The CaCo-2 cell junction derangement exerted by the single addition of oxysterols commonly detected in foods is markedly quenched when they are in mixture.

The selective permeability of the gut epithelial barrier is heavily reliant on the stability of cell junctions, often challenged by a variety of dietary stressors, including non-enzymatic cholesterol oxidation products (COPs). A marked decrease of the tight junctions claudin-1 and occludin, and of the adherens junction E-cadherin was previously detected in differentiated CaCo-2 monolayers challenged by a single addition of 7β-hydroxycholesterol (7βOHC) or 7-ketocholesterol (7KC) in the lowest micromolar range. However, in the diet, oxysterols are occurring in a mixture.

Mechanism of Solid-State H Photochemically Induced Dynamic Nuclear Polarization in a Synthetic Donor-Chromophore-Acceptor at 0.3 T.

H photochemically induced dynamic nuclear polarization (photo-CIDNP) has recently emerged as a tool to enhance bulk H nuclear magnetic resonance (NMR) signals in solids at magnetic fields ranging from 0.3 to 21.1 T, using synthetic donor-chromophore-acceptor (D-C-A) molecules as optically active polarizing agents (PAs).

Light-Induced H NMR Hyperpolarization in Solids at 9.4 and 21.1 T.

The inherently low sensitivity of nuclear magnetic resonance (NMR) spectroscopy is the major limiting factor for its application to elucidate structure and dynamics in solids. In the solid state, nuclear spin hyperpolarization methods based on microwave-induced dynamic nuclear polarization (DNP) provide a versatile platform to enhance the bulk NMR signal of many different sample formulations, leading to significant sensitivity improvements. Here we show that H NMR hyperpolarization can also be generated in solids at high magnetic fields by optical irradiation of the sample.

Magic Angle Spinning Solid-State C Photochemically Induced Dynamic Nuclear Polarization by a Synthetic Donor-Chromophore-Acceptor System at 9.4 T.

Solid-state photochemically induced dynamic nuclear polarization (photo-CIDNP) is a nuclear magnetic resonance spectroscopy technique in which nuclear spin hyperpolarization is generated upon optical irradiation of an appropriate donor-acceptor system. Until now, solid-state photo-CIDNP at high magnetic fields has been observed only in photosynthetic reaction centers and flavoproteins. In the present work, we show that the effect is not limited to such biomolecular samples, and solid-state C photo-CIDNP can be observed at 9.

Probing Homogeneous Catalysts and Precatalysts in Solution by Exchange-Mediated Overhauser Dynamic Nuclear Polarization NMR.

Triphenylphosphine (PPh) is a ubiquitous ligand in organometallic chemistry that has been shown to give enhanced P NMR signals at high magnetic field via a scalar-dominated Overhauser effect dynamic nuclear polarization (OE DNP). However, PPh can only be polarized via DNP in the free form, while the coordinated form is DNP-inactive. Here, we demonstrate the possibility of enhancing the P NMR signals of coordinated PPh in metal complexes in solution at room temperature by combining Overhauser effect DNP and chemical exchange between the free and coordinated PPh forms.