download report - Sapienza
download report - Sapienza
download report - Sapienza
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Scientific Report 2007-2009<br />
Condensed matter physics and biophysics<br />
sized particles to generate materials (and bio-materials) with controlled physical properties.<br />
One of the model system investigated in Rome is made of interacting colloidal particles and<br />
oppositely charged polymers. These systems have recently attracted great interest, due to their<br />
relevance in a number of biological and technological processes, but even more to the fact that their<br />
dynamics and out-of-equilibrium properties offer unceasing challenges. These complexes show a<br />
rich and fascinating phenomenology yet poorly understood. Various novel core-particle aggregates<br />
have been prepared in Rome, by electrostatic self-assembly of polyelectrolytes (and nano particles)<br />
with oppositely charged lipid liposomes. The use of non-covalent forces provides an efficient<br />
method to position the polyelectrolyte chainin a well-defined supra-molecular architecture. In<br />
addition, it is possible to control the macroscopic properties of the assembly through an external<br />
environmental stimulus (C23,C24). We also investigate the interactions between biopolymers<br />
(proteins or nucleic acids) and self-assembled surfactants, a system which has raised increasing<br />
interest within the scientific community. Studies along these lines constitute an interdisciplinary<br />
approach of chemical/physical nature at the bio-molecular level. In addition these investigations<br />
contribute to important applications in biomedicine, as gene therapy. Our research focuses on<br />
a new class of self-assembled amphiphilic aggregates, called cat-anionic vesicles. The acronym<br />
cat-anionic defines surfactant aggregates formed by non-stoichiometric amounts of anionic and<br />
cationic surfactants coexisting with tiny amounts of simple electrolytes (C25).<br />
We also investigate solid-supported lipid-films, considered as an attractive and useful model<br />
system for biological membranes. In particular, amphipathic lipid films on solid support allow the<br />
study of structural investigation of important biological model systems such as the vector like lipid<br />
membranes, in order to improve DNA transfection in non viral gene therapy and as a template<br />
for nanostructure construction (C26).<br />
Structural properties of proteins are also carefully investigated with spectroscopic methods with<br />
the aim of connecting structural changes with the ability to catalyze specific chemical reactions<br />
or the relationship between structural properties of proteins of nutritional relevance, as examined<br />
by FT-IR spectroscopy, and nutrient utilization (C27). Using femtosecond stimulated Raman<br />
scattering spectroscopy (FSRS) we study the reaction of heme proteins with different biological<br />
functions (electron transfer , signaling, etc.). FSRS provides vibrational structural information<br />
with an unprecedented combination of temporal and spectral resolution, unconstrained by the<br />
Fourier uncertainty principle, i.e. in the < 100 fs time domain, unaccessible to conventional<br />
vibrational spectroscopy (C28). We also investigate via small angle X-ray scattering (SAXS), mass<br />
spectroscopy and light scattering techniques different proteins. In particular, we have recently<br />
investigated the protein ferritin , the main iron storage protein in living systems and τ-protein,<br />
one of the few proteins without a secondary structure. Ferritin is a stable complex forming an<br />
hollow sphere (apoferritin) filled with a Fe(II) oxide core and it is important to study since the<br />
ferritin core composition differs between pathological and physiological conditions. τ-protein is<br />
an interesting protein in which fluctuations are expected to be fast and to control the biological<br />
function (C29).<br />
Soft and bio matter is also investigated to address fundamental problems in condensed matter.<br />
Indeed, colloidal suspensions have unambiguous advantages with respect to their atomic counterparts.<br />
Characteristic space and time scales are much larger, allowing for experimental studies in<br />
the light scattering regime and for a better time resolution. The size of the particles allows for<br />
direct observation with confocal microscopy techniques, down to the level of single-particle resolution.<br />
In addition, particle-particle interactions can be tuned by changing the solution conditions<br />
or by additives, as well as by synthesis of functionalized colloids. Colloidal suspensions, despite<br />
being very complex in nature and number of components, can often be well described theoretically<br />
via simple effective potentials. A significant effort is devoted to the investigation of the phase diagram<br />
and self-assembly abilities of patchy colloidal particles, in a combined theoretical, numerical<br />
and experimental study (C9,C20).<br />
One powerful technique to investigate the motion and the interactions between colloidal particles<br />
<strong>Sapienza</strong> Università di Roma 50 Dipartimento di Fisica