Nikolai V. Tkachenko

Excitation energy relaxation in chlorophyll a Langmuir-Blodgett multilayer films

Multilayer LB films of chlorophyll a in L-(alpha) -phosphatidylcholine dipalmitoyl matrix have been prepared in order to study excitation energy relaxation processes. Chlorophyll a layers were deposited on a plate previously covered with 10 layers of stearic acid and separated from each other by three layers of stearic acid, and finally covered by 8 layers of stearic acid to avoid interlayer interaction and to protect the sample. Films were deposited on quartz plates with ends cut at an angle of 45 degree(s) to use the full inner reflection of the probing beam. Fluorescence of the samples were studied in the time range from 10 ps to 10 ns and transient absorption in time range from 100 ns to 100 microsecond(s) . Results are discussed from the point of two types of chlorophyll arrangements on the films.

Time-resolved transient absorption and photoresponse studies of oriented bacteriorhodopsin in Langmuir-Blodgett films

In this work we have studied photon initiated processes of bacteriorhodopsin (BR) in Langmuir-Blodget (LB) monolayers and multilayers. As far as we know the present work is the first, where the photoresponse function and kinetics of BR is detected from a monolayer as well as the first report, where oriented monolayers have been used as a proton pump. The transient absorption spectra and the decay functions of multilayers were detected for films in water, in water vapor saturated air, and at room humidity. This had an influence on transient lifetimes. The method we have used to orient the bacteriorhodopsin molecules is based on the LB-technique and the fact that the protein orients during the coating process when a phospholipid binder is used. The photoelectric signals of the monolayers deposited by the different directions had opposite polarities. The amplitude due to five layers was five times as high as that due to a monolayer.