Carbohydrate Mixtures Research Articles

Effect of molecular structure on the conductivity of amorphous carbohydrate–water–KCl mixtures in the supercooled liquid state

The effect of carbohydrate structure on the conductivity of low water content amorphous carbohydrate–water, and carbohydrate–water–KCl mixtures, has been measured using both direct current and alternating current techniques at temperatures in the supercooled liquid and glassy range, ranging from −40 to 80 °C. The structures included homologous mono-, di- and trisaccharides (glucose, maltose and maltotriose), a monosaccharide with no exocyclic hydroxymethyl group (xylose) and a second trisaccharide (raffinose). The KCl-mixtures contained 9.3% w/w water and 0.74% w/w KCl which resulted in calorimetric glass transition temperatures, T g, in the range −29–19 °C. At this concentration conduction due to KCl dominated that due to intrinsic conductors originating from the carbohydrates and water. In the supercooled liquid region, as temperature, T, is reduced to T g, the activation energy of the molar conductivity of KCl, Λ m, increased as described by a Vogel–Tamman–Fulcher-type equation, Λ m= Λ m0exp[ B/( T− T 0)], where Λ m0, B and T 0 are constants. Comparison of the molar conductivity of KCl in the carbohydrate mixtures at T g with that in aqueous solutions showed that conductivity is, to varying extents, uncoupled from viscosity. The uncoupling increased in the order d-xylose< d-glucose<maltose<maltotriose and raffinose. The results suggest that the primary structural characteristic determining conductivity is molecular weight, though the presence of the exocyclic hydroxymethyl group in the monosaccharide also has an effect. Whilst at T g the d-xylose mixture had the lowest conductivity, at a particular temperature the trisaccharide mixtures of maltotriose and raffinose had the lowest conductivities.

Capillary Affinity Electrophoresis for the Screening of Post-Translational Modification of Proteins with Carbohydrates

Glycosylation is one of the most important post-translational events for proteins, affecting their functions in health and disease, and plays significant roles in various information traffics for intracellular and intercellular biological events (Hancock, W. S. J. Proteome Res. 2002, 1, 297). We have attempted to obtain the information on the numbers and amounts of carbohydrate chains. Interaction between carbohydrate chains and proteins that recognize them is a target to understand the biological roles of glycosylation. To date, there have been a few strategies for simultaneous analysis of the interactions between complex mixtures of carbohydrates and proteins. Here, we report an approach to categorize carbohydrate chains using a few glycoprotein samples as models for the studies on the analysis of post-translational modification of proteins with carbohydrates. A combination of some specific lectins was used as carbohydrate-binding proteins. The method is based on high-resolution separation of fluorescent-labeled carbohydrates by capillary electrophoresis with laser-induced fluorescent detection in the presence of carbohydrate-binding proteins at different concentrations. The present technique affords (1) simultaneous determination of carbohydrate chains, (2) binding specificity of the constituent carbohydrate chains to specific proteins, and (3) kinetic data such as the association constant of each carbohydrate. We found that the lectins employed in the present study could discriminate subtle difference in linkages and resolved the carbohydrate mixtures. The results will be useful, for example, to understand the biological events expressed with carbohydrate changes on the cell surface.

Factors affecting conjugated linoleic acid and trans-C18:1 fatty acid production by mixed ruminal bacteria.

The objective of this study was to identify environmental factors that influence conjugated linoleic acid (CLA) and trans-C18:1 fatty acid production by mixed ruminal bacteria. Ruminal contents were collected from a 600-kg ruminally fistulated Hereford steer maintained on pasture. Mixed ruminal bacteria were obtained by differential centrifugation under anaerobic conditions and added to a basal medium that contained a commercial emulsified preparation of soybean oil and a mixture of soluble carbohydrates (cellobiose, glucose, maltose, and xylose). Culture samples were collected from batch culture incubations at 0, 2, 4, 6, 8, 12, 24, 26, 28, 30, 32, and 48 h. Continuous culture incubations were conducted at dilution rates of 0.05 and 0.10 h(-1) with extracellular pH values of 5.5 and 6.5, and 0.5 and 1.0 g/L of mixed soluble carbohydrates. Culture samples were obtained from the culture vessel once steady-state conditions had been achieved. In batch culture, trans-C18:1 concentrations increased over time and reached a maximum at 48 h. Little CLA was produced during the first 8 h, but cis-9, trans-11 CLA concentrations remained high between 24 and 30 h. When mixed ruminal bacteria were maintained in continuous culture on 0.5 g/L of mixed soluble carbohydrates, concentrations of trans-C18:1 and cis-9, trans-11 CLA were reduced (P < 0.05) at a dilution rate of 0.05 h(-1) and an extracellular pH of 5.5. Similar effects were also observed when 1.0 g/L of mixed soluble carbohydrates was used. When extracellular pH was lowered to 5.0, neither trans-C18:1 or CLA isomers were detected. In conclusion, our results suggest that culture pH appears to have the most influence on the production of trans-C18:1 and CLA isomers by mixed ruminal bacteria.

Leucine is a direct-acting nutrient signal that regulates protein synthesis in adipose tissue.

In freshly isolated rat adipocytes, leucine or its analog norleucine activates the mammalian target of rapamycin (mTOR)-signaling pathway. This results in phosphorylation of the ribosomal protein S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E-binding protein-1 (4E-BP1), two proteins involved in the initiation phase of protein synthesis. The purpose of the studies reported herein was to address the question of whether or not these in vitro effects of leucine and norleucine on adipocytes could be extended to the intact animal and to other tissues. To accomplish this, food-deprived (18 h) male Sprague-Dawley rats were orally administered solutions (2.5 ml/100 g body wt) containing normal saline (0.9% NaCl), a carbohydrate mixture (26.2% D-glucose and 26.2% sucrose), leucine (5.4%), or norleucine (5.4%). The protein synthetic responses of adipose tissue were measured and compared with those of other tissues. In addition, S6K1 and 4E-BP1 phosphorylation was measured, as was the plasma concentration of insulin and tissue ATP concentrations. Leucine administration stimulated protein synthesis in adipose tissue, gastrocnemius, and kidney but not in liver and heart. Norleucine stimulated protein synthesis in all of the tissues tested but, in contrast to leucine, without affecting plasma insulin concentrations. The carbohydrate meal had no effect on protein synthesis in any tissue tested but elicited a robust increase in plasma insulin. These findings provide support for a role of leucine as a direct-acting nutrient signal for stimulation of protein synthesis in adipose tissue as well as other select tissues. In adipose tissue, the effects of the different treatment conditions on the acute regulation of protein synthesis closely correlated with changes in phosphorylation of S6K1 and 4E-BP1; however, this correlation did not exist in all tissues examined. This result implies that leucine or norleucine may acutely stimulate protein synthesis, at least in some tissues, by a mechanism that is independent of both S6K1 and 4E-BP1 phosphorylation.

Physical characteristics of total parenteral nutrition bags significantly affect the stability of vitamins C and B1: a controlled prospective study.

Vitamin degradation occurring during the storage of total parenteral nutrition (TPN) mixtures is significant and affects clinical outcome. This study aimed to assess the influence of the TPN bag material, the temperature, and the duration of storage on the stability of different vitamins. Solutions of multivitamin and trace elements at recommended doses were injected into either an ethylvinyl acetate (EVA) bag or a multilayered (ML) bag filled with 2500 mL of an identical mixture of carbohydrates (1200 kcal), fat (950 kcal), and amino acids (380 kcal). The bags were then stored at 4 degrees C, 21 degrees C, or 40 degrees C. Concentrations of vitamins A, B1, C, and E were measured up to 72 hours after compounding, using high-pressure liquid chromatography. Ten percent to 30% of vitamin C degradation occurred within the first minutes after TPN compounding. Vitamin C was more stable in ML bags (half-life: 68.6 hours at 4 degrees C, 24.4 hours at 21 degrees C, and 6.8 hours at 40 degrees C) than in EVA bags (half-life: 7.2 hours at 4 degrees C, 3.2 hours at 21 degrees C, and 1.1 hour at 40 degrees C). Moreover, appearance of dehydroascorbic acid in the TPN mixture did not compensate for vitamin C losses. Vitamin B1 was stable at 21 degrees C, but a 43% loss occurred at 40 degrees C after 72-hour storage in EVA bags. The other vitamins were stable in the TPN mixture stored in both bags at any temperature and without daylight protection. Degradations of vitamins C and B, are significantly reduced in ML bags compared with EVA bags. To prevent vitamin C deficiencies, its initial dose should be adapted to its degradation rate, which depends on the TPN bag material, the ambient temperature, and the length of time between TPN compounding and the end of infusion to the patient.

Plant root carbohydrates affect growth behaviour of endophytic microfungi

Peucedanum alsaticum and Peucedanum cervaria represent characteristic umbellifers (Apiaceae) of calcareous grasslands in Central and Eastern Europe. Both accumulate glucose, fructose, mannitol and sucrose as dominant carbohydrates in their roots. The objective of the study was to determine if endophytes utilise host plant carbohydrates differently than rhizosphere and bulk soil microfungi. Inula ensifolia (Asteraceae), Lathyrus latifolius (Fabaceae) and Bromus erectus (Poaceae), all plants that grow along with the two umbellifers, accumulated only sucrose as major sugar in their roots. Germ tube growth of 30 microfungal isolates, recovered from various rhizosphere habitats, was quantified in microdilutions (10–5000 μg ml −1) of a number of substrates, including glucose, sucrose, mannitol and the water-soluble plant root carbohydrate mixtures. Multivariate analysis of variance and subsequent least significant difference analysis of isolate group means revealed that sucrose and mannitol utilisation affected affiliation to a certain fungal lifestyle. Endophytes utilised host plant carbohydrates more efficiently at lower concentrations. Conversely, higher concentrations slowed their growth. Non-host carbohydrates did not cause comparable effects. The results suggest that root carbohydrate diversity may determine fungal diversity in natural rhizosphere environments.

Plant root carbohydrates affect growth behaviour of endophytic microfungi

Abstract Peucedanum alsaticum and Peucedanum cervaria represent characteristic umbellifers (Apiaceae) of calcareous grasslands in Central and Eastern Europe. Both accumulate glucose, fructose, mannitol and sucrose as dominant carbohydrates in their roots. The objective of the study was to determine if endophytes utilise host plant carbohydrates differently than rhizosphere and bulk soil microfungi. Inula ensifolia (Asteraceae), Lathyrus latifolius (Fabaceae) and Bromus erectus (Poaceae), all plants that grow along with the two umbellifers, accumulated only sucrose as major sugar in their roots. Germ tube growth of 30 microfungal isolates, recovered from various rhizosphere habitats, was quantified in microdilutions (10-5000 mug ml(-1)) of a number of substrates, including glucose, sucrose, mannitol and the water-soluble plant root carbohydrate mixtures. Multivariate analysis of variance and subsequent least significant difference analysis of isolate group means revealed that sucrose and mannitol utilisation affected affiliation to a certain fungal lifestyle. Endophytes utilised host plant carbohydrates more efficiently at lower concentrations. Conversely, higher concentrations slowed their growth. Non-host carbohydrates did not cause comparable effects. The results suggest that root carbohydrate diversity may determine fungal diversity in natural rhizosphere environments.

Fermentation by Lactobacillus fermentum Ogi E1 of different combinations of carbohydrates occurring naturally in cereals: consequences on growth energetics and α-amylase production

Glucose, fructose, sucrose and starch are naturally present in cereals. Fermentation of different combinations of these carbohydrates by Lactobacillus fermentum Ogi E1, a sourdough heterofermentative lactobacillus, was investigated to determine effects on fermentation kinetics, growth energetics and α-amylase production. Irrespective of the substrate combination, the strain was able to simultaneously produce α-amylase and consume starch, glucose, fructose and sucrose. In mixtures of starch with either sucrose or fructose or with both fructose and glucose, yields of α-amylase from biomass ( Y amy/x) were similar to those observed for starch. However, for starch and glucose or starch, glucose, fructose and sucrose mixtures, both Y amy/x and the specific rate of α-amylase production decreased markedly. In fructose- or sucrose-containing mixtures, mannitol was formed stoichiometrically indicating that fructose served as electron acceptor, and acetate was produced at constant yield from biomass ( Y ac/x) (1 g acetate g biomass −1). Acetate production was expected to confer to the strain a competitive advantage during natural fermentation by improving biomass formation and growth through an increase in the ATP gain. Y ATP varied depending on the carbohydrate mixture, indicating different effects of substrate mixtures on the efficiency in ATP coupling to biomass formation. Compared to starch fermentation, the highest value of Y ATP (29 g biomass mol ATP −1) was estimated for the starch/fructose mixture but no increase in μ max was observed. The lowest value (16 g biomass mol ATP −1) was obtained for the starch, glucose and fructose mixture, whereas for the mixture of all carbohydrates, Y ATP was similar to that obtained with starch alone (20 g biomass mol ATP −1) and it was intermediary for the starch and sucrose mixture (17 g biomass mol ATP −1). It is concluded that competitiveness of the strain cannot be based on expected energy gain in mixed substrate fermentation involving fructose and sucrose with glucose and starch, but rather on its ability to simultaneously use carbohydrates while producing α-amylase and to produce acetic acid. Acetic acid production could enhance the strain capacity to inhibit nonacid-tolerant, competitive microflora at the earlier stage of natural fermentation.

Glycoscreening by on-line sheathless capillary electrophoresis/electrospray ionization-quadrupole time of flight-tandem mass spectrometry.

An analytical approach based on sheathless on-line coupling of capillary electrophoresis (CE) and electrospray ionization (ESI) quadrupole time-of-flight (QTOF) mass spectrometry (MS) has been developed for providing new insight into the characterization of carbohydrate mixtures. The home-built sheathless CE/

Physicochemical stability assessments of lipid emulsions of varying oil composition

Background and aims: Intravenous lipid emulsions have been shown to be unstable when the percent fat >5 μm (PFAT >5 μm) exceeds 0.4% by weight of the total fat present. We investigated the physicochemical stability of a standard low amino acid and carbohydrate mixture containing electrolytes when combined with four different commercial intravenous lipid emulsions of varying oil composition. Methods: The 20% (w/v) lipid emulsions studied were composed of the following oils (by weight): 1) 1 : 1 soybean/safflower (SS); 2) 100% soybean (S); 3) 1 : 1 soybean/MCT (SM) and 4) 4 : 1 olive/soybean (OS). Physicochemical stability was assessed by light obscuration or extinction using a single-particle optical sensing technique to detect growth of fat globules in the large diameter tail (>1 μm) of the droplet size distribution and by visual analyses for evidence of phase separation. Results: The physicochemical stability of SS and S-based all-in-one mixtures significantly deteriorated over time when compared to the mixtures made from SM and OS. In addition, of the four mixtures studied that contained SS (n=2) and S (n=2), only one of each bag studied showed visually obvious destabilization by the presence of free oil from phase separation, despite highly abnormal changes in the globule size distribution of all four preparations. Conclusion: The results suggest that all-in-one mixtures composed of either soybean oil alone or in combination with safflower oil are less stable than those mixed with either MCT or olive oil which also contain sodium oleate that can act as co-emulsifying agent.

Effects of Preservation Methods On Geosmin Content and Off-Flavor in Nile Tilapia (Oreochromis niloticus)

In this study, the masking or reduction of off-flavor in tilapia due to various preservation methods such as salting, drying, frying, smoking, microwave heating, marinating and fermentation with carbohydrate mixture (som fak preparation) was investigated by subjecting the processed tilapia to sensory evaluation and analyzing the concentrations of geosmin (1,10-trans -dimethyl-trans -9-decaol) in the processed samples. Dry salting or brining muddy-flavored fish and then drying either by hot air at 50°C or sun-drying resulted to only a slight reduction in the geosmin content of the product. Deep-frying reduced the muddy flavor intensity and geosmin content in salted-dried tilapia. Pretreatment of tilapia fillets with acidified brine before smoking reduced geosmin content and masked the muddy flavor in the smoked product. Microwave cooking of fresh muddy-flavored tilapia showed no effect on its geosmin content nor its off-flavor. Marinating tilapia in acetic acid solution resulted in decreased muddy flavor, and longer marinating period led to lower geosmin content in the product. The geosmin content of som fak made from muddy-flavor and non-muddy-flavor tilapia differed significantly, although sensory evaluation yielded no significant differences between the two types of som fak, and the taste panelists preferred the product fermented for 3 days.

Ingestion of Protein Hydrolysate and Amino Acid–Carbohydrate Mixtures Increases Postexercise Plasma Insulin Responses in Men

To optimize the postexercise insulin response and to increase plasma amino acid availability, we studied postexercise insulin levels after the ingestion of carbohydrate and wheat protein hydrolysate with and without free leucine and phenylalanine. After an overnight fast, eight male cyclists visited our laboratory on five occasions, during which a control drink and two different beverage compositions in two different doses were tested. After they performed a glycogen-depletion protocol, subjects received a beverage (3.5 mL. kg(-1)) every 30 min to ensure an intake of 1.2 g. kg(-1). h(-1) carbohydrate and 0, 0.2 or 0.4 g. kg(-1). h(-1) protein hydrolysate (and amino acid) mixture. After the insulin response was expressed as the area under the curve, only the ingestion of the beverages containing wheat protein hydrolysate, leucine and phenylalanine resulted in a marked increase in insulin response (+52 and + 107% for the 0.2 and 0.4 g. kg(-1). h(-1) mixtures, respectively; P: < 0. 05) compared with the carbohydrate-only trial). A dose-related effect existed because doubling the dose (0.2-0.4 g. kg(-1). h(-1)) led to an additional rise in insulin response (P: < 0.05). Plasma leucine, phenylalanine and tyrosine concentrations showed strong correlations with the insulin response (P: < 0.0001). This study provides a practical tool to markedly elevate insulin levels and plasma amino acid availability through dietary manipulation, which may be of great value in clinical nutrition, (recovery) sports drinks and metabolic research.

Correlation of activities of the enzymes alpha-phosphoglucomutase, UDP-galactose 4-epimerase, and UDP-glucose pyrophosphorylase with exopolysaccharide biosynthesis by Streptococcus thermophilus LY03.

The effects of different carbohydrates or mixtures of carbohydrates as substrates on bacterial growth and exopolysaccharide (EPS) production were studied for the yoghurt starter culture Streptococcus thermophilus LY03. This strain produces two heteropolysaccharides with the same monomeric composition (galactose and glucose in the ratio 4:1) but with different molecular masses. Lactose and glucose were fermented by S. thermophilus LY03 only when they were used as sole energy and carbohydrate sources. Fructose was also fermented when it was applied in combination with lactose or glucose. Both the amount of EPS produced and the carbohydrate source consumption rates were clearly influenced by the type of energy and carbohydrate source used, while the EPS monomeric composition remained constant (galactose-glucose, 4:1) under all circumstances. A combination of lactose and glucose resulted in the largest amounts of EPS. Measurements of the activities of enzymes involved in EPS biosynthesis, and of those involved in sugar nucleotide biosynthesis and the Embden-Meyerhof-Parnas pathway, demonstrated that the levels of activity of alpha-phosphoglucomutase, UDP-galactose 4-epimerase, and UDP-glucose pyrophosphorylase are highly correlated with the amount of EPS produced. Furthermore, a weaker relationship or no relationship between the amounts of EPS and the enzymes involved in either the rhamnose nucleotide synthetic branch of the EPS biosynthesis or the pathway leading to glycolysis was observed for S. thermophilus LY03.

Plasma insulin responses after ingestion of different amino acid or protein mixtures with carbohydrate

Protein induces an increase in insulin concentrations when ingested in combination with carbohydrate. Increases in plasma insulin concentrations have been observed after the infusion of free amino acids. However, the insulinotropic properties of different amino acids or protein (hydrolysates) when co-ingested with carbohydrate have not been investigated. The aim of this study was to define an amino acid and protein (hydrolysate) mixture with a maximal insulinotropic effect when co-ingested with carbohydrate. Eight healthy, nonobese male subjects visited our laboratory, after an overnight fast, on 10 occasions on which different beverage compositions were tested for 2 h. During those trials the subjects ingested 0.8 g*kg(-)(1)*h(-)(1) carbohydrate and 0.4 g*kg(-)(1)*h(-)(1) of an amino acid and protein (hydrolysate) mixture. A strong initial increase in plasma glucose and insulin concentrations was observed in all trials, after which large differences in insulin response between drinks became apparent. After we expressed the insulin response as area under the curve during the second hour, ingestion of the drinks containing free leucine, phenylalanine, and arginine and the drinks with free leucine, phenylalanine, and wheat protein hydrolysate were followed by the largest insulin response (101% and 103% greater, respectively, than with the carbohydrate-only drink; P < 0.05). Insulin responses are positively correlated with plasma leucine, phenylalanine, and tyrosine concentrations. A mixture of wheat protein hydrolysate, free leucine, phenylalanine, and carbohydrate can be applied as a nutritional supplement to strongly elevate insulin concentrations.

Synthesis and characterization of specifically 14C-labeled humic model compounds for feeding trials with soil-feeding termites

The feeding activity of soil-feeding termites is considered an important factor in the turnover of soil organic matter in tropical ecosystems, but the nature of the components exploited as carbon and energy source and the consequences of the gut passage for the residual fraction are still largely obscure. In order to determine mineralization rates of specific components in feeding experiments, we prepared 14C-labeled synthetic humic model compounds by peroxidase-initiated radical polymerization of a mixture of phenolic compounds, peptides, amino acids, and carbohydrates. A general characterization of the polymerization products showed that they resembled natural humic substances prepared from tropical soil used in feeding trials with soil-feeding termites in their elemental content, infrared spectra, and molecular weight distribution. Solubility-based fractionation of chemically identical preparations, arising from selective labeling of different precursors, revealed that almost all of the label stemming from the protein precursors and approximately two-thirds stemming from the peptone and catechol precursors were recovered in the humic acid fraction. In contrast, the label of glucose or glycine was recovered almost completely in the acid-soluble fraction. High-performance gel-permeation chromatography (HP-GPC) of the humic and fulvic acid fractions combined with online radiotracer analysis showed large differences in the size distribution of the radiolabel, which depended strongly on the chemical nature of labeled precursor.

The nutraceutical benefit, part iii: honey

The nutraceutical benefit, part iii: honey

Optimization of Storage Stability of Lyophilized Actin Using Combinations of Disaccharides and Dextran

The storage stability of a dry protein depends on the structure of the dried protein, as well as on the storage temperature relative to the glass transition temperature of the dried preparation. Disaccharides are known to preserve the native conformation of a dried protein; however, the resulting Tg of the sample may be too low ensure adequate storage stability. On the other hand, formulations dried with high molecular weight carbohydrates, such as dextran, have higher glass transition temperatures, but fail to preserve native protein conformation. We tested the hypothesis that optimizing both protein structure and Tg by freeze‐drying actin with mixtures of disaccharides and dextran would result in increased storage stability compared to actin dried with either disaccharide or dextran alone. Protein structure in the dried solid was analyzed immediately after lyophilization and after storage at elevated temperatures with infrared spectroscopy, and after rehydration by infrared and circular dichroism spectroscopy. Structural results were related to the polymerization activity recovered after rehydration. Degradation was noted with storage for formulations containing either sucrose, trehalose, or dextran alone. Slight increases in Tg observed in trehalose formulations compared to sucrose formulations did not result in appreciable increases in storage stability. Addition of dextran to sucrose or trehalose increased formulation Tg without affecting the capacity of the sugar to inhibit protein unfolding during lyophilization and resulted in improved storage stability. Also, dextran provides an excellent amorphous bulking agent, which can be lyophilized rapidly with formation of strong, elegant cake structure. These results suggest that the strategy of using a mixture of disaccharide and polymeric carbohydrates can optimize protein storage stability. © 2000 Wiley‐Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 89: 199–214, 2000

Oligosaccharide profiling: the facile detection of mono-, di- and oligosaccharides by electrospray orthogonal time-of-flight mass spectrometry using 3-aminophenylboronic acid derivatization.

Monosaccharides, disaccharides and larger carbohydrates can be derivatized using 3-aminophenylboronic acid (3-APBA). This procedure is carried out at low pH (2.7-3.0) and allows the use of positive ion mode electrospray orthogonal time-of-flight mass spectrometry (ES-OTOFMS) to analyze the resulting boronate complexes. A carbohydrate profile map of a complex carbohydrate mixture, honey, was prepared which displayed superior sensitivity when compared with lithium ion cationization. Complexes formed using simple mono- and disaccharides show that facile in situ derivatization leads to an equilibrium mixture; which is reproducible for a specific set of electrospray conditions. D-Glucose could be detected at 5 microM concentration using the standard instrument spray interface. Lower detection levels of approximately 500 nM could be achieved using a nanospray device. The 3-APBA complexes are observed on instruments employing a low temperature interface (140-150 degrees C) which allows formation of the boronate species while still promoting efficient desolvation of the ions. The spectral identification of 3-APBA complexed carbohydrates in complex mixtures is facilitated by the easily observed 1 mass unit separated peak pair bearing the 1:4 ratio resulting from the natural isotopic abundance of (10)B and (11)B.

Analyzing mixtures of amino acids and carbohydrates using bi-modal integrated amperometric detection

Described in this work is a new detection methodology – bi-modal integrated amperometric detection – for identifying peaks and as a tool for solving difficult separation problems. Bi-modal integrated amperometry makes it possible to selectively detect amino acids, amino sugars, and carbohydrates following their separation by anion-exchange. Selectivity is gained by two different methods of integrating anodic current on an otherwise identical waveform. As with the single-mode integrated amperometry reported previously, the limits of detection are in the femtomole range and linear calibration plots are possible over three orders of magnitude. This new detection method does not require analyte derivatization. The practical utility of this new technique is demonstrated in the analysis of amino acids and sugars in a recombinant mammalian cell culture medium.

Genomics-assisted plant improvement to benefit human nutrition and health

Plant foods contain a bountiful array of vitamins, minerals and unique phytochemicals that are critical and/or beneficial for human health and well-being. A mixture of carbohydrates, lipids and protein (amino acids), as well as 17 mineral nutrients and 13 vitamins are essential components of the human diet. To prevent nutrient deficiencies, each dietary component must be consumed at a daily intake level at or above a defined minimum value; the level for each nutrient varies with age, sex and physiological status (e.g. pregnancy, lactation, disease-related stress). Additionally, the intake of some nutrients at higher, therapeutic levels has been associated with a reduction in risk for chronic conditions, such as cancers and cardiovascular diseases1. Because almost all essential human nutrients can be obtained from a diverse, plant-based diet (the exceptions being vitamins B12 and D), plant foods have the potential to significantly impact human nutrition and health. Unfortunately, many people in the developing world exist on a simple diet composed primarily of staple foods (e.g. rice, wheat, maize) that are poor sources of many micronutrients, and even in developed countries, the average intake of fruits and vegetables is well below government recommendations2. Therefore, efforts are under way to improve the nutrient content and composition of plant foods as a means of increasing the consumption of various essential and health-enhancing compounds3. An important new approach in this effort is the genomics-assisted strategy, used recently to improve tocopherol (vitamin E) composition in seeds4. This is the first example of increasing the vitamin level in a plant tissue by molecular manipulation.