Crystal Structure Models for the Aldaramide Units of Poly(pentaramides)

The X-ray crystal structures of seven structurally related diamides, N,N′-dihexyl- and N,N′-dimethylglutaramide, N,N′-dimethylxylaramide, N,N′-dimethyl-l-arabinaramide, N,N′-dimethylribaramide monohydrate, 2,3,4-tri-O-acetyl-N,N′-dimethylxylaramide, and 2,3,4-tri-O-acetyl-N,N′-dimethyl-l-arabinaramide, were determined. These diamides were chosen as solid-state conformational models for the diamido repeating units of the corresponding polyamides. Solid-state conformations of the two N,N-dialkyglutaramides, with no pendant groups, were compared to those of their stereochemically different trihydroxy derivatives N,N′-dimethylxylaramide, l-arabinaramide and ribaramide, and the two aforementioned tri-O-acetylpentaramides.     

Analysis of 5'-mononucleotides in infant formula and adult/pediatric nutritional formula by liquid chromatography: First Action 2011.20

A method for the routine determination of 5'-mononucleotides (uridine 5'-monophosphate, inosine 5'-monophosphate, adenosine 5'-monophosphate, guanosine 5'-monophosphate, and cytidine 5'-monophosphate) in infant formula and adult nutritionals is described. After sample dissolution and addition of internal standard, potential interferences were removed by anion-exchange SPE followed by HPLC-UV analysis. Single-laboratory validation performance parameters include recovery (92-101%) and repeatability (1.0-2.3% RSD). The method was approved for Official First Action status by an AOAC expert review panel.     

Pentaric Acids and Derivatives from Nitric Acid–Oxidized Pentoses

This report describes the preparation of the four stereoisomeric pentaric acids by nitric acid oxidation of d-xylose, d-arabinose, l-arabinose, and d-ribose, with xylaric, d-arabinaric, and l-arabinaric acids being made in a reactor under computer control. The pentaric acids were converted to their crystalline N,N′-dimethylpentaramides, derivatives that proved useful for isolation of the arabinaric acids from their respective oxidation mixtures. The N,N′-dimethylpentaramides were readily convertible to the corresponding pentaric acid disodium salts in aqueous sodium chloride. The 2,3,4-O-triacetyl-N,N′-dimethylpentaramides of xylaric, l-arabinaric, and ribaric acid were also prepared. Ribaric acid was isolated as crystalline 1,4(5,2)-ribarolactone and further characterized by x-ray crystallography.     

A comparison of the charring and carbonisation of oxygen-rich precursors with the thermal reduction of graphene oxide

Chars and carbonised chars were produced from two oxygen-rich precursors (Phormium tenax leaf fibres and sucrose crystals) and compared to thermally reduced graphene oxide (TRGO) samples using a range of analytical techniques. A hypothesis that carbonised chars are chemically and nanostructurally more similar to TRGOs than to other proposed structural analogues such as graphites and fullerenes was investigated. The greatest similarities in chemical structural features were observed between the well-carbonised chars and thermally reduced graphene oxide both of which had been prepared using heat treatment temperatures above ≈700 °C. However, thermal analysis and infra-red spectroscopy demonstrated how the char formation process differs from the early stages of the thermal reduction of graphene oxide. Major differences in morphology between TRGOs and various chars were also clearly observable using scanning electron microscopy. Prominent signals indicating the presence of aromatic C–H functional groups were observable in char samples and negligible in the thermally reduced graphene oxide samples when both were analysed by infra-red spectroscopy. The similarities and differences on a nanostructural scale between carbonised chars and thermally reduced graphene oxide are discussed with a focus on clarifying existing models for non-graphitisable carbons produced from oxygen-rich precursors.     

Analysis of nucleosides and nucleotides in infant formula by liquid chromatography–tandem mass spectrometry

A method for the simultaneous analysis of nucleosides and nucleotides in infant formula using reversed-phase liquid chromatography–tandem mass spectrometry is described. This approach is advantageous for compliance testing of infant formula over other LC-MS methods in which only nucleotides or nucleosides are measured. Following sample dissolution, protein was removed by centrifugal ultrafiltration. Chromatographic analyses were performed using a C₁₈ stationary phase and gradient elution of an ammonium acetate/bicarbonate buffer, mass spectrometric detection and quantitation by a stable isotope-labelled internal standard technique. A single laboratory validation was performed, with spike recoveries of 80.1–112.9 % and repeatability relative standard deviations of 1.9–7.2 %. Accuracy as bias was demonstrated against reference values for NIST1849a certified reference material. The method has been validated for the analysis of bovine milk-based, soy-based, caprine milk-based and hydrolysed milk protein-based infant formulae.

Synthesis of Poly(galactaramides) from Alkylene- and Substituted Alkylenediammonium Galactarates

Polyhydroxypolyamides (PHPAs) represent a class of synthetic polyamides derived from aldaric acid and diamine monomer units. This paper describes the synthesis of some poly(galactaramides), a class of polyhydroxypolyamides, that employs alkylene and substituted alkylenediammonium galactarate salts, with 1:1 molar equivalency of the diacid and diamine monomer components, as precursors for the polyamides. The salts were treated with acid/alcohol and then base in order to initiate the polymerization in methanol. The polyamides, labeled as prepolyamides, precipitated from solution and were then subjected to a second polymerization (postpolymerization) in a different solvent to produce a generally larger polyamide, labeled as a postpolyamide.     

The Structures and Hydrogen Bonding Networks in Crystals of Alkylenediammonium Salts of Galactaric Acid

The crystal structures of five alkylenediammonium galactarates (1– 5) were determined because the information from these structures may provide some insight into the solid state structures of the poly(alkylene galactaramides) derived from these salts. In each case the meso-galactarate anion is in the extended conformation. In four out of the five cases associations between galactarate units led to alternating layers of anions and cations rather than the expected alternation of anion and cation found in ionic solids. All five salts display extensive hydrogen bonding involving ammonium and carboxylate groups and in some cases hydroxyl groups of the anion.