Subunit structure of glycinin and its molecular species based on RP-HPLC, gel electrophoresis and SEC studies

Glycinin and its molecular species (glycinin I and glycinin II) were separated and isolated. The number and kind of subunits of glycinin, glycinin I and glycinin II were determined. Studies were carried out under different experimental conditions using slab gel electrophoresis, size-exclusion chromatography and reversed-phase high performance liquid chromatography. Gel electrophoresis was done using both continuous and discontinuous system and under varying concentrations of resolving gel. In addition, the subunits were separated by reversed phase using gradient program. Glycinin and glycinin II were found to have 12 subunits each while glycinin I showed six subunits. Molecular weight and weight ratio in each case were also determined.     

Exploring Antagonistic Metabolites of Established Biocontrol Agent of Marine Origin

Biocontrol ability of Pseudomonas aeruginosa ID 4365, a biocontrol agent of groundnut phytopathogens from marine origin, was previously attributed to the production of pyoverdin type of siderophores. However, pyoverdin-rich supernatants of this organism showed better antifungal activity compared to equivalent amount of purified pyoverdin indicating presence of undetected metabolite(s) in pyoverdin rich supernatants. On the basis of observation that antagonistic activity was iron-dependent and iron-independent, an attempt was made to detect the presence of additional metabolites. In addition to pyoverdin, strain produced additional siderophores, viz. pyochelin and salicylic acid. Two broad spectrum antifungal compounds, viz. pyocyanin and phenazine-1-carboxylic acid, were detected, characterized, and activity against phytopathogens was demonstrated. Iron- and phosphate-dependent co-production of siderophores and phenazines was confirmed. Strain showed additional features like production of hydrogen cyanide, indol-3-acetic acid, and phosphate solubilization.     

Indirect resolution of baclofen enantiomers from pharmaceutical dosage form by reversed-phase liquid chromatography after derivatization with Marfey's reagent and its structural variants

A high-performance liquid chromatographic (HPLC) method was developed for chiral assay of baclofen enantiomers in pharmaceutical formulations using an indirect approach. Baclofen enantiomers were derivatized with Marfey's reagent (FDNP-L-Ala-NH2) and its structural variants FDNP-L-Phe-NH2, FDNP-L-Val-NH2, FDNP-L-Leu-NH2 and FDNP-L-Pro-NH2. The resultant diastereomers were separated on RP-TLC [triethylammonium phosphate buffer (pH 4.0, 50 mm)-acetonitrile, 50:50] and on a C18 column using a linear gradient (45 min) of acetonitrile and 0.01% aqueous trifluoroacetic acid (TFA) with UV detection at 340 nm. The differences in the retention times (Delta t R) of diastereomers due to the five chiral reagents were compared. The maximum and minimum difference in retention times between separated diastereomers was for FDNP-L-Leu-NH2 and FDNP-L-Pro-NH2, respectively. The effect of flow rate, acetonitrile content and TFA concentration on resolution was studied. The method was validated for linearity, repeatability, limit of detection and limit of quantification.     

Enantioresolution of Amino Acids: A Decade’s Perspective,Prospects and Challenges

Both from academic and industrial points of view enantioseparation of dl-amino acids continues to be a subject of immense importance and enjoys a great analytical significance in various fields, such as in the studies of fossils, origin of life, disease diagnosis, quality of food and beverages, etc. The present paper is a topical collection of recent advances along with a discussion on possible challenges in chiral amino acid analysis and is intended to present the existing state of knowledge on the topic as a particular facet of chromatography (and electrophoretic techniques). It presents a critical overview of the state-of-the-art of the topic, with critically selected examples to point the reader to trends and likely future developments and to give a selection of important references to the current literature.

     

Critical micelle concentration and self-aggregation of hexadecyltrimethylammonium bromide in aqueous glycine and glycylglycine solutions at different temperatures

Conductivities, densities and ultrasonic speeds measurements of hexadecyltrimethylammonium bromide (HTAB) in aqueous solutions of glycine (Gly) and glycylglycine (Gly-Gly) have been made at various temperatures. The critical micelle concentration (CMC), the degree of ionization (??) of the micelles, standard free energy, enthalpy, and entropy of the micellization process (??G _m ^° , ??H _m ^° , and ??S _m ^° ) for the present systems were estimated at different temperatures. The CMC values of HTAB in aqueous Gly and Gly-Gly were also evaluated by density and ultrasonic speed measurements. Apparent molar volumes, (V _?), apparent molar volumes at infinite dilution, (V _? ^° ), apparent molar compressibilities, (K _?), of HTAB in the pre- and post-micellar regions, and volume change on micellization (??V _? ^m ) were also estimated. Large positive values of T??S _m ^° and small negative values of ??H _m ^° suggest that micellization process is driven primarily by entropy increase. The increase in ??V _? ^m and K _? with rise in temperature is indicative of less compact micellar structure of HTAB in presence of amino acid additives. These data suggest that amino acids are solubilised probably in the palisade layer of the micelle.     

(S)‐Naproxen as a platform to develop chiral derivatizing reagent for reversed‐phase high‐performance liquid chromatographic enantioseparation of analytes having a carbonyl functional group

(S)‐Naproxen was used to synthesize a chiral reagent, (S)‐2‐(6‐methoxynaphthalen‐2‐yl)propanehydrazide, by itsreaction with hydrazine hydrate in the presence of dicyclohexylcarbodiimide as coupling agent. The reagent was characterized and its chiral purity was established. It was used as a chiral derivatizing reagent for the synthesis of hydrazone diastereomers, under microwave irradiation, of certain chiral aldehydes and ketones. The respective diastereomers were separated by reversed‐phase high‐performance liquid chromatography using a binary solvent combination containing trifluoroacetic acid. The diastereomers were detected at 231 nm. The method was validated for accuracy, precision, and limit of detection (LOD). For a series of hydrazones the LOD was found to be in the range 1.62–1.65 pmol/mL. Copyright © 2012 John Wiley & Sons, Ltd.     

Indirect enantioseparation of proteinogenic amino acids using naproxen‐based chiral derivatizing reagent and HPLC

Diastereomers of 18 proteinogenic amino acids were synthesized under microwave irradiation and by vortexing using (S)‐naproxen–benzotriazole as chiral derivatizing reagent. The diastereomers synthesized by two approaches were found to be identical in terms of their characterization and chromatographic data. A linear gradient of triethylammonium phosphate (pH 3.5)–acetonitrile (30–65%, within 35 min) was found to be successful using reversed‐phase high‐performance liquid chromatography for their separation. Detection was carried out at 231 nm and sharp peaks were obtained. The method was validated for accuracy, precision and limit of detection. Copyright © 2012 John Wiley & Sons, Ltd.     

Kinetics of evaporation of some liquids by thermogravimetry

Latent heat of evaporation is one of the decisive factors in the design and operation of chemical plants [1], Brennan et al. [2] have shown that the heat of evaporation of a liquid and the activation energy of evaporation, E^evap_act are found, as expected, to be numerically similar. We present here some results on the kinetics of evaporation of five liquids (selected at random) based on TG data.     

Synthesis of (S)-naproxen-benzotriazole and its application as chiral derivatizing reagent for microwave-assisted synthesis and indirect high performance liquid chromatographic separation of diastereomers of penicillamine, cysteine and homocysteine

(S)-Naproxen-benzotriazole was synthesized by the reaction of (S)-naproxen with 1H-benzotriazole using coupling reagent dicyclohexyl carbodiimide and 4-dimethylamino pyridine (DCC/DMAP). It was used as chiral derivatizing reagent for microwave irradiated synthesis of diastereomers of penicillamine, cysteine and homocysteine. The diastereomers were separated by reversed phase high performance liquid chromatography using gradient elution of triethylammonium phosphate (pH 3.5)-acetonitrile (30-65% within 30 min). The method was validated for accuracy, precision, and limit of detection.