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At least 1,333 records · Page 74Linked to original sources
PubMed1977

Resolution of molecular species of intact serine and ethanolamine phosphatides by argentation chromatography of their trifluoroacetamides.

An effective resolution of intact phosphatidylserines on the basis of unsaturation has been achieved by conventional argentation thin layer chromatography (TLC) following trifluoracetylaction. The trifluoroacetamides are prepared by treatment with trifluoroacetic anhydride or N-methyl-bis-trifluoroacetamide. The acetamides are resolved with chloroform-methanol-water (65:25:4, v/v/v) on Silica Gel G containing 20% silver nitrate. Subfractions with 0-6 double bonds per molecule were obtained for the phosphatidylserines of pig and ox brain, pig erythrocytes, rat liver, and rabbit skeletal muscle. The preparation of trifluoroacetamides is also advantageous for the silver ion fractionation of phosphatidylethanolamines. The method is applicable to metabolic studies of molecular species using radioactive precursors of neutral lipids, phosphorus, and nitrogenous bases.

Acetamides↗
PubMed1991

Stereospecific synthesis of antitumor active thioether PAF analogs.

A novel stereospecific synthesis of antitumor active thioether analogs of platelet-activating factor (PAF) is reported. The synthesis is based upon: i) the use of D-serine to provide the chiral center for the construction of the optically active phospholipid molecule; ii) development of the sn-1-thioalkyl function via thioacetate displacement of methanesulfonate-activated primary hydroxyl group followed by alkylation of the sn-1-thiolate function; and iii) introduction of the phosphocholine moiety through the 2-chloro-2-oxo-1,3,2-dioxaphospholane/trimethylamine sequence. The entire scheme relies on the use of a single protecting group. The synthetic thioether phospholipid 1-S-hexadecyl-2-N-acetamidodeoxy-sn-glycero-3-phosphocholine has been shown to be a potent antitumor active phospholipid, exhibiting tumor cytotoxicity against a lymphoblastoid lymphoma (Li-A) cell line and a malignant histiocytic (DHL-4) cell line of human origin at the same level of potency as ET-18-OMe and 1-O-octadecyl-2-N-acetamidodeoxy-sn-glycero-3-phosphocholine. The synthetic method described has a great deal of flexibility, providing a convenient general route to a wide range of thioether PAF analogs.

Antineoplastic Agents↗
PubMed2003

Cerebrosides and terpene glycosides from the root of Aster scaber.

Three cerebrosides 2, 3, and 5 and two terpene glycosides 1 and 4 have been isolated from the methanol extract of the root of Aster scaber. Their structures were determined as 3-O-beta-D-glucuronopyranosyl-oleanolic acid methyl ester (1), (2S, 3S, 4R, 2'R, 8Z, 15'Z)-N-2'-hydroxy-15'-tetracosenoyl-1-O-beta-D-glucopyranosyl-4-hydroxy-8-sphingenine (2), (2S, 3S, 4R, 8Z)-N-octadecanoyl-1-O-beta-D-glucopyranosyl-4-hydroxy-8-sphingenine (3), 1alpha-hydroxy-6beta-O-beta-D-glucosyl-eudesm-3-ene (4), and (2S, 3S, 4R, 2'R, 8Z)-N-2'-hydroxy-hexadecanoyl-1-O-beta-D-glucopyranosyl-4-hydroxy-8-sphingenine (5) on the basis of spectroscopic methods.

Aster Plant↗
PubMed2004

A new cycloartane glycoside from Camptosorus sibiricus Rupr.

A new cycloartane glycoside was isolated from the dried whole herbs of Camptosorus sibiricus Rupr By means of chemical (hydrolysis) and spectroscopic methods (IR, 1D, and 2D NMR, ESI-MS), the structure was established as 3beta, 7beta, 24beta, 25, 30-pentahydroxycycloartane-3-omicron-beta-D-glucopyranoside-24-omicron-beta-D-glucopyranoside (1).

Glycosides↗
PubMed2004

Optical purity determination of (S)-ibuprofen in tablets by achiral gas chromatography.

An optical purity test was indirectly performed on (S)-ibuprofen as its diastereomeric (R)-(+)-1-phenylethylamide derivative using achiral gas chromatography (GC). The method for the determination of trace (R)-ibuprofen (optical impurity), within the range 1.0 to 50 ng, from a racemic ibuprofen standard was linear (r = 0.9997) with acceptable precision (% RSD < or = 5.3) and accuracy (% RE = 0.7 - -3.9). Similar results were obtained with the method validation for the quantification of (S)-ibuprofen within the range 0.1 to 2.0 microg using a (S)-ibuprofen standard. When applied to seven different commercial (S)-ibuprofen products, their optical purities (98.7 - 99.1%) were determined with good precision (% RSD < or = 4.0).

Chromatography, Gas↗
PubMed2001

Origin of organic molecules and biomolecular homochirality.

Theories about the origin of biomolecular homochirality, which seems to be a prerequisite for the creation of life, are discussed. First, possible terrestrial and extraterrestrial sources of organic molecules are outlined. Then, mechanisms for the formation of enantiomerically enriched compounds and for the amplification of their chirality are described.

Amino Acids↗
PubMed2003

Near-infrared fluorescence imaging of lymph nodes using a new enzyme sensing activatable macromolecular optical probe.

The aim of this study was to validate the use of near infrared fluorescence imaging (NIRF) using enzyme-sensitive optical probes for lymph node detection. An optical contrast probe that is activated by cystein proteases, such as cathepsin B, was used to visualize lymph nodes by NIRF reflectance imaging. In order to quantitate the uptake of the optical probe in lymphatic tissue, the biodistribution was assessed using the Indium-111 labeled optical probe. Sixteen Balb-c mice were injected either intravenously (i.v.) or subcutaneously (s.c.) with the NIRF-probe (2 micromol cyanine (Cy)/animal; i.v., n=10; s.c., n=6) and imaged 24 h after injection. Signal intensities and target-to-background ratios of various lymph nodes were measured by manual regions of interest (ROIs). Additional signal intensity measurements were performed of excised lymph nodes (n=21) from i.v. injected mice (24 h after injection) and compared with excised lymph nodes (n=8) of non-injected mice. The probe employed in this study was lymphotropic with approximately 3-4% accumulation in lymph nodes (3.4+/-0.8% ID/g). Measurements of the excised lymph nodes (after i.v. injection) confirmed a significant increase in lymph node fluorescence signal from baseline 26+/-7.6 arbitary units (AU) to 146+/-10.9 AU (p<0.0001). A significant increase in lymph node fluorescence signal was also seen in vivo throughout the body after i.v. injection (96+/-7.8 AU) and/or regionally after s.c. injection (141+/-11.5 AU) in comparison with baseline autofluorescence (26+/-7.6 AU). Target-to-background ratio was significantly higher after s.c. injection (6.6%+/-0.81) compared with i.v. injection (4.8+/-0.67%). Detection and visualization of lymph nodes is feasible by NIRF imaging using a cystein-protease sensitive optical probe.

Animals↗
PubMed2000

MJ1647, an open reading frame in the genome of the hyperthermophile Methanococcus jannaschii, encodes a very thermostable archaeal histone with a C-terminal extension.

All archaeal histones studied to date have similar lengths, 66 to 69 amino acid residues that form three alpha-helices separated by two beta-strand loop regions which together constitute a histone fold. In contrast, the eukaryal nucleosome core histones are larger, 102 to 135 residues in length, with N-terminal and C-terminal extensions flanking the histone fold that participate in gene regulation and higher-order chromatin assembly. In the Methanococcus jannaschii genome, MJ1647 was annotated as an open reading frame predicted to encode an archaeal histone with an approximately 27-amino-acid C-terminal extension, and we here document the DNA binding and assembly properties and thermodynamic stability parameters of the recombinant product of MJ1647 synthesized in Escherichia coli with (rMJ1647) and without (rMJ1647delta) the C-terminal extension. The presence of the C-terminal extension did not prevent homodimer formation or inhibit DNA binding, but the complexes formed by rMJ1647, presumably archaeal nucleosomes containing a (rMJ1647)4 tetramer, were apparently less stable than those formed by (rMJ1647delta)4. The presence of the C-terminal extension increased the thermostability of rMJ1647 when compared with rMJ1647delta in 0.2 M KCl at pH 4 but not in the absence of KCl at pH 1. Based on thermal unfolding transitions, rMJ1647 and rHAfB generated by expression of AF0337 cloned from the genome of the related hyperthermophile Archaeoglobus fulgidus in E. coli were found to have higher thermodynamic stabilities than all previously studied archaeal histones.

Amino Acid Sequence↗