scholarly journals Dianions of glyoxylic acid thioketals: conventent α-keto acid equivalents

1980 ◽  
Vol 58 (7) ◽  
pp. 716-722 ◽  
Author(s):  
Gordon S. Bates ◽  
S. Ramaswamy
Keyword(s):  
Acetic Acid ◽  
Reaction Temperature ◽  
Glyoxylic Acid ◽  
Alkyl Halides ◽  
Thermally Stable ◽  
Keto Acid ◽  
Optimum Conditions ◽  
Keto Acids

By varying the solvent, reaction temperature, and bases (i.e., gegenions present), optimum conditions for the alkylation of the dianions of glyoxylic acid derivatives 8 and 9 were established. It was found that the easily prepared, thermally stable, tetrahydrofuran-soluble potassium dianion of bis(ethylthio)acetic acid was readily alkylated by alkyl halides, tosylates, epoxides, and N-tosyl aziridines. The latter alkylation is being used to develop a possible cytochalasin synthesis.The alkylated products may be readily converted into the corresponding α-keto acids or methyl 2,2-bismethoxycarboxylates.

scholarly journals FLUORESCENCE HISTOCHEMISTRY OF BIOGENIC MONOAMINES A STUDY OF THE CAPACITY OF VARIOUS CARBONYL COMPOUNDS TO FORM FLUOROPHORES WITH BIOGENIC MONOAMINES IN GAS PHASE REACTIONS

1972 ◽  
Vol 20 (6) ◽  
pp. 435-444 ◽  
Author(s):  
STURE AXELSSON ◽  
ANDERS BJÖRKLUND ◽  
OLLE LINDVALL
Keyword(s):  
Acetic Acid ◽  
Gas Phase ◽  
Carbonyl Compounds ◽  
Glyoxylic Acid ◽  
Histochemical Demonstration ◽  
High Reactivity ◽  
Gas Phase Reactions ◽  
Cyclization Reactions ◽  
Biogenic Monoamines ◽  
Keto Acids

The capacity of biogenic amines to form fluorophores in histochemical gas phase reactions has been tested with 20 compounds having a carbonyl group (> C = O) as a common characteristic. Significant visible fluorescence was induced from catecholamines and indolamines with aldehydes, ketones, α-keto acids and carboxylic acids, suggesting that all of these compounds can enter fluorophore-forming cyclization reactions under the histochemical gas phase conditions. The most "reactive" reagents are found among the low molecular aldehydes, and formaldehyde and glyoxylic acid seem to be the most suitable reagents, combining high reactivity with good selectivity. Fluorescence, interesting for the histochemical demonstration of N-acetylated indolamines, was obtained from melatonin and N-acetyl-5-hydroxytryptamine with some acid reagents (glyoxylic acid, formic acid, acetic acid and pyruvic acid). A direct cyclodehydration according to the classical Bischler-Napieralski reaction is the most likely mechanism underlying this fluorophore formation. The usefulness of the various carbonyl reagents for the fluorescence histochemical demonstration of other biologically interesting amines, such as histamine, p-tyramine and octopamine, has been specially investigated.

The role of acidity profile in the nanotubular growth of polyaniline

2010 ◽  
Vol 64 (1) ◽  
Author(s):  
Elena Konyushenko ◽  
Miroslava Trchová ◽  
Jaroslav Stejskal ◽  
Irina Sapurina
Keyword(s):  
Acetic Acid ◽  
Sulfuric Acid ◽  
Reaction Temperature ◽  
Subsequent Growth ◽  
Subsequent Oxidation ◽  
Ammonium Peroxydisulfate ◽  
Aniline Oligomers ◽  
Positive Effect ◽  
Granular Morphology

AbstractConditions of polyaniline (PANI) nanotubes preparation were analyzed. Aniline was oxidized with ammonium peroxydisulfate in 0.4 M acetic acid. There are two subsequent oxidation steps and the products were collected after each of them. At pH > 3, neutral aniline molecules are oxidized to non-conducting aniline oligomers. These produce templates for the subsequent growth of PANI nanotubes, which takes place preferably at pH 2–3. At pH < 2, granular morphology of the conducting PANI is obtained. High final acidity of the medium should be avoided in the preparation of nanotubes, e.g., by reducing the amount of sulfuric acid which is a by-product. Reduction of the peroxydisulfate-to-aniline mole ratio was tested for this purpose in the present study. Lowering of the reaction temperature from 20°C to −4°C had a positive effect on the formation of nanotubes.

scholarly journals Process optimization for biodiesel production from neutralized waste cooking oil and the effect of this biodiesel on engine performance

2018 ◽  
Vol 8 (1) ◽  
pp. 121-127 ◽  
Author(s):  
Tanzer Eryilmaz
Keyword(s):  
Reaction Time ◽  
Methyl Ester ◽  
Reaction Temperature ◽  
Direct Injection ◽  
Engine Performance ◽  
Waste Cooking Oil ◽  
Biodiesel Production ◽  
Phase Reaction ◽  
Optimum Conditions ◽  
Cooking Oils

In this study, the methyl ester production process from neutralized waste cooking oils is optimized by using alkali-catalyzed (KOH) single-phase reaction. The optimization process is performed depending on the parameters, such as catalyst concentration, methanol/oil ratio, reaction temperature and reaction time. The optimum methyl ester conversion efficiency was 90.1% at the optimum conditions of 0.7 wt% of potassium hydroxide, 25 wt% methanol/oil ratio, 90 min reaction time and 60°C reaction temperature. After the fuel characteristics of the methyl ester obtained under optimum conditions were determined, the effect on engine performance, CO and NOx emissions of methyl ester was investigated in a diesel engine with a single cylinder and direct injection. When compared to diesel fuel, engine power and torque decreased when using methyl ester, and specific fuel consumption increased. NOx emission increases at a rate of 18.4% on average through use of methyl ester.

scholarly journals Convenient Genetic Encoding of Phenylalanine Derivatives through Their α-Keto Acid Precursors

Biomolecules ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1358
Author(s):  
Li Liu ◽  
Bohao Wang ◽  
Sheng Li ◽  
Fengyuan Xu ◽  
Qi He ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Genetic Code ◽  
Fluorescent Proteins ◽  
Coli Strain ◽  
Keto Acid ◽  
Phenylpyruvic Acid ◽  
Genetic Encoding ◽  
Keto Acids ◽  
Genetic Code Expansion ◽  
And Function

The activity and function of proteins can be improved by incorporation of non-canonical amino acids (ncAAs). To avoid the tedious synthesis of a large number of chiral phenylalanine derivatives, we synthesized the corresponding phenylpyruvic acid precursors. Escherichia coli strain DH10B and strain C321.ΔA.expΔPBAD were selected as hosts for phenylpyruvic acid bioconversion and genetic code expansion using the MmPylRS/pyltRNACUA system. The concentrations of keto acids, PLP and amino donors were optimized in the process. Eight keto acids that can be biotransformed and their coupled genetic code expansions were identified. Finally, the genetic encoded ncAAs were tested for incorporation into fluorescent proteins with keto acids.

Hydrohalogenation of Unactivated Alkenes Using a Methanesulfonic Acid/Halide Salt Combination

Synthesis ◽  
2021 ◽  
Author(s):  
Jean-François Paquin ◽  
Xavier Bertrand ◽  
Pascal Paquin ◽  
Laurent Chabaud
Keyword(s):  
Acetic Acid ◽  
Methanesulfonic Acid ◽  
Alkyl Halides ◽  
Halide Salt ◽  
Acid Halide ◽  
Halide Salts

AbstractThe hydrochlorination, hydrobromination, and hydroiodination of unactivated alkenes using methanesulfonic acid and inorganic halide salts (CaCl2, LiBr, LiI) in acetic acid are reported. This approach uses readily available and inexpensive reagents to provide the alkyl halides in up to 99% yield. An example of deuteriochlorination using deuterated acetic acid as the solvent is also demonstrated.

Transport of alpha-keto analogues of amino acids across blood-brain barrier in rats

1982 ◽  
Vol 243 (4) ◽  
pp. E272-E277
Author(s):  
A. R. Conn ◽  
R. D. Steele
Keyword(s):  
Blood Brain Barrier ◽  
Transport System ◽  
Ketone Bodies ◽  
Brain Barrier ◽  
Sodium Pentobarbital ◽  
Keto Acid ◽  
Dual Isotope ◽  
Common System ◽  
Blood Brain ◽  
Keto Acids

The transport of 14C-labeled alpha-keto acids across the blood-brain barrier (BBB) was studied in rats anesthetized with sodium pentobarbital using a modification of a single-injection dual-isotope technique. alpha-Keto acids were found to cross the BBB via a saturable carrier-mediated transport system that may be specific based on lack of inhibition by glucose, isoleucine, and ketone bodies on the uptake of tracer levels of 14C-labeled alpha-keto acids. alpha-Ketobutyrate and alpha-keto-gamma-methiolbutyrate, both straight chain keto acids, and alpha-ketoisocaproate, a branched-chain keto acid, appeared to cross the barrier by a common carrier based on cross-inhibition studies. Aromatic keto acids had no effect on the uptake of tracer levels of these 14C-keto acids. The Km of transport of alpha-ketobutyrate, alpha-ketoisocaproate, and alpha-keto-gamma-methiolbutyrate, was 0.11, 0.60, and 0.33 mM, respectively. The corresponding Vmax was 15.7, 73.3, and 30.2 nmol . g-1 . min-1. Phenylpyruvate was found not to cross the BBB. Inhibition of brain uptake of alpha-keto acids by propionate and pyruvate, and not by DL-beta-hydroxybutyrate suggests that alpha-keto acids and monocarboxylic acids are transported either via a common system independent of ketone bodies or share an affinity with a monocarboxylic acid and an alpha-keto acid transport system.

Transamination of branched-chain keto acids by isolated perfused rat kidney.

1978 ◽  
Vol 235 (1) ◽  
pp. E47
Author(s):  
W E Mitch ◽  
W Chan
Keyword(s):  
Amino Acids ◽  
Rat Kidney ◽  
Branched Chain Amino Acids ◽  
Keto Acid ◽  
Branched Chain Amino Acid ◽  
Keto Acids ◽  
Perfused Rat Kidney ◽  
Branched Chain ◽  
Branched Chain Keto Acids ◽  
Isolated Rat

Isolated rat kidney perfused without substrate released serine, glycine, and taurine, and substantially smaller amounts of other amino acids. When branched-chain keto acids were added, the corresponding amino acids were released at rates amounting to 15-25% of keto acid disappearance. Perfusion with 2 mM alpha-keto-isovalerate or alpha-keto-beta-methylvalerate caused an increased glucose release amounting to 18-23% of keto acid disappearance. The activity of branched-chain amino acid transferase (BATase) was significantly stimulated by perfusion with the analogue of leucine, but not by perfusion with alpha-ketoglutarate, the analogues of valine or isoleucine, or with leucine itself. These findings document that the kidney converts branched-chain keto acids in part to the corresponding amino acids and suggest that the keto analogue of leucine may be involved in the control of renal BATase activity, thereby indirectly regulating the metabolism of branched-chain amino acids.

Observations on the Zak Cholesterol Reaction: Glacial Acetic Acid Purity, a More Sensitive Absorbance Peak, and Bromide Enhancement

1962 ◽  
Vol 8 (3) ◽  
pp. 296-301 ◽  
Author(s):  
Robert E Bowman ◽  
Richard C Wolf
Keyword(s):  
Acetic Acid ◽  
Glacial Acetic Acid ◽  
Enhancement Effect ◽  
Optimum Conditions ◽  
Absorbance Spectrum ◽  
Iodide Ions ◽  
Color Reagent ◽  
Absorbance Peak

Abstract An examination of the absorbance spectrum of the Zak cholesterol reaction, made with two brands of commercially available reagent-grade glacial acetic acid, showed not only the expected peak at 560 mµ, but an additional, higher peak at about 490 mµ. A specially purified glacial acetic acid did not show this 490 mµ peak. Conversely, increasing the ratio of color reagent to glacial acetic acid from 0.8 to 1.2 (v/v) greatly increased the height of the absorbance peak at 480 mµ and eliminated the 560 mµ peak. Under optimum conditions of time and color-reagent concentrations, the 480 mµ peak affords approximately double the sensitivity for cholesterol as compared to the 560 mµ peak. Finally, it was observed that the reported interference of bromide and iodide ions in the Zak reaction results almost entirely from an enhancement effect on the color by the cholesterol itself, and that the addition of about 100 µg. NaBr per milliliter of glacial acetic acid prior to reaction produced the full enhancement of 50 per cent greater color, and virtually eliminated interference at 560 mµ from additional amounts of bromide or iodide salts.

Transesterification of Degummed Jatropha curcas Oil Using Tri-potassium Phosphate as Base Catalyst

2015 ◽  
Vol 13 (3) ◽  
pp. 395-406 ◽  
Author(s):  
Y. V. V. Satyanarayana Murthy ◽  
Rajeswara R. Resapu ◽  
M. R. S. Satyanarayana ◽  
Ramakrishna Jogi
Keyword(s):  
Reaction Temperature ◽  
Jatropha Curcas ◽  
Methyl Esters ◽  
Potassium Phosphate ◽  
Molar Ratio ◽  
Base Catalyst ◽  
Optimum Conditions ◽  
Drastic Reduction ◽  
Biodiesel Standards ◽  
Atomic Absorption Spectra

Abstract Jatropha curcas oil and methanol are transesterified using potassium triphosphate as base catalyst. The effects of methanol to oil molar ratio, reaction temperature, stirring speed, catalyst concentration, solubility and its reusability on the yield of biodiesel are investigated. The base catalyst tri-potassium phosphate (K3PO4) is found to be highly suitable for oils having less than 1.5% free fatty acids (FFA). Highest biodiesel yield (approximately 92%) is acquired under optimum conditions of 9:1 methanol to oil molar ratio, 2% catalyst at 70°C reaction temperature at a stirring speed of 650 rpm. The chemical activity of K3PO4 is found to be similar to that of base catalyst potassium hydroxide (KOH) and the catalyst solubility in biodiesel as determined by atomic absorption spectra is only 4.81 ppm. It has been found that K3PO4 is highly hygroscopic and its reusability drastically decreases upon further usage and it can be reused only in wetted condition for three continuous usages with drastic reduction in catalytic strength. The biodiesel samples prepared were tested for several physicochemical properties and compared with the values of European biodiesel standards. The fatty acid methyl esters (FAME), also referred to as jatropha methyl esters (JME) in this paper, have been analyzed by gas chromatography and thermogravimetric analysis.

scholarly journals Accumulation of α-Keto Acids as Essential Components in Cyanide Assimilation by Pseudomonas fluorescens NCIMB 11764

1998 ◽  
Vol 64 (11) ◽  
pp. 4452-4459 ◽  
Author(s):  
Daniel A. Kunz ◽  
Jui-Lin Chen ◽  
Guangliang Pan
Keyword(s):  
Pseudomonas Fluorescens ◽  
Culture Fluid ◽  
Maximal Activity ◽  
Resonance Spectroscopy ◽  
Keto Acid ◽  
Growth Substrate ◽  
Reaction Products ◽  
Cell Extracts ◽  
Keto Acids ◽  
Essential Components

ABSTRACT Pyruvate (Pyr) and α-ketoglutarate (αKg) accumulated when cells of Pseudomonas fluorescens NCIMB 11764 were cultivated on growth-limiting amounts of ammonia or cyanide and were shown to be responsible for the nonenzymatic removal of cyanide from culture fluids as previously reported (J.-L. Chen and D. A. Kunz, FEMS Microbiol. Lett. 156:61–67, 1997). The accumulation of keto acids in the medium paralleled the increase in cyanide-removing activity, with maximal activity (760 μmol of cyanide removed min−1 ml of culture fluid−1) being recovered after 72 h of cultivation, at which time the keto acid concentration was 23 mM. The reaction products that formed between the biologically formed keto acids and cyanide were unambiguously identified as the corresponding cyanohydrins by 13C nuclear magnetic resonance spectroscopy. Both the Pyr and α-Kg cyanohydrins were further metabolized by cell extracts and served also as nitrogenous growth substrates. Radiotracer experiments showed that CO2 (and NH3) were formed as enzymatic conversion products, with the keto acid being regenerated as a coproduct. Evidence that the enzyme responsible for cyanohydrin conversion is cyanide oxygenase, which was shown previously to be required for cyanide utilization, is based on results showing that (i) conversion occurred only when extracts were induced for the enzyme, (ii) conversion was oxygen and reduced-pyridine nucleotide dependent, and (iii) a mutant strain defective in the enzyme was unable to grow when it was provided with the cyanohydrins as a growth substrate. Pyr and αKg were further shown to protect cells from cyanide poisoning, and excretion of the two was directly linked to utilization of cyanide as a growth substrate. The results provide the basis for a new mechanism of cyanide detoxification and assimilation in which keto acids play an essential role.

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