Insights into the Electronic Structure of CuII Bound to an Imidazole Analogue of Westiellamide

A Biophysical Study of Ru(II) Polypyridyl Complex, Properties and its Interaction with DNA

Mononuclear Ru(II)Polypyridyl complexes of type [Ru(A)₂BPIIP] (ClO₄)₂.2H₂O, where BPIIP = 2-(3-(4-bromophenyl)isoxazole-5-yl)-1 H-imidazo [4,5-f] [1, 10] phenanthroline and A = bpy = bipyridyl (1), phen = 1,10 Phenanthroline (2), dmb = 4, 4' -dimethyl 2, 2'- bipyridine (3) & dmp = 4,4'-dimethyl-1,10 -Ortho Phenanthroline (4), were synthesized and their antibacterial activity were examined. The synthesized complexes were characterized and their interaction with DNA was studied using Computational and Biophysical methods (Absorption, emission methods, and viscosity). Molecular modelling studies were carried out for molecular geometry and electronic properties (Frontier molecular orbital HOMO-LUMO). The electrostatic potential surface contours for the complexes were analysed to give their nucleophilic level of sensitivity. The study reveals that the Ru(II) Polypyridyl complexes bind to DNA preponderantly by intercalation. The results recommend that the phen and dmp complex have more effective binding ability than the bpy and dmb, indicating the role of the ancillary ligand in determining their specificity for DNA binding. Further molecular docking studies suggested an octahedral geometry and bind to DNA by preferential binding to Guanine. The docking study additionally sustains the binding constant data acquired with the absorption and emission techniques.The results reveal that the nature of the ancillary Ligand plays a considerable role for the intercalation of the Ru(II) polypyridyl complex to DNA, which subsequently influences the antibacterial activity. Biological studies conducted on Gram-Negative (E.coli and K.pneumonia) and Gram-Positive (S. aureus and E. faecalis) bacteria establish that complex 1 and 2 were considerably active against S. aureus and E. coli.

Possible Functional Roles of Patellamides in the Ascidian-Prochloron Symbiosis

Patellamides are highly bioactive compounds found along with other cyanobactins in the symbiosis between didemnid ascidians and the enigmatic cyanobacterium Prochloron. The biosynthetic pathway of patellamide synthesis is well understood, the relevant operons have been identified in the Prochloron genome and genes involved in patellamide synthesis are among the most highly transcribed cyanobacterial genes in hospite. However, a more detailed study of the in vivo dynamics of patellamides and their function in the ascidian-Prochloron symbiosis is complicated by the fact that Prochloron remains uncultivated despite numerous attempts since its discovery in 1975. A major challenge is to account for the highly dynamic microenvironmental conditions experienced by Prochloron in hospite, where light-dark cycles drive rapid shifts between hyperoxia and anoxia as well as pH variations from pH ~6 to ~10. Recently, work on patellamide analogues has pointed out a range of different catalytic functions of patellamide that could prove essential for the ascidian-Prochloron symbiosis and could be modulated by the strong microenvironmental dynamics. Here, we review fundamental properties of patellamides and their occurrence and dynamics in vitro and in vivo. We discuss possible functions of patellamides in the ascidian-Prochloron symbiosis and identify important knowledge gaps and needs for further experimental studies.

An azobenzene container showing a definite folding - synthesis and structural investigation

The combination of photo-switchable units with macrocycles is a very interesting field in supramolecular chemistry. Here, we present the synthesis of a foldable container consisting of two different types of Lissoclinum macrocyclic peptides which are connected via two azobenzene units. The container is controllable by light: irradiation with UV light causes a switching process to the compact cis,cis-isomer, whereas by the use of visible light the stretched trans,trans-isomer is formed. By means of quantum chemical calculations and CD spectroscopy we could show that the trans→cis isomerization is spatially directed; that means that one of the two different macrocycles performs a definite clockwise rotation to the other, caused by irradiation with UV light. For the cis→trans isomerization counterclockwise rotations are found. Furthermore, quantum chemical calculations reveal that the energy of the cis,cis-isomer is only slightly higher than the energy of the cis,trans-isomer. This effect can be explained by the high dispersion energy in the compact cis,cis-isomer.

Dinuclear ZnII and mixed CuII-ZnII complexes of artificial patellamides as phosphatase models

The patellamides (cyclic pseudo-octapeptides) are produced by Prochloron, a symbiont of the ascidians, marine invertebrate filter feeders. These pseudo-octapeptides are present in the cytoplasm and a possible natural function of putative metal complexes of these compounds is hydrolase activity, however the true biological role is still unknown. The dinuclear Cu^II complexes of synthetic patellamide derivatives have been shown in in vitro experiments to be efficient hydrolase model catalysts. Many hydrolase enzymes, specifically phosphatases and carboanhydrases, are Zn^II-based enzymes and therefore, we have studied the Zn^II and mixed Zn^II/Cu^II solution chemistry of a series of synthetic patellamide derivatives, including solution structural and computational work, with the special focus on model phosphatase chemistry with bis-(2,4-dinitrophenyl)phosphate (BDNPP) as the substrate. The Zn^II complexes of a series of ligands are shown to form complexes of similar structure and stability compared to the well-studied Cu^II analogues and the phosphatase reactivities are also similar. Since the complex stabilities and phosphatase activities are generally a little lower compared to those of Cu^II and since the concentration of Zn^II in Prochloron cells is slightly smaller, we conclude that the Cu^II complexes of the patellamides are more likely to be of biological importance.