Wyniki wyszukiwania - Biblioteka Nauki

1

Asymetryczna synteza a-aminokwasów

100%

Dąbrowska A. , Wiczk W. , Łankiewicz L.

Wiadomości Chemiczne

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1998

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tom [Z] 52, 1-2

1-42

EN

a-Amino acids are among the most important compounds in living organisms. Amino acids are not only constituents of peptides and proteins but they play an important role in many reactions in living cells. There are many excellent methods of the asymmetric synthesis of a-amino acids, but only some of them are versatile. In this work we have reviewed and presented the most versatile methods, giving the best chemical yield and optical purity of the final products. One of the oldest and still useful synthetic routes to racemic a-amino acids is Strecker's method [3], (Scheme 1). Modification of the methods by Weinges et al. [8-11] (Scheme 2) allowed to obtain pure enantiomers of a-amino acids in high yields. Next important group of the methods applies 'glycine anion equivalent'. In this group, 'bislactim-ether' method of Schöllkopf et al. [13-21], (Scheme 3 and Tab. 1] has to be mentioned at first because of the high chemical yield of the transformation and optical purity of the final amino acid. The same type of methodology was employed by Seebach et al., their method utilizing oxazolidinones or imidazolidinones [22-26] (Schemes 4, 5 and Tab.2). Yield and enantiomeric excess (ee) of the final amino acid in the method of Seebach et al., is very high (in most cases >80%). The only inconvenience is connected with drastic conditions of final hydrolysis. The similar, good results were also obtained in methods utilizing enolates obtained from oxazinones [29-31], (Schemes 6-8 and Tabs 3,4). Derivatives of the oxazinones were also applied as 'glycine cation equivalent' in the method in which 'the chiral cation' reacts with nucleophiles [32, 33], (Scheme 9 and Tab.5) with the high chemical yield and ee of the final product. The similar procedures were used in an alkylation of a chiral Schiff base. The best yields and optical purity of the final a-amino acid were obtained by Oppolzer et al. [35,36], who applied a derivative of glycine attached to bornane-10,2-sultam (the derivative of camphor), (Schemes 13,14). The next group of synthetic procedures is based on a reaction of a ring opening of b-lactones obtained from serine [41-43], (Scheme 16) or threonine [44], and aziridines [45-48], (Scheme 17). A nucleophile attack on the b-carbon of the substrate gives amino acid with modified side chain. Despite the high yield and ee selection of possible nucleophiles is limited. Another important methodology is called 'electrophilic amination'. In this procedure a chiral enolate obtained from N-acyl-oxazolidinone [50,52], (Scheme 18,19) or N-acyl-sultam [51, 53 ], (Scheme 21) is aminated either by di-tert-butyl-azodicarboxylate (DBAD), [50, 51], trisyl azide [52], or 1-chloro-1-nitrozo-cyclohexane [53]. Yield of these reactions are high and ee exceeds 95%. Contrary to the 'electrophilic', a 'nucleophilic amination' requires a 'cation equivalent' obtained from a chiral N-acyl-derivatives [54-55]. The reaction usually yields a desired product of good enantiomeric quality. In most cases azide anion is a source of 'nucleophilic amine equivalent' (Schemes 22 and 23). The chiral 2,3-epoxy-1-ols can be also applied in this methodology [57, 58], (Scheme 24). Asymmetric catalytic hydrogenation of a dehydro derivatives of amino acids and peptides is another valuable group of synthetic routes to the single enantiomer of the amino acid. There is a possiblity of heterogenous and homogenous catalysis involving insoluble catalysis [60, 61], (Schemes 25, 26) or soluble [62, 63], (Schemes 27, 28) in medium of the reaction. The best results (yield = 100% and ee>99%) were reprted for the complexes of Rh with chiral phosphines ligands like BINAP or DIPAMP (Scheme 28), [67]. The last method reported in our review is based on the usage of enzymes. The most widely used in this field are the following enzymes : acylases - catalyzing stereoselective removal or synthesis of N-acyl deerivatives [70], (Scheme 30) and proteases - catalyzing methods give in many cases both enantiomers at the same time.

2

Application of Oppolzer's Sultam in the Synthesis of Cyclic alfa-Amino Acids and beta-Amino Acids

100%

Woźniak D. , Szymańska A. , Ołdziej S. , Łankiewicz L. , Grzonka Z.

Polish Journal of Chemistry

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2006

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tom Vol. 80, nr 2

265-277

EN

In this paper we describe the application of Oppolzer's sultam as a chiral auxiliary for the synthesis of cyclic alfa- and beta2-amino acids. The key step of the synthesis is stereoselective alkylation of sultam-derived glycine and beta-alanine Schiff's bases leading to diastereometrically pure products. Final compounds are obtained after mild acidic and next basic hydrolyses of auxiliary groups and can be directly converted into N-tert-butoxycarbonyl- or N-fluorenylmethoxycarbonyl derivatives useful in peptide synthesis. In the case of substrates alkylated with dihalogenoalkanes spontaneous cyclization occurring during removal of the auxiliary groups yields cyclic alfa-amino acids (proline homologues) with reasonable yield and stereoselectivity. Theoretical data explain the differences in tendency for cyclization between alfa- and beta-amino acids.

3

Seasonal changes in the biochemical components of Pseudonereis anomala (Polychaeta, Nereididae) from the Alexandria coast, Egypt

100%

Dorgham M. M. , Hamdy R. , Al-Rashidy H. H. , Atta M. M.

Oceanologia

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2014

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tom No. 56 (4)

881--887

EN

The biochemical composition (carbohydrates, protein, lipids, fatty acids and amino acids) of the nereid polychaete Pseudonereis anomala Gravier 1901, from a shallow part of the Alexandria coast (Egypt), was studied seasonally. The results revealed that P. anomala had a lower water content, higher carbohydrates and protein, but approximately similar or higher lipid levels than several other polychaetes. Fatty acids appeared to be dominated by unsaturated acids, constituting seasonally 49.6-81%, while saturated acids reached high amounts in winter and spring (23.3 and 38.3% respectively). C20:5n-3 was the major polyunsaturated fatty acid, accompanied by small amounts of C18:4n-3, C20:4n-6, C16:1n-7 and C20:1n-9. C18:0 dominated the saturated fatty acids for most of the year, except in autumn when C16:0 was the major one.

4

Wydzielanie aminokwasów techniką wykorzystującą temperaturę zmętnienia

100%

Materna K.

Przemysł Chemiczny

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2006

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tom T. 85, nr 8-9

615-616

PL

Przedmiotem pracy było zbadanie możliwości wydzielania aminokwasów z roztworów wodnych metodą wykorzystującą zjawisko zmętnienia roztworów niejonowych związków powierzchniowo czynnych CPE (cloud-point extraction). Zastosowanymi surfaktantami były oksyetylenowane dodekaniany metylu o różnej hydrofilowości oraz oksyetylenowany nonylofenol. Jako modelowych aminokwasów użyto glicynę, DL-fenyloalaninę oraz L-4-hydroksyprolinę. Na podstawie uzyskanych wyników stwierdzono, że najskuteczniej separowanym aminokwasem była DL-fenyloalanina (60%), następnie glicyna (58%) i L-4-hydroksyprolina (52%). Spośród zastosowanych surfaktantów najbardziej odpowiednim okazał się oksyetylenowany dodekanian metylu o średnim stopniu oksyetylenowania równym 7. Najniższe wartości skuteczności wydzielania badanych aminokwasów uzyskano dla roztworów zawierających oksyetylenowany nonylofenol.

EN

Model amino acids, DL-phenylalanine, glycin, and L-4-hydroxyproline, were extd. from 1-7 mM solns., with 2.5% of a nonionic, oxyethylenated(n = 7 or 10)methyl dodecanoate or polyoxyethylene(9) nonylphenyl ether. The 0.004 M acids were sepd. (with centrifugation) in resp. 60, 58, and 52% into the water phase. The 10 and the 9 were the most and the least efficient surfactants, resp. The 7 was next best; it gave lower cloud ps. than did the 10. Cloud ps. were detd. in relation to surfactant concn., amino acid concn., and NaSCN and NaCl as salting-in and salting-out agent, resp. Optimum heating time was 4 hrs.

5

Structural factors influencing the reaction rates of 4-aryloxy-7-nitrobenzofurazans with amino acids

100%

Bem M. , Vasilescu M. , Caproiu M. , Draghici C. , Beteringhe A. , Constantinescu T. , Banciu M. , Balaban A.

Open Chemistry

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2004

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tom 2

|

nr 4

672-685

EN

An interesting observation was made when studying the SNAr reaction between several 4-aryloxy-7-nitrobenzofurazans (2) and several amino acids leading to the apparition of detectable fluorescence from the substitution products3. Acidic amino acids reacted very slowly=while basic amino acids react fastest with2 having an unsubstituted phenyl or a 4-formyl-phenyl Ar group. Amongst neutral amino acids, proline reacts fastest at room temperature after 100 min. With2 having a methoxy-subtituted Ar group.

6

Quantum Chemical Study on Chiral Recognition Modes Between Esters of alfa-Hydroxycarboxylic Acids and Amino Acids

100%

Hoffmann M.

Polish Journal of Chemistry

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2005

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tom Vol. 79 / nr 7

1179-1185

EN

Chiral recognition between methyl ester of (R)-lactic acid and (R)- or (S)-alanine has been studied by means of quantum chemistry. The interacting systems in vacuo have been studied up to B3LYP/6-311++G(3df,3pd)//B3LYP/6-31+G(d) and MP2/6-31+G(d) levels, while aqueous solution effects have been included via solvation model SM5.4 calculations. The obtained results shed new light on chiral recognition between homochiral and heterochiral alfa-hydroxy carboxylic acid esters and amino acids. Energy of binding by about 3 kJ/mol favors associations between homochiral (R + R) molecules of methyl ester of lactic acid and alanine then associations between heterochiral (R + S) molecules. In the heterochiral complex alaninie accommodates significantly larger deformation than in the homochiral association.

7

Oxidation of Phosphonocysteine and Phosphonohomocysteine. Synthesis of Phosphonocysteic and Phosphonohomocysteic Acids

100%

Kudzin Z. , Saganiak M. , Andrijewski G. , Drabowicz J.

Polish Journal of Chemistry

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2005

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tom Vol. 79 / nr 3

525-528

8

Coordination behaviour of biologically active Shiff bases of amino acids towards stannous ion

100%

Singh H. L. , Sharma M. , Gupta M. K. , Varshney A. K.

Bulletin of the Polish Academy of Sciences. Chemistry

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1999

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tom Vol. 47, No. 2

103-110

EN

Reaction of tin (II) methoxide with Schiff bases derived by condensation of 2-hydroxy-1-naphthaldehyde, salicylaldehyde with glycine, b-alanine, a-valine, a-iso-leucine and a-tryptophan in 1:1 molar ratio gives a new series of tin(II) complexes. The complexes are monomeric and of non-electrolytic nature. The coordination behaviour of Schiff bases through phenolic and acidic oxygens and azomethine nitrogen towards tin atom has been investigated by infrared and multinuclear magnetic resonance (1 H, 130 and 119Sn) spectral studies. Schiff bases and their tin complexes have also been screened for their antifungal and antibacterial activities as several fungi and bacteria are found quite active in this respect.

9

DEVELOPMENT OF HYDROGEL CAPSULES FOR USE IN DUAL-PHASE TOPICAL PREPARATIONS CONTAINING DIHYDROXYACETONE AND AMINO ACIDS – PRELIMINARY RESULTS

100%

Jacyna B. , Mikolaszek B. , Maciejewski B. , Cal K.

Acta Poloniae Pharmaceutica - Drug Research

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2019

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tom 76

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nr 4

715-724

EN

The aim of the following work was a preliminary assessment of the possibility of producing a topical preparation containing dihydroxyacetone (DHA) and amino acids, encapsulated separately in polysaccharide capsules. The colour reaction between the DHA and amino acids would be possible after mixing of the two components triggered with mechanical disruption of the capsules on application. Such preparation could be used in patients suffering from vitiligo, by masking the symptoms of the disease. Several capsule compositions were evaluated in terms of appearance, dimensions and mechanical parameters. In addition, the reactions of various amino acids with DHA were carried out and obtained colours were analysed. The results indicate that formation of the dual-phase formulation of encapsulated DHA and amino acids is possible. It was also found that certain amino acids vary in colour resulting from reaction with DHA. This feature can be potentially utilized to better design the colour resulting from application of the prepared composition.

10

Microcapillary Electrophoresis with Fluorescence Detection

100%

Lewandowska N. , Dybko A. , Chudy M. , Wcisło M. , Poboży E. , Brzózka Z.

Polish Journal of Chemistry

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2006

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tom Vol. 80, nr 11

1799-1806

EN

The advantages and application perspectives for microcapillary electrophoresis (mi CE) are presented. The microchip based on a glass plate was fabricated. The separations of three FITC-labeled amino acids carried out with the conventional CE system and in the microchip were compared. The obtained results proved the usability of the microchip for mi CE process.

11

Non-racemic mixture model: a computational approach

100%

Polanco C. , Buhse T.

Acta Biochimica Polonica

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2017

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tom 64

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nr 1

17-19

EN

The behavior of a slight chiral bias in favor of l-amino acids over d-amino acids was studied in an evolutionary mathematical model generating mixed chiral peptide hexamers. The simulations aimed to reproduce a very generalized prebiotic scenario involving a specified couple of amino acid enantiomers and a possible asymmetric amplification through autocatalytic peptide self-replication while forming small multimers of a defined length. Our simplified model allowed the observation of a small ascending but not conclusive tendency in the l-amino acid over the d-amino acid profile for the resulting mixed chiral hexamers in computer simulations of 100 peptide generations. This simulation was carried out by changing the chiral bias from 1% to 3%, in three stages of 15, 50 and 100 generations to observe any alteration that could mean a drastic change in behavior. So far, our simulations lead to the assumption that under the exposure of very slight non-racemic conditions, a significant bias between l- and d-amino acids, as present in our biosphere, was unlikely generated under prebiotic conditions if autocatalytic peptide self-replication was the main or the only driving force of chiral auto-amplification.

12

Biomass of freshwater Cladophora as a raw material for agriculture and the cosmetic industry

88%

Messyasz B. , Leska B. , Fabrowska J. , Pikosz M. , Roj E. , Cieslak A. , Schroeder G.

Open Chemistry

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2015

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tom 13

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nr 1

EN

This study was undertaken to determine mineral content, amino acid and fatty acid composition of the freshwater macroalga – Cladophora glomerata. The studies were based on the content comparison in algal biomass collected from a lake and cultured in a laboratory. To determine the ability of copper cumulating by macroalgae, Cladophora was cultured in the medium supplemented with Cu ions. This study indicated that the relative abundance of metals in filaments decreased in the following order: Ca > K > Mg > Na > Fe > Cu > Zn > Pb > As > Ni > Cd > Mn > Cr > Co. Total protein content ranged from 14.45% in Cladophora from a lake to 26.55% in Cladophora from a laboratory. The main amino acids analyzed were aspartic and glutamic acid. The fatty acid content in the dry matter of the extract varied depending on the extraction method used: ethylene alcohol (19.0%), acetone (34.5%) or supercritical fluid extraction (62.5%). Freshwater C. glomerata due to the macrominerals, trace elements, amino and fatty acids composition in the extracts can be a valuable resource for nutritional and cosmetic applications.

13

Artificial evolution. An algorithm for an exploration of the amino acid sequences space

88%

Błażewicz J. , Dziurdza B. , Markiewicz W. T.

Foundations of Computing and Decision Sciences

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2003

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tom Vol. 28, No. 4

195-209

EN

Artifical evolution methods are useful tools in designing of drugs and proteins with the desired properties. One of the applications is searching for new proteins which have the required features. Due to some disadvantages of known artificial evolution methods, such as phage display or SELEX, the new approach to artificial evolution experiment is being studied. The mathematical model for this approach is introduced and the interesting classes of efficient randomization patterns are defined The corresponding algorithm to find them is also presented. The model allows to plan an artificial evolution experiment and makes this new approach efficient. The introduced model has led to the new optimization problem: Efficient Randomization one, for which an exact algorithm is described.

14

The influence of selected amino acids on the dynamic properties of the liposome membranes : ESR study

88%

Man D. , Broda M. , Buczek A. , Kawecka A. , Siodłak D.

Nukleonika

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2013

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tom Vol. 58, No. 3

443--446

EN

In this work the changes in the fluidity of liposome membranes caused by alanine and butyrine derivatives (Ac-Ala-NMe2 and Ac-Abu-NMe2) were investigated. Liposomes were obtained in the process of egg yolk lecithin (EYL) sonication. The concentration of the admixture in the proportion to EYL varied from 0 to 25% mole. The electron spin resonance (ESR) spectroscopy was used with two different spins probes. Each spin probe penetrates different regions of liposome membrane. The TEMPO probe occurs both in the hydrophobic part of the membrane and in the water environment what allows to determine the spectroscopic parameter F of division of this probe into the membrane and its water surrounding. DOXYL is localized in the central part of the lipid bilayer and is used to obtain the spectroscopic parameter τ – rotation correlation time – whose value gives information about fluidity changes in the middle of the lipid bilayer. The study indicated that the tested as admixtures N-methylated model peptides significantly changed the fluidity of liposome membranes. The dynamic of this process depends both on amino acids derivative and on the membrane region. Both studied compounds increased the fluidity of the surface layer of liposome membrane. At the same time, butyrine derivative caused the stiffening of the middle part of liposome bilayer, but alanine derivative slightly increased the fluidity of this region.

15

Evaluation of thin-layer chromatography systems for analysis of amino acids in complex mixtures

88%

Vasta J. D. , Cicchi M. , Sherma J. , Fried B.

Acta Chromatographica

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2009

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tom Vol. 21, no. 1

29-38

EN

Different thin-layer chromatography (TLC) systems were evaluated for analysis of 21 biologically important essential and nonessential amino acids in complex mixtures such as biological tissues and fluids. Amino acids were visualized on the layers by derivatization with ninhydrin reagent, and R F values were determined by slit-scanning densitometry. The five systems found to be most useful for analysis of amino acids were cellulose and silica gel high-performance TLC (HPTLC) plates developed with either 2-butanol-pyridine-glacial acetic acid-deionized water, 39:34:10:26, or 2-butanol-pyridine-25% ammonia-deionized water, 39:34:10:26, and ion exchange TLC plates developed with citrate buffer, pH 3.3. Using these five systems with ninhydrin detection, identification of all amino acids except for leucine and isoleucine in complex mixtures is possible, and quantification can be achieved if the amino acid to be quantified is well separated from adjacent components of the mixture. Example chromatograms are illustrated for separation and identification of amino acids in a snail tissue sample on a cellulose HPTLC plate.

16

Studies on carotenoproteins in animals. X. Euphausia superba Dana 1852 (Crustacea, Euphausiacea)

88%

Czeczuga B. , Czeczuga B.

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1984

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tom 5

|

nr 1-2

17

Evaluation of Hyper-Tolerance of Aquatic Plants to Metal Nanoparticles

88%

Оlkhovych O. , Taran N. , Hrechishkina S. , Voitsekhivska O. , Panuta O. , Voitsekhivskyi V. , Belava V.

Journal of Ecological Engineering

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2022

|

tom Vol. 23, nr 8

249--259

EN

The estimation of the protein content and amino acid composition under the influence of metal nanoparticles (Mn, Cu, Zn, Ag) for seven species of aquatic macrophytes: Limnobium laevigatum (Humb. & Bonpl.ExWilld.), Pistia stratiotes L., Salvinia natans L., Elodea canadensis Michx., Najas guadelupensis (Spreng.) Magnus, Vallisneria spiralis L. and Riccia fluitans L. was conducted. The plants were exposed during 7 days on the experimental solutions of metal nanoparticles at the rate of 1 g of plant per 100 ml of the mixture of stock colloidal solutions of metal nanoparticles (Mn – 0.75 mg/l, Cu – 0.37 mg/l, Zn – 0.44 mg/l, Ag+, Ag2O – 0.75 mg/l) diluted 200 times. In the five investigated species, reduction of the protein content was observed. However, this indicator remained stable only in P. stratiotes (52 mg/ml) and, conversely, increased in V. spiralis (46 mg/ml to 51 mg/ml). The content of the studied amino acids in N. guadelupensis decreased by 46% (from 112.05 mmol/g to 60.15 mmol/g), in R. fluitans – by 44% (from 104.06 mmol/g to 58.25 mmol/g), in S. natans – by 23% (from 90.08 mmol/g to 69.59 mmol/g), in E. canadensis – by 10% (from 143.92 mmol/g to 129.4 mmol/g), and in P. stratiotes as well as in L. laevigatum – by 8% (from 210.65 mmol /g to 193.77 mmol/g and with 155.0 mmol/g to 142.60 mmol/g), but in V. spiralis, on the contrary, increased by 7% (from 91.31 mmol/g to 97.59 mmol/g). Changes in the composition and content of amino acids for each species of aquatic plant were analyzed. It was suggested that the studied plants, which belong to different families, have different defense mechanisms, according to which the amino acid composition of plants varies.

18

A Convenient Synthesis of D,L-Selenomethionine

88%

Ran X. G. , Cao D. R. , Wang L. Y. , Lin Y. C.

Polish Journal of Chemistry

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2009

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tom Vol. 83, nr 3

431-435

EN

A convenient synthesis of D,L-selenomethionine from a-bromo-g-butyrolactone in 4 steps and 26% over all yield has been described.

19

Factors regulating the compositions and distributions of dissolved organic matter in the estuaries of Jiaozhou Bay in North China

88%

Hu J. , Zou L. , Wang J. , Ren Q. , Xia B. , Yu G.

Oceanologia

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2020

|

tom No. 62 (1)

101--110

EN

Water samples collected from the Jiaozhou Bay every two months between April 2016 and February 2017 were analyzed for dissolved organic carbon (DOC), particulate organic carbon (POC), total dissolved carbohydrates (TCHO), total hydrolyzed amino acids (THAA), and chromophoric dissolved organic matter (CDOM) to explore the biogeochemical processes of dissolved organic matter (DOM) in anthropogenic estuarine and coastal environments. In addition, nutrients, chlorophyll a and COD (chemical oxygen demand) in these samples were also analyzed. All parameters exhibited temporal and spatial variations: POC 0.13-22.40 mg/L (average 1.75 mg/L), DOC 0.98-32.75 mg/L (average 5.04 mg/L), COD 0.23-7.58 mg/L (average 1.67 mg/L), TCHO 0.34-14.09 µM (average 3.18 µM), THAA 0.89-8.30 µM (average 4.04 µM), and the absorption coefficient a(355) of CDOM 0.23-16.35 m − 1 (average 3.09 m − 1). The temporal and spatial variations in the concentrations of TCHO, THAA, and DOC implied that the DOM in the study areas had a relatively higher biochemical activity. The canonical correspondence analysis (CCA) and maximal information coefficient (MIC) revealed that seasonal variations in temperature and the phosphate concentration were the dominant factors regulating the DOM distributions in Jiaozhou Bay, while riverine inputs and in situ reproduction mainly controlled the DOM compositions.

20

Bis(2-amidophenyl) Diselenides Derived from Amino Acids and Dipeptides: Synthesis, Antiviral and Antimicrobial Activity

88%

Palus J. , Dąbrowska E. , Piętka-Ottlik M. , Piasecki E. , Młochowski J.

Polish Journal of Chemistry

|

2008

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tom Vol. 82, nr 5

1015-1022

EN

Synthesis of bis(2-aminophenyl) diselenide 1 derivatives, having amino acids and dipeptides moieties, has been reported. This process has been realized by acylation of both amine groups in 1 us ing N-Boc blocked amino acids 8 in the presence of DCC and HOBT, followed by deprotection to hydrochlorides 9. The free amines 2 have been obtained by removing the protective groups. In the similar way dipeptides 3, 10 and 11 have been prepared. Selected compounds have been tested as potential antiviral, antibacterial and antifungial agents.