Molecular assembling is one of the current interests in the field of bottom-up nanotechnology. Self-assembled monolayers of sulfur-containing molecules or supramolecular assemblies via surface sol-gel processes formed on conductive supports are chemically robust and can be easily fabricated without sophisticated instruments. We have fabricated various types of molecular assemblies consisting of donor-acceptor pairs on the surfaces of gold and indium-tin-oxide electrodes. Build-up of three-dimensional multi structures consisting of thiol dyes and gold nanoparticles also has been successful. These assemblies showed clear photocurrent responses in photoelectro-chemical cells. In this article, we will describe recent progress on photoelectric conversion using molecular assemblies especially focused on our research results.

The synthesized macrocycle L was found to be a smart fluorescent receptor which distinguishable efficiently from various neutral molecules with the functional groups such as the electron donating (X =$CH_3$, N($CH_3$)$_2$ and O$CH_3$) and electron withdrawing groups (X =F and Cl), respectively. In the case of guest molecules containing electron donating groups, the fluorescence of macrocycle L was enhanced in the presence of the guest molecules. On the contrary, in the case of guest molecules containing electron withdrawing groups, it was almost quenched in the presence of those.

Fluorescence quenching of l,4-bis [2-(2-methylphenyl) ethenyl]-benzene (Bis-MSB) by carbon tetrachloride in five different solvents namely hexane, cyclohexane, toluene, benzene and dioxane has been carried out at room temperature with a view to understand the quenching mechanisms. The Stern-Volmer plot has been found to be non-linear with a positive deviation for all the solvents studied. In order to interpret these results we have invoked the Ground state complex and Sphere of action static quenching models. Using these models various rate parameters have been determined. The magnitudes of these parameters imply that sphere of action static quenching model agrees well with the experimental results. Hence the positive deviation in the Stem-Volmer plots is attributed to the static and dynamic quenching. Further, with the use of Finite Sink approximation model, it was possible to check whether these bimolecular reactions as diffusion limited and to estimate independently distance parameter R' and mutual diffusion coefficient D. Finally an effort has been made to correlate the values of R'and D with the values of the encounter distance R and the mutual diffusion coefficient D determined using the Edwardis empirical relation and Stokes-Einstein relation.

The sharp-line absorption spectrum of microcrystalline samples of cis-[Cr(cycb)$Cl_2$]Cl (cycb=rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) has been measured between 13000 and $16000 cm^{-1}$ at temperatures down to 5K. The 77K emission and excitation spectra, and 298 K infrared and visible absorption spectra have also been measured. The nine electronic bands due to spin-allowed and spin-forbidden transitions were assigned. Using the observed transitions, a ligand field analysis has been performed to probe the ligand field properties of coordinated atoms in the title chromium(III) complex. The zero-phonon line in the sharp-line absorption spectrum splits into two components by $240 cm^{-1}$ , and the $large ^2$$_E{g}$ splitting can be reproduced by the modem ligand field theory. It is confirmed that nitrogen atoms of the macrocyclic cycb ligand have a strong $\sigma$-donor character, but chloride ligand has weak $\sigma$- nd $\pi$-donor properties toward chromium(III) ion.n.

The kinetics of the loss of leaf fresh weight during incubation of barley and rice leaves in 9% or 15% NaCl solutions were biphasic, indicating the existence of a controlling mechanism for water transport. The first rapid phases reached their plateaus within 1 and 2 h in the case of rice and barley leaves, respectively. When barley leaves were fed with sodium fluoride, an inhibitor of phosphatase inhibitor, through their epicotyls for 3 h in darkness, prior to the treatment of NaCl, the biphasic pattern shown during NaCl treatment was disappeared resulting in linear decreases in the relative fresh weights. The results suggest that NaF accelerates salt-induced water efflux from plant cells, possibly by inhibiting the protection mechanism that may act in NaF-untreated leaves. The linear water loss can be explained in terms of phosphorylation of aquaporin by blocking its dephosphorylation in the presence of the phosphatase inhibitor to keep aquaporin in a phosphorylated form. However, the effect of NaF shown in barley leaves were not observed in rice. These results suggest that the regulation of water transport depends on plant species, and the mechanism for the controlling water transport in rice is different from that of barley.

The mechanism of interaction of cyanocobalamin (CB) with bovine serum albumin (BSA) has been investigated by spectrofluorometric and circular dichroism methods. Association constant for the CB-BSA system showed that the interaction is non-covalent in nature. Binding studies in the presence of an hydrophobic probe, 8-anilino-l-naphthalene sulphonic acid, sodium salt (ANS) showed that there is hydrophobic interaction between CB and ANS and they do not share common sites in BSA. Stern-Volmer analysis of fluorescence quenching data showed that the fraction of fluorophore (protein) accessible to the quencher (CB) was close to unity indicating thereby that both tryptophan residues of BSA are involved in drug-protein interaction. The rate constant for quenching, greater than $10^{10}$ $M^{-1}$ $s^{-1}$, indicated that the drug binding site is in close proximity to tryptophan residue of BSA. Thermodynamic parameters obtained from data at different temperatures showed that the binding of CB to BSA involves hydrophobic bonds predominantly. Significant increase in concentration of free drug was observed for CB in presence of paracetamol. Circular dichroism studies revealed the change in helicity of BSA due to binding of CB to BSA.

[Ru(2,2'-bipyridine)$_2$(4,4'-dicarboxy-2,2'-bipyridine)]$^{2+}$(RuBDc) is a very photostable probe that possesses favorable photophysical properties including long lifetime, high quantum yield, large Stokes' shift, and highly polarized emission. To evaluate the usefulness of this luminophore (RuBDc) for studying macromolecular dynamics, its intensity and anisotropy decays when conjugated to RNA bacteriophage MS2 were examined using frequency-domain fluorometry with a high-intensity, blue light-emitting diode (LED) as the modulated light source. The intensity decays were best fit by a sum of two exponentials, and the mean intensity decay time was 442.2 ns. The anisotropy decay data showed a single rotational correlation time (2334.9 ns), which is typical for a spherical molecule. The use of RuBDc enabled us to measure the rotational correlation time up to several microseconds. These results indicate that RuBDc can be useful for studying rotational diffusion of biological macromolecules.s.

The key riboflavin synthesis genes are located immediately downstream of luxG in the lux operon from Photobacterium leiognathi. It is of interest that a site capable of forming a rho-independent terminator does not appear to be present between luxG and ribE in our previous data. These results raise the question of whether the transcription of lux and rib genes is integrated or not. In order to answer the question, in vivo transcriptional assay and Southern blot were examined. These studies demonstrate that neither transcriptional terminator nor promoter site is present in the intergenic region between of lux and rib genes as well as that the riboflavin genes are single copy in a chromosome of Photobacterium leiognathi.