A rapid cytofluorometric method for quantitative DNA determination on fixed smears

Summary A study has been made of the possibility of using propidium iodide (PI) for the cytofluorometric determination of DNA in fixed smears. A preliminary spectrofluorometric study made it possible to define the optimal conditions for the excitation wavelength and the intensity of the emitted fluorescence. The stoichiometry and specificity of the DNA-PI bond were studied in different materials and for different fixation procedures. In order to check whether RNA might interfere, it was extracted enzymatically from test preparations selectively. The data from such treated sections were not significantly different from those obtained by means of the fluorescent Feulgen reaction (Pararosaniline-SO₂) on the same material. On the other hand, some of the advantages of the PI method are important: (a) the time required for making ready and staining the preparations is very short, and in any case is considerably shorter than the feulgen method; (b) the high quantum yield of the DNA-PI complex induces very high fluorescence intensities which can, therefore, be easily measured, even with low sensitivity instruments; (c) the spectral conditions are particularly favourable for excluding the inner filter effect from the measurement; (d) the photo-decomposition is considerably lower compared to that found in preparations stained by the conventional Feulgen method. The wise possibility of excitation (from the u.v to the green), together with the limited extent of the emission band (which is mainly in the red) are also conditions that are particularly favourable for obtaining multi-parametric determinations simultaneously from the same cell.     

Microbiological method for the determination of L-tryptophan

Sebek, Oldrich K. (The Upjohn Company, Kalamazoo, Mich.). Microbiological method for the determination of l-tryptophan. J. Bacteriol. 90:1026-1031. 1965.-The ability of Chrombacterium violaceum to utilize l-tryptophan for the synthesis of a purple pigment, violacein, served as a basis for the development of a quantitative estimation of this amino acid. The method consists of suspending washed colorless cells of the organism in an agar layer, placing a paper disc impregnated with a tryptophan solution on top of the layer, and allowing the system to incubate. As tryptophan diffuses into the agar, it is converted into violacein, and appears as a zone of striking purple color. Since the diameter of the zone is a function of the amount of tryptophan applied, the amino acid can be quantitatively estimated within the range of 10 to 320 mug per sample with 5.6% standard deviation. The method is fairly specific for free tryptophan, since only indole, indole-3-pyruvic acid, and, to a small degree, anthranilic acid interfere. Other amino acids, tissue homogenates, tryptophan in peptide linkage, or compounds related to this amino acid do not affect its determination. The bacterium does not utilize tryptophan for the synthesis of cellular material unless its growth has been initiated by another substrate.     

A rapid, high-throughput method for quantitative determination of ethanol tolerance in Saccharomyces cerevisiae

There are a variety of methods available for determining ethanol tolerance phenotypes in Saccharomyces cerevisiae. Many of these methods are limited in through-put and/or application. We describe here a microtiter-plate, growth-based, liquid-culture, rapid ethanol tolerance assay (RETA) that overcomes these limitations. Determinations of ethanol tolerance gave results that were comparable to shake-flask cultures, and there was a high level of intra- and inter-plate reproducibility. We report the successful application of this assay to determining the segregation pattern of ethanol tolerance in backcrosses of two ethanol-tolerant mutants (SM and CM) to a non-tolerant parent (W303-1A); RETA was used to determine ethanol tolerance in numerous progeny resulting from these crosses. This assay, or variations thereof, will prove be of great value for anyone attempting to develop quantitative, high-throughput growth assays for yeast or other microorganisms.     

A rapid quantitative method for the determination of thebaine in Papaver bracteatum

A rapid method enabling a quantitative analysis of thebaine in capsules and latex of Papaver bracteatum has been devised, based on a TLC technique. This method was compared to the commonly used GLC procedure, and highly significant correlation coefficient (r = 0.90) and linear regression were found between the two methods. Values for concentrations to the nearest ±0.25% of the standard spots can be reached by this simple and rapid thebaine determination.     

A rapid capillary gel electrophoresis method for the quantitative determination of RuBisCo in spinach

A capillary gel electrophoretic (CGE) method for the quantitative analysis of RuBisCo in spinach leaves was developed. RuBisCo was resolved into large and small subunits in the presence of sodium dodecyl sulphate (SDS) by the CGE procedure which enabled the determination of the molecular weight of each unit accurately; the values so determined were in close agreement with those reported using other methods. Advantages of CGE over SDS-polyacrylamide gel electrophoresis and high-pressure gel filtration include decreased sample preparation and analysis time, superior resolution and greater sensitivity permitting reduced sample size and trace analysis. In addition, CGE provided precise quantification of RuBisCo and was demonstrated to be a viable alternative to other available methods of protein analysis.     

A rapid and direct method for the quantitative determination of tryptophan in the intact protein

1. A method is given for the quantitative determination of free tryptophan or tryptophan in the intact protein by treating with ninhydrin in a mixture of formic acid and hydrochloric acid (reagent b), for 10min at 100 degrees C. Glycyltryptophan was used as a standard for the determination of tryptophan in the intact protein. The extinction at 390nm was linear in the range 0.05-0.5mumol for free tryptophan (in7120) and 0.05-0.30mumol for glycyltryptophan (in15400). 2. Free tryptophan in the presence of protein may be determined by treating with ninhydrin in a mixture of acetic acid and 0.6m-phosphoric acid (reagent a) for 10min at 100 degrees C, the extinction being linear for tryptophan in the range 0.05-0.9mumol. N-Terminal tryptophan peptides also give the typical yellow product on treatment with reagent a. 3. Tryptophan content of several pure intact proteins when treated with the above method gave values in good agreement with those reported by others. A mean tryptophan content of 11.25 (s.e.m. +/-0.08) mumol/100mg of protein was found in rat brain during development from 1 to 82 days after birth.     

A rapid method for quantitative separation of urea cycle intermediates

To our knowledge, there exists no single rapid technique for the quantitative separation of the amino acid intermediates of the Krebs-Henseleit urea cycle. In this cycle, ammonia is converted to urea by a series of reaction beginning with the condensation of l-ornithine with carbamyl phosphate and proceeds sequentially through citrulline, argininosuccinic acid, and, finally, arginine, which is the cleaved to form urea with regeneration of ornithine.This communication describes chromatographic methods which have been found to give satisfactory separation of these compounds in a variety of mixtures. The time required for the separations is slightly over 2 hr which compares favorably with the 12–18 hr needed for papar chromatography or the time required for separations by automatic amino acid analyzers.     

A rapid method for determination of ribonucleotide reductase activity

Ribonucleoside diphosphate reductase activity is determined in centrifuged homogenates by following the conversion of cytosine ribonucleotide to cytosine deoxyribonucleotide. The enzymatic reaction is measured by monitoring the radioactivity of the reaction products separated by thin layer chromatography on PEI-cellulose plates. The method is rapid and permits the simultaneous processing of multiple samples.     

A rapid colorimetric method for the determination of mimosine

A rapid colorimetric method has been described for the quantitative determination of mimosine by using activated carbon as a decolorizing agent and measuring the intensity of mimosine-ferric chloride color produced.     

A rapid spectrophotometric method for the determination of esterase activity

We have developed a spectrophotometric assay method which continuously records esterase activity at 510 nm by monitoring absorbance changes due to the formation of a diazo dye complex. In our method, α-naphthyl ester substrates are hydrolyzed by enzymatic action to α-naphthol which couples to Fast Blue RR salt (a diazonium salt) forming a diazo dye complex. Our method is unique in directly monitoring the formation of the diazo dye complex without extracting the color of the complex as in other methods that use naphthyl esters and diazo coupling of reaction products. The method appears to be limited to α-naphthyl ester substrates, however, since β-naphthyl esters did not give a linear change in absorbance in the enzymatic reactions tested. With this assay method, one can use a single substrate both to determine esterase units quantitatively in solution and to detect esterase staining activity on gel electrophoresis.