Controlled intracellular localization and enhanced antisense effect of oligonucleotides by chemical conjugation

Oligonucleotides can be covalently linked to peptides composed of any sequence of amino acids by solid phase fragment condensation. The peptides incorporated into the conjugates include nuclear localizing signals (NLS), nuclear export signals (NES), membrane fusion domain of some viral proteins and some designed peptides with amphipathic character. Evaluation of biological properties of DNA-peptide conjugates indicated that (a) the conjugates could bind to target RNA and dsDNA with increased affinity, (b) the conjugates were more resistant to cellular nuclease degradation, (c) the conjugate-RNA hybrids could activate RNase H as effectively as native oligonucleotides, (d) the conjugates with fusion peptides showed largely enhanced cellular uptake, (e) the conjugates with NLS could be predominantly delivered into the cell nucleus, (f) the conjugates with NES could be localized in the cytoplasm. As a result, antisense oligonucleotides conjugated with NLS could inhibit human telomerase in human leukemia cells much more strongly than phosphorothioate oligonucleotides.     

Enhancement of the photoluminescence of CdSe quantum dots during long-term UV-irradiation: privilege or fault in life science research?

The present study describes an impressive enhancement of the photoluminescence (PL) intensity of low-temperature synthesized CdSe nanocrystals (75 degrees C) during long-term UV-irradiation. The integrated PL-intensity of CdSe core and CdSe/ZnS core/shell nanocrystals, dispersed in chloroform, enhanced about 3 and 6 times, respectively, during 9 h exposure to UV-light, without any significant changes in the characteristic absorbance spectra and shifting of PL-spectra. After termination of the irradiation a comparatively slow photobleaching was detected with tau(1/2) = 6 h for CdSe core and tau(1/2) = 14 h for CdSe/ZnS core/shell nanocrystals. The most impressive was the effect of UV-irradiation on the photoluminescence of water-soluble CdSe nanocrystals. The integrated PL-intensity enhanced about 10 times during 11 h exposure to UV-light and the improved PL-intensity was preserved during 3 days after termination of the irradiation without any significant photobleaching. The results are discussed in the context of application of CdSe nanocrystals as novel fluorophores in life science experiments.     

Transition from complete to partial wetting within membrane compartments

Wetting and dewetting phenomena are ubiquitous, but wetting transitions have been reported only in a few experimental systems. In this work, we present a wetting transition in a mesoscopic membrane compartment for the first time. A two-phase aqueous polymer solution was encapsulated in a giant vesicle (few tens of micrometers in size). The polymers used are poly(ethyleneglycol) (PEG) and dextran. By increasing the polymer concentration in the vesicle, the PEG-rich phase changed from complete wetting to partial wetting of the membrane.     

Bis-macromonomers of 2-alkyl-2-oxazolines–synthesis and polymerization

Poly(2-alkyl-2-oxazoline)s having an acrylate group at both chain ends were synthesized by terminating living bifunctional poly(2-methyl-2-oxazoline) or poly(2-ethyl-2-oxazoline) with acrylic acid. These macromonomers have been polymerized to the corresponding polyoxazoline networks. Thermal as well as UV-initiated free radical polymerization were applied and the influence of the polymerization conditions and molecular weight of the prepolymer used on the properties of the networks were investigated. Both methods of polymerization produced high fractions of soluble material, probably due to the low concentration of the acrylate end groups.     

Recent developments in the field of bending rigidity measurements on membranes

This review gives a brief overview of experimental approaches used to assess the bending rigidity of membranes. Emphasis is placed on techniques based on the use of giant unilamellar vesicles. We summarize the effect on the bending rigidity of membranes as a function of membrane composition, presence of various inclusions in the bilayer and molecules and ions in the bathing solutions. Examples for the impact of temperature, cholesterol, some peptides and proteins, sugars and salts are provided and the literature data are discussed critically. Future directions, open questions and possible developments in this research field are also included.     

Nonradioactive telomerase activity assay by microchip electrophoresis: privileges to the classical gel electrophoresis assay

The present study accents on the privileges of microchip-based electrophoresis to the conventional gel electrophoresis in separation of telomerase repeat amplification protocol/polymerase chain reaction (PCR) ladder products obtained in telomerase-catalyzed reaction in cancer cells. We try to clarify the interpretation of the results obtained by both electrophoretic procedures and to avoid misinterpretation as a result of PCR-dependent artefacts.     

Fabrication of quantum dot-lectin conjugates as novel fluorescent probes for microscopic and flow cytometric identification of leukemia cells from normal lymphocytes

The present study describes a synthesis of QD-lectin conjugates and their application for identification of leukaemia cells from normal lymphocytes using fluorescent confocal microscopy and flow cytometry. The results are compared with commercially available FITC-lectin.     

Tailor-made polymers and copolymers from aziridines and 1,3-oxacyclanes

Telechelic poly(tert-butylaziridine)s (polyTBA) and poly(1,3,6-trioxocane)s (polyTOC) and macromonomers were synthesized mainly by living cationic polymerization. Both, molecular weight and end-functionality distributions of polyTOC oligomers and polymers were studied using a combination of HPLC under “critical conditions”, gradient HPLC and SEC with double detection following a preparative HPLC fractionation. Monofunctional and bifunctional polyTBA with various end-groups were synthesized by the end-capping method. Several modification reactions were examined for terminal transformation of polyTBA and polyTOC hydroxy-telechelics into mono- and bifunctional vinyl ether macromonomers. Various tailor-made polymers based on uniform size telechelics and macromonomers were prepared using: 1. polymer-polymer coupling to produce block copolymers; 2. polyaddition of amino-functionalized telechelics to bisacrylamides; 3. addition of amino-polyTBA to polydienes; 4. synthesis of graft copolymers with well-defined graft component and networks.