Native High Molecular Weight Research Articles

Shear-induced structure in enzymatically-synthesized dextran solutions

A number of dextran derivatives and low molecular weight dextrans have found outlets in different fields such as fine chemistry and pharmaceutical industry, whereas only a few native (high molecular weight) dextrans have found applications. Thus, theoretical studies have scarcely concerned the rheological properties of native dextran solutions. Among the different synthesis processes, only the enzymaticin vitro synthesis produces a pure dextran, thereby allowing the rheological behavior of dextran solutions to be interpreted in terms of molecular considerations.

Properties of a phosphoprotein phosphatase from skeletal muscle and its regulation in diabetes.

Although the major phosphorylase phosphatase activity in skeletal muscle (1) and in liver (2) chromatographs with an apparent molecular weight of 250,000–260,000, only low molecular weight forms (30,000 to 35,000) have been purified to homogeneity (see review (3)). Since the low molecular weight phosphatases have not been demonstrated in tissues, it is important to isolate native high molecular weight phosphatases to investigate their subunit structure, substrate specificity, and mode of regulation.In skeletal muscle partially purified phosphatase preparations of molecular weight ranging from 30,000 to 140,000 have been reported (3–7) whereas in other tissues investigators have obtained highly purified high molecular weight multisubunit phosphoprotein phosphatases. Tsuiki and co-workers (8, 9) have isolated two high molecular weight phosphatases from rat liver (termed phosphatase IB and II). Phosphatase IB has an apparent molecular weight of 260,000 and consists of three polypeptide chains of 69,000, 58,0...

Partial purification from rat liver microsomes of three native protein phosphatases with activity towards HMG-CoA reductase.

A procedure for the isolation and partial purification of three hydroxymethylglutaryl coenzyme A reductase phosphatases in their native high molecular weight form from rat liver microsomes is described for the first time. Reductase phosphatase Ex (Mr 90,000), IM (Mr 75,000), and IIM (Mr 180,000) were purified 132-, 55-, and 98-fold, respectively. Treatment with 80% ethanol irreversibly inactivated the three enzymes contrary to what is found for cytosolic reductase phosphatases. The three microsomal reductase phosphatases differ among themselves and with respect to the cytosolic reductase phosphatases in molecular weight, response to inhibitors, thermal stability, and optimum pH. Indirect evidence that these three proteins are phosphatases includes their inhibition by inhibitors of phosphatase activity, such as KF, Pi, and PPi. Direct evidence includes their ability to release 32P from highly radioactive homogeneous 32P-labeled HMG-CoA reductase, this dephosphorylation being concomitant with activation of HMG-CoA reductase. The three phosphatases dephosphorylate 32P-labeled phosphorylase a, but only reductase phosphatase IIM shows glycogen synthase phosphatase activity.

Uptake of DNA by fragile mutants of Saccharomyces cerevisiae

When Saccharomyces cerevisiae SY15 rho° mutant cells grown in media stabilized with 10% sorbitol were suspended in 2% sorbitol solutions, 60-70% of the population did not lyse and became permeable to native high molecular weight DNA. Maximal incorporation of DNA to DNase resistant state was measured after 60 min of incubation in presence of 5 μg/ml DNA and 10 mM CaCl2. These results suggest that the fragile mutants might be tested as hosts for transformation of whole yeast cells.

Deoxyribonucleic acid dynamics from phosphorus-31 nuclear magnetic resonance.

31P NMR of native high molecular weight DNA shows that the phosphodiester backbone undergoes reorientation with a rotational correlation time of about 2 X 10(-6) s at 30 degrees C. This rate is consistent with the flexibility of the polymer and does not require the presence of internal phosphate motions. The line width of the phosphorus resonance of DNA is due to incompletely averaged 31P-1H dipolar couplings and 31P chemical shift anisotropy relaxation; high-power proton decoupling and magnetic field dependence experiments separate the two effects and allow the use of the line width for determination of the rotational correlation time. The line width is dependent on temperature, and an activation energy of 5-8 kcal/mol is calculated for the motion of DNA.

The activation and dissociation of a native high molecular weight form of rabbit skeletal muscle phosphorylase phosphatase by endogenous CA2+-dependent proteases.

The activation and dissociation of a native high molecular weight form of rabbit skeletal muscle phosphorylase phosphatase by endogenous CA2+-dependent proteases.

Origin of branches in native dextrans.

AbstractAccording to the proposed mechanism for the enzymatic formation of dextran, branches of different length are formed in a reaction between a so‐called acceptor dextran molecule and an active reaction complex; propagation of the dextran chain occurs by an insertion‐type polymer growth. To investigate this branching reaction, radioactive labeled acceptor dextran of relatively low molecular weight was added to a dextran synthesizing system and the native high molecular weight dextran separated by a fractionation method. From the specific radioactivity of the isolated native dextran, and assuming a molecular weight of 2.5 × 105, the average number of acceptor molecules incorporated into native dextran is calculated to be about unity, as predicted by the proposed mechanism. Analogous results have been obtained in the reaction of two different dextran sucrases from Leuconostoc mesenteroides B512F and B1307, respectively.