| 1. |
- Berglund, Per, et al.
(författare)
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Strategies for altering enzyme reaction specificity for applied biocatalysis
- 2005
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Ingår i: Current organic chemistry. - : Bentham Science Publishers Ltd.. - 1385-2728 .- 1875-5348. ; 9:4, s. 325-336
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Tidskriftsartikel (refereegranskat)abstract
- The fact that many enzymes have broad substrate specificity has been a property, of fundamental importance for the widespread applications of enzymes in synthetic chemistry. Many enzymes can, in addition, catalyze completely different reactions compared to their natural ones. The possibility of using molecular biology techniques to control Such catalytic plasticity of enzymes in order to establish completely new reaction specificity in the active site is the topic for this review. The examples are subdivided according to six different approaches used (i - vi) for engineering of the reaction specificity. The first approach (i) is the random method of directed evolution to achieve new reaction specificity. Other approaches involve strategies where tire reaction specificity of a known enzyme is implemented into another, closely related, enzyme by substituting key amino acid residues selected either by (ii) sequence or (iii) structural overlap of the two enzymes. Yet other approaches involve substitution of key amino acid residues to introduce new reaction specificity without comparing with a template enzyme (iv) and the introduction of a complete catalytic machinery (v). The final approach is the introduction of an active site into a non-catalytic protein (vi). These six different approaches for altering the reaction chemistry of enzymes each represent a powerful tool for controlling the catalytic plasticity or enzymes. The prospect for these altered enzymes as catalysts in synthetic chemistry is very large although examples of practical use are rare and still challenging. The progress in the area of altering enzyme reaction specificity will result in a Continued development towards the goal of creating tailor-made enzymes for synthetic chemistry.
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| 2. |
- Bernardo-Garcia, Noelia, et al.
(författare)
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Structural Bioinformatics in Broad-Spectrum Racemases : a new path in anti-microbial research
- 2016
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Ingår i: Current organic chemistry. - : Bentham Science. - 1385-2728 .- 1875-5348. ; 20:11, s. 1222-1231
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Tidskriftsartikel (refereegranskat)abstract
- D-amino acids are essential components of the bacterial cell wall and play notable roles in microbiology as regulators, for example in sporulation, biofilm formation or interspecies communication. Racemases are the specific enzymes catalyzing the interconversion of L-amino acids to D-amino acids. While most of racemases are mono-specific, a family of broad-spectrum racemases that can racemize ten of the 19 natural chiral amino acids has been recently reported. These enzymes can interconvert radically different residues such as aliphatic and positively charged residues producing non-canonical D-amino acids. Crystal structures together with bioinformatics allowed identification of the residues defining the molecular footprint in broad-spectrum racemases, the specific features of their active sites and the structural basis of their promiscuity. Here we review the recent knowledge on this family compared with the well established of alanine racemases. This structural information is a prerequisite for the development of novel drugs against the important human pathogens for which broad-spectrum racemases play a key role.
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| 3. |
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| 4. |
- Cetecioglu, Zeynep, et al.
(författare)
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Acute and Chronic Effects of Antibiotics on Deterioration of Anaerobic Substrate Utilization
- 2017
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Ingår i: Current organic chemistry. - : Bentham Science Publishers B.V.. - 1385-2728 .- 1875-5348. ; 21:12, s. 1044-1053
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Forskningsöversikt (refereegranskat)abstract
- The paper essentially summarizes and provides a comprehensive evaluation of degeneration of substrate utilization in terms of short and long term effects and biodegradability of the selected antibiotics; sulfamethoxazole, erythromycin, and tetracycline; under different conditions. This review focuses on acute and chronic tests to evaluate the inhibitory effects of the antibiotics and to control them at the source. Acute impact based on batch tests was conducted using antibiotic dozing in the range of 1-1000 mg/L. Substrate removal was monitored by means of soluble COD and VFA measurements. At low antibiotic dosing VFA mixture was completely removed; at higher doses propionate utilization was impaired and butyrate was reduced. Higher doses induced total inactivation of microbial metabolism. For chronic impacts, the antibiotic dozing was gradually increased in lab-scale anaerobic reactors. COD, VFA, and methane generation were monitored during each phase. For each antibiotic, a threshold concentration level was determined, which did not impair substrate utilization. High concentration of antibiotics (3 mg/L<) caused toxic effects on the mixed microbial culture and affected substrate removal and biogas generation and finalized a total collapse of the reactors. Each antibiotic reflected a different impact and biodegradation pattern related to its specific mode of action. Complete removal of antibiotics could be achieved at low concentration levels. The main removal mechanism for all three antibiotics was biodegradation and not sorption. When the sorption increased in the system, the system collapsed.
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| 5. |
- Grivas, Spiros
(författare)
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2,1,3-benzoselenadiazoles as valuable synthetic intermediates
- 2000
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Ingår i: Current organic chemistry. - : Bentham Science Publishers Ltd.. - 1385-2728 .- 1875-5348. ; 4:7, s. 707-726
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Tidskriftsartikel (refereegranskat)abstract
- N-alkyl-1,2-benzenediamines, 4-substituted-3-nitro-1,2-benzenediamines and 3,4-diamino-2-nitrophenols are readily obtained by deselenation of alkyl quaternary salts of 2,1,3-benzoselenadiazoles (bsd) and 5-substituted-4-nitro-bsd. The latter are easily obtained by nitration of 5-X-bsd (X = Me, Br, Cl, F, OMe, NHMe). Nitration of 5-fluoro-bsd yields the 4-nitro derivatives that are accompanied by substantial amounts of the corresponding 4-nitro-bsd-5-ols. ipso-Nitration of 5-fluoro-4-methyl-bsd is followed by instantaneous hydrolysis to (+/-)-4-methyl-4-nitro-bsd-5(4H)-one. Batcho-Leimgruber indole synthesis on 5-methyl-4-nitro-bsd followed by reductive deselenation of 1,2,5-selenadiazolo[3,4-g]indole affords 6,7-diaminoindole. Cyclocondensation of 3-nitro-1,2-benzenediamines with acetylacetone provides a convenient route for the preparation of 2-methyl-4-nitrobenzimidazoles. Less-accessible 6-halo-5-nitro- and 6-methoxy-5-nitroquinoxalines are efficiently synthesized by regioselective condensation of alpha-dicarbonyls with 4-halo- and 4-methoxy-3-nitro-1,2-benzenediamines. The reactive halogen atom or methoxyl group ortho to the nitro substituent renders these quinoxalines versatile intermediates to further heterocycles. The Se-77, C-13 and H-1 NMR chemical shifts of sixteen bsd derivatives, and the C-13 NMR chemical shifts of eight derivatives of 2-methylquinoxalines are presented.
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| 6. |
- Li, S., et al.
(författare)
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High-performance Sn/carbon composite anodes derived from Sn(II) acetate/polyacrylonitrile precursors by electrospinning technology
- 2013
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Ingår i: Current organic chemistry. - : Bentham Science Publishers Ltd.. - 1385-2728 .- 1875-5348. ; 17:13, s. 1448-1454
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Tidskriftsartikel (refereegranskat)abstract
- Sn/carbon composite nanofibers with various compositions were prepared from Sn(II) acetate/polyacrylonitrile (PAN) precursors by a combination of electrospinning and carbonization methods, and their potential use as anode materials for rechargeable lithiumion batteries was investigated. The composite electrode derived from 20 wt% Sn(II) acetate/PAN precursor showed excellent electrochemical properties, including a large reversible capacity of 699 mAh g-1 and a high capacity retention of 83% in 50 cycles. Sn/carbon composite nanofibers exhibited enhanced electrochemical performance ascribing to the combination of the properties of both Sn nanoparticles (large Li storage capability) and carbon matrices (long cycle life), and therefore could be potentially used in high-energy rechargeable lithium-ion batteries.
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| 7. |
- Ostrovskis, Pavels, et al.
(författare)
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Application of Metal Free Click Chemistry in Biological Studies
- 2013
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Ingår i: Current organic chemistry. - : Bentham Science Publishers Ltd.. - 1385-2728 .- 1875-5348. ; 17:6, s. 610-640
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Tidskriftsartikel (refereegranskat)abstract
- The first reported click reaction, copper(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition had limited biocompatibility due to the high toxicity of copper. Since alternative bioorthogonal click reactions have been developed, they have strongly influenced the field of chemical biology. Here are summarized three main metal-free click methodologies based on cycloaddition, Staudinger and thio-ene reactions. This review contains the basic principles, some mechanistic considerations and a collection of reagents that can be used in each method. Firstly, Diels-Alder and strain promoted inverse electron demand Diels-Alder cycloadditions are outlined together with triazole and isoxazole formation by 1,3-dipolar cycloadditions. Secondly, Staudinger-Bertozzi ligation, a chemoselective reaction of azides and engineered triarylphosphines, is discussed. Finally, thio-click chemistries including thiol-ene, thiol-yne, thio-Michael and fluoro-thio-click reactions are reviewed. Among the most important bioapplications of these click methodologies is the labeling of glycans, proteins, lipids and DNA. Additionally, synthetic methods and surface immobilization of biomolecules and biologically useful polymeric materials are also reviewed.
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| 8. |
- Pilarski, Lukasz T., et al.
(författare)
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Palladium Pincer Complex Catalyzed Funtionalization of Electrophiles
- 2011
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Ingår i: Current organic chemistry. - : Bentham Science Publishers Ltd.. - 1385-2728 .- 1875-5348. ; 15:18, s. 3389-3414
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Tidskriftsartikel (refereegranskat)abstract
- This review describes the usefulness of palladium pincer complexes in catalytic transformations of various electrophiles. We discuss two basic approaches to the functionalization of electrophiles: (i) palladium pincer complex catalyzed additions of allylic and other substrates to electrophiles, such as sulfonyl imines, aldehydes and related reagents; and (ii) pincer complex catalyzed generation of allylmetal reagents (such as boronates and other species) followed by a direct or palladium-catalyzed functionalization of the electrophiles under one-pot conditions. The study is focused on the reactivity and selectivity aspects of pincer complex catalysis. We show, for example, that allylations of imines and aldehydes are easier to perform with pincer complexes bearing pi-acceptor phosphine ligands, while generation of organometallic species can be efficiently achieved by sigma-donor, selenium or nitrogen containing pincer ligands. We present several examples of chiral pincer complexes in asymmetric catalysis. The high stability and well-defined stoichiometry of pincer-complexes allow a rational design of asymmetric catalytic reactions for carbon-carbon and carbon-heteroatom bond formations. Briefly, we have also reviewed the new emerging field of pincer complexes in Pd(II)/Pd(IV)-based catalytic cycles. These processes allow redox reactions involving pincer complex catalysts without altering of the typical pincer complex topology.
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| 9. |
- Rybakiewicz, Renata, et al.
(författare)
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Dithienopyrrole-based Organic Electroactive Materials and Their Photovoltaic Aspects
- 2020
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Ingår i: Current organic chemistry. - : BENTHAM SCIENCE PUBL LTD. - 1385-2728 .- 1875-5348. ; 24:23, s. 2695-2736
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Forskningsöversikt (refereegranskat)abstract
- 4H-dithieno[3,2-b:2,3-d]pyrrole has recently become a useful building block in the synthesis of donor-acceptor molecules with practical application in various organic technologies. The DTP molecule itself consists of a pyrrole ring with two fused thiophenes providing an alternative for the related dithieno[3,2-b:2,3-d]thiophene. Most notably, the significance of DTP-based low- and high-molecular weight species has increased in recent years since, upon proper processing, they allow to improve the performance of many fields of organic electronics. This review is a trial of a brief report on recent advances in modern DTP chemistry with examples of their applications, mostly in the area of organic photovoltaics. The scope of this manuscript was to present the structure-property relationships that had been found together with the development of DTP-based materials.
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| 10. |
- Witt, A, et al.
(författare)
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Recent developments in the field of quinazoline chemistry
- 2003
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Ingår i: Current organic chemistry. - : Bentham Science Publishers Ltd.. - 1385-2728 .- 1875-5348. ; 7:7, s. 659-677
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Tidskriftsartikel (refereegranskat)abstract
- Recent developments in the chemistry of quinazolines and quinazolinones are discussed. The chemistry of quinazoline alkaloids is reviewed featuring chrysogine, luotonin A, tryptanthrin, febrifugine. and rutaecarpine.
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