Rose bengal dye on thiol-terminated bilayer for molecular devices

Recently, it has become increasingly important to control molecular layers, especially with regard to the formation of bilayers, in order to avoid electrical shorts in molecular electronics. In this paper, we report on the characterization of an in situ thiol-terminated bilayer that is formed by hydrogen bonding between the amine group of an aminoalkanethiol monolayer on a gold surface and the free amine group of aminoalkanethiolates in a bulk solution. We also report on the use of a rose bengal (RB) monolayer on a thiol-terminated bilayer for the purpose of application in a molecular memory device. Using surface-sensitive techniques such as grazing angle Fourier transform infrared (FT-IR) spectroscopy, quartz crystal microbalance (QCM) measurement, ellipsometry, X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV), we characterized a thiol-terminated bilayer (TUA-AUT) and an RB functionalized monolayer on a bilayered surface (RB-TUA-AUT). For a control experiment, we prepared a single RB monolayer attached by an ethanethiol group to a gold surface. In order to assess the feasibility of the present approach with respect to application in molecular electronics, we tested the switching property of the self-assembled monolayers (SAMs) using conducting-probe atomic force microscopy (CP-AFM). The RB monolayer on the bilayered surface exhibited hysteresis, while a single RB monolayer gave an electrical short.     

Strikingly High Activity of 15-Lipoxygenase Towards Di-Polyunsaturated Arachidonoyl/Adrenoyl-Phosphatidylethanolamines Generates Peroxidation Signals of Ferroptotic Cell Death

The vast majority of membrane phospholipids (PLs) include two asymmetrically positioned fatty acyls: oxidizable polyunsaturated fatty acids (PUFA) attached predominantly at the sn2 position, and non-oxidizable saturated/monounsaturated acids (SFA/MUFA) localized at the sn1 position. The peroxidation of PUFA-PLs, particularly sn2-arachidonoyl(AA)- and sn2-adrenoyl(AdA)-containing phosphatidylethanolamines (PE), has been associated with the execution of ferroptosis, a program of regulated cell death. There is a minor subpopulation (≈1–2 mol %) of doubly PUFA-acylated phospholipids (di-PUFA-PLs) whose role in ferroptosis remains enigmatic. Here we report that 15-lipoxygenase (15LOX) exhibits unexpectedly high pro-ferroptotic peroxidation activity towards di-PUFA-PEs. We revealed that peroxidation of several molecular species of di-PUFA-PEs occurred early in ferroptosis. Ferrostatin-1, a typical ferroptosis inhibitor, effectively prevented peroxidation of di-PUFA-PEs. Furthermore, co-incubation of cells with di-AA-PE and 15LOX produced PUFA-PE peroxidation and induced ferroptotic death. The decreased contents of di-PUFA-PEs in ACSL4 KO A375 cells was associated with lower levels of di-PUFA-PE peroxidation and enhanced resistance to ferroptosis. Thus, di-PUFA-PE species are newly identified phospholipid peroxidation substrates and regulators of ferroptosis, representing a promising therapeutic target for many diseases related to ferroptotic death.     

Urea nitrate and nitrourea: powerful and regioselective aromatic nitration agents

Urea nitrate (UN) and nitrourea (NU), easily prepared from urea and nitric acid, convert deactivated aromatic compounds to the corresponding nitrated derivatives with a high yield and a high regioselectivity under very mild conditions. The performance of the two reagents is quite similar indicating that NU is an intermediate in the UN nitration process.     

Anionic oligomerization of dimethyl itaconate

Methanolic solutions of alkali metal and magnesium methoxides were used as initiators for the oligomerization of dimethyl itaconate in methanol, DMF and DMSO. The yield of oligomers was higher in the aprotic solvents. The oligomeric mixtures contained a preponderance of trimer, the structure of which was elucidated by mass spectrometry as a cyclohexane derivative. The oligomers contained no methoxyl end-groups, and initiation is postulated to be an acid-base reaction, in which the allylic hydrogen α- to the carbonyl is abstracted. This belief was supported by the fact that the use of sodium naphthalene and triethylamine as initiators gave the same oligomers. The trimer was tested as a plasticizer.     

Carbon-13 n.m.r. of the 8-phosphabicyclo[3.2.1]octane system

¹³C Chemical shifts and ¹³C? ³¹P nuclear spin coupling constants have been determined for 26 8-phosphabicyclo[3.2.1]octane derivatives, namely phosphines, phosphine oxides, phosphine sulphides and one phosphonium salt. The influence of the phosphorus configuration on δ and ²J(PC) values was examined and other factors influencing the ²J(PC) coupling constant are discussed.     

Direct evidence for the hydroxide extraction mechanism in the phase transfer catalyzed cyclopropanation of 4-halobutyronitrile in a solid-liquid system

The Hoffman degradation reaction is proposed as an unequivocal proof for the validity of the extraction mechanism in Phase Transfer Catalysis (PTC) in the presence of solid NaOH. 4-Chlorobutyronitrile is found to yield cyclopropyl cyanide via an extraction route while 4-bromobutyronitrile reacts to form the same product by the prevalent interfacial mechanism.     

Structure of swinholide-a,a new macrolide from the marine sponge theonella swinhoei

Swinholide-A ($\text{1}$a) a novel 22-membered macrolide has been isolated from a Red Sea sponge. The structure of the tetraformate ($\text{1b}$) has been determined on basis of spectral data using 2D-NMR correlations.     

Attempted acid-catalyzed transannular reactions in the cembranoids

Several cembrane diterpenes were treated by various acids under different experimental conditions. All tested compounds were found to be acid sensitive, leading either to local chemical transformations (e.g. opening of epoxides), to transannular reactions and/or to unidentified mixtures. Sarcophine (7), the principal cembrane tested, was found to afford either all types of possible epoxide opening products (11–22), or, by a transannular reaction, when treated with SnCl₄, two tetrahydrooxepine derivatives (23 and 24). The structure determination of the various derivatives of sarcophine was based mainly on the ¹H and ¹³C-NMR spectra and also on several chemical transformations.Flaccidoxide (8), another cembranoid examined, was found to yield, with Zn/Cu couple, the expected deoxygenation product (sarcophytol-B, 32) together with an unexpected transannular reaction product (33). The structure, including the stereochemistry, of the latter THF-derivative of 8 (33) was elucidated by NMR and chemical reactions.