Nanohybrid Structures Based on Plasmonic or Fluorescent Nanoparticles and Retinal-Containing Proteins.

Rhodopsins are light-sensitive membrane proteins enabling transmembrane charge separation (proton pump) on absorption of a light quantum. Bacteriorhodopsin (BR) is a transmembrane protein from halophilic bacteria that belongs to the rhodopsin family. Potential applications of BR are considered so promising that the number of studies devoted to the use of BR itself, its mutant variants, as well as hybrid materials containing BR in various areas grows steadily. Formation of hybrid structures combining BR with nanoparticles is an essential step in promotion of BR-based devices. However, rapid progress, continuous emergence of new data, as well as challenges of analyzing the entire data require regular reviews of the achievements in this area. This review is devoted to the issues of formation of materials based on hybrids of BR with fluorescent semiconductor nanocrystals (quantum dots) and with noble metal (silver, gold) plasmonic nanoparticles. Recent data on formation of thin (mono-) and thick (multi-) layers from materials containing BR and BR/nanoparticle hybrids are presented.

Supramolecular nanostructures based on bacterial reaction center proteins and quantum dots.

Design of the nanostructures based on membrane proteins (the key functional elements of biomembranes) and colloid nanoparticles is a fascinating field at the interface of biochemistry and colloids, nanotechnology and biomedicine. The review discusses the main achievements in the field of ultrathin films prepared from bacterial reaction center proteins and light-harvesting complexes, as well as these complexes tagged with quantum dots. The principles of preparation of these thin films and their structure and properties at different interfaces are described; as well as their characteristics estimated using a combination of the modern interfacial techniques (absorption and fluorescence spectroscopy, atomic force and Brewster angle microscopy, etc.) are discussed. Further approaches to develop the nanostructures based on the membrane proteins and quantum dots are suggested. These supramolecular nanostructures are promising prototypes of the materials for photovoltaic, optoelectronic and biosensing applications.

Organization of butadienyl dyes containing benzodithiacrown-ether or dimethoxybenzene in monolayers at the air/aqueous salt solution interface.

Two amphiphilic butadienyl dyes 1 and 2 form stable monolayers at the air/water interface in the presence of various salts. Dye 1 consists of the basic amphiphilic butadienyl chromophore. In dye 2, the dimethoxybenzene part of dye 1 is substituted by benzodithia-15-crown-5. The monolayers have been characterized by surface pressure-area and surface potential-area isotherms as well as Brewster angle microscopy and reflection spectroscopy. In contrast to dye 1, dye 2 interacts specifically with Hg(2+) and Ag(+) cations forming complexes. No complex formation was observed with alkali and earth alkali metal ions. The nature of the anion (Cl(-) or ClO(4)(-)) influences the monolayer behaviour of both dyes. At the air/water interface, besides monomers of the dyes, two types of associates are coexisting in the pure dye monolayers on aqueous salt solutions, attributed to dimers and aggregates, respectively. Their equilibria depend on the nature of both cations and anions in the subphase, as in the case of dye 2, or only anions, as in the case of dye 1. The dimers may be organized as head-to-tail dimers with the intermolecular distances 0.38 and 0.45nm for dye 1 and dye 2, respectively. According to the extended dipole model, we propose formation of aggregates in which the chromophores are parallel to each other with the same intermolecular distances as in the dimers, and the centers of their transition moments shifted by 0.95nm (dye 1) and 1.2nm (dye 2).

Monolayers of a novel ionoselective butadienyl dye.

The novel amphiphilic benzodithia-18-crown-6 butadienyl dye (1) forms relatively stable insoluble monolayers on distilled water (collapse pressure of 41 mN/m) and on aqueous subphases containing alkali metal or heavy metal salts (collapse pressures in the range of 27-38 mN/m, respectively). The dye 1 monolayer organization depends on chromophore association and interactions (especially complex formation) with heavy and alkali metal ions as deduced from surface pressure-area and surface potential-area isotherms as well as reflection spectra and Brewster angle microscopy observations. Dye 1 undergoes specific interactions with Hg(2+) and Ag(+), respectively (formation of different complexes). Nonspecific interactions have been observed with other salts, such as KClO(4) or Pb(ClO(4))(2). Further, dye 1 monolayers on 1 mM Hg(ClO(4))(2) solution undergo reversible photoisomerization, in contrast to monolayers on water and other aqueous salt subphases.