Search results for "acids"

Conservation of amino-acid chromatograms.

1951

IN filter-paper partition chromatography, the ninhydrin reaction has been used almost exclusively for the identification and quantitative assay of amino-acids. One of the chief disadvantages of the blue pigment formed in this reaction is its rapid fading on filter-paper chromatograms. This makes it difficult to construct permanent or semi-permanent reference maps from which not only the type of amino-acid, but also the approximate quantity of the unknown mixture, can be deduced.

Separation of aromatic aminophosphonic acid enantiomers by capillary electrophoresis with the application of cyclodextrins

2002

The detailed studies concerning capillary electrophoresis separation of aminophosphonic acid enantiomers with various commercially available cyclodextrins are presented. The obtained results show that the separation of these stereoisomers is dependent on pH of background electrolyte, concentration of cyclodextrin as well as on the type of applied chiral selector. The separation mechanism is based on the co-operative effect of hydrogen bond type interactions enhanced by hydrophobic forces and sterical constrains between aminophosphonate and cyclodextrin. With application of elaborated method, enantiomeric baseline or partial separation of 18 alpha-aminophosphonic acids was achieved. This sep…

Phospholipid-based reverse micelles.

1990

Physicochemical investigations on the aggregation of phospholipids (mainly phosphatidylcholines) in organic solvents are reviewed and compared with the aggregation behaviour of phospholipids in aqueous medium. In particular we review the data showing that phosphatidylcholines (lecithins) form reverse micellar structures in certain apolar solvents. In these systems not only low molecular weight compounds but also catalytically active enzymes and entire cells can be solubilized. In addition, highly viscous phosphatidylcholine gels can be obtained in organic solvents upon solubilizing a critical amount of water. Generally, phospholipid-based reverse micelles can be regarded as thermodynamicall…

Reliable and simple analytical methods for determination of citrulline and metabolically related amino acids by liquid chromatography after derivatiz…

2014

We describe the development of a high-performance liquid chromatography (HPLC) method for the determination of citrulline and other amino acids relevant to intestinal diseases. The amino acids were derivatized with 9-fluorenylmethylchloroformate (FMOC-Cl) and their derivatives were separated on two different columns, a core-shell column (Halo C18) and a silica-based monolith (Chromolith Performance RP-18). The derivatization reaction was optimized with respect to pH, buffer concentration and reproducibility. The optimal derivatization conditions were achieved with 0.4 M borate buffer at pH 9.20, a constant ratio of FMOC-Cl/total amino acids (10 : 1) and 75 mM tyramine after 1 min (quenching…

Changes in ewe milk fatty acids following turning out to pasture

2008

Abstract Ten Comisana dairy ewes were selected to observe time of changing in milk fatty acids as a result of switching from stall to pasture feeding. At first, ewes were subjected to a stall-feeding period of 30 days (pre-experimental phase). After which, ewes were abruptly turned out to a vetch and oats pasture as their sole feed (experimental phase). Individual milk samples were collected on experimental days 0 (the last day of stall feeding), 1–4, 8, 11, 17 and 23. Milk and feeds fatty acid composition was determined by gas chromatography. The sudden passage from a stall to a pasture diet significantly modified the fatty acid profile of ewe milk. Medium- and long-chain fatty acids were …

An Insight into Substrate-Dependent Fluorination of some Highly Substituted Alicyclic Scaffolds

2017

The substrate-dependent fluorination of some highly-functionalized cyclopentane derivatives with multiple chiral centers has been investigated. The key steps of the stereocontrolled syntheses are the oxidative cleavage of the ring carbon–carbon double bond of readily available diexo or diendo norbornene β-amino acid derivatives followed by transformation of the resulted dialdehyde stereoisomers by reduction. Finally, substrate-directable chemodifferentiation of different types of hydroxy groups under fluorination procedures gave various densely functionalized alicyclic derivatives or heterocycles.

Polyunsaturated fatty acids and Plasmalogens in diabetics

2012

Purpose Plasmalogens (PLS) are phospholipids characterized by a vinyl ether bond and a preferential esterification of polyunsaturated fatty acids (PUFA). We have previously shown that the lack of PLS leads to retinal hyper-capillarization. We hypothesize that PLS are negative regulators of vascular development, and aimed to check their circulating levels in diabetic patients. Methods Blood samples were collected from 88 patients and 14 control subjects. Among diabetics we had 14 patients without diabetic retinopathy (DR), 12 with a mild non proliferative DR, 12 with a moderate non proliferative DR, 22 with a severe non proliferative DR and 24 with a proliferative DR (PDR). Erythrocytes were…

Hemorheological benefits of omega-3 polyunsaturated fatty acids on erythrocyte deformability in renal transplanted patients

1994

Acides gras des phospholipides plaquettaires et des lipides plasmatiques chez le rat obése Zucker

1988

AbstractThe purpose of this work was to see whether hyperlipaemia observed in genetically obese Zucker rats (fa/fa) was associated with differences in fatty-acid composition of plasma triacylglycerols, plasma phospholipids and of platelet phospholipids, in comparison with the control lean rats (Fa/-).Results showed that plasma triacylglycerols and phospholipids were increased in obese rats. In triacylglycerols, the amount of saturated and monounsaturated fatty acids was highly increased whereas the amount of the n-6 and n-3 polyunsaturated fatty acids was little modified. In plasma phospholipids, saturated and monounsaturated fatty acids were also increased, as were the n-3 fatty acids (exc…

Lipid and fatty acid profile of the retina, RPE/choroid and lacrimal gland, and associations with dietary fatty acids in human subjects

2008

Purpose The contribution of dietary lipids to the accumulation of lipids in the retina during ageing and in the course of age related maculopathies remains under debate. Our objective was to establish associations between fatty acid profiles of ocular structures, and adipose tissue as a surrogate for the past dietary intake of the subjects. Methods Lipids and fatty acids were analyzed by tandem thin-layer chromatography-flame ionization detection and gas chromatography-flame ionization detection from the neural retina, RPE/choroid, lacrimal gland and adipose tissue, collected from 19 women and 8 men, aged 59–95 years. Results DHA concentrations in the neural retina were positively associate…