A gas chromatographic method for the quantitative detemination of hexuronic acids in alginic acid

A method has been developed for the quantitative determination of the relative proportions of d-mannuronic and l-guluronic acids in alginic acid. To obtain homogeneous reaction conditions the viscosity of the alginic acid sample was first decreased by limited hydrolysis with mineral acid. The carboxyl groups were then esterified by reaction with 1-ethyl-3-[3-(dimethylamino)propyl]-carbodiimide, and reduced with sodium borohydride. The resulting hexosans were converted by acid hydrolysis to d-mannose and an equilibrium mixture of l-gulose and 1,6-anhydro-l-gulose. These were treated with sodium borohydride; the 1,6-anhydro-l-gulose was not reduced whereas d-mannose and l-gulose were converted to d-mannitol and d-glucitol. The hexitols were estimated by gas-liquid chromatography as the n-butane boronic acid esters, and the relative proportions of the uronic acids in the alginic acid were calculated by taking into account the equilibrium ratio of l-gulose and 1,6-anhydro-l-gulose. The method can be used to analyze as little as 2 mg of alginic acid.     

Heat shock proteins, molecular chaperones and the prion encephalopathies

No Abstract Available     

Ion transport by lasalocid A across red-blood-cell membranes. A multinuclear NMR study

Na+ and K+ fluxes mediated by lasalocid A across erythrocyte membranes have been determined from 23Na-NMR peak areas and chemical shifts, respectively. In similar experiments, Cl- transport has been monitored by NMR signal intensities. Taking into account the external pH variations, the results are readily explainable in terms of charge-balance conservation. The effect of disodium 4,4'-diisothiocyanostilbene-2,2'-disulfonate, an anion-exchange inhibitor, has also been studied.     

Induced Resistance to the Designer Proline-rich Antimicrobial Peptide A3-APO does not Involve Changes in the Intracellular Target DnaK

The designer proline-rich antimicrobial peptide A3-APO and its Chex1-Arg20 single chain in vivo metabolite were studied for their ability to induce bacterial resistance upon repeated incubation of Escherichia coli and Klebsiella pneumoniae strains in sublethal concentrations. While no resistant E. coli phenotype emerged to either peptides, after 10 passages the K. pneumoniae strain became resistant to the monomer but not the dimer. The major microbiological difference between A3-APO and Chex1-Arg20 is the improved membrane-disintegrating ability of the dimeric prodrug. Thus, in agreement with earlier studies, the induced resistance likely resides in some membrane component rather than the intracellular target protein DnaK. In support, no genetic alteration in the DnaK multihelical lid region could be observed in any of the sensitive or resistant bacterial strains.     

Carbohydrate metabolism in the bovine carotid artery contracted by the action of potassium chloride

The concentration of some end products and the activity of some enzymes participating in carbohydrates metabolism were examined in bovine carotid artery contracted by KCl. Oxygen consumption decreased significantly, anaerobic glycolysis and tissue lactic acid content increased during the KCl contraction. The hexosamines and the uronic acids producing ability of the KCl contracted artery were also higher. During contraction the SDH activity decreased in a smaller degree, cytochrome oxydase activity in a much more important degree. On the basis of our results we can conclude that the complete oxydation pathway of carbohydrates degradation, as mucopolysaccharides synthesis and degradation have an important part in the energy metabolism, but anaerobic glycolysis is the most important pathway to produce energy for the KCl contraction of vascular smooth muscle.     

Dormant Buds and Adventitious Root Formation by Vitis and Other Woody Plants

Viticulture has historically depended upon clonal propagation of winegrape, tablegrape, and rootstock cultivars. Dependence on clonal propagation is perpetuated by consumer preference, legal regulations, a reproductive biology that is incompatible with sustaining genetic lines, and the fact that grapevine breeding is a slow process. Adventitious root formation is a key component to successful clonal propagation. In spite of this fact, grapevine has not been a centerpiece for adventitious root research. Dormant woody canes represent complex assemblages of tissues and organs. Factors that further contribute to such complexity include levels of endogenous plant growth regulators, the extent and duration of dormancy, carbohydrate storage, transport, the presence or absence of dormant buds or emergent shoots, and preconditioning treatments. For the above reasons, the mechanisms driving adventitious root formation by grapevine and other woody cuttings are poorly understood. We present results indicating that the dormant bud on cane cuttings from a non-recalcitrant to root Vitis vinifera cultivar, cv. Cabernet Sauvignon, slows or inhibits adventitious root emergence. In contrast to Cabernet Sauvignon, removal of the dormant bud from cane cuttings of a recalcitrant to root hybrid rootstock (V. berlandieri × V. riparia cv. 420A) and an intermediate to root hybrid rootstock (V. riparia × V. rupestris cv. 101-14) had no influence on adventitious root emergence. Reciprocal transplanting of nodes containing dormant buds among all three cultivars did not affect rooting behavior. Our results indicate that the commonly held belief that bud removal diminishes adventitious root emergence is not true.     

Mode of action of photosynthesis inhibiting 4-hydroxy-benzonitriles containing nitro group

The effects of 3,5-disubstituted 4-hydroxy-benzonitriles — bromoxynil and compounds containing nitro group — on some photosynthetic parameters of spinach and wheat were investigated. There is considerable difference in the effectivity of the compounds even at the level of chloroplasts. On the basis of their effect on the development of CO₂ fixation of greening wheat seedlings bromoxynil and 3,5-dinitro-4-hydroxy-derivative were ineffective, while the asymmetric — 3-nitro-5-halogenic-substituted — compounds showed a strong effectivity. The bromine and iodine containing asymmetric compounds reduced the intensity of the short wavelength fluorescence. All asymmetric compounds shifted the long wavelength fluorescence maximum with 5–8 nm to shorter wavelength. These results refer to inhibition of formation of chlorophyll forms absorbing at longer wavelengths and to the change in the conditions of energy migration. The ultrastructure of the chloroplasts in the treated seedlings became similar to the shade adapted chloroplasts.