Azurin is a blue single copper protein involved in the respiratory chain of denitrifying bacteria. The structural gene for azurin from Pseudomonas aeruginosa was cloned in an Escherichia coli recombinant strain. The protein overexpressed in the bacterial periplasmic space was subsequently purified. Two strategies were followed to anchor azurin to gold surfaces. First, the protein was immobilised on bare gold. Azurin adsorbs on gold via its disulfide group. Scanning tunnelling microscopy (STM) inspection of the azurin-Au(111) interface revealed the formation of a closely packed protein monolayer and allowed individual azurin molecules to be resolved. In order to uncouple the protein layer from the metal, the gold surfaces were then covered with self-assembled monolayers of 11-mercaptoundecanoic acid. The changes in the sample morphology due to the protein adsorption have been investigated by atomic force microscopy (AFM). A fairly uniform distribution of protein molecules covers the surface. Owing to the tip broadening effect, an average protein diameter of about 20 nm was measured. An upper limit of 1 nN for the non-disruptive imaging force in the contact mode was found

Rate constants for the title reaction have been measured in both forward and reverse directions leading to rates and equilibrium constants for all the steps in equation (i). The effects of varying the structures of A r A r -0 -C S -N H A r ' e A r -0 -C C N -A r ' s Ar-0- ExperimentalMateriafs.-0-4-Methoxyphenyl chlorothioformate was prepared by adding a solution of 4-methoxyphenol (8.3 g, 67 mmol) in 5% NaOH (60 ml) dropwise to a well stirred, cooled solution of thiophosgene (7.7 g, 67 mmol) in chloroform (40 ml). The reaction was stirred for 1 h at 0-5" and the chloroform layer washed with dilute HCl and water. The chloroform solution was dried with sodium sulphate, evaporated, and the residue distilled to yield a liquid, b.p. 92" at 0.5 Torr (lit.,3h 141-143" at 13 Torr), which solidified on cooling.0-4-Met hoxyphenyl N-arylthioncarbamates were prepared by adding the aniline (32 mmol) dissolved in carbon tetrachloride (5 ml) to a stirred, cooled solution of O-(Cmethoxyphenyl) chlorothioformate (3.3 g, 10 mmol) in carbon tetrachloride (50 ml). The mixture was stirred at room temperature for 24 h, filtered, and the filtrate evaporated to dryness. The thioncarbamate was recrystallised from a suitable solvent (see Table 1).Aryl isothiocyanates were prepared by adding a slight excess of thiophosgene to a mechanically stirred mixture of the appropriate aniline and water. Reaction was almost instantaneous and the isothiocyanate separated as an oil and was extracted with ether. The ether was dried (Na,SO,), evaporated, and the residual oil distilled under high vacuum. The materials prepared above had satisfactory analyses (Table 1) and their structures were confirmed by i.r. (Perkin-Elmer 297 instrument) and 100 MHz 'H n.m.r. spectra. The latter spectra were recorded by Dr. D. 0. Smith using a JEOL instrument, Buffers and reagents used in the kinetics were of analytical quality or were recrystallised or redistilled from bench grade materials. Water used throughout the investigation was distilled twice from glass.Method;F.-Kinetics were followed spectrophotometrically at an. appropriate wavelength determined using a repetitive wavelength scanning spectrophotometer (Unicam SP 800). Constant wavelength studies were carried out using a Unicam SP 800 machine or a Beckman D.B. instrument fitted with Servoscribe potentiometric recorders. The stock solution of substrate (thioncarbamate or isothiocyanate) in ethanol or

Recently new molecular systems based on the pyrene moiety were developed for photovoltaic applications. Here we present the results of a quantum chemical study focused on the effects induced by some different substituents on the electronic properties of pyrene, to obtain general hints for the molecular design of new pyrene-based systems. In particular, a series of electron-donating (hydroxy, amino, acetylamino) and electron-withdrawing (cyano, carbamoyl, formyl, ethynyl, ethenyl) groups were considered. Furthermore, in addition to the single pyrene molecule, two pyrene units linked by ethenylene, ethynylene, 2,5-thienylene, and ethynylene-p-phenylene containing chains of different lengths were taken into account. For all of the model structures presented, the ground state geometries have been optimized using the density functional approach, while the vertical transition energies were calculated using the time-dependent density functional theory. We will show that the tuning of the lowest electronic excitation energy (i.e., the HOMO-LUMO energy gap) as well as the localization of the spatial distributions of the frontier molecular orbitals (i.e., the nature of the electron-hole pair, generated by photon absorption) can be obtained through the analysis of the pyrene frontier molecular orbitals. This approach allows to evaluate the most suitable position of the substituents on the pyrene moiety giving rise to enhanced electronic effects also in function of their electronic nature. In this way, pyrene-structures with tailored electronic properties could be modeled. Our screening shows that promising candidates for photovoltaic applications could be molecular structures formed by two pyrene units joined/linked by a short conjugated bridge containing double or triple bonds (henceforth pyrene-linked dimers). As far as the single pyrene units are considered, the most significant reduction of the transition energy of the lowest optical electronic excitation is obtained with disubstituted pyrenes with push-pull character.

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This paper reports on the fabrication of self-assembled monolayers containing disulfide-functionalized diacetylenes. To this purpose, two diacetylene derivatives were synthesized:  the novel 14-(9H-9-carbazolyl)tetradeca-10,12-diyn-1-yl disulfide (CDS9) and the henicosa-10,12-diyn-1-yl disulfide (DS9). Both monomers were employed to prepare two-dimensional self-assembled monolayers (2D-SAMs) by chemisorption on gold-sputtered platforms and three-dimensional self-assembled monolayers (3D-SAMs) on gold nanoclusters by direct synthesis in organic solvent. The chemisorbed diacetylenes were then converted to the polymeric form by exposure to UV radiation, and their morphological and spectroscopic properties investigated by several techniques. From SERS data it was inferred that both monomers show the same behavior, in that the highly conjugated blue phase was observed in the 3D-SAMs, while only the less extended red conformation was found in the corresponding 2D-SAMs.