The retinylidene chromophore mutant (Y185F) of bacteriorhodopsin, in which Tyr-185 is substituted by phenylalanine, is examined and compared with wild-type bacteriorhodopsin expressed in Escherichia coli; both were reinstituted similarly in vesicles. The Y185F mutant shows (at least) two distinct spectra at neutral pH. Upon light absorption, the blue species (which absorbs in the red) behaves a...

A new spectral species of the purple membrane of Halobacterium halobium has been observed below pH 3.2. The formation of this new species is temperature-dependent and is favoured by increasing temperature up to the physiological range of the organism. The rate of formation at pH 3.0 and 22 degrees C is 7.9 x 10-3s-1. The spectral distribution and temperature-dependence of the new species sugges...

The second order nonlinear polarizability and dipole moment changes upon light excitation of light-adapted bacteriorhodopsin (BR), dark-adapted BR, blue membrane, and acid purple membrane have been measured by second harmonic generation. Our results indicate that the dipole moment changes of the retinal chromophore, delta mu, are very sensitive to both the chromophore structure and protein/chro...

A method of direct lipid analysis by MALDI mass spectrometry in intact membranes, without prior extraction/separation steps, is described. The purple membrane isolated from the extremely halophilic archaeon Halobacterium salinarum was selected as model membrane. Lyophilized purple membranes were grinded with 9-aminoacridine as dry matrix and the powder mixture crushed in a mechanical die press ...

Transmembrane location of the retinal chromophore, either native or reduced in situ to a fluorescent derivative, of the purple membrane of Halobacterium halobium was investigated with fluorescence energy transfer techniques. Single sheets of purple membrane, either native or reduced with borohydride, were adsorbed on polylysine-coated glass; the orientation, whether the exposed surfaces were cy...

Bacteriorhodopsin, the only protein of the purple membranes of halobacteria [ 11, acts as a light-driven proton pump, translocating protons from the inner to the outer side of the plasma membrane [2]. The lightinduced asymmetric proton distribution contributes to the membrane potential by up to lo-40 mV [3]. Assuming a membrane thickness of 50 A, this potential difference corresponds to an elec...

BR* has been the subject of a wide variety of biophysical studies. Particular attractions are its ease of preparation in pure form, the availability of much structural information and its intrinsic chromophore, which facilitates a range of spectroscopic investigations (for review, see Stoeckenius et al., 1979). We have used BR to investigate various aspects of protein diffusion in membranes. In...

Indolicidin, a cationic antimicrobial tridecapeptide amide, is rich in proline and tryptophan residues. Its biological activity is intensively studied, but the details how indolicidin interacts with membranes are not fully understood yet. We report here an in situ atomic force microscopic study describing the effect of indolicidin on an artificial supported planar bilayer membrane of dipalmitoy...