Papers by Ranieri Rolandi
Molecular monolayer structure investigations by scanning tunneling microscopy
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
Structure analysis of Eledon cirrhosa by CLSM and SFM
18th Annual Intern. Conference of IEEE EMBS, 1996
Chitosan-based systems as drug delivery platforms for periodontal disease
Polarized Electroluminescence from Double-Layer LEDs with Active Film Formed by Two Perpendicularly Oriented Polymers
ACS Symposium Series, 2004
The aim of this work is to study the feasibility of a double layer device, where the two active m... more The aim of this work is to study the feasibility of a double layer device, where the two active materials are formed, respectively, by two oriented polymers, whose orientation direction is orthogonal, and which can emit simultaneously in different regions of the visible spectrum. We demonstrate that the anisotropy of the polymers is not lost when they are perpendicularly oriented, obtaining polarized light in a large spectral region, extending from the green to the red. The emitted light, observed through a polarizer, can be varied from green to red by simply rotating the polarization axis, obtaining polarized light of variable colour. This peculiar device design is particularly appealing as it can increase the versatility of organic LEDs providing polarized light with easily variable colour emission.
Materials Letters, 2018
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service... more This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Poly(styrene-co-maleic anhydride) nanoparticles as protein carriers.
533—Structure and transport properties of artificial bipolar lipid membranes
Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, 1982
The membranes of thermophilic archaebacteria are characterized by the presence of unusual bipolar... more The membranes of thermophilic archaebacteria are characterized by the presence of unusual bipolar saturated isoprenoid lipids. In order to investigate their molecular arrangement in the membrane and a possible influence on transport properties, we studied black films made from lipids of Caldariella acidophila, one of the most thermophilic archaebacteria. Details on the kinetics of formation at various temperatures are presented. Capacitance, compressibility and valinomycin-induced conductance values are compared with the corresponding data for a glycerol-monooleate (GMO) bilayer. A very peculiar behavior is presented by the bipolar lipid films studied. In fact, the values of conductance are more than two orders of magnitude lower than those of a GMO bilayer, while the values of capacitance and compressibility do not depend appreciably on the solvent in which the lipid is dispersed (in contrast with a GMO bilayer, where there is a 100% change). The results are discussed in terms of a proposed model of a monolayer organization of bipolar lipids and of the unusual composition of the hydrophobic core of the membrane. \ua9 1982
Journal of The Royal Society Interface, 2013
Marine biofouling causes problems for technologies based on the sea, including ships, power plant... more Marine biofouling causes problems for technologies based on the sea, including ships, power plants and marine sensors. Several antifouling techniques have been applied to marine sensors, but most of these methodologies are environmentally unfriendly or ineffective. Bioinspiration, seeking guidance from natural solutions, is a promising approach to antifouling. Here, the eye of the green crab Carcinus maenas was regarded as a marine sensor model and its surface characterized by means of atomic force microscopy. Engineered surface micro- and nanotopography is a new mechanism found to limit biofouling, promising an effective solution with much reduced environmental impact. Besides giving a new insight into the morphology of C. maenas eye and its characterization, our study indicates that the eye surface probably has antifouling/fouling-release potential. Furthermore, the topographical features of the surface may influence the wettability properties of the structure and its interaction ...
Molecular dynamics simulations of the indentation of a crystalline surface by an atomic force microscope tip
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.
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.
Photovoltage generation in bilayer lipid membrane-cadmium sulfide junctions
The Journal of Physical Chemistry, 1992
ABSTRACT This paper discusses how the formation of CdS particulate films on black lipid membranes... more ABSTRACT This paper discusses how the formation of CdS particulate films on black lipid membranes (BLM) of glycerol monooleate is measured by membrane potential differences, capacitance, and solution pH variations. This suggests that HâS makes the BLM selectively permeable to protons that are responsible for the dark voltage. Other experiments are used to check the influence of dark potentials, gradients, and proton permeability of the photopotential, which yields a quantitative model to describe these kinetics, based on CdS electron/hole pair localization and interaction with HâS. 20 refs., 8 figs., 1 tab.
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.
Peroxidated olive oil nanoemulsion for cancer targeted therapy
2015 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2015
A reactive oxygen species-mediated targeting system has been used to selectively kill cancer cell... more A reactive oxygen species-mediated targeting system has been used to selectively kill cancer cells. Two different cell lines, normal and cancer cells, have been cultured and treated with a peroxide olive oil (K600) in simple solution and in form of nanoemulsion (N-K600). Preliminary results of both treatments have been compared.
CLSM and SFM imaging to investigate the structure of the sperm head of Eledone cirrhosa
Surface and Interface Analysis, 1994
Scanning force microscopy (SFM) inspection shows that stearic acid deposited on a glass slide by ... more Scanning force microscopy (SFM) inspection shows that stearic acid deposited on a glass slide by evaporation of an organic solvent forms a layered structure. Scanning force microscopy images covering areas of a few square micrometres show a stack of bimolecular layers. Molecular resolution images of the layer surface shows ordered hexagonal patterns extending over areas as large as several unit cells. An accurate analysis of several images based on the evaluation of the Fourier transform made it possible to measure the unit mesh1 constant of the surface lattice with an accuracy of 1%. After samples are annealed slightly above melting temperature, the unit mesh constant decreases significantly, indicating a more compact arrangement of the molecules.
Physica C: Superconductivity, 1997
We deposit thin epitaxial YBaCu203 films on SrTi03 (100) substrates by pulsed laser deposition us... more We deposit thin epitaxial YBaCu203 films on SrTi03 (100) substrates by pulsed laser deposition using a pulsed molecular oxygen flow. We study the oxygen pressure dependence of their growth and their surface morphology by means of reflection high energy electron diffraction (RHEED) and atomic force microscope (AFM). A new method to improve the oxygen reactivity is also proposed.
Experientia, 1995
The Atomic Force Microscope (AFM) was used to inspect collagen fibrils deposited on mica sheets a... more The Atomic Force Microscope (AFM) was used to inspect collagen fibrils deposited on mica sheets at different fibrillogenesis times. Collagen was obtained from rat tail tendon fibers. Various fibril forms were observed, together with the characteristic periodic intra-fibril structure (D-bands). The fibril thickness, width, D-band periodicity and depth were measured and the statistical distribution of these parameters at t, 2, 5, 10 and 15 days of in vitro fibril formation time was calculated. The fibrils showed an increasing size with time, but the band interval measure remained stable. The band depth, after an initial increase, exhibited a relative steadiness. The results indicate that AFM offers, at low resolution, images qualitatively similar to those obtained With electron microscopy, but with less manipulation of the sample. A quantitative evaluation of collagen structural features in the nanometer scale is made possible by AFM.
Ultrahigh Vacuum Deposition of l -Cysteine on Au(110) Studied by High-Resolution X-ray Photoemission: From Early Stages of Adsorption to Molecular Organization
The Journal of Physical Chemistry B, 2005
We report on a high-resolution X-ray photoemission spectroscopy study on molecular-thick layers o... more We report on a high-resolution X-ray photoemission spectroscopy study on molecular-thick layers of L-cysteine deposited under ultrahigh vacuum conditions on Au(110). The analysis of core level shifts allowed us to distinguish unambiguously the states of the first-layer molecules from those of molecules belonging to the second layer. The first-layer molecules strongly interact with the metal through their sulfur headgroup. The multipeaked structure of the N 1s, O 1s, and C 1s core levels is interpreted in terms of different molecular moieties. The neutral acidic fraction (HSCH2CH(NH2)COOH) is abundant at low coverage likely associated with isolated molecules or dimers. The zwitterionic phase (HSCH2CH(NH3+)COO-) is largely dominant as the coverage approaches the monolayer limit and is related to the formation of ordered self-assembled molecular structures indicated by electron diffraction patterns. The occurrence of a small amount of cationic molecules (HSCH2CH(NH3+)COOH) is also discussed. The second-layer molecules mainly display zwitterionic character and are weakly adsorbed. Mild annealing up to 100 degrees C leads to the desorption of the second-layer molecules leaving electronic states of the first layer unaltered.
The two-fold aspect of the interplay of amyloidogenic proteins with lipid membranes
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.
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.
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Papers by Ranieri Rolandi