1,721,016 research outputs found
AFM: a versatile tool in biophysics
No full textHere we review the applications of atomic force microscopy to the study of samples of biological origin. Emphasis is given to provide the reader with information on the broad range of different biophysical applications that, to date, such a technique can deal with. After recalling briefly the operating principles of an atomic force microscope, the broad field of bio-imaging applications is faced (DNA, DNA-protein interaction, proteins, lipid membranes, cells); thereafter, the use of the atomic force microscope to measure forces is introduced and force mapping on living cells is discussed. This section is followed by the description of the use of force curves in assessing single-molecule inter- and intramolecular interactions. A paragraph on the perspectives of the technique in biophysical applications concludes the paper. We hope that this review can help the reader in appreciating how atomic force microscopy contributes to the current explosive growth of nanobiosciences, where biology, chemistry and physics merge
Taylored Synthesis of nanocrystals of II-VI alloy semiconductors in Langmuir-Blodgett templates
No full textA Highly Selective, Biofunctional Surface for Molecule/Cell Sorting
No full textWe report in this paper an approach to the effective capture of IgM antibodies from antisera and solutions based on the formation of a carpet of molecules exposing thiols off a surface. Surfaces of different nature, such as OH-exposing (glass, SiO2, metal oxides, etc.) and noble metal ones (Au, Ag, etc.), have been first functionalized in the liquid phase by suitable chemistry [3-(mercaptopropyl)trimethoxysilane or 1,4-benzenedimethanethiol]. The resulting exposed SH moieties have been further used for binding anti-A, -B, and -D IgM molecules from goat sera via a thiol exchange reaction involving the J chain and other disulfide bonds present in the IgM molecular structure. Antibodies preserve their functional activity at the surface and appear to be able to bind specifically erythrocytes of the proper group in a fast and reliable way. These results can be generalized to the use of any kind of IgM antibody and can be valuable in surface biofunctionalization in the fields of biosensors and immunoassays
Nanocrystalline alloys of II-VI semiconductors from molecular multilayer templates
No full textWe present the synthesis and characterization of nanocrystalline II-VI semiconductors of mixed composition (CdSe/ZnSe, CdS) grown in fatty acid Langmuir-Schaefer multi-layer templates. The controlled production of i) homogeneous nanocrystalline CdxZn1-xSe alloys and ii) heterogeneous mixtures of different pure composition II-VI semiconductors such as CdSe and ZnSe provides, in addition to the size control, the parameter of the chemical composition for the fine tuning of the electronic properties. The samples are characterized by optical and quasi-resonance micro-Raman spectroscopy
DNA-templated photoinduced silver deposition
No full textWe are presenting a photography-derived methodology to achieve the photoreduction of Ag+−DNA complexes. λ-Phage DNA was first loaded with silver ions, then irradiated with UV light at 254 nm. The DNA bases acted as light sensitizers, promoting the in situ reduction of Ag+ and the formation of metallic silver clusters. Three different approaches will illustrate this procedure, and silver nanoparticle chains will be grown along a DNA template in a rapid and specific way
Nanoscale mechanical properties of lipid bilayers and their relevance in biomembrane organization and function
No full textThe mechanical properties of biological systems are emerging as fundamental in determining their functional activity. For example, cells continuously probe their environment by applying forces and, at the same time, are exposed to forces produced by the same environment. Also in biological membranes, the activity of membrane related proteins are affected by the overall mechanical properties of the hosting environment. Traditionally, the mesoscopic mechanical properties of lipid bilayers have been studied by micropipette aspiration techniques. In recent years, the possibility of probing mechanical properties of lipid bilayers at the nanoscale has been promoted by the force spectroscopy potentiality of Atomic Force Microscopes (AFM). By acquiring force-curves on supported lipid bilayers (SLBs) it is possible to probe the mechanical properties on a scale relevant to the interaction between membrane proteins and lipid bilayers and to monitor changes of these properties as a result of a changing environment. Here, we review a series of force spectroscopy experiments performed on SLBs with an emphasis on the functional consequences the measured mechanical properties can have on membrane proteins. We also discuss the force spectroscopy experiments on SLBs in the context of theories developed for dynamic force spectroscopy experiments with the aim to extract the kinetic and energetic description of the process of membrane rupture
SFM and SEM investigation of CdS layers from Langmuir-Blodgett film templates
No full textThe 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 mu m 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. (C) 1998 Elsevier Science S.A. All rights reserved
Tuning molecular orientation in protein films
No full textThe rational design of azurin metalloprotein assemblies suitable for biomolecular electronics application has been achieved by exploiting different surface chemical approaches for growing active protein layers on both metal and insulating surfaces. The formed layers, which have been tested extensively by scanning force microscopy (SFM), spectroscopic ellipsometry, X-ray photoelectron spectroscopy (XPS), and electrochemical measurements (cyclic and linear voltammetry (CV and LV)), consist of redox active molecules endowed with tuneable orientation according to the particular functional group exploited for surface immobilization. The peculiar molecular arrangement has turned out to be responsible for different transport properties in solid state hybrid electronic planar devices
Fine-Tuning Nanoparticle Size by Oligo(guanine)n Templated Synthesis of CdS: an AFM study
No full textWe are presenting a method for modulating the size of US nanoparticles by templating their formation with oligo(guanine)(n) oligomers where n varied from 5 to 20. The variation in template length resulted in observable changes in the size distribution of the US nanoparticles. Statistical analysis of AFM images showed a general trend whereby the US average height decreased for longer oligoG(n) and increased for shorter oligoG(n). Concomitantly, shorter oligoG(n). yielded more dispersed populations, while longer oligoGn gave less dispersed populations. This synthetic methodology could be extended to the synthesis of other nanoparticles and even to mixed-metal nanoparticles resulting in a powerful method for fine-tuning size-dependent properties
Phase-Transition-Induced protein redistribution in Lipid Bilayers
No full textWe report an atomic force microscopy study on the lateral spatial redistribution of an integral membraneprotein reconstituted in supported lipid bilayers (SLBs) subjected to a thermally induced phase transition.KcsA proteins were reconstituted in proteoliposomes of POPE/POPG (3:1, mol/mol), and SLBs, includingthe proteins, were then obtained by the vesicle fusion technique on mica. By decreasing the temperature, thelipid bilayer passed from a liquid disordered (ld) phase in which the proteins are homogeneously distributedto a coexistence of solid ordered (so) and ld domains with the proteins preferentially distributed in the lddomains. The inhomogeneous distribution eventually led to protein clustering. The obtained results are discussedin light of the role that the lipid/protein interaction can have in determining the function of integral membraneproteins
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