13C Nmr Spectroscopy in Macromolecular Systems of Biochemical Interest

Sulfur- and Selenium-Containing Compounds Derived from Natural and Synthetic Sources in Angiogenesis Modulation.

Local environments for Cs(1) and Cs(2) sites in a perovskite Cs2CoBr4 single crystal with a dominant magnetic type based on the observed spin-lattice relaxation time

Nuclear Magnetic Resonance (NMR) relaxometry has emerged as a complementary tool in food metabolomics to investigate molecular dynamics beyond conventional spectral analysis. In coffee systems, longitudinal (T₁) and transverse (T₂) relaxation times provide insights into molecular movements and interactions relevant to flavor and aroma development during brewing. T₁ relaxation is primarily associated with slower molecular motion and bulk interactions, such as water mobility and lipid matrix organization on longer timescales. In contrast, T₂ relaxation is more sensitive to faster, localized molecular dynamics, including water-solute interactions, molecular confinement, and structural heterogeneity within the coffee matrix. These short-range dynamics are directly involved in the release, diffusion, and perception of volatile and non-volatile compounds, making T₂ relaxation more closely related to aroma intensity and flavor expression during extraction. This review summarizes the principles of NMR relaxation and its applications in various food matrices, with Arabica coffee discussed as a representative complex system. Methodological challenges, inconsistencies in reporting, and limitations in interpretation are highlighted. From a sustainability perspective, NMR relaxometry aligns with the principles of green analytical chemistry by enabling rapid, non-destructive analysis with minimal solvent consumption. Future directions toward standardized and meaningful relaxation-based NMR applications in coffee research are discussed.

Proton magnetic resonance second moments of triphenyltin fluoride, chloride, and hydroxide have been measured between 77 K and 530 K for the fluoride or the melting point for the chloride and hydroxide. Spin-lattice relaxation times have been obtained by pulse spectrometry over the same temperature ranges for these compounds as well as for triphenyltin bromide. The results are discussed in terms of three possible molecular motions: 180° jump reorientation of the phenyl groups about their Sn—C axes, other (probably fourfold) reorientation of the phenyl groups about the Sn—C bonds, and C3 reorientation of the triphenyltin group. The experimental results appear to agree best with a probably fourfold reorientatio of phenyl groups about the Sn—C bond in the case of the heat treated fluoride, and with a C3 reorientation of the whole molecule in the case of the chloride. The second moments of the hydroxide suggest a significantly different packing of molecules in the unit cell to that existing in the chloride. In other respects the behaviour of the hydroxide seems to resemble that of the fluoride. T1 values for chloride and bromide are similar.

Molecular motion in ultradispersed polytetrafluroethylene obtained by special gas-phase technology has been studied experimentally and theoretically based on a temperature dependence of the second moment of 19F NMR spectra and the time of spin-lattice relaxation. The results of observations are interpreted as the consequence of reorientation motion of CF2 groups around the axis of macromolecules at low temperature and of translational motion of macromolecules in the high temperature region. Qualitative differences from the molecular motion in industrial polytetrafluoroethylene (teflon-4) were detected and parameters of dynamic processes determined.

Miscibility, Morphology and Molecular Motion in Polymer Blends

NMR relaxation study of molecular motions in liquid chlorobenzotrifluorides

Synthesis of Macro-, Meso-, and Microporous Carbons from Natural and Synthetic Sources, and Their Application as Adsorbents for the Removal of Quaternary Ammonium Compounds from Aqueous Solution

Tyrosinase is a key enzyme for melanin biosynthesis and known to be sensitive to ultraviolet light in the presence of oxygen. Therefore, finding effective tyrosinase inhibitors, either from synthetic or natural sources, can be beneficial in the treatment of melanin-related disorders. We synthesized 4-(6-hydroxy-2-naphthyl)-1,3-bezendiol (HNB), a new family of hydroxyl substituted phenyl naphthalenes, as the isosteres of oxyresveratrol. This study investigated inhibitory effects of HNB on tyrosinase activity. HNB inhibited mushroom tyrosinase with an IC(50) value of 0.07 microM, which is more potent than the anti-tyrosinase activity of kojic acid (IC(50)=38.24), a well-known tyrosinase inhibitor. The kinetic analysis of tyrosinase inhibition revealed that HNB is a competitive inhibitor (K(i) 4.78 x 10(-9) M at 0.125 microM and K(i) 6.21 x 10(-9) M at 0.25 microM). We further found that HNB also inhibited melanin production in B16F10 melanoma cells (B16 cells). In addition to tyrosinase inhibiting activity, melanin biosynthesis was inhibited by HNB in the B16F10 cells. These data strongly suggest that HNB can suppress the production of melanin via the modulation of tyrosinase activity.

Proteases are involved in a broad range of physiological processes, including host invasion by fungal pathogens, and enzymatic inhibition is a key molecular mechanism controlling proteolytic activity. Importantly, inhibitors from natural or synthetic sources have demonstrated applications in biochemistry, biotechnology, and biomedicine. However, the need to discover new reservoirs of these inhibitory molecules with improved efficacy and target range has been underscored by recent protease characterization related to infection and antimicrobial resistance. In this regard, naturally-sourced inhibitors show promise for application in diverse biological systems due to high stability at physiological conditions and low cytotoxicity. Moreover, natural sources (e.g., plants, invertebrates, and microbes) provide a large reservoir of undiscovered and/or uncharacterized bioactive molecules involved in host defense against predators and pathogens. In this Review, we highlight discoveries of protease inhibitors from environmental sources, propose new opportunities for assessment of antifungal activity, and discuss novel applications to combat biomedically-relevant fungal diseases with in vivo and clinical purpose.

Harnessing The Role Of Rubiadin in Cancer: Current Scenario And Future Perspectives.

This work describes the synthesis and characterization of boronic acid-based supramolecular structures. Macrocycles, dendritic structures, polymers, rotaxanes, and cages were assembled using four types of reversible reactions. The key point of the strategy is the parallel utilization of two –or more– of these reactions. Initially, aryl and alkylboronic acids were condensed with dihydroxypyridine ligands to give tetrameric or pentameric macrocycles, in which four or five boronate esters are connected by dative B-N bonds. These macrocycles were then used as scaffolds for the assembly of more complex structures from the multicomponent reaction of formyl functionalized boronic acids, with dihydroxypyridine ligands and primary amines. Dendritic structures having a tetrameric or pentameric macrocyclic core and four, five, eight, or ten amine-derived groups in their periphery were obtained. Three-component reactions were further used to prepare boronate ester polymers from aryl boronic acids, 1,2,4,5-tetrahydroxybenzene and either 1,2-di(4-pyridyl)ethylene or 4,4'-dipyridine. Crystallographic analyses show that the bis(dioxaborole) units are connected by dipyridyl linkers via dative B-N interactions. A computational study provides evidence that the polymers are strongly colored due to efficient intrastrand charge transfer excitations from the tetraoxobenzene to the dipyridyl linker. This latter property was used to assemble the first boron-based rotaxanes from 1,2-di(4-pyridyl)ethylene, catechol, 3,5-bis(trifluoromethyl)phenylboronic acid and 1,5-dinaphto-38-crown-10 or bis-p-phenylene-34-crown-10. In the last part of this work, boronate ester condensations were combined with imine condensations to build organic macrocycles and cages. The former interaction was also used together with metal-ligand interactions to prepare rhenium-based macrocycles. Finally, a nanometer-sized macrocycle was obtained in one step from four chemically distinct building blocks via the simultaneous utilization of the three reversible reactions.

The present study was to understand how efficiently the astaxanthin in Calanus oil is utilized for flesh colouration in Atlantic salmon (Salmo salar). Postsmolts of the fish (309 g) were held at 7.9 °C and they were fed diets containing 20 or 60 mg astaxanthin per kilogram feed derived from a synthetic source or from Calanus oil for 181 days. Besides growth and feed intake assessments, at day 81 and 181, fish flesh were subjected to colour analysis and astaxanthin determination. Growth and feed performance did not vary between the groups. There were significant differences in the amount of astaxanthin in muscle between almost all groups both at day 81 (P < 0.05) and at day 181 (P < 0.001). However, a notable similarity between fish receiving 20 mg astaxanthin from the synthetic source and those receiving 60 mg astaxanthin from Calanus oil (P > 0.05) at day 181 indicated that comparable amounts were deposited only with the greater level of the natural source. Tristimuli colorimeter a* values support the analytical results at day 181. Although Calanus oil did serve as a natural dietary pigment source for farmed salmon, its inclusion level should provide more than 60 mg astaxanthin per kilogram feed to achieve colouration preferred by the market.

Poly(vinyl alcohol)–poly(acrylic acid) interpenetrating networks. Study on phase separation and molecular motions

Two dimensional deuterium NMR measurements are reported for three different onium salts (CH3)3SeNO3-d3, (CH3)3TeI-d3, and (CH3)3SI-d9. In these molecular solids with the general structure (CH3)3E+X-, three methyl groups are attached to the E atom. There is the possibility of reorientation of the methyls about their C3 axes and reorientation of the whole tri-methyl group about the C'3 axis. From an analysis of the 2D NMR exchange spectra the angle between the E-C bonds and the rotation axis for trimethyl reorientation were determined. Exchange rates and spin lattice relaxation times are given for several temperatures, to show how the mixing times for the experiments were selected. The data presented for (CH3)3TeI-d3, demonstrate that 2D techniques are sensitive to motions on a time scale an order of magnitude slower than that accessible using 1D line shape techniques.Key words: deuterium NMR, molecular motion, onium salts, two dimensional spectra.