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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Inhibition of polyphenol oxidase by sulfur dioxide

Sayavedra-Soto, Luis Alberto 03 October 1983 (has links)
Inhibition of polyphenol oxidase (PPO) by sulfur dioxide (SO₂) was studied using three different sources of PPO (banana, mushroom, and pear). Several methods to detect PPO activity were tested due to SO₂, interference in some of the assays. The method using 2-nitro-5-thiobenzoic acid (TNB) to react with the quinones was found to be the most reliable for assaying PPO activity in the presence of SO₂ whereas, the oxygen electrode and spectrophotometric methods were not suitable. When PPO was exposed to SO₂ prior to the substrate addition, it was inhibited irreversibly. Trials to regenerate the PPO activity using extensive dialysis, column chromatography, and addition of copper salts were not successful. Experiments using Cu(II) and the TNB method to regenerate the activity of the pear PPO apoenzyme that was not exposed to SO₂, also showed the turnover between Cu(I) and Cu(II) during the enzyme oxidation of o -phenols. Increased concentrations of SO₂ and pH less than 5 enhanced the inhibition of PPO by SO₂. At pH 4 concentrations greater than 20 ppm completely inhibited 1,000 units of PPO activity almost instantaneously. This suggests SO₂ as such as the main form inhibiting PPO. Kinetic studies confirmed the irreversibility of the inhibition. Purified pear PPO was used to determine binding of ³⁵SO₂ to the enzyme. Column chromatography, extensive dialysis and gel electrophoresis did not show SO₂ bound to PPO protein. Formation of extra bands on gel electrophoresis in the SO₂ inhibited pear PPO fractions was demonstrated. This and other evidence suggests that there was a modification of the protein structure of PPO, with retention of protein integrity. Also it is suggested that this was the main mode of direct irreversible inhibition of PPO by SO₂. / Graduation date: 1984
2

Annelation and pyrolysis reactions of 3-thiabicyclo[3.2.0]heptane-3,3-dioxide ring systems

Henry, William John January 1987 (has links)
No description available.
3

The magnetic rotation spectrum of sulfur dioxide in the 3000A region

Hardwick, John Lafayette 12 1900 (has links)
No description available.
4

A separation of the saturated and unsaturated components of cottonseed oil with liquid sulfur dioxide

Childress, John Bowles 05 1900 (has links)
No description available.
5

The absorption of sulfur dioxide by condensing aerosols

Travis, Edward Outlaw 08 1900 (has links)
No description available.
6

Novel adsorbents using metal complexes

Rao, Sumitrananda N. R. 08 1900 (has links)
No description available.
7

Comparison of sulfur dioxide air quality data with the PALSEM model

Carlson, Diane Marie Halverson 08 1900 (has links)
No description available.
8

Effect of sulfur dioxide on asbestos

Madry, James Thomas 12 1900 (has links)
No description available.
9

Sulfur dioxide reactions with aqueous solutions of manganese at high temperature and with ammonia in the gas phase.

Hartley, Edwin M. 12 1900 (has links)
No description available.
10

The Systems of Sulphur Dioxide and Ortho, Meta and Para Xylenes

Martin, K.W. January 1932 (has links)
[No abstract available] / Science, Faculty of / Chemistry, Department of / Graduate

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