Preparation of basal cell membranes for scanning probe microscopy.

Scanning probe microscopy has the potential for investigating membranes in a physiological environment. We prepared with a lysis-squirting protocol basal cell membranes, that are suitable for scanning probe microscopy. Investigations using atomic force microscopy under liquid revealed cellular filaments which correlated perfectly with fluorescently stained actin filaments. Globular structures with a diameter as little as 10 nm could be resolved by stripping cytoplasmic components from the membranes. Therefore, cytoplasmic sides of supported basal cell membranes prove useful to gain high resolution with scanning probe microscopy in studies of plasma membrane associated structures and processes under buffer solution.

Near-Field Surface-Enhanced Raman Imaging of Dye-Labeled DNA with 100-nm Resolution.

Raman chemical imaging on a scale of 100 nm is demonstrated for the first time. This is made possible by the combination of scanning near-field optical microscopy (SNOM or NSOM) and surface-enhanced Raman scattering (SERS), using brilliant cresyl blue (BCB)-labeled DNA as a sample. SERS substrates were produced by evaporating silver layers on Teflon nanospheres. The near-field SERS spectra were measured with an exposure time of 60 s and yielded good signal-to-noise ratios (25:1). The distinction between reflected light from the excitation laser and Raman scattered light allows the local sample reflectivity to be separated from the signal of the adsorbed DNA molecules. This is of general importance to correct for topographic coupling that often occurs in near-field optical imaging. The presented data show a lateral dependence of the Raman signals that points to special surface sites with particularly high SERS enhancement.

Dynamic self-pumped phase-conjugating mirror based on the bacteriorhodopsin variant D96N.

A self-pumped, phase-conjugating mirror (diameter 17 mm) is described that contains the bacteriorhodopsin variant D96N as the photoactive material. Resonant reflectivities up to 30% were obtained with an intensity of 25 mW/cm(2) at 647 nm. Rise times of less than 1 ms were observed with an intensity of 500 mW/cm(2) at 532 nm. Wave-front restoration with spatial light modulators as the dynamic input device was demonstrated, and the dependence of the reflectivity on the intensity and polarization was analyzed. The reflectivity shows no significant decrease with increasing angle between the pump and signal beams as a result of the high resolution of the bacteriorhodopsin films.