Resolving NMR signals of short‐chain fatty acid mixtures using unsupervised component analysis

Nuclear magnetic resonance (NMR) is a very powerful instrumental technique suited to identify and characterize organic compounds. NMR has been successfully used in the analysis of complex biological and environmental samples; however, these applications are still rather limited. In this work, we describe unsupervised component analysis as a multivariate unsupervised method suited to identify the number of relevant NMR signal contributions and to deconvolve mixed signals into signal individual sources and respective contributions. Using this approach, we were able to advance further in the field of quantification of NMR spectra, and this methodology will help in the characterization of complex biological samples. Copyright © 2017 John Wiley & Sons, Ltd.     

Inhibition of methicillin resistant Staphylococcus aureus by a plasma needle

In numerous recent papers plasma chemistry of non equilibrium plasma sources operating at atmospheric pressure has been linked to plasma medical effects including sterilization. In this paper we present a study of the effectiveness of an atmospheric pressure plasma source, known as plasma needle, in inhibition of the growth of biofilm produced by methicillin resistant Staphylococcus aureus (MRSA). Even at the lowest powers the biofilms formed by inoculi of MRSA of 10⁴ and 10⁵ CFU have been strongly affected by plasma and growth in biofilms was inhibited. The eradication of the already formed biofilm was not achieved and it is required to go to more effective sources.     

β‐Cyclodextrin Duplexes That Are Connected through Two Disulfide Bonds: Potent Hosts for the Complexation of Organic Molecules

New tubular host molecules, which are composed of two β‐cyclodextrin macrocycles that are connected through two disulfide bonds, have been prepared by the air‐promoted oxidation of 6^I,6^IV‐dideoxy‐6^I,6^IV‐disulfanyl‐β‐cyclodextrin in aqueous solution. This reaction leads to three products: monomeric intramolecular disulfide and two dimeric species, which are termed as “non‐eclipsed” and “eclipsed” cyclodextrin duplexes. Oxidation at a concentration of the starting thiol of 0.1 mM gave the intramolecular disulfide as the major product whereas a concentration in the millimolar range afforded the dimeric species as the dominant products. The tubular structure of the “non‐eclipsed” isomer was unequivocally determined by X‐ray analysis. The binding affinities of the duplexes to a wide range of compounds, including fluorescent dyes and clinically used drugs Imatinib and Esomeprazol, were studied in water by ITC. For most guest compounds, the experimentally determined K_a values were in the range 10⁷–10⁸ M ^?1. These binding affinities are significantly higher than those found in the literature for analogous complexes with native cyclodextrins. In cases of binding of neutral or anionic guest molecules cyclodextrin duplexes outperformed cucurbiturils. A complex between a duplex and Nile blue was used to investigate its ability to penetrate the cytoplasmic membrane of HeLa cells. We found that the complex accumulated in the cell membrane but did not pass into cytosol. Importantly, the complex did not decompose to a significant extent under high dilution in the cellular environment.     

In Situ FTIR and NMR Spectroscopic Investigations on Ruthenium‐Based Catalysts for Alkene Hydroformylation

Homogeneous ruthenium complexes modified by imidazole‐substituted monophosphines as catalysts for various highly efficient hydroformylation reactions were characterized by in situ IR spectroscopy under reaction conditions and NMR spectroscopy. A proper protocol for the preformation reaction from [Ru₃(CO)₁₂] is decisive to prevent the formation of inactive ligand‐modified polynuclear complexes. During catalysis, ligand‐modified mononuclear ruthenium(0) carbonyls were detected as resting states. Changes in the ligand structure have a crucial impact on the coordination behavior of the ligand and consequently on the catalytic performance. The substitution of CO by a nitrogen atom of the imidazolyl moiety in the ligand is not a general feature, but it takes place when structural prerequisites of the ligand are fulfilled.