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Alzheimer's disease is the most prevalent neurodegenerative pathology. According to the amyloid cascade hypothesis, a key event of the Alzheimer's disease pathogenesis is a transition of the β-amyloid peptide (Аβ) from the monomeric form to the aggregated state. The mechanism of Аβ aggregation is intensively studied in vitro, by means of synthetic peptides and various physico-chemical methods allowing evaluation of size, molecular structure, and morphology of the formed aggregates. The paper reviews both the well-known and recently introduced physico-chemical methods for analysis of Аβ aggregation, including microscopу, optical and fluorescent methods, method of electron paramagnetic resonance, electrochemical and electrophoretic methods, gel-filtration, and mass spectrometric methods. Merits and drawbacks of the methods are discussed. The unique possibility to simultaneously observe Аβ monomers as well oligomers and large aggregates by means of atomic force microscopy or fluorescence correlation spectroscopy is emphasized. The high detection sensitivity of the latter method, monitoring the aggregation process in Аβ solutions at low peptide concentrations is underlined. Among mass spectrometric methods, the ion mobility mass spectrometry is marked out as a method enabling to obtain information about both the spectrum of Аβ oligomers and their structure. It is pointed out that the use of several methods giving the complementary data about Аβ aggregates is the best experimental approach to studying the process of b-amyloid peptide aggregation in vitro.Bolezn' Al'tsgeĭmera iavliaetsia naibolee rasprostranennym neĭrodegenerativnym zabolevaniem. Soglasno gipoteze “amiloidnogo kaskada”, kliuchevym sobytiem patogeneza bolezni Al'tsgeĭmera iavliaetsia perekhod b-amiloidnogo peptida (Ab) iz monomernogo sostoianiia v agregirovannoe. Mekhanizm agregatsii Ab intensivno izuchaetsia in vitro s ispol'zovaniem sinteticheskikh peptidov s pomoshch'iu fiziko-khimicheskikh metodov, pozvoliaiushchikh otsenivat' razmer, molekuliarnuiu strukturu i morfologiiu obrazuiushchikhsia agregatov. V obzore rassmotreny kak khorosho izvestnye, tak i nedavno poiavivshiesia fiziko-khimicheskie metody issledovaniia agregatsii Ab, vkliuchaia metody mikroskopii, opticheskie i fluorestsentnye metody, metod élektronnogo paramagnitnogo rezonansa, élektrokhimicheskiĭ i élektroforeticheskiĭ metody, gel'-fil'tratsiiu i mass-spektrometricheskie metody. Obsuzhdaiutsia dostoinstv a i nedostatki metodov. Otmechena unikal'naia vozmozhnost' odnovremenno nabliudat' kak monomery Ab, tak i ego oligomery i krupnye agregaty s pomoshch'iu metodov atomno-silovoĭ mikroskopii i fluorestsentnoĭ korreliatsionnoĭ spektroskopii, a takzhe vysokaia chuvstvitel'nost' poslednego, pozvoliaiushchaia sledit' za protsessom agregatsii v nizkokontsentrirovannykh rastvorakh Ab. Sredi mass-spektrometricheskikh metodov vydelen metod spektrometrii ionnoĭ podvizhnosti/mass-spektrometrii, kotoryĭ, nariadu s opredeleniem spektra oligomerov Ab, pozvoliaet poluchat' informatsiiu ob ikh strukture. Odnovremennoe ispol'zovanie neskol'kikh metodov, pozvoliaiushchikh poluchit' vzaimodopolniaiushchie dannye ob agregatakh Ab, iavliaetsia naibolee optimal'nym éksperimental'nym podkhodom k issledovaniiu protsessa agregatsii b-amiloidnykh peptidov in vitro.

Aptamers interacting selectively with the anion-binding exosites 1 and 2 of thrombin were merged into dimeric oligonucleotide constructs by means of a poly-(dT)-linker of 35 nucleotides (nt) in length. Complexes of thrombin with the aptamers and their hetero- and homodimeric constructs were measured using an optical biosensor Biacore-3000. The K D values obtained for the hetero- and homodimeric constructs were correspondingly 25–30- and 2–3-fold lower than those for the primary aptamers. Analysis of temperature dependencies of the K D values within the temperature interval of 10–40°C has shown that affinity increases with the temperature decrease. The values of the enthalpy change ΔH upon formation of complexes of thrombin with the aptamers and the heterodimeric construct were basically the same. The value of the entropy change ΔS upon complex formation of thrombin with the aptamer heterodimeric construct was 1.5–2-fold higher than the ΔS values for the complexes with the aptamers. The complex formation and dissociation rates increased with the elevation of temperature from 10 to 37°C. However, at both temperatures the dissociation rate for the complex of thrombin with the heterodimeric construct was evidently lower that for the complexes with the aptamers.

Using DNA aptamers selectively recognizing anion-binding exosites 1 and 2 of thrombin as a model, it has been demonstrated that their conjugation by a poly-(dT)-linker (ranging from 5 to 65 nucleotides (nt) in length) to produce aptamer heterodimeric constructs results into affinity enhancement. At the linker lengths ranged from 35 to 55 nt the apparent dissociation constants (KDapp) measured using the optical biosensor Biacore-3000 for complexes of thrombin with the heterodimeric constructs reached minimum values (KDapp) = 0.2–0.4 nM), which were approximately 30-fold less than for the complexes with the initial aptamers. A photoaptamer heterodimeric construct was designed connecting photoaptamer and aptamer sequences with the poly-(dT)-linker of 35 nt long. The photoaptamer used could form photo-induced cross-links with the exosite 2 of thrombin and the aptamer could bind to the exosite 1. The (KDapp value for the photoaptamer construct was approximately 40-fold less than that for the primary photoaptamer (5.3 and 190 nM, respectively). Upon exposure of the equimolar mixtures of thrombin with the photoaptamer construct to the UV radiation at 308 nm the equal yield of the crosslinked complexes was observed at concentrations, which were lower by two orders of magnitude than in the case of the primary photoaptamer. It was found that concurrently with crosslinking to thrombin a photo-induced inactivation of the photoaptamer occurs presumably due to formation of the intermolecular crosslinking.

Sorption properties of ammonium humates with respect to Fe(III), Cu(II), Al(III), Ni(II), Pb(II), and Zn(II) are studied. The effect of the metal ion concentration on the ammonium humate consumption is examined and the corresponding dependences are analyzed using regression equations. The IR spectra of brown coal humic acids, ammonium humates, as well as Fe, Cu, Ni, Zn, Pb, and Al humates are presented.

The fatty acid (FA) composition was determined in the blubber of 5 adult Baikal seals Phoca sibirica caught in July 2001, nine 1-mo old pups caught in April 2002, and 25 adults and fetuses from 3 of these, caught in October 2002, all along the SE shores of Lake Baikal, eastern Siberia. For comparison, FA in the blubber of ringed seals P. hispida, the closest marine relative of the Baikal seal, caught along the ice edge around Svalbard during 1999 and 2000 were also analyzed. The FA of the main prey of the Baikal and ringed seals, the endemic golomyanka Comephorus baikalensis and polar cod Boreogadus saida, respectively, were also studied. The same suite of FA was found in all samples. Saturated FA (SFA) with branched chains, all n6 polyunsaturated FA (PUFA) and 18:3n3 and 20:3n3 were more abundant in the blubber of the Lake Baikal seal and in the golomyanka than in the blubber of the marine ringed seal and marine fishes. In contrast, the relative levels of mono- unsaturated FAs (MUFA) with 20 and 22 carbons and polyunsaturated 20:5n3 were lower in the Baikal species than in the Svalbard species. The FA composition of the inner blubber was signifi- cantly different from the FA composition of the outer blubber in both species. Despite large differ- ences in FA composition between Baikal and ringed seal blubbers, vertical differences were mani- fested in the same FA: MUFA with 14, 16 and 18 carbons were present in higher relative abundance in the outer than in the inner layer. In both species all the other quantitatively important FA had lower or equal relative values in the outer layer. The FA composition of the seals' blubber differed from that of their main prey. The difference was, however, smaller between prey and inner blubber than between prey and outer blubber. The FA composition of the inner blubber of adults showed tempo- ral differences. Since the change from prey to blubber in relative concentration occurred in the same direction for all but 5 FA, the selection of FA during deposition in the inner blubber was similar for the 2 species, even though there was a large difference between the general FA composition of the freshwater and marine lipids. The FA composition in the blubber of adults, pups and fetuses differed.

Changes in sapropelite structure at room temperature in the course of modification with HNO3, HNO3-Ac2O, SO3-H2SO4, and H2SO4 were studied. The effect of chemical modification on the development of the specific surface area at thermolysis in the presence of acid (H3PO4) or base (KOH) activators was analyzed.

The interaction of the 16-mer synthetic peptide (Aβ16), which represents the metal-binding domain of the amyloid-β with DNA, was studied employing the surface plasmon resonance technique. It has been shown that Aβ16 binds to the duplex DNA in the presence of zinc ions and thus the metal-binding domain can serve as a zinc-dependent DNA-binding site of the amyloid-β. The interaction of Aβ16 with DNA most probably depends on oligomerization of the peptide and is dominated by interaction with phosphates of the DNA backbone.

Aliphatic carboxylic acids of normal structure were obtained in high yields by high-temperature alkaline (HTA) hydrolysis of three Siberian sapropelitic coals. The carboxylic acids and other oxygen-containing components of the hydrolysates were analysed by gas chromatography-mass spectrometry and the relevance of the results to the molecular structure of the coals was considered. The same types of oxygen-containing components were present in the alkaline hydrolysates of each coal. The major portion of these components was formed during the HTA hydrolysis.

The products of the fast-heating pyrolysis of two sapropelitic coals, from Taymalyr and Budagovo, in a helium flow were studied by differential mass-spectrometry (in the mass number range from 2 to 110). Equations describing the kinetics of the process under different conditions were produced. The mass-spectra of the sapropelitic coals are similar to those of switch oil evaporation products, which indicates the similarity of their chemical structures. The results obtained allowed the conclusion that the fundamental chemical structure of sapropelitic coals is a polycyclic hydrocarbon matrix of CH2 and CH groups with joinednalkane chains containing end-capping CH3 and COOH groups.

Normal aliphatic carboxylic acids and ketones obtained from the extraction of Taimylyr (Lensky basin, USSR) or Matagan (Irkutsky basin, USSR) sapropelitic coal with water and sodium hydroxide at elevated pressure and temperatures from 400 to 450 °C were investigated. The compositions of these compounds were studied by i.r. and n.m.r. spectroscopy, and combined g.c.-m.s.. The possible pathways of aliphatic carboxylic acids and ketones formation during the fossilization process are discussed.