Video enhanced differential interference contrast microscopy: Characterizing colloidal materials

Video enhanced differential interference contrast microscopy (VEDICM) permits an immediate, rapid characterization of association colloid aggregates and other colloidal aggregates by direct visualization on a television screen. Particles with sizes down to 500 A, their dynamics, fusion and slow flocculation can be directly pictured, recorded and analyzed in real time, freezeframe, slow motion or time lapse. It is precisely in the distance regime, 500–10,000 A, joining micellar chemistry to the field of biological structures, that classical techniques do have most difficulty. In this domain surfactant aggregates-vesicles, liposomes, microemulsions, microtubules-can exhibit an astonishing dynamic structural diversity and distribution of structures. These are highly sensitive to pH, salt, temperature, and surfactant concentration in ways which are partially understood at a theoretical level, but not formerly easily accessible.In this paper, the VEDICM technique is described and its ability to follow the spontaneous growth and fusion of vesicles upon changes in chemical environment is presented.Session lecture, Ninth International Conference on Non-Aqueous Solutions, Pittsburgh, PA, August 1984.     

Lipophilic derivative of rhodamine 19: characterization and spectroscopic properties

A new octadecylamide derivative of rhodamine 19 was synthesized by reaction of rhodamine 19 ethyl ester (rhodamine 6 G) with octadecylamine. This lipophilic dye exists in two forms: as a cationic species containing a secondary amide group and as an electrically neutral molecule containing an additional ring closed between the oxygen of the amide group and the central carbon of the xanthene part. Both forms were isolated and characterized in detail by means of elemental analysis, mass spectrometry, IR, NMR and UV-VIS spectroscopy. Depending on the hydrogen ion activity in solution and the availability of solvent hydrogen for hydrogen bond formation, the cationic form easily converted into a neutral one and vice versa. On the basis of absorption and emission UV-VIS spectroscopic data, the equilibrium of the two forms was studied in various solvents. An increase in dye concentration in acidified methanol/water mixture (volume fraction of water, ?=80%) led to aggregation of the cationic molecules. Using the UV-VIS absorption data, a corresponding dimerization constant was evaluated.     

Organic micropollutants in the sewage from a phenoxyalkanoic acid production plant after biological treatment in a municipal trickling filters plant

The environmentally hazardous organic substances in the waste water from the manufacture of chlorophenoxyalkanoic acids have been identified and semiquantified before and after passing through a biological treatment plant for municipal sewage, the secondary effluent of which is discharged into a marine ecosystem. The organics belong to three groups: (i) chlorophenols; (ii) chlorophenoxyalkanoic acids; and (iii) chlorinated neutrals. The removal of chlorophenols and phenoxyalkanoic acids was shown to be good, with a 90% overall reduction of chlorinated substances in the sewage passing through the treatment plant. The lowest reduction occurred for the polychlorinated compounds. Two chlorobenzofurans among the chlorinated neutrals were preliminarily identified.     

Perfusive flow and intraparticle distribution of a neutral analyte in capillary electrochromatography

The relevance and magnitude of an electroosmotic perfusion mechanism in electrochromatography is analyzed. To systemize our studies we first considered the transport of an electroneutral and nonadsorbing tracer. Based on the refractive index matching in a microfluidic setup containing fixed spherical porous particles, we conducted a quantitative analysis in real time of the spatio-temporal distribution of fluorescent tracer molecules during their uptake by (and a release from) single particles using confocal laser scanning microscopy. Even under conditions of a significant electrical double layer overlap the intraparticle electroosmotic flow produces due to its unidirectional nature and in striking contrast to the symmetric (spherical) distributions typical for purely diffusive transport strongly asymmetric concentration profiles inside spherical particles as the locally charged pore liquid begins to respond to the externally applied electrical field. The profiles retain an axisymmetric nature, i.e., rotational symmetry with respect to the field direction. Results of our measurements could be successfully interpreted and further analyzed by a compact mathematical model. Intraparticle Peclet numbers of up to 150 have been realized and found to significantly enhance the mass transport on particle scale towards the convection-dominated regime when compared to a conventional (diffusion-limited) kinetics.     

Conformational stability and antibody response to the 18kda heat- shock protein formulated into different vehicles

Protein stability is one of the most important obstacles for successful formulation in the development of new-generation vaccines. Here, the 18kDa heat-shock protein (18kDa-hsp) was chemically modified though conjugation with bovine serum albumin or by esterification with N-hydroxysuccinimide ester of palmitic acid. The biologically active conformation of the protein was preserved after chemical modification. The immune responses to the recombinant 18kDa-hsp fromMycobacterium leprae were studied in different presentations: free, copolymerized with bovine serum albumin in aggregates (18kDa-hsp-BSA), and either surface linked to liposomes or entrapped into liposomes. Measuring the antibody production of immunized genetically selected mice has compared the adjuvant effects of liposomes and proteic copolymer. Among the two liposome preparations, the strongest response was obtained with the surface-exposed antigen-liposomes. The copolymer 18kDa-hsp-BSA conferred a high titer of antibody in injected mice, and persisted 70 d after immunization. This approach should prove very useful for designing more effective vaccines by using 18kDa-hsp as carrier protein.     

Synchronous fluorescence and UV-vis spectrometric study of the competitive interaction of chlorpromazine hydrochloride and Neutral Red with DNA using chemometrics approaches

In this study, we have shown with the use of UV–vis spectrophotometry and the constant wavelength synchronous fluorescence spectroscopy (CW-SFS) techniques that the pharmaceutical drug, chlorpromazine hydrochloride (CPZ), intercalates into the deoxyribonucleic acid (DNA) double helix by partial exchange with the Neutral Red (NR) molecular probe.

We have also demonstrated that with the use of three-way data plots, it is clear that it is important to have well-defined methodology for the selection of the important CW-SFS method parameter, Δλ. Ad hoc selection of this parameter, or even that based on experience, can readily lead to serious errors, which subsequently can be transferred to the interpretation of results. The said three-way plots provide a straightforward diagrammatic method, which improves the selection process of a satisfactory value for Δλ.

Finally, we used PARAFAC modeling to resolve the complex three-way CW-SFS data, which provided simultaneously the concentration information for the three reaction components, NR, CPZ and NR-DNA, for the system at equilibrium. This PARAFAC analysis indicated that the intercalation of the CPZ molecule into the DNA proceeds by exchanging with the NR probe, and can be attributed to two parallel reactions.     

对氨分子敏感的一种方酸二酰胺(SQDAM)新型PVC膜电极

氨是中性分子,它在水溶液中主要以NH_3·H_2O形式存在。氮的测定目前国内外大多数使用氨气敏电极,系将待测液中的氨通过透气膜后改变内充液的pH,再用pH电极测定此变化,间接确定氨含量.也有用硝化菌作为生物催化层的(双膜)电极测定氨。但对中性分子氨敏感的中性载体单膜电极尚未见文献报道.我们在合成双臂型方酰胺多齿     

Determination of neutral cannabinoids in hemp samples by overpressured-layer chromatography

Summary The overpressured-layer chromatographic separation of neutral cannabinaids (Δ⁹ -tetrahydro-cannabinol, cannabidiol, cannabinol, cannabigerol and cannabichromene) has been achieved on amino HPTLC plates with dichloromethane as mobile phase. By use of bidirectional development up to 30 samples can be analysed on a 10 cm×20 cm plate within 4 min. Evaluation was performed by slit-scanning densitometry at 200 nm. System-suitability data confirm the applicability of the method. Presented at Balaton Symposium 01 on High-Performance Separation Methods, Siófok, Hungary, September 2–4, 2001