Papers by Ranieri Rolandi
18th Annual Intern. Conference of IEEE EMBS, 1996
Molecular monolayer structure investigations have been performed by Scanning Tunneling Microscopy... more Molecular monolayer structure investigations have been performed by Scanning Tunneling Microscopy (STM) on self-assembled systems made of dotriacontane, stearic acid, tetracosanoic acid and octadecylmercaptane adsorbed on graphite. High-resolution voltage-bias dependent STM images have been obtained and conditions for optimal image contrast are discussed. A correction procedure to minimize scanning-induced geometrical distortion has been successfully applied on dotriacontane and octadecylmercaptane images
Thin Solid Films, 1998
The morphology of ultrathin layers of CdS nanocrystals from cadmium arachidate Langmuir-Blodgett ... more The morphology of ultrathin layers of CdS nanocrystals from cadmium arachidate Langmuir-Blodgett (LB) film templates has been investigated by means of scanning force and scanning electron microscopies (SEM). Consistently with previous Brewster angle microscopy investigations, low resolution electron micrographs reveal a flat film surface characterized by steps due to the difference in the number of precursor layers. Scanning force microscopy (SFM) allows one to get information on the mesoscopic and atomic film structure. While in the range 1-10 mm the film appears to be formed by a series of flat platforms, often shaped like triangles and sometimes superorganized in larger needle-like structures, in the hundred nanometer scale an irregular granular structure appears. Finally, performing zooms onto flat platforms, the CdS hexagonal lattice appears, revealing a lattice periodicity of 0.42 nm, in agreement with the bulk value.
Nano Science and Technolgy
Amyloids are insoluble, thread-like protein aggregates which are associated with a number of seve... more Amyloids are insoluble, thread-like protein aggregates which are associated with a number of severe diseases. Different techniques currently employed to characterize the structural features of amyloids, such as optical methods, electron microscopy, X-ray diffraction, nuclear magnetic resonance and atomic force microscopy (AFM), are briefly described in the first part of this chapter. Among these techniques, AFM plays a relevant role, as it is capable of imaging samples in different environments without requiring particular preparation, such as staining or fixation procedures. It allows the different steps of the aggregation process to be followed, from early oligomers to fibrils, providing nanometric details of their morphology. AFM has been used to probe the effects of organic and inorganic surfaces on the aggregation process and the interaction of amyloid with model membranes. Finally we review how the statistical analysis of AFM images and force spectroscopy measurements can give quantitative information on mechanical properties of fibrils.
Ultramicroscopy, 2007
The morphological and mechanical properties of encapsulated yeast cells (Saccharomyces cerevisiae... more The morphological and mechanical properties of encapsulated yeast cells (Saccharomyces cerevisiae) have been investigated by atomic force microscopy (AFM). Single living cells have been coated through the alternate deposition of oppositely charged polyelectrolyte (PE) layers. The properties of cells coated by different numbers of PE layers and from PE solutions of different ionic strength have been investigated. AFM imaging indicates an increase in PE coating stability when decreasing the solution ionic strength. The Young's moduli of the different examined systems have been evaluated through a quantitative analysis of force-distance curves by using the Hertz-Sneddon model. The analysis indicates an increase in hybrid system stiffness when lowering the ionic strength of the PE solution. An evaluation of the viability of encapsulated cells was obtained by confocal laser scanning microscopy (CLSM) measurements. CLSM analysis indicates that cells preserve their subcellular structure and duplication capability after encapsulation. By coupling AFM and CLSM data, a correlation between local stiffness and duplication rate was obtained.
Amyloid-like fibrils have been obtained upon incubation of a diluted aqueous solution of cytochro... more Amyloid-like fibrils have been obtained upon incubation of a diluted aqueous solution of cytochrome c at neutral pH in the presence of gold nanoparticles. The interaction of the cytochrome c suspension, containing proteins in both the monomeric and fibrillar state, with the freshly cleaved highly ordered pyrolytic graphite (HOPG) surface results in a double process. First, it leads to a nanopatterning of the HOPG surface and, second, it promotes the self-aligning of cytochrome c protofilaments on the nanopatterned HOPG surface.
Thin Solid Films, 1996
Self-assembled multilayers of stearic acid were obtained by evaporating a drop of stearic acid di... more Self-assembled multilayers of stearic acid were obtained by evaporating a drop of stearic acid dissolved in organic solvent onto a cleaned glass slide. X-ray diffraction and scanning force microscopy (334) were used to determine the bulk structure and to study the surface at molecular level. In samples prepared from decane solution, at least two crystalline forms (A + C and B + C, but seldom A + B + C) coexist and the molecules at the surface appear arranged according to a two-dimensional non-centered rectangular lattice. After annealing of the samples at 80 "C (slightly above the melting point of stearic acid), the C-form exists singly: accordingly, the molecular arrangement at the surface reverts to an hexagonal pattern. A periodic buckling superstructure is also observed by SFM in non-annealed samples. Moreover, X-ray diffraction results indicate that recrystallization processes occur.
Synthetic Metals, 2003
In this paper we discuss the optical (absorption and photoluminescence) and solvatochromic proper... more In this paper we discuss the optical (absorption and photoluminescence) and solvatochromic properties of a newly synthesized alternating copolymer based on poly(3-alkylthiophene) structure. In this copolymer an unsubstituted thiophene ring is linked to a 3-alkyl-substituted thiophene, the two repeating units being alternated in the copolymer chains. Moreover, a bulky group, THP, with high steric hindrance has been introduced in the side chain. This copolymer, designed to preserve the backbone planarity of polythiophenes and to prevent a close packing arrangement through the non-regioregular insertion of the bulky substituted monomer, shows high PL quantum yield in the solid state and in solution aggregates. The electroluminescence of this copolymer is reported for a simple single layer device.
Superconductor Science and Technology, 1997
Abstract. High-Tc thick films of YBa2Cu3O7− δ (YBCO) were grown on Ag substrates by a cryoelectro... more Abstract. High-Tc thick films of YBa2Cu3O7− δ (YBCO) were grown on Ag substrates by a cryoelectrophoretic technique, ie deposited by electrophoresis in a cryogenic environment. The orienting effect is provided by the application of an external magnetic field of small intensity (120 G). After sintering, these films exhibited a superconducting transition at 92 K in the electrical resistivity. Oriented films show significantly enhanced critical current densities. A detailed study of the structural and morphological properties of the film surfaces was ...
Physical Review B, 2005
ABSTRACT The indentation of protein crystals by an atomic force microscope tip is studied by mole... more ABSTRACT The indentation of protein crystals by an atomic force microscope tip is studied by molecular-dynamics simulations. This work is inspired by our previously reported experimental results, showing the occurrence of force jumps in the contact region of force-distance curves measured on ferritin crystals. These jumps were interpreted as due to the removal of molecules from the surface. Here we perform simulations of the indentation of topmost crystal layers with different tip sizes; special attention is devoted to the case corresponding to the experimental conditions, in which the tip size is twice the size of the crystal molecules. Force-distance curves are calculated. These curves show a first clear jump in correspondence of the rupture of the first layer; this jump is associated to the removal of a few molecules from the surface. The jump height, the curve shape, and the emission mechanism of the molecules from the crystal depend strongly on the indentation point. In particular, the amplitude of tip jumps resulting from crystal layer breakage is found to have a multimodal distribution. These results are in agreement with the interpretation previously given to our experimental results.
Physica B: Condensed Matter, 2001
We have studied the effect of physiological amounts of myelin basic protein (MBP) on pure dimyris... more We have studied the effect of physiological amounts of myelin basic protein (MBP) on pure dimyristoyl l-α-phosphatidic acid (DMPA) vesicles using the elastic neutron scattering technique. Elastic scans have been performed in a wide temperature range (20–300K). In the lower temperature region the behaviour of the integrated elastic intensity was the typical one of harmonic systems. The analysis of the
Langmuir, 2002
Departmental sources Background: Hip fracture is common in elderly patients. However, few effecti... more Departmental sources Background: Hip fracture is common in elderly patients. However, few effective studies had linked cognitive impairment to patient clinical outcome. Material/Methods: A total of 244 elderly hip fracture patients were prospectively followed up for 12 months. At 30 days, 6 months, and 1 year after hip repair surgery, patients and/or primary caregivers were interviewed by phone by trained, blinded interviewers. Functional evaluation, from pre-injury through 1 year after the operation, was assessed using the Barthel Index. Results: Among 244 patients, 43 were diagnosed as having cognitive impairment (Mini-Mental State Examination score <24). Compared to those without cognitive impairment, the 30-day, 6-month, and 1-year mortalities in the impaired patients were significantly higher than that of the cognitively intact patients. Six months after hip repair surgery, the cognitively intact patients presented significantly higher activities of daily living (ADL) scores than the cognitively impaired patients, and only 38.5% of impaired patients returned to their pre-operation baseline levels afterwards. The ADL scores in the impaired patients were similar to the intact ones at 1 year after the operation. Conclusions: Although they had a higher risk of mortality in hip fracture, functional gain in the cognitively impaired patients was similar to that in the cognitively intact patients at 1-year follow-up.
Langmuir, 1995
... Rolandi, R.; Dante, S.; Maga, L.; Robello, M. Prog. Colloid Polym. Sci. 1991, 84, 273-274. ..... more ... Rolandi, R.; Dante, S.; Maga, L.; Robello, M. Prog. Colloid Polym. Sci. 1991, 84, 273-274. ... The correlation of the growth of the dark domains with the irradiation time and the shFinking of the film area (vide infra) identify the dark domains as a phase rich in polymeric molecules. ...
The Journal of Membrane Biology, 1983
The membrane of Caldariella acidophila, an extreme thermophilic archaebacterium, is characterized... more The membrane of Caldariella acidophila, an extreme thermophilic archaebacterium, is characterized by unusual bipolar complex lipids. They consist of two nonequivalent polar heads, linked by a C4o alkylic component. The molecular organization of these lipids in the plasma membrane is still a matter of study. In this paper, we present current-voltage measurements on artificial bipolar lipid membranes, indicating that molecules are indeed organized as a covalently bound bilayer, in which each molecule is completely stretched and spans its entire thickness. Furthermore, conformational transitions of these artificial membranes (which could be formed only above 70 ~ C from a lipid/squalene dispersion) are analyzed in the 80 to 15~ temperature range. Abrupt variations in capacitance and valinomycin-induced conductance seem to indicate the occurrence of at least two structural changes. Measurements are also extended to different solvent systems. Results are consistent with the picture of a monolayer bipolar lipid membrane in which few solvent molecules align themselves parallel to the lipophilic chains. The amount of solvent as well as the temperature at which conformational transitions occur, depend on the solvent system in which the lipid is dispersed.
Journal of Biological Chemistry, 2013
Background: We recently discovered the first natural human  2-microglobulin variant, D76N, as an... more Background: We recently discovered the first natural human  2-microglobulin variant, D76N, as an amyloidogenic protein. Results: Fluid flow on hydrophobic surfaces triggers its amyloid fibrillogenesis. The ␣-crystallin chaperone inhibits variantmediated co-aggregation of wild type  2-microglobulin. Conclusion: These mechanisms likely reflect in vivo amyloidogenesis by globular proteins in general. Significance: Our results elucidate the molecular pathophysiology of amyloid deposition. Systemic amyloidosis is a fatal disease caused by misfolding of native globular proteins, which then aggregate extracellularly as insoluble fibrils, damaging the structure and function of affected organs. The formation of amyloid fibrils in vivo is poorly understood. We recently identified the first naturally occurring structural variant, D76N, of human  2-microglobulin ( 2 m), the ubiquitous light chain of class I major histocompatibility antigens, as the amyloid fibril protein in a family with a new phenotype of late onset fatal hereditary systemic amyloidosis. Here we show that, uniquely, D76N  2 m readily forms amyloid fibrils in vitro under physiological extracellular conditions. The globular native fold transition to the fibrillar state is primed by exposure to a hydrophobic-hydrophilic interface under physiological intensity shear flow. Wild type  2 m is recruited by the variant into amyloid fibrils in vitro but is absent from amyloid deposited in vivo. This may be because, as we show here, such recruitment is inhibited by chaperone activity. Our results suggest general mechanistic principles of in vivo amyloid fibrillo-genesis by globular proteins, a previously obscure process. Elucidation of this crucial causative event in clinical amyloidosis should also help to explain the hitherto mysterious timing and location of amyloid deposition.
Journal of molecular biology, 2004
Much information has appeared in the last few years on the low resolution structure of amyloid fi... more Much information has appeared in the last few years on the low resolution structure of amyloid fibrils and on their non-fibrillar precursors formed by a number of proteins and peptides associated with amyloid diseases. The fine structure and the dynamics of the process leading misfolded molecules to aggregate into amyloid assemblies are far from being fully understood. Evidence has been provided in the last five years that protein aggregation and aggregate toxicity are rather generic processes, possibly affecting all polypeptide chains under suitable experimental conditions. This evidence extends the number of model proteins one can investigate to assess the molecular bases and general features of protein aggregation and aggregate toxicity. We have used tapping mode atomic force microscopy to investigate the morphological features of the pre-fibrillar aggregates and of the mature fibrils produced by the aggregation of the hydrogenase maturation factor HypF N-terminal domain (HypF-N)...
European Biophysics Journal, 2001
Tapping mode atomic force microscopy was employed to study the surface structure of dierent prote... more Tapping mode atomic force microscopy was employed to study the surface structure of dierent protein crystals in a liquid environment. The (101) face of hen egg-white lysozyme crystals and the (111) face of horse spleen ferritin crystals were studied. On the (101) face of lysozyme crystals we observed islands delimitated by micro-steps and elongated in the [010] direction. The elongation direction coincides with the preferential growth direction predicted by a growth model reported in the literature. The islands observed on the ferritin (111) face are also delimitated by micro-steps but have circular symmetry. Sectioning of the images allowed us to measure the step heights. The surface free energy was estimated from the growth step morphology. Molecular resolution was achieved for ferritin crystals, showing a hexagonal surface packing, as expected for the molecular lattice of a (111) face in a fcc crystal. Keywords Atomic force microscopy á Protein crystals á Crystal growth á Ferritin á Lysozyme
Chemistry and Physics of Lipids, 2009
Investigating the pathways leading to the formation of amyloid protein aggregates and the mechani... more Investigating the pathways leading to the formation of amyloid protein aggregates and the mechanism of their cytotoxicity is fundamental for a deeper understanding of a broad range of human diseases. Increasing evidence indicates that early aggregates are responsible for the cytotoxic effects. This paper addresses the catalytic role of lipid surfaces in promoting aggregation of amyloid proteins and the permeability changes that these aggregates induce on lipid membranes. Effects of amyloid aggregates on model systems such as monolayers, vesicles, liposomes and supported lipid bilayers are reviewed. In particular, the relevance of atomic force microscopy in detecting both kinetics of amyloid formation and amyloid-membrane interactions is emphasized.
Biophysical Journal, 2010
We used tapping mode atomic force microscopy to study the morphology of the amyloid protofibrils ... more We used tapping mode atomic force microscopy to study the morphology of the amyloid protofibrils formed at fixed conditions (low pH with high ionic strength) by self-assembly of the N-terminal domain of the hydrogenase maturation factor HypF. Although all protofibrils in the sample share a beaded structure and similar values of height and width, an accurate analysis of contour length and end-to-end distance and the comparison of experimental data with theoretical predictions based on the worm-like chain model show that two different populations of protofibrils are present. These populations are characterized by different physical properties, such as persistence length, bending rigidity and Young's modulus. Fluorescence quenching measurements on earlier globular intermediates provide an independent evidence of the existence of different populations. The finding that differences in mechanical properties exist even within the same sample of protofibrils indicates the presence of different subpopulations of prefibrillar aggregates with potentially diverse tendencies to react with undesired molecular targets. This study describes a strategy to discriminate between such different subpopulations that are otherwise difficult to identify with conventional analyses.
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Papers by Ranieri Rolandi