Isomerization of carotenoids in photosynthesis and metabolic adaptation.

In nature, carotenoids are present as trans- and cis-isomers. Various physical and chemical factors like light, heat, acids, catalytic agents, and photosensitizers can contribute to the isomerization of carotenoids. Living organisms in the process of evolution have developed different mechanisms of adaptation to light stress, which can also involve isomeric forms of carotenoids. Particularly, light stress conditions can enhance isomerization processes. The purpose of this work is to review the recent studies on cis/trans isomerization of carotenoids as well as the role of carotenoid isomers for the light capture, energy transfer, photoprotection in light-harvesting complexes, and reaction centers of the photosynthetic apparatus of plants and other photosynthetic organisms. The review also presents recent studies of carotenoid isomers for the biomedical aspects, showing cis- and trans-isomers differ in bioavailability, antioxidant activity and biological activity, which can be used for therapeutic and prophylactic purposes.

Evolution of Proteins of the DNA Photolyase/Cryptochrome Family.

Proteins of the cryptochrome/DNA photolyase family (CPF) are phylogenetically related and structurally conserved flavoproteins that perform various functions. DNA photolyases repair DNA damage caused by UV-B radiation by exposure to UV-A/blue light simultaneously or subsequently. Cryptochromes are photoreceptor proteins regulating circadian clock, morphogenesis, phototaxis, and other responses to UV and blue light in various organisms. The review describes the structure and functions of CPF proteins, their evolutionary relationship, and possible functions of the CPF ancestor protein.

A theoretical study of 5,6,7,8-tetrahydro-6-hydroxymethylpterin: insight into intrinsic photoreceptor properties of 6-substituted tetrahydropterins.

Tetrahydropterins are essential biological cofactors, which play a crucial role in DNA and RNA syntheses, NO synthesis, hydroxylation of aromatic amino acids, etc. In the last few years, it has been shown that 6-substituted "unconjugated" tetrahydropterins can also play a photoreceptor chromophoric role in plants and cyanobacteria. However, the nature of the initial light signal transduction act in which H4pterins participate is unknown. Our quantum chemical calculations have shown the possibility of the fast internal conversion of excited states of H4pterins. The potential energy surface scan along the 1ππ* state shows no energy barrier leading to 1ππ*/S0 conical intersection, this explains the absence of fluorescence for H4pterins. Other trajectories of the internal conversion relate to the stretching vibrations of the N-H bonds of the pyrimidine ring for the Rydberg state. The presence of several trajectories of nonradiative quenching of the photoexcited singlet states provides the photostability of the molecule. It was demonstrated for the first time that the nature of the excited states of H4pterins is similar to the nature of the excited states of guanine.

Ultrastructure of hepatorenal cell populations in patients with HCV and HBV infection markers. Hepatorenal associations.

Hepatorenal cell populations were studied in patients with HCV and HBV infection markers and renal dysfunction. Pronounced mosaicism of ultrastructural changes in hepatocytes was associated with polymorphic cytopathic effects caused by RNA-genome hepatitis C virus and DNA-genome hepatitis B virus. The destructive component of the tubular compartment predominated in renal biopsy specimens from patients, with subsequent degeneration of the tubular epithelium associated with progressive interstitial fi brosis. Immunohistochemical studies detected HCV NS3Ag and HBcAg structural marker in the tubular epitheliocytes. An appreciable part of the structural and functional changes in the liver in patients with HCV and HBV infections was caused by the therapeutic complex, including programmed hemoperfusion.

Excited flavin and pterin coenzyme molecules in evolution.

Excited flavin and pterin molecules are active in intermolecular energy transfer and in photocatalysis of redox reactions resulting in conservation of free energy. Flavin-containing pigments produced in models of the prebiotic environment are capable of converting photon energy into the energy of phosphoanhydride bonds of ATP. However, during evolution photochemical reactions involving excited FMN or FAD molecules failed to become participants of bioenergy transfer systems, but they appear in enzymes responsible for repair of UV-damaged DNA (DNA photolyases) and also in receptors of blue and UV-A light regulating vital functions of organisms. The families of these photoproteins (DNA-photolyases and cryptochromes, LOV-domain- and BLUF-domain-containing proteins) are different in the structure and in mechanisms of the photoprocesses. The excited flavin molecules are involved in photochemical processes in reaction centers of these photoproteins. In DNA photolyases and cryptochromes the excitation energy on the reaction center flavin is supplied from an antenna molecule that is bound with the same polypeptide. The role of antenna is played by MTHF or by 8-HDF in some DNA photolyases, i.e. also by molecules with known coenzyme functions in biocatalysis. Differences in the structure of chromophore-binding domains suggest an independent origin of the photoprotein families. The analysis of structure and properties of coenzyme molecules reveals some specific features that were significant in evolution for their being selected as chromophores in these proteins.

[Photobiochemistry of folates: a photochemical reduction of folic acid].

Exposure of deaerated folic acid solutions containing an electron donor to UV radiation (310-390 nm, I = 0.4 W m(-2)) induced formation of dihydrofolic acid (DHFA), a photoexcitation which gave tetrahydrofolic acid (THFA). Only DHFA was formed in the presence of EDTA (E'o = +0.40 V), while the presence of stronger reductants-NADH (E'o = -0.32 V) and boron hydride (E'o = -0.48 V)-induced photoreduction to THFA. It was demonstrated that UV radiation had no effect on the THFA formylation, giving the coenzyme 5,10-methenyltetrahydrofolic acid and its transformation into another coenzyme, 5-formyltetrahydrofolic acid.

[Study of the photochemical properties of biopterin and its reduced forms].

UV-irradiation (270-390 nm, 20 min, I = 3.2 W m(-2)) of deaerated biopterin solution containing electron donor (Na2-EDTA) led to the formation of 7,8-dihydrobiopterin (H2BPT), which, when excited, underwent reduction to form 5,6,7,8-tetrahydrobiopterin (H4BPT). Protonated molecules of H4BPT were resistant to oxidation by O2 both in the "dark" incubated and UV-irradiated solutions at pH below 3.0. The rate of H4BPT oxidation dramatically increased at pH above 3.0, and, then, up to pH 10.0, it did not change, showing no dependence on UV-irradiation. At the initial stage (5 min) of H4BPT oxidation in neutral solution, UV-irradiation stimulated the accumulation of quinonoid 6,7-dihydrobiopterin (q-H2BPT) in addition to H2BPT. UV-irradiation of H2BPT induced its oxidation to biopterin and unidentified products.

[Immunogenetic analysis of pathomorphological forms and prognosis of chronic glomerulonephritis].

AIM: To ascertain whether HLA antigens are associated with morphological forms of chronic glomerulonephritis (CGN). MATERIAL AND METHODS: A retrospective analysis was made of HLA distribution in 122 patients with proliferative and nonproliferative forms of CGN at different stages of fibroplastic transformation and addition of the tubulointerstitial component. Testing of HLA antigens of class I was conducted by lymphocytotoxicity; specificity of DRBI genes was investigated by DNA polymerase chain reaction. The control group consisted of 341 healthy citizens of Novosibirsk. RESULTS: HLA-associations typical for each morphological CGN form, characteristic differences between them were established. CONCLUSION: The tables were plotted allowing estimation of probability of each of CGN morphological forms.

[Tolerance of 5,10-methenyltetrahydrofolate to ultraviolet radiation].

Aeration of aqueous solutions of 5,10-methenyltetrahydrofolic acid (MTHF) during exposure to ultraviolet irradiation (lambda 300-390 nm, 240 W/m2, 30 min) slowed down photolysis in comparison with deaerated solutions. The rate of photolysis in the presence of oxygen depended on buffer composition. It did not exceed 6% of the starting amount of MTHF. Photolysis of MTHF included opening of the imidazoline ring, dehydrogenation of the tetrahydropterin portion, and elimination of the p-aminobenzoylglutamate moiety. 6,7-Dimethyltetrahydropterin was used as a model compound to show that protonation of the reduced pterin heterocycle increased its tolerance to oxidation, and UV irradiation did not accelerate this process. The stabilizing effect of protonation of the pterin portion and the presence of the positively charged imidazoline moiety are assumed to hamper MTHF oxidation and photolysis. It is assumed that these factors favored the choice of MTHF molecules as photosensors in light-sensitive proteins in the course of evolution.

[Plasmic activity of phospholipid membranes in nephritis]. / Plazmennaia aktivnost' fosfolipidnykh membran pri nefritakh.

AIM: To study activity of plasmic phospholipid membranes (PPM) in patients with chronic nephritis (CN) as regards clinical-laboratory and morphological characteristics of the disease. MATERIAL AND METHODS: 10 patients with chronic mesangial glomerulonephritis (CMG) and 4 patients with chronic drug-induced tubulointerstitial nephritis were examined. All the patients had moderate arterial hypertension including 5 patients with CMG combined with nephrotic syndrome. 9 patients had elevated blood creatinine (up to 500 mcmol/l). Measurements were made of routine laboratory indices, blood coagulation and paracoagulation, Willebrand's factor (WF), aggregation time (AT), phospholipid activation of blood coagulation (FABC), morphological indices of activity and sclerosis. RESULTS: In spite of chronic latent intravascular blood coagulation, CN was characterized by apparent lowering of FABC which was more evident in CMG. There was a weak correlation between a FABC fall and the level of proteinuria, lipidemia, AT of platelets, indices of activity. Some parallels exist between creatininemia and activity of PPM. A close reverse relationship was found between FABC and WF, and a direct one between FABC and sclerosis index. CONCLUSION: Subnormal PPM activity in CN correlates with organic microthrombi formation and promotes the discussion of both mechanisms of FABC formation disturbances and possible ways of PPM consumption including enhanced diffusion into the mesangium in progressing nephrosclerosis.

[Effects of helium-neon laser on regeneration capacity of skeletal muscles of adult guinea pigs]. / Vozdeistvie gelii-neonovogo lazera na regeneratsionnuiu sposobnost' skeletnykh myshts vzroslykh morskikh svinok.

The muscle regeneration was studied in across-cut gastrocnemius muscle of adult guinea pigs. Both hind guinea pig legs were exposed to laser therapy (3-9 procedures for 5 min each) after operation. It was shown that laser therapy accelerated fibrin resorption and wound healing, decreased the muscle fiber degeneration, increased DNA and RNA synthesis in regenerating tissues, stimulated regenerative muscle fiber capacity. However, the regenerating muscle tissue did not connect both muscle stumps, and the narrow connective tissue scar was formed. Before it was shown that the same laser therapy conditions were more effective for rats. Probably, the stimulating effect of laser rays on regenerative tissue ability depends on species peculiarities of animals.

[Changes in the cuticle of a keratin fiber under the action of a low-temperature plasma]. / Izmeneniia v kutikule keratinovogo volokna pod deistviem nizkotemperaturnoi plazmy.

Oxygen and air low-temperature plasma treatment leads to significant changes in fibre cuticle cell membrane (skin flakes). Both lipids and proteins were destroyed. The processes of intensive lipid oxidation resulted from low-temperature plasma action. This factor seems to change critical surface tension, wetting and increasing penetration of dyes through the cuticle.

[The melanoidin-containing preparation MIGI-K from mussels and its characteristics]. / Melanoidinosoderzhashchii preparat MIGI-K iz midii i nekotorye ego kharakteristiki.

The physico-chemical properties of preparation MIGI-K from mussels are given. Some characteristics of melanoidin fractions of MIGI-K are presented, their similarity to standard melanoidin is revealed. The given data on biological activity of the preparation permit to consider MIGI-K as immunomodulator.