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1.
Values in the literature for the quantum efficiency of the photochemical cycle of bacteriorhodopsin (bR) range from 0.25 to 0.79 and the sum of the quantum yields of the forward and back photoreactions [Formula: see text] has been proposed to be 1. In the present work, low intensity laser flashes (532 nm) and kinetic spectroscopy were used to determine the quantum efficiency of bR photoconversion, [UNK]bR, by measuring transient bleaching of bR at 610 nm in the millisecond time scale. Bovine rhodopsin (R) in 2% ammonyx LO was used as a photon counter. We find that the ratio of the quantum yields of bacteriorhodopsin photoconversion and bleaching of rhodopsin, [UNK]bR/[UNK]R, is 0.96 ± 0.04. Based on the quantum yield of the photobleaching of rhodopsin, 0.67, the quantum efficiency of bR photoconversion was determined to be 0.64 ± 0.04. The quantum yield of M formation was found to be 0.65 ± 0.06. From the transient bleaching of bR at 610 nm with a saturating laser flash (28 mJ/cm2) the maximum amount of bR cycling was estimated to be 47 ± 3%. From this value and the spectrum of K published in the literature, the ratio of the efficiencies of the forward and back light reactions, [UNK]1/[UNK]2, was estimated to be 0.67 ± 0.06 and so [UNK]2 ≈ 1 (0.94 ± 0.06). The sum of [UNK]1 + [UNK]2 ≈ 1.6. It was found that repeated high-intensity laser flashes (>20 mJ/cm2) irreversibly transformed bR into two stable photoproducts. One has its absorption maximum at 605 nm and the other has a well-resolved vibronic spectrum with maxima at 342, 359 (main peak), and 379 nm. The quantum yield of the formation of the photoproducts is ≈ 10-4. 相似文献
2.
G V Morozov L F Panchenko I P Anokhina A M Balashov N L Vekshina 《Biulleten' eksperimental'no? biologii i meditsiny》1980,90(11):566-568
Stereospecific binding of apomorphine to rat brain opiate receptors was shown by assaying the competition of 7,8(n)--3H--naloxone and D-ala2-tyrosyl-3,5-3H--enkephalin (5-D-leucine) for opiate receptor binding. EC-NaCl50, the concentration of apomorphine which inhibited 50% binding of the radioactive naloxone and D-ala2, D-leu5-enkephalin in the absence of NaCl were 20 and 42 microM, respectively. EC+NaCl 50, the concentration of apomorphine which inhibited 50% binding of the radioactive naloxone in the presence of 100 mM NaCl was 17 microM. From the ratio of EC+NaCl 50 to EC-NaCl the value of "sodium shift" of effective concentration can be calculated as 0.85. From the data obtained it is concluded that apomorphine, like naloxone, is a "pure" antagonist but it has much less affinity for enkephalin and opiate binding sites. The probable mechanisms of the pharmacological action of apomorphine are discussed. 相似文献
3.
Iu S Balashov 《Parazitologiia》1988,22(6):513-515
The structure of the surfaces of midgut and salivary glands in hungry and engorged females of Hyalomma asiaticum was studied by means of scanning electron microscopy. Preparations were fixed in glutaraldehyde osmium and then dehydrated by the critical point method and gold or platinum coating Different periods of fixation at room temperature or at 4 degrees C did not affect the condition of surface structures of gut and salivary glands. 相似文献
4.
Balashov IuS 《Parazitologiia》1999,33(3):210-222
During 60 years passed after the creation of the conception on natural focus of human infections by the academician E. N. Pavlovski? our knowledge on a role of blood-sucking insects and ticks in this phenomenon have been significantly enlarged. It has been recovered, that these arthropods serve not only as vectors of infection agents, but also as natural reservoirs and amplificators of these agents. In the process of the infection agent circulation in the natural focus there are several additional pathways of circulations without a participation of vertebrates. These pathways are as follows: the dispersion of infection agent in cases of simultaneous feeding of infected and "clean" ticks, and also the sexual, transovarial and transphase transmissions of pathogens. These mechanism of circulation are most often occur in the ixodid ticks, which can play the main role in supporting the infection agent in the focus. 相似文献
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7.
Balashov AM 《Uspekhi fiziologicheskikh nauk》2004,35(2):73-91
The literature data devoted to endogenous allosteric regulators of membrane bound receptors are summarized in the present review. The allosteric processes are classified to (i) cooperative interaction, (ii) nonspecific, (iii) functional, and (iv) specific regulations according to target topography in a receptor. The specific endogenous allosteric regulators are described for GABAA, NMDA, muscarinic, nicotinic, serotonin, and opioid receptors. Substances of different chemical structure (peptides, lipids, and polycyclics) are able both to activate or inhibit binding and function of respective receptors. Some pathological processes appear to depend on endogenous receptor modulators. The role of the regulators is speculated in terms of receptor homeostasis, in particular, counteraction of receptor tolerance and/or sensitisation during physiological pulsation in a ligand' level in synaptic cleft. 相似文献
8.
Mel'kumiants AM Balashov SA Kartamyshev SP 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2004,90(6):693-704
The effect of control of arterial diameter by the shear stress at the endothelium on noradrenaline-induced constriction of femoral vascular bed was investigated in anaesthetised cats. We compared noradrenaline-induced responses during the perfusion of the hindlimb at a constant blood flow and at a constant pressure as vasoconstriction is accompanied by an increase in wall shear stress only in the former case. We found that the same concentration of noradrenaline at a constant flow caused an augmentation of vascular resistance that was considerably smaller than at a constant pressure perfusion. This difference was almost eliminated after either removal of the endothelium or selective impairment of the endothelial sensitivity to the shear stress. These findings demonstrate that the control of arterial smooth muscle tone at a constant blood flow by shear stress at the endothelium does weaken noradrenaline-induced vasoconstriction. 相似文献
9.
Maeda A Herzfeld J Belenky M Needleman R Gennis RB Balashov SP Ebrey TG 《Biochemistry》2003,42(48):14122-14129
The L intermediate in the proton-motive photocycle of bacteriorhodopsin is the starting state for the first proton transfer, from the Schiff base to Asp85, in the formation of the M intermediate. Previous FTIR studies of L have identified unique vibration bands caused by the perturbation of several polar amino acid side chains and several internal water molecules located on the cytoplasmic side of the retinylidene chromophore. In the present FTIR study we describe spectral features of the L intermediate in D(2)O in the frequency region which includes the N-D stretching vibrations of the backbone amides. We show that a broad band in the 2220-2080 cm(-1) region appears in L. By use of appropriate (15)N labeling and mutants, the lower frequency side of this band in L is assigned to the amides of Lys216 and Gly220. These amides are coupled to each other, and interact with Thr46 and Val49 in helix B and Asp96 in helix C via weakly H-bonding water molecules that exhibit O-D stretching vibrations at 2621 and 2605 cm(-1). These water molecules are part of a hydrogen-bonded network characteristic of L which includes other water molecules located closer to the chromophore that exhibit an O-D stretching vibration at 2589 cm(-1). This structure, extending from the Schiff base to the internal proton donor Asp96, stabilizes L and affects the L-to-M transition. 相似文献
10.
The retinal protein phoborhodopsin (pR) (also called sensory rhodopsin II) is a specialized photoreceptor pigment used for negative phototaxis in halobacteria. Upon absorption of light, the pigment is transformed into a short-wavelength intermediate, M, that most likely is the signaling state (or its precursor) that triggers the motility response of the cell. The M intermediate thermally decays into the initial pigment, completing the cycle of transformations. In this study we attempted to determine whether M can be converted into the initial state by light. The M intermediate was trapped by the illumination of a water glycerol suspension of phoborhodopsin from Natronobacterium pharaonis called pharaonis phoborhodopsin (ppR) with yellow light (>450 nm) at -50 degrees C. The M intermediate absorbing at 390 nm is stable in the dark at this temperature. We found, however, that M is converted into the initial (or spectrally similar) state with an absorption maximum at 501 nm upon illumination with 380-nm light at -60 degrees C. The reversible transformations ppR if M are accompanied by the perturbation of tryptophan(s) and probably tyrosine(s) residues, as reflected by changes in the UV absorption band. Illumination at lower temperature (-160 degrees C) reveals two intermediates in the photoconversion of M, which we termed M' (or M'(404)) and ppR' (or ppR'(496)). A third photoproduct, ppR'(504), is formed at -110 degrees C during thermal transformations of M'(404) and ppR'(496). The absorption spectrum of M'(404) (maximum at 404 nm) consists of distinct vibronic bands at 362, 382, 404, and 420 nm that are different from the vibronic bands of M at 348, 368, 390, and 415 nm. ppR'(496) has an absorption band that is shifted to shorter wavelengths by 5 nm compared to the initial ppR, whereas ppR'(504) is redshifted by at least 3 nm. As in bacteriorhodopsin, photoexcitation of the M intermediate of ppR and, presumably, photoisomerization of the chromophore during the M --> M' transition result in a dramatic increase in the proton affinity of the Schiff base, followed by its reprotonation during the M' --> ppR' transition. Because the latter reaction occurs at very low temperature, the proton is most likely taken from the counterion (Asp(75)) rather than from the bulk. The phototransformation of M reveals a certain heterogeneity of the pigment, which probably reflects different populations of M or its photoproduct M'. Photoconversion of the M intermediate provides a possible pathway for photoreception in halobacteria and a useful tool for studying the mechanisms of signal transduction by phoborhodopsin (sensory rhodopsin II). 相似文献