Ageing of solid-state protein films: behavior of azurin at ambient conditions.

We report on the folding properties of the protein azurin, deposited onto SiO2 surfaces and subsequently dehydrated. The molecular films have been maintained at ambient conditions through several days, and the ageing effects have been investigated by fluorescence spectroscopy. The experimental results show a modest initial conformational rearrangement, followed by long-term stability. Interestingly, upon rehydration of the biomolecular films at the end of the investigated period (approximately one month), azurin returns to exhibit a native-like conformation. This study indicates a rather surprising resilience of proteins to ambient conditions and sheds a somewhat unexpected positive light on reliability in biomolecular electronics. (C) 2005 Elsevier B.V. All rights reserved

Charge transport in disordered films of non-redox proteins

Electrical conduction in solid state disordered multilayers of non-redox proteins is demonstrated by two-terminal transport experiments at the nanoscale and by scanning tunneling microscopy (STM/STS experiments). We also show that the conduction of the biomolecular films can be modulated by means of a gate field. These results may lead to the implementation of protein-based three-terminal nanodevices and open important new perspectives for a wide range of bioelectronic/biosensing applications

Transistore biomolecolare ad effetto di campo comprendente un film di polipeptidi, e procedimento per la sua realizzazione. (A BIOMOLECULAR FIELD EFFECT TRANSISTOR COMPRISING A POLYPEPTIDE FILM, AND A METHOD FOR ITS MANUFACTURING)

An organic field-effect transistor (T) is described, which comprises: a pair of source and drain electrode (S, D) which are formed on an electrically insulating layer (INS) and which are adapted to operate as the source and the collector of a flow of electric charge-carriers in which the majority carriers are free holes, and a layer of organic conductive material (F) which is disposed between the electrodes (S, D) for the formation of a conduction region through which the flow of charge carriers passes and the resistance of which is modulated by the application of a control voltage to a gate electrode (G) insulated from the conduction region, characterized in that the layer of organic conductive material (F) is a layer of biomolecular conductive material including a film of polypeptides or oligopeptides (P) .; The method for the manufacture of a transistor of this type comprises the formation of a film (F) of polypeptides or oligopeptides (P) on the electrically insulating layer (INS) in contact with the source and drain- electrodes (S, D) by immobilization of the polypeptides/oligopeptides (P) on the layer (INS) by deposition of a buffer solution of polypeptides/oligopeptides (P) , subsequent incubation for a predetermined period of time and at a predetermined temperature, removal of the buffer solution, and drying by exposure to a stream of gas

Fluorescence enhancement in colloidal semiconductor nanocrystals by metallic nanopatterns

In this work we demonstrate the possibility of obtaining a significant increase of the photoluminescence of colloidal semiconductor nanocrystals (NCs) by means of metallic nanopatterns. Highly ordered triangular-shaped gold nanopatterns (typical dimensions 200 nm) were fabricated on planar substrates by electron beam lithography (EBL). Colloidal semiconductor nanocrystals (core/shell CdSe/ZnS quantum dots or CdSe nanorods) dispersed in a polymer matrix (PMMA) were subsequently deposited on the substrates by spin-coating. The coupling between the surface plasmons (SPs) resonance band of the metallic nanostructures and the excitation/emission bands of the nanocrystals resulted in a strong enhancement of the fluorescence from the quantum emitters, as probed by confocal microscopy analyses. Importantly, the proposed approach allows a precise control of the shape and dimensions of the single metallic nanostructure (and consequently of the SPs resonances), thanks to the nanometer resolution of the EBL. Moreover, the concentration of the NCs dispersed in the blend, as well as the thickness of the active layer, can be finely tuned. These results may open interesting perspectives for a wide range of applications, such as photonic devices, LEDs, sensor technology, microarrays, single/few molecules experiments, and biochemical/biophysical investigations

Exploring Local Flexibility/Rigidity in Psychrophilic and Mesophilic Carbonic Anhydrases

Molecular flexibility and rigidity are required to determine the function and specificity of protein molecules. Some psychrophilic enzymes demonstrate a higher catalytic efficiency at low temperatures, compared to the efficiency demonstrated by their meso/thermophilic homologous. The emerging picture suggests that such enzymes have an improved flexibility of the structural catalytic components, whereas other protein regions far from functional sites may be even more rigid than those of their mesophilic counterparts. To gain a deeper insight in the analysis of the activity-flexibility/rigidity relationship in protein structure, psychrophilic carbonic anhydrase of the Antarctic teleost Chionodraco hamatus has been compared with carbonic anhydrase II of Bos taurus through fluorescence studies, three-dimensional modeling, and activity analyses. Data demonstrated that the cold-adapted enzyme exhibits an increased catalytic efficiency at low and moderate temperatures and, more interestingly, a local flexibility in the region that controls the correct folding of the catalytic architecture, as well as a rigidity in the hydrophobic core. The opposite result was observed in the mesophilic counterpart. These results suggest a clear relationship between the activity and the presence of flexible and rigid protein substructures that may be useful in rational molecular and drug design of a class of enzymes playing a key role in pathologic processes