Phytosterols from pressmud residue obtained after methanogenic fermentation

Summary Pressmud, a sugar factory waste, was fermented with methanogenic bacteria in an anaerobic fermenter for 40 days at 31±2°C. The pressmud residue obtained after fermentation was used as a source for the extraction of phytosterols. The anaerobic digestion degraded the organic matter and resulted in enrichment of phytosterols from 0.33% in the pressmud to 3.05% in the residue. Refluxing of 100 g of residue with benzene, petroleum ether, and ethanolic KOH (1051) yielded 8 g of soft cake, which on further fractionation with methylcyanide and isopropanol gave three fractions: 1) a crude mixture of phytosterols, 2) resin, and 3) undigested organic matter. The crude mixture of phytosterols after purification on neutral alumina followed by GLC analysis resulted in the separation of 68.7% of -sitosterol, 18.4% of stigmasterol and 12.9% of campesterol and brassicasterol together. Phytosterols were extracted more easily from fermented than from unfermented samples, because of biodegration of lipophilic compounds by the methanogenic bacteria.Acknowledgments. S.K.S. and J.C.S. are thankful to the authorities of the U.G.C., New Delhi, for the award of Teacher-fellowships. R.C.S., R.A.K.S. and D.K.M. are thankful to the authorities of the C.S.I.R., New Delhi, for providing R.A., S.R.F., and J.R.F., respectively. Reprint request to S.N.M.     

DNA synthesis provides the driving force to accelerate DNA unwinding by a helicase

Helicases are molecular motors that use the energy of nucleoside 5'-triphosphate (NTP) hydrolysis to translocate along a nucleic acid strand and catalyse reactions such as DNA unwinding. The ring-shaped helicase of bacteriophage T7 translocates along single-stranded (ss)DNA at a speed of 130 bases per second; however, T7 helicase slows down nearly tenfold when unwinding the strands of duplex DNA. Here, we report that T7 DNA polymerase, which is unable to catalyse strand displacement DNA synthesis by itself, can increase the unwinding rate to 114 base pairs per second, bringing the helicase up to similar speeds compared to its translocation along ssDNA. The helicase rate of stimulation depends upon the DNA synthesis rate and does not rely on specific interactions between T7 DNA polymerase and the carboxy-terminal residues of T7 helicase. Efficient duplex DNA synthesis is achieved only by the combined action of the helicase and polymerase. The strand displacement DNA synthesis by the DNA polymerase depends on the unwinding activity of the helicase, which provides ssDNA template. The rapid trapping of the ssDNA bases by the DNA synthesis activity of the polymerase in turn drives the helicase to move forward through duplex DNA at speeds similar to those observed along ssDNA.     

Charge-ordered ferromagnetic phase in La(0.5)Ca(0.5)MnO3

Mixed-valent manganites are noted for their unusual magnetic, electronic and structural phase transitions. For example, the La(1-x)Ca(x)MnO(3) phase diagram shows that below transition temperatures in the range 100-260 K, compounds with 0.2 < x < 0.5 are ferromagnetic and metallic, whereas those with 0.5 < x < 0.9 are antiferromagnetic and charge ordered. In a narrow region around x = 0.5, these totally dissimilar ground states are thought to coexist. It has been shown that charge order and charge disorder can coexist in the related compound, La(0.25)Pr(0.375)Ca(0.375)MnO(3). Here we present electron microscopy data for La(0.5)Ca(0.5)MnO(3) that shed light on the distribution of these coexisting phases, and uncover an additional, unexpected phase. Using electron holography and Fresnel imaging, we find micrometre-sized ferromagnetic regions spanning several grains coexisting with similar-sized regions with no local magnetization. Holography shows that the ferromagnetic regions have a local magnetization of 3.4 +/- 0.2 Bohr magnetons per Mn atom (the spin-aligned value is 3.5 micro (B) per Mn). We use electron diffraction and dark-field imaging to show that charge order exists in regions with no net magnetization and, surprisingly, can also occur in ferromagnetic regions.     

Synthetic substitute enzymes: Part III glutamic acid copolymers with lysozyme-like activity

Zusammenfassung Synthetische Copolymere aus Glutaminsäure und Phenylalanin zeigen Lysozymaktivität. Mit einem Produkt Phe₉₀Glu₁₀ wurde ca. ein Drittel der Lysozymaktivität erreicht.

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Communication No. 1415 from the Central Drug Research Institute. Part II — V. K.Naithani, K. B.Mathur and M. M.Dhar, Indian J. Biochem.6, 10 (1969).

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To whom enquiries may be made.     

Proteorhodopsin in the ubiquitous marine bacterium SAR11

Proteorhodopsins are light-dependent proton pumps that are predicted to have an important role in the ecology of the oceans by supplying energy for microbial metabolism. Proteorhodopsin genes were first discovered through the cloning and sequencing of large genomic DNA fragments from seawater. They were later shown to be widely distributed, phylogenetically diverse, and active in the oceans. Proteorhodopsin genes have not been found in cultured bacteria, and on the basis of environmental sequence data, it has not yet been possible to reconstruct the genomes of uncultured bacterial strains that have proteorhodopsin genes. Although the metabolic effect of proteorhodopsins is uncertain, they are thought to function in cells for which the primary mode of metabolism is the heterotrophic assimilation of dissolved organic carbon. Here we report that SAR11 strain HTCC1062 ('Pelagibacter ubique'), the first cultivated member of the extraordinarily abundant SAR11 clade, expresses a proteorhodopsin gene when cultured in autoclaved seawater and in its natural environment, the ocean. The Pelagibacter proteorhodopsin functions as a light-dependent proton pump. The gene is expressed by cells grown in either diurnal light or in darkness, and there is no difference between the growth rates or cell yields of cultures grown in light or darkness.     

Transition metals in an experimental tumour system

Summary In this report we present an analysis by atomic absorption spectrometry of some of the transition metals Fe, Zn, Cu, Mn, Co, and Ni in tissues and nuclear fractions in an experimental tumour system.Acknowledgments. The atomic absorption spectroscopic analysis was done at the Health Physics Division, Bhabha Atomic Research Centre, Bombay. The author are indebted to Dr S.D. Soman, Director, Health Physics Division for providing facilities for the said analysis.