Degree Of N-methylation Research Articles

Complexation of C-Functionalized Cyclams with Copper(II) and Zinc(II): Similarities and Changes When Compared to Parent Cyclam Analogues.

Herein, we report a comprehensive coordination study of the previously reported ligands cyclam, CB-cyclam, TMC, DMC, and CB-DMC and of their C-functional analogues, cyclam-E, CB-cyclam-E, TMC-E, DMC-E, and CB-DMC-E. This group of ligands includes cyclam, cross-bridged cyclams, their di- or tetramethylated derivatives, and the analogues bearing an additional hydroxyethyl group on one β-N position of the ring. The Cu(II) and Zn(II) complexes of these macrocycles have been highlighted previously for the biological interest, but the details of their structures in the solid state and in solution remained largely unexplored. In particular, we analyzed the impact that adding noncoordinating N-methyl and C-hydroxyethyl functionalities has in the structures of the complexes. All the Cu(II) and Zn(II) complexes were synthesized and investigated using single crystal X-ray diffraction and NMR, electronic absorption, and EPR spectroscopies, along with DFT studies. Dissociation kinetics experiments in acidic conditions and electrochemical studies were also performed. Special attention was paid to analyze the different configurations present in solution and in the solid state, as well as the impact of the C-appended hydroxyethyl group on the coordination behavior. Various ratios of the trans-I, trans-III, and cis-V configurations have been observed depending on the degree of N-methylation and the presence of the ethylene cross-bridge.

Nanoparticles of Quaternary Ammonium Polyethylenimine Derivatives for Application in Dental Materials.

Various quaternary ammonium polyethylenimine (QA-PEI) derivatives have been synthesized in order to obtain nanoparticles. Due to their antibacterial activity and non-toxicity towards mammalian cells, the QA-PEI nanoparticles have been tested extensively regarding potential applications as biocidal additives in various dental composite materials. Their impact has been examined mostly for dimethacrylate-based restorative materials; however, dental cements, root canal pastes, and orthodontic adhesives have also been tested. Results of those studies showed that the addition of small quantities of QA-PEI nanoparticles, from 0.5 to 2 wt.%, led to efficient and long-lasting antibacterial effects. However, it was also discovered that the intensity of the biocidal activity strongly depended on several chemical factors, including the degree of crosslinking, length of alkyl telomeric chains, degree of N-alkylation, degree of N-methylation, counterion type, and pH. Importantly, the presence of QA-PEI nanoparticles in the studied dental composites did not negatively impact the degree of conversion in the composite matrix, nor its mechanical properties. In this review, we summarized these features and functions in order to present QA-PEI nanoparticles as modern and promising additives for dental materials that can impart unique antibacterial characteristics without deteriorating the products’ structures or mechanical properties.

Physicochemical characteristics and in vitro release from oil-based vehicles of peptidomimetics: parenteral depots for intra-articular administration

Results: Basic physicochemical properties including their apparent solubility in aqueous buffer and vegetable oils of a series of 11 peptidomimetics varying with respect to chain length and degree of N-methylation were estimated. It was observed that the compounds in contact with water transformed into sticky, slowly dissolving semisolid materials. Based on these observations, the in vitro release behavior of selected peptide derivatives from oil solutions and in situ formed precipitates was investigated using a validated in vitro release model. Conclusion: The results of this investigation suggest that both types of oil-based drug delivery systems might constitute alternative sustained release formulation principles of such amorphous peptide derivatives for the intra-articular route of administration.

Effects of Acidity and Methylation on the UV and Fluorescence Spectra of Poly(pyridine)s in Aqueous Acidic Solutions and in the Solid State

Poly(2,5-pyridine) and poly(3,5-pyridine) were synthesized by coupling polymerization of 2,5- and 3,5-dibromopyridine, respectively. Partially N-methylated poly(2,5-pyridine)s were prepared with a degree of N-methylation per repeating unit from 10 to 25%. UV spectra and fluorescence were studied in aqueous acidic solutions and in the solid state. The UV absorption maximum of poly(2,5-pyridine) is blue-shifted with increasing acidity and/or degree of N-methylation; however, the UV absorption maximum of poly(3,5-pyridine) does not change with the acidity of the solution. Fluorescence emission intensities of poly(2,5-pyridine) and poly(3,5-pyridine) increase with increasing acidity sharply up to Ho (Hammett acidity function) = −10.1. The fluorescence emission of poly(2,5-pyridine) is also enhanced by N-methylation. Protonated and N-methylated pyridines in poly(pyridine) are the fluorescence active species. The fluorescence emission maximum of poly(2,5-pyridine) shifts from 420 nm in dilute HCOOH solution to 520 nm in the solid state. Homogeneous films of poly(2,5-pyridine) with poly(vinyl alcohol) can be obtained by spin coating from the blended solutions. The longer wavelength emission (520 nm) which became dominant in blends containing more than 10 mol % of poly(2,5-pyridine) was assigned to an emission of excimer. However, when a highly protonated poly(2,5-pyridine) was blended with poly(vinyl alcohol), an intense 420 nm emission appeared and became dominant, since excimer formation was inhibited by intermolecular electrostatic repulsion. It is proposed that two blue electroluminescence (420 and 520 nm) devices based on poly(pyridine) can be constructed by varying the degree of protonation or N-methylation and controlling the composition of the blends of poly(2,5-pyridine) with appropriate polymers.

Rhizobium tropici nodulation factor sulfation is limited by the quantity of activated form of sulfate

Rhizobium tropici is a broad host-range symbiont of Phaseolus vulgaris. This bacterium produces a mixture of sulfated and non-sulfatedN-methylated pentameric nodulation (Nod) factors. To understand the genetic bases of the partial sulfation of R. tropici Nod factors, which might be involved in the broad host-range of this species, we introduced in R. tropici CFN299 the recombinant plasmid pGMI515 carrying a set of nodulation ( nod) genes of R. meliloti, including those involved in the sulfation of R. meliloti Nod factors. The CFN299 (pGMI515) transconjugant produced only sulfated Nod factors, but approximately half of them were no moreN-methylated. Mutations in R. meliloti nodH gene did not decrease the Nod factor sulfation whereas inactivation of the nodPQ genes restored the production of a mixture of sulfated and non-sulfated molecules. These results suggest that the limiting step in R. tropici Nod factor sulfation is the production of activated sulfate donors. Mutations in the R. meliloti nodFEG and nodH genes did not change theN-methylation pattern, whereas mutations in nodPQ increased the degree ofN-methylation, suggesting a metabolic link between sulfation and methylation of R. tropici Nod factors.