Monosaccharide Isomers Research Articles

In-depth profiling of carbohydrate isomers in biological tissues by chemical derivatization-assisted mass spectrometry imaging

Carbohydrates play crucial regulatory roles in various physiological and pathological processes. However, the low ionization efficiency and the presence of linkage pattern, monosaccharide composition and anomeric configuration isomers make their in-depth analysis very challenging, especially for heterogeneous biological tissues. In this study, we propose a high-sensitive and isomer-specific imaging approach to visualize the spatial distributions of monosaccharide and disaccharide isomers by integrating chemical derivatization and matrix-assisted laser desorption/ionization tandem mass spectrometry imaging (MALDI-MS2I). 2-Pyridinecarbohydrazide (PYD) is developed as a novel derivatization reagent which can not only improves the MS sensitivity of carbohydrates, but also enables the identification and visualization of ketose and aldose monosaccharide isomers, as well as linkage pattern, monosaccharide composition and anomeric configuration disaccharide isomers by mass spectrometry imaging of isomer-specific MS/MS fragment ions. Moreover, we build quantitative MALDI-MS2 and MALDI-MS2I methods for disaccharide isomers based on the diagnostic fragment ions, and good linear relationships could be achieved both in solution and on glass slides. We expect that this study should provide new ideas for in-depth profiling of the spatial signatures of carbohydrates in biological tissues and lay the foundation for a deeper understanding of carbohydrates’ structure.

Mass–Energy Profiles Obtained by Quantum Chemical Computing Applied in Mass Spectrometry: A Case Study with Identification of a Group of Acetalized Monosaccharide Isomers

Accurate modeling of small molecules substantially reduces the logistical effort and time consumption to discover and then obtain chemicals with various applications. Molecular stereochemistry is fundamentally involved in the intermolecular interactions that give rise to biological activity. Establishing the configuration of the asymmetric carbon in diastereomers can be decisive in drug design. In the presented analytical technique, on the basis of quantitative structure–fragmentation relationship (QSFR), mass–energy profiles obtained by electron ionization mass spectrometry (EI-MS) for analytes are used, along with some profiles for candidate structures calculated by quantum chemical (QC) methods. Our paper establishes the analytical conditions that lead to the best matching scores of such profiles corresponding to the actual structures for some isomers of acetalized monosaccharides. The optimization was achieved by group validation of five analytes, using four independent variables: the QC method, the descriptor of calculated energy, the impact energy of electrons, and the descriptor of experimental energy. The true structures were obtained using experimental profiles obtained at low electronic impact energies, and profiles were calculated using the DFT (B3LYP/6-31G) and RM1 QC methods. The double quantification of the ionic mass and the energy that generates it, for only a few primary ions of the mass spectrum, even allows the differentiation of acetalized diastereomers.

On-tissue derivatization for isomer-specific mass spectrometry imaging and relative quantification of monosaccharides in biological tissues

Spatially-resolved profiling of tissue monosaccharides not only gives an insight into the spatial heterogeneity of monosaccharides, but also helps to decipher the possible roles of monosaccharides in biological processes. Here, we develop an on-tissue derivatization method, coupled with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) to image and quantify the aldose and ketose isomers of monosaccharide in biological tissues. A new derivatization reagent, 1-naphthaleneacethydrazide (NAH) was synthesized for the on-tissue derivatization of monosaccharides, and it significantly enhanced the imaging sensitivity of monosaccharides. Moreover, the NAH-derivatized aldose and ketose can generate isomer-specific diagnostic ions during MALDI-MS/MS analysis, and thus paves way for the isomer-specific MS imaging of aldose and ketose monosaccharides. On this basis, we further constructed a quantitative MALDI-MS imaging model based on isomer-specific diagnostic ions, and calculated the expression contents of aldose and ketose monosaccharide isomers in different tissue regions of carrot section. We expect that the development of this method should provide more precise view on the spatial distributions and contents of different monosaccharides in heterogeneous biological tissues.

Non-derivatization strategy for the comprehensive characterization of neutral monosaccharide isomers and neutral disaccharide isomers using hydrophilic interaction liquid chromatography coupled to quadrupole/time-of-flight mass spectrometry

Monosaccharide isomers and disaccharide isomers widely exist in nature, playing a key role in a number of important biological processes. However, due to high structural similarity and high polarity, the characterization of monosaccharide isomers, disaccharide isomers, as well as the analysis of monosaccharide composition of polysaccharides by a method that does not require derivatization is an ongoing challenge. Herein, we proposed a simple method for rapid discrimination of non-derivatized neutral monosaccharide, and disaccharide isomers using hydrophilic interaction liquid chromatography coupled to quadrupole/time-of-flight mass spectrometry (HILIC-Q/TOF-MS). In this work, we optimized the experimental parameters, and detailed approaches to discriminate the precursor ions, deprotonated ions, and fragment ions are proposed, as well. To discriminate the various ions, the retention times, the relative abundance (RA) of precursor ions and fragment ions at different collision energies, the relative abundance ratio (RAR) of fragment ions to deprotonated ions or precursor ions were considered for characterization of neutral monosaccharide and disaccharide isomers. Finally, this strategy was successfully applied to analyzing the monosaccharide composition of neutral disaccharides, polysaccharides, and an aqueous extract of Moringa oleifera seeds. The experimental results revealed that the HILIC-Q/TOF-MS is an effective and convenient strategy for rapid differentiation of monosaccharide isomers and disaccharide isomers, which may serve as a general platform for the analysis of neutral polysaccharides, food, medicinal plants, and herbs.

Factors in Protobiomonomer Selection for the Origin of the Standard Genetic Code.

Natural selection of specific protobiomonomers during abiogenic development of the prototype genetic code is hindered by the diversity of structural, spatial, and rotational isomers that have identical elemental composition and molecular mass (M), but can vary significantly in their physicochemical characteristics, such as the melting temperature Tm, the Tm:M ratio, and the solubility in water, due to different positions of atoms in the molecule. These parameters differ between cis- and trans-isomers of dicarboxylic acids, spatial monosaccharide isomers, and structural isomers of α-, β-, and γ-amino acids. The stable planar heterocyclic molecules of the major nucleobases comprise four (C, H, N, O) or three (C, H, N) elements and contain a single -C=C bond and two nitrogen atoms in each heterocycle involved in C-N and C=N bonds. They exist as isomeric resonance hybrids of single and double bonds and as a mixture of tautomer forms due to the presence of -C=O and/or -NH2 side groups. They are thermostable, insoluble in water, and exhibit solid-state stability, which is of central importance for DNA molecules as carriers of genetic information. In M-Tm diagrams, proteinogenic amino acids and the corresponding codons are distributed fairly regularly relative to the distinct clusters of purine and pyrimidine bases, reflecting the correspondence between codons and amino acids that was established in different periods of genetic code development. The body of data on the evolution of the genetic code system indicates that the elemental composition and molecular structure of protobiomonomers, and their M, Tm, photostability, and aqueous solubility determined their selection in the emergence of the standard genetic code.

Factors of protobiomonomer selection for the emergence the genetic code

The natural selection of specific protobiomonomers during abiogenic development of the prototype genetic code is hindered by the diversity of structural, spatial, and rotational isomers. They have identical elemental composition and molecular mass (M), but can vary significantly in their physicochemical characteristics, such as melting point Tm, the Tm : M ratio, and solubility in water, due to the different arrangement of atoms in the molecule. These parameters differ between cis- and trans-isomers of dicarboxylic acids, spatial monosaccharide isomers, and structural isomers of α-, β-, and γ-amino acids. The stable planar heterocyclic molecules of the major nucleobases comprise four (C, H, N, O) or three (C, H, N) elements and contain a single -C=C bond and two nitrogen atoms in each heterocycle involved in C-N and C=N bonds. They exist as isomeric resonance hybrids of single and double bonds and as a mixture of tautomer forms due to the presence of -C=O and/or -NH2 side groups. They are thermostable, insoluble in water, and exhibit solid-state stability, which is of central importance for DNA molecules as carriers of genetic information. In M Tm diagrams, proteinogenic amino acids and the corresponding codons are distributed in a rather ordered manner relative to the distinct clusters of purine and pyrimidine bases, reflecting the correspondence between codons and amino acids that was established in different periods of genetic code development. The body of data on the evolution of the genetic coding system indicates that the elemental composition and molecular structure of protobiomonomers, and their M, Tm, photostability, and aqueous solubility determined their selection in the emergence of the standard genetic code.

The baseline resolution of Aldo-monosaccharide enantiomers: Simplified GC–MS analyses using acetal-trifluoroacetyl derivatives for complex samples

A variety of scientific and technical fields rely on the analysis of monosaccharides (sugars). However, the multiple isomer forms of individual monosaccharides have long hampered their analyses in complex samples: significant chromatographic co-elution often leads to the loss of information on individual compounds. In addition, the chromatographic enantiomer resolution of monosaccharides has of course received less attention than molecular resolution. This would be expected in the case of rare monosaccharides, but enantiomer resolution of erythrose and threose have also received relatively little attention in the literature. Methods that are capable of the simultaneous molecular and enantiomer resolution/identification of suites of monosaccharides in single complicated mixtures are desirable. Here we report the results of attempts to resolve mixtures of the enantiomers of all three‑carbon (3C) to six‑carbon (6C) aldehyde (aldose) monosaccharides as acetal-trifluoroacetyl (acetal-TFA) derivatives by gas chromatography–mass spectrometry (GC–MS); glyceraldehyde (3C) is included as its TFA-only derivative. After a relatively simple derivatization procedure, the analyzed acetals are in the ethyl-, 2-propyl- and 2-butyl-TFA forms. Using chiral (cyclodextrin) and non-chiral (DB-17) GC columns we show that these enantiomer pairs can be baseline resolved - depending on the derivative/GC column combination - and that any single acetal/TFA combination can resolve the majority of enantiomers in a single run. Importantly, ribose and lyxose form only one significant (in abundance) stereoisomer with all derivative combinations while other monosaccharides form a maximum of only two significant stereoisomers: this greatly reduces obfuscation due to crowding on a given chromatogram. We conclude that GC–MS of acetal-TFA derivatives is the best (overall) analytical technique, to date, for the analysis of aldose-monosaccharide enantiomer ratios and reduces chromatogram clutter by favorably restricting the proliferation of monosaccharide isomers.

Fabrication of ordered polydopamine-coated carbon nanotube arrays and their electrocatalytic activities towards synergistically enhanced oxidation of ascorbate-monosaccharides and reduction of oxygen

An ordered array of single-walled carbon nanotubes coated with polydopamine (SWCNTs@PDA) is prepared using multiple voltammetry for the oxidation of ascorbate (AA)-monosaccharides, and the reduction of oxygen (O2) in enzyme-free fuel cells. The SWCNTs@PDA electrode exhibits a pair of redox peaks at the formal potential of 0.145 V (vs. SCE, 0.1 V s−1). The electrocatalytic oxidation of ascorbate enhanced by three monosaccharide isomers on SWCNTs@PDA shows the stereoisomeric effects. Glucose (Glu) has the highest ability to enhance synergistically the oxidation reaction of ascorbate while fructose (Fru) has the lowest with galactose (Gal) in between. The presence of SWCNTs@PDA arrays on carbon felt surface leads to a positive shift of 0.331 V or 0.335 V in the onset potential of O2 or H2O2 reduction. While simultaneously employing SWCNTs@PDA as anode and cathode catalysts to assemble an ascorbate-glucose fuel cell, the short-circuit current density (isc) or maximum power density (Pmax) shows a 5.2-fold or 12.7-fold increase compared with that using bare SWCNTs. The present study provides an interesting platform for the electrochemical oxidation of ascorbate enhanced recognizably by monosaccharides, as well as illustrates that the redox-active SWCNTs@PDA arrays can act as a signal amplifier to promote remarkably the redox reactions of ascorbate and glucose with O2 in fuel cells.

Monosaccharide Isomer Interconversions Become Significant at High Temperatures.

Quantum-chemical calculations show how low barriers to anomerization and shifting equilibria cause a significant presence of different monosaccharide isomers in high-temperature processes such as pyrolysis. The transition between isomeric forms of monosaccharides is long-studied, but examination has typically been limited to the solution phase and to pyranose isomers. Processes and rates of anomerization by reversible, gas-phase ring-opening and -closing reactions were predicted for the monosaccharides d-glucose, d-mannose, d-galactose, d-xylose, l-arabinose, and d-glucuronic acid. Structures and thermochemistry were computed for stable species and pericyclic transition states using CBS-QB3, and high-pressure-limit Arrhenius reaction parameters were predicted and fitted from 300 to 1000 K. Activation energies for the ring-opening reactions were 162-217 kJ/mol for four-center pericyclic separation of the lactol group but were reduced by catalytic participation of a hydroxyl group within the monosaccharide or an external R-OH group represented by an explicit water molecule, reaching activation energies as low as 97 and 67 kJ/mol, respectively. Equilibrium constants implied increasing fractions of furanose and linear aldehyde anomers with increasing temperature.

Resolution and signal-to-noise in analysis of carbohydrate isomers by graphitised carbon chromatography with charged aerosol detection

The effects of co-eluents and additives on separation and signal-to–noise ratio in analyses of monosaccharides by graphitised carbon chromatography (GCC) in combination with charged aerosol detection were studied. Design of experiments was used to model and predict the elution of two monosaccharide isomers, galactose and glucose and the corresponding amine at varying isocratic conditions, including concentration of water-soluble co-eluent, flow and temperature. The study confirmed the well-known order of eluent strength of the co-eluents investigated but showed that the eluent strength of MeOH was significantly lower than that of ACN, and at co-eluent concentrations ≥5% (v/v) IPA approached that of THF. Addition of NH3 increased retention and improved both peak shape and separation but the detector response decreased with increasing NH3 concentration lowering the signal-to-noise ratio. The best combination of response, retention and separation was obtained at 0.1% NH3. Increasing column temperature in the range of 15–50°C resulted in decreased retention times and resolution. The corresponding Van’t Hoff correlations showed negative adsorption enthalpies indicating an exothermic adsorption process driven by a decrease in entropy minimising the surface energy of the system. Isocratic elution with MeOH as co-eluent offered limited possibilities for optimisation of resolution due to the opposite effects of changes in co-eluent concentration and changes in flow rate. Elution with acetonitrile as co-eluent showed possibilities for optimisation of the resolution within the range of flow rates of 0.6-0.95mL/min and co-eluent concentrations of 0.1–0.3%, with the highest resolution predicted at 0.1% acetonitrile and a flow rate of 0.81mL/min. Saccharides in the size range DP1–4, including amino, acetamido, and deoxy sugars, were separated using a binary gradient method. Higher retention was observed for increasing degree of polymerisation (DP) and N-acetylated saccharides were retained longer than non-substituted saccharides of corresponding DP. Partial resolution of two lacto-N-tetrasaccharide positional isomers was obtained.

Origin of the blueshift of water molecules at interfaces of hydrophilic cyclic compounds.

Water molecules at interfaces of materials exhibit enigmatic properties. A variety of spectroscopic studies have observed a high-frequency motion in these water molecules, represented by a blueshift, at both hydrophobic and hydrophilic interfaces. However, the molecular mechanism behind this blueshift has remained unclear. Using Raman spectroscopy and ab initio molecular dynamics simulations, we reveal the molecular mechanism of the blueshift of water molecules around six monosaccharide isomers. In the first hydration shell, we found weak hydrogen-bonded water molecules that cannot have a stable tetrahedral water network. In the water molecules, the vibrational state of the OH bond oriented toward the bulk solvent strongly contributes to the observed blueshift. Our work suggests that the blueshift in various solutions originates from the vibrational motions of these observed water molecules.

Dissecting the role of dispersion on the quantum topology phase diagram of monosaccharide isomers

Intermolecular and intramolecular weak interactions have been described extensively with dispersion corrections from an energetics perspective. However, insights gained from a wave function view are to a lesser extent. Using two approximate density functionals B3LYP and M06-2X, together with D3BJ, DCP, and NL dispersion corrections, we have systematically explored and established the quantum topology phase diagram (QTPD) of 58 monosaccharide isomers within the framework of quantum theory of atoms in molecules for the first time. We find that merely NL dispersion corrections have an impact on the QTPD where those dubious points are further benchmarked and ruled out by the CCSD method. In addition, we use the Poincare–Hopf relation rather than the Euclidean geometry to quantify the dimensionality of a molecule. This quantum topological definition of geometry reveals that the most energetically stable monosaccharide C6H12O6 conformers are quantified as two-dimensional.

Identification of structurally closely related monosaccharide and disaccharide isomers by PMP labeling in conjunction with IM-MS/MS.

It remains particularly difficult for gaining unambiguous information on anomer, linkage, and position isomers of oligosaccharides using conventional mass spectrometry (MS) methods. In our laboratory, an ion mobility (IM) shift strategy was employed to improve confidence in the identification of structurally closely related disaccharide and monosaccharide isomers using IMMS. Higher separation between structural isomers was achieved using 1-phenyl-3-methyl-5-pyrazolone (PMP) derivatization in comparison with phenylhydrazine (PHN) derivatization. Furthermore, the combination of pre-IM fragmentation of PMP derivatives provided sufficient resolution to separate the isomers not resolved in the IMMS. To chart the structural variation observed in IMMS, the collision cross sections (CCSs) for the corresponding ions were measured. We analyzed nine disaccharide and three monosaccharide isomers that differ in composition, linkages, or configuration. Our data show that coexisting carbohydrate isomers can be identified by the PMP labeling technique in conjunction with ion-mobility separation and tandem mass spectrometry. The practical application of this rapid and effective method that requires only small amounts of sample is demonstrated by the successful analysis of water-soluble ginseng extract. This demonstrated the potential of this method to measure a variety of heterogeneous sample mixtures, which may have an important impact on the field of glycomics.

Manifesting Subtle Differences of Neutral Hydrophilic Guest Isomers in a Molecular Container by Phase Transfer.

Achieving strong host-guest interactions between synthetic hosts and hydrophilic guests in solution is challenging because solvation effects overwhelm other effects. To resolve this issue, we transferred complexes of cucurbit[7]uril (CB[7]) and monosaccharides to the gas phase and report here their intrinsic host-guest chemistry in the absence of solvation effects. It was observed that effective host-guest interactions in the gas phase mediated by ammonium cations allow the differentiation of the monosaccharide isomers in complex with CB[7] upon vibrational excitation. The potential of the unique observation was extended to a quantitative supramolecular analytical method for the monosaccharide guests. The combination of host-guest chemistry and phase transfer presented in this study is an effective approach to overcome current limitations in supramolecular chemistry.

Manifesting Subtle Differences of Neutral Hydrophilic Guest Isomers in a Molecular Container by Phase Transfer

AbstractAchieving strong host–guest interactions between synthetic hosts and hydrophilic guests in solution is challenging because solvation effects overwhelm other effects. To resolve this issue, we transferred complexes of cucurbit[7]uril (CB[7]) and monosaccharides to the gas phase and report here their intrinsic host–guest chemistry in the absence of solvation effects. It was observed that effective host–guest interactions in the gas phase mediated by ammonium cations allow the differentiation of the monosaccharide isomers in complex with CB[7] upon vibrational excitation. The potential of the unique observation was extended to a quantitative supramolecular analytical method for the monosaccharide guests. The combination of host–guest chemistry and phase transfer presented in this study is an effective approach to overcome current limitations in supramolecular chemistry.

Multidimensional Analysis of 16 Glucose Isomers by Ion Mobility Spectrometry.

Diastereomeric adducts comprising an enantiomerically pure monosaccharide analyte, a peptide, and/or an amino acid and a divalent metal ion (for 16 different monosaccharide isomers) are generated by electrospray ionization and analyzed by combined ion mobility spectrometry-mass spectrometry (IMS-MS) techniques. Mobility distributions of [l-Ser + M + H](+) (where l-Ser is l-serine and M is a given monosaccharide), [l-Phe-Gly + M + H](+) (where l-Phe-Gly is l-phenylalanine-glycine), and [Mn(II) + (l-Phe-Gly - H) + M](+) complex ions are used to determine collision cross sections (ccs in Å(2)), and groups of cross sections for different clusters are proposed as means of identifying the sugar isomers. Within one type of complex, variations in ccs do not always allow delineation between the 16 glucose isomers, but interestingly, when ccs of three different ions are combined as a spatial vector, enantiomers are partially resolved. As a result of this analysis, l-glucose, d-glucose, l-allose, d-allose, d-gulose, d-galactose, and l-mannose are delineated, and for all eight enantiomeric pairs, d and l entities display different coordinates. In addition, different combinations of amino acids, peptide, and metal ions are surveyed, and the potential for yielding unique coordinates for the generated diastereomeric complexes is assessed.

A Hierarchy of Methods for the Energetically Accurate Modeling of Isomerism in Monosaccharides.

The performance of different wave-function-based and density functional theory (DFT) methods was evaluated with respect to the prediction of relative energies for gas-phase monosaccharide isomers. A test set of 58 structures was employed, representing all forms of isomerism encountered in d-aldohexoses. The set was built from eight hexopyranose epimers by deriving subsets of isomers that include hydroxymethyl rotamers, anomers, ring conformers, furanose, and open-chain forms. Each subset of isomers spans a different energy range and involves various stereoelectronic effects. Reference energy values were obtained with coupled-cluster calculations extrapolated to the complete basis set limit, CCSD(T)/CBS. The tested CBS-extrapolated ab initio methods include various types of Møller-Plesset (MP) perturbation theory and the localized paired natural orbital coupled electron pair approach (LPNO-CEPA). Extensive benchmarking of DFT methods was carried out with 31 functionals. The results allow us to establish a hierarchy of methods that forms a reference guide for further computational studies. Among wave-function-based methods, LPNO-CEPA proved indistinguishable from CCSD(T), offering a promising alternative for a reference method that can be applied to larger systems. MP2 and SCS-MP2 follow closely, surpassing SOS-MP2 and MP3. The mPW2PLYP-D double hybrid and the Minnesota M06-2X hybrid meta-GGA are the best performing density functionals and are directly competitive with wave-function-based ab initio methods. Among the remaining functionals, B3PW91, TPSSh, mPW1PW91, and PBE0 yield the best results on average, while PBE is the best general-purpose GGA functional, surpassing meta-GGAs and several hybrids such as B3LYP. The choice of method strongly depends on the type of isomerism that needs to be considered, since many DFT methods perform well for purely conformational isomerism, but most of them fail to describe ring versus open-chain isomerism, where LYP-based GGA functionals perform particularly poorly.

Use of electrospray ionization ion‐trap tandem mass spectrometry and principal component analysis to directly distinguish monosaccharides

Carbohydrates are good source of drugs and play important roles in metabolism processes and cellular interactions in organisms. Distinguishing monosaccharide isomers in saccharide derivates is an important and elementary work in investigating saccharides. It is important to develop a fast, simple and direct method for this purpose, which is described in this study. Stock solutions of monosaccharide with a concentration of 400 μM and sodium chloride at a concentration of 10 μM were made in water/methanol (50:50, v/v). The samples were subjected to electrospray ionization ion-trap tandem mass spectrometry (ESI-MS) and the detected [2M + Na - H(2)O](+) ions were further investigated by tandem mass spectrometry (MS/MS), followed by applying principal component analysis (PCA) on the obtained MS/MS data sets. The MS/MS spectra of the [2M + Na - H(2)O](+) ions at m/z 365 for hexoses and m/z 305 for pentoses yielded unambiguous fragment patterns, while rhamnose can be directly identified by its ESI-MS [M + Na](+) ion at m/z 187. PCA showed clustering of MS/MS data of identical monosaccharide samples obtained from different experiments. By using this method, the monosaccharide in daucosterol hydrolysate was successfully identified. A new strategy was developed for differentiation of the monosaccharides using ESI-MS/MS and PCA. In MS/MS spectra, the [2M + Na - H(2)O](+) ions yielded unambiguous distinction. PCA of the archived MS/MS data sets was applied to demonstrate the spatial resolution of the studied samples. This method presented a simple and reliable way for distinguishing monosaccharides by ESI-MS/MS.

Fabrication of glucose-sensitive TiO2 ultrathin films by molecular imprinting and selective detection of monosaccharides

In this study, we extended the molecular imprinting capability of TiO2 gel to the monosaccharide family. Composite nanofilms were prepared from d-glucose and titanium n-butoxide, Ti(O–nBu)4, on a QCM electrode by the surface sol–gel process. After the d-glucose template was removed, the binding behavior of the template and other monosaccharides (d-mannose, d-galactose and d-fructose) was examined by QCM measurement The d-glucose imprinted TiO2 gel film provided sensitively mass increases for monosaccharides. The largest binding was achieved with d-glucose, showing a maximal binding ratio of 2.3 (λ = Mimp/Mnon-imp, mol/mol) between the imprinted and non-imprinted films. The other six-membered monosaccharide guests gave 44–68% binding efficiencies of that of d-glucose. It is concluded that the imprinted TiO2 gel film could efficiently discriminate the structure of monosaccharide isomers.

CARBOHYDECK: A Card Game To Teach the Stereochemistry of Carbohydrates

Identifying and differentiating monosaccharide isomers is an important educational goal in introductory biochemistry courses. However the topic is difficult for many students—in particular, chemistry nonmajors. This paper describes CARBOHYDECK, a card game that may replace or complement the lectures traditionally used in the presentation of the topic. The deck consists of cards with Fischer representations of monosaccharides. Players pick pairs of cards, and, when two isomers are thought to be found, identify the type of isomerism and defend their identification to classmates and the instructor. The game promotes learning about the diversity of carbohydrates through a discovery process. In a pilot study, the game was observed to have a strong stimulatory effect on the motivation and commitment of nonmajor students with poor chemistry backgrounds. The students realized the need to observe structural differences in compounds carefully in order to score.