Characteristics of the photoconversion of rhodopsin in the early stages of photolysis.

Low-temperature spectrophotometry was used to study the primary stages of rhodopsin photolysis. A digitonin extract of rhodopsin was irradiated at -155 degrees C with blue light of wavelength 436 nm. The stage of the bathorhodopsin --> lumirhodopsin conversion was accompanied by the simultaneous formation of several products. Formation of an intermediate product spectrally similar to the known "blue-shifted intermediate" (BSI) was demonstrated. It is suggested that the appearance of more than one intermediate product at each stage of photolysis reflects the existence of several conformational states of the rhodopsin molecule during its photoconversion.

[Peculiarities of rhodopsin photoconversion at the early stages of photolysis]. / Osobennosti fotoprevrashcheniia rodopsina na rannikh stadiiakh fotoliza.

The primary stages of rhodopsin photolysis were studied with the low temperature absorption spectroscopy technique. Digitonin extract of bovine rhodopsin was irradiated at -155 degrees C with blue light (436 nm). The following changes of the dark spectrum were recorded in the course of slow rise of the temperature in 1-3 degrees C steps. Simultaneous appearance of more than one spectral product was revealed throughout the batho- to lumirhodopsin transition. An intermediate product transformed along with bathorhodopsin to a next product known as a "blue-shifted intermediate", was observed. The data suggest that appearance of more than one intermediate at each stage of the rhodopsin photolysis reflects existence of multiple conformation states of the rhodopsin molecule in the course of its photoconversion.

Photosensitized light-induced damage of IRBP (interphotoreceptor retinoid-binding protein): effects on binding properties.

PURPOSE: To determine if IRBP (interphotoreceptor retinoid-binding protein) is damaged following irradiation by visible light in the presence of bound all-trans retinal. METHODS: Following irradiation of the IRBP-all-trans retinal complex, the retinal was removed and damage to IRBP measured as loss of titratable thiol groups, loss of tryptophan fluorescence, and changes in retinol-binding-induced fluorescence. RESULTS: IRBP irradiated by itself showed only minimal loss of tryptophan fluorescence; this loss was substantially increased by irradiation in the presence of all-trans retinal. Thiol groups and retinol-binding activity were also shown to be reduced. The damage to IRBP seemed to involve photosensitization by the all-trans retinal, which was in turn protected from bleaching by the IRBP. The binding affinity was shown to be reduced ten-fold following irradiation. CONCLUSION: In the eye, IRBP can stabilise vitamin A and debatably may be responsible for transport of different forms of vitamin A between the photoreceptor cells and pigment epithelium. If this is the case, it would play a key role in rhodopsin regeneration after bleaching. IRBP also appears to be necessary to sustain photoreceptor cells. Light was shown to cause photosensitized damage to IRBP, and thus might impair the regeneration process and photoreceptor viability.

[Photoreceptor membrane assymetric structure in separated phase state]. / Asimmetrichnaia struktura fotoretseptorno'i membrany v sostoianii fazovogo razdeleniia.

The structure of unbleached bovine retinal rod photoreceptor membranes isolated in ficoli density gradient has been studied by means of small-angle X-ray diffraction methods. Samples were prepared in the form of thin multilamellar films of photoreceptor membranes in phase-separated state induced by partial dehydration. Diffraction data were collected using diffractometer with linear position-sensitive detector. Phase signs of structure amplitude were determined by method [7] and membrane lamellar electron density distribution was calculated at 1, 7 nm resolution. The results obtained showed photoreceptor membranes isolated in ficoli density gradient to have asymmetric structure which differed from that of photoreceptor membranes isolated in sucrose density gradient [1]. The asymmetry observed may be accounted for different content of lipid L alpha and L beta phases in cytoplasmic and intradisk membrane layers. It may be assumed that ficoli helps to support membrane native structure.

[Retinal as a photo-damage sensitizer of retinal-containing retina proteins]. / Retinal' kak sensibilizator fotopovrezhdeniia retinal'-soderzhashchikh belkov setchatki glaza.

In vision light may act as an information bearer and a dangerous injury factor. The perfection of visual reception bases on using some "details" which promote free-radical photooxidized destruction. The samples of such "details" are retinal-chromophores of all visual pigments, polyunsaturated fatty acids of photoreceptor membrane phospholipids and thiol proteins. Reliable systems protecting structure of eyes against such damage have been formed in the course of evolution process. The review of details with photosensitizing properties of retinal and some other dangerous endogenous and exogenous sensitizers of retina and retinal pigment epithelium; with mechanisms of rhodopsin and interphotoreceptor retinal binding protein photodamage; with deterioration of structure and function of photoreceptor membrane, visual cells and retina, induced by photooxidation of proteins and lipids; with aggravation role of oxygen.

[Autoimmune mechanisms of eye involvement in congenital cataracts in children]. / Autoimmunnye mekhanizmy porazheniia glaz pri vrozhdennykh katarakt u detei.

A total of 112 children aged 6 months to 8 years with congenital cataracts (69 ones with bilateral and 43 with unilateral forms) and 34 mothers of these children were examined to estimate the activity of local and systemic autoimmune reactions to lenticular crystallines and retinal S antigen, differentiation between and diagnosis of congenital cataract pathogenetic forms. Lacrimal fluid antibodies were measured in 80 eyes with congenital cataracts and 29 ones with strabismus, blood serum antibodies in 72 children with cataracts, 20 without cataracts, 34 mothers of children with cataracts and 20 mothers of children without cataracts by the passive hemagglutination test (micromethod) with stable erythrocytic diagnostic agents. alpha, Bh, Bl, gamma crystallines and summary extracts of the cortical and nuclear layers were tested. The studies have demonstrated the significance of autoimmune reactions to lenticular crystallines in the pathogenesis of congenital cataracts and in involvement of the retina in the immunopathologic process.

[The mechanism of photodamage of eye structures. IV. Changes in the reactivity of crystalline SH-groups during UV irradiation]. / Mekhanizm fotopovrezhdeniia struktur glaza. IV. Izmenenie reaktsionnoi sposobnosti SH-grupp belkov khrustalika pri UV-obluchenii.

The kinetics of individual crystalline SH-group modification by DTNB were studied. According to the rates of their interaction with the modifier, the thiol groups in the native protein molecule can be classified as free, accessible, weakly modified and "masked" ones. Denaturation by the detergent (CTAB) caused an increase in the SH-group modification rate. In this case the SH-groups were modified as free and accessible ones. Illumination with UV-light resulted in a decrease in the number of SH-groups, opening of "masked" SH-groups in almost all crystallines except for alpha-crystalline, and essential changes in the SH-group modification rate.

[Mechanism of the photodamage of eye structures. Changes in the lens crystalline charges after ultraviolet irradiation]. / Mekhanizm fotopovrezhdeniia struktur glaza. Izmenenie zariadov kristallinov khrustalika pri ul'trafioletovom obluchenii.

UV photodamaging action on individual soluble proteins of the cattle eye crystalline lens were studied by electrofocusing. The most quantitative and qualitative changes were found in gamma-crystallines: a decrease of original polypeptide stripes and appearance of additional components in pI 5.1-6.4 region. The illumination of alpha- and beta H-crystallines resulted in qualitative changes. The appearance of aggregates with the molecular mass above 10(6)D were noticed in all the protein fractions, except beta H-crystalline.

Structural conversions of crystallins under senile cataract, dehydration and UV-irradiation studied by X-ray diffraction.

By means of X-ray diffraction analysis, structural conversions of crystallins in human lens were detected in senile cataract and upon artificial dehydration of lens tissue. In senile cataract certain characteristics of the native three-dimensional structure of gamma- and beta-crystallins are completely lost, whereas during dehydration of lens tissue a small but significant contraction of these protein molecules takes place. Upon artificial UV-irradiation of bovine crystallins destructive changes are observed, which are very similar to those in cataract.

[Mechanisms of photodestruction of the eye structure. Formation of polypeptide aggregates upon UV-irradiation of lens proteins]. / Mekhanizmy fotopovrezhdeniia struktur glaza. Obrazovanie agregatov polipeptidov pri UF-obluchenii belkov khrustalika.

UV-light injury of individual crystallins (water soluble proteins of the cattle eye crystalline lens) were studied by SDS PSSG technique. Photodamage resulted in oligomer formation. The appearance of high molecular aggregates with the molecular mass as large as 10(5) D were seen in all fractions of the crystalline.

[A structural study of crystallins in the normal and cataractous crystalline lens by x-ray diffraction]. / Strukturnoe issledovanie kristallinov v normal'nom i kataraktal'nom khrustalike metodom difraktsii rentgenovskikh luchei.

Nucleus of the normal and cataractous human lenses were studied by means of the X-ray diffraction method. The conformational changes, as it is shown, take place during cataract formation. The similar as in senile cataract, conformational changes of bovine lens crystallins were induced by UV irradiation.

[Rhodopsin photo-oxidation: oxygen consumption and spectrum of activity]. / Fotookislenie rodopsina: raskhod kisloroda i spektr deistviia.

The coincidence of action spectrum of SH-groups and lipid oxidation is shown in the photoreceptor photodamaging process. Dose dependence of the process is measured in the maximum of photooxidation (380 nm). Dose of 0.1 J/cm2 is the threshold of photodamaging of photoreceptor membrane. Oxygen consumption in photooxidation of rhodopsin SH-groups and lipids are determined.

[Photo-oxidative processes in eye structures. Protective function of the lens and shielding pigments]. / Fotookislitel'nye protsessy v strukturakh glaza. Zashchitnaia funktsiia khrustalika i ékraniruiushchikh pigmentov.

The results of visual cell photoreceptor membrane light damage mechanism research and some mechanisms of optical and chemical protection of eye structure from photo-sensibilized oxidation are reviewed.

[Aggravating action of oxygen in light injury to the retina in the white rat]. / Usugubliaiushchee deistvie kisloroda pri fotopovrezhdenii setchatki glaza beloi krysy.

Rhodopsin concentration and "a"-wave ERG decrease, depending on illumination in the range of 360-380 nm have been investigated in albino rats. The dose of 1.8 J/cm2 proved sufficient for a decrease of "a"-wave ERG by 70% and for the reduction in rhodopsin concentration by 80%. The substitution of the air for O2 (1 or 2.5 ata) resulted in a considerable increase of photodamage of the retina.

[The study of photo-induced rhodopsin aggregation in the photoreceptor membrane by electron paramagnetic resonance]. / Issledovanie svetoindutsirovannoi agregatsii rodopsina v fotoretseptornoi membrane metodom élektronnogo paramagnitnogo rezonansa.

The ESR measuring of UV-induced free radicals concentration limit has been used for studying rhodopsin aggregate state in the photoreceptor membrane.

[Retinal-sensitized photo-oxidation of rhodopsin]. / Sensibilizirovannoe retinalem fotookislenie rodopsina.

Kinetics of retinal photosensitized initiation of radicals of sulfhydryl groups of cysteine and rhodopsin is investigated by spin trapping. Photooxidation of both systems is the result of free radical mechanism. Photooxidation of SH-groups proceeds both with singlet oxygen participation and by direct interaction of photosensitizer with the substrate. The rate constants of these reactions are measured. The rate constant with oxygen participation (K0 = 1.1 X 10(9) M-1 S-1) is higher than the one without oxygen (K = 2.5 X 10(8) M-1 S-1) correspondingly. The lifetime of retinal triplet state in photoreceptor membrane is tau = 4 X 10(-6) s.

[Sulfhydryl group distribution along the axis of the rod outer segment in the frog]. / Raspredelenie sul'gidril'nykh grupp vdol' osi naruzhnogo segmenta palochki sechatki liagushki.

The existence of SH-group concentration axial gradient in frog's retinal rod outer segments has been shown. A diminution of SH-groups in the outer segment apical part points to a damage of the vision pigment during the life span of the rod disks.