Investigation of structure and conformational changes of proteins by inductive - resonance energy transfer method

Intramolecular dynamics and conformational transition in proteins studied by biophysical labelling methods. Common and specific features of proteins from thermophylic micro-organisms

A general survey is carried out on the theoretical grounds for methods of spin, luminescence and Mössbauer labels, as well as their application in the study of protein intramolecular dynamics. When combined, these methods allow the protein dynamics to be investigated within a wide range of correlation times (tau c = 10(2) - 10(-10) s) and amplitudes. The purposeful application of the methods to various proteins at different temperatures (30-330 K), water content, substrate addition, etc., revealed a number of dynamical processes and conformational transitions in proteins. The experiments indicated correlations between the local segmental mobility of protein globules in a nanosecond temporal scale and biochemical reactions, such as long-distance electron transfer, hydrolysis and photoreactions. The biophysical labelling methods results were analysed together with the data on dynamics obtained using complementary physico-chemical methods and theoretical calculations. Special emphasis is given to recent results on proteins from thermophylic micro-organisms. The mechanisms of protein intramolecular dynamics and their role in the stability and functions of proteins and enzymes are discussed.

Determination of fluorescent probes localization in membranes by nonradiative energy transfer

One of the new methods of studying the structure and dimensions of biological membranes is based on the Förster's nonradiative energy transfer between special molecules, the so-called 'membrane fluorescent probes'. Further development of the approach is presented in this article. It consists of the combined use of the time-resolved and steady-state fluorescence data with subsequent computer simulation of the energy transfer in membranes. Anthracene as an energy donor, and 4-p-(dimethylamino)styryl-N-dodecylpyridinium (DSP-12) or 4-dimethylaminochalcone (DMC) as energy acceptors were bound with artificial phospholipid membrane vesicles ('liposomes'). The synchrotron radiation was used as an impulse source for the excitation light. The steady-state fluorescence data permit the area of possible probe localization in membranes to be distinguished, while the kinetic data allow them to be narrowed significantly. There is a good agreement between the obtained localization and our present-day knowledge of lipid bilayer structure. The accuracy of the method is ca. several Angströms.

Methods of physical labels--a combined approach to the study of microstructure and dynamics in biological systems

The physical principles of several new approaches to the investigation of biological and model systems are discussed, including versions of the spin label method based on relaxation measurements, and also the methods of triplet, Mössbauer, electron-scattering and radical-pair labels and probes. It is shown that all these methods make it possible to investigate molecular mobility of the medium with the correlation frequencies tau c-1 = 10(-3) -10(11) s-1, to measure the rate constants of collisions Ktr = 10(3) -10(10) M-1 s-1, to measure the distance between centers up to 100 A and finally, to evaluate the immersion depths of paramagnetic and chromophore centers in matrices up to 40 A. The combined approach is demonstrated with examples from studies of the structure of nitrogenase, the reaction centers of photosynthetic bacteria and sarcoplasmic reticulum membranes and from studies of the molecular dynamics of proteins and membranes.