Confocal Fluorescence Microscope Studies of the Adsorptive Behavior of Dioctadecyl-rhodamine B Molecules at a Cyclohexane-Water Interface

Quantification of Target Molecules Needed To Detect Microorganisms by Fluorescence In Situ Hybridization (FISH) and Catalyzed Reporter Deposition-FISH

“…The value obtained here for conventional FISH on glass slides (approximately 370 16S rRNA copies per cell) is low compared to the detection limit of flow cytometers (at least those which were used before 1995), which were used to sort probe-stained bacterial pure cultures (several thousand ribosomes per cell) (4). This is consistent with the findings of Zheng and Harata (50), who reported that a CLSM could detect as few as 82 rhodamine molecules in an area of 1.4 m 2 , which is similar to the area of a single bacterial cell in a two-dimensional image. Moreover, the detection of the E. coli cells in our FISH experiments on glass slides was facilitated by the almost complete absence of fluorescent background.…”

Surface Properties of Surfactant-Free Oil Droplets Dispersed in Water Studied by Confocal Fluorescence Microscopy

“…By fitting the fluorescence intensity ( I F ) vs the concentration ( C o ) relationship to the Langmuir adsorption isotherm (eq 4), the values of K and GN max were obtained to be (2.9 ± 0.3) × 10 5 M -1 and (2.5 ± 0.08) × 10 4 counts/s, respectively. The Gibbs energy of adsorption, −Δ G ads °, corresponding to the adsorption constant K , was further calculated to be 30 ± 1 kJ mol -1 with the relation Δ G ads ° = − RT ln K , where R is the gas constant and T is the absolute temperature (296 K). , As for adsorption of dioctadecyl-rhodamine B dissolving in cyclohexane on a cyclohexane−water interface, the Gibbs energy of adsorption, − G ads °, which is obtained by using the Langmuir adsorption isotherm, is reported to be 39 kJ mol -1 , which is comparable to the adsorption energy of amphiphiles being adsorbed from an organic phase on a liquid−liquid interface . The dioctadecyl-rhodamine B molecules at the interface are in the zwitterionic and cationic forms, rather than in the lactone form.…”

“…If self-quenching and energy transfer between the adsorbed DCM molecules are disregarded, the fluorescence intensity, I F , of the adsorbed DCM molecules is proportional to the number density, N s , of DCM molecules in the focal area, and is given as where G is a constant; in the present experimental condition, G turns out to be the number of photon counts detected per DCM molecule in 13 s. The adsorption isotherm of the DCM molecules on the flat interface was obtained through measuring the fluorescence intensities of DCM in the interface and inside the n-decane liquid as a function of the DCM concentration in the n-decane liquid (see Figure 6). We employed the Langmuir adsorption isotherm for describing the condensation of DCM molecules in the peripheral region of the interface, since it is successfully applied to various systems akin to the present system such as adsorption of neutral hydrophobic molecules in air-liquid, 30 solid-liquid, 31 and liquid-liquid 16 interfaces. The number density, N s , of the DCM molecules in the interface is expressed by the Langmuir adsorption isotherm as where N max is the number density of the DCM molecules at saturation, and K is the equilibrium constant of adsorption (Langmuir constant).…”

“…For instance, Zheng et al have demonstrated the utility of CFM under a limited depth resolution in the studies of insoluble chromophores as well as surface-active soluble chromophores in air-water and oil-water interfaces. [14][15][16] On the other hand, the extremely small probe volume of CFM facilitates detection and identification of nanometer-sized droplets dispersed in a liquid. 17,18 Actually, we have observed dye-labeled surfactant-free n-decane droplets dispersed in water by using CFM and have revealed that dye molecules in a given droplet permeate through the n-decane-water interface at a rate that depends critically on the droplet diameter.…”

Imaging of the Liquid−Liquid Interface under Electrochemical Instability Using Confocal Fluorescence Microscopy

“…The microscopic structure at the liquid−liquid interface at the incipient stage of the electrochemical instability may then be observed with microscopic techniques. CFM has the potential to observe adsorbed molecules at the liquid−liquid interface with high sensitivity and selectivity, because CFM has a higher depth resolution than conventional fluorescence microscopy and is suitable for the observation of the fluorophore-adsorbed liquid−liquid interface in the presence of the fluorophore in the adjacent bulk phase. In this work, we successfully imaged the inhomogeneity at the 1,2-dichloroethane (DCE)|water (W) interface caused by the transfer of dodecyl sulfate (DS − ) across the interface using CFM and a probe, a fluorescent phospholipid, which is zwitterionic and stays adsorbed in the entire range of the applied potential across the interface, unless disturbed by the electrochemical instability.…”