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Results for “protein aggregation”

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PubMed1977

Anaphylactoid reactions due to non-immune complex serum protein aggregates.

The infusion of aggregate-containing i.v. human gamma-globulin as well as human serum albumin can lead to severe anaphylactoid reactions with decrease in mean arterial pressure, increase in pulmonary artery pressure and decrease in cardiac output in unsensitized dogs, while the deaggregated solutions are well tolerated. During these anaphylactoid reactions, no significant changes in the serum complement activity of the dogs were observed. In clinical human serum albumin incompatibility, stimulation with albumin aggregates led to a high response in the lymphocyte culture, whereas deaggregated albumin had no stimulatory effect. By deaggregation of horse anti-human lymphocyte globulin prior to clinical administration, the compatibility of ALG therapy was improved.

Anaphylaxis↗
PubMed1979

Membrane damage caused by irradiation of fluorescent concanavalin A.

Visible light irradiation of fluoresceinated concanavalin A (f-Con A) bound to the outside of resealed erythrocyte membranes caused crosslinking of as much as 50% of the membrane proteins. Crosslinking was absent in controls in which equivalent amounts of f-Con A were added to the membranes but prevented from binding by the presence of 10 mM alpha-methylmannoside. The photodamage was not accompanied by a change in the membrane permeability barrier or membrane shape. Although fluorescein bleaching accompanies the formation of protein aggregates, the amount of aggregated protein is not simply a function of the number of fluoresceins bleached. The percentage of aggregated protein decreases when the same dose of light is given in a shorter time. Although certain antioxidants and free-radical scavengers had no detected effect on the crosslinking, reducing agents such as cysteamine and reduced glutathione either blocked or reversed the protein crosslinking. The mechanism of photoinduced oxidation and the implications of these results for fluorescence studies of cell membranes are discussed.

Concanavalin A↗
PubMed1977

Comparison of hydrophobic and strongly hydrophilic cleavable crosslinking reagents in intermolecular bond formation in aggregates of proteins or protein-RNA.

Most of the bifunctional reagents in protein chemistry possess a strongly hydrophobic backbone, derived from aliphatic or aromatic hydrocarbons. Even bifunctionals of more than 30 A in length of this sort form intramolecular bridges preferentially. In recent years, the intermolecular crosslinking of physiological protein aggregates has gained in importance. As shown in the crosslinking of hemoglobin with two sets of hydrophobic and strongly hydrophilic reagents, derived from azo dyes and tartaric acid, respectively, in this case it is not primarily the length of the bifunctional, but the hydrophilic structure that will enhance intermolecular crosslinking. Artificial dimers of native structure may be obtained. For the crosslinking of RNA to protein, we have synthesized a new reagent, 3-(2-bromo-3-oxobutane-1-sulphonyl)-propionic acid p-nitrophenyl ester. In a two step reaction, it is attached to adenine and cytosine moieties at pH 6 first, and to lysine side chains at pH 7,5. The reagent has been applied to the poly-A sequence of globin messenger RNA nucleoprotein.

Adenosine↗
PubMed1977

Characteristics of pulmonary surfactant in adult respiratory distress syndrome associated with trauma and shock.

Broncho-alveolar lavage fluid was obtained from a 24-year-old man who developed the adult respiratory distress syndrome one day after massive trauma and hemorrhagic shock. The lungs were available 3 days later when organ transplantation was performed. When the various fractions of the lavage material obtained by centrifugation, including the purified surface-active lipid-protein aggregates, were examined on the film balance, they revealed the usual minimal surface tension of 16 to 18 dyne per cm at 37 degrees C, but the compressibility of the films from the lungs with adult respiratory distress syndrome was 5 to 10 times higher than the normal range. This suggests that surfactant films in the adult respiratory distress syndrome are less responsive to stress, and that as a result, a loss of film elasticity may contribute to the abnormal pressure-volume relationships observed with the intact lung. Changes in the lipid-to-protein ratios of the purified lipid-protein aggregates were also found, as indicated by the recovery of 3 lipid-protein aggregates with different isopycnic densities from the lung with adult respiratory distress syndrome; only one major aggregate could be recovered from the lavages of normal lungs.

Adult↗
PubMed1975

The effect of ADP, calcium and some inhibitors of platelet aggregation on protein phosphokinases from human blood platelets.

A protein phosphokinase (ATP: protein phosphotransferase EC 2.7.1.37) which is stimulated by 3',5'-cyclic adenosine monophosphate (cyclic AMP) has been partially purified from both the cytoplasmic and membrane fractions of human platelets. The kinetics of both enzymes preparations are similar in respect to cyclic AMP, ATP, ADP and AMP. 5-10-minus 7 M cyclic AMP stimulated both preparations by approximately 100%. Both ADP and AMP at a concentration of 5-10-minus 5 M inhibited protein phosphokinase activity of the soluble and membrane preparation by between 50% and 70%. The response of the two enzyme preparations to calcium differed. 10 mM Ca-2+ inhibited soluble protein phosphokinase activity approximately 80% both in the presence and absence of 5-10 minus 7 M cyclic AMP whereas the same concentrations of Ca-2+ inhibited the membrane-bound enzyme by approximately 60% in the presence of 5-10-minus 7 M cyclic AMP and 40% in the absence of cyclic AMP. This observation may be of importance in understanding the mechanism of platelet aggregation.

Adenosine↗
PubMed1976

Electron spin resonance analysis of irreversible changes induced by calcium perturbation of erythrocyte membranes.

Introduction of calcium during hemolysis of erythrocytes causes irreversible membrane changes, including protein aggregation. These changes have been investigated by incorporation of one protein and three fatty acid spin label probes into washed membranes from erythrocytes hemolyzed with a range of Ca2+ concentrations. Electron spin resonance spectra of the lipid probes were analyzed for changes in the order parameters, isotropic coupling constants and mean angular deviations of the lipid hydrocarbon chains. The results generally indicated an increased freedom of mobility of the probes with increased Ca2+ concentration during hemolysis, but the response of each probe showed a different concentration dependence. The maximal response was obtained with the I(5, 10) probe. Variations in the responses were interpreted to reflect different modes of protein-lipid or protein-probe interactions arising from Ca2+ -induced membrane protein alterations. Spectra from membranes treated with the protein spin label showed an increased ratio of immobilized to mobile label with increased Ca2+ concentrations at hemolysis. This is consistent with the membrane protein aggregation phenomena previously observed. It is suggested that the increased protein-protein interactions formed as a result of calcium treatment permit an increased lipid mobility in the membrane regions monitored by the fatty acid probes.

Calcium↗
PubMed1977

[Experimental analysis of the complement-binding activity of gamma-globulin].

It was experimentally demonstrated that the anticomplimentary characteristics of gamma-globulin perparations was associated with disturbances of the colloid condition of the serum system and the absence of any stabilizing action of albumin and other serum proteins. It is also expressed as a result of a high complement-binding activity of protein aggregates. The anticomplementary characteristics of the nonaggregated part of protein in commercial preparations of gamma-globulin could be depressed by the addition of albumin or fresh serum; as to the anticomplementary characteristics of protein aggregates -- it remains unchanged. An intermolecular electrostatic interaction exists between albumin and gamma-globulin; it prevents sorption of the complement on Fc-fragment of IgG, whose destruction leads to the manifestation of the gamma-globulin complement-binding activity.

Blood Proteins↗
PubMed1975

Effects of denaturants on the sweet-tasting protein monellin.

Effects of the denaturants urea and guanidine-HCl on the sweet-tasting protein monellin have been studied. The pH at which monellin is initially treated with denaturant is an important factor in retention of sweetness, but the pH maintained during subsequent removal of denaturant by dialysis has no effect on activity. Recovery of sweetness of denaturant-treated monellin is favored when denaturation occurs at acid pH. Monellin treated with either 6 M guanidine-HCl or 8 M urea at acid pH retains all of its sweetness following removal of denaturant, but urea treatment at neutral pH leads to some irreversible loss of sweetness. Monellin precipitates from solution under some conditions during removal of denaturant by dialysis, and the precipitated protein is no longer sweet. Precipitation is least under acid conditions. Aggregated protein was demonstrated by gel filtration chromatography. The single sulfhydryl group of monellin was not demonstrable in the precipitated protein, having apparently become oxidized during denaturation and formation of the aggregated protein. The data support the hypothesis that the tertiary structure is important in the ability of monellin to elicit a sweet sensation.

Guanidines↗
PubMed1977

Assembly of tobacco mosaic virus in vitro: elongation of partially reconstituted RNA.

It was reported that the rate of elongation of partially reconstituted RNA, if prepared without centrifugation, showed dependency upon the state of protein aggregation like that found when free RNA was used as the nucleic acid source [Butler, P. J. G. (1974) J. Mol. Biol. 82, 333-341]. Butler concluded from this result that disks are the kinetically favored protein source for the elongation of the tobacco mosaic virus rod. We show that partially reconstituted RNA prepared without centrifugation always contains a significant amount of free RNA and conclude that the dependency of its elongation rate upon the state of protein aggregation is due to contamination of his partially reconstituted RNA preparation by free RNA. The elongation rate of partially reconstituted RNA, which had been pelleted and contained no free RNA, was found to be about the same regardless of the state of aggregation of the added protein.

Centrifugation, Density Gradient↗
PubMed1975

Circular dichroism and gel filtration behavior of subtilisin enzymes in concentrated solutions of guanidine hydrochloride.

The circular dichroism of diisopropylphosphorylsubtilisins Novo and Carlsberg in both the near- and farultraviolet spectral regions is unaltered by concentrations of guanidine hydrochloride as high as 4 M at neutral pH. At concentrations of guanidine hydrochloride greater than 4 M slow irreversible time-dependent changes, apparently obeying second-order kinetics, are evident in both the near- and far-ultraviolet circular dichroism of these enzymes. Gel filtration studies of inactivated subtilisin enzymes reveal the circular dichroism changes to be accompained by the appearance of aggregated protein material. The changes in circular dichroism and the production of associated subtilisin species are sensitive to protein concentration, denaturant concentrations, and pH. The circular dichroism of active subtilisins Novo and Carlsberg in guanidine hydrochloride exhibits irreversible changes similar to those observed for the inactivated subtilisins. Aggregated protein material is also formed initially in the presence of guanidine hydrochloride, but is rapidly autolyzed to low molecular weight fragments.

Binding Sites↗