Dynamic force spectroscopy to probe adhesion strength of living cells

We studied the mechanical strength of the adhesion of living cells to model membranes. The latter contained a RGD lipopeptide which is a high affinity binding site for a cell adhesion molecule (integrin alpha(V)beta(3)). Cells adhered specifically to the vesicles. We used micropipette aspiration for breaking this adhesion with well defined forces. Systematic variation of the rate of force application revealed pronounced kinetic effects. The dependence of the detachment forces on the loading rate was well described by a power law (exponent approximately 0.4), in agreement with recent theoretical work.     

2-(2-pyridyl-)ethyl esters A new carboxyl protecting group in peptide synthesis

2-(2-pyridyl-)ethyl esters are used as chemically inert, highly selective protecting groups that are removable under mild conditions via a two step procedure.     

Diffraction efficiency of volume holograms

In this paper we give an exact solution of the coupled differential equation system as developed by Kogelnik [1] for the case of symmetrical recording without neglecting the second differentials. This generalized solution is applicable to dielectric, absorption and so-called mixed volume holograms. It is shown that under special assumptions and approximations we get the same equations for the diffraction efficiency as derived by Kogelnik. In this first part of the paper transmission holograms are only investigated and in the second part we will give the solution for reflection holograms.     

Elektronen-Spinpolarisation bei der Photoionisation unpolarisierter Cäsiumatome mit zirkularpolarisiertem Licht

Photoelectrons ejected from cesium atoms by circularly polarized light of certain wavelengths are highly spinpolarized according to Fano's theory. Measurements of the spinpolarization of photoelectrons along the wavelength spectrum are reported. The highest degree of spinpolarization obtained experimentally is 100%. Our results reveal a small deviation from the theoretically predicted spinpolarization. Apart from giving information on the influence of spin-orbit interaction on the photoionization process, the Fano-effect turns out to be a simple and efficient method for producing polarized electron beams. Though not designed as a polarized electron source, our present apparatus yields a beam of 0.3·10^?10 Ampere with a polarization of 81 ± 3% when a broad unfiltered spectral band is irradiated.     

Elektronen-Spinpolarisation beim Photoeffekt mit zirkularpolarisiertem Licht an Alkalischichten

The spin polarization of photoelectrons emitted by alkali surfaces illuminated with monochromatic circularly polarized radiation has been observed. Maximum spin polarization of 4.5% is obtained with cesium at a wavelength of about 4500 Å. Both maximum spin polarization and the wavelength of the maximum decrease monotonically with decreasing atomic number. The spin polarization is zero within experimental errors, in the case of solid sodium and lithium.