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Results for “Retinaldehyde”

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At least 721 records · Page 40Linked to original sources
PubMed1984

Light-dependent trans to cis isomerization of the retinal in halorhodopsin.

Flash-induced absorption changes in the near UV were determined for bacteriorhodopsin and halorhodopsin on a millisecond time scale. The difference spectrum obtained for bacteriorhodopsin was comparable to model difference spectra of tyrosine (aromatic OH deprotonated vs protonated), as found by others. The flash-induced difference spectrum for halorhodopsin, in contrast, resembled a model spectrum obtained for trans to 13-cis isomerization of retinal in bacteriorhodopsin. A model for chloride translocation by halorhodopsin is presented, in which the retinal isomerization moves positive charges, which in turn modulate the affinity of a site to chloride.

Bacteriorhodopsins↗
PubMed1987

A commentary on the inhibition by retinoids of leukotriene B4 production in leukocytes.

The order of potency of retinoids as inhibitors of A23187-induced production of leukotriene B4 (LTB4) in human polymorphonuclear leukocytes (PMN) was retinoic acid greater than retinal greater than retinol. However, the conversion of exogenous arachidonate (AA) to LTB4 by PMN homogenates was inhibited in the rank order retinol greater than retinal much greater than retinoic acid. The agreement between active concentrations of retinol in these two systems is consistent with this compound acting directly to inhibit AA metabolism: this is not so for the other retinoids. The order of potency for inhibition of phorbol dibutyrate (PDBu)-stimulated superoxide (O-2) production in HL60 granulocytes was retinol greater than retinoic acid much greater than retinal (inactive); neither retinol nor retinal displaced [3H]PDBu from HL60 cells. We conclude that inhibition of LTB4 production by retinoic acid and retinal is neither through inhibition of AA metabolism nor through inhibition of protein kinase C.

Arachidonic Acid↗
PubMed1987

Retinal Schiff base position relative to the surfaces of photoreceptor disk.

Surface-enhanced Raman spectra of native and photobleached bovine rod outer segment disks as well as inside-out (inverted) photoreceptor disks adsorbed on silver hydrosol have been analyzed. Surface-enhanced spectra of inverted disks and disk-monoclonal antibody complexes reveal the short-range mechanism of enhancement. The distance between retinal Schiff base and the cytoplasmic side of native disk has been shown to be 5-10 A.

Animals↗
PubMed1990

Rhodopsin reconstitution in bleached rod outer segment membranes in the presence of a retinal-binding protein from the honeybee.

The physiological role of a retinal-binding protein from honeybee is investigated. This protein, upon previous loading with all-trans retinal and subsequent irradiation with monochromatic light of wavelength 490 nm, is able to promote the reconstitution of rhodopsin when added to a suspension of opsin membranes from bleached bovine rod outer segments. In this respect this retinal-binding protein could have a role very similar to that postulated for the well-known cephalopod retinochrome, that serves to catalyze the formation in the presence of light of 11-cis retinal in photo-receptor cells and to provide it for the reconstitution of rhodopsin during the visual cycle.

Animals↗
PubMed1991

Identification of 11-cis and all-trans-retinal in the photoreceptive organelle of a flagellate green alga.

Isolation of intact photoreceptive organelles (eyespot apparatuses) involved in blue-light mediated photoresponses in a flagellate green alga (Spermatozopsis similis) allowed for the first time the identification of both 11-cis- and all-trans-retinal in a plant cell. Both isomers were identified by HPLC analysis in conjunction with UV spectra. Additionally, reconstitution of a distinct absorption band, centered around 540 nm, was achieved by addition of exogenous 9-cis-retinal to bleached, isolated eyespot apparatuses.

Carrier Proteins↗
PubMed1991

Between the ground- and M-state of bacteriorhodopsin the retinal transition dipole moment tilts out of the plane of the membrane by only 3 degrees.

The orientation of the transition dipole moments in the ground state and the M-intermediate of bacteriorhodopsin were determined by time-resolved and steady-state polarized absorption spectroscopy on samples of oriented immobilized purple membranes. The angle between the transition dipole moment and the membrane normal decreases from 66.8 +/- 0.5 degrees in the all-trans ground state to 64.1 +/- 0.8 degrees in the 13-cis M-state. The light-induced isomerization of the chromophore is thus accompanied by an orientational change of only about 3 degrees out of the plane of the membrane. The absorption anisotropy at 410 nm remains constant over more than 4 decades of time covering both the rise and decay of M. Conformational changes accompanying a sequential M1----M2 transition thus do not affect the chromophore orientation.

Bacteriorhodopsins↗
PubMed1992

Diversion of the sign of phototaxis in a Chlamydomonas reinhardtii mutant incorporated with retinal and its analogs.

The blind mutant FN68 of the unicellular flagellate green alga Chlamydomonas reinhardtii is negatively phototactic in the presence of the native chromophore all-trans retinal. In contrast, analog chromophores such as a ring-acyclic retinal and those in which trans/cis isomerization about the C11 = C12 double bond was blocked induced predominantly positive phototaxis in the same strain under the same experimental conditions. These observations can be interpreted by assuming that the negative and the positive phototaxis is mediated distinctively by two rhodopsin species which differ in their affinities with the exogenous chromophores. However, a more reasonable explanation, which requires fewer assumptions, is that the sign of phototaxis depends on a delay in intracellular photosignal transduction. This novel view was deduced directly from the widely accepted hypothesis [1980, Microbiol. Rev. 44, 572-630] on phototaxis mechanisms.

Animals↗
PubMed1993

Amino acid sequence surrounding the retinal-binding site in retinochrome of the squid, Todarodes pacificus.

Squid (Todarodes pacificus) retinochrome was reduced to N-retinyl protein with borane dimethylamine and cleaved by CNBr. The retinyl peptide was then isolated by chromatography while being monitored for absorbances at 215 and 330 nm, and the N-terminal amino acid sequence was determined to be Ser-Lys-Thr-Gly-X-Ala-Leu-Phe-Pro. This sequence was the same that we had observed at the 7th transmembrane domain of retinochrome whose structure was reported previously. During Edman degradation of the retinyl peptide, the yield of the PTH-lysine at the second cycle was lower than those of the other PTH-amino acids, proving that the lysine residue forms a Schiff's base with retinal (Lys-275 in retinochrome). The amino acid sequence surrounding the retinal-binding lysine in retinochrome greatly differed from those in a variety of known visual pigments. This fact would be associated with the difference in the photoisomerization of chromophore between retinochrome and rhodopsin. The protein structure of retinochrome is also compared with that of rhodopsin in Todarodes.

Amino Acid Sequence↗