Vesicles and Micelles from Amphiphilic Zinc(II)–Cyclen Complexes as Highly Potent Promoters of Hydrolytic DNA Cleavage

Abstract

Phosphate esters are essential to any living organism and their specific hydrolysis plays an important role in many metabolic processes. As phosphodiester bonds can be extraordinary stable, as in DNA, great effort has been put into mimicking the active sites of hydrolytic enzymes which can easily cleave these linkages and were often found to contain one or more coordinated metal ions. With this in mind, we report micellar and vesicular Zn(II)-cyclen complexes which considerably promote the hydrolytic cleavage of native DNA and the activated model substrate bis(4-nitrophenyl)phosphate (BNPP). They are formed by self-assembly from amphiphilic derivatives of previously employed complexes in aqueous solution and therefore allow a simple and rapid connection of multiple active metal sites without great synthetic effort. Considering the hydrolytic cleavage of BNPP at 25 °C and pH 8, the micellar and vesicular metal catalysts show an increase of second-order rate constants (k(2)) by 4-7 orders of magnitude compared to the unimolecular complexes under identical conditions. At neutral pH, they produce the highest k(2) values reported so far. For pBR322 plasmid DNA, both a conversion of the supercoiled to the relaxed and linear form, and also a further degradation into smaller fragments by double strand cleavages could be observed after incubation with the vesicular Zn(II)-complexes. Finally, even the cleavage of nonactivated single-stranded oligonucleotides could be considerably promoted compared to background reaction.

Kemp elimination in cationic micelles: designed enzyme‐like rates achieved through the addition of long‐chain bases

“…Thus, our results suggest that relatively loose and non‐specific interactions with the substrate can provide at least four orders of magnitude rate acceleration even in a non‐hydrophobic environment when the catalytic base is easily accessible. This rate acceleration is larger than the approximately 20‐fold rate accelerations measured for hydrolyses of benzoyl chlorides and benzenesulfonyl chlorides in the presence of CTAC, and of the 30‐ and 100‐fold measured for hydrolyses of aromatic phosphate triesters and diesters in CTAC; in fact, it is more similar to the 10 5 ‐fold rate accelerations achieved by metallomicelles …”

Photo-induced secondary assembly of bis(terpyridyl)dibenzo-24-crown-8/Zn2+ supramolecular polymer

“…In addition, the slope of viscosity/concentration plot of 1/Zn system gave a slope of 1.08 at the low concentration range, but this value rapidly increased to 2.37 at the higher concentration range (Fig. 4) [35]. These phenomena, along with the clear Tyndall effect (Fig.…”

An Anionic Surfactant Metallomicelle: Catalytic Activity and Mechanism for the Catalytic Hydrolysis of a Phosphate Ester

“…The results also indicate that the rate of catalytic hydrolysis of BNPP is ca six times greater in the new metallomicellar system, made of the cerium(III) complex of the aza-crown ether ligand and anionic micelle, compared to that in our previously reported metallomicellar system made from the aza-crown ether, lanthanum(III) ion and CTAB cationic surfactant [22]. It is well-known that a micelle can play a very important role in the catalytic processes of enzymes owing to the effect of the associated high local concentration [25]. The cause may lie mainly in that the electrostatic effects of the micelles play a key role in the catalytic hydrolysis of BNPP, in another words, these effects are mainly dependent on the interaction between the micelle and the positively charged active species.…”