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J Clauwaert

Publications and source records attributed to J Clauwaert.

At least 37 records · Page 2Linked to original sources
PubMed1983

Pro-(carboxypeptidases A) from whole pig pancreas. Their mass, size, shape and solvation.

Sedimentation analysis and light-scattering measurements were made with the two forms of pig pancreas pro-(carboxypeptidase A), in order to determine some of their physical properties. The following values were found (the first value applies to the binary complex and the second one to the monomer). The A 1%/280.1 cm values were 19.9 +/- 0.3 and 16.3 +/- 0.3. The partial specific volumes v -0 were 0.707 +/- 0.016 cm3/g and 0.714 +/- 0.015 cm3/g. The sedimentation coefficients S 0/20,w were 4.90 +/- 0.15S and 3.75 +/- 0.15 S. The diffusion coefficients D 0/20,w were (5.8 +/- 0.1) X 10(-7) cm2/s and (6.95 +/- 0.15) X 10(-7) cm2/s. From these data the following values were calculated. Relative molecular masses Mr were 71 000 +/- 4000 and 46 000 +/- 3000. The frictional ratios f/fmin. were 1.37 +/- 0.06 and 1.31 +/- 0.07; assuming a value for the solvation of the molecules (delta = 0.5 g/g) the asymmetry values range from 3 to 5 for the binary complex and from 2 to 4 for the monomer. The Mr values found in the present work coincide with those found by means of polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate [Martínez, Avilés, SanSegundo & Cuchillo (1981) Biochem. J. 197, 141-147]. Therefore the low values obtained by those authors when using gel-filtration chromatography must be the result of the interaction of the zymogens with the gel matrix, as the asymmetry is too small to justify the large discrepancies found.

Animals↗
PubMed1983

Photon and fluorescence correlation spectroscopy and light scattering of eye-lens proteins at moderate concentrations.

The bovine eye-lens protein, alpha L-crystallin, has been studied with photon correlation spectroscopy to obtain the mutual diffusion coefficient, Dm, with fluorescence correlation spectroscopy to determine the tracer diffusion coefficient, DT, and with light scattering to get the isothermal osmotic compressibility (delta pi/delta c) P,T. The concentration dependence of Dm, DT, and (delta pi/delta c) P,T up to a volume fraction phi of the protein of 2.5 x 10(-2) has been interpreted on the basis of four different interaction potentials: (a) an extended hard-sphere potential; (b) a shielded Coulomb potential; (c) a shielded Coulomb interaction where the effect of counterions is included; (d) a simple mixed potential. The three parameters Dm, DT, and (delta pi/delta c) P,T have also been combined in the generalized Stokes-Einstein equation, Dm = [(delta pi/delta c)P,T . (1--phi) . (DT)]/(kappa B . T). Our results indicate that, in the case that photon correlation spectroscopy gives the mutual diffusion coefficient Dm, the applicability of the Stokes-Einstein equation can be questioned; or that, when one assumes the Stokes-Einstein equation to be valid, there is significant discrepancy between the result of photon correlation spectroscopy and Dm.

Animals↗
PubMed1982

The size and conformation of Artemia (brine-shrimp) ribosomal RNA free in solution.

The RNA was isolated from the large ribosomal subunits of the brine shrimp Artemia, and its conformation free in solution was studied by determining its sedimentation and diffusion coefficients. A comparison was made of the hydrodynamic radius of the ribosomal subunit and its isolated RNA in various buffers. The conformation of the rRNA free in solution is more extended than when it is incorporated in the ribosome. This is not only the case when the rRNA solution lacks bivalent and polyvalent cations, but even in the presence of Mg2+ and spermidine, which cause a tightening of RNA. Thus the ribosomal proteins should induce a further tightening of the rRNA during the assembly of the ribosome. In the discussion, the reported data on Escherichia coli rRNA species are presented in such a way that large discrepancies between various studied are revealed, and that they can be compared with the data reported here on the larger rRNA of an eukaryote.

Animals↗
PubMed1982

The structure of Artemia sp. haemoglobins-I. Isolation and characterization of oxygen binding domains obtained by limited tryptic digestion.

Limited tryptic digestion of the extracellular haemoglobins of the crustacea Artemia sp. result in series of discrete fragments which are multiples of 16,000 d. 2. These 16,000 d fragments, together with 50,000 d and 80,000 d fragments have similar amino acid composition and tryptic peptide maps as the intact globin chains. 3. The haem content of the 16,000 d fragments is the same as this of the intact pigment and they can bind oxygen in a non cooperative way. 4. These results strongly support that the 16,000 d fragments represent structural and functional units or domains from which the globin chains are built up.

Amino Acids↗
PubMed1982

Ribosome purification by isopycnic sedimentation in high density sucrose gradients.

The applicability has been investigated of a method for the isolation of cytoplasm (and mitochondrial) ribosomes of various eukaryotes. The procedure is based on centrifugation techniques and includes a sedimentation of the ribosomes in a sucrose gradient of very high density. It was found to be particularly useful with material which contains relatively few ribosomes.

Animals↗
PubMed1981

Physicochemical characterization of ribosomal particles from the eukaryote Artemia.

Cytoplasmic ribosomes and their large and small subunits have been isolated from the brine shrimp Artemia, and their basic physicochemical properties have been determined. From measurements of their ratio of absorbance at 260 and 280 nm, phosphorus and protein content, buoyant density in a CsCl gradient, and density increment, values have been derived for their RNA content (49, 52, and 43 +/- 2%, respectively), absorbance coefficient at 260 nm (12.1, 2.8, and 10.5, +/- 0.4 ml/mg, respectively), and partial specific volume (0.63, 0.62, and 0.65 +/- 0.002 ml/g, respectively). Analytical boundary sedimentation has yielded their standard sedimentation coefficient (81, 59, and 38, +/- 1 S, respectively). Photon correlation spectroscopy of laser light scattered from centrifuged solutions has yielded their translational diffusion coefficients (1.41 +/- 0.02, 1.61 +/- 0.03, and 1.80 +/- 0.04 X 10(-7) cm2/s, respectively). Combinations of these data have yielded values for their molecular weight (3.85 +/- 0.2, 2.45 +/- 0.2, and 1.45 +/- 0.1 X 10(6), respectively), for the total molecular weight of the free acid form of their RNA (1.9 +/- 0.1, 1.27 +/- 0.08, and 0.62 +/- 0.04 X 10(6), respectively) and of their proteins (2.0 +/- 0.1, 1.2 +/- 0.1, and 0.83 +/- 0.08 X 10(6), respectively), for their frictional coefficient ratio (1.54 +/- 0.04, 1.58 +/- 0.05, and 1.66 +/- 0.06, respectively), for their hydrodynamic and dry particle volume and radius, and for their hydrodynamic solvation. All the results are highly consistent. The various intact ribosomal particles of Artemia have nearly the same solvation (1.7 g/g); in this respect they resemble Escherichia coli ribosomal particles; this finding contrasts, however, with the few published data on eukaryotic ribosomes. This work strengthens the basis for a comparative study and for a more detailed elucidation of the structure of eukaryotic ribosomes.

Animals↗
PubMed1981

A cryptobiosis-specific 19S protein complex of Artemia salina gastrulae.

The postribosomal supernatant of Artemia salina cryptobiotic embryos contains a large quantity of a 19S protein complex. An amount of 3.6 mg/g of cysts is measured by immunoprecipitation with anti-(19S protein complex) antibody. The quantity of this complex decreases during further development to nauplius larvae to only 15% of the quantity present in cryptobiotic embryos. The complex was no longer detectable after 7 days of growth. The 27000-Mr protein subunit of the 19S complex is not synthesized by mRNA isolated from cryptobiotic embryos. The cryptobiosis-specific complex has Mr 573000 and 610000 as calculated from light-scattering and sedimentation-diffusion measurements respectively. The 19S homocomplex contains 20-23 27000-Mr proteins and has no function in the translation of homologous mRNA. From hydrodynamic data a hydration of 1.25 g of water/g of protein is calculated. The abundant presence of the 19S protein complex in cryptobiotic embryos and the absence of synthesis during development to nauplius larvae indicate a functional role during the cryptobiotic process in early embryogenesis. A role in maintaining the water content of the cytoplasm above a critical threshold during desiccation is suggested.

Animals↗
PubMed1981

Quasi-elastic light scattering of Artemia ribosomes sedimented in a CsCl density gradient.

It is impossible to measure the diffusion coefficient of macromolecules directly and accurately by quasi-elastic light scattering, when aggregates cannot be eliminated from the solutions to be investigated. Nevertheless, a simple method can be applied to overcome this problem in many cases. Aggregates are separated from the monomeric macromolecules by rate-zonal sedimentation in a CsCl density gradient in a transparent centrifugation tube; the monomers are then located by laser light scattering intensity measurements; photon correlation spectroscopy of the scattered ligh finally yields their diffusion coefficient. The viscosity of aqueous CsCl solutions at different temperatures and concentrations allows a good separation by centrifugation and a low uncertainty in the reduction of the measured diffusion coefficient to standard conditions. The application of the method to eukaryotic large ribosomal subunits is described as an example.

Animals↗
PubMed1980

High-pressure scattering study of Artemia salina ribosomes and polysomes.

The intensity has been measured of the light scattered by solutions of brine shrimp (Artemia salina) ribosomes and polysomes under hydrostatic pressures up to 2000 atm. This has given information about pressure-induced decreases in the means weight of the particles in solutions containing different concentrations of K+ and Mg2+ ions. The dissociation-association equilibrium reaction ribosome formed from large subunit + small subunit is accompanied by a volume change, --200 less than delta V less than --300 ml/mol; this delta V is discussed with relation to different models for the interaction between the ribosome subunits. The application of high pressures on polysome solutions caused also decreases of the light scattering; these were slower than in the case of ribosomes, and nonexponential. Only small decreases were found for ribosomes attached to messenger-RNA, which were obtained by incubation of polysomes with pancreatic RNAase. After fixation of the ribsomes and polysomes with formaldehyde, the light scattering remained constant with increasing pressures.

Animals↗
PubMed1978

Physical properties of Artemia salina ribosomes.

Eukaryotic ribosomes were isolated from the cryptobiotic embryos and from the further-developed free-swimming nauplii of the brine shrimp Artemia salina. Analytical boundary sedimentation and photon correlation spectroscopy yielded, respectively, the standard sedimentation and diffusion coefficients at infinite dilution, s degrees 20,w = 81 +/- 1 S and D degrees 20,w = (1.41 +/- 0.02) x 10(-7) cm2/s, for the unfixed and formaldehyde-fixed ribosomes from different developmental stages and for ribosomes attached to a messenger RNA fragment. Also, the density increment was determined, from which the partial specific volume was derived (0.63 +/- 0.01 cm3/g). Combination of the different measured parameters gives accurate values for the molecular weight (3.8 +/- 0.1) x 106 and for size and solvation parameters. These results are compared with their counterparts for the smaller ribosomes from the prokaryote Escherichia coli.

Animals↗