PubMed · 8772796
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B F Brandt. 1996-08-30. Developing a workshop to address unresolved research issues.. https://doi.org/10.1080/009841096161041
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A fluorescent microscopic determination of trace amount of tetracycline is reported based on the aluminum-sensitized fluorescence effect of a self-ordered ring formed by a sessile droplet on glass slide support. Since the evaporative loss of the solvent from the edge wedge of the droplet that is spotted on a hydrophobic-treated glass slide, an outward capillary flow of the interior solvent of the droplet occurs. The resulted outward capillary flow then carries the solute to the perimeter of the droplet spot where the solute accumulates to form a fluorescent self-ordered ring (SOR). Depending on the spotted volume of the aluminum-tetracycline chelate solution, different size of SOR with the outer diameter (o.d.) less than 1.1mm and the ring belt width less than 21.6 microm can be obtained. Data analysis for the imaged SOR by using a digitalized CCD camera showed that the chelate molecule across the fluorescent SOR belt section follows a Gaussian distribution, and the maximum fluorescent intensity (I(max)) was found to be proportional to tetracycline content. When a 0.1 microl droplet was spotted on the solid surface, tetracycline in the range of 7.5-800.0 fmol (or 7.9 x 10(-8) to 800.0 x 10(-8)moll (-1)) can be detected, and the limit of detection can reach 0.8 fmol (or 7.9 x 10(-9) moll (-1)). With present method, the contents of tetracycline in capsule, tablet, urine and fresh milk were satisfactorily detected with the recoveries of 97.0-106.5% and RSD of 1.2-4.2%, correspondingly.
The interaction of ferric, aluminum, and chromium ions with humic acids at different pH of mixture has been investigated. The concentration of metal ions, bound with humic acid is proportional to the concentration of metal ion in water solution at pH 3 at low metal ion concentrations. The ratio of the number of ferric ions, bound with humic acid, to the number of acidic groups in humic acid is more than 1.5 at high ferric ion concentration in solution. That is bound with the formation of dimers of ferric ions and their treatment with acidic groups of humic acid. The radius of particles formed in the reaction of humic acid with ferric ion does not depend on the pH and decreases in the reaction with chromium and aluminum ions at pH higher than 4. An increase of metal ion concentration leads to the increase of the particle radius at low metal ion concentration reaching the constant value at high metal ion concentration and pH 6.1.
cDNAs expressed preferentially in an Al-tolerant microorganism were isolated by subtraction hybridization with cDNAs of Al-sensitive Penicillium chrysogenum IFO4626 as driver cDNA and cDNAs of the Al-tolerant mutant derived from the wild cells by UV irradiation as tester cDNA. Northern blot analysis revealed that mRNA levels of six genes were increased significantly in the Al-tolerant mutant after exposure to Al stress when compared with the wild cells. Two genes accumulated in both the presence and absence of Al stress and four genes were induced by Al stress in the Al-tolerant mutant. cDNA fragments were amplified by rapid amplification of cDNA ends and sequenced to obtain full-length cDNAs of the six genes. Two genes were novel or predicted ones and the others showed significant homology to known genes, ADP/ATP translocase, enolase, cysteine synthase, and glucoamylase, which are induced by environmental stresses in prokaryotic and eukaryotic cells. These enzyme activities increased in the Al-tolerant mutant when compared to those in the wild cells, showing that not only the levels of gene expression but also the levels of enzyme activities increased in the Al-tolerant mutant.