Mechanism of uptake of liquid hydrocarbons by microorganisms

Growth rates of Candida tropicalis were studied in two different fermentors. One was the ordinary shaker flask containing both the aqueous culture medium and liquid hydrocarbons. The other was a specially designed rotating disk-type fermentor containing only the aqueous culture medium, into which vapors of n-paraffins from C₆ to C₁₈ were supplied continuously without forming the liquid hydrocarbon phase. The specific growth rates of Candida tropicalis in the rotating disk fermentor, under such conditions that supply of hydrocarbon vapor was sufficient, showed good agreement with those in the shaker flask. This seems to indicate that hydrocarbon uptake by Candida tropicals by direct contact with liquid hydrocarbon is negligible.     

Choline, tetraalkylammonium and aminoalcohol as preserves of photosynthetic activities in isolated chloroplasts

Choline chloride, tetraalkylammonium chloride and aminoalcoholshow preservative effects on photosynthetic activities in spinachchloroplasts against deterioration after isolation, when oneof them is present in the medium used for isolating and storingchloroplasts within the concentration range between 0.1 and0.5 M. Any of these chemicals cause uncoupling to some extentif present in the reaction medium. (Received August 23, 1973; )     

Biological activity of some synthetic gibberellin glucosyl esters

Four gibberellin (GA₁, GA₃, GA₄ and GA₃₇) glucosyl esters were synthesized and found to be as active as their respective free acids in the rice seedling bioassay. The rapid hydrolysis of the glucosyl esters in rice seedlings was demonstrated by feeding experiments with glucosyl esters of [³H]GA₁ and [³H]GA₄.     

Defects in modification of cytoplasmic and mitochondrial transfer RNAs are caused by single nuclear mutations

Many nucleus-encoded mitochondrial enzymes differ in physical and chemical properties from analogous cytoplasmic enzymes, and it is therefore generally assumed that different genes encode analogous mitochondrial and cytoplasmic enzymes. However, our genetic studies show that for at least two different tRNA modifications, mutations in nuclear genes affect cytoplasmic as well as mitochondrial tRNAs. These studies utilize two yeast genes: TRM1 and TRM2. trm1 cells do not have the enzyme activity necessary to methylate guanosine to N²,N²-dimethylguanosine. trm2 is a new mutation that we describe here. trm2 cells are deficient in tRNA(uridine-5)methyltransferase, and hence contain tRNA lacking 5-methyluridine or ribothymidine. Other than lacking 5-methyluridine trm2 cells have no obvious physiological defect. These studies also show that the N²,N²-dimethylguanosine and 5-methyluridine modifications are not added to tRNA in an obligatory order, and that 5-methyluridine is not required for removal of intervening sequences from precursor tRNA.     

High resolution nuclear magnetic resonance study of base pairing in the native and denaturated conformers of transfer RNA Leu 3

The hydrogen-bonded protons of the base pairs in the native and denatured conformers of transfer RNA₃^Leu from bakers' yeast have been investigated by high resolution proton nuclear magnetic resonance at 220 MHz. Widespread changes in the nuclear magnetic resonance spectrum observed on going from the denatured to the native state indicate a change from 18 base pairs in the former conformer to 22 in the latter, corresponding to a gain of 3 to 5 G · C pairs, and a loss of 0 to 2 A · U pairs. These changes are compared with other data on the two conformers, affording further insight into their differences.     

Crystallization and preliminary crystallographic study of bacterial alpha-amylases

Crystallization of bacterial alpha-amylases has been achieved by the hanging-drop vapor diffusion method. The crystals of Bacillus licheniformis and B. licheniformis 584 amylases are isomorphous to each other. The crystals of B. licheniformis amylase belong to the tetragonal system, space group P4(2)2(1)2 with cell dimensions of a = 119.3 and c = 85.4 A. The asymmetric unit contains one molecule of amylase, with a volume per molecular mass, Vm, of 2.75 A3/Da. The crystals of B. licheniformis and B. licheniformis 584 amylases diffract beyond 2.5 A resolution and are suitable for X-ray diffraction analysis. The crystals of B. amyloliquefaciens amylase are orthorhombic, and have space group C222(1), with cell dimensions of a = 154, b = 298, and c = 90 A. The asymmetric unit contains three to five molecules. In the crystallization of B. licheniformis and B. licheniformis 584 amylases, the addition of EDTA was indispensable to obtain large single crystals, while it had an adverse effect on the crystallization of B. amyloliquefaciens amylase, producing a large amount of small crystals.     

Anticholinesterase Action of a Bromine Compound Isolated from Human Cerebrospinal Fluid

Abstract: L-l-Methylheptyl-γ-bromoacetoacetate was found to be a competitive inhibitor of the acetylcholines-terases (electric eel, K_i= 17.2 μM; rat brain, K_i= 32.6 μM) and of butyrylcholinesterase (horse serum, K_i= 1.2 μM). The L-isomer was a more effective inhibitor than the D-isomer. The bromine atom at the γ-position of the acidic moiety, the specific length of the carbon chain constituting the secondary alcohol moiety, and the presence of the ketone radical at the acidic moiety of the ester were necessary for the anticholinesterase action. 1-Methyl-heptyl-γ-bromoacetoacetate formed a complex with acetylcholinesterase or butyrylcholinesterase without hydrolysis of its own molecule.