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A series of non-innocent halogen substituted Schiff base vanadium catecholates were added with different electron donating and withdrawing substituents on the catecholates to investigate the electronic effects on the properties of this class of compounds. We hypothesized that the electronic changes would be reflected in their redox properties and stabilities, which should lead to differences in their biological properties. Using UV-spectroscopy, we measured their hydrolytic stability, and using electrochemistry, we characterized their redox properties. Adding one substituent on the catecholate group on the complexes changed the redox potentials of the complexes; however, less impact on the hydrolytic stability was observed. We discovered that hydrolytic stability was crucial to the anti-proliferative effects on glioblastoma cells, and most of these compounds had effects similar to vanadates regardless of their different redox properties. Hence, we could not determine the importance of changing the electronic properties and redox potential on the anti-proliferative effects of mono-substituted catecholates. However, the studies did show that the pKa of the substituted catecholate showed a linear correlation with the redox potential of the non-innocent Schiff base vanadium complexes, which will be important in future investigations into this class of complexes. [ABSTRACT FROM AUTHOR]

Menaquinones are lipoquinones that consist of a headgroup (naphthoquinone, menadione) and an isoprenyl sidechain. They function as electron transporters in prokaryotes such as Mycobacterium tuberculosis. For these studies, we used Langmuir monolayers and microemulsions to investigate how the menaquinone headgroup (menadione) and the menahydroquinone headgroup (menadiol) interact with model membrane interfaces to determine if differences are observed in the location of these headgroups in a membrane. It has been suggested that the differences in the locations are mainly caused by the isoprenyl sidechain rather than the headgroup quinone-to-quinol reduction during electron transport. This study presents evidence that suggests the influence of the headgroup drives the movement of the oxidized quinone and the reduced hydroquinone to different locations within the interface. Utilizing the model membranes of microemulsions and Langmuir monolayers, it is determined whether or not there is a difference in the location of menadione and menadiol within the interface. Based on our findings, we conclude that the menadione and menadiol may reside in different locations within model membranes. It follows that if menaquinone moves within the cell membrane upon menaquinol formation, it is due at least in part, to the differences in the properties of headgroup interactions with the membrane in addition to the isoprenyl sidechain. Key words: menaquinone, menadione, menadiol, Langmuir monolayer, reverse micelle. Les menaquinones sont des lipoquinones formees d'un groupement de tete (naphtoquinone, menadione) et d'une chaine laterale isoprenyle. Elles servent de transporteurs d'electrons dans les procaryotes tels que Mycobacterium tuberculosis. Dans le cadre des presents travaux, nous avons employe des monocouches de Langmuir et des microemulsions pour etudier la maniere dont le groupement de tete de la menaquinone (la menadione) et le groupement de tete de la menahydroquinone (le menadiol) interagissent avec les interfaces du modele membranaire. Cette etude avait pour but de determiner si des differences peuvent etre decelees quant aux endroitsou ces groupementsde tete se situent a l'interieur d'une membrane. L'hypothese selon laquelle ces differences de position seraient essentiellement attribuables a la chaine laterale plutot qu'a la reduction de la quinone en quinol durant le transport d'electrons a ete posee. Cette etude presente des elements qui tendent a demontrer que la quinone oxydee et l'hydroquinone reduite se deplacent a des endroits differents dans la membrane cellulaire, et ce, sans influence de la chaine laterale. A l'aide de membranes modeles de microemulsions et de monocouches de Langmuir, nous avons pu determiner s'il y avait ou non une difference de position entre la menadione et le menadiol dans la membrane. Nos resultats ont permisdeconclure quela menadioneet lemenadiol peuvent se situerades endroits differents dans les membranes modeles. Par consequent, si la menaquinone sedeplace dans la membrane cellulaire lorsqu'elle se transforme en menaquinol, ce deplacement est attribuable non seulement a la chaine isoprenyle, mais aussi, du moins en partie, a la difference des proprietes des interactions entre le groupement de tete et la membrane. [Traduit par la Redaction] Mots-cles : menaquinone, menadione, menadiol, monocouche de Langmuir, micelle inversee., 1. Introduction Lipoquinones are an essential group of lipids that act as electron transfer donors and acceptors within the electron transfer complex (.1,2) One type of lipoquinone typically associated with [...]