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Specific antibodies against the tetra-acetylated form of H4 histone have been elicited in the rabbit. They do not cross-react with the non-, mono-, and di-acetylated forms of the histone molecule but a slight cross-reactivity with the tri-acetylated form of H4 histone is observed. Our studies also show that hyperacetylated H4 histones are recognized by the antibodies in intact nucleosomes.
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The absorption spectra of fluram, lysozyme, horse-radish peroxidase, and mixtures of lysozyme + fluram and peroxidase + fluram and the fluorescence and fluorescence excitation spectra of the mixtures in 0.05 M phosphate buffer with 1 per cent dioxane are determined. Due to formation of a protein-fluram compound, the absorption spectra of the mixtures are not algebraic sums of the components. From the fluorescence intensities the number of bonding sites is found 6 in both cases. The fluorescence spectrum of the peroxidase-fluram compound has maxima at 305, 350, 400, 450 nm due to peroxidase and at 480 nm originating from fluram. In mixtures of 10(-5) M lysozyme + 10(-4) M fluram, 3/4 of the excitation energy is transferred from lysozyme to fluram within the compound under 280 nm excitation. Under similar conditions 4/5 of the excitation energy is transferred from peroxidase to fluram.
Diffusion in multicomponent solutions containing proteoglycan is shown to result in the formation of coherent, fluid structures (known as dissipative structures) and induction of rapid polymer transport. These phenomena occur over a wide range of conditions (i.e. varying solute distribution, concentration, size, and chemical composition) which are envisaged to occur in the extracellular matrix of connective tissues. A concentration gradient of chondroitin sulfate in a proteoglycan matrix of uniform concentration yields dissipative structures which transport the proteoglycan up to 300-fold faster than its transport in the absence of the gradient component. Similar behavior was observed with other polysaccharide and monosaccharide concentration gradient components. Amplification of structure formation and rapid transport was achieved by 1) increasing the concentration of proteoglycan matrix, 2) increasing the magnitude of the concentration gradient, 3) decreasing the molecular weight of the gradient-forming component, and 4) decreasing the concentration gradient of proteoglycan in the matrix. Dissipative structure morphology exhibits a marked dependence on the initial component distribution. Non-specific, excluded volume interactions between the proteoglycan and the gradient component are believed to induce coupled diffusive transport of the proteoglycan. This leads to microscopic density inversions which nucleate and develop into macroscopic convective flows. These results are similar to those previously observed in ternary solutions of uncharged polymers (i.e. dextran/polyvinylpyrrolidone). We have demonstrated that dissipative structures may transport Micrococcus luteus cells as well as various solutes. Flows were also observed in proteoglycan solutions after localized addition of small amounts of either a proteolytic enzyme or hyaluronic acid. It is likely that the prerequisites for this spontaneous macroscopic self-organization, as manifested by the flow phenomenon, are present in the extracellular matrix of connective tissues.
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Cathepsin D was purified from porcine spleen to near homogeneity as determined by gel electrophoresis. The isolation scheme involved an acid precipitation of tissue extract, DEAE-cellulose and Sephadex G-200 chromatography, and isoelectric focusing. The end product represented about a 1000-fold purification and about a 10% recovery. The purified enzyme was the major isoenzyme, which represented 60% of cathepsin D present in porcine spleen. Two minor isoenzymes of cathepsin D were present in small amounts. The purified enzyme resembled porcine pepsin in molecular weight (35,000), amino acid composition, and inactivation by specific pepsin inactivators. The pH activity curve of the purified enzyme showed two optima near pH 3 and 4. The relative activities at these optimal pH values were affected by salt concentration. Experimental evidence indicated that the two-optima phenomenon is a property of a single enzyme species.
In the liver, the synthesis and the decarboxylation of phosphatidylserine (PS) are a part of a metabolic cycle forming choline from serine. Yet, in the brain, the methylation of PE to phosphatidylcholine is a minor path. Therefore it is possible that the decarboxylation of PS has different biological meanings in the two organs. In this paper, we follow the formation and the fate of radioactive PE; to this purpose, we load brain mitochondria with PS by incubating cell homogenates with labelled serine in base-exchange conditions. Then, we isolate mitochondria and incubate them for PS decarboxylase. We also subfractionate mitochondria to investigate the distribution of PE in inner and outer membranes. We conclude that newly formed PE slowly moves from its site of synthesis (inner mitochondrial membranes). Besides, it reacts better with TNBS and with FLA than the pre-existing PE. This suggests that the newly-synthesised lipid does not mix quickly with the rest of mitochondrial PE. Therefore, our data demonstrate that the fate of PE formed through the decarboxylation path in the brain is different from that reported for the liver where newly-formed PE is rapidly exported to outer mitochondrial membranes.
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Stationary and time-dependent fluorescence were measured for a donor/ acceptor (DA) pair bound to membrane proteins of bovine erythrocyte ghosts. The donor N-(p-(2-benzoxazolyl)phenyl)-maleimide (BMI) and the acceptor fluram bind to SH- and NH2-residues, respectively. The fluorescence spectra and the time-dependent emission were consistent with radiationless fluorescence energy transfer (RET). Band3 protein is the only membrane spanning protein with accessible SH-groups for the coupling of BMI molecules, and therefore only acceptor binding sites on the same band3 protein were counted by the RET measurements performed. A density of RET-effective acceptor binding sites c = 0.072 nm-2 was calculated on the basis of the two-dimensional Förster-kinetics.