Flavonoids enantiomer distribution in different parts of goldenrod (Solidago virgaurea L.), lucerne (Medicago sativa L.) and phacelia (Phacelia tanacetifolia Benth.)

Plant material is a rich source of valuable compounds such as flavanones. Their different forms influence bioavailability and biological activity, causing problems with the selection of plant material for specific purposes. The purpose of this research was to determine selected flavanone (eriodictyol, naringenin, liquiritigenin, and hesperetin) enantiomer contents in free form and bonded to glycosides by an RP‐UHPLC‐ESI‐MS/MS method. Different parts (stems, leaves, and flowers) of goldenrod (Solidago virgaurea L.), lucerne (Medicago sativa L.), and phacelia (Phacelia tanacetifolia Benth.) were used. The highest content of eriodictyol was found in goldenrod flowers (13.1 μg/g), where it occurred mainly as the (S)‐enantiomer, and the greatest proportion of the total amount was bonded to glycosides. The richest source of naringenin was found to be lucerne leaves (4.7 μg/g), where it was mainly bonded to glycosides and with the (S)‐enantiomer as the dominant form. Liquiritigenin was determined only in lucerne, where the flowers contained the highest amount (1.2 μg/g), with the (R)‐enantiomer as dominant aglycone form and the (S)‐enantiomer as the dominant glycosylated form. The highest hesperetin content was determined in phacelia leaves (0.38 μg/g), where it was present in the form of a glycoside and only as the (S)‐enantiomer. A comparison of the different analyte forms occurring in different plant parts was performed for the first time.     

Purification and immunological studies of glutathione reductase from rat liver. Evidence for an antigenic determinant at the nucleotide-binding domain of the enzyme

Glutathione reductase has been purified to homogeneity by a method which is an improvement of an earlier procedure (Carlberg, I. and Mannervik, B. (1975) J. Biol. Chem. 250, 5475-5480). The new steps in the purification scheme include affinity chromatography on 2',5' ADP-Sepharose 4B. Antibodies to glutathione reductase from rat liver were raised in rabbits and used for analysis of the enzyme by quantitative 'rocket' immunoelectrophoresis. Glutathione reductase from human erythrocytes, porcine erythrocytes, and calf-liver gave precipitin lines showing partial identity with the rat liver enzyme in Ouchterlony double diffusion experiments. Enzyme from spinach, yeast (Saccharomyces cerevisiae), and the photosynthetic bacterium Rhodospirillum rubrum did not give precipitates with the antibodies to the enzyme from rat liver. Titration of glutathione reductase from the different sources with antibodies confirmed the cross-reactivity of the mammalian enzymes; the human enzyme giving the strongest heterologous reaction. No reaction was observed with the enzyme from spinach, yeast, and Rhodospirillum rubrum. NADPH, NADP+, and 2',5' ADP were found to inhibit the interaction between antibodies and glutathione reductase from rat liver and human erythrocytes. NADH, glutathione, or glutathione disulfide did not protect the enzyme from reacting with the antibodies. It is concluded that glutathione reductase has an antigenic binding site for the antibodies at the pyridine nucleotide-binding site of the enzyme molecule.     

Ethylene and IAA interactions in the inhibition of photoperiodic flower induction of <Emphasis Type="Italic">Pharbitis nil</Emphasis>

It has been shown that both IAA and ethylene application inhibit flower induction in the short-day plant Pharbitis nil. However application of IAA has elevated ethylene production in this plant, as well. Strong enhancement of ethylene production is also correlated with the night-break effect, which completely inhibits flowering. In order to determine what the role of IAA and ethylene is in the photoperiodic flower induction in Pharbitis nil, we measured changes in their levels during inductive and non-inductive photoperiods, and the effects of ethylene biosynthesis and action inhibitors on inhibition of flowering by IAA. Our results have shown that the inhibitory effect of IAA on Pharbitis nil flowering is not physiological but is connected with its effect on ethylene biosynthesis.     

Fluorescence resonance energy transfer analysis of the structure of the four-way DNA junction.

We have carried out fluorescence resonance energy transfer (FRET) measurements on four-way DNA junctions in order to analyze the global structure and its dependence on the concentration of several types of ions. A knowledge of the structure and its sensitivity to the solution environment is important for a full understanding of recombination events in DNA. The stereochemical arrangement of the four DNA helices that make up the four-way junction was established by a global comparison of the efficiency of FRET between donor and acceptor molecules attached pairwise in all possible permutations to the 5' termini of the duplex arms of the four-way structure. The conclusions are based upon a comparison between a series of many identical DNA molecules which have been labeled on different positions, rather than a determination of a few absolute distances. Details of the FRET analysis are presented; features of the analysis with particular relevance to DNA structures are emphasized. Three methods were employed to determine the efficiency of FRET: (1) enhancement of the acceptor fluorescence, (2) decrease of the donor quantum yield, and (3) shortening of the donor fluorescence lifetime. The FRET results indicate that the arms of the four-way junction are arranged in an antiparallel stacked X-structure when salt is added to the solution. The ion-related conformational change upon addition of salt to a solution originally at low ionic strength progresses in a continuous noncooperative manner as the ionic strength of the solution increases. The mode of ion interaction at the strand exchange site of the junction is discussed.     

Nerve Growth Factor Effect on Adenosine Transport in Cultured Chromaffin Cells

Chromaffin cells both recently isolated or in culture present a high-affinity adenosine transporter with a Km value of 1 microM. When cells were exposed to nerve growth factor (NGF; 10 ng/ml), the adenosine transporter affinity decreased to 3 microM. This value was maintained from 3 days after plating to the end of the culture period. A change in the transport capacity was observed, with a significant increase (approximately 200-260%) in NGF-cultured cells throughout the period studied.