[Disturbance of serum albumin conformation in patients with melancholic depression]. / Narushenie konformatsii al'bumina syvorotki u bol'nykh melankholicheskoi depressiei.

OBJECTIVE: Conformational protein changes may be an important component of the disturbance of molecular processes in the development of pathological process in the body. We studied conformations of albumin molecule in the blood of patients with depression using biophysical -nanotechnical approach. MATERIAL AND METHODS: We examined 19 patients with depression and 25 healthy controls. Properties of serum albumin were compared in patients with typical melancholic depression and controls using spectroscopy (subnanosecond range) with K-35 fluorescent probe. RESULTS AND CONCLUSION: The properties of albumin binding sites in patients before and after treatment differed from those in controls. The authors suggest that it points to the changes in albumin molecule conformation that may influence the functional state of the protein. It has been suggested that these changes may be considered as biomarkers of pharmacotherapeutic efficacy.

Effects of fatty acids on human serum albumin binding centers.

Albumin is a carrier of nonesterified long-chain fatty acids and many other ligands. The status of its binding centers was studied for various proportions of nonesterified long-chain fatty acids and albumin as exemplified by palmitic acid. The status of the binding center was tested by recording K-35 probe fluorescence decay in the subnanosecond band. This method showed the work of three types of centers. Palmitic acid enhanced binding activity of all centers, though to a different degree: if the palmitic acid/albumin proportion increased to 2-3, the probe binding to type 1 centers (located in the drug center I region) increased 1.5 times, while binding to type 3 centers increased more than 3-fold. Modification of these centers by nonesterified long-chain fatty acids was similar in the isolated human albumin preparation and in diluted blood serum. Hence, K-35 probe showed the actual status of various albumin centers, their binding capacity depending to a different measure on the fatty acid charge of albumin.

Dipolar relaxation in a lipid bilayer detected by a fluorescent probe, 4''-dimethylaminochalcone.

The dynamic behavior of polar molecules in egg phosphatidylcholine (PC) bilayers has been studied using a membrane fluorescent probe, 4''-dimethylaminochalcone (DMAC). Time and spectrally resolved fluorescence spectroscopy of DMAC incorporated in PC liposomes, as compared to studies of the probe in organic solvents, shows the existence of two independent populations, associated with different extent and speed of dipolar solvent relaxation. The first DMAC population represents approximately 69% of the fluorescence-emitting molecules, has a short fluorescence decay time (0.32 ns) and undergoes Stokes shift of 80 nm. The remaining 31% fraction of DMAC molecules has a decay time of 0.74 ns and undergoes a high (106 nm) Stokes shift. A fraction of the shift, ca. 24 nm for the first and 46 nm for the second population, is attributed to the fast (<0.1 ns) rotational relaxation of nearby dipolar molecules, which might be water. This two-state model accounts well for the detailed fluorescence properties of DMAC in egg PC, i.e. its broadened steady-state spectrum, its average fluorescence quantum yield and its complex wavelength-dependent fluorescence decays.

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.