Effect of different amino acids on the phosphatase system of an ectoparasite: Poecilobdella granulosa.

Inhibitory effect of different amino acids (L-phenylalanine, L-tryptophan, L-tyrosine, L-histidine-monochloride and L-arginine) on the phosphatase system of the brain, ventral nerve cord, stomach and intestine of the Indian medicinal leech Poecilobdella granulosa, was observed to be substrate, tissue, and inhibitor-specific. Most fascinating observation recorded was the activation of alkaline phosphatase of stomach and intestine by certain amino acids at low concentrations. This has been correlated with the sanguivorous habit of leeches.     

Molecular recognition of human eosinophil-derived neurotoxin (RNase 2) by placental ribonuclease inhibitor

Placental ribonuclease inhibitor (RI) binds diverse mammalian RNases with dissociation constants that are in the femtomolar range. Previous studies on the complexes of RI with RNase A and angiogenin revealed that RI utilises largely distinctive interactions to achieve high affinity for these two ligands. Here we report a 2.0 angstroms resolution crystal structure of RI in complex with a third ligand, eosinophil-derived neurotoxin (EDN), and a mutational analysis based on this structure. The RI-EDN interface is more extensive than those of the other two complexes and contains a considerably larger set of interactions. Few of the contacts present in the RI-angiogenin complex are replicated; the correspondence to the RI-RNase A complex is somewhat greater, but still modest. The energetic contributions of various interface regions differ strikingly from those in the earlier complexes. These findings provide insight into the structural basis for the unusual combination of high avidity and relaxed stringency that RI displays.     

DNA isolation from dry and fresh samples of polysaccharide-rich plants

DNA extraction is difficult in a variety of plants because of the presence of metabolites that interfere with DNA isolation procedures and downstream applications such as DNA restriction, amplification, and cloning. The chemotypic heterogeneity among species may not permit optimal DNA yield with a single protocol; thus, even closely related species may require different isolating protocols. Here we describe a modified procedure based on the hexadecyltrimethylammonium bromide (CTAB) method to isolate DNA from tissues containing high levels of polysaccharides. The procedure is applicable to both dry and fresh tissues and was tested on chickpea seeds, soybean, and wheat leaves. This method solved the problems of DNA degradation, contamination, and low yield due to binding and/or coprecipitation with starches and polysaccharides. The isolated DNA proved amenable to PCR amplification and restriction digestion.     

Interaction of surfactants with model and biological membranes. II. Effect of N-alkyl-N,N,N-trimethylammonium ions on phosphatidylcholine bilayers as studied by spin probe ESR

The interaction of N-alkyl-N,N,N-trimethylammonium (CnTMA, n = 6-18) salts (iodides and/or bromides) with model membranes prepared by hydration of egg yolk phosphatidylcholine (EYPC) over aqueous salt solutions has been studied by m-doxyl stearic acid (m-DSA, m = 12 and 16) spin probe method. In disoriented EYPC bilayers the CnTMA salts decrease the orientational order parameter S33 of m-DSA evaluated from the powder pattern ESR spectra. This effect is maximal for C6TMA. In oriented EYPC bilayers prepared by the parallel-beam sputtering method and hydrated over saturated NaCl solution the order parameter S33 calculated from the angular dependence of the nitrogen hyperfine splitting is decreased in the presence of C6TMA. The order parameter S11 obtained from the angular dependence of line positions indicates deviation of m-DSA motion from axial symmetry. C6TMA increases the probability of gauche conformations of the lipid chains by about 13-14%, and decreases the effective energy difference between the trans and gauche conformations by about 420-480 J/mol, at molar ratio of EYPC/C6TMA = 2:1. The angular dependence of linewidths is analysed by employing a theory of spin relaxation based on the strong collision model for molecular reorientations. The correlation time tau 0 of the reorientation of an axis orthogonal to the doxyl ring of 16-DSA is decreased in the presence of C6TMA, while that of 12-DSA is not influenced by it. The ratio of tau 2/tau 0 is increased in the presence of C6TMA for the both spin probes. The results are explained using the free-volume model of the CnTMA-EYPC membrane interaction.     

New alkaloids from Glycosmis mauritiana

Chemical investigation of the roots of G. mauritiana resulted in the isolation of two new alkaloids; 1-hydroxy-3-methoxy-2-(3-methylbut-2-enyl)-N-methylacridan-9-one (1) and 4,8-dimethoxy-3-(3-methylbut-2-enyl)-N-methyl-2-quinolone (6). The structures of these new bases have been established by chemical and spectroscopic methods and confirmed in the case of 6 by its synthesis. Interestingly, the formic acid-catalysed cyclisation of 1 gave the dealkylated product 3 along with the pyrano-[2, 3-a]-acridine (4).     

MORPHOLOGICAL AND EMBRYOLOGICAL STUDIES ON THE LEMNACEAE. I. THE FLORAL STRUCTURE AND GAMETOPHYTES OF LEMNA PAUCICOSTATA

Maheshwari, Satish C., and R. N. Kapil. (U. Delhi, Delhi, India.) Morphological and embryological studies on the Lemnaceae. I. The floral structure and gametophytes of Lemna paucicostata. Amer. Jour. Bot. 50(7): 677–686. Illus. 1963.—In Lemna paucicostata, a locally occurring member of the Lemnaceae, the plant body is represented by a frond which is devoid of lignified elements. The root shows a winged root sheath but does not have root hairs. There are no distinctive layers like the endodermis and xylem. The male archesporium is hypodermal and differentiates normally as in other angiosperms into parietal and sporogenous layers. The tapetum is single-layered and plasmodial. The partition walls of the anther are not derived by sterilization of the sporogenous cells as believed earlier. The microspore tetrads are isobilateral and decussate, the meiotic divisions being successive. The pollen grains are shed at the 3-celled stage. The ovary contains a single hemianatropous, bitegminal and crassinucellar ovule. The development of the embryo sac conforms to the Allium type.