Marked increase in PROP taste responsiveness following oral supplementation with selected salivary proteins or their related free amino acids

The genetic predisposition to taste 6-n-propylthiouracil (PROP) varies among individuals and is associated with salivary levels of Ps-1 and II-2 peptides, belonging to the basic proline-rich protein family (bPRP). We evaluated the role of these proteins and free amino acids that selectively interact with the PROP molecule, in modulating bitter taste responsiveness. Subjects were classified by their PROP taster status based on ratings of perceived taste intensity for PROP and NaCl solutions. Quantitative and qualitative determinations of Ps-1 and II-2 proteins in unstimulated saliva were performed by HPLC-ESI-MS analysis. Subjects rated PROP bitterness after supplementation with Ps-1 and II-2, and two amino acids (L-Arg and L-Lys) whose interaction with PROP was demonstrated by (1)H-NMR spectroscopy. ANOVA showed that salivary levels of II-2 and Ps-1 proteins were higher in unstimulated saliva of PROP super-tasters and medium tasters than in non-tasters. Supplementation of Ps-1 protein in individuals lacking it in saliva enhanced their PROP bitter taste responsiveness, and this effect was specific to the non-taster group.(1)H-NMR results showed that the interaction between PROP and L-Arg is stronger than that involving L-Lys, and taste experiments confirmed that oral supplementation with these two amino acids increased PROP bitterness intensity, more for L-Arg than for L-Lys. These data suggest that Ps-1 protein facilitates PROP bitter taste perception and identifies a role for free L-Arg and L-Lys in PROP tasting

Dose-Dependent Effects of L-Arginine on PROP Bitterness Intensity and Latency and Characteristics of the Chemical Interaction between PROP and L-Arginine

Genetic variation in the ability to taste the bitterness of 6-n-propylthiouracil (PROP) is a complex trait that has been used to predict food preferences and eating habits. PROP tasting is primarily controlled by polymorphisms in the TAS2R38 gene. However, a variety of factors are known to modify the phenotype. Principle among them is the salivary protein Ps-1 belonging to the basic proline-rich protein family (bPRP). Recently, we showed that oral supplementation with Ps-1 as well as its related free amino acids (L-Arg and L-Lys) enhances PROP bitterness perception, especially for PROP non-tasters who have low salivary levels of Ps-1. Here, we show that salivary L-Arg levels are higher in PROP super-tasters compared to medium tasters and non-tasters, and that oral supplementation with free L-Arg enhances PROP bitterness intensity as well as reduces bitterness latency in a dose-dependent manner, particularly in individuals with low salivary levels of both free L-Arg and Ps-1 protein. Supplementation with L-Arg also enhanced the bitterness of caffeine. We also used 1H-NMR spectroscopy and quantum-mechanical calculations carried out by Density Functional Theory (DFT) to characterize the chemical interaction between free L-Arg and the PROP molecule. Results showed that the -NH2 terminal group of the L-ArgH+ side chain interacts with the carbonyl or thiocarbonyl groups of PROP by forming two hydrogen bonds with the resulting charged adduct. The formation of this PROP\u2022ArgH+ hydrogen-bonded adduct could enhance bitterness intensity by increasing the solubility of PROP in saliva and its availability to receptor sites. Our data suggest that L-Arg could act as a 'carrier' of various bitter molecules in saliva

A kinetic study of mercury(II) transport through a membrane assisted by new transport reagent

Background: A new organodithiophosphorus derivative, namely O-(1,3-Bispiperidino-2-propyl)-4-methoxy phenyldithiophosphonate, was synthesized and then the kinetic behavior of the transport process as a function of concentration, temperature, stirring rate and solvents was investigated.Results: The compound 1 was characterized by elemental analysis, IR, H-1 and P-31 NMR spectroscopies. The transport of mercury(II) ion by a zwitterionic dithiophosphonate 1 in the liquid membrane was studied and the kinetic behavior of the transport process as a function of concentration, temperature, stirring rate and solvents was investigated. The compound 1 is expected to serve as a model liquid membrane transport with mercury(II) ions.Conclusion: A kinetic study of mercury(II) transport through a membrane assisted by O-(1,3-Bispiperidino-2-propyl)4-methoxy phenyldithiophosphonate was performed. It can be concluded that the compound 1 can be provided a general and straightforward route to remove toxic metals ions such as mercury(II) ion from water or other solution

Polyiodides and polytellurides: Analogies and differencies

Analogies and differences between polytellurides and polyiodides are discussed with the help of quantum chemical DFT calculation

4-Methoxyphenylphosphonic acid: reactivity of Lawesson's reagent

Reactivity of Lawesson's reagent was investigated by synthesizing 4-methoxyphenylphosphonic acid, obtained as a by-product from the reaction of the reagent with methyl iodide. The structures of the compounds were rationalized in terms of their significant intermolecular interactions. Hydrogen bonds of type P-O-H·O = P linked molecules into helical chains and formed ten-membered hydrogen-bonded rings

A spectroscopic study on ionization of 2-, 3- and 4-aminopyridines

The first ionization constants of the 2-, 3-, and 4-aminopyridines were evaluated by spectrophotometric methods using Evolving Factor Analysis approach. The ionization constants of aniline and pyridine were estimated by potentiometric methods in the same experimental conditions for comparison. A C-13 NMR spectroscopy study is here presented to assess the protonation site in aminopyridines and to evaluate the resonance effects

Gold oxidative dissolution by (thioamide)-I2 adducts

Elemental gold powder is easily oxidised under mild reaction conditions with 1 : 1 I2-adducts of the thioamides 3-methyl-benzothiazole-2- thione (mbtt) and 1-methyl-1H-benzimidazole-2(3H)-thione (mbit) with separation of the ionic complexes [AuI(mbtt)2]I3 (1) and [(mtbiH)2](AuI4)I3 (2) [mtbiH = the imido protonated form of 2-(methylthio)benzimidazole] (gold oxidation yield >78% and 45%, respectively). The X-ray crystal structure of 1 shows the Au(i) centre linearly bound by two neutral ligands via the sulphur atom, whereas the X-ray crystal structure of 2 shows the Au(iii) centre surrounded by four iodides in a square-planar arrangement. The oxidising/complexing properties of the mbtt·I2 and mbit·I2 adducts were interpreted considering the S-donor to I2 interaction that leads to a charge separation between the Ib and It iodine atoms in the fragment S-Ib-It. The oxidation of gold in a non-aqueous solvent by thioamide-I2 adducts could be a promising alternative process to the numerous hydrometallurgical ones for the recovery of gold from secondary sources. © 2013 The Royal Society of Chemistry