Steroselective synthesis of imidazolidin-4-ones from α-amino amides of the antimalarial primaquine and substituted benzaldehydes

Imidazolidin-4-ones are commonly employed as skeletal modifications in bioactive oligopeptides, either as proline surrogates or for protection of the N-terminal amino acid against aminopeptidase-catalysed hydrolysis . We have been working on the synthesis of imidazolidin-4-ones of the antimalarial primaquine , through acylation of primaquine with an α-amino acid and subsequent reaction of the resulting α-aminoamide with a ketone or aldehyde. Thus, when using racemic primaquine, an optically pure chiral α-amino acid and an aldehyde as starting materials, four imidazolidin-4-one diastereomers are to be expected (Scheme 1). However, we have recently observed that imidazolidin-4-one synthesis was stereoselective when 2-carboxybenzaldehyde (2CBA)* was used, as only two diastereomers were produced2. Computational studies have shown that the imine formed prior to ring closure had, for structures derived from 2CBA, a quasi-cyclic rigid structure2. This rigid conformation is stabilized by an intramolecular hydrogen bond involving the C=O oxygen atom of the 2-carboxyl substituent in 2CBA and the N-H group of the α-amino amide moiety2. These findings led us to postulate that the 2-carbonyl substituent in the benzaldehyde moiety was the key for the stereoselective synthesis of the imidazolidin-4-ones2

Unravelling the structure of chemisorbed CO2 species in mesoporous aminosilicas: a critical survey

Chemisorbent materials, based on porous aminosilicas, are among the most promising adsorbents for direct air capture applications, one of the key technologies to mitigate carbon emissions. Herein, a critical survey of all reported chemisorbed CO2 species, which may form in aminosilica surfaces, is performed by revisiting and providing new experimental proofs of assignment of the distinct CO2 species reported thus far in the literature, highlighting controversial assignments regarding the existence of chem- isorbed CO2 species still under debate. Models of carbamic acid, alkylammonium carbamate with different conformations and hydrogen bonding arrangements were ascertained using density functional theory (DFT) methods, mainly through the comparison of the experimental 13C and 15N NMR chemical shifts with those obtained computationally. CO2 models with variable number of amines and silanol groups were also evaluated to explain the effect of amine aggregation in CO2 speciation under confinement. In addition, other less commonly studied chemisorbed CO2 species (e.g., alkylammonium bicarbonate, ditethered carbamic acid and silylpropylcarbamate), largely due to the difficulty in obtaining spectroscopic identification for those, have also been investigated in great detail. The existence of either neutral or charged (alkylammonium siloxides) amine groups, prior to CO2 adsorption, is also addressed. This work extends the molecular-level understanding of chemisorbed CO2 species in amine-oxide hybrid surfaces showing the benefitof integrating spectroscopy and theoretical approaches.publishe

Catalytic reactions for H2 production on multimetallic surfaces: a review

Herewith, an overview is provided on the recent developments in the utilization of multimetallic catalysts to produce large amounts of molecular hydrogen, especially via the steam reforming of hydrocarbons and the water–gas shift reaction. Emphasis is given on the explanation of the problems affecting the currently used catalysts and how the addition/incorporation of other metals in available or new catalysts may lead to improved catalyst activity, selectivity and stability. We compare results from selected key examples taken from the literature where multimetallic catalysts are used for the aforementioned reactions. The methanol and ammonia decompositions are also critically analyzed, with focus on Earth-abundant metal elements.publishe

Core-shell nanocomposites prepared by hierarchical co-assembly: the role of the carbon shell in catalytic wet peroxide oxidation processes

The diffraction pattern of Fe3O4 (not shown) confirmed the presence of only one phase, corresponding to magnetite with a lattice parameter a = 8.357 Å and a crystallite size of 16.6 ± 0.2 nm. The diffraction pattern of MGNC (not shown) confirmed the presence of a graphitic phase, in addition to the metal phase, suggesting that Fe3O4 nanoparticles were successfully encapsulated within a graphitic structure during the synthesis of MGNC. The core-shell structure of MGNC is unequivocally demonstrated in the TEM micrograph shown in Fig. 1b. Characterization of the MGNC textural and surface chemical properties revealed: (i) stability up to 400 oC under oxidizing atmosphere; (ii) 27.3 wt.% of ashes (corresponding to the mass fraction of Fe3O4); (iii) a micro-mesoporous structure with a fairly well developed specific surface area (SBET = 330 m2 g-1); and (iv) neutral character (pHPZC = 7.1). In addition, the magnetic nature of MGNC (Fig. 2) is an additional advantage for possible implementation of in situ magnetic separation systems for catalyst recovery

Cellulose nanocrystals of variable sulfation degrees can sequester specific platelet lysate-derived biomolecules to modulate stem cell response

The surface chemistry of cellulose nanocrystals was engineered to show variable sulfation degrees, which was exploited to modulate platelet lysate-derived biomolecule sequestration and presentation. The protein coronas developed on CNC surfaces were characterized and it was demonstrated how they promote different signaling effects on human adipose-derived stem cell behavior.The research has received funding from PTDC/NAN-MAT/30595/2017, ERC Grant No. 772817; FCT/MCTES for PD/59/2013 - PD/BD/113807/2015, for ITI Research grant 1306_2018,ROTEIRO/0028/2013, and LISBOA-01-0145-FEDER-022125

Moisture effect on the separation of CO2/CH4 mixtures with amine-functionalised porous silicas

The effect of minor amounts of water on the CO2 and CH4 adsorption on primary and secondary amine-functionalised mesoporous silicas (APTES@SBA-15 and DEAPTES@SBA15, respectively) was studied with a combination of high-pressure gas adsorption, solid state NMR of labelled 13CO2 and density functional theory (DFT) calculations. Known amounts of water were pre-adsorbed on the materials (0.047 to 0.157 mmol∙g−1) and the adsorption performance for CO2 and CH4 was compared to the performance of the dry samples. We observed that even when only minor amounts of water are present, the tertiary amine-functionalised material revealed a significant enhancement of the selectivity for CO2 (from ca. 5.8 to 208) while the one with primary amine maintained the same adsorption properties. This is related to the change in the adsorption mechanism in DEAPTES@SBA15 when water is present since water participates in the reaction of the tertiary amine with CO2 to produce bicarbonate (confirmed by NMR and DFT results). Such species was not observed in APTES@SBA-15 with water. From a broader perspective, the results presented in this work are relevant to confirm the suitability of this type of hybrid adsorbents in industrial applications related with CO2 adsorption, where minor amounts of water may be present in the process streams, such as during bio, landfill, or natural gas upgrading, or also in carbon capture applications.publishe

Epitope-imprinted polymers: design principles of synthetic binding partners for natural biomacromolecules

Molecular imprinting (MI) has been explored as an increasingly viable tool for molecular recognition in various fields. However, imprinting of biologically relevant molecules like proteins is severely hampered by several problems. Inspired by natural antibodies, the use of epitopes as imprinting templates has been explored to circumvent those limitations, offering lower costs and greater versatility. Here, we review the latest innovations in this technology, as well as different applications where MI polymers (MIPs) have been used to target biomolecules of interest. We discuss the several steps in MI, from the choice of epitope and functional monomers to the different production methods and possible applications. We also critically explore how MIP performance can be assessed by various parameters. Last, we present perspectives on future breakthroughs and advances, offering insights into how MI techniques can be expanded to new fields such as tissue engineering.This work was supported by Project NORTE-01-0145-FEDER-000021 supported by the Norte Portugal Regional Operational Program (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF); by the European Union Framework Program for Research and Innovation HORIZON 2020, under the Twinning grant agreement no. 810850–Achilles, European Research Council grant agreement no. 772817; and by FCT/MCTES (Fundação para a Ciência e a Tecnologia/Ministério da Ciência, Tecnologia, e Ensino Superior) through PhD grant PD/BD/143039/2018 for S.P.B.T., financed through the Doctoral Program in Advanced Therapies for Health (PATH) (FSE/POCH/ PD/169/2013), project PTDC/NAN-MAT/30595/2017, and individual contract 2020.03410. CEECIND for R.M.A.D. N.A.P. acknowledges support from the Cockrell Family Chair Foundation; the Institute for Biomaterials, Drug Delivery, and Regenerative Medicine; and the UT-Portugal Collaborative Research Program

Sol-Gel Coating Membranes for Optical Fiber Sensors for Concrete Structures Monitoring

The use of advanced sensing devices for concrete and reinforced concrete structures (RCS) is considered a rational approach for the assessment of repair options and scheduling of inspection and maintenance strategies. The immediate benefits are cost reduction and a reliable prevention of unpredictable events. The use of optical fiber sensors (OFS) for such purposes has increased considerably in the last few years due to their intrinsic advantages. In most of the OFS, the chemical transducer consists of immobilized chemical reagents placed in the sensing region of the optical sensor by direct deposition or by encapsulation in a polymeric matrix. The choice of the support matrix impacts directly on the performance of the OFS. In the last two decades, the development of OFS functionalized with organic-inorganic hybrid (OIH) sol-gel membranes have been reported. Sol-gel route is considered a simple method that offers several advantages when compared to traditional synthesis processes, allowing to obtain versatile materials with unique chemical and physical properties, and is particularly valuable in the design of OIH materials. This review will provide an update of the current state-of-the-art of the OFS based on OIH sol-gel materials for concrete and RCS since 2016 until mid-2021. The main achievements in the synthesis of OIH membranes for deposition on OFS will be discussed. The challenges and future directions in this field will also be considered, as well as the main limitations of OFS for RCS monitoring. (c) 2021 by the authors. Licensee MDPI, Basel, Switzerland

Natural materials

The use of naturally occurring materials as scaffolds to support cell growth and proliferation significantly impacted the origin and progress of tissue engineering and regenerative medicine. However, the majority of these materials failed to provide adequate cues to guide cell differentiation toward the formation of new tissues. Over the past decade, a new generation of multifunctional and smart natural-based materials has been developed to provide biophysical and biochemical cues intended to specifically guide cell behavior. In this chapter, the use of extracellular matrix proteins and blood-derivatives intrinsic capacity to mimic the biophysical and biological characteristics of native tissues is reviewed. Furthermore, the design of a variety of nanostructures using the well-explored characteristics of nucleic acids is summarized. In the second section, the exploitation of supramolecular chemistry to create new dynamic functional hydrogels that mimic the extracellular matrix structure and/or composition is surveyed. Then, the incorporation of nanoelements in polymeric networks for the design of smart nanocomposite materials with tailored functionalities to guide cell behavior is introduced. Finally, the future perspectives in the development of new biomaterials for tissue engineering and regenerative medicine are presented.Te authors acknowledge the fnancial support of the European Union Framework Programme for Research and Innovation Horizon 2020, under the TEAMING grant agreement No 739572 – Te Discoveries CTR, Marie Skłodowska-Curie grant agreement No 706996 and European Research Council grant agreement No 726178; FCT (Fundação para a Ciência e a Tecnologia) and the Fundo Social Europeu através do Programa Operacional do Capital Humano (FSE/POCH) in the framework of Ph.D. grants PD/BD/113807/2015 (BBM) and PD/BD/129403/2017 (SMB), Post-Doc grant SFRH/ BPD/112459/2015 (RMD) and project SmarTendon (PTDC/NAN-MAT/30595/2017); Project NORTE01-0145-FEDER-000021 supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (ERDF

Operations and control of unmanned underwater vehicles

Operations and control of unmanned underwater vehicle systems arediscussed in terms of systems and technologies, vehicles, operational deploymentsand concepts of operation. The notions underlying the specification of single vehicleoperations are contrasted to new concepts of operation to illustrate the challengesthey pose to control engineering. New research directions are discussed in thecontext of the theories and techniques from dynamic optimization and computerscience. The overall discussion is done in the context of the activities of theUnderwater Systems and Technology Laboratory from Porto University