ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

Hits per page

hits 1 - 2 | 2 hits

Sorting

Electronic Resource

Plastic colorimetric film sensors for gaseous ammonia (1995)

Mills, Andrew ; Wild, Lorraine ; Chang, Qing

Springer

Microchimica acta 121 (1995), S. 225-236

add to mindlist on the mindlist

Details

ISSN: 1436-5073

Keywords: ammonia ; sensor ; colorimetric ; plastic ; optical

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract The preparation and characterization of three different plastic thin-film colorimetric sensors for gaseous ammonia is described. In the film sensors, the neutral form of a pH-sensitive dye (Bromophenol Blue, Bromocresol Green or Chlorophenol Red) was encapsulated in a plastic medium, either poly(vinyl butyral) or ethylcellulose plasticized with tributyl phosphate. Each of these film optodes gave a reproducible and reversible response towards gaseous ammonia. The sensitivity of the film sensors towards ammonia was found to be strongly dependent upon the pK a of the encapsulated dye. Thus, the film with Chlorophenol Red (pK a = 6.25), proved to be very insensitive (operating range: 0.29% 〈 %NH3 〈 100%), whereas the film with Bromophenol Blue (pK a = 4.1), was much more sensitive (operating range: 0.0003% 〈 %NH3 〈 0.11%). The sensitivity of a plastic film sensor decreased markedly with increasing operating temperature and the 90% response (15–38 s) and recovery (820-127 s) times were slow and activation-controlled.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01248252

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

Electronic Resource

Tris-dependent oxidative DNA strand scission during electrophoresis (1995)

Ray, Trevor ; Mills, Andrew ; Dyson, Paul

Weinheim : Wiley-Blackwell

Electrophoresis 16 (1995), S. 888-894

add to mindlist on the mindlist

Details

ISSN: 0173-0835

Keywords: Streptomyces ; DNA modification ; Oxidative DNA strand scission ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Chemistry and Pharmacology

Notes: The DNA of two Streptomyces species contains site-specific labile modifications. During gel electrophoresis the DNA can undergo Tris-dependent strand scission at the positions of these modifications. Our investigations into the nucleolytic activity which reacts with the modifications implicate a peracid derivative of Tris formed at the anode; the kinetics of production and decay of this activity were followed using both a DNA cleavage assay and a reduced methyl viologen assay to measure oxidant. Anode activation could be chemically mimicked by addition of peracetic acid to Tris buffers. We tested the DNA cleavage activity of several other compounds after anode or chemical activation; we used an analogue of Tris lacking a primary amine group and also several reagents known to promote DNA strand cleavage by amine-catalysis at abasic sites. Anode generation of oxidant could be detected for compounds containing either hydroxyl or carboxyl groups. However, DNA cleavage activity correlated with oxidant formation only for those compounds also containing primary amine groups. These results support a mechanism of DNA strand scission at modification sites via concerted peracid-mediated oxidative and amine-catalysed reactions. The novel finding of Tris-dependent formation of a long-lived reactive oxidant at the anode suggests that this compound is unsuited as an electrophoresis buffer for certain biological macromolecules.

Additional Material: 3 Ill.