Influence of soil reducing capacity on the mechanisms driving mercury behaviour

AbstractThe reducing potential of fresh cigarette smoke can be modified by the use of certain oxidants and reductants. The influence of these additives on smoke may be monitored by employing a system which measures changes in EMF on a puff by puff basis. The addition of the oxidant 1,4-benzoquinone to tobacco eliminates the rapid reduction in potential which normally takes place when an untreated cigarette is smoked. The addition of the benzoquinone alters the composition of the smoke by increasing the levels of the total particulate matter and possibly the phenols, while decreasing the nicotine content without affecting the amount of benzo[a]pyrene formed. The addition of sodium thiosulfate to tobacco causes a significant increase in the reducing capacity of cigarette smoke. It also brings about increases in the smoke BAP, phenols and TPM. The level of nicotine in these cigarettes, however, is lowered.

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Influence of 2,5-dichloro-1,4-benzoquinone on jack bean urease activity. Inhibitory effect, total reducing capacity and DPPH radical scavenging activity.

Acta Biochimica Polonica ◽

10.18388/abp.2011_2234 ◽

2011 ◽

Vol 58 (4) ◽

Cited By ~ 2

Author(s):

Mirosława Kot ◽

Zofia Olech

Keyword(s):

Light Exposure ◽

Radical Scavenging Activity ◽

Radical Scavenging ◽

Order Rate Constant ◽

Inhibitory Effect ◽

Pseudo First Order Reaction ◽

Experimental Conditions ◽

Jack Bean ◽

Direct Modification ◽

Reducing Capacity

Inhibition of jack bean activity by 2,5-dichloro-1,4-benzoquinone (DCBQ) was studied in phosphate buffer, pH 7.0. It was found that DCBQ acted as a strong, time and concentration dependent inactivator of urease. Under the experimental conditions obeyed the terms of pseudo-first-order reaction, urease was totally inactivated. Application of Wilson-Kitz method proved that the urease-DCBQ interaction followed a simple bimolecular process and the presence of intermediate complex was undetectable. The determined second order rate constant of the inactivation was 0.053 (μM min)(-1). Thiols such as l-cysteine, glutathione and dithiothreitol (DTT) protected urease from inhibition by DCBQ but DCBQ-modified urease did not regain its activity after DTT application. The thiol protective studies indicated an essential role of urease thiol(s) in the inhibition. The irreversibility of the inactivation showed that the process was a result of a direct modification of urease thiol(s) by DCBQ (DCBQ chlorine(s) substitution). The decomposition of DCBQ in aqueous solution at natural light exposure was monitored by visible spectrophotometry, determination of the total reducing capacity (Folin-Ciocalteu method) and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging ability. The DCBQ conversion resulted in a decrease of the inhibition power and was well correlated with the increase of the total reducing capacity and DPPH scavenging ability. These findings were attributed to DCBQ transformation by photolysis and the hydrolysis effect was found to be negligible.

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