Laboratory disruption of scaled astrophysical outflows by a misaligned magnetic field.

The shaping of astrophysical outflows into bright, dense, and collimated jets due to magnetic pressure is here investigated using laboratory experiments. Here we look at the impact on jet collimation of a misalignment between the outflow, as it stems from the source, and the magnetic field. For small misalignments, a magnetic nozzle forms and redirects the outflow in a collimated jet. For growing misalignments, this nozzle becomes increasingly asymmetric, disrupting jet formation. Our results thus suggest outflow/magnetic field misalignment to be a plausible key process regulating jet collimation in a variety of objects from our Sun's outflows to extragalatic jets. Furthermore, they provide a possible interpretation for the observed structuring of astrophysical jets. Jet modulation could be interpreted as the signature of changes over time in the outflow/ambient field angle, and the change in the direction of the jet could be the signature of changes in the direction of the ambient field.

[Structure of glyceraldehyde-3-phosphate dehydrogenase from rat muscle. Localization of arginine residues modified by 2,3-butanedione]. / Issledovanie struktury glitseral'degid-3-fosfatdegidrogenazy iz myshts krysy. Lokalizatsiia argininovykh ostatkov, modifitsiruemykh 2,3-butandionom.

Modification of rat skeletal muscle hologlyceraldehyde 3-phosphate dehydrogenase by [2,3-14C]butanedione was carried out. The conditions for obtaining preparative amounts of the modified protein and for the maintenance of the modification product stability at various steps of treatment were elaborated. Two radioactive peptides containing modified arginine residues were isolated from the trypsin hydrolysate of the enzyme modified by [2,3-14C] butanedione and oxidizied by performic acid, and their amino acid sequence was established. The data obtained suggest that the essential arginine residue occupies position 134 in the primary structure of the rat muscle enzyme.

Identification of an arginine residue important for catalytic activity in the primary structure of D-glyceraldehyde 3-phosphate dehydrogenase. Studies with the rat skeletal-muscle enzyme.

The reaction of holo-(D-glyceraldehyde 3-phosphate dehydrogenase) (EC 1.2.1.12) from rat skeletal muscle with [14C]butanedione in 0.05 M-NH4HCO3, pH 8.0, resulted in modification (*) of two arginine residues per subunit with a concomitant loss of catalytic activity. From a tryptic digest of the modified protein two radiolabelled peptides were isolated, with the following sequences: (1)Val-Ile-Ile-Asn-Ala-Pro-Thr-Ala-Asp-Ala(Glx,Met,Leu,Phe,Met)Gly-Val-Asx-Arg- Glx(His,Tyr)Ser-Lys and (2) Asp-Ala-Gly-Ala-Thr-Ile-Ala-Leu(Asx,Glx,Arg,Phe,Val)Lys. By comparison of the data with the known sequences of homologous enzymes, the localization of the modified residues was established. The first peptide was identified as corresponding to residues 116--139, the second to residues 293--306. Experimental evidence from this and previous studies suggests that arginine-134 is important for the catalytic activity of the rat muscle enzyme, being involved in structural rearrangements accompanying the organization of the active centre on the binding of coenzyme and substrate.

Structural studies on glyceraldehyde-phosphate dehydrogenase from rat skeletal muscle.

The NH2-terminal amino acid sequence of rat skeletal muscle glyceraldehydephosphate dehydrogenase (D-glyceraldehyde-3-phosphate : NAD+ oxidoreductase(physphorylating), EC 1.2.1.12) was determined to be Val-Lys-Val-Gly-Val-Asn-Gly-Phe-Gly-Arg-Ile-Gly-Arg-Leu-Val-Thr-Arg-Ala-Ala-Phe-Ser-Ser-(-)-(-)--Val-Asx-Ile-Val-Ala-Ile. The presence of Asn instead of Asp in position 6 differentiates this enzyme from other glyceraldehyde-3-phosphate dehydrogenases so far sequenced with the exception of the enzymes isolated from liver. The location of Asn in position 6 has been considered as a specific property of liver glyceraldehyde-3-phosphate dehydrogenase (Kulbe, K.D., Jackson, K.W. and Tang, J. (1975) Biochem. Biophys. Res. Commun. 67, 35--42); this suggestion is not sustained by the results of the present investigation. The amino acid composition of the rat skeletal muscle dehydrogenase demonstrates the unusually low histidine content of this enzyme as compared to other mammalian muscle glyceraldehyde-phosphate dehydrogenases.

[Structural studies on D-glyceraldehyde-3-phosphate dehydrogenase from rat skeletal muscle]. / Issledovanie struktury D-glitseral'degid-3-fosfatdegidrogenazy iz skeletnykh myshts krysy

The amino acid composition of glyceraldehyde-3-phosphate dehydrogenase isolated from rat skeletal muscle was determined. Tryptic peptide maps of the carboxymethylated protein were compared with those of the corresponding derivative of the rabbit muscle dehydrogenase. Evidence from the amino acid analysis, N-terminal amino acid and the position of the peptides in two-dimensional chromatography-electrophoresis suggests a high degree of homology between the two enzymes. However, the rat muscle glyceraldehyde-3-phosphate dehydrogenase is characterised by a markedly lower histidine content. Some differences are also revealed in the peptide maps of the rat and rabbit dehydrogenases. Four cysteine residues per subunit of rat apoenzyme may be carboxymethylated in the absence of denaturing agents (pH 8,4 75 min). Two of them are modified at pH8,0 within 30 min and are both found in the peptide, which has been demonstrated to contain the most reactive cysteine residue. This suggests cysteine residue N 153 to be the second in order of reactivity towards iodacetate. No difference in the accessibility of SH groups to iodacetic acid has been found between apoenzyme samples incubated in 0,15 M NaCl at 20 degrees and 4 degrees respectively. This indicates that enzyme inactivation caused by dissociation which occurs at low temperature brings about no measurable alterations in the SH group reactivity as compared to that observed at 20 degrees.

[Effect of succinic semialdehyde on nitrogen metabolism of animal brain tissue during hypoxia]. / Vliianie iantarnogo polual'degida na nekotorye storony azotistogo obmena tkani mozga zhivotnykh pri gipoksii

In examining the content of free ammonia, glutamine and some free amino acid s in the brain tissue of mice under normal conditions, in hypoxia and under the effect of succinic acidsemialdehyde, in hypoxia there was revealed a marked increase in comparison with the normal conditions) of the content of free ammonia, and alpha-alanine, a reduction of glutamine; there was also a slight elevation in the content of gamma aminobutyric acid and no changes in glutamic and asparagic acid content. In case of pretreatment with succinic acid semialdehyde the content of free ammonia, glutamine and alpha-alanine in hypoxia approached the normal value. One of the possible mechanisms of the antihypoxic effect of succinic acid semialdehyde was transformation of this compound as a results of which there occurred synthesis of glutamic acid and glutamine leading to detoxication of free ammonia accumulating in the brain tissue in hypoxia.