BioSystems 59 (2001) 53–60 Photoinduced transformation of 14-F-bacteriorhodopsin gelatin films based on both wild type and D96N mutant A.B. Druzhko a, *, V.Yu. Shakhbazian a , R. Alvarez b , A.R. de Lera b , H.H. Weetall c a Institute of Theoretical and Experimental Biophysics Russian Academy of Sciences, Pushchino, Moscow region 142290 Russia b Department of Organic Chemistry, Uniersity de Vigo, Vigo, Spain c National Institute of Standards and Technology, Maryland, USA Received 11 September 2000; received in revised form 9 November 2000; accepted 12 November 2000 Abstract Spectral and kinetic transformations were studied in gelatin films made with 14-F wild type (WT) bacteri- orhodopsin (BR) and 14-F D96N mutant BR. Unlike the recent study of water suspensions of the same pigments, where a red shifted species at 660 nm was shown to form under the light in 14-F WT only, there are no drastic differences in photoinduced behavior between gelatin films based on 14-F WT and 14-F D96N. It is not observed any photoinduced formation of red shifted species at 660 nm for both types of films as it is observed for corresponding pigments in water suspension. The observed results are explained in a terms of relationship between the rates of two photoinduced processes that occur in suspensions and films of corresponding pigments. Kinetic characteristics of the photoinduced processes for the films with chemical additives suggest that there are no advantages in using 14-F D96N films when compared to films based on 14-F WT. © 2001 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Biomaterials; Bacteriorhodopsin derivatives; Fluorine analogs; Gelatin films; Optical spectroscopy www.elsevier.com/locate/biosystems 1. Introduction Over the last few decades the example of bacte- riorhodopsin (BR) has demonstrated that biologi- cal systems potentially can be used to solve material requirements in technical devices (Oester- helt et al., 1991; Birge, 1995). Indeed, pho- tochromic, electrochromic and non-linear-optical properties of BR allow the potential utilization of this naturally found molecular device (Druzhko et al., 1995; Hampp and Silber, 1996; Kolodner et al., 1997; Hampp, 2000). BR is a unique light-energy-transducing molecule, that is the photocycling protein in the purple membrane of the bacterium Halobacterium salinarium (Ebrey, 1992). It has a remarkable feature of forming a hexagonal crystalline array of BR molecule trimers. Seven transmembrane -helices are arranged in a circular manner with * Corresponding author. Tel.: +7-095-9239668; fax: +7- 0967-790553. E-mail address: druzhko@fluor.iteb.serpukhov.su (A.B. Druzhko). 0303-2647/01/$ - see front matter © 2001 Elsevier Science Ireland Ltd. All rights reserved. PII:S0303-2647(00)00144-1