Carbohydrate Sugar Research Articles

Effect of carbohydrate sugars as a capping agent on the size and morphology of pure Zn2SnO4 nanostructures and their optical properties

Pure Zn2SnO4 nanostructures were prepared via simple and rapid co-precipitation approach in presence of different carbohydrate sugars as a green capping agents. The effect of different carbohydrate sugars such as glucose, sucrose and starch on the size, morphology and optical properties of Zn2SnO4 nanostructures were investigated. The results demonstrated that applying the appropriate amount of sugars could be effective in particle size, morphology and optical properties control.

Chemoprevention of Low-Molecular-Weight Citrus Pectin (LCP) in Gastrointestinal Cancer Cells

Background & Aims: Low-molecular-weight citrus pectin (LCP) is a complex polysaccharide that displays abundant galactosyl (i.e., sugar carbohydrate) residues. In this study, we evaluated the anti-tumor properties of LCP that lead to Bcl-xL -mediated dampening of apoptosis in gastrointestinal cancer cells.Methods: We used AGS gastric cancer and SW-480 colorectal cancer cells to elucidate the effects of LCP on cell viability, cell cycle and apoptosis in cultured cells and tumor xenografts.Results: Significantly decreased cell viabilities were observed in LCP treated AGS and SW-480 cells (P<0.05). Cell cycle-related protein expression, such as Cyclin B1, was also decreased in LCP treated groups as compared to the untreated group. The AGS or SW-480 cell-line tumor xenografts were significantly smaller in the LCP treated group as compared the untreated group (P<0.05). LCP treatment decreased Galectin-3 (GAL-3) expression levels, which is an important gene in cancer metastasis that results in reversion of the epithelial-mesenchymal transition (EMT), and increased suppression of Bcl-xL and Survivin to promote apoptosis. Moreover, results demonstrated synergistic tumor suppressor activity of LCP and 5-FU against gastrointestinal cancer cells both in vivo and in vitro.Conclusions: LCP effectively inhibits the growth and metastasis of gastrointestinal cancer cells, and does so in part by down-regulating Bcl-xL and Cyclin B to promote apoptosis, and suppress EMT. Thus, LCP alone or in combination with other treatments has a high potential as a novel therapeutic strategy to improve the clinical therapy of gastrointestinal cancer.

Lectin histochemistry ofKudoa septempunctatagenotype ST3-infected muscle of olive flounder (Paralichthys olivaceus)

The localization of carbohydrate terminals in Kudoa septempunctata ST3-infected muscle of olive flounder (Paralichthys olivaceus) was investigated using lectin histochemistry to determine the types of carbohydrate sugar residues expressed in Kudoa spores. Twenty-one lectins were examined, i.e., N-acetylglucosamine (s-WGA, WGA, DSL-II, DSL, LEL, STL), mannose (Con A, LCA, PSA), galactose/N-acetylgalactosamine (RCA12, BSL-I, VVA, DBA, SBA, SJA, Jacalin, PNA, ECL), complex type N-glycans (PHA-E and PHA-L), and fucose (UEA-I). Spores encased by a plasmodial membrane were labeled for the majority of these lectins, with the exception of LCA, PSA, PNA, and PHA-L. Four lectins (RCA 120, BSL-I, DBA, and SJA) belonging to the galactose/N-acetylgalactosamine group, only labeled spores, but not the plasmodial membrane. This is the first confirmation that various sugar residues are present in spores and plasmodial membranes of K. septempunctata ST3.

Sol–gel auto combustion synthesis of BaFe12O19 nanoceramics by using carbohydrate sugars as a novel reducing agent

In this paper, barium hexaferrite nanostructures have been successfully synthesized via sol–gel auto combustion method based on the reaction between Ba(NO3)2 and Fe(NO3)3·9H2O in water, in the presence of carbohydrate sugar as fuel, reducing and capping agent. The products were characterized by X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy analysis. To investigate the effects of calcination temperature, the Ba2+ molar ratio to Fe3+ and the type of sugar on the morphology of products and finding optimal condition, several experiments were carried out. It was found that the phase and morphology of products could be influenced by these parameters. Vibrating sample magnetometer (VSM) was used to study the magnetic properties of BaFe12O19 samples. The uniform nanoparticles are produced when the maltose is used as the reduction and the molar ratio of Fe3+ to Ba2+ reaches 12. The resulted product has the properties of the hard magnetic material, so, it has got the specific saturation magnetization and coercivity 48emu/g and 5000Oe, respectively.

Spray drying and post-processing production of highly-porous lactose particles using sugars as templating agents

The possibility of using different carbohydrate sugars, such as maltose, sucrose, glucose, and fructose, as templating agents to produce highly-porous lactose particles with high degrees of crystallinity in a new templating process has been investigated. The new production process includes spray drying of the lactose (core material) solutions containing different types of ethanol-soluble templating sugars and then removing the templates in a post-treatment process involving ethanol-washing the spray-dried particles. Gravimetric moisture sorption tests and modulated scanning calorimetry (MDSC) have been used to study the effect of different concentrations of templating sugars on in-process crystallization of lactose during the spray-drying step and its effect on the BET surface areas of the final processed particles after ethanol washing. The results showed significant reductions in process yield and glass-transition temperatures of the spray-dried powders and considerable increases in the degree of crystallinity of the lactose in spray-dried powders, as the templating-sugar concentrations were increased. Spray-dried powders containing sucrose and maltose as templating materials had lower degrees of crystallinity, which resulted in higher porosities and BET surface areas of around 20±1 and 18.2±0.6m2/g, respectively. The results of this study have implications in choosing the proper processing conditions (type of templating agent and its concentration) to control in-process crystallization of lactose during spray-drying to produce highly-porous engineered particles.

Mapping Moisture Sorption Through Carbohydrate Composite Glass with Fourier Transform Near-Infrared (FT-NIR) Hyperspectral Imaging

Inherent changes in foods during storage are often caused by water sorption or desorption that often results in product matrix instability. Water sorption behavior differs depending on the matrix through which it moves. Often, concurrent phenomenon such as crystallization modifies water’s movement. We describe a novel use of hyperspectral imaging combined with Fourier Transform Near Infrared (FT-NIR) spectroscopy to map where water molecules are in two dimensions while concurrently quantifying the crystallization motif as water sorbs into a carbohydrate matrix over a month’s storage time. This methodology allows us to identify and quantify sucrose crystals formed within a carbohydrate matrix while also mapping water migration through this complex matrix. We compared corn syrup/sucrose blends where sucrose is supersaturated (high sucrose, HS), sucrose is below saturation (low sucrose, LS), sucrose below saturation with embedded sucrose crystals (LSS) and maltotriose is supersaturated within a corn syrup matrix (high maltotriose, LSM). This FT-NIR method was used to characterize water sorption through a carbohydrate matrix over time and measured both the propensity of the systems to form sucrose crystals and the influence sucrose crystals have on water sorption. We observed water diffusion was slower in lower sugar carbohydrate glasses, and the process of sorption was different. Amorphous systems supersaturated in sucrose allow crystallization when sufficient water is sorbed and thus, this concurrent action disrupts normal Fickian diffusion. The water front compresses to a narrow band as it sorbs through the matrix. The presence of embedded crystals in an amorphous matrix slows overall water penetration through the matrix by convoluting the path of moving water molecules. This did not appear to change the rate of diffusion. Experiments with maltotriose at supersaturation concentration showed the crystallization rate was slower than sucrose. Thus, pure maltotriose is not a practical solution as a potential replacement for sucrose to slow sorption in food systems.

Solazyme: "unlocking the power of microalgae: a new source of sustainable and renewable oils"

• The technology platform of Solazyme: Solazyme´s biotechnology platform transforms a wide variety of sugars into renewable oils with high added value, using microalgae, microorganisms that are naturally capable of storing energy in the form of oil. Solazyme's technology enables the conversion of this feedstock into oils for a variety of applications including chemical, cosmetic, food and fuel. Unique to Solazyme's process is their proprietary ability to tailor oils, meaning that for the first time in the history, Solazyme has the ability to design oil profiles rather than simply use what's available in nature today. Through its world class tailoring capabilities, Solazyme is coupling proprietary strains of algae with standard industrial biotechnology; converting what the earth produces naturally- carbohydrate sugars- into what society needs most - oil. • The existing source of oils × new source of oil: While the physical and chemical characteristics of conventional oils have traditionally been dictated by oils found in nature, or blends derived from them, this is no longer the case. Solazyme has created a new paradigm that enables the company to design and produce novel tailored oils that cannot be achieved through blending of existing oils alone. This core competency has created an incredible market opportunity. Solazyme´s platform enables the production of renewable oils with different carbon chain lengths, saturation levels and profiles simply by changing the microalgae strain used in the fermenter. • Solazyme renewable oils - the microalgae: Through Solazyme's industrial biotechnology platform, the company is able to harness the oil-producing capability of microalgae, an organism that has evolved naturally to produce oil prolifically and efficiently, making it an ideal organism for industrial fermentation. The company's technology allows for the optimization of oil profiles with different carbon lengths, saturation levels and functional groups to modify important oil characteristics, such as flash point, pour point, cloud point, oxidative stability, smoke point, and viscosity, thus enabling much more stable and sustainable end products. Solazyme's platform is also feedstock flexible and can utilize a wide variety of renewable plant-based sugars, such as sucrose, dextrose, and sugar from other sustainable biomass sources including cellulosics. Utilizing standard industrial fermentation equipment to efficiently scale and accelerate microalgae's natural oil production time to a few days, Solazyme feeds their proprietary, oil-producing microalgae plant-based sugars in enclosed fermentation tanks, where they are in effect utilizing indirect photosynthesis, in contrast to the traditional open-pond approach. • Markets: Solazyme leverages their proprietary biotechnology platform to tailor oils that address major markets served by conventional oils: transportation fuels, chemicals, skin and personal care products, nutritionals, among many others. • Sustainability and safety - breaking paradigms: Solazyme oils address many of the challenges associated with traditional oils, such as supply constraints, volatile pricing, and potentially negative and irreversible environmental effects. The drop-in nature of Solazyme's tailored oils enables compatibility with existing production, refining, and distribution infrastructures in each of its target markets. Solazyme´s algal oil are fully traceable back to their source of origin and are more sustainable than any other plant-based or petroleum-based oil. They are produced locally and therefore environmental and logistic costs are lower; feedstock comes from the sugar/alcohol industry, a closed carbon system; Solazyme's oil has the lowest GHG profile as compared to any other plant-based and petroleum-based oils.

Identification of Fusarium oxysporum Genes Associated with Lignocellulose Bioconversion Competency

Fusarium oxysporum can convert straw to ethanol via consolidated bioprocessing (CBP)—a two-stage process that firstly involves aerobic saccharification and thereafter an oxygen-limiting fermentation phase. The efficacy of CBP is dependent upon the fungal strain used. Using suppression subtractive hybridisation (SSH), a total of 210 transcripts were identified as being overexpressed in a high as compared to low efficacy CBP strain in the aerobic and oxygen-limiting growth stages on a straw/bran mix. These transcripts encode proteins assigned to various categories, including carbohydrate metabolism, energy, protein and sugar transport and detoxification. Real-time RT-PCR analysis of 12 transcripts, including an endoglucanase III (EGIII), a novel ricin toxin A1 chain-like protein (RTA1), and two unknown transcripts (JX308289 and JX308290) validated the SSH findings. Post-transcriptional silencing of EGIII, RTA1 and an unknown transcript JX308289 in F. oxysporum strain 11C significantly reduced the capacity of the fungus to produce ethanol from a straw/bran mix. Thus these and other genes identified in this study are likely factors that determine the efficacy of CBP and such genes can be used as candidates for enhancing microbial ethanol production from straw and other lignocellulosic substrates.

Extracting glycan motifs using a biochemicallyweighted kernel.

Carbohydrates, or glycans, are one of the most abundant and structurally diverse biopolymers constitute the third major class of biomolecules, following DNA and proteins. However, the study of carbohydrate sugar chains has lagged behind compared to that of DNA and proteins, mainly due to their inherent structural complexity. However, their analysis is important because they serve various important roles in biological processes, including signaling transduction and cellular recognition. In order to glean some light into glycan function based on carbohydrate structure, kernel methods have been developed in the past, in particular to extract potential glycan biomarkers by classifying glycan structures found in different tissue samples. The recently developed weighted qgram method (LK-method) exhibits good performance on glycan structure classification while having limitations in feature selection. That is, it was unable to extract biologically meaningful features from the data. Therefore, we propose a biochemicallyweighted tree kernel (BioLK-method) which is based on a glycan similarity matrix and also incorporates biochemical information of individual q-grams in constructing the kernel matrix. We further applied our new method for the classification and recognition of motifs on publicly available glycan data. Our novel tree kernel (BioLK-method) using a Support Vector Machine (SVM) is capable of detecting biologically important motifs accurately while LK-method failed to do so. It was tested on three glycan data sets from the Consortium for Functional Glycomics (CFG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) GLYCAN and showed that the results are consistent with the literature. The newly developed BioLK-method also maintains comparable classification performance with the LK-method. Our results obtained here indicate that the incorporation of biochemical information of q-grams further shows the flexibility and capability of the novel kernel in feature extraction, which may aid in the prediction of glycan biomarkers.

Extraction of species-specific glycan substructures.

Glycans, which are carbohydrate sugar chains attached to some lipids or proteins, have a huge variety of structures and play a key role in cell communication, protein interaction and immunity. The availability of a number of glycan structures stored in the KEGG/GLYCAN database makes it possible for us to conduct a large-scale comparative research of glycans. In this paper, we present a novel approach to compare glycan structures and extract characteristic glycan substructures of certain organisms. In the algorithm we developed a new similarity measure of glycan structures taking into account of several biological aspects of glycan synthesis and glycosyltransferases, and we confirmed the validity of our similarity measure by conducting experiments on its ability to classify glycans between organisms in the framework of a support vector machine. Finally, our method successfully extracted a set of candidates of substructrues which are characteristic to human, rat, mouse, bovine, pig, chicken, yeast, wheat and sycamore, respectively. We confirmed that the characteristic substructures extracted by our method correspond to the substructures which are known as the species-specific sugar chain of gamma-glutamyltranspeptidases in the kidney.

Effects of carbohydrate sugars and artificial sweeteners on appetite and the secretion of gastrointestinal satiety peptides

In vitro, both carbohydrate sugars and artificial sweeteners (AS) stimulate the secretion of glucagon-like peptide-1 (GLP-1). It has been suggested that the gut tastes sugars and AS through the same mechanisms as the tongue, with potential effects on gut hormone release. We investigated whether the human gut responds in the same way to AS and carbohydrate sugars, which are perceived by lingual taste as equisweet. We focused on the secretion of gastrointestinal (GI) satiety peptides in relation to appetite perception. We performed a placebo-controlled, double-blind, six-way, cross-over trial including twelve healthy subjects. On separate days, each subject received an intragastric infusion of glucose, fructose or an AS (aspartame, acesulfame K and sucralose) dissolved in 250ml of water or water only (control). In a second part, four subjects received an intragastric infusion of the non-sweet, non-metabolisable sugar analogue 2-deoxy-d-glucose. Glucose stimulated GLP-1 (P=0·002) and peptide tyrosine tyrosine (PYY; P=0·046) secretion and reduced fasting plasma ghrelin (P=0·046), whereas fructose was less effective. Both carbohydrate sugars increased satiety and fullness (albeit not significantly) compared with water. In contrast, equisweet loads of AS did not affect gastrointestinal peptide secretion with minimal effects on appetite. 2-Deoxy-d-glucose increased hunger ratings, however, with no effects on GLP-1, PYY or ghrelin. Our data demonstrate that the secretion of GLP-1, PYY and ghrelin depends on more than the detection of (1) sweetness or (2) the structural analogy to glucose.

Conversion of rice straw to bio-based chemicals: an integrated process using Lactobacillus brevis

Commercialization of lignocellulosic biomass as a feedstock for bio-based chemical production is problematic due to the high processing costs of pretreatment and saccharifying enzymes combined with low product yields. Such low product yield can be attributed, in large part, to the incomplete utilization of the various carbohydrate sugars found in the lignocellulosic biomass. In this study, we demonstrate that Lactobacillus brevis is able to simultaneously metabolize all fermentable carbohydrates in acid pre-processed rice straw hydrolysate, thereby allowing complete utilization of all released sugars. Inhibitors present in rice straw hydrolysate did not affect lactic acid production. Moreover, the activity of exogenously added cellulases was not reduced in the presence of growing cultures of L. brevis. These factors enabled the use of L. brevis in a process termed simultaneous saccharification and mixed sugar fermentation (SSMSF). In SSMSF with L. brevis, sugars present in rice straw hydrolysate were completely utilized while the cellulase maintained its maximum activity due to the lack of feedback inhibition from glucose and/or cellobiose. By comparison to a sequential hydrolysis and fermentation process, SSMSF reduced operation time and the amount of cellulase enzyme necessary to produce the same amount of lactic acid.

A weighted q-gram method for glycan structure classification

BackgroundGlycobiology pertains to the study of carbohydrate sugar chains, or glycans, in a particular cell or organism. Many computational approaches have been proposed for analyzing these complex glycan structures, which are chains of monosaccharides. The monosaccharides are linked to one another by glycosidic bonds, which can take on a variety of comformations, thus forming branches and resulting in complex tree structures. The q-gram method is one of these recent methods used to understand glycan function based on the classification of their tree structures. This q-gram method assumes that for a certain q, different q-grams share no similarity among themselves. That is, that if two structures have completely different components, then they are completely different. However, from a biological standpoint, this is not the case. In this paper, we propose a weighted q-gram method to measure the similarity among glycans by incorporating the similarity of the geometric structures, monosaccharides and glycosidic bonds among q-grams. In contrast to the traditional q-gram method, our weighted q-gram method admits similarity among q-grams for a certain q. Thus our new kernels for glycan structure were developed and then applied in SVMs to classify glycans.ResultsTwo glycan datasets were used to compare the weighted q-gram method and the original q-gram method. The results show that the incorporation of q-gram similarity improves the classification performance for all of the important glycan classes tested.ConclusionThe results in this paper indicate that similarity among q-grams obtained from geometric structure, monosaccharides and glycosidic linkage contributes to the glycan function classification. This is a big step towards the understanding of glycan function based on their complex structures.

Modified silica surface by phenylboronic acid derivatives as effective sugar sensor

Abstract Silica surface was modified with phenylboronic acid derivatives. The structures of the functionalized supports were characterized by FT-IR spectroscopy, 13C CP/MAS NMR spectrometry, elemental and thermogravimetric analysis. The solid supports were effectively applied as artificial receptors for sugars in aqueous solutions. Alizarin Red S. (ARS) was used to detect colour change upon carbohydrate (sugar) binding. The association constants of the supports studied-ARS complex and the functionalized silica-sugar (glucose) complex were calculated. The parameters obtained were comparable with those for the phenylboronic acids used for the silica gel modification. The competitive binding of the functionalized silica surface with ARS and sugar were studied by UV/VIS measurements.

Mining significant tree patterns in carbohydrate sugar chains

Carbohydrate sugar chains or glycans, the third major class of macromolecules, hold branch shaped tree structures. Glycan motifs are known to be two types: (1) conserved patterns called 'cores' containing the root and (2) ubiquitous motifs which appear in external parts including leaves and are distributed over different glycan classes. Finding these glycan tree motifs is an important issue, but there have been no computational methods to capture these motifs efficiently. We have developed an efficient method for mining motifs or significant subtrees from glycans. The key contribution of this method is: (1) to have proposed a new concept, 'á-closed frequent subtrees', and an efficient method for mining all these subtrees from given trees and (2) to have proposed to apply statistical hypothesis testing to rerank the frequent subtrees in significance. We experimentally verified the effectiveness of the proposed method using real glycans: (1)We examined the top 10 subtrees obtained by our method at some parameter setting and confirmed that all subtrees are significant motifs in glycobiology. (2) We applied the results of our method to a classification problem and found that our method outperformed other competing methods, SVM with three different tree kernels, being all statistically significant. Supplementary data are available at Bioinformatics online.

A new efficient probabilistic model for mining labeled ordered trees applied to glycobiology

Mining frequent patterns from large datasets is an important issue in data mining. Recently, complex and unstructured (or semi-structured) datasets have appeared as targets for major data mining applications, including text mining, web mining and bioinformatics. Our work focuses on labeled ordered trees, which are typically semi-structured datasets. In bioinformatics, carbohydrate sugar chains, or glycans, can be modeled as labeled ordered trees. Glycans are the third major class of biomolecules, having important roles in signaling and recognition. For mining labeled ordered trees, we propose a new probabilistic model and its efficient learning scheme which significantly improves the time and space complexity of an existing probabilistic model for labeled ordered trees. We evaluated the performance of the proposed model, comparing it with those of other probabilistic models, using synthetic as well as real datasets from glycobiology. Experimental results showed that the proposed model drastically reduced the computation time of the competing model, keeping the predictive power and avoiding overfitting to the training data. Finally, we assessed our results on real data from a variety of biological viewpoints, verifying known facts in glycobiology.

The role of motivation in the performance of conditioned reflex switching of a maze skill in response to substitution of food reward quality in ants of the species Myrmica rubra

The characteristics of learning in ants - active Myrmica rubra foragers - were studied in a maze at different levels of colony carbohydrate food need with reinforcement consisting of carbohydrate (sugar syrup) or protein (pupae of Lasius niger ants). Measures of the maze skill during learning reinforced with syrup were somewhat worse than those during learning reinforced with pupae, especially in terms of time-based measures. Ants were able to modify the acquired conditioned reflex reaction when the quality of reinforcement changed. At high levels of food need (" hungry" colony), substitution of syrup with larvae and vice versa was followed by transformation of the previously formed skill; this occurred at both experimental periods (training and testing). At low levels of motivation ("sated colony"), the optimized maze habit formed with protein reinforcement was replaced in the test with carbohydrate reinforcement by a "stochastic," unoptimized behavior with a dominance of investigative activity. These experiments demonstrated that conditioned reflex switching can occur in higher social insects - ants - in which the different forms depend on the level of colony need for food and, respectively, on the level of social food-related motivation of forager ants. The special importance of using the switch activating the corresponding motivational system before changing the reinforcement food quality is emphasized.

Hydro-MRI of the Small Bowel: Effect of Contrast Volume, Timing of Contrast Administration, and Data Acquisition on Bowel Distention

The purpose of this study was to assess oral contrast agents, volumes of the agents, and time points of data acquisition in regard to small-bowel distention and patient acceptance. Six healthy volunteers underwent imaging on 16 different days. Four volumes (450, 900, 1,350, and 1,800 mL) of each of the four contrast compounds (0.2% locust bean gum plus 2.5% mannitol, VoLumen containing 2.0% sorbitol, VoLumen containing 1.4% sorbitol, and tap water) were used. Two-dimensional true fast imaging with steady-state free precession data sets were acquired at 5-minute intervals after contrast ingestion. Distention values for small-bowel segments (duodenum, proximal and distal jejunum, ileum) and occurrence of side effects were documented. Analysis of bowel distention revealed significantly greater distention for all carbohydrate sugar alcohol-containing solutions compared with water but no significant difference among the three contrast agents. Sufficient duodenal distention was achieved with 900 mL of any of the contrast agents, but imaging had to be performed soon after ingestion. For MRI of the distal jejunum and ileum, a volume of 1,350 mL is preferable, and the time point of data acquisition plays a minor role. Ingestion of 1,800 mL of the carbohydrate sugar alcohol solutions led to a significantly higher rate of side effects such as abdominal cramps than did ingestion of smaller volumes. The data indicate that sufficient contrast consumption and optimal timing of data acquisition are essential to distention of the small bowel. Oral contrast agent protocols should be adapted to the bowel region in question.

ProfilePSTMM: capturing tree-structure motifs in carbohydrate sugar chains

Carbohydrate sugar chains, or glycans, are considered the third major class of biomolecules after DNA and proteins. They consist of branching monosaccharides, starting from a single monosaccharide. They are extremely vital to the development and functioning of multicellular organisms because they are recognized by various proteins to allow them to perform specific functions. Our motivation is to study this recognition mechanism using informatics techniques from the data available. Previously, we introduced a probabilistic sibling-dependent tree Markov model (PSTMM), which we showed could be efficiently trained on sibling-dependent tree structures and return the most likely state paths. However, it had some limitations in that the extra dependency between siblings caused overfitting problems. The retrieval of the patterns from the trained model also involved manually extracting the patterns from the most likely state paths. Thus we introduce a profilePSTMM model which avoids these problems, incorporating a novel concept of different types of state transitions to handle parent-child and sibling dependencies differently. Our new algorithms are more efficient and able to extract the patterns more easily. We tested the profilePSTMM model on both synthetic (controlled) data as well as glycan data from the KEGG GLYCAN database. Additionally, we tested it on glycans which are known to be recognized and bound to proteins at various binding affinities, and we show that our results correlate with results published in the literature.

Gold Glyconanoparticles for Mimics and Measurement of Metal Ion-Mediated Carbohydrate−Carbohydrate Interactions

To mimic and measure calcium ion-mediated carbohydrate-carbohydrate interactions, four lactose derivatives have been synthesized for assembly on gold nanoparticles. The series of lactose derivatives varied by the length of the thiolated ethylene glycol anchor chain [O(CH2CH2O)(m)CH2CH2SH; where m = 0, 1, 2, and 3] used to self-assemble the carbohydrates to the preformed gold nanoparticles of ca. 16 nm diameter. Upon addition of calcium ions to the lactose-stabilized nanoparticles, rapid carbohydrate-carbohydrate interactions were visualized and subsequently measured using UV-visible spectrometry and transmission electron microscopy (TEM). The nanoparticle aggregates formed via metal-mediated carbohydrate-carbohydrate interactions could be readily redispersed through the addition of EDTA. Multiple reaggregation and redispersion cycles were achieved, confirming that the aggregation process was due to metal ion-mediated carbohydrate interactions rather than calcium chelation by residual citrate ions on the particle surface. The essential involvement of the lactose moiety in Ca2+ complexation was shown by control measurements on related D-glucose-derivatized nanoparticles, where a significantly reduced aggregation response was obtained only at high ion concentrations. Other group 2 metal ions with radii larger than that of calcium, viz., barium and strontium, were also shown to mediate the aggregation of the lactose-stabilized nanoparticles. The induced aggregation of the lactose nanoparticles was determined to be quantitatively dependent upon the calcium ion concentration. Furthermore, the analytical sensitivity of the calcium-induced aggregation and the linear dynamic range were dependent on the length of the ethylene glycol anchor chain. The shortest ethylene glycol chain (m = 0) gave the most sensitive response with the optimum limit of detection (0.8 mM Ca2+), whereas the longest ethylene glycol chain (m = 3) provides a measurement of calcium ion concentration over the largest linear dynamic range (10-35 mM Ca2+). This work has shown that the self-assembled deposition of lactose derivatives on gold nanoparticles provides multivalent carbohydrate surfaces that can be used as mimics for the measurement of biologically relevant carbohydrate-carbohydrate interactions. Additionally, this study has highlighted the importance of the structure and length of the ligand that anchors the carbohydrate sugar to the gold particle surface to facilitate such carbohydrate interactions and for "tuning" the analytical characteristics of bioassays developed using metal nanoparticle technology.