Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Solution-grown, chain-folded lamellar crystals of poly(16-hexadecalactone) (PHDL) were crystallized isothermally from 1-hexanol at 70 degrees C. The morphology of lozenge-shaped crystals was studied by TEM and AFM. The lamellae are ca. 10 nm thick and the chains run orthogonal to the lamellar surface with folding along (110) and (110) planes. The crystal structure of PHDL was determined by XRD and election diffraction of single crystals. The chains are in the 2(1) helix conformation close to all-trans and the structure consists of an orthorhombic unit cell with a P2(1)2(1)2(1) space group with the lattice constants a = 0.746 +/- 0.001 nm, b = 0.504 +/- 0.001 nm, and c (chain axis) = 4.116 +/- 0.003 nm. There are two chains per unit cell, which exist in an antiparallel arrangement. Molecular packing structure has been studied in detail, taking into account both diffraction data and energy calculations. The setting angles, with respect to a axis, were +/-40 degrees for the corner and center chains, respectively. By using the electron and XRD data, the best molecular packing model was refined to R-factors of 0.168 and 0.196, respectively. A brief comparison of chain-packing structure is also made with related polymer structures.
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PMID:Crystal structure and morphology of poly(16-hexadecalactone) chain-folded lamellar crystals. 1608 Jan 67

Retinal is the molecule found in photoreceptor cells that undergoes a change in shape when it absorbs light. Specifically, the cis/trans isomerization of a carbon-carbon double bond in this chromophore sets in motion the chain of biochemical processes responsible for vision. Here, we obtain atomically resolved images of individual structural isomers of the retinal chromophore attached to C60 molecules and study their dynamic behaviour inside a confined space--that is, inside single-walled carbon nanotubes--using high-resolution transmission electron microscopy (HR-TEM). Sequential HR-TEM images with sub-second time resolution directly reveal the isomerization between the cis and all-trans forms of retinal, as well as conformational changes and volume-conserving effects. This work opens up the possibility of investigating in vitro the biological activities of these photoresponsive molecules on an individual basis, and the molecular imaging technique described here is a general one that can be applied to a wide range of systems.
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PMID:Imaging the dynamic behaviour of individual retinal chromophores confined inside carbon nanotubes. 1865 17

For a new anticancer drug carrier, we synthesized 4 compositions of amphiphilic stearic acidconjugated pullulan (SAP) and characterized them with FT-IR spectroscopy. Crystalline changes were verified by x-ray diffraction patterns before and after synthesis of the SAP conjugate. SAP nanoparticles were prepared by a diafiltration method, and the fluorescence spectroscopy using pyrene showed particle self-assembly in water. SAP nanoparticles were spherical in TEM photos, and particle size ranged between 200 approximately 500 nm in photon correlation spectroscopy. Release of all-trans-retinoic acid from the SAP nanoparticles was maintained over 5 weeks. For further study in vivo, we tested the cytotoxicity of SAP nanoparticles using an MTT assay, and cytotoxicity was augmented as the molar mass of stearic acid increased in human liver carcinoma HepG2 cells. Therefore, SAP nanoparticles might be a promising longterm delivery carrier for hydrophobic therapeutic molecules with the appropriate composition.
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PMID:Preparation and characterization of stearic acid-pullulan nanoparticles. 2051 75

All-trans-retinoic acid reverses malignant cell growth and induces cell differentiation and apoptosis. Poor aqueous solubility and uncertain bioavailability are the limiting factors for using all-trans-retinoic acid for tumor therapy. The objective of present study was to encapsulate the hydrophobic drug all-trans-retinoic acid in the polymer poly (lactide-coglycolide). The encapsulation was expected to improve the bioavailability and solubility of the drug. Oil in water single emulsion solvent evaporation technique used for the preparation efficiently encapsulated about 60% of the drug. The drug release profile showed a biphasic pattern with 70% of the drug being released in first 48 hrs and the residual drug showing a slow controlled release reaching up to 8 days. The particle size of 150-200 nm as determined with TEM was ideal for tumor targeting. All-trans-retinoic acid loaded nanoparticles were efficient to induce differentiation and blocked the proliferation of HL-60 cells invitro. These studies also revealed that the dosage of drug required for the therapeutic effects have been reduced efficiently. Our studies thereby demonstrate that Poly (lactide-co-glycolide) based nanoparticles may be efficient for parenteral administration of the drug.
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PMID:Poly (D,L-lactic-co-glycolide) nanoparticles for the improved therapeutic efficacy of all-trans-retinoic acid: a study of acute myeloid leukemia (AML) cell differentiation in vitro. 2274 6