02105nas a2200313   4500008004100000022001400041245010800055210006900163260001600232300001100248490000900259520118500268653001101453653003901464653001801503653001901521653001801540653001001558653001701568653001401585653002101599653002501620653002601645100001401671700001901685700001501704700001301719856005901732       1998                        eng d  a0006-300200aFormation of high axial ratio microstructures from peptides modified with glutamic acid dialkyl amides.0 aFormation of high axial ratio microstructures from peptides modi  c1998 May 28  a168-840 v13713 a<p>A growing number of amphiphiles are known to form high axial ratio microstructures (HARMs) such as the hollow cylindrical microstructures called lipid tubules. As a prelude to exploring the potential of HARMs formed from lipopeptides in controlled release drug delivery, several microstructure formation conditions were investigated. We report the preparation of several glutamic acid dialkyl amides with varying alkyl chain lengths bearing a verity of peptides (1-4 amino acids) [peptide-Glu-(NHCnH2n+1)2, n=12, 14, 16]. These surfactants have been rapidly and efficiently converted into HARMs in aqueous buffer at physiological pH and ionic strength, or in buffer containing MeOH or EtOH. Helical ribbons and tubular HARMs were produced that were stable for as long as 6 months below the phase transition temperatures of the compounds. To estimate the stability of HARMs in vivo, HARMs formed from (Pro)3-Glu(NHC16H33)2 were incubated with DOPC liposomes or fetal calf serum at 40 degreesC. HARM size and shape did not change significantly, suggesting that such lipopeptide particles can retain their morphology long enough in vivo to be useful as drug delivery vehicles.</p>10aAmides10aCalorimetry, Differential Scanning10aDrug Carriers10aDrug Stability10aGlutamic Acid10aLight10aLipoproteins10aLiposomes10aPeptides, Cyclic10aPhosphatidylcholines10aScattering, Radiation1 aLee, K, C1 aLukyanov, A, N1 aGelb, M, H1 aYager, P  uhttps://www.microfluidicsciences.com/drupal/?q=node/3102393nas a2200289   4500008004100000022001400041245009200055210006900147260001500216300001000231490000700241520154100248653001101789653001601800653003901816653001401855653003201869653001601901653002401917653001801941100002001959700001901979700001801998700001302016700001502029856005902044       1997                        eng d  a0009-308400aFormation of high-axial-ratio-microstructures from natural and synthetic sphingolipids.0 aFormation of highaxialratiomicrostructures from natural and synt  c1997 Aug 8  a21-360 v883 a<p>Amphiphiles that form high-axial-ratio-microstructures (HARMs) are being considered as novel materials for controlled release of drugs and other biologically functional molecules. HARMs consisting of tubules, ribbons, solid rods and helices are formed from sphingolipids by addition of water to a solution of amphiphile in DMF. Single molecular species of galactocerebroside (GalCer) containing long unsaturated fatty acid chains or natural GalCer containing mixed-length, non-hydroxy fatty acids (NFA-GalCer) or alpha-hydroxy fatty acids (HFA-GalCer) form cylindrical structures. In contrast, single molecular species of GalCer containing long saturated fatty acids form ribbons and helices. GalCer HARMs are typically under 100 nm in diameter and have lengths of several microns. The importance of the amide of GalCer for HARM formation was evaluated using psychosine, which forms solid fibers, whereas sphingosine and an analog of GalCer in which the amide is reduced to a secondary amine form amorphous aggregates. Single molecular species of ceramide containing long unsaturated fatty acid chains form cylindrical structures, whereas those with long saturated fatty acids form ribbons and helices. Short chain saturated ceramide also forms cylindrical structures. GalCer analogs with N-acetyl-glycine in place of the galactose form fibers whereas those with N-acetyl-proline yield amorphous material. The N-acetyl-proline-containing amphiphile can de doped into pure GalCer or NFA-GalCer without perturbing tubule formation.</p>10aAmides10aAmino Acids10aCalorimetry, Differential Scanning10aCeramides10aDelayed-Action Preparations10aFatty Acids10aGalactosylceramides10aSphingolipids1 aGoldstein, A, S1 aLukyanov, A, N1 aCarlson, P, A1 aYager, P1 aGelb, M, H  uhttps://www.microfluidicsciences.com/drupal/?q=node/32