Consistent treatment of coherent and incoherent energy transfer dynamics using a variational master equation

We investigate the energy transfer dynamics in a donor-acceptor model by developing a time-local master equation technique based on a variational transformation of the underlying Hamiltonian. The variational transformation allows a minimisation of the Hamiltonian perturbation term dependent on the system parameters, and consequently results in a versatile master equation valid over a range of system-bath coupling strengths, temperatures, and environmental spectral densities. While our formalism reduces to the well-known Redfield, F?rster and polaron forms in the appropriate limits, in general it is not equivalent to perturbing in either the system-environment or donor-acceptor coupling strengths, and hence can provide reliable results between these limits as well. Moreover, we show how to include the effects of both environmental correlations and non-equilibrium preparations within the formalism.     

Twisted Baskets

A preparative procedure for obtaining a pair of twisted molecular baskets, each comprising a chiral framework with either right ((P)‐ 1 _syn) or left ((M)‐ 1 _syn) sense of twist and six ester groups at the rim has been developed and optimized. The racemic (P/M)‐ 1 _syn can be obtained in three synthetic steps from accessible starting materials. The resolution of (P/M)‐ 1 _syn is accomplished by its transesterification with (1R,2S,5R)‐(?)‐menthol in the presence of a Ti^IV catalyst to give diastereomeric 8 ^P and 8 ^M . It was found that dendritic‐like cavitands 8 ^P and 8 ^M , in CD₂Cl₂, undergo self‐inclusion (¹H NMR spectroscopy) with a menthol moiety occupying the cavity of each host. Importantly, the degree of inclusion of the menthol group was (¹H NMR spectroscopy) found to be greater in the case of 8 ^P than 8 ^M . Accordingly, it is suggested that different folding characteristic of 8 ^P and 8 ^M ought to affect the physicochemical characteristics of the hosts to permit their effective separation by column chromatography. The absolute configuration of 8 ^P/ 8 ^M , encompassing right‐ and left‐handed “cups”, was determined with the exciton chirality method and also verified in silico (DFT: B3LYP/TZVP). Finally, the twisted baskets are strongly fluorescent due to three naphthalene chromophores, having a high fluorescence quantum yield within the rigid framework of 8 ^P/ 8 ^M .     

An Assessment of the Utility of Tissue Smears in Rapid Cancer Profiling with Desorption Electrospray Ionization Mass Spectrometry (DESI-MS)

Mass spectrometry imaging with desorption electrospray ionization mass spectrometry (DESI-MS) is used to characterize cancer from ex vivo slices of tissues. The process is time-consuming. The use of tissue smears for DESI-MS analysis has been proposed as it eliminates the time required to snap-freeze and section the tissue. To assess the utility of tissue smears for rapid cancer characterization, principal component analysis (PCA) was performed to evaluate the concordance between DESI-MS profiles of breast cancer from tissue slices and smears prepared on various surfaces. PCA suggested no statistical discrimination between DESI-MS profiles of tissue sections and tissue smears prepared on glass, polytetrafluoroethylene (PTFE), and porous PTFE. However, the abundances of cancer biomarker ions varied between sections and smears, with DESI-MS analysis of tissue sections yielding higher ion abundances of cancer biomarkers compared with smears. Coefficient of variance (CV) analysis suggests DESI-MS profiles from tissue smears are as reproducible as the ones from tissue sections. The limit of detection with smear samples from single pixel analysis is comparable to tissue sections that average the signal from a tissue area of 0.01 mm². The smears prepared on the PTFE surface possessed a higher degree of homogeneity compared with the smears prepared on the glass surface. This allowed single MS scans (~1 s) from random positions across the surface of the smear to be used in rapid cancer typing with good reproducibility, providing pathologic information for cancer typing at speeds suitable for clinical utility.

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Flavonoids: biological activities and therapeutic potential

Abstract

Flavonoids have aroused much interest in research, since they present a great diversity of biological activities observed in vitro, such as: antioxidant effect, modulation of the enzymatic activity and inhibition of cellular proliferation, exerting beneficial effects on the organism, as well as the use of its therapeutic potential. With wide distribution in the plant kingdom represent a class of phenolic compounds that differ in their chemical structure and particular characteristics. The objective of this review was to describe the relevant aspects of flavonoids, reporting the different known groups, the probable mechanisms by which they act, their pharmacological properties and to gain a better understanding of the reported beneficial health effects of these substances. This systematic review consisted of research using scientific databases such as Scopus, Science Direct, PubMed, SciVerse and SciELO, without time limitation. Some pharmacological properties of some flavonoids and their health benefits have been confirmed by previous studies.     

New coumarin derivatives from Ferula pseudalliacea with antibacterial activity

In this study, the antibacterial activity of disesquiterpene coumarin and sesquiterpene coumarins obtained from Ferula pseudalliacea roots was evaluated by determination of minimum inhibitory concentration using the broth micro-dilution method against seven pathogenic bacterial strains (Staphylococcus aureus ATCC 25,923, vancomycin resistant clinical strain of Enterococcus faecium, Bacillus cereus PTCC 1015, Escherichia coli ATCC 25,922, Pseudomonas aeruginosa PTCC 1430, clinical strain of Klebsiella pneumoniae and a clinical strain of Helicobacter pylori). The overall inhibitory activities of the compounds were higher against Gram positive tested bacteria. Sanandajin and ethyl galbanate demonstrated significant activity against H. pylori strain, as well as S. aureus strain in concentration of 64 μg/ml. Methyl galbanate inhibited vancomycin resistant strain of E. faecium in concentration of 64 μg/ml. The results of the present investigation indicated that disesquiterpene and sesquiterpene coumarins isolated from F. pseudalliacea root extract can be considered as potent antibacterial agents for pharmaceutical and food industries.     

Chemical composition and antioxidant activity of the essential oil of aerial parts of Petasites albus from Iran: a good natural source of euparin

The chemical composition of the essential oil of Petasites albus (known as 'Baba Adam' in Iran) was investigated by capillary gas chromatography and gas chromatography-mass spectrometry for the first time. Twenty components were identified, accounting for 99.7% of the oil composition. The major compounds were euparin (73%), α-eudesmol (13.2%) and β-selinene (4.5%). Euparin, the main component of the essential oil, was isolated and characterised by spectroscopic techniques. The antioxidant activities of the essential oil and euparin were evaluated by using the 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay and are shown to exhibit a moderate antioxidant activity.     

Unexpected regioselectivity observed in the bromination and epoxidation reactions of p-benzoquinone-fused norbornadiene: An experimental and computational study

The bromination reaction of p-benzoquinone-fused norbornadiene was studied at various temperatures (?78, ?50, 0, 25, and 77 °C). At room temperature, the double bonds of the p-benzoquinone units were mainly brominated. The double bond of the norbornene unit also underwent a bromination reaction in a yield of only 2%. However, the reaction at ?78 °C resulted in the formation of products derived from the attack of bromine on the norbornene double bond with higher charge density. In contrast to the bromination reaction, the epoxidation reaction of the same compound with m-chloroperbenzoic acid and dimethyldioxirane exclusively resulted in the formation of products derived from the addition to the double bond of norbornadiene. The regioselectivity observed was investigated and the results were supported by theoretical calculations.     

Kamonolol acetate from Ferula pseudalliacea as AChE inhibitor: in vitro and in silico studies

Structural Chemistry - Alzheimer’s disease is one of the most common causes of dementia. Acetylcholinesterase has been considered as the main therapeutic target in the treatment of...