Substrate-dependent inhibition of yeast enolase by fluoride

A possibly physiologically significant inhibition of yeast enolase by fluoride occurs in the absence of inorganic phosphate. The inhibition increases with time, is strongly dependent on fluoride concentration and requires substrate and “catalytic” Mg²⁺. The inhibition increases more slowly in the presence of product (phosphoenolpyruvate) than substrate (2-phosphoglycerate). The dependence on fluoride concentration and the spans of substrate analogue displacement titrations suggest the inhibition is produced by two moles of fluoride per active site.     

Origin of bombesin-like peptides in human fetal lung

Four different forms of bombesin-like immunoreactive peaks were detected in extracts of human fetal lung by the use of reversed-phase high performance liquid chromatography (HPLC). Peaks I, II, III and IV, (increasing retention time), were eluted using a 14-38% of acetonitrile gradient containing 0.1% trifluoroacetic acid (TFA). Peak II was the major material found in the extract of human fetal lung obtained at 16-20 weeks gestation. None of the four compounds contained in the eluted peaks had the same retention time as amphibian bombesin or porcine gastrin releasing peptide (GRP). On reversed-phase HPLC using two different solvent systems TFA or heptafluorobutyric acid (HFBA) as a hydrophobic counter ion, and in gel filtration chromatography, the chromatographic behavior of the main peak (peak II) was the same as that of the carboxyl terminal fragments of GRP, GRP18-27 or GRP19-27. This suggested that the peptide(s) in peak II resembled in composition the carboxy terminal 9 or 10 amino acids of porcine GRP. Following tryptic digestion the material in peak IV was converted to the more polar compound present in peak II. Two other peptide peaks were eluted close to peak II and these were presumed to be a modification of this main peak. One of the possible biosynthetic steps in the formation of bombesin-like peptides in human fetal lung could be a tryptic conversion of a less polar peptide to a more polar form (peak IV to II).     

Allogibberic acid: An inhibitor of flowering in Lemna perpusilla

Allogibberic acid (I) has been identified as the compound responsible for the inhibition of flowering, increase in frond multiplication rate and decrease in frond size produced in Lemna perpusilla 6746 by autoclaved, unbuffered aqueous solutions of gibberellic acid (VII). 13-Deoxyallogibberic acid (IV), a product of autoclaving aq. GA₇ (VIII) solutions, also inhibits flowering in L. perpusilla and is about 10 times more active than allogibberic acid.     

The effect of buffers and chelators on the reaction of luminol with Fenton's reagent near neutral pH

The chemiluminescence of the system luminol +Fe²⁺ + H₂O₂ was measured in aqueous buffer at pH 7.2. In veronal (5,5-diethybarbiturate) buffer, the luminescence is strongly quenched by ethanol and mannitol, but only weakly by t-butanol, benzoate and superoxide dismutase (SOD); complexing Fe²⁺ with 1,10-phenanthroline or 2,2′-dipyridyl causes a decrease of light production that can be partially obviated by the simultaneous addition of SOD. In phosphate buffer, the luminescence is higher than in veronal and it is efficiently quenched by all four OH · quenchers and by SOD. In Tris buffer, no light production is observed as long as the Fe²⁺ is not complexed. When Fe²⁺ is complexed by pyrophosphate or phytate, there is a strong chemiluminescence in all three buffers, which is quenched by all four OH · quenchers and by SOD. When Fe²⁺ is complexed by EDTA or DTPA, very little luminescence is observed. The luminol analogue phthalhydrazide, which was suggested by Merényi and Lind as a reliable OH · detector, can replace luminol only in phosphate buffer, and thus turns out to be very specific indeed for free OH ·.     

Sequence of an operon containing a novel δ-endotoxin gene from Bacillus thuringiensis

An insect larval toxin designated CryII is produced by several subspecies of Bacillus thuringiensis and differs from the other major delta-endotoxins in these bacteria in its size, toxicity profile and presence as part of an operon with three open reading frames (ORF). Such an operon from a novel B. thuringiensis isolate has been cloned and differs from one previously characterized in the following ways: (a) the size and number of amino acid repeats in one of the ORFs; (b) the smaller size of the CryII protoxin and the presence of a unique 110-kDa CryII-related antigen; and (c) high larvicidal activity for a particular Lepidopteran but low activity for a Dipteran. Various subclones of this operon were introduced into a plasmid-free B. thuringiensis strain and only the cryII gene was found to be necessary for protoxin accumulation.     

Strategies for signal amplification in nucleic acid detection

Many aspects of molecular genetics necessitate the detection of nucleic acid sequences. Current approaches involving target amplification (in situ PCR, Primed in situ Labeling, Self-Sustained Sequence Replication, Strand Displacement Amplification), probe amplification (Ligase Chain Reaction, Padlock Probes, Rolling Circle Amplification) and signal amplification (Tyramide Signal Amplification, Branched DNA Amplification) are summarized in the present review, together with their advantages and limitations.