Lack of repair of ultraviolet light damage in Mycoplasma gallisepticum

Molecules with single-stranded tails (rolling circles) were isolated as replicating intermediates in G4 progeny single-stranded DNA synthesis. Lysates from infected cells harvested late in infection during single-stranded DNA synthesis were not deproteinised but analysed directly in caesium chloride and propidium diiodide gradients. The gradient fractionated them on the basis of tail length. If the lysates were first deproteinised however, the tailed replicative intermediates banded as a peak at a density just greater than that of replicative form II DNA (RFII) and did not spread down the gradient. The origin of synthesis of the viral strand tail was mapped by electron microscopy as 55 to 60% away from the single EcoRI cleavage site. Termination molecules finishing a round of viral strand DNA synthesis have been identified as molecules consisting of a closed single-stranded DNA circle attached by a very small region to the parent double-stranded DNA circle.     

A triterpene acid constituent of Salvia lanata

The petrol extract of the whole plant (aerial parts and roots) of Salvia lanata yielded a new triterpene acid, 3-epi-ursolic acid.     

Total nitrogen and phosphorus balance sheet in a typic ustochrept soil under intensive cropping and fertilizer use

Summary Balance sheets were computed for total nitrogen and phosphorus in plough layer (0–15 cm) of a Typic Ustochrept soil under continuous multiple cropping for seven years (1971–72 to 1977–78) with a fixed rotation of pearl millet (Pennisetum typhoideum L.) wheat (Triticum aestivum L.) (Vigna sinensis Savi.) The treatments considered of soil test-based rates of N, P and K, applied both singly and in combinations together with farm yard manure, sulphur and zinc superimposed over optimum rates (100%) of NPK. Heavy, losses of N (762–899 kg ha⁻¹) occurred in the plots which received high rates of Nviz. 150% of recommended NPK and 100% NPK plus FYM. Application of N alone accelerated N losses whereas addition of P, PK, PKS to N minimised such losses. Enrichment of P (66 to 198 kg ha⁻¹) occurred in all phosphate-treated plots. A marginal net decrease (29–54 kg ha⁻¹) in P levels was observed in control and N alone treatments.     

Abnormally spliced messenger RNA in erythroid cells from patients with β+ thalassemia and monkey cells expressing a cloned β+-thalassemic gene

The reduced β-globin synthesis characterizing the β⁺ thalassemia phenotype has been shown to be caused by anomalous processing within the small Intervening sequence (IVS1) of the β-globin mRNA precursor. The β-globin gene from such patients contains a single base substitution within IVS1, located 22 bp from the 3′ junction between IVS1 and exon 2, creating an alternative splice site within IVS1 and resulting in retention of the 3′-terminal 19 bases of IVS1. We have identified this abnormally spliced mRNA in the reticulocyte RNA of two patients with β⁺ thalassemia, by S1 nuclease mapping and primer-extension analysis. Moreover, a cloned β⁺-thalassemic gene preferentially generated the anomalously spliced RNA when expressed In monkey kidney cells. The anomalously spliced RNA constituted approximately 80%–90%, and normal β RNA approximately 10%–20%, of the total β mRNA. In contrast, the small amount of β mRNA present in reticulocytes from such patients consisted predominantly of normal β mRNA. These results suggest that the reduced amount of normally functioning β mRNA present in such patients results from preferential processing at the alternative splice site, with subsequent Instability, reduced nuclear processing and/or inadequate cytoplasmic transport of the abnormal RNA species.     

Polymorphism and conformational flexibility of DNA: right and left handed duplexes

Left handed duplexes are shown to be in agreement with the X-ray intensity data of A-, B- and D-forms of DNA. The structures are stereochemically satisfactory because they were obtained following a stereochemical guideline derived from theory and single crystal structure data of nucleic acid components. The same stereochemical guideline also led to right handed duplexes for B- and D-forms of DNA which have stereochemically preferred conformation and hence are superior to those given by Arnott and coworkers^10,11.     

Sequence-dependent molecular conformation of polynucleotides: right and left-handed helices

Based upon a stereochemical guideline, two topologically distinct types of helicalduplexes have been deduced for a polynucleotide duplex with alternating purine pyrimidine sequence (PAPP): (a) right-handed uniform (RU) helix and (b) left-handed zig-zag (LZ) helix. Both structures have trinucleoside diphosphate as the basic unit wherein the purine pyrimidine fragment has a different conformation from the pyrimidine-purine fragment. Thus, RU and LZ helices represent two different classes of sequence-dependent molecular conformations for PAPP. The conformationalf eatures of an RU helix of PAPP in B-form and three LZ-helices for B-, D- and Z-forms are discussed.