Covalent binding studies on the 14C-labeled antitumour compound 2,5-bis(1-aziridinyl)-1,4-benzoquinone. Involvement of semiquinone radical in binding to DNA, and binding to proteins and bacterial macromolecules in situ

2,5-Bis(1-aziridinyl)-1,4-benzoquinone (BABQ) is a compound from which several antitumour drugs are derived, such as Trenimone, Carboquone and Diaziquone (AZQ). The mechanism of DNA binding of BABQ was studied using 14C-labeled BABQ and is in agreement with reduction of the quinone moiety and protonation of the aziridine ring, followed by ring opening and alkylation. The one-electron reduced (semiquinone) form of BABQ alkylates DNA more efficiently than two-electron reduced or non reduced BABQ. Covalent binding to polynucleotides did not unambiguously reveal preference for binding to specific DNA bases. Attempts to elucidate further the molecular structure of DNA adducts by isolation of modified nucleosides from enzymatic digests of reacted DNA failed because of instability of the DNA adducts. The mechanism of covalent binding to protein (bovine serum albumin, BSA) appeared to be completely different from that of covalent binding to DNA. Binding of BABQ to BSA was not enhanced by reduction of the compound and was pH dependent in a way that is opposite to that of DNA alkylation. Glutathione inhibits binding of BABQ to BSA and forms adducts with BABQ in a similar pH dependence as the protein binding. The aziridine group therefore does not seem to be involved in the alkylation of BSA. Incubation of intact E. coli cells, which endogenously reduce BABQ, resulted in binding to both DNA and RNA, but also appreciable protein binding was observed

Herijking EHS Noord-Holland : een toets vanuit het perspectief van ruimtelijke samenhang

De realisatie van de Ecologische Hoofdstructuur in de Provincie Noord-Holland ligt achter op schema. Hierom hebben Gedeputeerde Staten van Noord-Holland besloten te onderzoeken of via een herbegrenzing een groter deel van de EHS nog is te realiseren. De gebieden die in aanmerking komen voor herbegrenzing zijn beoordeeld op de ruimtelijke samenhang van het gebied zelf én de mate waarin het gebied bijdraagt aan de omgeving. Op basis van de analyses mag geconcludeerd worden dat de beoogde herbegrenzing in Noord-Holland goed is voor de ruimtelijke samenhang van de provinciale EHS. Tevens zijn er twee quick-scan analyses uitgevoerd die een positief beeld laten zien van de herbegrenzingen op het niveau van Natuurdoelen en in relatie tot Natura2000-gebieden

Tailoring information about climate change and its impacts

Resultaten van onderzoek naar klimaatverandering en de mogelijke effecten zijn vaak niet beschikbaar in een vorm waarin ze direct door anderen gebruikt kunnen worden. Gebruikers van klimaat- en impactinformatie hebben vaak ook geen goed overzicht over de beschikbare gegevens van alle sectoren en resultaten zijn soms inconsistent

Teenagers and biodiversity - worlds apart? : an essay on young people's views on nature and the role it will play in their future

The children of today have plenty of toys to play with in comparison with some decades ago. Instead of playing outside, they watch television. Recent research in the UK has revealed that primary schoolchildren know more about the different ‘species’ of Pokémon than about plants and animals. Nature is something they see on television, preferably in programs featuring dangerous and spectacular animals. The aim of this study was to find out what young people think biodiversity or nature will mean to their lives in about twenty years time. One of the goals of nature policy is to bring nature closer to people. This study looked at teenagers as a possible target group of government policy. It has thrown up some pointers for meeting young people’s needs and raising their appreciation and understanding of nature and biodiversity. It uncovered a wider gap between young people and nature than the researchers had expected, but also sparked of a desire to know more, and not only among the schoolchildren. This study attracted attention from the media and the subject was discussed on meetings about nature and environmental education. Although the research was conducted in the Netherlands, the picture obtained may also apply to at least the more urbanised regions of Europe where the cultural, economic and social climates are broadly simila

Electrochemistry of potentially bioreductive alkylating quinones : Part 1. Electrochemical properties of relatively simple quinones, as model compounds of mitomycin- and aziridinylquinone-type antitumour agents

The influence of methyl-, hydroxy and amino substituents on the electrochemical behaviour of simple 1,4-naphtho-and 1,4-benzoquinones, model compounds of many quinoid antitumour agents, in aqueous media was studied. Significant changes in electrochemical behaviour were observed, potentially the result of a change in the electron density of the quinone moiety, pre- or post-protonation of substituents, hydrogen bond formation, tautomerization reactions and steric interactions between the quinone moiety and substituents. The information obtained was of benefit in the elucidation of the reduction mechanisms of quinoid antitumour agents such as aziridnylquinones and mitomycins

Mitosene-DNA adducts. Characterization of two major DNA monoadducts formed by 1,10-bis(acetoxy)-7-methoxymitosene upon reductive activation

Reductive activation of racemic 1,10-bis(acetoxy)-7-methoxymitosene WV15 in the presence of DNA, followed by enzymatic digestion and HPLC analysis, revealed the formation of various DNA adducts. Reduction is a necessary event for adduct formation to occur. This reductive activation was performed under hypoxic conditions in various ways:  (1) chemically, using a 2-fold excess of sodium dithionite (Na2S2O4), (2) enzymatically using NADH-cytochrome c reductase, (3) electrochemically on a mercury pool working electrode, and (4) catalytically, using a H2/PtO2 system. Five different mitosene−DNA adducts were detected. These adducts were also present when poly(dG-dC) was used instead of DNA, but were absent with poly(dA-dT). All were shown to be adducts of guanine. Reduction of 1,10-dihydroxymitosene WV14 in the presence of DNA did not result in detectable adduct formation, demonstrating the importance of good leaving groups for efficient adduct formation by these mitosenes. Finally, two of the adducts were isolated and their structures elucidated, using mass spectrometry, 1H NMR and circular dichroism (CD). The structures were assigned as the diastereoisomers N2-(1‘ ‘-n-hydroxymitosen-10‘ ‘-yl), 2‘-deoxyguanosine (n = α or β). These type of adducts, in which the mitosene C-10 is covalently bonded to the N-2 of a guanosylic group, are different from the well-known mitomycin C 2‘-deoxyguanosine monoadducts, that is linked via the mitomycin C C-1 position, demonstrating that the order of reactivity of the C-1 and C-10 in these mitosenes is reversed, as compared to mitomycin C. The 7-methoxy substituent of WV15 is a likely factor causing this switch. Evidence is presented that the 7-substituent of mitosenes also influences their DNA alkylation site. Adducts 4 and 5 represent the first isolated and structurally characterized covalent adducts of DNA and a synthetic mitosene