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Biomedical subjects

V L Ratner

Publications and source records attributed to V L Ratner.

7 recordsLinked to original sources
PubMed1992

Immobilization of immunoglobulin on a quartz surface by BrCN without loss of antigen binding capability.

BrCN-activated quartz was used for the immobilization of monoclonal immunoglobulins. BrCN-activated quartz keeps its ability to quantitatively bind immunoglobulins for at least 8 h. The surface density of the immobilized immunoglobulins was 100 ng cm-2 and they were found to retain their ability to bind antigen in a molar ratio of 1:2 for not less than three months.

Antigen-Antibody Reactions↗
PubMed1984

Photoinduced isochromic rearrangement in rhodopsin.

Two tests have been used to detect and to study conformational rearrangements of cattle rhodopsin, occurring in the process of rhodopsin photolysis and resulting in no change in the visual pigment absorption spectrum. The first test concerns the ability of retinal to react with hydroxylamine. This ability occurs after photoisomerization of retinal with a time constant of 0.3 s at 20 degrees C reflecting this way a conformational transition demasking the retinal-opsin NC-bond. The other test takes advantage of the ability of rhodopsin to modulate the conductance of artificial lipid membranes. After a bleaching flash such a rhodopsin containing membrane shows a transient change in conductance. One of its characteristic time constants is that of NC-bond demasking. It shows that the "demasking" rearrangement is not an artefact due to presence of hydroxylamine and that it occurs in native rhodopsin. It has been shown that the "demasking" rearrangement is isochromic, not associated with known rhodopsin conformational transitions and, judging by its time characteristics, it may be of a functionally importance. The common scheme of rhodopsin photolysis has been modified to include a new conformational transition.

Animals↗
PubMed1976

The study of photoconduction of artificial lipid membranes incorporating rhodopsin. The simultaneous changes of membrane conduction and rhodopsin fluorescence.

The protein fluorescence changes of rod outer segment fragments during bleaching were studied. Flash caused a fluorescence intensity drop by about 6%. The time constant of this process was approximately 30 msec and coincided with the time constant of increasing the permeability of an artificial lipid membrane containing rhodopsin and of Metarhodopsin I decay. In the presence of hydroxylamine the fluorescence intensity increases after the initial drop. The second process time constant was about 300 msec and coincided with the conduction drop time constant of the artificial membrane containing rhodopsin. A new intermediate -- Metarhodopsin II1 is proposed. It has the Metarhodopsin II absorption spectrum, lives for about 300 msec at room temperature, does not react with hydroxylamine, and increases the permeability of a disk membrane.

Animals↗
PubMedDate not supplied

[Molecular mechanisms of receptor. II. Identification of the conformational transition of rhodopsin responsible for the leading edge of the photoresponse of artificial lipid membranes modified by fragments of the outer segment of rods].

Kinetic parameters of photoinduced permeability increase of artificial lipid membranes, modified by ROS fragments (tau20 degrees C = 20 mesec Ea = 33 +/- 2 kcal/mole) coincides with appropriate parameters of photoinduced protein fluorescence intensity decrease and ROS fragments absorption spectra change (metarhodopsin I leads leads to metarhodopsin II transition). Hydroxylamine accelerates this process, its rate is proportional to hydroxylamine at concentrations lower than 0.6 M.

Cell Membrane↗
PubMedDate not supplied

[Molecular mechanisms of receptor-potential generation by the photoreceptor. III. Conformational transition responsible for the tail end of the photoresponse of an artificial lipid membrane modified by fragments of the external segments of rods].

The kinetics of photoinduced changes of protein fluorescence of cattle visual pigment was studied in the presence of hydroxylamine. The rate constant of fluorescence increase is proportional to NH2OH concentration when it is less than 0.4 M. It reaches the maximal magnitude (3.3 +/- 1 sec-1) at higher hydroxylamine concentration. Fluorescence increase rate is controlled by the rate of chemical reaction of rhodopsin with hydroxylamine. It is limited by conformational rearrangement of opsin. This rearrangement does not induce absorbance spectrum change of visual pigment, but confers to it the capability to react with NH2OH and NaBH4. Kinetic parameters of this rearrangement (tau 20 degrees C approximately 300 msec, Eact = 19 +/- 2 kcal/mole) coincide with kinetic parameters of diminishing of the photoresponse of artificial lipid membrane modified by fragments of rod outer segments in the temperature range studied (+2 divided by +25 degrees C).

Animals↗