Light-induced membrane potential changes and rectification in Acetabularia.

The application of 2,4-dinitrophenol and 2,6-dinitrophenol as reagents for a ion pair extraction spectrophotometry was tested. The ion pair extraction spectrophotometry experiments were carried out using a simplified procedure (test tube method). Four cationic tensides were used as model analytes. After the optimal conditions of the assay were being determined, the influence of the concentration excess of the reagents on the absorbance of the chloroform extract was investigated. Calibration curves were constructed; an estimation of limits of quantitation was performed and apparent molar absorption coefficients were determined. The obtained results show that both investigated dinitrophenols are suitable for the studied purpose.

Dinitrophenols↗

PubMed1998

Improved mRNA in situ hybridization on formaldehyde-fixed and paraffin-embedded tissue using signal amplification with different haptenized tyramides.

We report an optimized in situ hybridization (ISH) protocol with a rapid signal amplification procedure based on catalyzed reporter deposition (CARD) to increase the sensitivity of non-isotopic mRNA ISH on formaldehyde-fixed and paraffin-embedded tissue. The CARD method is based on the deposition of haptenized tyramide molecules in the vicinity of hybridized probes catalyzed by horseradish peroxidase. Commercially available and newly synthesized haptenized tyramides, including digoxigenin-, biotin-, di- and trinitrophenyl- as well as fluorescein-tyramide, were compared. The haptenized tyramides were visualized using peroxidase conjugated anti-hapten antibodies followed by the diaminobenzidine reaction. As a test system, we applied digoxigenin-labeled oligonucleotides to detect insulin and vasoactive intestinal polypeptide mRNA in pancreatic endocrine tumors and liver metastases. Our results indicate that specificity, sensitivity, and applicability of oligonucleotide mRNA ISH can be significantly improved by using chemically digoxigenin-labeled oligonucleotide probes and signal amplification by CARD. Furthermore, all tested tyramides provided approximately equal amplification efficiency. In conclusion, CARD signal amplification should further promote mRNA ISH studies on paraffin-embedded tissues and allow for multiple-target nucleic acid detection in situ.

Dinitrophenols↗

PubMed1997

Definition of the substrate specificity of the 'sensing' xylanase of Streptomyces cyaneus using xylooligosaccharide and cellooligosaccharide glycosides of 3,4-dinitrophenol.

The title compounds, (Xylp beta (1-->4))nXylp beta-3,4-DNP (n = 0-4) have been made by selective anomeric deprotection of peracetylated xylose oligosaccharides with hydrazine, followed by formation of the trichloroacetimidate, uncatalysed reaction with 3,4-dinitrophenol, and Zemplén deacetylation. The values of k(cat)/K(m) for 3,4-dinitrophenol release from these substrates by xylanase III of Streptomyces cyaneus, expressed in Escherichia coli, increase with increasing n up to n = 2 and then slightly decrease. Since it is known from previous work that in its normal host, the enzyme is produced constitutively at low levels and excreted, these results suggest that the biological function of the enzyme may be to produce small molecule inducers, predominantly xylotriose, from the non-reducing end of the xylan. Activity on cellooligosaccharide glycosides (Glcp beta (1-->4))nGlcp beta-3,4-DNP (n = 0-3) was detected, at a rate about two-and-a-half orders of magnitude less than that observed on the corresponding xylooligosaccharides, indicating that the enzyme is a true xylanase.

Dinitrophenols↗