We focus on the study of how the small volumes, the limited dimensions and the topology of the compartments in which biological reactions take place influence their kinetics and equilibrium.
Phone (+351) 214469724
At the Laboratory of Microheterogeneous Systems of ITQB we study the chemical equilibrium and the kinetics of bimolecular reactions in lipid mesophases. The lipid mesophases we are interested in are those that mimic cell structures such as the biological membrane or the cellular compartments. With synthetic lipid bilayers of selected composition to which we add hydrophobic or amphiphilic reactants we model reactions taking place in the biological membrane, and with submicron aqueous compartments delimited by aggregated lipids containing aquo-soluble reactants we simulate reactions in cell compartments or at soft interfaces.
It is expectable that the models that were developed for large three-dimensional spaces containing an “infinite” number of reactant molecules and for which the effect of the wall of the reaction vessel is negligible, fail when applied to reactions in biological systems. The speed of a bimolecular reaction is modified by the geometry in which the molecules are allowed to diffuse before encounter and by the number of reactant molecules available. The number of molecules in a compartment will modify the rate and the yield of the reaction.
In our Laboratory we simulate the environment in which biological reactions take place, and follow the progression of reactant conversion with time in the sub-millisecond time scale, the time in which many biological reactions occur.
The aggregates of lipids forming bilayers, or other molecular constructs with which we intend to work, need to be characterized before we begin to deal with them as microreactors. A large part of the Laboratory’s work is devoted to the study of the structure and topology of the lipid aggregates we use in our studies, or those that are of particular biological interest, namely those responsible for the creation of lipid inhomogeneity in the biological membranes.
- Rute Mesquita, PhD student
- Sofia de Souza, PhD student
- Helena Lameiro, PhD student
- S. L. Souza, M. J. Capitan, J. Alvarez, S. S. Funari, M. H. Lameiro, and E. Melo “Phase behavior of aqueous dispersions of mixtures of N-palmitoyl ceramide and cholesterol: A lipid system with ceramide-cholesterol crystalline lamellar phases” J. Phys. Chem. B, 113 (2009) 1367–1375
- E. Melo and J. Martins “Kinetics of bimolecular reactions in model bilayers and biological membranes. A critical review” Biophys. Chem., 123 (2006) 85- 02
For further information please visit the laboratory's website
As reacções que garantem o funcionamento das células e dos organismos a que pertencem dão-se no interior de compartimentos sub-microscópicos, ou na membrana que delimita a célula ou naquelas que a reticulam internamente. No Laboratório de Sistemas Micro-heterogéneos, estudamos a forma como a velocidade e o rendimento destas reacções são modificados devido a dois factores: a geometria do espaço em que se dão e o reduzido número de moléculas reagentes.
As membranas biológicas, por sua vez, têm composição muito variada, composição esta certamente relacionada com a sua função. Na maioria dos casos ainda é desconhecida esta relação e um dos temas de estudo no nosso Laboratório é a caracterização das membranas constituídas por lípidos específicos de determinadas estruturas. Por exemplo, estudamos a matriz lipídica do stratum corneum que protege os mamíferos do meio exterior, ou a formação de agregados lipídicos que concentram algumas proteínas na parede de organelos celulares.