Search results for "MOLECULE"
showing 10 items of 5162 documents
Photoreactions in Langmuir-Blodgett-Kuhn multilayer assemblies of liquid crystalline azo-dy side-chain polymers
2007
Reversible and persistent optical data storage in Langmuir-Blodgett-Kuhn liquid crystalline systems has been reported recently. Depending on the molecular structure, the trans-cis isomerization in these systems (induced by illumination with UV- and VIS-light) leads to different macroscopic behavior of the chromophore percentage on the photo-induced structural changes in a series of statistical copolymers.
Human artificial membranes in (bio)analytical science: Potential for in vitro prediction of intestinal absorption-A review
2021
Abstract Artificial membranes for investigation of the human absorption (oral, dermal or respiratory) of target organic compounds are aimed at mimicking the interactions occurring at and within the cell lipid membrane. Biomolecules such as proteins are also integral components of the lipid membranes and play a pivotal role towards understanding the complex mechanisms of human absorption. In this review, we will differentiate biomimetic platforms based on static (batchwise) and dynamic modes. In the former, a synthetic membrane placed between two phases (donor and acceptor) mimics a given biological system to study permeability. Parallel artificial membrane permeation assays are the most com…
Towards highly luminescent phenylene vinylene films
1996
Abstract Fluorescence and electronic absorption spectra, fluorescence decay curves and fluorescence quantum yields of a series of oligo (p-phenylene vinylenes) are investigated in solution, nanoaggregates and vapour-deposited or cast ultrathin films. The film constituting molecules are varied in chain length and modified by electron donating and withdrawing substituents and bulky alkyl spacers. PPP-MO calculations serve to rationalize the resulting spectral changes. In dilute solutions, fluorescence yields of the short oligomers with alkyl or oxyalkyl substituents approach the region of unity. The yields decrease with chain length, reaching a long-chain limit of ΦF=0.4–0.7. Introduction of …
Photochemical holes under pressure: Compressibility and volume fluctuations of a protein
1991
From the pressure induced frequency shift of photochemical holes burnt into mesomorphyrin substituted horseradish peroxidase, we determined the compressibility of the protein and the vacuum frequency of the chromophore. From the compressibility, an estimation of the volume fluctuations of the biomolecule is possible.
The guanidinium group as a key part of water-soluble polymer carriers for siRNA complexation and protection against degradation.
2014
Here, the preparation of a novel block copolymer consisting of a statistical copolymer N-(2-hydroxypropyl) methacrylamide-s-N-(3-aminopropyl) methacrylamide and a short terminal 3-guanidinopropyl methacrylamide block is reported. This polymer structure forms neutral but water-soluble nanosized complexes with siRNA. The siRNA block copolymer complexes are first analyzed using agarose gel electrophoresis and their size is determined with fluorescence correlation spectroscopy. The protective properties of the polymer against RNA degradation are investigated by treating the siRNA block copolymer complexes with RNase V1. Heparin competition assays confirm the efficient release of the cargo in vi…
Macromolecules in ordered media: 5. Poly(4-vinyl pyridine)—liposome association induced by electrostatic interactions
1997
Abstract The association of water-soluble vinyl polymers to dimyristoyl phosphatidic acid unilamellar vesicles as a function of pH, temperature and salt content using steady-state fluorescence and viscometry has been investigated. Poly(4-vinyl pyridine) fluorescence data were converted to association isotherms and discussed in terms of binding and partition models. The results of this report support previous suggestions: (1) in the case of polyions the inclusion of the activity coefficient in both models is essential; (2) the parameters calculated using the two different theoretical approaches can be directly compared by the relating equation proposed for us. Finally, the excellent agreemen…
Glycidyl methacrylate derivatization of α,β-poly(N-hydroxyethyl)-dl-aspartamide and α,β-polyasparthydrazide
1997
Abstract α,β-Poly(N-hydroxyethyl)- dl -aspartamide (PHEA) and α,β-polyasparthydrazide (PAHy) are two synthetic macromolecules having many potential applications in the field of biomedical sciences. This paper describes the functionalization of PHEA and PAHy with glycidyl methacrylate (GMA), in order to introduce pendant double bonds in their chains. Derivatized PHEA and PAHy (samples PHG and PAG, respectively) at various GMA content have been obtained and characterized. It has been shown that the derivatization reaction can be controlled by varying some parameters as solvent, catalyst, pH, GMA concentration and reaction time. As expected, PAHy reacted more rapidly and more extensively than …
Stereoselective Conjugate Addition of Mixed Organoaluminum Reagents to ?,?-Unsaturated N-Acyloxazolidinones Derived from Carbohydrates.
2005
The stereoselective synthesis of β-branched carboxylic acid derivatives was accomplished by conjugate addition of mixed organoaluminum reagents to chiral α,β-unsaturated N-acyloxazolidinones. Mixed organoaluminum reagentswere generated in situ by transmetalation of Grignard or organolithium compounds with methylaluminum dichloride. Efficient stereocontrol was achieved using different bicyclic glycosamine-derived oxazolidinones, yielding alternatively (R)- or (S)-configured β-branched carboxylic acid derivatives.
Étude thermodynamique du polymère super absorbant X10 vis–à–vis de l’eau vapeur
2004
The organic polymers super absorbents present values of specific surface lower than 2m 2 /g. The isobars of adsorption of water vapor on studied polymer are of type III at ambient temperature with the hysterisis phenomena.For temperatures lower than ambient, the isobars become deformed because of an effect of chains. This type of polymer is characterized by a multi-layer adsorption which occurs before the full-course one is complete. During reactions of adsorption, the polymer undergoes rearrangement polymeric network which results from a co-operative diffusion of the water molecules and from a spacing of chain followed by an expansion of the polymeric network. Three types of water molecule…
Label-Free Detection of Protein-Ligand Interactions by the Quartz Crystal Microbalance
2005
In recent years the quartz crystal microbalance (QCM) has been accepted as a powerful technique to monitor adsorption processes at interfaces in different chemical and biological research areas. In the last decade, the investigation of adsorption of biomolecules on functionalized surfaces turned out to be one of the paramount applications of the QCM comprising the interaction of nucleic acids, specific molecular recognition of protein-receptor couples, and antigen-antibody reactions realized in immunosensors. The advantage of the QCM technique is that it allows for a label free detection of molecules. This is a result of the fact that the frequency response of the quartz resonator is propor…