Publications by authors named "Daniel Méndez-Sánchez"

10 Publications

  • Page 1 of 1

Evolutionary insights and brief review of Loxodes Ehrenberg, 1830 (Ciliophora, Karyorelictea, Loxodidae) with description of a new species from Mexico.

Eur J Protistol 2021 Dec 6;82:125856. Epub 2021 Dec 6.

Taller de Sistemática y Biogeografía, Facultad de Ciencias, Universidad Nacional Autónoma de México. Av. Universidad 3000, Circuito Exterior s/núm. Ciudad Universitaria, CP 04510, Coyoacán, Ciudad de México, Mexico.

Karyorelictids are a group of ciliates inhabiting marine and freshwater biotopes and possessing a non-dividing macronucleus. We describe a new freshwater species based on morphology and the 18S rRNA gene sequence data. Loxodes tziscaensis n. sp. can be easily distinguished from other Loxodes species by the arrangement of the nuclear apparatus and features of the buccal and somatic ciliature. The current proposed 18S rRNA phylogeny of Loxodes, including seven Loxodes species, shows two morphologically well-supported groups. Group A (L. rostrum, type species; L. vorax and L. tziscaensis n. sp.) includes species with a single nuclear group (two macronuclei and one micronucleus), in contrast to species of group B, which possess more than one nuclear group (L. striatus, L. magnus, L. kahli, L. penardi, and L. rex). We propose that the last common ancestor of Loxodes was a marine Remanella-like species possessing a single nuclear group. The division and differentiation of the micronucleus into a new macronucleus and the retention of the old macronuclei, independently of cell division, may have been two crucial processes during the evolution and diversification of Loxodes species with one nuclear group into species with multiple nuclear groups.
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http://dx.doi.org/10.1016/j.ejop.2021.125856DOI Listing
December 2021

Multienzyme One-Pot Cascades Incorporating Methyltransferases for the Strategic Diversification of Tetrahydroisoquinoline Alkaloids.

Angew Chem Int Ed Engl 2021 08 16;60(34):18673-18679. Epub 2021 Jul 16.

Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK.

The tetrahydroisoquinoline (THIQ) ring system is present in a large variety of structurally diverse natural products exhibiting a wide range of biological activities. Routes to mimic the biosynthetic pathways to such alkaloids, by building cascade reactions in vitro, represents a successful strategy and can offer better stereoselectivities than traditional synthetic methods. S-Adenosylmethionine (SAM)-dependent methyltransferases are crucial in the biosynthesis and diversification of THIQs; however, their application is often limited in vitro by the high cost of SAM and low substrate scope. In this study, we describe the use of methyltransferases in vitro in multi-enzyme cascades, including for the generation of SAM in situ. Up to seven enzymes were used for the regioselective diversification of natural and non-natural THIQs on an enzymatic preparative scale. Regioselectivites of the methyltransferases were dependent on the group at C-1 and presence of fluorine in the THIQs. An interesting dual activity was also discovered for the catechol methyltransferases used, which were found to be able to regioselectively methylate two different catechols in a single molecule.
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http://dx.doi.org/10.1002/anie.202104476DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8457072PMC
August 2021

Euplotes octocarinatus Carter, 1972 (Ciliophora, Spirotrichea, Euplotidae): Considerations on its morphology, phylogeny, and biogeography.

Eur J Protistol 2020 Jun 3;74:125667. Epub 2020 Jan 3.

Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China. Electronic address:

The cosmopolitan genus Euplotes Ehrenberg, 1830 comprises a highly distinguishable group of ciliates. However, details of the cell surface, the ciliature, and molecular data are still scarce for some species. We studied Euplotes octocarinatus Carter, 1972 from two Mexican freshwater bodies, providing data on its morphology, SSU rRNA gene sequence, and phylogeny. In addition, we obtained all data of previous records to show its geographic distribution and biogeographical pattern. The current populations showed some differences as compared with the original description and we provide an improved diagnosis. Morphologically, the species is very similar to Euplotes patella and E. daidaleos but differs by invariably having eight dorsolateral kineties (vs. nine in Euplotes patella and E. daidaleos), and lacking endosymbiotic green algae (vs. present in E. daidaleos). Phylogenetically, the Mexican population of E. octocarinatus nested with four isolates of the species lacking morphological characterization. The Euplotes octocarinatus described herein grouped into a fully-supported clade, which includes E. patella, E. amieti, E. daidaleos, E. eurystomus, E. woodruffi and E. aediculatus. Biogeographically, E. octocarinatus seems to have a wide distribution.
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http://dx.doi.org/10.1016/j.ejop.2019.125667DOI Listing
June 2020

Engineering transketolase to accept both unnatural donor and acceptor substrates and produce α-hydroxyketones.

FEBS J 2020 05 10;287(9):1758-1776. Epub 2019 Nov 10.

Department of Biochemical Engineering, University College London, UK.

A narrow substrate range is a major limitation in exploiting enzymes more widely as catalysts in synthetic organic chemistry. For enzymes using two substrates, the simultaneous optimisation of both substrate specificities is also required for the rapid expansion of accepted substrates. Transketolase (TK) catalyses the reversible transfer of a C -ketol unit from a donor substrate to an aldehyde acceptor and suffers the limitation of narrow substrate scope for industrial applications. Herein, TK from Escherichia coli was engineered to accept both pyruvate, as a novel donor substrate, and unnatural acceptor aldehydes, including propanal, pentanal, hexanal and 3-formylbenzoic acid (FBA). Twenty single-mutant variants were first designed and characterised experimentally. Beneficial mutations were then recombined to construct a small library. Screening of this library identified the best variant with a 9.2-fold improvement in the yield towards pyruvate and propionaldehyde, relative to wild-type (WT). Pentanal and hexanal were used as acceptors to determine stereoselectivities of the reactions, which were found to be higher than 98% enantiomeric excess (ee) for the S configuration. Three variants were identified to be active for the reaction between pyruvate and 3-FBA. The best variant was able to convert 47% of substrate into product within 24 h, whereas no conversion was observed for WT. Docking experiments suggested a cooperation between the mutations responsible for donor and acceptor recognition, which would promote the activity towards both the acceptor and donor. The variants obtained have the potential to be used for developing catalytic pathways to a diverse range of high-value products.
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http://dx.doi.org/10.1111/febs.15108DOI Listing
May 2020

Design and Use of de novo Cascades for the Biosynthesis of New Benzylisoquinoline Alkaloids.

Angew Chem Int Ed Engl 2019 07 18;58(30):10120-10125. Epub 2019 Jun 18.

Department of Chemistry, University College London, 20 Gordon Street, London, WC1H 0AJ, UK.

The benzylisoquinoline alkaloids (BIAs) are an important group of secondary metabolites from higher plants and have been reported to show significant biological activities. The production of BIAs through synthetic biology approaches provides a higher-yielding strategy than traditional synthetic methods or isolation from plant material. However, the reconstruction of BIA pathways in microorganisms by combining heterologous enzymes can also give access to BIAs through cascade reactions. Most importantly, non-natural BIAs can be generated through such artificial pathways. In the current study, we describe the use of tyrosinases and decarboxylases and combine these with a transaminase enzyme and norcoclaurine synthase for the efficient synthesis of several BIAs, including six non-natural alkaloids, in cascades from l-tyrosine and analogues.
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http://dx.doi.org/10.1002/anie.201902761DOI Listing
July 2019

Biomimetic Phosphate-Catalyzed Pictet-Spengler Reaction for the Synthesis of 1,1'-Disubstituted and Spiro-Tetrahydroisoquinoline Alkaloids.

J Org Chem 2019 06 31;84(12):7702-7710. Epub 2019 May 31.

Department of Chemistry , University College London , Christopher Ingold Building, 20 Gordon Street , London WC1H 0AJ , U.K.

Tetrahydroisoquinoline (THIQ) alkaloids are an important group of compounds that exhibit a range of bioactivities. Here, a phosphate buffer-catalyzed Pictet-Spengler reaction (PSR) using unreactive ketone substrates is described. A variety of 1,1'-disubstituted and spiro-tetrahydroisoquinoline alkaloids were readily prepared in one-step and high yields, highlighting the general applicability of this approach. This study features the role of phosphate in the aqueous-based PSR and provides an atom-efficient, sustainable route to new THIQs.
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http://dx.doi.org/10.1021/acs.joc.9b00527DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7007230PMC
June 2019

A New Subspecies of Oxytricha granulifera (Hypotrichia: Oxytrichidae) from Mexico, with Notes on its Morphogenesis and Phylogenetic Position.

J Eukaryot Microbiol 2018 05 10;65(3):357-371. Epub 2017 Nov 10.

Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao, 266003, China.

The genus Oxytricha Bory de Saint-Vincent in Lamouroux, Bory de Saint-Vincent and Deslongchamps, 1824 comprises about 38 species distributed worldwide and has been considered to be a nonmonophyletic group. Based on living observations, protargol preparations, and a small subunit ribosomal RNA (SSU rRNA) gene sequence, we describe a new subspecies Oxytricha granulifera chiapasensis n. subsp. This new taxon is morphologically characterized by undulating membranes basically in a Stylonychia-pattern, six dorsal kineties, size in vivo ca. 60-120 × 20-40 μm, 21-30 right and 21-31 left marginal cirri, 22-29 adoral membranelles, and spherical cortical granules arranged in longitudinal rows on the dorsal side. In terms of the SSU rRNA gene sequence, the new subspecies differs from populations of O. granulifera from GENBANK by 7-35 nucleotides. Phylogenetic analyses showed that Oxytricha granulifera gene sequences were nested into three groups, with the new subspecies included in one of them. Oxytricha granulifera chiapasensis n. subsp. is different from Oxytricha granulifera granulifera Foissner and Adam, 1983 and Oxytricha granulifera quadricirrata Blatterer and Foissner, 1988 based on: (i) undulating membranes in Stylonychia-pattern, (ii) formation of a sixth dorsal kinety during morphogenesis, (iii) the adoral membranelles number, and (iv) inhabiting freshwater habitats.
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http://dx.doi.org/10.1111/jeu.12479DOI Listing
May 2018

Novel chemoenzymatic oxidation of amines into oximes based on hydrolase-catalysed peracid formation.

Org Biomol Chem 2017 Apr;15(15):3196-3201

Departamento de Química Orgánica e Inorgánica, Instituto Universitario de Biotecnología de Asturias, Universidad de Oviedo, 33006 Oviedo, Spain.

The efficient transformation of benzylamines into the corresponding oximes has been described by means of a chemoenzymatic process. This strategy is based on a two-step sequence developed in one-pot at 30 °C and atmospheric pressure. First, the formation of a reactive peracid intermediate occurs by means of a lipase-catalysed perhydrolysis reaction, and then this peracid acts as a chemical oxidising agent of the amines. A total of nine ketoximes were isolated in high purity after a simple extraction protocol (90-98% isolated yield), while for the eleven synthesised aldoximes a further column chromatography purification was required (71-82% isolated yield). In all cases excellent selectivities were attained, offering a practical method for amine oxidation in short reaction times (1 hour). The environmental impact of the process was analysed and compared with a recently published alternative chemical synthesis, finding for this metric a good E-factor value.
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http://dx.doi.org/10.1039/c7ob00374aDOI Listing
April 2017

Determination of volatile compounds in cider apple juices using a covalently bonded ionic liquid coating as the stationary phase in gas chromatography.

Anal Bioanal Chem 2017 Apr 1;409(11):3033-3041. Epub 2017 Mar 1.

Department of Physical and Analytical Chemistry, University of Oviedo, Avenida Julián Clavería 8, 33006, Oviedo, Spain.

A chromatographic method for the separation of volatile compounds in Asturian cider apple juices has been developed. For this separation purpose, a monocationic imidazolium-based ionic liquid bearing a reactive terminal iodine atom was synthesized by a quaternization-anion exchange chemical sequence. Next, the gas chromatography (GC) stationary phase was prepared by covalently linking the imidazolium monolith to the reactive silanol groups of the inner capillary wall at 70 °C. This coated GC column exhibited good thermal stability (290 °C), as well as good efficiency (2000 plates/m) in the separation of volatile compounds from Asturian apple cider juices, and was characterized using the Abraham solvation parameter model. The intra-day and inter-day precision of the chromatographic method was evaluated, obtaining relative standard deviations from 3.7 to 12.9% and from 7.4 to 18.0%, respectively. Furthermore, recoveries from 82.5 to 122% were achieved. Graphical Abstract Covalent bonding of an ionic liquid to inner column wall led to a great improvement of the separation efficiencies of stationary phases in gas chromatography.
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http://dx.doi.org/10.1007/s00216-017-0250-9DOI Listing
April 2017
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