaged in a close to equilibrium situation under reducing conditions (for instance in hydrothermal vents). However, coupling irreversibly self-organization with the dissipation of an energy flux implies far from equilibrium conditions that are shown in this work to raise quantitative requirements on the height of kinetic barriers protecting metabolites from a spontaneous evolution into deactivated species through a quantitative relationship with the time scale of the progress of the overall process and the absolute temperature. The thermodynamic potential of physical sources of energy capable of feeding the emergence of this capacity can be inferred, which leads to the identification of photochemistry at the wavelength of visible light or processes capable of generating activated species by heating transiently a chemical environment above several thousand Kelvin as the only processes capable of fulfilling this requirement. © 2012 Pascal; licensee Chemistry Central Ltd. Source

Discover hidden collaborations