The Oligomerization of Glucose Under Plausible Prebiotic Conditions.

The prebiotic origin of polysaccharides, the largest class of biopolymers by mass in extant biology, has seldom been investigated experimentally. Herein, we report on the acid-catalyzed condensation of aqueous solutions of glucose, a model monosaccharide, under plausible prebiotic conditions employing a wet-dry (night-day) protocol with 0.01 M HCl at 50 °C. This protocol leads to the formation of oligosaccharides containing up to eight monomeric units identified by high resolution mass spectrometry. The regio- and stereochemistry of the oligomeric acetal linkages, as well as the quantitative analysis of glucose conversion, are elucidated by combining 1H, 13C and 2D NMR spectroscopy. Ten out of eleven possible acetal linkages, including α- and ß- anomers, have been identified with the α- and ß- 1,6-acetals being the dominant linkages observed. In addition, the acid-catalyzed oligomerization of several glucose disaccharides such as cellobiose, maltose, and gentiobiose are presented along with an accompanying comparison with the corresponding oligomerization of glucose.

Production of tartrates by cyanide-mediated dimerization of glyoxylate: a potential abiotic pathway to the citric acid cycle.

An abiotic formation of meso- and DL-tartrates in 80% yield via the cyanide-catalyzed dimerization of glyoxylate under alkaline conditions is demonstrated. A detailed mechanism for this conversion is proposed, supported by NMR evidence and (13)C-labeled reactions. Simple dehydration of tartrates to oxaloacetate and an ensuing decarboxylation to form pyruvate are known processes that provide a ready feedstock for entry into the citric acid cycle. While glyoxylate and high hydroxide concentration are atypical in the prebiotic literature, there is evidence for natural, abiotic availability of each. It is proposed that this availability, coupled with the remarkable efficiency of tartrate production from glyoxylate, merits consideration of an alternative prebiotic pathway for providing constituents of the citric acid cycle.

Biomarkers of whale shark health: a metabolomic approach.

In a search for biomarkers of health in whale sharks and as exploration of metabolomics as a modern tool for understanding animal physiology, the metabolite composition of serum in six whale sharks (Rhincodon typus) from an aquarium collection was explored using (1)H nuclear magnetic resonance (NMR) spectroscopy and direct analysis in real time (DART) mass spectrometry (MS). Principal components analysis (PCA) of spectral data showed that individual animals could be resolved based on the metabolite composition of their serum and that two unhealthy individuals could be discriminated from the remaining healthy animals. The major difference between healthy and unhealthy individuals was the concentration of homarine, here reported for the first time in an elasmobranch, which was present at substantially lower concentrations in unhealthy whale sharks, suggesting that this metabolite may be a useful biomarker of health status in this species. The function(s) of homarine in sharks remain uncertain but it likely plays a significant role as an osmolyte. The presence of trimethylamine oxide (TMAO), another well-known protective osmolyte of elasmobranchs, at 0.1-0.3 mol L(-1) was also confirmed using both NMR and MS. Twenty-three additional potential biomarkers were identified based on significant differences in the frequency of their occurrence between samples from healthy and unhealthy animals, as detected by DART MS. Overall, NMR and MS provided complementary data that showed that metabolomics is a useful approach for biomarker prospecting in poorly studied species like elasmobranchs.

Self-organization of water in lithium/nitrobenzene system.

The effect of lithium ion on the ordering of water in water-saturated nitrobenzene has been probed by 2H NMR, diffusion ordered spectroscopy and neutron scattering. It was shown that increased water concentration in LiClO4/wet nitrobenzene results in the formation of a metastable solvatomer with mixed water and nitrobenzene character, Li+(W/NB). This species is shown to decay over hours to two solvatomers, one dominated by nitrobenzene Li+(NB) and the other dominated by water Li+(W). To confirm the assignment of these solvation states, diffusion ordered deuterium NMR spectroscopy has been used to elucidate the hydrodynamic radii of these solvatomers. Neutron scattering yields vibrational spectroscopy information that shows how addition of lithium to the nitrobenzene/water system results in relatively slow self-organization of the water environment (hours).

1H NMR investigation of thermally triggered insulin release from poly(N-isopropylacrylamide) microgels.

We describe investigations of insulin release from thermoresponsive microgels using variable temperature (1)H NMR. Microgel particles composed of poly(N-isopropylacrylamide) were loaded with the peptide via a swelling technique, and this method was compared to simple equilibrium partitioning. Variable temperature (1)H NMR studies suggest that the swelling loading method results in enhanced entrapment of the peptide versus equilibrium partitioning. A centrifugation-loading assay supports this finding. Pseudo-temperature jump (1)H NMR measurements suggest that the insulin release rate is partially decoupled from microgel collapse. These types of direct release investigations could prove to be useful methods in the future design of controlled macromolecule drug delivery devices.

Iso-coenzyme A.

Iso-coenzyme A is an isomer of coenzyme A in which the monophosphate is attached to the 2'-carbon of the ribose ring. Although iso-CoA was first reported in 1959 (Moffatt, J. G., and Khorana, H. G. (1959) J. Am. Chem. Soc. 81, 1265-1265) to be a by-product of the chemical synthesis of CoA, relatively little attention has been focused on iso-CoA or on acyl-iso-CoA compounds in the literature. We now report structural characterizations of iso-CoA, acetyl-iso-CoA, acetoacetyl-iso-CoA, and beta-hydroxybutyryl-iso-CoA using mass spectrometry (MS), tandem MS, and homonuclear and heteronuclear NMR analyses. Although the 2'-phosphate isomer of malonyl-CoA was recently identified in commercial samples, previous characterizations of iso-CoA itself have been based on chromatographic analyses, which ultimately rest on comparisons with the degradation products of CoA and NADPH or have been based on assumptions regarding enzyme specificity. We describe a high performance liquid chromatography methodology for separating the isomers of several CoA-containing compounds. We also report here the first examples of iso-CoA-containing compounds acting as substrates in enzymatic acyl transfer reactions. Finally, we describe a simple synthesis of iso-CoA from CoA, which utilizes beta-cyclodextrin to produce iso-CoA with high regioselectivity, and we demonstrate a plausible mechanism that accounts for the existence of iso-CoA isomers in commercial preparations of CoA-containing compounds. We anticipate that these results will provide methodology and impetus for investigating iso-CoA compounds as potential pseudo-substrates or inhibitors of the >350 known CoA-utilizing enzymes.

NMR study of lithium ion in nitrobenzene/water system.

The goal of this project has been to elucidate the solvation states and kinetics involved in the transfer of Li ions between nitrobenzene and water. A large interface area has been realized by confining one phase in polymer beads and suspending them in the other phase. A 2D 7Li-NMR spectroscopic result of such a system obtained on a 400 MHz instrument has shown that the rate of the Li ion transfer exchange between nitrobenzene and water is too fast to resolve individual solvatomers. A pair of well-resolved 7Li-NMR peaks corresponding to different solvation environments of Li+ in "wet" nitrobenzene has been observed. The most surprising result is that the ratio of those two peaks and their separation changes over a period of days, but it can be reversibly changed by mechanical disturbance, such as ultrasonication. This effect is reproducible and suggests spontaneous but slow formation of metastable solvatomers of Li+. Another surprising observation has been slow and irreversible incorporation of lithium ion from wet nitrobenzene into the walls of the silica-containing vessels.

Regioselective syntheses of 2,3,4-tribromopyrrole and 2,3,5-tribromopyrrole.

2,3,4-Tribromopyrrole (1) and 2,3,5-tribromopyrrole (2) were each synthesized from pyrrole. Spectral data and antifeedant effects for synthetic 1 and the antipredatory chemical defense compound of the marine hemichordate Saccoglossus kowalevskii were in agreement, confirming the structure of the deterrent natural product as 1. Spectral data for 2 differed from synthetic and natural 1.