Synapses are critical components of an artificial neural network. Bacteriorhodopsin thin film can be used to construct compact, finely graded synapses for an optoelectronic neural network, based on its photochromic properties. Measurements show that these photochromic changes are blocked at low temperature. Thermal gating will allow synapses to be written on the film optically and then read wit...

Active proton transfer through membrane proteins is accomplished by shifts in the acidity of internal amino acids, prosthetic groups, and water molecules. The recently introduced step-scan attenuated total reflection Fourier-transform infrared (ATR/FT-IR) spectroscopy was employed to determine transient pKa changes of single amino acid side chains of the proton pump bacteriorhodopsin. The high ...

The complete denaturation and subsequent renaturation and reconstitution of a polytopic integral membrane protein are demonstrated. Delipidated bacteriorhodopsin (Huang, K.-S., Bayley, H., and Khorana, H. G. (1980) Proc. Natl. Acad. Sci. U. S. A. 77, 323-327) is completely denatured when transferred into 88% formic acid or anhydrous trifluoroacetic acid as shown by NMR and circular dichroism sp...

Chemical modification and electron spin resonance techniques were used to study the topography of carboxyl residues in purple membranes. The results showed that buried carboxyl groups are )ocated in hydrophobic protein domains at least 16 A from the membrane surface, and that the carboxyl-terminal tail is partially immobilized. Carboxyl groups on bacteriorhodopsin in purple membranes...

The retinal chromophore of bacteriorhodopsin is attached as a Schiff's base with the epsilon-amino group of a lysine residue. The site of attachment has now been investigated by the use of resonance Raman spectroscopy which has previously been shown to be sensitive to 15N isotope substitution at the Schiff's base. Bacteriorhodopsin samples obtained from bacteria grown in a medium containing eit...

The orientation of bacteriorhodopsin in the purple membrane of Halobacterium halobium has been studied by proteolytic degradation of purple membrane sheets, reconstituted vesicles, and whole cells, with the following results: (i) Bacteriorhodopsin in purple membrane sheets is cleaved at a single site by Pronase or trypsin; a polypeptide segment of about 15 amino acids is lost from the carboxyl ...

A simple model for the early events in visual pigments and bacteriorhodopsin is proposed. The model makes use of the likelihood that a negatively charged amino acid forms a salt bridge with the positively charged nitrogen of the retinylic chromophore. The photochemical event is a cis-trans isomerization in visual pigments and a trans-cis isomerization in bacteriorhodopsin, which in each case cl...

The primary processes of the photochemical cycle of light-adapted bacteriorhodopsin (BR) were studied by various experimental techniques with a time resolution of 5 x 10(-13) s. The following results were obtained. (a) After optical excitation the first excited singlet state S(1) of bacteriorhodopsin is observed via its fluorescence and absorption properties. The population of the excited singl...