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Probe Techniques (probe + techniques)

Distribution by Scientific Domains

Life Sciences	40%

Selected Abstracts

Nanogels of poly(acrylic acid): Uptake and release behavior with fluorescent oligothiophene-labeled bovine serum albumin

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010
Simona Argentiere
Abstract Nanometer-sized poly(acrylic acid) (PAA) hydrogels were synthesized by emulsion polymerization of methyl acrylate and subsequent acidic hydrolysis. The nanohydrogel was characterized by spectroscopic methods (FTIR and 1H-NMR) and scanning probe techniques, and their pH-dependent swelling behavior was studied by dynamic light scattering. To determine the suitability of PAA nanogels as pH-sensitive carriers for biomedical applications, uptake and release of an oligothiophene fluorophore and its albumin conjugated from PAA nanogels were investigated as a function of pH by absorption and photoluminescence measurements. It was observed that uptake and release processes of both the oligothiophene and its conjugate could be controlled by changing the pH of the external solution. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Effects of uniaxial stress on the magnetic properties of thin films and GMR sensors prepared on polyimide substrates

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2008
Berkem Özkaya
Abstract The effects of externally applied uniaxial stress on the magnetic properties of Co thin films and pseudo-spin-valve (PSV) structures on flexible polyimide substrates were investigated. The advantage of the polyimide substrate is its flexibility and high elasticity (,1%), which cannot be achieved using conventional crystalline substrates. The Co layers exhibit a macroscopic easy axis induced by the preparation process. When the stress is applied perpendicular to the induced in-plane easy axis, the magnetic domains in the film rotate towards the applied stress direction, which was confirmed using Kerr microscopy and magneto-optical Kerr effect (MOKE) magnetometer measurements. A Co/Cu/Ni PSV system was prepared on polyimide substrate with dc magnetron sputtering. Applying uniaxial stress leads to opposite rotation of the magnetisation directions in both layers to each other due to different signs of the magnetostriction coefficients of Co and Ni. The magnetisation and giant magnetoresistance (GMR) curves under applied stress were recorded using in situ MOKE and current in-plane four-point probe techniques, respectively. When the stress is applied perpendicular to the external magnetic field (Hext), the operating range of the GMR sensor increases, whereas the sensitivity decreases. Anisotropy energies and saturation magnetostriction values of the Co and Ni layer were determined by fitting the GMR and magnetisation curves using a micromagnetic model. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Xylem Flow and its Driving Forces in a Tropical Liana: Concomitant Flow-Sensitive NMR Imaging and Pressure Probe Measurements

PLANT BIOLOGY, Issue 6 2000
N. Wistuba
Abstract: Flow-sensitive NMR imaging and pressure probe techniques were used for measuring xylem water flow and its driving forces (i.e., xylem pressure as well as cell turgor and osmotic pressure gradients) in a tropical liana, Epipremnum aureum. Selection of tall specimens allowed continuous and simultaneous measurements of all parameters at various distances from the root under diurnally changing environmental conditions. Well hydrated plants exhibited exactly linearly correlated dynamic changes in xylem tension and flow velocity. Concomitant multiple-probe insertions along the plant shoot revealed xylem and turgor pressure gradients with changing magnitudes due to environmental changes and plant orientation (upright, apex-down, or horizontal). The data suggest that in upright and - to a lesser extent - in horizontal plants the transpirational water loss by the cells towards the apex during the day is not fully compensated by water uptake through the night. Thus, longitudinal cellular osmotic pressure gradients exist. Due to the tight hydraulic coupling of the xylem and the tissue cells these gradients represent (besides the transpiration-induced tension in the xylem) an additional tension component for anti-gravitational water movement from the roots through the vessels to the apex. [source]

Acquisition of desiccation tolerance in developing wheat embryos correlates with appearance of a fluid phase in membranes

PLANT CELL & ENVIRONMENT, Issue 11 2003
E. A. GOLOVINA
ABSTRACT Membrane behaviour in developing wheat (Triticum aestivum cv Priokskaya) embryos was studied in relation to the acquisition of desiccation tolerance, using spin probe techniques. Fresh embryos were able to develop into seedlings at day 15 after anthesis, but it took 18 d before fast-dried, isolated embryos could germinate. On the basis of membrane integrity measurements it was estimated that between 14 and 18 d after anthesis the proportion of embryonic cells surviving fast drying increased and the critical moisture content, to which embryonic cells could be dehydrated, decreased. Apparently, embryonic cells do not acquire the same level of desiccation tolerance simultaneously. Only when all cells had become desiccation tolerant was germination of air-dried embryos possible. Using 5-doxylstearic acid as the probe molecule, an approximately similar lipid,water interface ordering of membranes was observed in all hydrated embryos, irrespective of age. Dehydration had a dual effect on the lipid interface: further ordering of the major part of the interface and the appearance of additional, disturbed regions. The proportion of these regions correlated with the proportion of desiccation-tolerant cells. We propose that the membrane surface disturbance be caused by endogenous amphiphiles that partition from the cytoplasm into membranes during drying. The absence of such disturbed regions in dried, desiccation-sensitive embryos might reflect a lack of sufficient amphiphiles. The relevance of membrane surface disturbance for desiccation tolerance is discussed. [source]

Steering Two-Dimensional Molecular Growth via Dipolar Interaction

CHEMPHYSCHEM, Issue 12 2009
Stefan Kuck
Molecular networks: Chiral and metallized Salen molecules on a Cu(111) are investigated using local probe techniques (see figure). Whereas for the parent Co-Salen molecule no self-assembly is observed, in the metal,organic complexes the growth of large and regular molecular networks is achieved through a target-oriented synthetic design of the local electrostatic dipolar molecular fields. [source]