Exploring Rigid and Flexible Scaffolds to Develop Potent Glucuronic Acid Glycodendrimers for Dengue Virus Inhibition.

Multivalent glycodendrimers are valuable tools for studying carbohydrate-protein interactions, and their scaffolds represent important components to increase specificity and affinity. Previous work by our group described the preparation of a tetravalent glucuronic acid rigid dendron that binds with good affinity to the dengue virus envelope protein (KD = 22 µM). Herein, the chemical synthesis and binding analysis of three new sets of rigid, semirigid, and flexible glucuronic acid-based dendrimers bearing different levels of multivalency and their interactions with the dengue virus envelope protein are described. The different oligoalkynyl scaffolds were coupled to glucuronic acid azides by a copper-catalyzed azide-alkyne cycloaddition reaction through optimized synthetic strategies to afford the desired glycodendrimers with good yields. Surface plasmon resonance studies have demonstrated that glycodendrimers 12b and 12c, with flexible scaffolds, give the best binding interactions with the dengue virus envelope protein (12b: KD = 0.487 µM and 12c: KD = 0.624 µM). Their binding constant values were 45 and 35 times higher than the one obtained in previous studies with a rigid tetravalent glucuronic acid dendron (KD = 22 µM), respectively. Molecular modeling studies were carried out in order to understand the difference in behavior observed for 12b and 12c. This work reports an efficient glycodendrimer chemical synthesis process that provides an appropriate scaffold that offers an easy and versatile strategy to find new active compounds against the dengue virus.

A Novel Lipase from Streptomyces exfoliatus DSMZ 41693 for Biotechnological Applications.

Genome mining of Streptomyces exfoliatus DSMZ 41693 has allowed us to identify four different lipase-encoding sequences, and one of them (SeLipC) has been successfully cloned and extracellularly expressed using Rhodococcus sp. T104 as a host. SeLipC was purified by one-step hydrophobic interaction chromatography. The enzyme is a monomeric protein of 27.6 kDa, which belongs to subfamily I.7 of lipolytic enzymes according to its phylogenetic analysis and biochemical characterization. The purified enzyme shows the highest activity at 60 °C and an optimum pH of 8.5, whereas thermal stability is significantly improved when protein concentration is increased, as confirmed by thermal deactivation kinetics, circular dichroism, and differential scanning calorimetry. Enzyme hydrolytic activity using p-nitrophenyl palmitate (pNPP) as substrate can be modulated by different water-miscible organic cosolvents, detergents, and metal ions. Likewise, kinetic parameters for pNPP are: KM = 49.6 µM, kcat = 57 s-1, and kcat/KM = 1.15 × 106 s-1·M-1. SeLipC is also able to hydrolyze olive oil and degrade several polyester-type polymers such as poly(butylene succinate) (PBS), poly(butylene succinate)-co-(butylene adipate) (PBSA), and poly(ε-caprolactone) (PCL). Moreover, SeLipC can catalyze the synthesis of different sugar fatty acid esters by transesterification using vinyl laurate as an acyl donor, demonstrating its interest in different biotechnological applications.

Expanding the synthesis of a library of potent glucuronic acid glycodendrons for Dengue virus inhibition.

Multivalent glycodendrons are valuable tools to mimic many structural and functional features of cell-surface glycoconjugates and its focal position scaffolds represent important components to increase specificity and affinity. Previous work in our group described the preparation of a tetravalent glucuronic acid dendron that binds with good affinity to Dengue virus envelope protein (KD = 22 µM). Herein, the chemical synthesis and binding analysis of a new library of potent glucuronic acid dendrons bearing different functional group at the focal position and different level of multivalency are described. Their chemical synthesis was performed sequentially in three stages and with good yields. Namely a) the chemical synthesis of the oligo and polyalkynyl scaffolds, b) assembling with fully protected glucuronic acid-based azide units by using a microwave assisted copper-catalysed azide-alkyne cycloaddition reaction and c) sequential deprotection of hydroxyl and carboxylic acid groups. Surface Plasmon Resonance studies have demonstrated that the valency and the focal position functional group exert influence on the interaction with Dengue virus envelope protein. Molecular modelling studies were carried out in order to understand the binding observed. This work reports an efficient glycodendrons chemical synthesis that provides appropriate focal position functional group and multivalence, that offer an easy and versatile strategy to find new active compounds against Dengue virus.

Biocatalyzed Synthesis of Glycostructures with Anti-infective Activity.

Molecules containing carbohydrate moieties play essential roles in fighting a variety of bacterial and viral infections. Consequently, the design of new carbohydrate-containing drugs or vaccines has attracted great attention in recent years as means to target several infectious diseases.Conventional methods to produce these compounds face numerous challenges because their current production technology is based on chemical synthesis, which often requires several steps and uses environmentally unfriendly reactants, contaminant solvents, and inefficient protocols. The search for sustainable processes such as the use of biocatalysts and eco-friendly solvents is of vital importance. Therefore, their use in a variety of reactions leading to the production of pharmaceuticals has increased exponentially in the last years, fueled by recent advances in protein engineering, enzyme directed evolution, combinatorial biosynthesis, immobilization techniques, and flow biocatalysis. In glycochemistry and glycobiology, enzymes belonging to the families of glycosidases, glycosyltransferases (Gtfs), lipases, and, in the case of nucleoside and nucleotide analogues, also nucleoside phosphorylases (NPs) are the preferred choices as catalysts.In this Account, on the basis of our expertise, we will discuss the recent biocatalytic and sustainable approaches that have been employed to synthesize carbohydrate-based drugs, ranging from antiviral nucleosides and nucleotides to antibiotics with antibacterial activity and glycoconjugates such as neoglycoproteins (glycovaccines, GCVs) and glycodendrimers that are considered as very promising tools against viral and bacterial infections.In the first section, we will report the use of NPs and N-deoxyribosyltransferases for the development of transglycosylation processes aimed at the synthesis of nucleoside analogues with antiviral activity. The use of deoxyribonucleoside kinases and hydrolases for the modification of the sugar moiety of nucleosides has been widely investigated.Next, we will describe the results obtained using enzymes for the chemoenzymatic synthesis of glycoconjugates such as GCVs and glycodendrimers with antibacterial and antiviral activity. In this context, the search for efficient enzymatic syntheses represents an excellent strategy to produce structure-defined antigenic or immunogenic oligosaccharide analogues with high purity. Lipases, glycosidases, and Gtfs have been used for their preparation.Interestingly, many authors have proposed the use Gtfs originating from the biosynthesis of natural glycosylated antibiotics such as glycopeptides, macrolides, and aminoglycosides. These have been used in the chemoenzymatic semisynthesis of novel antibiotic derivatives by modification of the sugar moiety linked to their complex scaffold. These contributions will be described in the last section of this review because of their relevance in the fight against the spreading phenomenon of antibiotic resistance. In this context, the pioneering in vivo synthesis of novel derivatives obtained by genetic manipulation of producer strains (combinatorial biosynthesis) will be shortly described as well.All of these strategies provide a useful and environmentally friendly synthetic toolbox. Likewise, the field represents an illustrative example of how biocatalysis can contribute to the sustainable development of complex glycan-based therapies and how problems derived from the integration of natural tools in synthetic pathways can be efficiently tackled to afford high yields and selectivity. The use of enzymatic synthesis is becoming a reality in the pharmaceutical industry and in drug discovery to rapidly afford collections of new antibacterial or antiviral molecules with improved specificity and better metabolic stability.

Antitumoral activity of 1,2,4-oxadiazoles compounds isolated from the Neowerdermannia vorwerkii in liver and colon human cancer cells.

Two unknown 1,2,4-oxadiazoles (3-(pyridin-3-yl)-5-(thiophen-3-yl)-1,2,4-oxadiazole and 5-(3-hydroxyphenyl)-3-(pyridin-3-yl)-1,2,4-oxadiazole) and one known 1,2,4-oxadiazole (5-(3-methoxyphenyl)-3-(pyridin-3-yl)-1,2,4-oxadiazole) were isolated from tubers of Neowerdermannia vorwerkii, collected from the San Juan Huancollo, Ingavi province, La Paz, Bolivia. The chemical structures of these compounds were elucidated through NMR and HRMS spectroscopic analyses. All compounds showed apoptotic capacity against the SK-HEP-1 and Caco-2 tumour cells. 5-(3-methoxyphenyl)-3-(pyridin-3-yl)-1,2,4-oxadiazole and 5-(3-hydroxyphenyl)-3-(pyridin-3-yl)-1,2, 4-oxadiazole showed slight apoptotic capacities, with an IC50 between 17.46 ± 0.75 to 15.91 ± 0.62 µM and 39.29 ± 0.98 to 34.81 ± 0.70 µM, respectively. 3-(pyridin-3-yl)-5-(thiophen-3-yl)-1,2,4-oxadiazole showed a higher apoptotic capacity with an IC50 in the range of 0.98 ± 0.11 to 0.76 ± 0.03 µM, similar to that of the positive control (Dimethylenastron).

Anti-inflammatory properties of Neowerdermannia vorwerkii Fric 'Achacana' used in treating stomach-related ailments.

ETHNO-PHARMACOLOGICAL RELEVANCE: The tuber of Neowerdermannia vorwerkii commonly known as 'Achacana' is used as an infusion in Andean countries to treat various gastrointestinal ailments, kidney and liver diseases. AIM OF THE STUDY: This study determined the anti-inflammatory activity of the aqueous extract from Neowerdermannia vorwerkii and identified the compounds related to this activity. MATERIALS AND METHODS: A bio-guided isolation of the active compounds of Neowerdermannia vorwerkii was carried out, selecting the sub-extracts and fractions depending on their anti-inflammatory activity in the Hs 738.St/Int, Hs 746T and NCI-N87 cells. RESULTS: Three compounds were obtained and characterised by nuclear magnetic resonance and mass spectrometry. These compounds are (3-(pyridin-3-yl)-5-(tiophen-3-yl)-1,2,4-oxadiazole (1), 5-(3-methoxyphenyl)-3-(pyridin-3-yl)-1,2,4-oxadiazole (2) and 5-(3-hydroxyphenyl)-3-(pyridin-3-yl)-1,2,4-oxadiazole (3). Regarding their anti-inflammatory activity, the three compounds inhibited the production of cytokines (IL-1ß, IL-6 and TNF-α), however, compound 1 was the most active, with an IC50 of 0.87 µM in all cell lines. CONCLUSION: In the present study, the anti-inflammatory activity of the aqueous extract of Neowerdermannia vorwerkii was tested and analysed, following the isolation of three 1,2,4-oxadiazoles type compounds with similar pharmacological properties.

Enzymatic Synthesis and Molecular Modelling Studies of Rhamnose Esters Using Lipase from Pseudomonas stutzeri.

Rhamnolipids are becoming an important class of glycolipid biosurfactants. Herein, we describe for the first time the enzymatic synthesis of rhamnose fatty acid esters by the transesterification of rhamnose with fatty acid vinyl esters, using lipase from Pseudomonas stutzeri as a biocatalyst. The use of this lipase allows excellent catalytic activity in the synthesis of 4-O-acylrhamnose (99% conversion and full regioselectivity) after 3 h of reaction using tetrahydrofuran (THF) as the reaction media and an excess of vinyl laurate as the acyl donor. The role of reaction conditions, such as temperature, the substrates molar ratio, organic reaction medium and acyl donor chain-length, was studied. Optimum conditions were found using 35 °C, a molar ratio of 1:3 (rhamnose:acyldonor), solvents with a low logP value, and fatty acids with chain lengths from C4 to C18 as acyl donors. In hydrophilic solvents such as THF and acetone, conversions of up to 99-92% were achieved after 3 h of reaction. In a more sustainable solvent such as 2-methyl-THF (2-MeTHF), high conversions were also obtained (86%). Short and medium chain acyl donors (C4-C10) allowed maximum conversions after 3 h, and long chain acyl donors (C12-C18) required longer reactions (5 h) to get 99% conversions. Furthermore, scaled up reactions are feasible without losing catalytic action and regioselectivity. In order to explain enzyme regioselectivity and its ability to accommodate ester chains of different lengths, homology modelling, docking studies and molecular dynamic simulations were performed to explain the behaviour observed.

Wound healing, anti-inflammatory and anti-melanogenic activities of ursane-type triterpenes from Semialarium mexicanum (Miers) Mennega.

ETHNO-PHARMACOLOGICAL RELEVANCE: The bark of Semialarium mexicanum commonly known as 'Cancerina' is used as an infusion in Central America and Mexico to treat various wound infections, as well as skin and vaginal ulcers. AIM OF THE STUDY: This study aimed to determine the wound healing, anti-inflammatory and anti-melanogenic activities of the aqueous extract of Semialarium mexicanum and to identify the compounds related to these activities. MATERIALS AND METHODS: A bio-guided isolation of the active compounds of Semialarium mexicanum was carried out, selecting the sub-extracts and fractions depending on their wound healing, anti-inflammatory and anti-melanogenic activities in the RAW 264.7, NIH/3T3 and B16-F10 cells. RESULTS: Three compounds were obtained and characterised by nuclear magnetic resonance and mass spectrometry. These compounds are (3ß)-3-Hydroxy-urs-12-en-28-oic acid (1), (3ß)-Urs-12-ene-3,28-diol (2) and (2α, 19α)-2,19-Dihydroxy-3-oxo-urs-12-en-28-oic acid (3). Regarding the anti-inflammatory activity, the three compounds inhibited the production of NF-κB and NO, however, compound 3 was the most active with IC50 values of 8.15-8.19 µM and 8.94-9.14 µM, respectively, in all cell lines. The anti-melanogenic activity of these compounds was evaluated by the inhibition of tyrosinase and melanin in the B16-F10 cell line. The three compounds showed anti-melanogenic activity, however, compound 3 was the most active with an IC50 of 8.03 µM for the inhibition of tyrosinase production, and an IC50 of 8.53 µM for the inhibition of melanin production. Finally, concerning the wound healing activity, the three compounds presented proliferative activity in all the tested cell lines, however, compound 3 showed higher cell proliferation percentages than compounds 1 and 2 (88.89-89.60% compared to 64.92-65.71% and 71.53-71.99%, respectively). CONCLUSION: The wound healing, anti-inflammatory and anti-melanogenic activity of the aqueous extract of Semialarium mexicanum was tested and analysed in the present study, after having isolated three ursane-type triterpenes.

Synthesis of Glycodendrimers with Antiviral and Antibacterial Activity.

Glycodendrimers are an important class of synthetic macromolecules that can be used to mimic many structural and functional features of cell-surface glycoconjugates. Their carbohydrate moieties perform key important functions in bacterial and viral infections, often regulated by carbohydrate-protein interactions. Several studies have shown that the molecular structure, valency and spatial organisation of carbohydrate epitopes in glycoconjugates are key factors in the specificity and avidity of carbohydrate-protein interactions. Choosing the right glycodendrimers almost always helps to interfere with such interactions and blocks bacterial or viral adhesion and entry into host cells as an effective strategy to inhibit bacterial or viral infections. Herein, the state of the art in the design and synthesis of glycodendrimers employed for the development of anti-adhesion therapy against bacterial and viral infections is described.

Enzymatic synthesis of novel fructosylated compounds by Ffase from Schwanniomyces occidentalis in green solvents.

The ß-fructofuranosidase from the yeast Schwanniomyces occidentalis (Ffase) produces potential prebiotic fructooligosaccharides (FOS) by self-transfructosylation of sucrose, being one of the highest known producers of 6-kestose. The use of Green Solvents (GS) in biocatalysis has emerged as a sustainable alternative to conventional organic media for improving product yields and generating new molecules. In this work, the Ffase hydrolytic and transfructosylating activity was analysed using different GS, including biosolvents and ionic liquids. Among them, 11 were compatible for the net synthesis of FOS. Besides, two glycerol derivatives improved the yield of total FOS. Interestingly, polyols ethylene glycol and glycerol were found to be efficient alternative fructosyl-acceptors, both substantially decreasing the sucrose fructosylation. The main transfer product of the reaction with glycerol was a 62 g L-1 isomeric mixture of 1-O and 2-O-ß-d-fructofuranosylglycerol, representing 95% of all chemicals generated by transfructosylation. Unexpectedly, the non-terminal 2-O fructo-conjugate was the major molecule catalysed during the process, while the 1-O isomer was the minor one. This fact made Ffase the first known enzyme from yeast showing this catalytic ability. Thus, novel fructosylated compounds with potential applications in food, cosmetics, and pharmaceutical fields have been obtained in this work, increasing the biotechnological interest of Ffase with innocuous GS.

Efficient Synthesis of Muramic and Glucuronic Acid Glycodendrimers as Dengue Virus Antagonists.

Carbohydrates are involved in many important pathological processes, such as bacterial and viral infections, by means of carbohydrate-protein interactions. Glycoconjugates with multiple carbohydrates are involved in multivalent interactions, thus increasing their binding strengths to proteins. In this work, we report the efficient synthesis of novel muramic and glucuronic acid glycodendrimers as potential Dengue virus antagonists. Aromatic scaffolds functionalized with a terminal ethynyl groups were coupled to muramic and glucuronic acid azides by click chemistry through optimized synthetic strategies to afford the desired glycodendrimers with high yields. Surface Plasmon Resonance studies have demonstrated that the compounds reported bind efficiently to the Dengue virus envelope protein. Molecular modelling studies were carried out to simulate and explain the binding observed. These studies confirm that efficient chemical synthesis of glycodendrimers can be brought about easily offering a versatile strategy to find new active compounds against Dengue virus.

Acceptor Specificity of ß-N-Acetylhexosaminidase from Talaromyces flavus: A Rational Explanation.

Fungal ß-N-acetylhexosaminidases, though hydrolytic enzymes in vivo, are useful tools in the preparation of oligosaccharides of biological interest. The ß-N-acetylhexosaminidase from Talaromyces flavus is remarkable in terms of its synthetic potential, broad substrate specificity, and tolerance to substrate modifications. It can be heterologously produced in Pichia pastoris in a high yield. The mutation of the Tyr470 residue to histidine greatly enhances its transglycosylation capability. The aim of this work was to identify the structural requirements of this model ß-N-acetylhexosaminidase for its transglycosylation acceptors and formulate a structure-activity relationship study. Enzymatic reactions were performed using an activated glycosyl donor, 4-nitrophenyl N-acetyl-ß-d-glucosaminide or 4-nitrophenyl N-acetyl-ß-d-galactosaminide, and a panel of glycosyl acceptors of varying structural features (N-acetylglucosamine, glucose, N-acetylgalactosamine, galactose, N-acetylmuramic acid, and glucuronic acid). The transglycosylation products were isolated and structurally characterized. The C-2 N-acetamido group in the acceptor molecule was found to be essential for recognition by the enzyme. The presence of the C-2 hydroxyl moiety strongly hindered the normal course of transglycosylation, yielding unique non-reducing disaccharides in a low yield. Moreover, whereas the gluco-configuration at C-4 steered the glycosylation into the ß(1-4) position, the galacto-acceptor afforded a ß(1-6) glycosidic linkage. The Y470H mutant enzyme was tested with acceptors based on ß-glycosides of uronic acid and N-acetylmuramic acid. With the latter acceptor, we were able to isolate and characterize one glycosylation product in a low yield. To our knowledge, this is the first example of enzymatic glycosylation of an N-acetylmuramic acid derivative. In order to explain these findings and predict enzyme behavior, a modeling study was accomplished that correlated with the acquired experimental data.

Supercritical Carbon Dioxide Antisolvent Fractionation for the Sustainable Concentration of Lavandula luisieri (Rozeira) Riv.- Mart Antimicrobial and Antioxidant Compounds and Comparison with Its Conventional Extracts.

Lavandula stoechas subsp. luisieri is a Spanish subspecies from the Lamiaceae family. Its essential oil has been traditionally used for several medical applications though little is known about other extracts. Similar to many other studies aiming to obtain traditional plant extracts to be used in different applications, this work evaluated the antioxidant and antimicrobial activities of Lavandula luisieri extracts and the correlation with their composition. Traditional hydrodistillation and ethanolic maceration were used to obtain the essential oil and the maceration extract, respectively. A green and sustainable methodology was applied to the maceration extract that was under a Supercritical Antisolvent Fractionation process to obtain a fine solid enriched in rosmarinic acid and the terpenes oleanolic and ursolic acids. Antimicrobial activities of all extracts and pure identified compounds (rosmarinic and ursolic acids) were evaluated against five bacterial strains; Listeria monocytogenes, Enterococcus faecium, Staphylococcus aureus, Salmonella Typhimurium and Escherichia coli and were compared with the pure compounds identified, rosmarinic and ursolic acids. All strains were sensitive against L. luisieri essential oil. The solid product obtained from the supercritical process was concentrated in the identified actives compared to the maceration extract, which resulted in higher antimicrobial and DPPH scavenging activities. The supercritical sustainable process provided L. luisieri compounds, with retention of their antimicrobial and antioxidant activities, in a powder exemptof organic solvents with potential application in the clinical, food or cosmetic fields.

Novel DNA Aptamers Against CCL21 Protein: Characterization and Biomedical Applications for Targeted Drug Delivery to T Cell-Rich Zones.

The chemokine (C-C motif) ligand 21 (CCL21) is a cytokine that attracts CCR7-positive cells to the T cell (paracortical) zone of lymph nodes by directional migration of these cells along the CCL21 gradient. In this article, we sought to mimic this chemotactic mechanism, by identifying a novel aptamer that binds CCL21 with high affinity. In vitro selection of DNA aptamers was performed by the Systematic Evolution of Ligands by Exponential Enrichment. Quantitative polymerase chain reaction (qPCR) and enzyme-linked oligonucleotide assay were used to screen for high-affinity aptamers against human and mouse CCL21 protein, respectively. Three such aptamers were identified. Surface plasmon resonance showed equilibrium dissociation constant (Kd) for these three aptamers in the nano to picomolar range. Cytotoxicity assays showed <10% toxicity in HEK293 and HL-60 cells. Last, in vivo biodistribution was successfully performed and CCL21 chemokine-binding aptamers were quantified within the draining lymph nodes and spleen using qPCR. Fluorescence microscopy revealed that one of the aptamers showed significantly higher presence in the paracortex than the control aptamer. The use of anti-CCL21 aptamers to mimic the chemotaxis mechanism thus represents a promising approach to achieve targeted delivery of drugs to the T cell-rich zones of the lymph node. This may be important for the treatment of HIV infection and the eradication of HIV reservoirs.

Direct Enzymatic Branch-End Extension of Glycocluster-Presented Glycans: An Effective Strategy for Programming Glycan Bioactivity.

The sequence of a glycan and its topology of presentation team up to determine the specificity and selectivity of recognition by saccharide receptors (lectins). Structure-activity analysis would be furthered if the glycan part of a glycocluster could be efficiently elaborated in situ while keeping all other parameters constant. By using a bacterial α2,6-sialyltransferase and a small library of bi- to tetravalent glycoclusters, we illustrate the complete conversion of scaffold-presented lactoside units into two different sialylated ligands based on N-acetyl/glycolyl-neuraminic acid incorporation. We assess the ensuing effect on their bioactivity for a plant toxin, and present an analysis of the noncovalent substrate binding contacts that the added sialic acid moiety makes to the lectin. Enzymatic diversification of a scaffold-presented glycan can thus be brought to completion in situ, offering a versatile perspective for rational glycocluster engineering.

Chemoenzymatic synthesis of carbohydrates as antidiabetic and anticancer drugs.

Different chemoenzymatic strategies for the preparation of carbohydrates and analogues possessing antidiabetic or anticancer activity are summarized. In this sense, some examples illustrating the use of enzymes such as aldolases, lipases or glycosidases (in some cases improved by genetic engineering techniques) are presented, showing the advantages of the implementation of chemoenzymatic protocols, which combine the flexibility of chemical synthesis with the efficiency, selectivity and sustainability of biotransformations to obtain diverse complex carbohydrates, glycoconjugates and glycomimetics.

New insights into glycopeptide antibiotic binding to cell wall precursors using SPR and NMR spectroscopy.

Glycopeptide antibiotics, such as vancomycin and teicoplanin, are used to treat life-threatening infections caused by multidrug-resistant Gram-positive pathogens. They inhibit bacterial cell wall biosynthesis by binding to the D-Ala-D-Ala C-terminus of peptidoglycan precursors. Vancomycin-resistant bacteria replace the dipeptide with the D-Ala-D-Lac depsipeptide, thus reducing the binding affinity of the antibiotics with their molecular targets. Herein, studies of the interaction of teicoplanin, teicoplanin-like A40926, and of their semisynthetic derivatives (mideplanin, MDL63,246, dalbavancin) with peptide analogues of cell-wall precursors by NMR spectroscopy and surface plasmon resonance (SPR) are reported. NMR spectroscopy revealed the existence of two different complexes in solution, when the different glycopeptides interact with Ac2KdAlaDAlaOH. Despite the NMR experimental conditions, which are different from those employed for the SPR measurements, the NMR spectroscopy results parallel those deduced in the chip with respect to the drastic binding difference existing between the D-Ala and the D-Lac terminating analogues, confirming that all these antibiotics share the same primary molecular mechanism of action and resistance. Kinetic analysis of the interaction between the glycopeptide antibiotics and immobilized AcKdAlaDAlaOH by SPR suggest a dimerization process that was not observed by NMR spectroscopy in DMSO solution. Moreover, in SPR, all glycopeptides with a hydrophobic acyl chain present stronger binding with a hydrophobic surface than vancomycin, indicating that additional interactions through the employed surface are involved. In conclusion, SPR provides a tool to differentiate between vancomycin and other glycopeptides, and the calculated binding affinities at the surface seem to be more relevant to in vitro antimicrobial activity than the estimations from NMR spectroscopy analysis.

Applied biotransformations in green solvents.

The definite interest in implementing sustainable industrial technologies has impelled the use of biocatalysts (enzymes or cells), leading to high chemo-, regio- and stereoselectivities under mild conditions. As usual substrates are not soluble in water, the employ of organic solvents is mandatory. We will focus on different attempts to combine the valuable properties of green solvents with the advantages of using biocatalysts for developing cleaner synthetic processes.

Binding studies of adhesion/growth-regulatory galectins with glycoconjugates monitored by surface plasmon resonance and NMR spectroscopy.

Functionalized fluorescent glycans have the potential to act as tools to detect and analyze protein-carbohydrate interactions. We present here a facile strategy for immobilization of functionalized lactose as a model disaccharide. Bioactivity was tested with three members of the adhesion/growth-regulatory galectins family in different types of assay, i.e. matrix in surface plasmon resonance (SPR), free ligand in solution by STD/trNOESY and docking measurements. In all cases, the activity of the disaccharide was maintained. The attachment of this new fluorescent glycoconjugate to the surface results in a well-defined interface, enabling desired orientational flexibility and enhanced access of binding partners. The results indicate that this new glycoconjugate exhibits binding affinity to galectin-1, 3 and CG-16. Kinetic analysis of the interaction between these galectins and immobilized glycoconjugate by SPR yielded a K(D) of 1.01 mM for galectin-1, 83.5 microM for galectin-3 and 0.28 mM for CG-16. No major contacts to the aglyconic part were detected, which might compromise the specificity of the binding process with other headgroups. Thus, testing these proteins offers the potential for medical applications to detect these endogenous effectors or further derivatives and characterize their carbohydrate specificity.