A laser scanning fluorescence microscope system has been fabricated for single molecule detection (SMD). Problems associated with the system set-up have been discussed along with proper suggestions. Based on the SMD results obtained by using the apparatus, a statistical method has been suggested to determine the minimum number of required molecules to form a group of uniform average in a selected error range.

The present investigation is an attempt to create an optimized protocol for a bactericidal modality of different powers of He-Ne laser radiation to eliminate periodontitis disease causing bacteria from dental plaques. Periodontitis is most prevalent infectious disease of men and caused by a limited number of Gram negative oral bacteria. Porphyromonas gingivalis and Streptococcus sanguis are the important bacteria responsible for periodontitis diseases. Effect on periodontitis disease causing bacteria were produced by the exposure of different powers of He-Ne laser light i.e. 9 mW, 17 mW and 26 mW of red colour of wavelength 632.8 nm in two different periods of time i.e. 10 min. and 20 min. in the presence of dye Methylene blue (MB) used as a photosensitizer. The results have been shown in terms of percentage inhibition of colony forming units (cfu.) of bacteria. This study has shown that maximum inhibition of cfu. were observed in Laser+MB-20 min. exposure time. This inhibition was followed by Laser+MB-10 min., but minimum inhibition was seen in Laser only at 10 min. exposure. In case of effect of methylene alone on the cfu. of bacteria, it was seen that MB have not shown more inhibition of cfu. and it had shown that the no. of cfu. are very similar to that of control. The above observation of the present study was seen in case of every 3 different type of used powers of laser for both the bacteria. Maximum percentage inhibition of cfu. were seen in case of 26mW powers of He-Ne laser, which was 67. 28% to 61.42% for Porphyromonas gingivalis and Streptococcus sanguis respectively. So, increasing the power of laser (safe range for dentistry is 3-30 mW) under conditions shows an increased percentage inhibition of cfu. Thus the present investigation may be a useful adjunct with mechanical debridement in the prevention of recolonization of subgingival lesions by pathogenic microorganisms which are harmful and drug resistant.

Some quinones such as 1,4-benzoquinone 2, 1,4-naphthoquinone 3 and 1,2-naphthoquinone 4 dissolved in diethylamine were irradiated with 300 nm UV light to afford red aminoquinones 6, 7, and 9 as the major products. Irradiation of a solution of a primary product, i.e., 2,5-bis(diethylamino)-1,4-benzoquinone 6 in benzene gave 2,5-bis (ethylamino)-1,4-benzoquinone 10 in 80% yield, along with an oxazoline 11 in 19% yield via photochemical deethylation. A solution of 2-diethylamino-1,4-naphthoquinone 7 in benzene was also irradiated under the same condition, in which 2-ethylamino-1,4-naphthoquinone 12 was obtained in ca. 100% yield.

The mechanism of interaction of four coumarin derivatives (CDS) with bovine serum albumin (BSA) was studied using spectrofluorometric technique. It was found that the coumarin ring common to all CDS makes major contribution to interaction. Binding affinities could be related to parachor values of CDS. Stem-Volmer plots indicated the presence of static component in the quenching mechanism. Results also showed that both tryptophan residues of protein are accessible to CDS. The high magnitude of rate constant of quenching indicated that the process of energy transfer occurs by intermolecular interaction forces and thus CDS binding site is in close proximity to tryptophan residues of BSA. Binding studies in the presence of the hydrophobic probe, 8-anilino-l-naphthalein-sulfonic acid showed that there is hydrophobic interaction between CDS and the probe and they do not share common sites in BSA. Thermodynamic parameters obtained from data at different temperatures showed that the binding of CDS to BSA involve hydrophobic bonds predominantly. The effects of various metal ions on the binding of CDS with BSA were also investigated.

The macrocycle L exhibited a switch on-off behavior through the fluorescent responses by aromatic imine molecule 1 (X=H) / trifluoroacetic acid (TFA). In the 'switch on' state, it was supposed that the aromatic imine molecule 1 is in the cavity of macrocycle L and a photoinduced electron transfer (PET) from the nitrogen of azacrown part to the anthryl group is inhibited by the interaction between the aromatic imine molecule 1 and the azacrown part of macrocycle L. In the 'switch off' state, it was supposed that the protonated imine molecule 1 is induced by the continuous addition of TFA and a repulsion between the protonated azacrown part and the protonated imine molecule 1 is occurred. It was considered that this process induces the intermolecular PET from the protonated imine molecule 1 to the anthryl group of macrocycle L because of a proximity effect between the anthryl group and the protonated imine molecule 1. From the investigation of the transient emission decay curve, the macrocycle L showed three components (3.45 ns (79.72%), 0.61 ns (14.53%), and 0.10 ns (5.75%). When the imine molecule 1 was added in the macrocycle L as molar ratio=1:1, the first main component showed a little longer lifetime as 3.68 ns (82.75%) although the other two components were similar as 0.64 ns (14.28%) and 0.08 ns (2.96%). On the contrary, when the imine molecule 3 (X=C1) was added in the macrocycle L as molar ratio=l:1, all the three components were decreased such as 3.27 ns (69.83%), 0.44 ns (13.24%), and 0.06 ns (16.93%). The fluorescent pH titration of macrocycle L was carried out from pH=3 to pH=9. The macrocycle L and C $U^{2+}$- macrocycle L complex were intersected at about pH=5, while the E $u^{3+}$ -macrocycle L complex was intersected at about pH=5.5. In addtion, we investigated the fluorescence change of macrocycle L as a function of the substituent constant ($\sigma$$_{p}$$^{o}$) showing in the para-substituent with electron withdrawing groups (X=F, Cl) and electron donating groups (X=C $H_3$, OC $H_3$, N(C $H_3$)$_2$), respectively, as well as non-substituent (X=H).).ctively, as well as non-substituent (X=H).

${\alpha}$,${\alpha}$-Dibromovalerophenone and ${\alpha}$,${\alpha}$-dichlorovalerophenone were prepared and their photochemical behaviors were investigated. The former gives C-Br cleavage products and the latter gives mainly the Yang photocyclization products upon irradiation. The reactivity of the chlorine substituted ketone turned out to be quite different from that of ${\alpha}$,${\alpha}$-difluorovalerophenone which gives both the cyclization and elimination products from the 1,4-biradical intermediate.

Deoxygadusol (DO) and structurally related mycosporine-like amino acids, i.e. mycosporine glycine (MO) and mycosporine taurine (MT), were isolated from phytoplankton Prorocentrum micans and studied for the reactivity toward singlet oxygen. These water-soluble compounds with a cyclohexenone chromophore were all shown to be highly effective in quenching singlet oxygen ($^1$ $O_2$), with the efficiencies being significantly larger compared with histidine, a well-known $^1$ $O_2$ quencher. The $^1$ $O_2$ reaction rate constant ( $k_{Q}$) of DG was determined to be 5.4 ${\times}$ 10$^{7}$ $M^{-1}$ $s^{-1}$ by a steady state method based on competitive inhibition of rubrene oxidation. The feasibility of this method was confirmed by estimating the $k_{Q}$ values for MG and two other quenchers, furfuryl alcohol and 1,4-diazabicyclo [2,2,2]octane, and comparing with those values determined by the time-resolved $^1$ $O_2$ decay method in the previous work.ork.

A porphyrin compound containing a crown ether moiety (Por-Crown) and its zinc complex (ZnPor-Crown) have been prepared and the effect of the addition of alkali metal on their fluorescence has been investigated. As alkali metal cations were added, the absorption and fluorescence maxima did not change. However, the absorbance and intensity of fluorescence increased dramatically. Among the alkali metal cations tested, addition of K$^{+}$ and Cs$^{+}$ showed strongest enhancement of absorbance and fluorescence intensity of Por-Crown and ZnPor-Crown.own.