177,117 research outputs found
Chemoenzymatic Synthesis of Alkyl Glycoside Fatty Acid Esters and Investigation of their Emulsifying Properties
No full textSugar fatty acid esters (SFAEs) are non-ionic surfactants that are characterized by excellent surface and interfacial tension reduction capability, low toxicity, and biodegradability. These features make SFAEs extremely promising for industrial applications as emulsifiers in the cosmetic and food sectors.[1] Interestingly, SFAEs can be obtained from renewable resources (from industrial waste and biomass) by enzymatic and/or chemoenzymatic approaches, thus answering the need for evermore sustainable and circular chemistry.[2,3]
6-O-Lauroyl-, 6-O-palmitoyl- and 6-O-stearoyl-1-O-butyl glucopyranosides were enzymatically synthesized by reacting n-butyl glucoside with molten fatty acids in an easily scalable solvent-free system. Derivatization of glucose as an alkyl glucoside before the esterification reaction played a key role to circumvent the striking different solubility of glucose and fatty acids. The physico-chemical properties of these tensides, such as interfacial tension features, W/O emulsification capability and W/O stability over time were deeply investigated.[4]
References
1. N.S. Neta, J.A. Teixeira, L.R. Rodrigues, Crit. Rev. Food Sci. Nutr. 2015, 5, 595.
2. A.R. Alcántara, P. Domínguez de María, J.A. Littlechild, M. Schürmann, R.A. Sheldon, R. Wohlgemuth, ChemSusChem 2022, e202102709.
3. T. Keijer, Nat. Chem. 2019, 11, 190.
4. S. Sangiorgio, E. Pargoletti, M. Rabuffetti, M.S. Robescu, R. Semproli, D. Ubiali, G. Cappelletti, G. Speranza, under review
This work was financially supported by Cariplo Foundation (Italy) (call: “Circular Economy for a sustainable future 2020”, project BioSurf, ID 2020-1094)
Sustainable synthesis of biosurfactants from renewable resources
No full textSFAEs (Sugar-Fatty Acid Esters) are a class of non-ionic surfactants characterized by excellent surface and interfacial tension reduction capability, low toxicity and biodegradability. Depending on their carbon chain length and the nature of the sugar head group, SFAEs can cover a wide range of hydrophilic-lipophilic balance (HLB) values, which result in tunable surfactant properties. Moreover, SFAEs can be obtained from renewable resources (i.e. industrial waste and biomass) by enzymatic and/or chemoenzymatic approaches, thus answering the need for sustainable and circular chemistry [1].
In this context, a small library of SFAEs were prepared by the lipase-catalyzed esterification of isomeric mixtures of alkyl glycosides (namely α-/β-d-glucosides and α-/β-d-galactosides) with molten fatty acids (lauric, palmitic and stearic acid), using CalB (Novozym® 435) as biocatalyst in an easily scalable solvent-free system. Conversion of glucose and galactose into alkyl glycosides before the esterification reaction played a key role in circumventing the striking different solubility of the two reagents. The physico-chemical properties of the synthesized tensides (interfacial tension features, W/O emulsification capability and W/O stability over time) were then finely investigated [2].
References
[1] a) I.J.A. Baker et al., J. Surfactant Deterg. 3 (2000) 1-11; b) H.M. El-Laithy et al., Eur. J. Pharm. Biopharm. 77 (2011) 43-55; c) N.S. Neta et al., Crit. Rev. Food Sci. Nutr. 55 (2015) 595-610.
[2] a) S. Sangiorgio et al., Colloids Interface Sci. Commun. 48 (2022) 100630; b) R. Semproli et al., ChemPlusChem 88 (2023) e202200331
A two-step enzymatic approach to cheese whey valorization: Synthesis of alkyl galactoside fatty acid esters as non-ionic biosurfactants
No full textCheese whey is the main wastestream of dairy industry. After protein recovery, the resulting whey permeate
contains a pool of carbohydrates (lactose as well as its hydrolysis products, i.e. glucose and galactose) that
can be exploited as feedstock for the synthesis of Sugar Fatty Acid Esters (SFAE), non-ionic surfactants
characterized by emulsifying, stabilizing, and detergency properties.1
In this work,2 an immobilization study of β-galactosidase from Aspergillus oryzae (GalAo) was carried out with
the aim to develop a robust biocatalyst for lactose upcycling. Several types of binding chemistry, chemical
activation of the support, and immobilization conditions were assayed. Glyoxyl-Sepabeads EC-EP resulted in
good immobilization yields (immobilized protein=65% and immobilized activity=58%) and moderate activity
recovery (20%). The immobilized GalAo was used for the synthesis of a library of alkyl-β-D-galactosides by
reacting lactose with naturally occurring alcohols 2a-2g through a transglycosylation reaction; compounds
(3a-3g) were isolated in moderate to good yields (20-45%) (Scheme 1A). n-Butyl β-D-galactopyranoside (3d)
was submitted to the esterification step with palmitic acid in a solvent-free system by using Novozym 435 as
the biocatalyst,3 affording 6-O-palmitoyl-1-O-butyl galactopyranoside (4d) (Scheme 1B).
Scheme 1. A) Transglycosylation of lactose (1) with natural aliphatic alcohols (2a-g) catalyzed by immobilized GalAo in buffer pH
4.3/alcohol/(acetone), r.t., 6 h. B) Esterification of 3d with palmitic acid catalyzed by Novozym 435 in a solvent-free system, 80 °C, 8
h, molecular sieves. n.o.=not optimized.
Interfacial features and W/O emulsifying properties of 4d together with W/O emulsion stability over time
were evaluated.
Acknowledgements
This work was financially supported by Cariplo Foundation (Italy) (call: “Circular Economy for a sustainable future 2020”,
project BioSurf, ID 2020-1094).
References
1. Ortiz, M.S.; Alvarado, J.G.; Zambrano, F.; Marquez, R. J. Surfact. Deter. 2022, 25, 147-183.
2. Semproli, R. et al., manuscript in preparation
3. Sangiorgio, S.; Pargoletti, E.; Rabuffetti, M.; Robescu, M.S.; Semproli, R.; Ubiali, D.; Cappelletti, G.;
Speranza, G. Colloids Interface Sci. Commun. 2022, 48 100630
Synthesis and molecular modeling of purine ribonucleotides as potential ligands of the human G protein-coupled receptor 17 (GPR17)
No full textGPCRs (G Protein-Coupled Receptors) are important drug targets in medicinal chemistry [1]. The GPR17 receptor, phylogenetically related to both purinergic P2Y and CysLT receptors, is usually over-expressed in the damaged brain tissue and is involved in various disorders characterized by demyelination, such as multiple sclerosis and stroke. Experimental data have shown that it is responsive to both agonists (e.g. nucleotides and their adducts) and antagonists (e.g. Cangrelor and Montelukast) [2]. Therefore, the human GPR17 receptor is a promising therapeutic target for treatment of neurodegenerative diseases [3].
This evidence prompted us to perform docking studies aided by molecular modeling on a homology model (based on P2Y1 receptors). Among the selected molecules, 8-methylaminoinosinic acid (1) and three N2-alkyl/acyl derivatives of guanylic acid (2-4) emerged as the best potential ligands.
As a result, their synthesis was carried out. Compound 1 was obtained by direct phosphorylation of 8-methylaminoinosine, previously prepared by amination of 8-bromoinosine. In the case of 2, position N2 of the purine ring was activated as a bromo derivative and subjected to displacement with n-octylamine. As for 3 and 4, N2-acylations were performed by treatment with a proper acyl chloride or anhydride through a transient protection strategy. Compounds 2, 3 and 4 were obtained as 2’,3’-O-isopropylidene adducts of the corresponding nucleotides.
Binding assays will be carried out by Surface Plasmon Resonance (SPR) [4], which has been demonstrated as a reliable technique for the systematic identification of agonists and antagonists of GPCRs, including GPR17 as recently demonstrated by our group [5].
[1] D. Wacker, R. C. Stevens, B. L. Roth, Cell 2017, 170, 414-427.
[2] P. Ciana, M. Fumagalli, M.L. Trincavelli, C. Verderio, P. Rosa, D. Lecca, S. Ferrario, C. Parravicini, V. Capra, P. Gelosa, U. Guerrini, S. Belcredito, M. Cimino, L. Sironi, E. Tremoli, G.E. Rovati, C. Martini and M.P. Abbracchio, EMBO J 2006, 25, 4615-4627.
[3] G. Marucci, D. Dal Ben, C. Lambertucci, A. Marti Navia, A. Spinaci, R. Volpini and M. Buccioni, Expert Opin. Ther. Pat. 2019, 29, 85-95.
[4] D.-S. Wang, S.-K. Fan, Sensors 2016, 16, 1175-1192.
[5] D. Capelli, C. Parravicini, G. Pochetti, R. Montanari, C. Temporini, M. Rabuffetti, M. L. Trincavelli, S. Daniele, M. Fumagalli, S. Saporiti, E. Bonfanti, M. P. Abbracchio, I. Eberini, S. Ceruti, E. Calleri, S. Capaldi, Front. Chem. 2020, 7, 910
Influence of rainfall and soil properties spatial aggregation on extreme flash flood response modelling: an evaluation based on the Sesia river basin, North Western Italy
No full textHigh resolution radar rainfall fields and a distributed hydrologic model are used to evaluate the sensitivity of flood and flash flood simulations to spatial aggregation of rainfall and soil properties at catchment scales ranging from 75 to 983 km2. Hydrologic modeling is based on a Hortonian infiltration model and a network-based representation of hillslope and channel flow. The investigation focuses on three extreme flood and flash flood events occurred on the Sesia river basin, North Western Italy, which are analysed by using four aggregation lengths ranging from 1 to 16 km. The influence of rainfall spatial aggregation is examined by using the flow distance as a spatial coordinate, hence emphasising the role of river network in the averaging of space–time rainfall. The effects of reduced and distorted rainfall spatial variability on peak discharge have been found particularly severe for the flash flood events, with peak errors up to 35% for rainfall aggregation of 16 km and at 983 km2 catchment size. Effects are particularly remarkable when
significant structured rainfall variability combines with relatively important infiltration volumes due to dry initial conditions, as this emphasises the non-linear character of the rainfall–runoff relationship. In general, these results confirm that the correct estimate of rainfall volume is not enough for the accurate
reproduction of flash flood events characterised by large and structured rainfall spatial variability, even at catchment scales around 250 km2. However, accurate rainfall volume estimation may suffice for less spatially variable flood events. Increasing the soil properties aggregation length exerts similar effects on peak discharge errors as increasing the rainfall aggregation length, for the cases considered here and after rescaling to preserve the rainfall volume. Moreover, peak discharge errors are roughly proportional to runoff volume errors, which indicates that the shape of the flood wave is influenced in a limited way
by modifying the detail of the soil property spatial representation. Conversely, rainfall aggregation may exert a pronounced influence on the discharge peak by reshaping the spatial organisation of the runoff volumes and without a comparable impact on the runoff volumes
Identification of type 1 5alpha-reductase in myelin membranes of male and female rat brain
No full textThe formation of the 5alpha-reduced metabolites of testosterone (T) and of progesterone (P) is a very active process in the brain, since the enzyme 5alpha-reductase (5alpha-R) is present in almost any central nervous system (CNS) structure. A particularly elevated 5alpha-R activity has been shown in myelin sheaths. Two isoforms of the enzyme have been cloned, with different localisation as well as different biochemical properties. The present study was performed to determine whether both isoforms of the 5alpha-R, or only one of them, are/is responsible for the enzymatic activity observed in myelin. Kinetic analyses have been performed on purified myelin membranes prepared from the male or female rat brain, using both T and P as substrates. The 5alpha-R present appears to possess a pH optimum at basic values. The Vmax values obtained in the Lineweaver-Burk analysis were comparable in male and female preparations independently on whether T or P were used as the substrates, suggesting that a single enzymatic form is present in all samples examined; the Km obtained using [14C]T (Km: male 1.14 microM; female 1.46 microM) or [14C]P (Km: male 0.5 microM; female 0.64 microM) as substrates, were in good agreement with those obtained for the recombinant type 1 isoform. These data suggest that the type 1 isoform is the most relevant 5alpha-R present in myelin. To confirm this, a new polyclonal antibody was raised against the type 1 5alpha-R enzymatic protein, and used in immunohistochemical studies. The experiments were performed on the optic nerve, a myelinated structure very rich in 5alpha-R activity and the results clearly indicated the presence of a specific type 1 enzyme immunoreactivity in the myelin sheaths of axons
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Stereoselective monoreduction of bulky 1,2-dicarbonyls catalyzed by a benzil reductase from Pichia glucozyma (KRED1-Pglu)
No full textEnantiomerically enriched hydroxyketones are well-established intermediates for the synthesis of several bioactive compounds [1] and can be chemically obtained by stereoselective reduction of one of the carbonyl moieties of the corresponding diketones. However, enzymatic strategies are characterized by higher catalytic efficiency, milder reaction conditions, higher stereo- and regioselectivity, and fewer numbers of synthetic steps. Therefore, they can be chosen as convenient and environmentally friendly alternatives.[2]
A NADPH-dependent benzil reductase from the non-conventional yeast Pichia glucozyma (KRED1-Pglu) was over-expressed in E. coli, purified and exploited to catalyze the asymmetric monoreduction of bulky aromatic 1,2-dicarbonyl compounds. The cofactor was recycled by an enzyme-coupled system (glucose-glucose dehydrogenase (GDH) from Bacillus megaterium). The recombinant KRED1-Pglu showed a wide range of activity (24-97% conversion) and excellent stereoselectivity (ee ≥ 96% in all but one case). On the contrary, it proved either inactive or very poorly active towards most 1,3- and 1,4-dicarbonyls tested as potential substrates. In order to understand this peculiar behavior, the enzyme was crystallized (1.77 Å resolution) and its active site was investigated to identify the recognition residues involved in the desymmetrization reaction. QM and classical calculations also allowed for a proposal of the catalytic mechanism, along with an in silico reactivity prediction.[3]
[1] G. Aullón, P. Romea, F. Urpí, Synthesis 2017, 49, 484.
[2] P. Hoyos, J.-V. Sinisterra, F. Molinari, A. R. Alántara, P. Domínguez de María, Acc. Chem. Res. 2010, 43, 288.
[3] M. Rabuffetti, P. Cannazza, M. L. Contente, A. Pinto, D. Romano, P. Hoyos, A. R. Alcántara, I. Eberini, T. Laurenzi, L. Gourlay, F. Di Pisa, F. Molinari, Bioorg. Chem. 2021, 108, 104644
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