No abstract

Monosaccharide analysis is a critical way to profile the composition of complex carbohydrates. Methods to analyze neutral and amino sugars have been established for a long time, but methods for acidic sugars are rare. The acidic sugars, including uronic acids and sialic acids, are also important components in some complex carbohydrates. In this report, a highperformance anion-exchange chromatography method with pulsed amperometric detection was initially developed to analyze acidic sugars including different uronic acids and sialic acids. Subsequently, a method to profile complete monosaccharides, including most neutral, amino, and acidic sugars, was developed. This method has a limit of quantitation of ∼12.5 × 10 −3 nmol for each sugar as well as good linearity over a wide range. This is a convenient procedure because it avoids additional derivatization of monosaccharides and has a broad application to a wide range of complex carbohydrates. The monosaccharide compositions of a variety of complex carbohydrates such as different glycosaminoglycans, alginate, fucoidan, and glycans were profiled by this comprehensive method. In addition, the hydrolysis patterns of these complex carbohydrates are discussed.

The contamination of the widely used lifesaving anticoagulant drug heparin in 2007 has drawn renewed attention to the challenges that are associated with the characterization, quality control and standardization of complex biological medicines from natural sources. Heparin is a linear, highly sulfated polysaccharide consisting of alternating glucosamine and uronic acid monosaccharide residues. Heparin has been used successfully as an injectable antithrombotic medicine since the 1930s, and its isolation from animal sources (primarily porcine intestine) as well as its manufacturing processes have not changed substantially since its introduction. The 2007 heparin contamination crisis resulted in several deaths in the United States and hundreds of adverse reactions worldwide, revealing the vulnerability of a complex global supply chain to sophisticated adulteration. This Perspective discusses how the US Food and Drug Administration (FDA), the United States Pharmacopeial Convention (USP) and international stakeholders collaborated to redefine quality expectations for heparin, thus making an important natural product better controlled and less susceptible to economically motivated adulteration.

Rats exposed for 3 weeks to uniform 60-Hz electric fields of 39 kV/m (effective field strength) failed to show normal pineal gland circadian rhythms in serotonin N-acetyl transferase activity and melatonin concentrations. The time required for recovery of the melatonin rhythm after cessation of field exposure was determined to be less than 3 days. The rapid recovery suggests that the overall metabolic competence of the pineal is not permanently compromised by electric-field exposure, and that the circadian rhythm effect may be neuronally mediated.

emphasized that our estimation of isocyanide isomerization energies does not require knowledge of any heats of formation.The core binding energies of tert-butyl isocyanide, tert-butyl cyanide,33 phenyl isocyanide, and benzonitrile33 can be used to predict values for the corresponding isocyanide-to-cyanide isomerization enthalpies. The isomerization enthalpy is calculated to be -27 kcal mol"1 for Zcrf-butyl isocyanide and -28 kcal mol"1 for phenyl isocyanide. Given the uncertainty in the core replacement energies (~5 kcal mol"1), our results indicate that A£lso (33) To be consistent with our assignment of the CH3CN spectrum, we assume that the carbon Is binding energy of the CN carbon atom of a nitrile is always lower than that of the carbon atom directly bonded to the CN group. Thus we take 291.8 and 291.85 eV for the CN carbon atoms of (CH3)3CN23 and C6H5CN,34 respectively.for the isocyanide RNC is essentially independent of the R group.